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ri
DIE NEUNATJGEN
(Petromyzonidae)
by Professor Dr. Gunther Sterba
1962,
(En.glish Translation) DIE NEUNAUGEN
(Petromyzonidae)
by
Professor De. Gunther Sterba
1962
(English translation)
handbuch der Dinnenfischerei Mit teleuropas Band III - Lieferung 10 (Schuss des Bandes)
• TABLE OF CONTENTS A. iN-en0ri=z5 0-q
I. Ta..:Donoray and Distribution of the Petromyzontida 1
11. Description of the Central European Species of the
Subfamily Petromyzoninao 5
D. ANATU::U An PUYSIOLCed OF LAKPaEYS 10 . . Y. Inteument 10
Derivatives pe the Integument - IS 10 III. Mechanical Structures of Lampreys
The Skeleton 19
The Musculature 25
IV. The Nervous System 31
nrain and Associated Glands 31
The Nerve Cord 37
The Peri»heral Nervous System 38 . . V. Sense Organs of the Head 40
The Onan of Olfactio-1 40
'Mo Eyes 42
The Labyrinth 43 44 VI. The Vascular System
The Heart and Arterial System 44
The Blood Sinuses and the Venous ystem 43
The Blood 47
VIII. The 2oregut of Lampreys Outside of the coolum 42
The Larval Mouth and Pharyn-î: 4G
The Adult Mouth and Pharynx 42 • The Branchial Pharynx of Larva and Adult 51 Organs of the Body Cavity 61
The Organs of Excretion of Lampreys 04
The Gonads 66
Hormone Systemof Lampreys ou
eS• Miscellaneous 71
Chromosome Number end Hybridization 71
Nooteny 71
.Capabilities of Regeneration 72
Parasitic Fauna of Lampreys 72
C. ONTOGENY, DIOWee, AND OECOLOGV OF TME LAMPUYS ...... 73
I. Primitive and Embryological Development 74
U. The Larval Period 70
III. Metamorphosis 84
vV. Catadromous Migration 83
V. The Parasitic Seeding N.Iriod sa
VI. Spin g Migration 91
VII. Spawning Period 99
'Conditions Which Must it for Mating 100
Courtship and Nest Building 101 .
Mating and the Spawning Act 103
Free Laying or Copulation 106
' VIII. Post-spawning 100 LAMPEY rIsHERïss
2. rising Grounds and Catch in Central and Eastern Europe . 110
U. Fishing Sonson e Equipment and Methods 115
1 17 1. Value of lamprey 120 . T Preprstion of Lamprey 124 • 111. V. The Ueputed 7exicity of Lampreys 126 •
VI. Lampreys ns Fish Pnrasites 127
Damages to Fish Caused by Lampetra
in the Dnitie Sea 127
The Damage Done by Potromyzen. _marinus (Land-locked in the
Great Lakes of Woeth Pmerica 129
E. MASONS FOP, ME DECLTM, 0? LAMPREY POPULAI1MS IN CENTRAL rouop2 121
„ F. AMCIAL PROPAGAWON AND UEMZIWU OF LAMPUEYE; 134
G. HISÎCUY or TME STUDY or umpfuys AND 1I oalelw OF Warin NAMES. • 136 •
• •
Die Neunaugen (Potromyzonidae)
by • Protessor Dr. Gunther Sterba
1962
PrelïminAry
English Traneaation aovised Deaft • lefflproys are wodorn, ool-shaped cyolostomes which leave the brackish p.263 . or sea ,,;ater in which they live to ascend ivers in search or spawning groundr5. After s'pauning the adults die. Tho larvae, knoun as airenoeoctes, ,end suerai yos in freshwater but, unlike the adults, are filter feeders - rd live burroliod in the bottom or the stream. After metamorphosis the young a.Uults ndgrato to the sea where thoy prey upon fish by r•sping a
hole in Lho flesh by means of a tooth-studded tonGue. While eating into the ish tfloy suck the blood of their victim. Several species have adapted
empletoly to freshwater. In many of these the life cycle is shortened by elimination of the parasitic period with sexual maturity being attained shortly after metamorphosis. The energy requirements of those species are supplier.1 by food reserves ‘z..ccumulatod during the :Larval stage.
Lampreys are only of local Imporl„ance. In the .Atropean .Lisnlng ln-
dus;,ry, however, because of =4.erous primitive characLoristies, they are
objects of intensive study. Th.e modern membors of the Potremvzontidn recapitulato in their life cycles one of the most interesting phases in the evolution of vertebrates. They present, therefore, rare opportunities in the
analysis of physiological causes of phylogenetic processes.
. 0 Ta...-:onomy and Distribution of the Potromyzontida
In the Cyclostomata (literally "round-mouthed creatures') a class of
the Agnatha, (literally njawless creatures"), are the following subclasses
Authev-'s footaote I would like to thank Dr. Christian Schoenfeld of •ho Ca-rl 2:e:iss Company at this time for the preparation of the drawings 2, 5, 4, 5, 7, a, 71),„ 16 2 17, 18, 21, 28, and 37. I would like to further thank Pisheries Supervisor Lift of Wordermuchle and his colleagues for elaking avaiMble material on lampreys. • :sraper ordors: (Stensto, 1958)
Class Cyclostemi 1. Subclass Cephalaspidomorphi Suporordor Osteostraci Superordor Anaspida • Suporordor Potromyzontida 2. Subclass Pteraspidomorphi Superorder « atorostraci 5Uperorder Kyxinoidea 1,
..)Q 3ubolass eJ..holodonti Superorder alebolepida Suporerder Theledontida
nlo period over mhich this interesting class formed an im-eortant ole-
;lent of the morld's fauna extends from the Upper Silurian to the Loor
voian iipst species beceme extinct in the Upper Devonian period. Only
sriaU groups can b~ likely rocognizod in the fossil records following
this period. raleir present day representatives have been included in the
ibtr=y2,ontida and the Mysinoidoa. Unfortunatoly the phyloenotic develop- p.264
n,ant of these two groups is practically unknown, since they developed early
: cArtilaginous skeleon which greatly reduced the possibility of their
dotection by fossil remains. Stonsio studied the anatomy of Silurian and
evonian cyclostomes in surprising detail. Compared anatomicallyith'these
encleAt.cyelostomes the modern Potromyzontida are found to have retained
so.ei primitive characteristics. Fortunately in those comparisons specialized
cheteristies can be clearly distinguished from primitive.
"1-3.1e Potroontida (lampreys) are distinguished from the 'ywinoidea
(Iner) by thoie indirect development. The larval phase of the lamproyE:
pc:Inns the comparisons mentioned above and suggests the physiological . • requirements for the transition from the original filter feeding of the natha to a predatory way of life. The life cycle of the Petromyzontida wesents an opertunity to study those phases which have played an important
,ole in the development of the chordates. Further diagnostic features
sorving to separate the two superordors are the tooth-studdede fannel-like rmuth, the blind olfactory sac, the lack of barbels and especially the woll
developed oyes of the adult lampreys. All modern Potremzontida are included in the family Potremyzenidae which are identified by the sane characteristics
possessed by the suporordor. According to holly (1933) the family may bo
subdivided into two sub.families on the basis of the following characteristics:
Supraoral teeth only on one horny plate: the periphery of the oral
disc) frlecfed .cith lobes and cirri ,,,,,,, ...... A. k3ubfa:Uly Petroonino
Suprteral teoth distributed on two horny plates: the periphery of the
oral disc not fringod with lobes but with eirri.B. Subfamily ;gordacAic
Figure 1
ilorld distribution of the retremyzonidao (after Grasse) •
Ail 'European lampreys belong to the subfamily 2otronyzoninac which
includes 7 genera and about 25 species. The Petroutyzonidae are distributed in the tc4perz.to watorn of the northern and southern he:Aispheros (Fig. 1). iierg (1951) baliovos that this distribution first came about durinu times of • .• • world flooding. U0 assumes that the lampreys were pushed north and south
out of a limited region in the northern hemisphore during the ice Age. 'I'ho • southern groups penetrated the tropical zone and entered the southorn
izu in.nu:ncod by '',.;emllszr,:ztu3,:a ›
stenothcr.l.
c..1:ton td 1 "pmirecd"
''pateed *cl" app:U*à twv wh5,ch inhAît
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tYP1'=1 oxr,.nPle ckg :nich e aro tb* tho beook (Zempic ..ea The.2 leev=
of t.4c£. spool‹.1* wep f!:/ukif diet ..tzeuleihabl 12-.t.c.acel(elly but tb,.e ri.vQe 1wwpzey ml.gen.to tep., zon afVcr rie..ltee?.wee>stli and 1 -4vo fcr
on ez.eh. paratic phab,z.
t: ioo• .1e..:itp7e,:ey àes loet. Uth e,,.:Dtamoephoele, becw5k
ccc.(2.;.* tt:› the 130u, raaurz;..
YcLIng em4 2-,unreileca peop‹.:kee that th*e* rcL U:eir liDeZeezw.(.1, 1.i.gQ dj...;wIay ereel .iacozciny. I I Açiu-,.);:g sto Z- In.derJe, ;;;;I:7) aio S;.:ollovile. pn1red zee.ileics .ze ,:.::ou,e
Non-roa:easitic Ilubitat e?:.emz
Z. oniD.Lii. Cree metbern MitTiss:&.1.Yen ba.4îin c,":>.nznr_uLv,3 Wcetan, rog.1:7en ce th
1. e- CCO. rft Z.D.torn eyg tUt - 1.
L. eblviatill ;4..4 • le anid eiout•en europo (AtZv.nL€c nn:à ez.c ,Mter=neau teÂbutaelOG oxept aria 51nek Z. 4 Aeth *1-eQpz. e,nd ;1ne Pe-clfic
dce;,erdi e. diulCced.'?„ ,Duneo -5-
II. Description of the Central European Species of the Subfamily Petromyzoninao
Key- to the n:legos- oe the Contrai rt.;urcecan_lP.mproys . (,,see 11
1. Supmeral plate narrow, bearing two largo, pointed, horny teeth closely sot together. Outer labial teeth (Fig. 2) nulerous in an arch Flal. nus . ; Supraoral Dlate broad and in the form of an arch with a terminal
tooth on each side. (Fig. 5) 044,70046090e140‘4:009*4000949ed1U04e9 2 p.266
2 4 Outer lateral teeth /ackin .49 9 ..4,80.490889.90898 4 994.4 48 e 8 84 8 43 Outer lateral teeth prosont...pnomwpn.dulforg4 'Aegan 2adontolween danfoli vidykovi, 1.anandrea
3. Sexuallymature animals about as thick as a thumb.... Lnyoleti:a fluviatUis L. Scremally mature animals about as thick as a nencil...Lamootra plaeri (Dloch)
Larval and adult lampreys may be casily distinguished by the following
characteristics:
outh swerounded by a velum vithout horny tooth; no visible eyos. The med_an dorsal fin is uniformly wide and. extonde continuously into a caudal fin...... Larva, Ammocoete ftWerdea Sucking Imuth with horny teoth; -wide largo oyes with shining silvery iris. Two 1-(:ore or less separated dorsal fins
4 44o841 8 8 4 4 84898888 4 :48 4 48048944.1,9844448IMaeg Lampotre„ 'JMounaug
Figure 2
Diagram or the dentition of lalupreys. (after Holly, from Grasse)
It ,n;- very difficult to identify uith certainty the larvae of the various species of lamDroys. All methods up to the present have been shown to be
wreliable fecontly Zanandrea (1959a) has draen attention to the histologi-
cal determination of the number of oocytes as me of separating species
since this nielor appears to characteristiq for each species. -6-
11› Po[,romwen yne,rinus Llnne 1258_1Firfs. 1_4.1
Comrmn names: German: .1'*3orneunauij,e, i'",eorpricke. Seclamproto Nounaup;enkeenig, Grosses ïlounauze Danish: Havnoï..:onoejn 1,:hg15sh: Sea intnproy nnnish: ;.îerinahkaainen Fr OM h : Laviproie *C.).11C3 Dutch: ‹!.eopr'keck Italian: ki,ufulloto, La.mpreda 'ebrwegian: Uoviamprot Swedish: Pavsnejo-noec;at •
Figure 3 Sexually mature sea laeiprey Petrom7zon marinus marinus
Flipre 4 Tho Mental arnamentn of P.,narinus parinus (after Rauther and Zan'andrea coeined)
trj Anadromous species living in the ocean. Body eel-like,
up to 990 ITLA. in length and 1200 gm. In -oeight. Dentition very pronounced. p.267
Supracral plate with tee large tooth closely set together. Infraoral
plate wih 7 - 9 teeth the muer labial plates (four on each side) with 1:::70 tooth each. Utaerous pointed outer labial tooth. Tho anterior dental plate of the hezld of the tongue is drawn in at the raiddle and boars tuo rows of curvod sieall teeth. Posterior portion of the split dorsal fin continuous
with the caudal rin Sovonty myomoros on the average botgeon the last gill pouch .2,1-1çl the vont.
Da-A,ng the spam-nin;;; migration the adults are golden broun to black dor- sally and laterally more or loss dark brown spattered with dark arons.
Ventrally thoy are light in colour. Frequently in the ocean they are uni- • foraly brown laterally. -7-
111PieributiwTo Atlantic coastal waters froel the White Sea and Iceland to Gibraltar. Weorn and mliddie Baltic Sa and the north and south coasts of the Neditorranean Soa including Italy. Le.okink3 in the Danube drainage. The Atlantic coast of North Auorica as far souLh as Florida, Vertical dis- tlbution 5 - 500 m.
'210 species ascends rivers after leaving the above-montioned areas
during the pre-spavalin polded. In Europe this takes place between j'ay and July. In the ihine thoy swim as far up as Basel, and in the dlbe aa far as nohemia. :the o'Kact locations of the spawning bode aro unknown but it is
presumed thai, P. =rinus 0 like the other species, lays its eggs' in the gravel redds of the river. Tho number of eggs produced is about 200,000 -
250,000 and these are about a millimetre in diameter boing yolicuish in ap.-)earance. The durntion of larval life is uncertain and is presumably
years. Very few observations have been made on the catadromous migra-
tion and the predaceous elstonce of this species in the ocean.
The larvae are filter feeders but the adults are Carnivores. 'iloy
uttach themselves on fish by suction and rasp a hole in the musculature uith
the. hole of their tooth-studded tongue. Blood and a %rein of flesh and body juicos are sucked out of the fishes body. Cod are especially attacked but wounds have also been observed on sharks and uheles. Lampreys in the ocean cannot be fished with profit since they are onlycaught individually. The land-loci:ed form of Potrime mp,rinue has transferred ite life cycle in historie times ontiroly to frechwator. In the Great Lakes of North kecrica it is a dreaded parasite. Here it attains the length of 550 mm. • Cœn-cion names: Co.eman: Flussneunauso, Peicke, Nounauge, eorpol Flodnegenoejn River lamproy rinnish: Virtahslklainen Feenchr Laf4proie fluviatile t)utch: Lamprei Italian: Lalupodra i!:orLzslan: In.ed lampet Mineg sslan: Unoga Cvodish: Xejonoegat Spnnich: Lamprea de rio Czech: Plhalico iiungarlan: Felyami orea Orschal
Figure 5 Diagram of the "oral armament" of —Ln=etra — fluviatis (after Zanandrea)
.),«As2'h,plen:1 An anadroalous marine species, Dody ool-like usually p.263 300 - 400 milnaetres in length and 90 - 130 gi . in weight, rarely oxcooding 450 mr.I. Sup-eaoral plate in the form of an arch with a pronounced tooth on each side. Infraoral plate uith 5-7-9 teeth of approximately the same size. •cas3x.wtally the tde outer toeth are bicuspid. Three., boar teeth, inner
dental platee on bo-th sides of which the upper 2, the middle 3 (4) and the lowor 2. Outer labial teeth only abovo the supraoral plate. A closed ring or po:,..1 ,-)hcr:11 labial teeth. In the reu of teeth of the anterior dental plate of the head of the tongue are 9 - 13 - 15 . 19 small tooth of which
the niddlo is always unusually largo. The tooth are pointed during the pre- datory phase but beco.ue blunted during the spawning migration. (Is thore a reDlace_:iertt e t3Oth?) EIV;CDt during the spawning poriod, the two dorsal fins remain undivided. During the spawning period they fuse. 13etween the last gill r;onch and the vent are 59 - 63 - 67 nyomeres.
The larvae are a clash to a dirty yellow and more or loss darkly mottled e.Che • adults leaden grey, dark or greenish blue dorsally. Laterally leighter and often a delicate dirty yollug in contact with the silvery
ventral sido sins durinj, the spawning pelod often with a lilae-coloured lustre. Eyec are large with a broad, silvery iris.
25Mr:Ibupn Atlantic coastal uators of &trope with the exception of
the Iberian poninsuIa. Baltic sea especially in the Gulf of nothnia. North- ern coast or the western Mediterranean; in Italy only in the LIEurian and
Tyrranean SGaS and not in the Adriatic. This snecios is not presont in the drainage system of the Danube, the Black Sea and the northern Polar Seas.
The river lamprey ascends rivers just prior to the spawning period and
. lays its eus in the upper reaches of the brooks inhabited by p;aue.,),. trp.tta and Thy.1. tpuAllug. In central Europe the return of the lalnorey from the sea,beins usually in summer and ceases often in March of the following ear. SpLwning reriod from April to Juno. A female produces 25,000 - :30,000
eggs. (ace p, bri )„
The larvae called amecootes, are filter feeders and barrow in the
soft bottoa of the streaz each that only tho rrionth ha s any connection uith the uator. They Drefor thoso reachos of tho brook uhore there is sandy,
ooze. Tho larval poriod lasts 3 - 4 yearz. The newly transformed adults migrate to brackish sea water to feed upon fi$h flesh and blood. They attach theseives prineipally„ by suction on bottemliving fish and rasp doop holes in the maç;oulkLure with theeir tooth-studded tongue. Growth during this .,riod is extraordinarily rapid. After from one to two years,
foodin,;, irroversibly ceases and tho lampreys return to the spawatng areas.
After spawninf; the aninals die. Aftor the cessation or feeding, all lifo enctiona are provided with energy from food resorvos of the body. -10- gp Lap.lpreys are caught commercially in the e=the of the Maas river and tributaries of the gulfs of Finland and Bothnia. In Europe the value or this industry is about as ereat as that of the eel fishery.
Berg (1931) distinguishes Paiuotr:e. fbviatip_s irma twic,, from a
foca »retecax (L. S. Berg L. So '£org, 1931) Thie mInor race occurs only in freshwater and consists of smell individuals no longer than 27 cm> and
usually 12.5 - 25 cx. Tho ripe femalo produces in the average of 3300 eggs. Terra 1,..ypic:A. Rivers Warova, Okhta, Kavasch„ Svir, Vidlitza, eeva (estuary)
and Lake Ladoga. In La2,zoU',•doga, especially in the vicinity of the estuaries of the Svir and Udlitza rivers a dark variation of this race occurs. L. sby.
nraeom. aber_relp L. 5, fierg (1931. Abalcumow (1956). however, spates the validity of the form praeco,
-r -t1 a 33-_t_oen•, it,y) -• 0 • • •, Corceion nueace: Geran: kleine Prick() iish F4rook In;(9roy French: _Petite 1aea;9reie de rivierc Italian: Lanpedra Dutch: Deekprik p.269
Figure 6 *1,0v0 beore .• larve. laotamorphosU.„ below': adult before the spaning period
Figure 7 Diagram of thc oral weaponry o£ For terras refer to Fig* 5. (after Zanandroa).,
Dop 4: Non-parasitic, Son-migratory, freshwater fore. The body
u;) to 180 mm.. zostly between 13 - 15 cm. Dentition corresponds to blunt toeth are that of Lapetra ± however with -ciletamorphois to othor character- layed dow There are *lose similarities ulth rospoot shape and arrangenent of the isLles to L Tho difforeneo in the cowpared fins d000riboa by Lho, early authors aro in error because they eolelF,rabIe stages roprosentativos of different phases of development. In The larvae of the tao the sha.po and distibution of the fins are sinillar. dovolop..mont species may only bo distinguished by the nambor and stage of
of the opoytos. (2;anandrea. 1959b) between the adults. acuover„ there are earked bieloecal difforencos and the anadro- In L„. planer:1. the ca, tadromaas migration, tho parasitic phase motlmorphosis reeding noas migration are lacktm?. '41th the beginning of
; irreversibly ceases. In spite of this eortain provisions for a parasitic however, Indicate a life or durinc eetae.orphosis. Two charactoristice, 1) 1.here arises, • morphologioal ad2,-ptation to a non-prasitio adult life. uhieh in I.. flpwiAIM% only as montionea above, a dwtolopluent of blunt tooth s; occurs daring tho catadroluou$ migration. 2) The extondcla oe.20Phague
dovoloving during metamorphosis is closod ore. Auzust - ,:;opte,viber, as Motaorphe;.sic ubich taos place in the period furnished with owrgy £rou stored all the othor following vital procosso:;, ie April - Juno or body reserves, The spawning period occurs in the months. perish. Stol-ba (1955) p.270 the follouing year and after spanning the animais spauning period. The mat- observed a rodueed tendency to migrate before the metamorphosis. The nuMbor of ueation of the gonads already begins durirg being somewhat eggs produced is 600 - 1500 the siu) of an indiVidual ogg
larer than that of I, flu-sdatUls, -12-
• The larvae are clay coloured to a yellowish eey and more or loos r.:,ottled. In the adults the silver whito ventral side fores quite a con- tract to the eirk brown to blue grey dorsal surface. Eyes large with a broad, silvery iris.
4.1=linotr el:vre,,rt is eympatrie with 1r,eoolra fluviati1io and Potro;nyzen.
D•strihution: Western and Central L'urope in brooks and the upper reachos of the rivers, as far south as southern Italy. Isolated in the drainage system of the Danube above Linz. (Fig. 9). Absent in the 13alkans. Of no conmerci:-11 importance.
, n, In 911 '
.Common name: Danube lamprey.
Pi_ b 8 Uagram of the dentition of Eaden4eAre,en 4nfordi for tares refer to Fig. 2 (after Zanandrea)
r5„Dt,: A parasitic species without catadromouo and anadromous migrations. Dody oel-like and up to 250 ima. in lonst4 and 19 ge. in 1104;ht,J
The supraoral dental plate in the fore of an arch, broad and possessing
tereinal teeth ubleh are sometimes bicuspid. In2raoral plate uith 9 - 10 - 13 teeth. On .each side three 'inner labial dental plates of which the anterior,
the middle two and the posterior three bear teeth. A compleJte row of outer labial teeth run between the two posterior labial dental plates belovi the infraoral -.plate. Anterior, lateral and lower outer labial teeth are present. • The anterior lingual dental plate with 11 - 15 tooth. The middle tooth -13-
, onlargo(. 53 - myomeres 'between the posterior gill pouch and the vont.
The two dorsal fins encept for the spawning period, arc divided. Tho
ammoccotos are coloured markedly brown.
According to Zanandrea ( ) 59a) Eudontomyzen darfordi is distributed in
Roumania and in the Teresowca and Toroblanca river. oe Csachoslevakia
(pi. 9). The Danube lamprey of Austria (Danube and Raab) and Jugoslavia
al.d certain '.-›.arts of Czechoslovakia represent a distinct sub-species--
L'ndcntomvsandanfordi vladyl 1959) but there are distinct variations in behaviour.'Msoe .table PA "Zruz.iGntomyon danfordi viadykovi does not feed after metamorphosis and p.271 consequently remnins small and matures sexually sooner. The teeth however, in this non-parasitic form generally are sharp. • Figure 9 Distribution of lampreys in tho Danube (after Zanandrea) bceez.1 demonstrated that this species may be paired off with E. danfordi since it is non-parasitic but similar to the parasitic species morphologically. It becomes sexually m2ture and draws upain reserves pre- pared in advance. Tam:yemic characteristics of Eudontemyzen danfordi an Eudentemyzon danfordi vladykovi according to Zanandrea (1:350c) are: z • -14- • i; vor iil phases: • 59-65 59-G5 1 • Dorsal myomeres Roumania, Czechoslav- ustria, Jugoslav- . 2. Distribution , akia, in the Terescova la at Luken/ and and Teroblancal rivers. Cilistova in Czech- oslovakia. (13ratislava) 'or the adults: . 1. Outer labial dentition complete complete 2. Peripheral dentition , lacking • il,›cleill-,. 3,. Teeth on supraoral plate 2 2-3 4. Upper outside labial tooth 9-10-13 5-7-12 5. Teet'r..on infraoral plate 8 rows . 5-8 rows 6. Lowe r outer labial tooth . 4 rows 3-4 rows 7. }.Ïigrati.on frlllowing metamorphosis none none 8. reedIng after meta- . morphosis : present' lacking 9. Durntion of life after metamorphosis. (in months) 17-9 6-8 Colouration in ammocoetes Dranounced pronounced In addition to the species which have teen described above ln detail, the following lampreys also occur in Europe. 'f.amstra zc,nandrea Vladykov 1955. A non-parasitio form found in Northern Ztaly. Distributed in the plain of the River Po, Allepatric with Lampotra fluvistilis and L. planeri. Simi- lar biologically apparently :e5._ai;e:==) to L. planer'. Up to 1;.)0 mm. This ariecies shows a strilzing similarity to Lampetra cepyptera (Abott 1361) of the Ohio and Potomac 'basins. (Zanandrea 193o, 1957, 1958a) 'Figure 10 Distribution of the Petromyzonidae Ln Eurasia (grûm Lanzing red.rawn and âltered) • Eudoatomon arie L. A. qerp- 1$31. A non-parasitic £reshwater form whose centre of distribution extends from PruÙ1 to the Don and Yle)an. Aout 134 - 20t". in length. As 1,Zannndrca was p.272 able to doonstrate the species IS pushing south westerly and occurs today, for example in Sarajevo, Jugoslavia. 1 Caspiomyzen wagneri (Z. Kessler 1S70) Parasitic species living in the Caspian Sea and ascending the drainage system of tl:s Volga. 370 - 410 mm. A precocious form (L. S. Berg, 1 )31) is said to romain much. smaller. 1,2mpetra japonica soptentrionalis L. A. norg. 1 ,331 A pnrasitic, marine, anadromous subspecies whose range extends froffl. the White Sea to the river Ob. Up to 430 mm. in len&th. The relation to the . gI1, form Iar,pc,, tra japonica occurring in Eastern Siberia and Alaska, is established through the non-parasitic form Lapetra japonica hessieri (Anikin 1905). (fig.10) u,a, B. ANATOMY AM PHYSIOLOGY OP LAMPKEYS The anatomical and physiological features of lamnreys correspond in part to those of the Onathostomes but also depart markedly in some respects. Tho common characteristics of both groups usually permit fruitful specula- tion on the origin, construction and function in organs of the chordates, and the divergent Characteristics nermit meaningful'comparisons of cor- responding theories. Wot all similarities, however, are due to a common phylogcnonotic origin, but some organisms have undergone deve/opment in- dependent of each other. This is especially true for psysiological char- • actors. On the other hand, not all differences ArOlïr the higher vertebrates should bz,, considered specializations peculiar to lampreys since some represent the precursors of those present in the higher forms. The prob- ability is groat in the lampreys that these peculiarities see older primi- tive characters which have been retained. Y. _Yntegumont The integument in lampreys consists of epidermis, corium and subcorium and Is a typical vertebrate integument of the kind present in fish. The shin is smooth to the touch but not slimy. In the adults it ean be easily re- moved. Hard substances are found only in the mouth region. The colis of the in height from the inner layers outwards. The outermost epidermis decrease layors of cells produce a layer of epithelial cell e reminiscent of brush- bordered coils. Specialized epidermal cells are especially concentrated in the dorsal region in the form of granular and flash-like glandular cells. In the former are granular inclusions which later swell up to form a viscuous slime. -17- e socroted through the brush border. The latter cells are homogenous and have as a rule two more or loss centrally located nuclei and apparently remain always, or at least eor a long time, in connection with the outer layers. Their function has not been clearly demonstrated. Figure 11 Lampetra nlaneri ( 1-1.) Section through the dorsal epidermis of a 120 mm. long larva. Co, corium; E, epidermic; KoZ, granular cells; KoZ, flask colla; M, musculature. Maghificat&on, 1?1,0 times. The densely packod collau,nous fibres of the corium are mainly circu- p In young larvae the suncerium is very thin but becomes darker with increasing age by the local deposition of fat cells. Single elastic fibres of the subcorium penetrate the corium vertically. Numerous molano- 4 I›phores are found everywhere especially on the dorsal surface between the corium and the subcorium. On the ventral surface of the larvae are xanthophores and guanophoros. The latter celle decrease substantially in numbers with the beginning of metamorphosis. The pigment cells are con- trolled by the hypophysis. Tho epidermis and the corium form an transparent costing over the eyes. The ski of lampreys is unusually well provided with sensitive structures. p.274 (Pahrenhols, 193, Wirochi, 1959.) Besides these ln the head and branchial regions arranged as lateral line organs, free nerve endings, epidermal sense . organs, pressure sensitive organs, ridges of such organs around the teeth and eive types of free sensitive coils occur. Even the epithelium of the • pharynx contains sensitive structures and free sense cells in characteristic -13 - II,arrangements, Steven (1959) demonstrated that the photoreceptive cells of the epidermis of an ammocoete are sensitive to the visible spectrum in the region of 530 millimicrons and concluded that these cells contained a substance either similar to phorphyropsin or an identical photolabile ; substance. The photoreceptive impulses are collected by the lateral lino nerve, (Young 1935). • Investigations on the lüminesconce of the skin of the river lamprey were carried out by rlin and Sehaummowitsch (1956). Remanini (1957) determined the DNS content of the nuclei of various epidermal coils. According to Hardisty (1954 ) the permeability of the lamprey skin is very great. The ; skin of Lampotra japonica janenica contains a considerable amount of thiamin and vitam in- , 12 , (Iligashiu et al., 19U). In experiments in which lamprey were artificially wounded Orleva (1958) found that,the epidermis regenerated • elatively quickly but the corium relatively slowly. • • Eï. Derivatives of the . /ntegument The horny teeth of lampreys are purely epidermal formations in the region of the buccal funnel and the head of the tongue. Their number, form and arrangement are peculiar to the species and are consequently of geaat importance in systematics. The largo, strong teeth are underlain by cart- ilage but the small, in contrast, are only anchored to the epidermis. The "dental armament" of the lampreys (eig. 2) consists of a horny plate in t1-.e- shape of a half moon possessing incidental bicuspid tooth on both sides, situated on the upper rim of the rizeuth (supraoral plate with •denticuli ,u1)raerales). There is also a bent plate bearing 6 - 11 tooth C. •on the lower rim of the mouth (infrooral plate with denticuli infraerales). On both sides of the mouth opening are 3 - 9 inner labial dental plates each with 2 - 3 teeth (denticuli latoralis intorni). Aside from these dental plates upper, lateral and lower outer labial teeth can exist (denticuli /aterales c:e;:erni). Finally many species have a complete ring of peripheral tooth (denticuli marginales). The hand of the tongue bears, as a rule an unpaired anterior and a paired posterior dental plate. Al]. dental plates of the tongue possess saw like rove of teeth. Petromy2oh marinus has the moot pronounced.dental development of all EuroPean species. The teeth themselves consist of a horny cap intowhich a papi/Ia of thickened epidermis often is insertsd front below. As a rule • (by histological investigations) replacement teeth are found separated from the outer teeth by a thin cellular layer of the epidermis. (Fig. 12) In the I•kpil2a of the corium a cartilaginous center can bo found. Most species have plsosumably a continuous replacement of teeth. Lampetra fluviatiiis, on the other hand, according to Weissonberg, (1926) replaces its teeth only two timos and La=etra eancri develops a stump which corresponds to the second set of teeth of L. fluviatilis. . Proof of this romaine to be seem. My own investigations indicate that L. planeri oxhibits no change of teeth. Mechanical Structures of Lampreys The Skeleton The skeleton of the cyclostomes han been reduced during the history . of the subphylum. Modern lampreys possess, in addition ton chords dorsalis, only cartila-,4iaeus slœletal parts since substances are lacking cola- T;:e cartilaginous skeleton is reinforced in certain parts by -20- • connective tissue membranes. Surrounding the brain and the largo sense organs of the head is the eozooranium. The branch:Lai skeleton nos around the pharynx. The skeleton of the unpaired fins is weekly developed and porichordal skeletal elements have developed only as small, irregular bars. • The cartilaginous substance itself is not uniform throughout the skeleton. Yn addition to e hard substance corresponding to hyaline cartilage of the vertebrates, is a soft cartilage poor in intercellular matri. Many skeletal parts sro intermediate in respect to their com- > position of these tvo cartilaginous typos. Fundamental investigations of the skeleton of . lamproys have been carried out by Parker E1334), .Trotjakoff (:1D20, 102'), k>e -,;ertzoff (1)16), Marinelli (1930), and Johnois (1948). Figure 13 Lempotra planori CBI.) Cross - section through the chorde of a 152 mm. larva in the region of the third gill pouch. aChS, outer membine -of chordes; Ao, aorta descendons; . ChE, epithelium of chorda; che, tissue of chords; ChStr, cord of chorda; CV, vona cordlnans coudolis; ChS, inner membrane of chorda; xioo Clerda dersails: The cherda of lampreys is a rod, almost circular in cross-section beginning in the shapo of a ball immediately behind the Hypophysis in the region of the perachordana. It atteins ite greatest thickness in the liver region, tapers sharply, and trai/s out into the skeleton of the caudal fin. The body a the chordà is made up of turgid, vacuolated cells and is covered by a distinct epithelium, which is in • turn covered by coating consisting predominant/y of tough collagenous fibres - 21 - overlain by e thin e elastic coating. (Fig. 13) In adults a very delicate The elas ton iio ffu:ty be isolated end observed during dissection. ohorda in lampreys can ho readily removed from the body throughout its catira length. Leloup (152) detected a high iodine, content in the notochord of on the notochord Petrenen marinus marinue. Ilistological investigations out by Romanini (1953). of Latra. . pianeri_ have been en lad krocranium and the pieton , app2ratus: Tho disc-like, united pars- the brain e laterally chordalia Iie =der and over the chords at the base of as the to the anterior end of the chorda. They continue anteriorly e 1U3). On the lateral periphery of the para- -trabeculeu cranii (johnels according to lies the firmly closed ovoid labyrinth e which e Marinelli sad Stronger (1954), is united over the rhomboncephslon by the tectum synoticum (Figs. 14 e 15). Figure 14 Lamputra fluvlatilis Skeleton in thu head and branchial region. Tho left DieLOS eD:? paired structures aee only shown. erom Marinelli and Stronger. ftedrawn.) in In fully grown animals only the lateral wail of the brain capsule (cartila ge orbitalls). frOE4 of the capsule of the labyrinth is cartilaginous connective tissue. The roof of the skull, on the other band e is composed of The dish-Iike socket eyo is found IatoraI to the cartilegines orb. It is arched cartilaginous supported voutrally , and protected from DFCS'elre by an • ridge—the arcus subocularis (Figs. 14, 15). The brain capsule, towards the - 29 - -front is closed by a membrane of connective tissue on which the flask-like nasal capsule rosis. Figure 15 Lampetra fluvintilis (L.) Skull, dorsal and ventral views. • (redrawn from Marinelli and Stronger) Cartilaginous elements are connected mith the skull itself and these either extend forwards as plates or run vontrally as straight or arched cartilaginous rods. The first group represent an extension of the base of the skull which consists of tmo large cartilaginous plates. The more anterior plate is Overlazpod by the one behind like a shingle on a roof and rests upon the cartilaginous ring of the oral funnel, (Fig. 15) cart- of mhich a rod-shapod piece of cartilage arises posteriorad. The ilaginous rods of the second group fora arc-like structures jutting out in part ventro-leterally from the base of the skull or struts holding open, primarily, the vide lumen of the pharynx.' Cis'. 14) Of especial interest are the rods situated farthest back, i.e., the --arcus extra hyoideus and cartylago Elyrpformis. During metamorphosis the branchial skeleton unites with the right and loft extralvaline arch. The cornual plates unite uith the styler cartilages on which the importent voler cartilage is perched. Attempts to find hcmologieo of the axial skeleton of cyclostomes especially with skeletal elements of gnethostomes were made notably by end Tretgakoff (1920). However, rurbor (1 875 )p Sowertzofg (191G), 1 iichnels (1948) first' found satisfactory comparisons. Accordingly only the -23- capsules elements of the capsule such as the parschordalia, traboculae, the tectum cranii have of the labyrinth e the cartilage of the orbitis and the homologous counterparts. On the other hand the plate and arrow-like skeleton or the nericapsular parts arise either from the larval branchial promandibular origins. authochthon--not as Sewartzeff (1915) has essumod, from nains also questionable A suecial homology of the branchiogenic elements re the since those of the gnathostemes departing primarily functionally from corresponding cartilaginous elements have led to comparisons based eather on structure. the tongue and the pharynx, The complicated cartilaginous apparatus of a peculiar type .the so-called piston apparatus is also a formation of which arises from the floor of the larval mouth but is not comparable the with the hyoid bone of gnathostomos. The piston apparatus starts from which the long hyoid bone with a lateral curved out piece of cartilage on level of the second gill cleft piston cartilage extending ventrally to the is contiguous. Pt the level of the labyrinth sit the above mentioned qg Ef>4. corDual plates ror the function of the piston apparatus see page the piston The dc=ciDtion presented above of the =craniums and apparatus are applicable to grown animals. The .relations are essentially simpler in t'e.ce larva, Above all many extracapsular cartilaginous elements are lack:Ing. bronchiFfi s'exaeton: The branchial skeleton of lampreys consists a very coarse, larval of so-callcd soft cartilage and is in its entirety, , i like screen which is widely open anteriorly. The cartilaginous branchial i and seven longitudinal cartilaginous i 411, basket consists of nine paired transverse ,, , rods. The main • supports in this system are an unpairod straight in the ventral median line. In contrast to this all the other cartilaginous rode are wave-shaped and thus permit an elastic expansion of the branchial pharynx without articulation. .With the exception of the ventral rods there are short or long extensions. The first transverse cartilaginous rod cor- responds to the wide Arcus extrphyoideus mentioned above. The two last on tho left and right form caudally pericardial cartilage from the lest gill opening which also represonts ot the samo time e the disk /Ike deepened f/oor of the bv'anchial basket. The longitudinal elements are divided such that auart from the ventral rod in the median ventral line, there are cartilaginous rods on both sides ! Figures 1G, I'd, and 18 over cLud under the gill openings and two further which run close te the sheath of the chorda. These dorsal rods which connect the transverse rodz are proseht, according to Marinello and Strenger (1954), in Lampetra fluvintills„ only in the form of short pieces (Fig. 14). he skeleton. of _ the fins: The unpaired fins of lampreys are supported by densely arranged, unpaired, unjointed, cartilaginous rays which are comparable to the fin rays of enathostomes (Pitschimann o 1933> e («rig. 16). 'A segmental arrangement of the supporting elements is not observable perhaps with the exception of the most anterior. The cartilaginous rays are 1 inclined backwards and extend in the dorsal median septum up to the supra- 1 . neural, vesicular, gelatinous tissue. , ! 'ene Perichordal el.ements of the skeleton: In the Petromyzontidae but not I 10 i • in the Myninidae there are small pieces of hard carti/ago on both sidee of the spinal cord which are generally compsrable with the bases of the neural arches of the gnathostomes (Fig. 14). The many forked feet of these cartilaginous pieces surround, as a rule, spinal nerves. A union under or over the spinal cord or a growth around the chorda does not take place. One is inclined, in estimating the worth of . these functionless pieces of cartilage) to consider them as rudiments of formerly complete porichordal elements. Tho Musculature As in the gnathostomes the musculature of the cyclostomes may be p.273 divided into somatic and visceral muscles. Indeed with the cyclostomes the visceral musculature is covered in every place by somatic muscles. In is. the region of the back and tail segments the musculature is simply organ- ized end may be easily compared with the comparable musculature of the rPra,- hostomes. However, there are fundamental differences in the pharyngeal and head region, especially of adult animals. These differences result from the radically different method of feeding. Histological differences enist characteristically between the viscera/ and somatic musculature. Important 'work on the musculature of the lampreys has been carried out by euerbringar (1e75) and Tretjake2f (1U26). Somatic musculature: The somatic musculature of lampreys consists of units which are not divided by a septum transversal into cp2and hypaxone musculature 0 The muscles of the posterior part of the body are distinctly divided by myosepta and are bent forward ventrally and dorsally. En the middle portion of the body they aø olined slightly towards the head. Each muscle segment is secured to amisl connective tissue and extends posteriorad at a sharp angle as far as the subcutaneous connective tissuo. The individual segments may be compared to bags inserted in each other. E,ach myonere consists of numerous little muscle containers stacked one on top of the other (rigs. I7 e 45). • The continuous mantle of muscle is split en both sides in the pharyngeal rogfon by the gill clefts (Fig. 17). The opibranchial somatic musculature lying dorsal to theso interruptions extends from the upper side of the head to the antorior poriphery of the Posterior plate of cartilage (seo page ;?:1 ). 'In this manner the pines/ region . and the nasal capsule ara separated. Out of this ePibrenchisl muscuiaturo a small muscle., the m. - 1, corneol.is » among others » arises and is inserted in the outer cornea. '.1his muscle, when contracting decreases its curvature, i.e., It serves in ecoennedation eranz, 1932). The hypobranchial Somatic musculature is attached by moons of elements of somatic muscle notably -the right and loft P.2B0 ra, subocularin, to the annular cartilage of the oral funnel (Fig. 17). The contraction of this muscle on one side causes the head to tuen to the same 51d. The contraction of both sides causes the ventral nodding of the oral funnel. The wouk fin muscle opposite the fin rnys belong to the somatic muscles which are moot/y concerned with locomotion. 1,rsc.e-,-al musculature: lho visceral musculature, ineervated by the cranial nerves, is complicated from the standpoint of its topography and function. Sn addition it • larvae. The visceral muscula- siso occurs in different form in adults and and transfcreed during ture of the larvae for the most part, is reorganised duits arises almost, or motsuor•hosis. The visceral musculature of the a of relationship completely indonendeut of that of the larvae. This lac the la •val and adult severely limits the makini-Y; of comparisons between visceral musculature.. Furthermore, corresponding comparisons between hardly possible. On the other fully grown lambre7s and gaathostomes are hand this relation can be considered as further support for the theory that the gnathostowes in respect the cyclostomes have so profoundly departedfrom the two are no loger to the mo ,ie of feeding that the mechanical parts of comparaUe. own musculature composed of various arrange- eral funnel has i'L=.; directions. ments of musclos allowing movements of this sucking organ in all n. api Lis (.un. porfvcans (Fig. IV). This m. anmaaris is innervated by the •i the tri fluai ves. FuebrIn:.,.e) arising from the ?;.n?.nglion subopticum of but when sucl.:e.ing It When swimmin, the oral funnel' is narrowed to a slit the fish on its entire periphery. is c;n=,, viide 2.1ad DvossQd to the body of annular muscle arises during metamorphosis from the labial muscles of iie anterior are prominently the larva. '2he right and Ioet u. toctospinus involveà in the movement of the funnel. Figure 19 The head of the tongue of Lampatra _ fluvintilis, e. side vie'/ , b. top V?->DW* CO:2t. pi. Cartilse pistoria, Cart.• ouor.. _ -- --....—...... Cartilago supra apicalis with posterior lingual dental plate. • VZ anterior lingual dental plate. -28- • The musculature of the piston apparatus end the pharyngeal pump e the n. teigenus e 'is very complicated. V,oth systems can- innervated by not he separated on the basis of their function or morphology sinco many muscles of one are auxilliary muscles of the other. In all e twenty paired single muscles holong to this group. The pvotractors of the cartilage of the piston lie covered with somatic musculature. They arise chiefly from the middle portion of the cartilage of the piston end continue forwards to cartilaginous pieces in the vicinity of the mouth. =en the oval p.281 cartilaginous system is stationery the musculature brings the cartilage Of the piston forwards. Vhen the cartilage of the piston is stationary, the muscles suprJort the bending of the mouth ventrally. In addition to the short retractors which run from the most anterior portion of the piston apparatus—the hoed of the torà,.yue—to the coenuai cartilage eig. 14), the m. erdi-anio. nl:lis_ runn ing between the head of the tongue to the perioardel cartilage certainly has a retrecting effect 18). The chief function cf this long muscle almost enveloping the last third of the piston cart- ilage, is el:tended to the head of the tongue itself (tg. 1f)). Xtz con- traction controls the coming together of the loft and right rows of teeth an the ten:7_5.1e, i.e., the active phase in rasping—the process by which lampreys burrow themselves into their prey. Zn contrast, the antagonistic muscle opening the row of teeth is a relatively sma/I muscle confined to the tongue itself (m. tendinoacapilis). The rasping process is accomp/ished by muscular contractions which move the tongue up anddown end possibly • rotate it. -29- • Figure 20 Diagram showing the action of the pharyngeal pump. a. Pharynx ezzpanded by the action of the mUsoulun hasilnris. b0 mu soujun pharyn re d Constriction of the pharynx through the con- traction of the m •f*Jlarveus kr1-1 -einIzaten of m. basilar:ts. cnrt. ni. Carti:>ao nistoria; Cart. tect. po. Cartilage tectoria ,3t:v , on Sp duct of salivary gland; En ° a' the course o2 the muscle fibres o$ M. basileris is shown. The most importnnt muscular components of the pharyngeal pump are the powerful M. basilneis sud M. haryngeus. it is conceivable that the pharynx is dilated by contraction of tho horseshoe-shaped, envoloping basilaris. En this way, if it is assumed that the gill pouches are closed off, a low pressure is created during the sucking phase. The circulai' ikbres of the M. . - pharyngeus surrounding the„pharynx can e V on the other hand, by reducing the pressure and, providing that the retracted head of the tongue cleses off the anterior o nIng. empty the pharynx of blood and muscle into the gut. (71g. 31). Tho finger-like velum (see p. \ "). serves as a sorting organ. The food fraction ters the oesophagus and the liquid fraction flows through the no w open entrance to the gill chamber. In this connection it must be mention that this sketchy description of the piston and pharyngeal musculature deviates partly from the presentation that Tretjahoff (1 92S), Marinolli and etrengor (1954), and others have developed. The above-mentioned very powerful tï. basilaris is, on the other hand, an auxilliary muscle of the piston apparatus. The m. basi/aris, for ezamplo e forms a covering for the nnterior third of the piston apparatus, i.e., the cartilage Ilero is surrounded by the ventral part of the m. basilaris. Finally, -30- • it should be mentioned that the buccal glands and their secretory ducts are imbedded in the basilar muscle (Fig. 20). p.289 Another muscle group of the visceral musculature consisting of four pairs, serves in the movement of the voler apparatus in all directions. I would hero like to assue,o, contrary to the theory of Marinelli and b-creager (1954), that the importance of the velar apparatus declines significantly after metamorphosis.. Although the velum in the larva functions primarily as a valve to prevent the expulsion of water anteriorly out of the pharynx, it serve s in the adult not only as a valve but also us a filtering arrangement. The musculature of the velar apparatus is also innervated with nerves from the trigemial nerve. . In the next group, the ocular muscles, nere are four strap-like and two oblique muscles. Ulloy permit not only a relatively good movement of . 1I , the eyes but also according to Fr ana (1932), take part in accommodation. , - In enntrnst tr. -4:31 encith,-,mi.n. --S.,,,. ,, ...... *e not only the m. rectus posterior (m , r. externus of vertebrates) but also the n. roctus inferior. In fact Tretjakoff (1927) and Lindstrom (1949) pro- sent the viewpoint that these lower occular muscles are., in addition, also innervated by the n. oculomotorius. The remaining ocular muscles are innervated in the same Lesbien as those of the vertebrates. ' The last group o5;2 the visceral musculature) that of the pharynx ,l may ba briefly mentioned. The nine branchial muscles belonging to this group lie comPletely within the cartilaginous branchial basket, which, because of its elasticity, acts antagonistically to the action of the muscles. The mechanical apparatus of the pharyngeal region of the lamprey oven after gI 0 -31- • motemorphosis is cz relatively simple structure and more easily comparod with the corresponding part of the gnathostomes than the prebranchial visceral musculature. The individual trains of muscles of the musculature of the pharynx will be discussed ) in connection with the pharynx „ !\ itself and its function in the larva and adult. All muscles of the pharynx are innervated by the vagua. • The troponyosino of Potromyzon mnrinus has been recently investigated by Sand and co-orkors (l959). Eloerekoper and Sibokin in /956 ab) reported unusual electrical "spike" discharea in Petromyzon mnrinus. Those can bo detected in the recion of the head at a distance of 25 centimeters and may be correlated with the contractions of the branchial basket. The centre of their omis- sion is on each side between the eye and the gill pouch. The electrical • field iG symmetrical. These authors posumo that the field arises from an electrical organ. In this connection is the interesting finding that primitive Dovonian Cephalespids apparently had eloctrical organs. IV. The Nervous System The nervous system of the cyclostomes illustrates the characteristic structural plan of the gnathoutoes but possesses primitive features in many aspects among which the lack of typical ganglia of the trunk nervous system is worth mentioning. Brai and Associated Glands Tho brain of the petromyzontida is a primitive but typica/ vertebrate' • brain. Tel- ai- Ros- and rhombencephalon are ospecial/y during the larval -32- period, little compressed in length and consequently easy to separate one from the ether eig. 21, 22). The cerebellum is wztremely small. nxtensive investigations on the brain of the lampreys have been curried out bY Jovmjton UL 90 2)Q 9 te2zi (1907), 'erotjakoff (1909, 1910), Saito 12,283 (1930), Larson (1947), Eeior (1048), and others. The largest portion, the eIub-shaped rhombencephalon, comgirises half of the total brain and may be subdivided into a. medulla and transitional region. The caudal limit lies at the level of the first spinal nerve. At the ventral and lateral outside surfaces, hardly any divisions are recognizable. Dors:ally and laterally the rhombencephalon is demarcated from the mcsencephalon by the culons posttectalis, the deeply incising suions rhembemesencephalicus respectively. In contrast to this the ven- tral surface runs almost unnoticeably into the mesencephalon (Fig. 21d). In some species the Culcus rhombencephalieue is said to be continued as a flat coating on the ventral side (sce earinelli and Strenger, 1954). The large fourth ventricle, about the shape and si= of an apple seed, opens into the antrier region of the rhembencephalon in a broad chorioidal sinus which is noticeably es:panded anteriorly of the mid-brain the broad chorioldal sinus. no plexus cheriodalis clothing the sinus ferms numerous folds which prejeet downward into the sinus (Fi, 22). Tho floor of the fourth ventricle is divided oj the aubes ventralis and the rinht and left sulcus *.Untans------clearly in characteristic segments. In the region of the rhomben- cephaion arise cranial nerves V - X respectively (rig. 21). Moments especially characteristic of the rhombencephalon-are the giant col/s of Mueller which lie always ventral • to the Sulcus limitans but very presumably -23- with snecies with respect to number an arrangement. Mueller Q s giant colis off giant send fibres montioned in the nerve column. Although the cerebellum is presumably secondary or is lacking in the Myxinoidea,..it is considered to be a small plate: in the Petromyzonida bordered anteriorly by the fourth vontriolo in which lie coll groups similar to Purkinje cells (Lsrsell, 1947a). The Mesencephalon extends doesally from the CO fissura posterior to the cerebellum and, in contrastithe ventral segment is developed very little. Deviating from the mid-brain in of all guathostomes and also the Mynininoidea the ventriculus mesencephnii opens as a wide choriodal sinus into the anterior region of the roof of the midbrain. In contrast to this the posterior roof segment of the tectum optieum Is highly arched and thickened to form the paired optic lob os (Figs. 21 9 22). The lateral walls of the masencephalon are relatively strong. In the region of the midbrain the m. oeulornoterius arises ventrally and the n. troch/earis arises dorso- .p.284 laterally in the Suleus rhombomesencephalicus. Accorddng to Larson (194%) the trochloaris nuclei lie originally directly caudally to the meson- cophalon and are secondarily included into this region. Figure 22 LnmDetra planer! (E1) Median jcilon throudi the brain oe a 151 mm. long swmally mature animal. 'i.he form of the di- and telencephalon of lampreys is affected by the pronounced development of the organs of smell, especially in the adults. :Ehey irr(,c so anteriorly compressed that the topographical features mentioned Ash elow have scarcely received any consideration. 111, 24- Th po crier borders of the diencephalon are superficially determined by a line beginning in front of the conmissura posterior and running from . here along the sulcus prostectolis to the posterior end of the tuberculum postorious. The demarcation towards the side of the telencephalon is out- . lined clesrly by the fissura telencephalon diendebhalica. At the diencephalon the segments of the opithaismus, thalamus, and hypothalamus can be dorso- ventrally distinguished. The roof of the diencephslon belonging to the epithalamus and rising steeply billows out into on anterior-dorsally directed opithalial sack-- the secoua do alla (parencephalon) lying dorsally over the caudal segment of the tolancephalon (Fig. 21). In the posterior segment of the roof are found the largo habeaular ganglia of which the right ganglion is always the stronger developed. The unusual size of the ganglia is associated with the gI › strong sense of smell found in cyclostomes. The greater development of the right ganglion is believed to be caused by its connection with the pineal organ. A stecial characteristic of the roof of the m±d-brain are twe hose- like structures provided with bladder-like extensions of the brimming out p.2G5 of the opendyms of the mid-brain (Figs. 22, 25). These rJineal and para- pineal organs are apparently the lateral homologues of a paired organ of which the loft has been more modified and is conseqUently more or less con- cealed under the right. En its histological structure the pineal organ is partly reminiscent of the histomorphology of the eyes (Pop and Duss, 1959). According to Studnicks (1905), the structure is a photoreceptive sense organ of the o•endymus. This viewpoint is supported morphologocally especially by the fact that the tissue under the organ is transparent and the fibres -35- of the pineal nerve (Tilnoy, 1937) terminate mostly in the tectum opticum. Your (1035b) was able to show that, in ammocoetos, the diurnal rhythm expressed by changes in dark end light pigmentation was discontinued vhon the pinera organ was removed. 'This menus that the activity of the meIanophcros controlled by the posterior portion of the hypophysis was influeneed. secretory function of the pineal complex of lampreys has been already sueygested by Tretjakoff (1915). According to Knowles (193), the nuclei of some of the pineal colle display certain storage substance dependent upon the illumination. For the differentiations of the ependyms based on its function as an organ, the subcommiesural organ lying under the commissure posteriorius should be mentioned. Maeui (1052), ascribed a secretory activity. Accord- ing to Adam (1956), no connection exists apparently between the secretion c“,' the subcon 4 ssurnI ogens and the formation of Reisznergs threads. The thalamus proper, however, and aise the hypothalamus is little developed end divided ln comparison to the plegicstomic fishes. The swelling of the chiasma er '?er in the ventricle toward the tuberculum posterius. A saccus vasculosus is lacking in lampreys. A detailed description of the walls of the > third ventricles has been given by Adam (195s). Figure 23 Dagram showing the location and parts of the hypophysis of lampreys Tho hypophysis of lampreys according to the relationship in vertebrates, la composed of epithelial, glandular, and cerebral portions. The glandular portion arises • in the embryo in connection with the naso-pharyngeal coed -3C- 1 II (Leach, 1931), and 12es closely divided foi the cnnalio nasephnryngens by moans of a layeL connective î.issue, the infundibulum ventral. eteip. 23) ,r1 According to pichford and At: (i957), as well as Zamor and Schrours (1955)„ - , the following segments of the hypophysis are distinguishable: Proado2ohypephysis, mostly basophyllic: PAS positive cells (Kamer and schreurs, 1959). in addition to those are individual chromophobic cells oning1959). Cenadotrepic hormones are presumably produced in the basophyllic cells. Aeseadonohypophysis: Mostly chromphobic cells, also basophyllic colis which can be stained with aniline blue or chromhaomotoxylin phloxin eGomer (Zumer and Schrours, 1959). They are less PAS positive than the basophyalic coals of the Proadanohypophysis (Lanzing, 1959). Somatotropic hormones are presumably formed in the chromophobic cells. ân the basophyllic e colls thyrootropic hormones are formod. The latter ore only active shortly Of ore and after metamornhosis. Metaadonohypophysis: Coils with a delicate acidophyl/ic plasma in which, dependent upon the phase of activity, are stored more or less basc- phyllic granules. Ail cells of the nctad9nohypc.phyEi$ ara oriented by the cell apex to the capillarieo botwoen this segment and the nourohypophysis. The motsadsnohypophysis is active during metamorphosis and during the spawning miration (Zamor and Schreurs, 1859; Lansing 1959; respectively). St is ae.med that the active ingredients for the movement of the melanophores is formed hero. Wouropypophysis: Tho nourohypophysis is made up of thin fibres form- ing tho floor of the recassus infundibuli. (Fig. 23). ât is delimited on 411 the ventricular side by the ependym cells and on the side immediately lower -37- to the metandenohypophysis by a dense net of capillaries. The presence of nouresecrotory mterial may be demonstrated in the neurophypophysis, which, during the larval period is bui/t up and which is used up even after meta- morphosis. é‘coording to Kamer and Sohreurs (1950) this section of the gland serves in the maintenance of water balance. Morphological investigation on the pituitary oe lampreys have been carried out by Tilnoy (103,7) and Green (1951). Eergquist (1932), Heir, Mazzi (1952), end, Bargmann (1953), have shown that there are nourosecretory, active colis in the region,of the nucleus preopticus. Bargmann especially ( 3, 953), hem shown a transport of the secretion into the r;euohypophylis. En addition to the gomorpositive neuro-socretion secretory granules have been observed lying mostly extracellularly at various points of the thalamus. Lamprey have no saccus- vasculesus. The te ,.elncephelon of the Petromyzonida Is small and esentially olfactory. 'She two homisDheres connected by the foramen interventricuisre to the vriculus innor are externally divided into a buibus and lobus The lamina terminal:Ls and supraneuroporice are thin, :90- cause of the pronounced development of the sense of small the forebrain is anteriorly compressed. Consequently, the hemispheres are laterally bsnt and the primordium hipnoeampi is swollen in the ventriculus imper. 'The Nerw! Cod The nerve cord of cyclostomes is shaped like a tape (Fig.. 24). From the histological construction of this structure white and grey matter can be difeerentiated. Dorsal and ventral horns are lacking. The motor cells 0 appear in three forms and lie mainly in the lateral tract oe the grey matter. -38- The fibres of the white matter have no "myelin sheath." Elements which are especially oherneterietic of the White matter are giant fibres arising from the giant colla of Mueller in the middle and hind brain (Fig. 24) and those are said to forward nervous impulses directly to the chief organ of locomotion—the tail. The central canal is narrow but continuous from an crier to posterior. No capilliories penetrate the nerve cord since the tape-like shape makes possible the direct exchange of metabolites with the surface. According to my own unpublished observations neuro-socrotory p.287 cells occur in the nerve cord of the Patromyzontida. A characteristic hypophysis spinali• eaudalis is locking. A thorough investigation on the nerve corn o lampreys have been carried out by Deetjakoff (1900). The central nervous system of lampreys is covered with au endomeninx overlain by- a ectemoninx. Between the two is found an intormeningeal • tissue rich in fat and pir4,ment cells e 'which at various sections, i.e., over the nerve cord e can be thick and act as a cushion (van Oolderen e 1925). Viguro 24 Lampe tra planeri Cross-section through the spinal cord in the region of the third gill pouch. Ch. chorda e grS grey matter; NP giant fibres, VS white matter, Zi central canal. Magnification 75 times. rr:ce Perip'noral Nervous System The following details of the peripheral nervous system of lamprey are dorsal and ventral nerves of tho cord are not worth mentioning. The united, in contrast to those of gnathostomes e to form spinal nerves. The dorsal sensory as well as the ventral motor roots fork independently of 4, each other into a dorsal und ventral branch. The sensory roots appear in -SC- 11, the region of the myosopts and the motor roots show up &bout the middle of the myoteme. Characteristic spinal ganglia are lacking. The first three segments of the nerve cord sand out only ventral roots, 'which run from the anterior of the branchial basket . to the ventral area of innervation of this structure. The following motor spinal nerves terminate in the vagua and go around the caudal portion of the pharynx. Tho system of cranial nerves also exhibits departures from the basic plan of the gnathostomes. Tho last cranial nerve—the n. vagua--bas a root ganglion, a peculiarity which only occurs in the amniotes. The n. vagus, n. glossopharyngeus and the nervus laternIis of the focialis supply L,Le skin uac m.us,..1.41at,,,Le of the pharynx. The —u lot. post. supply the • lateral "nouromasts" of the pharynx end the back. The wo-otic group of roots are mainly represented by the n. facialis ,• 1I › and n. trigeminns. With respect to the trigeminus it is worth noting that Lindstoom (1049 ) has questioned the homology of the n. mandibularis and . maxillaris with the corresponding branches of the gnathostomas. The , , . facialis complex departs from the relationships in the gnathostomes be- „ .: cause of the lack of a rnmus mandibularis intornus and a remus pharyngous. J Tho corresponaUng region of innervation is in this instance provided by the o. iem.thusaccordieg to Marthelli nd 3—onge4, 1954). The nervous supply of the eye muscles corresponds in principle to the‘. p.288 relation present in the gnathostomes. For details seo Corde (1928) 0 end compare with page The sympathetic nervous system of lampreys possesses very primitive characters Typical sympathetic nerve trunks are lacki„ng. In numerous e investigations, Kupffer, 1095; Johnston, 1905; Allen, 1917; Protjakoff, -40- • l 27; Mlochin e 195D; and eIsewhere 2 numerous nerve cells have been assoc- iated with the sympathetic system and the adequate form of a "sympathetic nerve trunk" has been sought without an' convincing evidence up to the present. :if von Lindstroem's demonstration (IUD) thnt branchiecophalic nerves presumably supply afferent fibres to the vessels of the head is very inconclusive. The autonomous system of the cyclostomes can be eveluated on the b.asis of other researches as a diffuse texture especially thick in come spots but in which the cells are not united for form ganglia. "Its connection to the cerebro-spinal system is still to bo explained. V. ;onse Organs of the Head The major sense orgens--elfactory organ:D v oyes o and organs of equili- brium of the lampreys correspond to those of the gnathostomes in their distribution and cerebral association. They differ considerably in some details of their make-up and function. In addition to primitive features special >functional differences may be observed. The Gran of Olfaction The olfactory orgnn of lampreys has no real connection with the sur- rounding water but is in contact with the unpaired dutus nasopharyngeus (tube of th hYP0PhYs1 s; rigs. 18 e 25). This structure begins with a median opening somewhat raised above the body surface of the head and continues to a position under the chords.. The olfactory organ itself is very lare and in many species compresses by spatial expansion the anterior part of the brain (Pig. 25). Of special interest is the lack of a edial- • nasal septum. • Figure 25 Lot: Schematic drawing shoving the relative positions of the ductuo; nasopharyngeus e olfactory organ, brain and chorda (after Parker and rlaswell from Grass) CD Corda; G e assessory glands; Oh, ganglion habonulae; H, hypophysis; M, entrance to the sac of the hypo- physls; wiD olfactory norvos; NP e ductus nasopharyngous; OD lobus olfactorius; Op, lobus opticus; P, pineal organ; P, parapineal organ; S, s'e=us na ai; To entrance portion; V, vaivula. • night: Uori2cnta1 section through the olfactory organ (after Matthes). 0, eye. The other letters as above. ' The two bilaterally symmetrical halves are broadly fused with each other. 7).2S9 According to the interpretation of most authors this unpaired arrangement is secondary but indeed very oie phylogenotically since, according to Stensio (195S) e it occurs in the Cephalespida (Xleorekoper and van Erkol, 10 ). The innervation of the olfactory organ is bilaterally symmetrica/ id corresponds to the form in gnathostomes. Two lateral vescicies grow ‘, out of the embryonal urpairod anisge but do not romain alter the formation of the continuation of the forehead which is subdivided by the exterior opening (:Marinelli and Stronger, 1954). The olfactory sack itself is surrounded by a cartilaginous capsule and narrowed by numerous septa e of which the medion dorsal and ventral septa are the largest Ceige. 25, 20. The glands present in the nasal sack ouen into the space between the septa. The olfactory celIs are chiefly conCentratod in the septal epithelium. The circulation of water in the tube of the hypophysis occurs presumably passive/y. It has been assured that the widened posterior end of the passage Is opened and constricted by the contractions of the pharynx. "in the olfactory sack ttsolf, ciliated epithelial cells provide a current of water. I I › -42- • Figure 2G Lametra Dlanari (B.1.) Cross -section through the olfactory organ of a 140 long, semually mature animal. cartilaginous capsule of the olfactory organ; mS, ventral septum; Sp lateral septum; Oac. hyp., saccus hypo- 'bvseos; Ductus nascpharyngous. Mgn. 75 ti=s. Tho sensitivity of the olfactory organ has been little investigated. Mlearekw)er and Morgensen (1059) showed that adult lamprey can distinguish the specific smell of various species of fish. In larvae the olfactory organ is essentially simply organized. -.-,,, .e,,, ,1,..,., ,,,,,,.. . The eyes of the Petromyzontida uppaar in the embryo but develop slowly gI > from dermal and ce active tissue layers during the larval period. They attain their final form and position after metamorphosis. The larvae . appear, therefore, to be eyeless in a superficial examination. In con- trast the eyes are extremely prominent in the adults being a sbiny silver in colour. The structure oe the aye corresponds very closely to the vertebrate aye z, although it remains primitive in many foatures(rig. 27). The sk.in forms a cornea ovor the eye under which, according to l'i'manz (1932) the b,.fibus in moveable. The inner cornea (membrana descementii plus endothol) rune into the tendons of the colora and rectus (l.o., it is still somewhat delimited). A ciliary body as well es a zonala sinii is lacking, the spheroid ions in which the centre Is divided is held, instead e a membrane. by The vitreous body Is acollular. The visual elements of the retina are p.290 -43- , not differentiated in rods and cones (Franz, 1 )32). The thin sclera per- . mite. a change in form of the bulbus by the ocular muscles. De cause of this a movement of the bulbus itself is not possible and o primitive . mechnnism of accommodation exists which has t however, attained a high level of functioning. Figure 27 Horizontal section through the eye of Lampetra fluviatilis (after Franz from Grasse). (Labels in latin). The peculiarities of the ocular muscles and their innervation have already been discussed on »age eîf›. The orbit of the eye is linod with a membrane of connective tissue. . II , erne Labyrinth Tho dermal labyrinth of lampreys enclosed in a cartilaginous capsule, exhibits important differences with respect of the feature of this structure in gunthostomes. Those differences must bo c•nsidorod a phyologenotically old condition. The following features are of especial interest (notably from the work of Buriot t ICU). , The endolymph is maintained in constant motion by the lining of the labyrinth consisting of "fIagollatod epithelium ln which the ondolymph of p.201 tho semicircular canals and the utriculus does not take part. Only the two .vertical semicircular canals of the vertebrates are represented. • The utriculus has two small ventral swellings of which the caudal pv'estzaby corresponds to the lagena and two large laterally directed out-pouchings (cillar spaces) unknown in vertebrates. The abve-mentioned circular currents are said to be confined by the latter. With the eception of cristao in the ampullae and a small tel "endstelIo" in the dorsal canal all the sensory endings are connected with each other. This condition in the guathostomes is only observed in the embryo. On the medial side are two tube-lika protrusions vhoso homo- lev with the ductus endolyiepathicus end the intrudinez canal of the laby- rinthe is questionable. A good presentation of the dermal labyrinth has been given by Marinelli and Stronger (1954). ?or dermal sense organs see page f:rïe. W. The Vascular Syntem The vascular system of the lampreys corresponds in basic principles to that of the primarily aquatic gnathostomes. Noteworthy departures g , ezist in the I venous system with respect to the distribution of vassels especially in the formation of highly branched sinuses. The so-called bloed sinuses are greatly developed, primarily in the anterior region of the body. Detailed investigations on the vascular system of lampreys have been • carried out by Natta (1397)(1923); Cori (1908); Xeibel (1926); and Trotjakoff elfyvV., The :zart and Arterial System The . heart o2. the lamprey is directly ventrally behind the pharynx in the most anterior segment of the coe/om. Sinus venesus e atrium and ventri- cle ezist as differentiations in the wall of the double bout tube (Matta 1023). En the larva they are in a plane, ona behind the other. The structure is so compressed in metamorphosis that the atrium now lies loft -45- • near the ventricle. Tho dorso-vonteelly drawn out sinus venomus is inserted between both from the back ( F ig. 20). Figure 2S Lambetra--- fluviati/is (L.) goart; a dorsal view , b. frontal section; the dorsal half of the heart seen from below, the sinus venosus brought out oe the normal position. (1'edrawn from Marinelli and Strenger) • The pericardium nestles closely to the heurt being ceudal/y supported by the Peridozdial cwetilage (seEl page 27-a).. It is connected to the ventricle by the muscular beginning (bulbue.., • arteriosus) of the aortal trunk which, a'?ter sending off branchial arteries D 6g forks into two branches. Xn the larva one branch supplies the strongly developed endostyle and, in the adultthe) other supplies the piston musculature which is shoved in hare, • gill arch arteries (a. branchial afferons) are present in all of Wne Which the first pair, principly as right and left voler arteries, supply blood to gill elements. The arteries supplying the gill filaments arising .F. -om the c,eir arch arteries, (a. Isminarum branchislum efferons) proceed along the proxime _Dphor•y.eri _ The veins (v. leminerum branchielum\.,, follow along the distal periphery. l'oth series of vessels are connected not be capillaries but by lecuner spaces, (Fig. coated with a layer of endo- thelium 'Cterbe, /952). The volas of the gill filaments run into branchial veins (a. branchialls efferens) which flow into the aorta. The veins of the gill filaments have also direct connection ventrally with the ondostyIe, velum und oral cavity. In metamorphosis the vascular system of the pharynx is greatly modified. For example> bread enveloping sinuses arise between (2)*q gI , the gill sente and servo as water cushions during expiration (sec page 2ffl. -46- • Figure 29 Vaseularization of the gills of larval lamprey artery of gill arch; (n. bun:whin:Lis affQrsns) artery of gill filament (a. 15,:elinarum branchialum afforons) iU31V, ef gill filament (a. IaPlinarum branchialum afferons) BV veiu of gill arch (a. Tho 2ora daseendems lying immediately under the chorda dorsalis tween the tris cardinal veins e gives off sogmented vessels ms well as vessels to the head and abdominal organs. P.mong those the a, mosenterion is ospecially voluminous. Et runs along the hepatic artery in the spiral fold of the gut. .....-__The Wiood Sinuses and the Venous System The sinus-liko lacunae spaces are characteristic of the vascular system of cyclostomes. In general these lacunae arc enclosed betwoon the g1 › arterial capillary nuts and the small veins and are coated with endothelium. p.293 Spatial folds are recognizable in addition to those of which the arrange- ment is difficult to ascertain. (Nest/er e 1890; Tretjakoff e l026; Marinelli and Stronger, 1954). .Uven the function of the laeunar spaces is difficult to evaluate. Cortainly one cannot go very fer astray in assuming that this differentiation is secondary and has arisen in connection with the reduction of the skeleton. They may partly serve as watery cushions or have some . other mechanical function. 7hey may eso ut as reserves for liquids !:riniz the animals'. sojourn in saa Wâter. The caudal cardinal veins arising from the unpaired caudal veins end the cranial cardinal veins unite in the sinus vonosus. The right e very • short, ductus Cuvieri takes up the trunks both careanal veins and empties • • into the sinus vsnosus. The loft ductus Cuvieri is barely represented and is oven reduced in early larval life (Marinelli and Stronger, 195d). In addition to this the %Iona • ugularis coming from the head and the venus heoctica entera the sinus vonosus. The true lymphatic system is said to be absent (Teetjakoff, 1927). The Blood Lamproy blood contains ireeé;ular, more or loss Spherical, nucleated erythrocytes as von as polymorphic nucleated leucocytes and lymphocytes poor in plasma. The cellular elements aro formed in the spiral groove of the gut and the lymphatic tissue oe the kidneys. ,e 0 studied the blood corpuscles of Lampatra plancri by naunicâ (1946ab) ------• staining with vital dyes. According to Adinelfi and Chioffi C19 S8p 1959) two hemoglobin components may be separated from the blood of the larvae by electrophoretic techniques. Three to four components appear during meta- morphosis. Wald and . Riggs (1051> were able to show that the hémoglobin of Patromynon marinus had a only Haem with a molecular weieht of 17 000. %Ihile the amiuo acid composition is reminiscent of the haemoe.hin of invertebrates the transport function ie similar to that of vertebrates. Primitive ana highly speciali=d properties seem to be combined. Accord- ing to Pawlow and Skirstymouskaja-grolik the blood of Lampetra fluviatilis may bo ast:Inguishod from that of fish by its respiratory properties, vanova-nerg and Sokolovn (19 0) reportod seasonal variations in the number of erythrocytes, haemoglobin, proteins and blood fat of Lompetra fluviatiIis. The iodj.ne content of the blood during anadromous migration in Petromyzon 4 Ie marinue i2 sirmieicantly lower than that pre,sont in migrating salmon or -40- "?.laifischo" from the same biotope (Fontain and Leloup, 1950). VSE, The Foregut or Lampreys Outside of the Coo:1°m :1'.hat part ci the foregut lying outside the body cavity may be divided Into an oral cavity, pharynx end branchial pharynx. /n the larvae these segments are arranged linearly but in the adults the branchial part is modified by an extension of the oesophagus to a blind sac (F ig. 30). . The Larval Mouth and Pha7,v1:lx The mouth cavity of larvae Is without tooth. The pharynn e in con- trast ta that in the adults, has a very wide lumen. Both sections are separated from one another ventrally by a circular fold eig. 30 e 35a). A thick wreath cf radially arranged branched tentacles directly in front of p.294 11› this fold projects outward into the mouth cavity. The num total of those tentacles makos up the oral "weie--a coarse fliter screening out the relatively large particles from the branchini pharynn Tho mouth opening is delineated by a large u-shyped upper end a narrow 'lower lip eig. 49). The broad pharynz IV closed oef posteriorly. by the velum . The two flap-like parts of the velum are back pressure valves serving in the transport of water outWârds. Figure 30 Diagram cf the anterior gut of the lamprey larva and the transformed lamprey. 'Me ,K.dnit Mouth and Pharynx • The oral funnel may ba compared to a concave dish having the appearance -49- i I sucton cup. n>4 the grown adult it is formed from the lips of the lrvs. 3i possesses sharp, horny teeth end bears tentacles on its peri- phory (Figs. 4, 17 e end 49). The mouth merges into the gul/ot in the vicinity of the cartilaginous ring. The anterior pert of the gullet is hold open by the cartilaginous ring end the anterior "elytra" hold open the entrance to tha gullet. This permits tho head of . tho tongue, the moot anterior portion of the piston apparatus, a free beck-and-forwards motion in this segment. Also in the region of the pharynx lying just behind tho gullet the musculature and skeletal parts prevent a collapse of the walls. The pharynx ends posteriorly with the complicated velar apparatus. This structure itself is formed by a combination oe the right and left cartylago otyliformis (Fig. 14, 15) and the* nenrooranium. It acte as a sorting device :hie h surrounds dorsally the entrance to the oesophagus and ventrally w-,,er passage. The finger-like velum extends between the two entenncez anteriorly into the lumen of the pharynx (Fig. 48). now this arrangement functions during feeding vas investigated by Reynold (1W1). Tho following outline is hastily sketched and departs from the customary presentation (Fig. 31). Tilz) lov pressure in the oral cavity necessary for sucking it attained by the stronc m. basilaris which by its contraction opands the lumen of the phsrynx (See page e) At the ( A H same time the connection with the branchial cavity is closed partly through muscular action and partly through a valvular action. The sharp tooth of the sucking mouth ere prossed into tho skin of the victim by the circular muscle, of the mouth. This strong anchorage makes :lossibie en active rasp- ing in the hoed of the tongue. Tho complete sealing is achieved by the 11, peripheral cirri. _As Eglite vas able to show, the cirri are very largo during the feeding period of the adults. The soue process described above with the exception of the penetration of the tooth, tubes place when the animnl nnctors itself to a stone or to the substrate. The hoed of the tongue during the feeding net is brought forth nnter- iorly into this region of low pressure and pressed in the ventral part of the sucldng"funnol against the skin of the victim. The ventral row of lingual . teeth serve entirely to anchor the base of the hoed of the tongue. p.295 However, the dorsal Part moves very quickly in a semicircular fashion up and down end in this way the two posterior rows of lingual tooth act in a scraping fashion (rig. 21). In the dorsal movement the posterior row of labial teeth come forward (contraction of the m. tendinapicalle) and these open in the ventral movement (contraction of the m. copuloglosous obliouus). Secretions of the salivery glands are poured out during rasping. This secretion inhibits coagulation and is haemolytic. The confirmation of the anterior row of teeth of the head of the tongue has been experimentally vorîfied. Figure '31 Diagv-7eu show-1.1g the r,›îl-zg and c.- CL'ineo movements of parasitic lampreys. The hand of the tonguo bores into the tissues of the Prey in the following way. When the low pressure is greatly reduced through tissue . particles and blood the head of the tongue is retracted into the gullot. The lamprey lots its victim free and empties the pharynx by- the contraction of the m, pharyngeus in the oesophagus. ny this action the head of the e51- • tongue serves as an anterior pharyngeal plug. Further on, the velar apparatus acts as a sorting arrangement. It is quite possible that, with a firm anchorage of the teeth of the oral funnel, the act of swallowing can occur while the lamprey is still attached to the prey and that in such cases a second rasping phase can occur. The type of wound occurring in 2- small prey fishes (see page s4e) makes it likely that a second attack takes place. It might take place, for example, when the fish is crippled by the first attack. In large prey only hole-like wounds can be found. p.29e A description of the complicated musculature of the head of the tongue _ and the piston of the tongue is given on page 9 I. The sack-like ealivary glands develop, first of all, during metamorpho- sis from the epithelium of the floor of the mouth. These very functional paired glands are imbedded on both aides of the m. basilaris at the approx- II, imete level of the olfactory organ. The secretion on both aides is by a long excretory duct emptying anteriorly under the head drained of the tongue. The secretion possesses anticoagulatory and haemolytic properties. Modern histological investigations on the salivary glands have been carried out by Gibbs (195G) and Baxter (1950. The active epithelium of the glands in parasitic opeelea become» functionless after the feeding period» In non-parasitic species the glands are still formed although the epithelium never becomes active. The nranchial Pharynx of Larva and Adult The larval branchial pharynx of lampreys is a filterefeeding device (Sterba, 1053). Only »von of the eight visceral pouches break through. •o first pouch of the gullet formed in front of the hyoid arch never.opene Fig. 32). The embryons] gill arches are differentiated into a lateral branchial arch plate and supporting structures of the gills. Both sections aro connected by a thin membrane. The branchial rods on the branchial arch plates are not vertical but somewhat anteriorly directed. Figure 32 Lampetra planeri (81.). • Frontal section through the branchial pharynx of a 3.8 mm. larva (above) and a 8 mm. long embryo (below). G, brain; lib, primary hyoid arch; 2Kb, a second branchial arth artery; 00, oesophagus; Nat, Pseudobranchial channel; SH, secondary hyoid arch; Va, velum; 1, 2 3 9 gill pouches magnification 60 times above and 45 times below. Explanation of Table 6 Figure 33 Diagrammatic illustration of the rearrangement o the larval branchial arches to form the Branchial arches in the adult during metamor- phosis. a. Typical branchial arch of the larva. The cow. secutive branchial plates are widely fanned out and overlap eaCh other. b. The rows of branchial plates fall backwards b.0. ■ coming parallel to the axis of the branchial rods. - c. Branchial arch of the adult. ',AuKo" outer gill opening. 01 - caudal row of branchial plates of a gill bearer. cr 01 .• cranial rows of branchial plates of a.g111 bearer. , • ZEEE - inner entrance to gill Chamber.. ' -53- . - inner gill muscle. • -. i . . , KBA - artery of branchial arch. ; KB1V vein of gill.tilament. ! ,K.Ka - cartilage of gill arch. . „ KP1 - disc of gill arch. • Kt gill bearer. • . . • tKU • deep branchial muscle. VU - connecting membrance between the plates of the neural arches and the gill bearer. . • - VS - venal sinus. -- - Figure 34 Lnmpetra plancri (B1.) a. Frontal.section through the branchial pharynx of 75 mm.- long larva. b. Horizontal section through the branchial sack of a 145 mm. long, • . sexually mature, lamprey . Au, eye; D, diaphragm; H, heart; Khi, gill filament; Xpl, plate of branchial arch; Ri, entrance to the gill chamber; KKAu, exit from the gill chambor; XL, lumen of . pharynx; KS, lumen of branchial anck; Kt, gill bearer; Pa, psoudobranchlal groove; S, septum; II, weir-like overlapping of the gill filaments. ve, velum. Magn. a. e six times and b., about. . four times. (Figs. 33 * 34a) A vertical arrangement of gill filaments. arise on the • p.297 cranial and caudal sides of the triangular gill bearer shown in cross- section. On the ventral and dorsal sides of these the gill filaments grow out. The caudal gill filaments of the gill bar in front of it always over-. lap the cranial gill filaments of the following gill bar., 'This overlapping - requires, however, a lateral basketm-like cloaure ot the wide larval gill chamber (Figs. 33a, 34a). The atrium lies laterally from this weir to the gill chamber which is widely expanded dorso-ventrally. Gill alite in the gill chamber open to the outside (Figs. 33, 37). The gill slits are bent back by a wide plica trematica. The inner parts of the gill bare, the broach• like diaphragms, surround the narrow, slit-like lumen of the branchial pharynx (Fig. 33a). Between the consecutive diaphragms lie the broad entrances into the gill chamber. The velum consisting of right.and loft sail-shaped portions, terms the anterior boundary of the larval branchial pharynx. The large, sunken tee in endostyle gives rise to-an arch on the floor of the branchial pharynx (Figs. 35b, .0). The anlage of the adult oesophagus narrows dorsally to. this region ("Epithelplacode"). The larval branchial pharynx (Fig. 35). •• The vascular system of the branchial pharynx corresponds in principle 41, to that of the vertebrates but shows, in. addition, some interesting peculiar• ities (Nestler, 1890; Cori, 1890; Bette, 1923; Sterba, 1953). Nine paired F!,' e(.1 vascular arches in all are present of which the first is and the second, A -le•-partli,24sisimplifiedi The afferent arteries are connected with the efferent arteries not by capillarlea but by a sinus connecting the gill filaments as a unit (Sterba, 1953). An expanded sinus also runs through the roof of the branchial pharynx and the outer wall. (Compare also with )-15 page -292). - The larval gill elements become profoundly rearranged during metamor- • phosis. A respiring pharynx develops out of a straining pharynx (Sterba, 1953). A ahortening of the region of the branchial pharynx may be detected : The gill bars are flattened to a septum to which the rows of ' externally. gill filaments are attached (Figs. 33b, c). In this way a.direet route for • the eter is made possible. Because of the shortening of the region of . the branchial pharynx, the individual gill pouches are compreseed tOgethOr and their angle of declination to the. body axis increases (Fig». 33, 34b). The entrances to the gill pouches become narrowed to slits and the atria to the gill pouches disappear. Out of the above mentioned epithelial placode the opibranchial segment of the oesophagus arises during metamorphosis. It involves the leagthening of the larval gullet anteriorly to the pharynx thus bridgingat the same time the branchial pharynx es also page 293). The . 71Ji' --- • ventral part of the branchial pharynx is now represented, by. a posterior b/ind, closed, elongated sac connected anteriorly to the pharynx. It is., connected through lateral alite with the gill chamber and is now termed. a water passage or the "gill sack"., (Figa. 18, 30, 36). • „ , The adult gill. chamber (gill pouch) is practically surrounded on all. sides by a blood sinus (Fig. 34b) aerving as a water cushion. The localu- ized pressure of the muscles of expiration, especially that of the m. constrictor, externUs, is rendered more uniform about. the chamber. This muscle is reinforced by several auxilliary muscles. . The dilation of the , lulilen of the gill chamber is partly achieved by the elasticity of the eaetilaginous branchial basket end partly by muscles. For a thorough trZateent of the arrangement of these muscles see Marinelli and Stronger, • . The morphological changes of the branchial pharynx are accompanied by characteristic histeogical changes. Of especial interest, la the reduction t>i tissue between.the secondary gill filaments, AsSterba ,(1953) was able • to show, the total respiratory surface of the larva in comparison with that of the adult han been increased by a quarter through the fusing of the inter- p.296 lamellar nests of cells. (1eadings of Table) 1 2 3 , 4 . 5 6 Animal Length in mm. Weight - Volume Body sur- Surface of ratio of . in C. .in mm. face in mm, » gilla.mm. , 6 to 5 1. Larva 2. Larva 3. Larva 4. "Querder" The external gill openings of the adults are narrowed from the front by the plicu trematica, a structure also present in the larvae. In addition are two valves and a row of . papilla on the poaterior margin (Fig. 37). Figure 37 • leelm fluviatilis (16.) . . Frontal section through the external gill openings as seen from below. Redrawn from Marinelli and 8trenger. General anal sis of the function of the larval and adult branchial .harInxt An onalyaisof the function of the larval and adult pharynxes involving core, pontoons is not just of limited importance but also has fundamental implica- tions 531 the understanding of the •volution of Chordates .(Sterba, : 1953, 1960 a, b). Explanation of Table 7 Figure 35 Lampotra planeri (Bi.) A median section through head und branchial pharynx of a 03 mm. larva. Craniad from , the ductus hypobranchialie co Cross-section through the pharynx of 92 mm. long larva caudally from the ductus hypobranchialis.' -57- er e caudal "Flimmerrimme", Ch, chorda; E, ondestyle; " EPLi epithelial plaeodo. Anlago Of the adult branchial • oesophagus. Esp. endostyle. caudal, spiral rolled out portion. 0, brain; H, heart, Ebl, gill filament; Le, liver; 0e, ocaophagus Pelt, Pseudobranchial groove; AM, nerve cord; Vo, velum; vKA, ventral branchial artery. Uagnification: a 9x, b and o 12x. Figure 36 • Lampetra planeri (B1.) Cross-section in the level of the thyreoid through the pharyngeal region of a sexually mature lamprey. Ch, chords.; Ebl, gill filaments; EL, lumen of the gill chamber; ue, lumen of the gill sack; M. cardap, musculo cardioapicalie; Ce, Oesophagus; Uld, nerve cord; StS, Stempel sinus; Th, thyroid; T. ing venir, taenia longitudinalis vontralis; veA, the ,teo branches of the ventral branchial artery.: x12. • • Figure 88 Itarrkwt_a_— a planeri (731.) Frontal section through the pharynx of a 86 mm. long larva in the region of the ductum hypebranchialis. Esp. ondostyl, caudal, spirally rolled up portion; OvEA, forking of the ventral branchial • artery-. 2, Z, 4, S. EB, gill arches; Pea, Pseudobranchial groeve and its ascending branches; Ve, velum; x12. Since the following considerations are based on the latter view, it is first of all necessary to review the general thoughts on this subject. The larval branchial pharynx la a filtering>device with breathing being of incidental importance. Both functions are in a reciprocal relation. The principle of getting food by filter feeding is extremely inefficient from • the standpoint of energy. The amount of energy that must be expanded to collect a given quantity of food is greater than all other means of feed- • ing. Especially evident are the dimadvantages of this system when it is first considered that the necessary energy per unit area of the filtering system increases with increasing body volume, 14e., in the filtering system of water, especially the inner slime filter. Tho energy requirements per unit area of the'filter systems increases with'increasing size. The reason for this discrepancy is caused by an enlargement of the filtering - surface which means that more energy must be supplied and the transport aystem expanded. The basal metabolism must be increased to provide energy. for the mucous filtration to the extent that the ratio of basal to total metabolism is unfavourable. As a result, the metabolium concerned with growth stagnates. From the phylogenetical' viewpoint the body size of mucous filterers is small (TUnicatea, acranla, larval petromyzontlda). The lamprey themselves supply two pieces of evidence in support of theory. - First of all, the maximal size of all species of lamprey larvae is independent of the variable body'size of the corresponding adults. This tact cannot be explained by other theories. Secondly all larvae require , . ) 4 - 5 and some, even more, years to become 15 - 20 times as heavy. The limits impoeed by filter feeding are independent on the species of lamprey. It is elso.of interest to note that the forerunners of the lampreys in the Silurian period were filter feeders and never attained a large eize. — it is evident that the adults can increase their body size only hy abandoning the mode of larval feeding. Active predators, in the course of metamorphosis, develop from inner mucous filter feeders. It is reavonable to assume that this step by which the lampreys are able to increase their . body size is a reflection of the same step which occurred in the development of vertebrate history. Since the original chordatee were mucous filter feeders their mode of feeding must have also governed their size and this likely considerably influenced their development. It can be seen that the . change of feeding in the lamprey has wide-spread phylogenetic implications. Special analysis of the function of the branchial pharynx of the larva: The etrenm of water in the pharyngeal pharynx of the larva is continous. The rhythmic pulsations of the velum and the contractions of the branchial pharynx are damped (f‘e page e1-3). Sy means of the pressure of the stream and bands of sua, water proceeds through the branchial pharynx and trickles from here through the muceue filter and the sieve elements in the anti• chamber. The water stream 18 . 1)re-filtered in the oral cavity. The coarse particles are held back and expelled by a sudden strong contradition • of the pharynx in which the water is emptied ' predominantly anteriorly. In this connection it is not without interest to point out that Ascidian and Selpen exhibit similar' movements of expulsion (Werner, 1959). In the pharynx, especially in the region of the secondary hyoid arch, are several groups of mueogenie colla which, according to Itiekebusch (192 8) produce the mucous -60- threads in which the nutritive particles are snared. Bterba (1960 a, b) • presents, on the other hand, the viewpoint that lamprey larvae along with Ascidie, and evidently other Acraniniata, produce a continuous pouch-like, mucous filter with the help of the endostyle. The extremely large endostyle of the lampreys develops from the walls of a sunken portion of the floor of the embryonal gut which folds into a . cavity and romains in contact with the pharynx by means 01 theendostylic passage. > During metamorphosis the endostyle is mostly fused with single' groups of cells differentiating into thyroid epithelia. (Bterba, 1953,. also refer to page -30e a, d Fig. 36.) Of the various epithelia of the endostyle the glandular epithelia, grouped in a cylinder, are the most etriking. Preliminary investigations (sterba, 1953, 1960; Schneider, 1961) indicate that the two paired cylinders each have a different function. The dorsal cylindrical glands secrete pre- sumably in connection with the epithelium of the broad ciliated band, a • secretion flowing into the pharynx, through the gill pouches, to the exterior. On the exterior they help in the formation of the walla of the burrow by cementing together the particles of ooze. In this way the larva which inhabits ooze makes provisiion for a directed circulation of water SC within the ooze (Sloe page 312,r),,\ The ventral cylinder of glands produces, on the other hand, an acid secretIon rich in mucopolysaccharides whiéh serves as filtration mucons. Both eecretiona reach, with the help of the ciliated band, the passage of exit of the endostyle and from here leave. anteriorly by way of the pseudobranchial trough. '7he latter is divided in --• the region of the third to fourth branchial'areh into a re•'and li, branch 1 • -61- which in the vicinity of the pseudohyoid arch, runs dorso-laterally (rigs. 32, 3513, 38). Because of this arrangement, however, a twist in the begin- ning of the pharynx is formed from which the aecretion of the ventral glandular cylinder in the form of mucous sac can be exuded (Sterba, 1960a). This filter is similar to an aasembly line belt. It is stored posteriorly and collected at the oesophagus into a cords of nutrient. These mucous corda described by Kieckebusch, may be considered to be reinforcements of the pouch. The structures of the pharynx itself may be considered to be sup- porting and transporting mechanisms for the mucous pouch which must handle a volume of flowing water. The water taken in is forced through the mucous filter. Ideally it would filter and trickle through the sieve into the forechamber. In this way the mode of feeding of the lamprey larva corresponds completely, with that of the salpidae and ascidia (McGinitie, 1939; Werner, E. and B. 1954; Werner, 1959), and presumably with that of the acraniata (Schroll, 1959). The morphological differences existing between the groups named are second- ary adaptations in the senae of refinements or reductions which do not alter the principle of the mode of feeding. VIII. Organs of the Body Cavity The pharynx of the larva continues posteriorly to form the oesophagus p,301 which already lies in the body cavity. In the adults it is a primary of motabranchial oesophagus which -is prolonged by'an eplbranchial segment anteriorly as far as the velar apparatus (Fig. 30). The epibranchial oesophagus arises during metamorphosis from the branchoserial dorsal epithelial placodes (Kelbel, - 1925, ,1921).- The,coelomic gut of lampreys -62- runs a straight course. The nerrow metabranchial oesophagus covered with ciliated epitheligm proceeds along a dorsal fold of the liver (Fig. 40) and becomes united with the midgut at the level of the last third of the liver. In the larva the oesophagus is eomewhat invaginated at the midgut causing its lumen to bocomo a blind sack near the oesophagus. In metamorphosis this swelling becomes very deep dorsally so that the oesophagus and midgut run together for a short distance, and then laterally communicate. The gall duct empties into the gut in the vicinity of this junction. The mldgut, possessos no mesentery. The propia of the midgut is,broad on one side with the epithelium swelling out into a type of typhlosole (Fig. 39, 41). The position of this thickening is not uniform throughout the course of the gut for it rather follows a spiral line. The spiral fold contains the large vessels of the gut as well as numerous capillaries and nervous elements. The spiral fold is also a centre for the formation of blood., . Figure 39 ( Le Changes in the architecture of the gut and its. . volume (a) cross-section through the gut of a . larva just before metamorphosis. (b) cross- ,.. section during the feeding period of the adult.. (c) cross-section before the spawning period. . All cross-sections are through the beginning of . the midgut. • • . .The mucous epithelium of the midgut is emeoth in larva but in the adult it is in form of numerous strongly differentiated longitudinal folds. Atter the adult feeding period the structure of the mucous epithelium is again reduced (Fig. 39). The epithelium of the midgut. is. composed of narrow cylindrical cella and rod cuticular cella. In the most anterior segment -03• cells with granules of prozymogen as well as other cellular types occur, whiCh also extend further posteriorly (Maskell, 1930). The cells contain- ing granules of prozymogen are, according to Barrington (1937) supposed to excrete proteolytic enzymes and correspond to an.exocrinic pancreas. Lanzing, (1050) showed a cessation of proteolytic activity in Lampetra.fluviatis at the beginning of the spawning period. The endgut (74 the lampreys is short and fixed by a strong dorsal and ventral mesentery. The•ureter lies on the endgut and is finally received by the muscular and connective tissue coat. Just before the cloaca -two muscular straps arising from the walls of the coelom (nodus muscularis cloacalls) stirround the gut, the ureter.and coelomic duct (Fig. 10, see also page isoe). • • After the imaginal feeding period not only the function of the gut . ceases but also the tissue of the intestinal tissue fuses so that the gut shrinks to one tenth of its original cross-section (Fig. 39, see also page In addition the epithelium adheres to the region of the oesophagus. /hose phenomena are especially worthy of attention in so far as they occur in the same way at the same stage in parasitic and non■parasitic species. In the non-parasitic speciea these processes begin already during metamor- - phosia and in parasitic speciea-shortly si ter the cessation of fooding. During the spawning period both btotypres exhibit the same relations in the gut., The liver of lampreys is bound•anteriorly by the pericardium extending to just below the beginning of the midgut. The anterior end la attached ta The convoi ventral surface le fixed by a short mesohopaticus the peritoneum. ventrale. The Oesophagua, aomewhat imbedded runs over the concave dorsal - surface. The gall bladder is sunk anteriorly on the right side._:It -64- degenerates after metamorphosis and with it the ductus choledochus. For (15 the degeneration of the liver during the preapewning period see page 310. g . i For the changes that occur in the liver during the pre...spawning period see e 9 5 . page me. • 1 • 4ï • . An exocrine pancreas in thé form of an discrete organ is lacking in the lampreya. Tho function, according to Barrington (1945), ia taken over by certain cells in the epithelium of the gut.' On the other band numerous blindly closed follicles found at the transition between oesophagus and 11 midgut arising from the epithelium of the gut, havebeen designated as an endocrine pancreas (Boening, 1929; Barrington, 1936, 1942, 1945; Fig. 40), During metamorphosis la cranial, Intermediate and a cqudal pancreas, arises through deposition and reconstitution in the area of the ductus choledoehua. There is apparently a secretion of insulin (Barrington, 1942). See Doenigg (1920), Barrington (1945), and Sterba (1955 a,b), for the function of,the pancreas after metamorphosis. • • The i:tgans of Excretion of Lampreys Pronephros and opisthonophros are formed but the definite organ of excretion is the latter. The salage of the pronephroa of the lampreys is similar to that of the emphibia. The small canals of the pronephros arise 1 embryologically and are distinctly segmented when the embryo ta 4 - 5 mm. A Three to five anterior kidney canals are formed on both sides in larvae which begin as a large ciliated funnel in the coelom. After a circuitous course they join the primary ureter (Inukai, 1030). The venous glomeruli arising from the walla of the anterior renal canal are largely fused with one another to form a'large glomerulus. Zn therimagos the pronephros is -65- absorbed (wheeler, 1899). Tho development of the hind kidney begins in the 9 - 10 mm. larva caudally at a relatively great distance from the pronephros. The increase of tho caudal canals continues throughout the entire larval period (Wheeler, 1899). The small canals of the hind kidney have a connection with the ..,• coelom. They begin in a complex arterial glomerular complex and empty into the primary ureter. The primary ureter runs along the side of eaCh kidney. In sections the kidneys appear in the caudal halves of the coelom as band-like organs lying on the walls. The primary ureter is united to form an unpaired canal which, in the larvae, emptlea - into the cloacaeug:e-303); :5 • .E.R.I.:3".-iel..-°n.....21.11121e-1,•: . , • . Figure el . . . • .. . . -.. Lampetra'eAn.E.11. (B1.) . : Cross-section through -the liver region of a 138 mm. long sexually mature male. • Figure 41 j ' Lampetra planeri (Bi.) Cross-section through the hind region of 88 mm. long larvae.: Figure 42 Cross-section through the posterior region of a Lampetra neri female:just: before the spawning period. p.303 Figure 43 Lampetra planeri (Bi.) Frontal section through the thyroid. r- -66- In the imagoo the urinary canal -unites with the'coolomic duct. ' The ' • urogential papilla in the male grows out of the Cloaca during the apawning \, period. The Gonads Originally the gonads of lamproya are formed as a pair but early during the larval period both anlare fuse together. The band-like organ extends from eedee rre1er** ■ e) the liver region almost to the end of the coelom and is suspended by a relatively broad mesentery. The lampreys are, according to Okkelberg,(1921) juvenille hermaphrodites. Lubosch (1903) showed that in a population of young ammocoetes 26.6%, wore undifferentiated, 48.9% female and the 24.5% had hermaphroditic gonads. In the bisexual animals the germinal glands dominate the growth of oocytes or testes. Not infrequently follicles con- taining mature sexual colle of the opposite sex occur in grown animals. The ovary and testes are made up of follicles. The sexual products ripou on the relationship between the time of maturation and successively. Work . life cycle bas been carried out especially by Weissenberg (1927). In parasitic species the development of the gonade does not begin until the end of the imaginal feeding period. In non-parasitic species it begins just after metamorphosis at the latest. According to Kamer and Schreurs (1059) and Lansing (1959), the gonadotropic hormones are manufactured in the pro-adenohypophysis. The relative weight of gonads to total body weight increases in Lampetra fluviatilis (Lansing, 1959) during the anadromous ' spawning migration from 1.4 to 6 (testis) and 3.9 to 13.9 (ovary). The ripe gonads fill up almost the entire body cavity (Pig. 43). The emptying of the products is achieved through the coelom. From thereth0 alakual -67‘ producta are conducted to the outside by a coolomic duct (see above). Ecg colis: The ovum of lampreys hap been investigated especially in recent times. (Yamomoto 1944, 1952; Rogozina, 1956; Schalumowitsch, 1956; , Chubareva, 1957; Lanzing, 1959; Schwarz, 1959) The oocytes display a large nucleolus lying within a spherical nucleus during the whole phase of egg formation. The yolk platelets arise close to the vicinity of the nucleus but then fill up the entire plasma. Peripheral vacuoles are formed. The, , yak of the nucleus is very diatinet end the cortical membrane is double- .- layered. Around the follicular epithelium is a layer of connective tissue. Tho mature eggs .have the form of an ellipsoid of rotation. .7be nucleus of the eggs lies in the region of the animal pole--a region which is in several species more or less free of yolk.' Some authors state that the ovum has no micropyle. (Horfort, 1901; Lubosch, 1904; 01aeaner, 1910; Lanzing, 1959; Yqmamoto, 1953; and others) Others, state the contrary, (Calberla, 1878 and Veit, 1957) The eggs of lampreys have no pigment and their bright yellow coler is caused by the yolk. The egg.aize varies with species. The p.304 number of eggs produced is also variable (see,table on page 303). . A Sperm cells: Not very muCh is known:about the sperm cells of lampreys. According to Ballowitz (1905) the head of, the, spermatozoa of 3 leme_Ire fluviatilis ia very irregular. Sperm having heads shaped like apple seeds or rods predominate. Especially characteristic is a long anterior bristle on the head. • A collar is said to be lacking.. The flagellum is uniformly thick. The expressed mut has a whitish colour. According to Rothschild the sperm of lampreys are viable for several hours under certain physiological.conditions. Montlenti and Schartau (1942) have worked on the substances necessary for fertilization. Insemination and fertilization itself has been studied recently. (ex. Rothschild, 1958; •• • Chubareva, 1987)\ IX. Hormone System of Lampreya Tho classical endocrine organs of the gnathostomes are represented in ,;• the cyclostomes mostly in primitive forms. Thus; cyclostomes assume importance when the development of these organs is being considered. TO a lesser extent, the Myxinidae are also important. In lerval develop- ment of the Petromyzontidae not cmly can the genesis of the endocrine organs be observed and physiological questions posed, but it is possible to analyze the physiological conditions for the development of the whole system (Sterba, 1953-60). Ne doubt in phylogenesie a causal relationship exists between the increase, diversity and intensity of metabolism, and the differentiation and integration of the hormone systems. Firstly,. . increased metabolism makes a better' coordination and regulation more necessary. • It is only from this point of view that it is understandable why in the Petromyzontida such a Change occurs in the hormone system:with metamor- -e phosis. Tho development of a thyreid during metamca4phosiscannot only be ' considered as a process in the sense of the'biogénetic rule, since this merely corresponds to the development Of the form out of the endostyle. The metamorphosis Of the endostyle is much more than this. It is a process closely associated with the change in metabolism and the extension of the variety of metabolism. These processes, however, are as Characteristic p.305 ' for the segment of the PhylogénY of chordates'in which a filterfeeder' ' becomes an active predator, as-it. iifor'the metamorphosis of 'lampreys. -69- When ono is ready to consider the biogenetic rule in this light, some . order of the sum total of the processes can generally be made, . In spite of numoroue investigations our knowledge on the inner secre- tiona of the lampreys la very aleetchy, 7he hietological relationehips of the pituitary glands, hypophyuis and eplphyvis us well au essential observa tions on the neuro-ssecretions of lamprey have already been dealt with on page 285.. At this place will be discussed the•work oe Daman (1033). He wau able to produce a premature ripening of the sexual eharacteristics by anterior pituitary extracte and by .pregnant womene a urine. He was, however, unable to duplicate these reuults in 1950. According to Lanzing the active constituent o (»rum and chorlongonadotropin , Pregnyl, Gestyl), are able to elicit sexual characteristics in the river lampreys several' weeks before they.occurred in a control group. Lanzing concernedpimself•also with osmoregulation. The thyroid of lampreys arises during metamorphosis from specialized • cells of the endostyle. . The thyroid follicles lie between the musculature ed the piston of the tongue und the two branches of the ventral branchial types of follicles are recognizable. The . epithelium arteries (Pig. 43). Two is partly flagellated. (Marine, 1913; Stokes, 1939; Leach , 1946; Sterba, 1903; Lanzing„ 1059) Substances similar to thyroxin were firot discovered . in the lamprey thyroid by Horton (1934) by applyinithe extract in .the "tadpole test." Fontaine end bis co-workers (1952) Showed the presence of thyroxin in the thyroid by radioautographs. .AcCording tu Leloup this hormone: is slowly . , . produced and secreted.' . . • Of especial intereet is the function of the lamprey endostyle.with ••• -70- regard to the question whether thyroxin is formed here. Corbman and Creager (1942), Olivereau (1955), Gorbman, (1955), were able to demonstrate by radioautographs the presence in the endostyle of organically bound iodine. On the other hand, it bas not yet been possible to attain a positive "tad- pole test." Metamorphosis is controlled directly by the hypophysis. Extir- pation of the endostyle has no effect on metamorphosis (Sterba, 1953). Ammocoetes whdeh are held in a thyroxin or in an iodine solution display no change in the time when metamorphosis ends. According to Knowles (1941) a reduction iz the cells of the cylindrical glands of the endostyle is observed aster injections of mammalian thyreotropin. Young and Bellerby, on the contrary, were unable to obtain metamorphosis by injections of mammalian anterior pituitary. According to , Kamer and 8chreurs (1959) the hypophysis diaplays intense activity at the beginning of metamorphosis. Numerous works have been dedicated to the homology of the endostyle of lampreys, tunicates and acraniates (Muller, 1873; Dohrn, 1886; Gorbman and Creaser, 1942; Barrington and Franchi, 1956, and others). The production of insulin in the pancreatic follicles of lamprey (see page 002) was aPParently ahown by Barrington (1936, 1942 * 1945), and confirmed histo- chemically by Ermisch. In non-parasitic species, the production of insulin is inhibited after matamorphosia by reciprocal action of the adrenalin system and in parasitic specien this occurs during the early spawning phase. The adrenal and interrenal system of lampreys has been depicted as islands of cells situated along the great dorsal vesscla from the pharynx to the caudal region (Glacomini, 1902; Gaskell, 1912; 8terba, 1955a). p.: 306 During metamorphosis the activity of both systems increases. The adrenal system presumably controls the 'formation of depot fat during the pro-spawning and spawning period. By injections of ACTH, a premature increase of • adrenal tissue is elicited. The adrenal system playe a role in the elicit-. ing of metamorphosis which is not yet known (5terba, 1955 ab). X. Miscellaneous Chromosome Number and Hybridization The only information on the chromosome number of lampreys is given by Lanzing (1959). "It appeared that the haploid number of chromosomes amounts to about 60, the diploid number thus being about 120." Hybridization experiments were carried out by Weissenberg (1925) and Cotronei (1942). Weissenberg observed in reciprocal crossings in both directions of LempeIni fluviatilis and Lampetra planeri that young larvae were producod. In the primitive and embryonal development no differences in the control could be shown. On the other band variable results were obtained with reciprocal crosses of Lampetra fluviatilisx Petromyzon marinus according to Cotronei (1942). In the crossing of L. fluviatilis (female) with P. marinus (male) development only proceeded as far as the blastula, and of the total number of eggs only 1% developed. Eggs of P..marinue which were fertilized with sperm of L. fluviatilis attained, on the other hand, in comparison to the control, gastrulation in greater number without the characteristic distortion. According to Cotronei (1942) these results confirm the close relationship between L. fluviatilis and L. planeri. Nooteny Zmnandrea observed neotenous larvae (1956 a, 1957) in Lampetra zanandreai. Out of 200 larvae in a biotope, 12 displayed well developed ovaries which, -72- in part, contained mature ovae. In one larva even secondary sexual char- acteristics were present. Sexual maturity in larvae represents the highest 'level Of that process "the limitation of the migratory drive"..-elimination of this drive, shortening of the imaginal feeding.period, and finally elimination of the imaginal feeding period also page /C),1 'It is . worthy of note in this connection'that even when . the.thyroid is'lacking the maturation of the gonada takes place. Capabilities of Regeneration In experiments on regeneration in Lampetra planori Zanandrea reports • his findings (1956b). °Playa's work bas already been repérted on page 1 81 . Parasitic Fauna of Lampreys Little 1.8 known about the parasites of lampreys. in general all that can be said that an encysted nematode'occurs in the wall of the gut which later penetrates the body cavity and feeds on the Seicells. 'Zglite . (1958) writes that this parasite is Cistidicaln farionie., C. "s‘cermGENy. ,\ BIOLOGY, AND OECOLOGY OF THE LAMPREYS Among the chordates the lampreys have the most varied life cycle with respect to morphological, physiological and paychological characters. They display a characteristic stee-like development which makes possible a definite division of the segments of the life cycle. In all lampreys of the northern hemisphere that segment of the life cycle up to metamorphosis is similar but the segment following this process is profoundly different among species. When neoteny occurs in some species the life cycle is short• ened und eventually a whole segment of the life cycle is suppressed. The distinguishable biotypes have developed independently oe each other in Europo $ Northern and eastern Asia und in North America. As a rule two biotypes occur in any area of distribution--"the paired species" • 14 of Zanaudrea (see page 2G5). In Europe P. marinus and Lampetra fluvlatilis possess a complots life cycle. In these species the following phases of the life cycle may be distinguished-m.embryonal development, larval develop- ment, metamorphosis, catadromous migration, imaginal feeding period, anadromous spawning migration, spawning and natural death (fig. 44).. Figure 44 Diagram of the life cycles of various species -' of lampreys. The plan should especially demon• . strate the abbreviation of the segments of the '• life cycle following metamorphosis. For the ,. imaginai period the area have the following meanings: densely stippled" Catudromoua migration - lightly otippled . Feeding period . heavily shaded f - horizoneally :Anadromoue migration :H • lightly shaded -- . horizontally : phase black Spawning -74«, A limiting pf the migration from the biotope or the complete suppress... sion of the migratery instinct results in a "stationary" freshwater form. Ex. Eudontomyzon denfordi. • The reduction of migration is highly correlated with a ahortening of the parasitic feeding period which, in a "stationary" freshwater form, may be completly lacking. • Such non-parasitic forms are represented in Central Europe by, for . example, Lampetra planeri und Lampetra aanandreal (Fig. 44). Since the . lampreys of Europe, Asia and North America are fully independent.of each • other, but have the same developmental tendencies, the assumption is not far from wrong that the matter is one of pre-adaptation. I...... 111 ILLIIii.eallememlel_Dentku...2. • The primitive development of the lamprey ogee is reminiscient in many respects to the corresponding processes in the amphibian egg. The resesee 4 blance is due to the same content of yolk and a similar topography of the presumptive areas of organ formation. A very good summary of the most important details on the primitive and embryological development its pro.. vided by Pasteels (1958). Important, recent invoatigations are found in papers by Weissenberg (1936, 1936a, b); leasteela (1939); Veit, O. (1039); Tschekanowskaia (1941), and Vett, K. (1957). The ova and spermatozoa are discuseed on page SUM. 1 The sperm enters; the ovum through the micropyle at the animal pole (Voit, X., 1957). The plasma of the pole contracts strongly after fertill... zation but still retains ite connection with the micropyle region through a cord of plasma. The polar bodies are formed first eali after -75- fertilization. The egg, which is again aphorical, divides totally into moquai parts (see Fig. 45). Successive divisions of the blastomere stop after the fourth division. The many-layered blastula bas a large coelom • lying somewhat excentrically. The blastopore arises beneath a small - • mound and becomes later the dorsal lip on the ventre-caudal aide of the blastula. Only the ventral lip of the blastopore ia evident. The tube■like gastrocoel displaces completely the hollows of segmentation. The mesoderm . arises not as a unit, but somites and coelom are formed, separated in time • and space (Voit, 0. 1939). In the cranial region a true enterocoele is' said to be formed' (Weissenberg, 1934; 'lait, O., 1939). — Even the formation of the thords is completely independent. ' • After neurulation a cranial fold appears opposite the blastopore and is•subsequently markedly extendeeforward. This structure give the lamprey I • embryo its characteristic retort-like sbape (Fig. 45).The:anla n. of tx,,A,4,,(» Figure 45 Larapetraplaneri (01.) . Above left, four cell stage. Above right, Retort stage. Delow, recently hatched embryos.' the systeme are, at the time of hatehing, still rather incomplete. The caudal segment of the yolk sac, for example, lies completely open, the gill pbuchea are either not yet open or just beginning to open from the front to the back. The edge of the fins are not yet present and the . stomadaeum is not yet open. In the course of 8 i* IC dayi embryonal develop- ment is completed to be followed by.the,period.of larval development. The lamprey embryo begins to display rotatory movements in the egg capsule shortly after neurulation (Sterba, 1953). Later lateral movements of the prolonged head region may also be observed. The egg capsule is ruptured by the head in hatching. p.309 Pilotti (1941 a,b) showed, by centrifuging eggs of lepere fluviatilis, that segmentation ceases. However e the beginning of segmentation takes place by invagination without the formation of celle. According to Noleth (1965, 1956) the neural crest of cyclostomes corresponds to the neural crest of gnathostomes. On the origin of the melanophores Daneel (1057) luta not established anything definitely from bis purely morphological investigations. , • The Lerval Period The biology of the ammocoetes of Central Europe is very eimilar. The bright yellow eggs are deposited on the sandy stream bettom during the spawning net and the sand etirred up thus affording some pro- l( ; tection from predators (see 432g). Hatching °acute; after 0 • 20 days, /\ depending on temperature, and the embryos, coloured yellow from yolk sub- stance, complete their development between the grains of sand. During this period their length is increased by about one third. After the yolk bas been completely used up the transparent, young larvae, about 8 • 9 mm. in length, leave the protective sand, partly swimming and partly being wafted by water currents. They settle in calm stretches of the brook and burrow in the bottom (Abakumow, 1957). Not an inconsiderable portion fall prey to young fish. Investigations on the intestinal contents of young trout, -77- 1110 "schmerlo" and sticklebacks, 3 4 weeks after the spawning period of brook lamprey, show that young larvae form almost excluaively their food. Applegate (1950), Sterba (1953), and Schroll (1059), have mainly car•P ried out investigations on the biology of ammocoetes. The behaviour of lamprey larvae is determined by their mode of feeding. Their utilization of the oecological relations of ilowing.waters is imam-. ' /ugly efficient. The densest larval populations in C ntral Europe are found in peaceful, stretchog of streamg. An example ia an impounded section possessing gandy deposits and loose marginal growth. The preference for these locations is understandable when their filter feeding mode of life Jo taken Into consider.- ation. Doubtlesely the production and concentration of micro-plancton is the greatest consideration and provides the boat nutrition of the larvae. 11, There are, however, other good reasons for thla tavoured site. Ii the upecial position of the larva at the surface of the mud and with respect 11 to the direction of water flow is conaidered (see page 311), then it be-. comes evident that this not only permits a constant stream of micremorgan- isms but also points the mouth In the direction of their densest flow. p.310 Uowever, one cannot go far wrong in assuming that the denseat growth of micro-organisms occurs at the surface of the mud, The lamprey larvae seek out stretches of the creek which are not only ideally auited for the growth of their food but also provides a good, protective substrate and permits the most efficient use of their filter apparatus. The concentration of ammocoetes in locations of the brook possessing a characteristic grouping of oecological factors has also been noted by Baxter (1957). He showed lib els° that, once a bed has been chosen. the larvae remain there even during - periods of high and low water, tho larve, in contrait to the imago» may. be designated as "steno-oocological." A characteristic example of the distribution of ammocoetes in a limited regions of an investigated waterahed is preeented by Schroll (1959). (Fig. 46). Figure 46 Stations at which ammocoetos were . collected in Steirmark (after Schroll). The following details of the micro-environment of ammocoetem are aloo worthy of notice. ' • - 1) Almost all populations are found in a region of the "beta mesoprobic zone" (Schroll, 1959). . • . 2) The preferred deposits of ooze consist of fine alluvial and diluvial material containing a moderate percentage oe organic substances (Sterba, 1953; Sehroll, 1959). 11i• Characteristic "AufwuChs" consists of coating-of diatoms. • • 3) The average current velocity at a depth of 25 cm. where colonies of • nmmocoetes in Steirmark are found ameunts to 40 cm. per second (Schroll, 1959). Using similar methods Sterba found that -the velocity directly over the surface is eosentially slower in brooks in the Flaeming region. Since similar disturbance» in streams flowing through geologically identical areas lead to similar sediments, it is to be expected that there would be a 'close connection between the sediments and the correeponding water velomi,. cities prevailing where the larvee are found. 4) Ammocoete populations,almost without exception, are limited to 1. -79- calcium poor, slightly acid waters, i.e., in brooks arising in archaic rocks or variegated sandstone. The chemical eharacteristics of these . brooks is aimilar in various iireaa of distribution. • 5) Thu preferred temperature for ammocootes is approximately C. ' They are able to acclimate to the freezing point of water and acclimation to 200 C. is possible. Ammocoetes, on the other hand are not unusually sensitive to Iow oxygen concentrations. At the corresponding temperatures; and under natural conditions no increase in respiration is noted when the oxygen falls to low levels. The following values; for the concentration of •dissolved oxygen were measured in the sediments where ammocoetes were collected (Sterba, 1953): • • Watery ooze at the 15 cm. depth '• 9.9 mg/I.0 2 Watery ooze at t1ie- 5 cm. depth 2.0 mg/1.02 Open water over the bode 10 15 mg/1.02 > (Temperature of ooze and water....10.50 C.) 51 p 't e For special details of the respiration of larvae, see )1\ esete. A s 0) According to Schroll (1059) the habitat of populations of larvae is dependent on the inteneity of light. Diffuse light is always preferred. 11 . It has been indicated on page eo9 that the larvae not cmly seek pro- tection in the substrate but also choose it because it permits them to use their filter-feeding apparetua efficiently. Figure 47 Position of ammocoetes of Lampetra planer/ in the mud. . The ammocoetea lie in the mud such that their anterior end protrudes 111, into the free Water and the Mouth opening directed into: the current -80- (Fig. 47). This position ia made possible by the formation of a very fragile tube which not only permits a circulation of water in the tube but also allows the animal to quickly withdraw into the burrow when danger approaches. The cementing of the surrounding particles of ooze to form a p.312 tube is achieved presumably by the secretion of the endostyle. The secretion is forced through the gill alita by the water of expiration and to it is added dermal slime (Sterba, 1953). The form of tube under exper- imental conditions and apparently also in the stream i ~ not uniform. Schroll, 1959, has obeerved, numeroua cross passages in addition to an ' exit and entrance: I have only in part found such eross passages in my own investigations . As a rule the opening of the burrow is inclined at an angle of 60 - 70° with the surface of the mud in the direction opposite that of the current flow. With age this angle becomes steeper. The entrance may be widened in the form of a filter. The peculiar orientation of the entrance is dependent upon the position of the filter-feeding larva (Fig. 47). The ammocoete filter food to some extent, in a steep dorsal position in which the mouth opening ia directed against the currant (Applegate, 1950), Non- filtering larvae pull themselves into their burrows. The entrance is thon and there must be reopened from the interior of the hurrow usually filled or rebuilt anew at another site. The lower portions; of the tube are not fixod but formed in a variety of ways. The larvae change position fre• quently and shove their way snako-aike through the send. The very mobile anterior end is shaped like a cone and then rounded again. The new core P nection with the water surface ls opened from below.. , 81- Tho water la pro-screened by the oral cirri and filtered in the pharynx (see P. 290ff). Leaving by the gill slits, it flows to the dorsal aide of the larva anteriorly again and thence out through the entrance of the burrow. Where present the water also leaves by the exita of burrows. The ammocoetes seldom leave the mud and, as a rule, only at night. Schroll (1959) was unable to detect a rhythm in the departures of larvae from the mud. The ammocootes retrace quite quickly into their burrows when sensing oven slight mechanical disturbances or by sudden changes ln light intensity. The depth to which they retreat depends . upon the, size of the larva. Approx., imate values for Lampetra planeri sie suemerized in the following table: 'Length of Larva, yepth of retreat - ' ' • 20 up to 50 - mm. 50m. 'up 'to 80 em. loo mm. up'to 150 me.' 150 ram. 'up'to 180 mm. - Schroll obtained similar reaults,for the' larvae el Eudontomyzon danfordi viadykovi. • • • Ammocoetes which have either been collected Or shocked out of the mud attempt at once to reburrow. The point of the head is inserted in the mud and, by . means of vigourous motions, the larva'thruats its body about three fifths in. With the aid of creeping movements the larva :complets ita A burrowing and lies completely covered (Sawyer, lebs). • - • Of interest concerning the peried which .the larvae spend in the mud are the oxygen needs of these erganiSma. In.general the . larvae of lampreys -82- are considered to be sensitive to low levels of oxygen, an assumption which q7 e is refuted by observations made under abnormal conditions (see p-t, -299). /1"" ' In the natural environment the need for oxygen for the following reason . - must be small: . • fl 1) The muscular aCtivity ià greatly reduced since active movement « hardly takes place. 2) The total metabolism Of larvae is very low. This exPeCtation is in good « agreement with the observation that . even under the unfavourable oxygen relations prevailing in the ooze the ventilatorY Movements are ' ; 'very groatly reduced. (Tàble)' ' !. 'NUmber of Contractions Beats of ., of the pharynx . • velum/min. Contractions/minute - • .1.040•101man. . . . . : . . ' 48 : ' • : .'. .• •' 63 ' . ' • " in water . .27. . . . , • :. 38 . . ... 3 minutes aster burrowing; - ' ' - -'''' ''-• ' ' - — -- 'diminished 15 .: • 28 . :. .6 minutes atter burrowing - . .. . , . - greatly diminished. 8 .. , -12. ' 8 minutes aerft burrowing • hardly noticeable. , 5 . .8 . : . 10 minutes after; hardly noticeable. 3-5 4. after a prolonged experiment • . .ot six days. le...”•;••••■•••**,••••••••■••~4.1...... *** The water movement in the pharynx during filtering is caused partially passive1y by the movement of water in the brook and partly by the movement of the rows Of cilia. This regular movement of water makes filtration possible with the aid of a continuous mucous filter (see page'800). In contrast to the above swimming animale and those held under adverse temperature conditions or disturbed'in some way, have a high oxygen demand. • ! • • -83- The Characteristic ventilatory movements due to pulsations of the velum and contractions of the pharynx lead to a rhythmic, highly accelerated flushing out of the pharynx. The mucous filter is not formed. As in many cases a characteristic difference exists between the behaviour under oxperimentaland natural conditions. . Since the mode of feeding of larvae bas already.been discussed in _- detail (see p4 299Zf) the type Md composition of the food will only be i\ . discussed here. The main type of food consists of diatoms and detritue (Storba, 1953). The morphological arrangement of the pharynx give the impression that all particles are indiscriminately filtered passing through the oral screen. Against this is the viewpoint of Schroll (1957, 1059) based on experiments with ammocoetes of the Eteirmark region and Italy which indicated that selective filtration occurs. The type of selection depends on the stage of the larvae. Under natural conditions the stomach in summer is said to çontain almost exclusively diatoms. In winter considerable detritus is preaent... SehrolI presumes that certain species of diatoms are agglutinated by the bands of mucous. Controlled experiments on larvae of Lampetra planer/ from the Ers mountains of middle Thueringia and Flaeming gave no proof of a selective filtration. Aleo in no instance and at no season could just diatoms be identified. Always us the .daatostfraction in the gut was substantially higher than the diatom fraction. A selective uptake of food in the sense of - Sehroll e s theory does not take place in the light of my own experience. The possibility exists, however, on the other hand, that the fineness of the oral filter decreases with age (a purely mechanical propert y) and the size of the particlea which are pro-sorted ia . éhanged. *A pure conaumption of dlatoma -84- is controlled only by the location of the larva.' The growth of the larvae and the larval period is only known, un- tortunately, for a tow species. Lubosch (1002), for Lampetra planeri already stated values, which have boon since many times confirmed. According to these metamorphosis . occurs in the year x 2 whore x is the time of hatching (May). In ' individual cases the tollowing growth .and time . t#14. is valid. . p.314 Year ' Month ' Average length Itemarks Ilve.e..• ••••••••■••••••• •••■•...... • e Ill-V embryonal development 0 . V. "(5x — . V-VI , ' ,'-, 10-20 mm. V - 40-50 mm. - • sex., 41 a .1e,i2 .. • . - V „ . .•. ,. . ;'," i . • 85-10û rm. i .. .* ::....».:': • • • ' ; a L..' • • x,43 V 120-180 x,43 . 130-180mm. ',.. .i.s. '..: metamorphosis' Ox>44 IV-V .... 120..-160 mm. .. spawning . - to .. .. ffw4 V-VI ''' - 120-160 mcia. - ;; .;; ;:' '.deatb.; • The ammocoetes of Larapotra tluviatilis agree completely in this respect 'tta the larvae of Lampetra planeri.: H No exact observations exist- on the length eflarval 34f. of the son (Petromyzon marinas marinus):, Aside from determinations of "from lamprey tour to five years of development," shorter,times.are;given.. 7ho'sane, •; - statement applies te. the Danube lamprey., H 1 ,H The ammocoetes have few enemies.. ewimming larvaeare easily. uappod . up by salmon:Ws:and. accerdingto çheppule (1930),, , they,are esp.ettacked - . by . crayfish. Metamorphosia . ..• • In, all species of.lampreys pf the northern. hemisphere the phystologleal -85- and morphological transformations in metamorphosis are almost the same. The ammocoates of all species are about the same size at the beginning of metamorphosis. Hotamorphosis is elicited directly by the hypophysis (Sterba 1953; Olivereau, 1958), in which the adrenal system plays a part not yet known. The hormone of metamorphosis (thyreotropo H) is produced in the mesoadonohypophysis (Kamer and Sabreurs, 1959; Lanzing, 1959). 4 There is no clear answer to the question whether the time of metamor- phosis is determined genetically or brought about by the state of nutrition . of metamorphosed larvae suggests a genetic The often indistinguishable size control. On the other hand, it has been possible to hold individual larvae five years by starvation (Sterba, 1953). Recent investigations suggest 1 that a critical phase is undergone during the larval period which determines the time of occurrence of the metamorphosis. Almost no evidence exista on the behaviour during metamorphosis. It is only known that the larvae cease feeding shortly before metamorphosis. It was observed in Lampetra' planeri that metamorphosing larvate . left the mud shortly atter transfare. ation to bide under stones, water 'plants, and under the banks of the stream. Our knowledge on the changes of the processes of regulation accompany-. ing morphological and phyaiological changes are well known. . since the metamorphosis of single organ systems is duScussed in A A section 5, a list of additional points will be presented here supplementing general characteristics. Hetamorphosis begins, as a rule, in European species during the period July • August. A larva ready to undergo this.process cease feeding and withdraw deeper into the mud. .The oral .tentaales shorten , and the mouth' . opening becomes a narrow slit. Later it redevelops to a circular sucking' ' funnel (Fig. 48). First of all the teeth break through. The eyes slowly , and, at the beginning of metamorphosis, contain appear directly under the skin dark irises. Those acquire a silvery lustre by the deposition of guanophores. Tee distinct dorsal fins and a caudal fin arise from the uniform fin fold P.315 of the larva. The dirty yellow coloration and pattern of spots have already receded during the first third of metamorphosis. The back becomes darker and the belly merges into a luatrous.silvery from a bright eolour to a pure white.: The body, especially in the branchial region becomes shorter. , OE, In this way the gill chamber becomes steeper(;) (See A. 29q), The transformer- . tions mentioned above require 2 - 3 months with alterations in the inner organ systems requiring, as a rule, about 3 - 4 months. The following organs show characteristic morphological and physiological changes. The head of the tongue develops from the floor of the oral cavity 9r -294). The larval visceral musculature is partly broken down and partly Pem3 A . rebuilt to form the piston apparatus and the pharyngeal pump.' Some muscles of this system arise anewtk (pee .pe 288 ) The flap-like velum, a valve of A A the larval pharynx, is greatly altered serving now as a Valve as well as a 1-11 sorting device (p,‘1; 224). ' Pe'Je Figure 48 Transformation of the larval mouth , . during metamorphosis. ' (elaborated from gaenschea • Tho anlage of the paired salivary glands deVelop - tres tbe -floor of'» - • I . •pci_c•e- • the mouth of the larva A v • • -87- Tho transition from the larval "weir gut" to the oesophagus is closed. A solid extension develops out of the dorsal placodes of the nutritive tube extending to the velum and finally containing it. The larval weir gut be- comes a pharynx. The elements of the gut arrange themselves parallel to e, the direction of flow of the inhaled water (9 2e7). The ondostyle recedes, and certain cells of the endostyle are grouped toe 90 to form thyroid follicles (see eoe). The taste buds in the branchial sac ero absorbed. The gall bladder becomes smaller and disappeara completely, `3* (4) page 302e)7‘ The venal sinuses in the head and pharyngeal regions are multiplied. 4q • p‘k The insular pancreatic tissue is also increasedeyee 80.481e. The adrenal and interranal tissues are enlarged C. eon. The secretion pAcc. A .. stored in the neuropypophysis during the larval period is release« qee A.-206). The intensity of metabolism increases and this is accompanied by Per'J e-4‘ a corresponding rise in oxygen consumption. In species lacking the migratory instinct and especially the imaginal feeding period (for example, Lampetra planeri and zanandreai) the following variations may be observed. The attenuated oesophagus remains blocked histologically at several points. The,mid gut degenerates(I) Maturation of the gonads 'begine Species with a complote life cycle migrate down to the sea after meta- morphosis (Petromyzon nu:minus, Lampetria fluviatilis). Species lacking a migratory instinct.begin immediately atter metamorphosis te teed parasitiCally. p.316 -SO- (Eudontomyzon danfordi danfordi) Species lacking the migratory instinct . and imaginal parasitic period over winter after metamorphosis under stones and roots and enter the spawning phase,tho following spring (Lampetre pliner4 Eudentomyzon danfordi,ealem9. , . •V. Catadromous Migration Practically no observations have been made on catadromous migration of, lampreys. Even the question whother . the animalmigrates at once or after some time after metamorphosis cannot be anewered with certainty. The same applies to the beginning of the feeding period. As a rule it is assumed. the feeding period begins first of all in brookiet water, an assumption that which presupposes that the entire .catadromous migration is supplied with energy from stored reserves, having their origin in the larval.period. Lanzing (1959), allowed that the stored fat of anadromous lamprey have a 111, fraction characteristic of freshwater fish. It is poosible that this was layed down during the'catadromous Migration. 'According to Bahr (1952), metamorphosing individuals appear directly downstream in .the estuary of the 9ste and at .Brunebuottel (in the lower Elbe) during April and May. V. The Parasitic Feeding' Period Petromyzon marinus marinus is found during the feeding period even, according to the chance catches of deep ses fishermen, far out at ses, The 'vertical distribution from 1 - 500 metres.aleo is noteworthy. • ' In contrast to this Lampetra fluviatilis is found predominantly in coast.» al areas. According to Bahr (1952), the riverlamprey is. a typical_brackish -89- gl› Water form, which, nt least in the estuary of the Elbe, does not penetrate into water of a salt content loss than 20%. This determination is based, . among other things, on the observation that the denaity. of animals; of all . • sizes and classes caught in the direction of Elbe lightship 2 (25%),. Elbe lightship 3 (18 - 10%), und the Elbe estuary at Cuxhaven (10 - 15%) quickly increases. The river lamprey has only a limited distribution determined by . the salinity and is found in the region of the Elbe estuary and the cor» responding estuaries of other rivera flowing into the North Sea. Bahr (1952)#/derives an extremely interesting theory from this relationship. • The reason why this species is not caught in large numbers in the Baltic Sea is due to the lack of a critical border of salinity. Xn this sea the area of distribution is large and the numbers of lamprey.are spread out. That the space factor plays an important role in the increase is.clearly shown by 1 2 1 the relations of lamprey ln North America (se. page -a41), " • In contrast to this Zanandrea (1959b) found river lamprey only in the gulf of Gaeta in sea water up to 15 hm. close to the coast, i.e., not in brackish water. The vertical distribution was 1 7 50 metres. Finally, .. in this connection it is necessareto mention that Caspiomyzon wagneri can withstand salt concentrations up to 150 0/00. , . . The lampreys during the feeding ' period in the sea live parasitically on fish flesh and fish blood. No investigations ,have been carOed out on the species of fish that .,. are attacked by ace lamprey. Wounds caused by lampreys have been observed. on bony fish, sharks and whales.. The river lamprey according to Bahr (1933, 1952) and Eglite (1955): attaek : especially - the Clupedae Gadus iorrhua -90- Iz (2, gland Pleuronectidao (see also ef340)., Robertson (1875) cites Coregonus • 5 clupeoldes a species indeed confined to English freshwaters. River lampreys are also attacked (Bahr, 1952). Salmonlds, according to Nikolski, are the prime victims of the North American species, Lampetra .japonica pponica parasitizes chiefly Cements p.317 eperlanus dentex, • The manner in which wounding occurs differs in the various species which are parasitized (for detaila see yo,z e40. Before the feeding act begins • P "A the lamprey, now tightly sucked on the fish, slidee along its surface to . find a favourable spot (Shetter, 1949; Bahr, 1952). With the mechanical destruction of the tissues lampredin io secreted from the salivary , glands , and acts both as an anticoagulant and a haemolytic (Lennon, 1954). The parasitized fish bleed to death or succumb to secondary wo4d ,infections. • S91o1egnia peresitica, Leptomitus lacteus) The method of feeding of the Danube lamprey, 11•12rAnlzony_ danfordi is not known. , According to Bahr (1933, 1952) the part of the fish eaten by Lampetra fluviatilis extends into the musculature. %rounds in the coolers apparently ,do not occur (see also a little further in the text),, Long pauses occur f between feeding sessions (Gage, 1923; Bahr, 1933). . Bahr has renewed the question whether river lamprey are able to con- sume other kinds of food. In some instances parte of algae and small 1 crustaceans may be detected in the gut in addition.to the,remains of,fish, , muscle. Bahr explains such contents in this manner. Algae are paesively •drawn into the gut when the animal fastana,itaelf to,a stone. The taking up ' -91- of small organiams is achieved through the gill openings partly actively ' 7-- and partly passively. Such a method of feeding ia not possible because of the construction of the lamprey's body. It is alse assumed that the small prey organisms contained in the host fish are taken up incidentally when the lamprey opens up the coelom. It is conceivable that lamprey woulepenetrate beyond the muscle layers when feeding.' • VI. Spawning Mieration For all species with normal life cycles the period of anadromous migration follows the feeding period. Species; with abbreviated life cycles, i.e., parasitic period absent, imitate in part a spawning migra- tion in a very limited fora. Anadromoue species; come from the North and Baltic Seas and even from the Mediterranean, to Central Europe. Especially thorough investigations on spawning migrations have been carried out recently by Lanzing (1059) onliampetra fluviatills. In general it J.Q assumed that the river lamprey after a sojourn of ' 15 to 24 months ln brackish and sas water, irreversibly ceases to teed (Loennberg, 1803; Weissenberg, 1925; Bahr, 1952), and begin to ascend rivers. All life processes after the feeding period are supplied with energy'from atored 'reserves, notably fat.' (Synchrony. after Mislin, The seasonal beginning of migration as well as the . duration Of the migration in the rivers locally differle because of unknown »Boone. In A the region of the estuary of the Muas the migration begins, according to tanzing, in July and continue until February. In the eituaries of the • -02- Voser and the Elbe'tho lampreyn appear later. Sven in tho Nova the first lamprey is obeerved in lato aummor. In the oatuarloa'of the Viatula and the Memel as a rule it can occur ln late autumn. • In the tributnry atreama of.tho Gulf of Bothnia, Nerve, Nova, and Luga tho migration occura in two 'gamete, L.O., on autumn and spring migrations are recognizable. This obaervation originally gave (rtee to the assumption that aeaaonal races oecur. This assumption woe queationed by Abakumov p.318 (1053s), to whom we are • ndebted for a aorioa of interesting atudies on this subject. Tho di-phasic migration Is determined climatically in this region. The river lampreys gather in autumn in front of the river estuaries. From Lore la portion migrate up the rivers and the remainder overwintor in tho ostunry to later migrate th ofollowing spring. Both migratory groups. slo in the spring on the apayning reticle. Similar relations are pro- Oaumably the cauao et tho locally different beginning,and the subsequent variable durations of the migratory period. aven the tan length and weight of migrating river lampreys, au the following examples shew, are locally different. Length in mm. Weight in gms..4 Author Lo ver Maaa 344.402, •Lanaing (1059) Ltd= . :120-480 • Lansing (1959) • elvers of the Gulf 258-390 Abahumow (1957). of Bothnia iv oe the Gulf 255-353 Abahumow (1057) of 'Riga Ivanovn-Berg (1932) Tibor -201 i max. 109 Cotronei (1924) Tributaries of the . 110-205 2-42 Um:ideas . (1959) Gull of Geota .1 No significant difference in length exista between the sexes. (F. sex - length 2.90 P .05 and no significant difference in weight; F sex - weight a 3.78 le min. 0.05.) The two centimeter long and 20 gm. weight claes in the populations in the Maga are distributed lu the follow-. ing manner: Length . Weight Class clues : in cm. in g. • These results of a very exact statistical analysis (Lanzing,.1959) throw not only doubt on earlier reports on differences (Ivanova-Derg, 1932, 1936; 'Applegate and Smith, 1951) =but aleo present the thought that the point in time when migration begins is elicited by hormones in temporary conjunction to the total life cycle, i.e., independent of the state of nutrition. • Even the standard variation of the number of myomeres do not indicate any significant differences in geographically widely separated populations. (Zanandrea, 1959b; Lanzing, 1959) According to Ivanovw-Berg (1933) and Lanzing (1959) there are more males than females of Lampetra fluviatilis at the beginning of the ëawning migration but at the end of the females predominate. The ratio of males to females is in this species approximately 1:1. In contrast the North American 2e/maygoa marinua (ErIckila, 1950) has • more males than females. Also in Lametra planerf, the males are more 1 numerous than the females (Zanandrea, 1951; Steele, 1963; gardisty, 1954) . 1 05 p 43 e. (see also we). During the spawning migration the body of the lamprey A experiences several changes., Some are especially Characteristic. Accore. ing to the views of several authors of the bodylength during migration ahrinUs. -94- The following results are given in detail: ; _111411p_Int fluviatilis • Neva 23% lvanova-Berg (1933) Lampotra fluviatilis Italy * 15% Lansing (1959 ; . from Cotronei Petromyzon marinus Italy Cotronei (1920) £.11›,, E521-m,213 marinus N. America Erkkila (1966) (landm.locked) Iththyomyson unicuspis N. America 22% Vladykov and Roya (1948) According to Lansing (1959) this reduction in body length is Very significant. F time a 6.83 P is less than .001. No difference due to sex exists here. Since the anadromous species cease irreversibly to teed with the beginning of the spawning migration it would be expected that the char- acteristics of the water content and fat would depend on the length of the migration route. Lansing (1959) determined in river lamprey the following differences, which in August and March had reaehed the same point in the river (05 km. upstream from the estuary). Auguat 65% 1120 18% fat March 71% 1120 . 12% fat Rardisty (1950) arrived at the following results with the river lamprey in England: November 77% 1120 31.6% fat March 83% 11 0 15% fat Tilik (1932) found similar results. For the Caspian lamprey, see page Nikoleki (1957), -95- There are characteristic - differences between the anadromous species and the species with abbreviated life cycles with reopect to:the composi- tion of body fat. In the latter the elimination of the feeding period has caused thous) differences. Aceorang to Lovern (1937) the depot fat of the anadromous species contains components of the fat of marine and treahwater fiph. Lansing (1959)/ indicated that the last named components are pre• sumably deposited during the catadromous migration. The fat of non-migra- tory species corresponds, on the other hand, according to my own observe.... tions, to the depot fat of freshwater fish (ses also page us). It has been known for a long time that the gut of lampreys is greatly reduced during the anadromous migration (Cotronoi, 1924; Weissenherg, 1925, 1920). Applegate describes this reduction.in terms of cross - sections of this organ. (Petromyon marinus .The cross-section of the gut is reduced from 7.5 - - I0 to 2.5 .• 1.5 mm. According to Lansing (1959) the weight of the mid-gut decreases to - I/10 of the original weight (Lampetra fluviatilis). The following table should be consulted. Only in exceptional instances have remnants of food been found in the guts of lampreys migrating upstream (Bahr, 1952). The reduction of the gut of anadromous species corresponds to the degeneration of the gut of non-' parasitic species. The Sharp teeth of the river lamerey during the spawning migrations are replaced by dull teeth.' The liver also dieplays characteristic changes after the conclusion of feeding.. A greenish colouration of the liver has been observed especially tewardSthe end of the spawning migration. (Cotronel, 1924, 1927; Applegate, 1950; Lansing, 1959). llese thanes are'eald to be -D6- accompanied by subtle sexual differences. According to•Applegate the liver p.320 of the male land-locked Petromyzon•marinus is dark green and the female a brighter green. Lanzing gives the oppoeite relationship • for Lampetra Iuvia tills. According to eavyer and eeth (1954) it is =tatted by a concentration of biliverdiu, which is partly excreted by the -kidneys. (Tnble in ilagUish) Footnotes to Tuble • • • . , • • :. A. Animale caught in Auguat. • • !. , • • . B. Animale eaught in•Cetober • • - C. Animele caught in January . of the following year.; ' D. Animels eaught in January but hold under nuturalv • conditions until earch. In speciee heving an abbreviated lie 'cycle coloration of the liver - with growing maturity (frem a-golden red to dark to bright green) occurs. • The riverlamprey adapte.with•roupect to osmoregulation during the - transition from the see into froehweter juet em it is observed in anadro- mous bony fishes (Behr, 1952; Merrie, 1958). In the narine pert of the life cycle a characteristic pereuterel uptakebf water occurs end tho'' abeorption of singly charge ions takee piece. The formation of urine i inereasee proportionally with increasing pereeability of the skin. 'ihe chlorido eecrotory colle of the gille decrease and finally disappear. The ■te adaptation is irreversible. .Lampreys perish when placed in sea water after they have entered freshwater. According to Xardisty (1956) the oemotic concentration of eerum oe Lampetre flUviatilie during ansdromeue migration is 126 e 143 mm, of XeCL, per . litre,,a result of limited value since it would . , . only be encountered during theupstream migratione.: -97- As expected, especially eharacteristic Changes occur in the gonads. According to Ivanova-Borg (1933) and Lansing (1959) the relative weight of the gonads of 1,!1.22212_- ,a fluviatilie le as follows: Neva population relative weight of ovaries: Sept, . 6.7 H et u • et tip et . : - Juno 17. 3 ,______I et • It et • ! et î " . tekiteaï Sept. 3.3 ! . . . June , 6,0 ,, . . • ., Maas population relative weight of ovaries: Sept. ' , 3.0 1 Mar... 13.0 I t 2 III 0 testes: Aug. 1.4 . Mar. • 5.8 Lansing further investigated the histo- and cytological Changes in - the gonads during the anadromous migration. "The testes have been found a• to contain only spermatagonia at the onset of migration. 'During autumn and part of the winter the testes contain primary spermatocytes, but in February the spermio-histogonic activity is evident. In Mareh some males may be already mature but the majority reach maturity in April." During migration. there is a graduai increase in the size of the eggs. This phenomenon is accompanied by certain changes in the granules% the zona radista, and the yolk platelets. • Corresponding changes in the gonade begin'in Lampetraplaneri during metamorphosis. '13 As bas been shown above (C818), thee it ta completely reaeonablia to (74(0e. . A assume that special hormonal regulatory proceuses elicit migration as veil -03- as the special metabolic processes during migration. The first experiment to investigate this was performed by Lansing (1959). Unfortunately definite conclusions could not be drawn. It was established that the thyroid la apparently active during the entire migratory.phase. The basophyllic cells of the proadenohypophyais greatly increases its activity during the entire anadromous migration. In this latter gland intermedin is per- haps formed which causes the dark coloration of this phase. . Sterba (1955) points out that the changes in the metabolism to consume stored substances is made possible by certain Changes in the islet adrenal system. FinallY Leloup (19521, i mentions that he was able to show a signift. cantly greater change in the iodine content in the Chord« and the ovaries than ta other tissues. .0n the other hand the blood is . markedly low in iodine (Fontaine and Leloup, 1950). The behaviour during the anadromous migration is rather unknown. According to Wikgren (1954) and Abakumow (1957) river . lamprey.migrate almost entirely at night preferring dark, moonless nights at high water. -Wikgren maintains; that an increase in activity may be observed in the morning. The speed of migration amounts to 1 - 4 km./hour (Abukumov, 1957). It must be assumed that the-animals spend the day hiding under stones and in the proximity of overhanging bunko. Even at night when the lamprey are highly active, the animale pause troquently in their progress up-stream by fastening themselves on to atones with their sucking mouths. Obstacles like rapids and weirs are overcome with the help of the sucking mouth. Lamprey which reach the spawning redds before the spawning period hide themselves without displaying rest periods..; . • -99- Unfortunately only unconnected observations exist on the migration of the Eurepen populations of sea lampreye (Petromyzon marinue). Most of these have been considered above. The return of the sea lamprey into the rivers of the North Sea is, na a rule, confined to the months of May July. P,322 The animals are at this time 05 - SO cm. long and 700 • 850 gm. in weight. In general it is assumed the Petromyzon marinus spawns in the lower reaches of the rivers. However, this presumption is contradicted by the fact that the sea lamprey is also found in the middle, and even the upper reaches./ (In the Elbe at Werben, and in the Havel, at Potsdam)1 Even species lacking ilia , lab • feeding periods and consequently a typical migration dieplay in the pre- spawning period an increased activity and local migrations. Sterba(1953) 7/ In Lamsetrn elaneri was able to show .tbat the sexually mature animale swam upstream and consequently were found in great numbers caught in weira. Tho migratory instinct is greatly reduced but it lias not been completely VII. emeng Period . Characteristic changes are to be observed in all lampreys before the beginning of the gemming period. Firet is the enlargement of the dorsal in and the consequent change in its position (Fig. 49, Weissenberg, 1925). In the female, in addition, a swelling of the epidermie, designated as an anal fin occurs. It is found behind the vent and consists of an oedematous swelling of the ventral epidermis in front of the vent as well as an . oedematous distension of the anterior end of the second dorsal fin. In the 101 male the urinegenital papilla grows,out in the tors a a penis (sea -100- 110 Weissonberg (1925) has especially demonstrated that these oestrual signa of Lampotra planeri und fluviatilis are expressed in the same way in the corresponding pheses of their life histories. This means that the shape of the fins used up to the present to separate these two species /a not justified. Figure 49 Changes in the pattern of fins of a female lamprey (Lampetra planer'. 111.). Above: utter metamorphosis. Below: during the spawning phase. • The spawning of the Petromyzontida Which differs from that of the teleosts, bas often been described with many contradictions in the early literature. Satisfactory descriptions have jugt appeared in recent years (Schultz, 1930; Bahr, 1952, 1953; Hagelin, 1959, 1959). Manin was able, to show by moving picture films the various phaaes,which occur - quite quickly?f , the , spawning_a9t) When,spawning lamprey are freshly caught and placed in obseryttion . the following may be observed: • , • ›- . • aquaria Even freshly captured rivet lamprey will only spawn in: an aquarium when certain conditions are fulfilled (Applegate, 1950;. Dames, 1950 for L. fluviatilis and planeri; and Hagelin, 1959 for L. fluviatilis). The observa- tions of these authors agree in that the conditions prevailing in the aqua- rium have a deciding influence. Normal mating activity'occurs when the bottom of the aquarium is covered with sand or gravel "without these . t• -101- 5 particular elements n \t construction raid opaWning do not take place." In aquaria without a subatrate the animals atill seemed a few signs of spawn- ing activity but the spawning which was finally seen was of low intenaity"'"." p.323 (Hagelin, 1959). According to bahrï(1953) circulating or flowing water , is of great importance. Animals in hie experiment only spawned in aquaria containing flowing water. Lamprey under aimilar'conditiona but without the • flow of water failed to bpawn. The factors mentioned above serve to stim-' • • . ' ulate the inherited Mating behaviour and thia is illuatrated by the follow.- • ing. It water ie circulated in au aquarium uontaining band and atones the lamprey undergo an increabe in mating activity from the weak degree that prevailed efore tu un activity resulting in the seerotion of the sex cells. Courtship and Nest Baildiu Secondary sexual characteristics develop in the river lamprey about 14 daye after the beginning of the spawning period (Welesenberg, 1025; nagelin, 1959 et. al.). Up to this time the animals have behaved photonegativoly, hiding under stonea and other ehelters during the day and beginning their diurnal phase o2 activity with the coming of night. They now become reetleen during the a, day and ewim around restlessly. -The nighly period of activity declines as a my own observations show. During the entire breeding period the animals remain extremely photopositive, in fact, they ceuld almost be considered steno4photic for even the rays of the sun or overcast skies can influence 'brd the mating activity of a pale. With the help of a large dlaphrogm to (lest a spot of sunlight ta the water at the bank of a etream it was demonstrated that brook lamprey not only chose this area to leitheir eggs but elso -102- followed it around in the course of the day (Sterba, 1953). Applegate (1950) and Bahr (1953) emphasized changes in vitality and phototropism. Hagelin (1959) investigated the "Steinchenschleppen" (play with stones, stone-moving) of lampreys during the first days of the spawning period. He distinguished two patterns of behaviour of atone moving. a) playing with stones without any relation to nest building. The male attaches himself with the sucking disc to a small stone bending dorsad until the anterior portion of the abdomen is in contact with the stream bottom. be,9 be5;n4 The male then turns -himself suddenly on his side and to engage in strong A • n swimming movements with the tail portion so that the body isumoved forward more bent than before. Finally the male lies vertically in the water and lets the atone fall. When the stone is too heavy the lamprey often losea its balance and tips over, b) Flaying with stones in the actual construction of a nest. While the firat kind of behaviour may be rightly designated as a play with stones, the second type has a practical function since it is concerned with not building. After the site of the neat has been chosen (see above) it i ~ the animas press themselves on the bottom to undergo often observed that extroWly quick movements with the tail by which the finest components of the substrate are stirred up and waahod away, so that a flat, excavation is created. This vibrating motion is reminiscent of that observed in the spawning of salmon. Small pebbles (up to 20 mm.) are easily removed by the sucking disc from the area of the nee site. The animals display slow, p.324 normal swimming movements during this activity. Large, or firmly , rooted atone s are transported by another means. out of the next area. The male sucks î -103- itself onto the ston to be moved and produces short, rapid strokes (about 5 - 0 movements per second) with the tail section. This action produces a considerable force and usually the large atone is transported from the nest site. The finer constituents of the stream bottom are stirred up and in this way the hollow of the nest is deepened. Firmly rooted utones are loosened by an acute bending of the anterior part of the body. Especially large' stones (4 - 5 cm. in diameter) are raised up or displaced sideways or backwards by raising the anterior part of the body. Nest construction in the river lamprey is also continued during the apawning period.' In the intervals between mating continuous nest building activities may be observed. The nest sites are frequently changed. Applegate (1950) observed that in P. merinus only the mule was involved in nest building. 'Bahr (1953) noted participation by the female of L. fluviatilis first after the beginning of spawning when enough males were present. Kagelin (1059),, observed in the same'species that the female rarely took part in the pre-spawning period. Ihe female diaplays the same type of behaviour pattern. Mating and the Spawning Act . H. .Hagelin and Steffner (1058) described the courtship of.. the river lamprey, . ct, (Uso Hagelin, 1959). Courtship and tieing are confined as a rule . to the nest area. The typical,behavionr of the male.is presumably atimulated by. . the female. In any event it may be observed that the female eel= in a tight circle around the nest bulIding . male and repeats this action by sink-. ing so that the postorior . part of the body glides under the head of the male . -or at least comes into its vicinity.. It is possible . that a stimulating . I . / • substance is released. \ -104- Figure 50 Mating act of Petromyzon fluviatilis. white. Female is (From photographs of Hagelin.) In typical cases the courting male swims from behind to the female, touches with its sucking disc the sida of the female's body in the region of the anterior dorsal fin and glides with its sucking disc forward to the branchial region. From here it travels almost to the dorsal aide té a point in front of the oye where it fastens itself, kore rarely the male approaches the female from the front. The events in courting occur more frequently finally culminating in copulation. The male then glides in a manner similar to courtship along the side of the female's body, fastens itself securely in front of the eye and winds himself at lightning speed around ber with the tail section of its body just in front of the first dorsal fin (Fig. 51). The rineaike sling so formed exerts not only pressure on the coelom filled with eggs but the sling is shoved backwards to the beginning of the second dorsal fin. The male strokes the female with this sling and presses the eggs in the posterior part of the coelom through to the opening of the genital papilla. By vigorous motions the sexual products are immediately expressed, the whole process lasting about five seconds (Fig. 50). Uagelin (1059) has explained for the first time the significance of the morphological changes which occur in the spawning phase (swelling in the vicinity of the female's genital region) and the events of the act of copulation. The swelling on the female at the leading edge of the second dorsal fin impedes the male from moving farther down the female's body and possibly covering the genital opening. -105- Figure 51 'Spawning brook lamprey. (1....112e2IELI planer» The brook lamprey has been little investigated with respect to the copulatory and spawning behaviour. The observations of Schultz (1930) and Sterba (1953), however, permit the establishment of several notable differences. The characteristic nest building of the river lamprey has been retained only ln one phase lu the brook lamprey. The moving of stones undirected with relation to any nest site may be observed. No purposeful construction of a shallow depression la observed. The spawning sites are chosen spontaneously (no depression prepared in advance) and are changed continuously. The spawning sites preferred are sunny sandy areas between 101 • course gravel (see page 323). Copulation itself appears to be el:miler to that of the river lamprey. Sterba (1953) points out that Petromyson planeri p.326 always spawns in groups which are composed of 4 - 15 individuals. In the central area of Germany these groups consists of as a rule, of males to females in the ratio 2:1. Hardistyi (1054)„after six years of observation) . obtained the ratio 1:1 for populations in England. - In the mating set all the females of a group lift themselves closely _together at the sema time, On a stone and are> treated by the males in the manner described tor'the river lamprey (p,..325, Fig. 51). The surplus of i\ males makes it often neceseary that:two males mate with one female. As in , the river lar;iprey the femalebeate ber caudal end vigorously, an impulsive movement whieh likely has the prime purpose.of driving the expressed eggs into the stirred up sand and not to construct a depression ai earlier authors have assumed. Tho number of mating* in the brook lamprey - is numerous under -100- the natural condition i and good weather conditions (suntihine). Onej4undred One. A A matings per day were established with marked animals, and changes in the composition of the mating group were noted ou the successive days. Table Protocol of the composition of mating groups of Lampotra planori over a period of seven days. • Day of • Females Females 1 Males Males newly marking Marked newly arrived Marked arrived Remarks Two marked males - in a mating group 130 cm. upstream. lOne marked male in a mating group 1 30 cm. upstream. 1 . . • . , ' .A . :: • One marked male 1 I . • « ' . !. ' 1 ': 1 3201 :mmilltelLear k . . , , 1 . ' • . • The missing tagged ; • • ' ' , 1 ' - J « i . , . • animals are at k 1 . i . • ' ' other locations • . 1 Changeable weather. The mating groups are attracted to each other chemotactically. The number of eggs expressed from a female during a single mating la quite •variable but in all each female lays 600 1500 .eggs., FreeLaying or Copulation • The unusually long, narrow and even movable genital papilla of the male lamprey were considered py Ferry (1883) and Lomann (1912) in their - time to be indicative of internal .fertilization. , This assumption, howeVer, • -107- haà boon considered by Dean and Sumner (1897) to be unlikely. Vejdovsky (1893) und Cage (1905) refuted this by direct observations. With few . exceptions the simultaneous releaae of sexual products has been maintained to occur by Applegate (1950), Sterba (1953), and Ragelin (1959). - It is, at this point, necessary to coneider more closely the secondary changes which take place in the region of the cloaca' space during the .14■ 41' K4,4' spawning phase. As bas been shown on pagetilledied, the two primitive A A ureters and coelomic ducts are united to form a canal with its own parti- tion. The urinogenital papilla projects behind the opening of the anus in the cloacal space. The cloacal space itself is confined by two lateral folds, the cloacal folds. At the beginning of the spawning period char- acteristic changes in the cloacal ares may be distinguiphed in the sexes. In .the female the lateral cloacal folds swell, the ,Irinogenital papilla. romains small and is covered by the folds of the lateral cloacal folds. In the male there are changes in the cloacal folds, on the other hand; the genital papilla grows out in the form of a tube in length and at the same time becomes strongly vascularized. At:the close of the spawning , . season the genital papilla projecte from the cloacal folds and, like a penis, is capable of erection. In addition, there arises, however, in • the female an oedomaous swelling lying directly over the leading edge of the second dorsal fin. This swelling prevents the sling formed by the male during copulation from slipping too far back and covering the cloaca. Hagelin (1959) was able to show.very clearly by means of moving pictures • . that, on the basis- of the topographic relations the male urinogenital pap- ilia was unable to reach the female cloacal'spaCe.. , When the sling of the -108- male glided down the body of the female until it was hindered by the swell-. ing on ber body, the space between the two individuals was 20 - 25 mm. The male urinogenitial papilla about 6 mal: in length, rubs against the body of the female and is therefore oriented towards the female's cloaca.'« Interior fertilization can accordingly bo ruled out and the penis-like organ be considered to function in directing the stream of mut. (Fig. 50) et In the brook lamprey similar relations are present« Sterbn (1983) - observed in 18 out of 60 females spermatozoa in the cleacal space. Since, during copulation in this species the distance ceparating.the,urogenital ,papilla of the male and the cloacal opening is smaller, it may be conceived ,that some milt of the stream from the papilla UBS entered.the body cavity. •It was assumed in 1953 on the basis of.these observations that there was a transition from fertilisation of the eggs in the water to internal:fertili... zation. .This assumption is very'questionable'WhanOne considers. the more • exact knowledge of these processes in the river lamprey. .* • VIII. Post-spawning Apart from the reports of. early amateur biologists (Kammerer, 1905, , . Schreitmueller, 1909; Fraenkel, 191l) all investigations are in agreement that lampreys spawn only once and then die. (A.ieueIler, 1856; Lubosch, î 1902; Gage, 1911; 14uternorn, 1926; Weissenberg„ 192$; Damas, 1980;« War, . • .1952; Sterba, 1953; Hagelin and Steffner, 1958; lenzing,.1959).. The dune' :tion of life . after spawning . can,however,• be'very'variable.. Next to . 'specific and sexual« differences,':climate plays an extremely,doolsive role.. As 'a rule . the female : of the .brooklampreisurvives'10 - 55. days'after - -109- spawning. The male liras 20 - 40 days. No results are recorded for the river lamprey. Since the gut in all lamprey has degenerated already by the time of spawning and the stored foodstuffs have been used for the • development of the sexual products, death may be considered to be the • result of exhaustion. A very small amount of ovarian tissue remains in the female. On the other hand, the males still possess ripe follicles with mature sperm (Sterba, 1953). The depreseed reeistance of the p.328 animals after the spawning period causes peritonitis which shortens the post-spawning period. According to Gage (1928), Applegate (1950), Sterba . (1953) Hagolin and others (1959), the various species of lampreys are. photonegative after the spawning period and hide under.stones or seek out • deep holes where they die buried in sand and rubble and quickly decompose. In the male the migratory tnsfinct appears to be retained longer. For this reason alMost only males are caught in the area of a population of L. planer. Gage (1928) and Applegate (1900) found great numbers of the remains of notochor4s of P. marinus in backwaters of Streams. • D. LAMPREli FISHERIES . (With the co-operation of my student K. Seiler) Fishing Grounds and Catch in Central and Eastern EUTODO Of the species occurring in Central gurope $ only the river lamprey (Lampetra fluvlatiUs) has any commercial importance. The brook lamprey (Lempetra planerl) and the Danube lamprey (EudontonIzon danfordi and Eudontomyzon danfordi yledemi) are too small and Petromyzon marinus too rare. The places where they are captured and the times of capture are closely connected to the life cycle of the river lamprey. As has been described on page 268, the river lamprey migrates after the conclusion of its feeding period spent in-sea and brackish water into rivers searching ' out spawning grounds (in the lower, middle, and upper reaches). , Figure 52 The most important fishing grounds for lamprey on the northern coast of central Europe. -very good yield,. -moderate yield, -abandoned • fishing -grounds. The fishing grounds of this anadromous species in Central Europe are, therefore, estuaries and lower reachea of rivers of the North and Baltic p. 329 Seas. In the North Sea region lampreys are mainly Might today on the Dutch coast. In the Baltic,sea the catch decreases from weet to east (Fig. 52). The nutrititive value is extremely high at the beginning of tt) migration (see we). They weigh on the average 100 g. with the length A • , varying between 350 and 450 mm. , I According to Lanzing extraordinarily good harvests have been obtained in the lower reaches of the River Mass. Year Catch in kg. Estimated number of lampreys •••••••■111.1011 • 1953 20,000 ' ; 200,000 1954 9,500 95,000 1955 . 11,000 . . : 110,000 1956 12,500 ' • 125,000 1957 16,000 , : 180,000 In Autumn during the lamprey aeason the nightly catch can amount to 100 - 155 kg. Lanzing estimates the number of animals ascending the Muas in a year to be about 250,000. In the Rhine the lamPrey fishery has mark- edly decreased e,t2tor the First World War. The fishing grounds extend, according to Seligo (1926) front the•estuary up to Duesseldorf. In 1913 twelve lamprey fisher4es were along the Dutch part of the Rhine with 1170 baskets in operation. The °ate, evea before the First World War was far A.ower than that caught in the Mans. , . , !. . . Year Catch in kg. 'Number 1910 . 1,983 H ' . 27,760 1911 . 4 237 59 , 742 • , L... . V 1912 V - 5,486 . 76,805 1913 . V 6,794 . .95,117 1914 • missing. 31,500 .missing: , , . 14,554. The river lampreys'caught in'the Rhine had an average weight 'of 113 g. and un average total length of 415 mm. During the Middle Agee the lamprey fishery in the Rhine extended na far upstream as Strasbourg. Daldner (1886) • 1] wrote..."The lamprey were caught in 1.argenumbers at Kornung and Mortzen...." -112- No information is available on the catches in the vicinity of Ems although the\harvest in the region of the estuary from my personal expel.-- ience was not considerable. , In the River Weser lamprey are still fished in the months of September- November; however, the yearly catch is very variable and small in relation to earlier catches. According to Hensen (1874) the lampreys in the Weser were, after "sels," "Stohr," "Quappe" and smelt, the .chief commercial fish. Even Werner (1938)/ stated that the estuary of the Weser was a fishing ground for river lampreys, and estimated the Yearly *catch to bo, in the lomer Weser, about 25,000 kg. • The importance of the lamprey fishery in the Elbe even before 1900 vus significantly less than in the Moser; Rhine, or Maas. Aside from p.330 fishing grounds in the estuary of the Elbe (CuXhaven and Hamburg) and the lower Elbe, the fishery of Magdeburg was important. (See Selig°, 1926; Werner, 1938; Nonne, 1939; Bahr, 1953; and Bauch, 1948.) Up to 1930 the catches, in the above-named portions of the Elbe, were approximately con- stant and good. However, from 1930 on lamprey were caught irregularly and in insignificant quantities. As in other places the decline could be i?›1 Pa'3e- traced to the pollution of the rivers (see 3*). In the season 1933-4 only (November until the end of February) 2400 - 3000 lamprey were reported. During and after the Second World War the number of lamprey caught fluctuse- • ted from 200 - 300 per year. Among the minor fishing grounds north of Maddeburg, Tangermuende, Arneburg, and Werben, not only river lampreys wore captured, but also some 20 50 sea lamprey appeared regularly each year ' • in the weirs.. Individual lamprey.ascend the Elbe up to the Hawn und th -113- Seale. In the whole Elbe area, however, there is no longer any Inmprey fishing. Ali lamprey are caught accidentally in eel weire. In the region of the small rivers emptying into the ealtic Son, only individual specimens are caught. The lampreys. fishery in the lower Oder formed an important component of the entire fisheries during the latter half of the nineteenth century. According to Seligo (1926) about 8% oe the entire catch of flab of the lower Oder and tributaries not including the Stettiner naff s ' consisted of lampreys. Cut of the twelve most important species for this region the lamprey was placed:in sixth place before aalmon. In the btettiner Half/ . itself lamprey were fished but the number has decreased before the numbers of salmon, perch, and smelt. In the rivers between the Oder and the Vistula lampreys were fished in great numbers during the nineteenth century. No information is avail- able on the pre$ent size of this fishery. In addition to these no infore- ,, ■ ation exiets on the lamprey of the Vistula, v Tee Fri.schorrid Kurische naff e' 9 c ) A A . as well an the rivera which empty into these bodies. 1 have had to.resort to older sources of information. According to Hensen (1874), Mankowski, (1024), Selig° (1926), and Werner (1968), large numbers of lamprey were . captured in the lower reaches oe the Vistula especially in the estuary. In 1023, for example, along in the region of Danzig there were 450 500 teaps for lamprey. Each fisherMen receives 6 7 of these catching sites and can set up 400 basket weirs in this area. dood harvests have even been reported from the canalized Vistula and the Nogat. A special lamprey industry is known in Danzig. Zn the Frische finff and its tributary streams the proportion of lamprey ili the fishing catch alwaye small -114- although in good years up to 3000 kg of lampreys have been caught. Accord- ing to Soligo (1926) the proportion of lampreys to the entire commercial fishery is 0.19% with nu average total value of 0.37%. . The catch of lampreys is of extreme importance in the Kurische Haff and tributaries. The lamprey fishery is concentrated on the estuarial area of the river Memeli (Neman). Werner (1938) and Buchholz %tate that the Memel is most important and well known place to catch lamprey. The catch, however, has been declining (Buceolz, 1938). A good catch has been realized in a tributary-erm of the Kusz (Skirwith). In this latter A region, according to Bucholz >catches of 240,000 lamprey having a total A weight of 12,000 kg. worth 4,000 gold marks were harvested,in the average year. In the Kurische Haft itself in the years 1905-1914, 2,700 kg. of 4,000 gold marks were caught on the average each goer. This lamprey worth -amount comprises 0.03% of the entire fiait harvest with a value of 0.29%. Floor/eke (1025) estimates that the lampreys caught off the coasts and not in rivers between Danzig and Memel averaged 300 - 360,000 yearly. , In the Gulf of flige and in the tributary river Buena (Daugava) and toc.‘$) Cr r Lu , Aa (Gauja) the 1 amprey next to the "Streemline the most landed fish. " A ) - (Seligo, 1926). In 1911 148,000 kg. of lampreys were caught comprising 2.5% of the total fish harvest and 8.1% of the total monetary value. Even today the catch of lampreys is said to be considerable. The Gulf of Bothnia is also good fish grounds for lampreys. Accord-. ing to Ivanova-Berg (1932) about-269,000 lampreys were caught in the river Nova. Nikolski (1957) reports that the lamprey fishery in the Nova produced earlier 6,000 kg.. per year. -115- The catches of the lamprey fisheries in the latvian socialist republic g C , is said even to have increased in recent years. , (Personal communication from the Freshwater Fisheries Inst., Leningrad.) In 1911 in one area 143,000 kg. were caught. In the same area in 1054 the weight was 252,000 , kg. This area contains the richest fishing grounds for lampreys in the whole of Europe. The Caspian river lamprey (Caspiomyzon wagneri) bas also commercial . importance in the Caspian Sea and in the Volga River. From 1930-41 the' yearly catch of lampreys averaged 35,000 kg. In 1954 the figures given for the Volga and the Kura are 4, 4000 and 0,800 respectively. Fishing Season, Equipment, and Methods • Tho time when lampreys are caught in the eetuaries and lower reaches of rivers depends upon the beginning of the anadromous spawning migration. In the middle reaches the time in the season is . somewhat late. As lias been expressed so ranch previously there is much local variation in these times. qi pe With few exceptions in the literature, autumn is giver‘S, Se also el% s Who dependence of migratory activity on certain climatic factors .0M) makes it understandable that the expectancy of catehing lamprey etC3 A is coupled with these. (Selig°, 1925) cites the following rules: "Dark nights, muddy .water e_frost and a west wind favour the catching of lamprey. Persistent thawing and an easterly,wind decreases the catch." Buehholz also noted similar relations. According to the reports of Master Fisherman Russfeldt of Werben and Fishmastors in Bremen, the catch of lamprey is closely connected to the water relations. Only when the -116- current is strong and the water level high do eels and lamprey move up-. stream in large numbers. Those climatic relations multiply the dif- ficulties in fishing lamprey and limit the setting of equipment where regular and-profitable catches are to be expected. As in other migratory fish the method used to catch lampreys is that of stationary traps. The gear used is variable, depending upon the local- ity. A quite thorough account of this gear is found in one of the earlier handbooks of the present series. (Selig°, 1926; especially pages 214, 227, • 231, 233, 253, 250.) I will confine myself, in light of thie more thorough treatment to a general description. In the Elbe region draw nets of dif- ferent sizes are used in the lamprey fishery. The draw nets are set with - • their openings pointed into the current. Those lamprey swimming with the current are carried into the nets. The "Steert", the pointed end of the lamprey net, accordlng to Selig°, has material of 13 mm. mesh, is three ,metres long and a brim of 210 mesh circumference. Somewhat other methods are used in the middle reaches of the Elbe (Bauch, 1948). Especially at •the Craeow Dike at Magdeburg. At this place the animals attempt to circumvent the dike and are washed by the rushing waters into nets. In the stretch of the Elbe at Werben draw nets are used to catch both eels and lampreys which correspond quite closely to the "Ankerkuile" of the Dutch Rhine and are conetructed in the following way: A single armed anchor of approximately two zentners holds a 20 metre long chain from which four ropes and four corners of a net held open by loge against the stream. The belly of the net'itaelf is, as a'rule, 6 metres wide, 3 m. high and about 15 metres long. 7117- Weirs are employed more frequently than draw nets in lamprey fisheries. p.332 ln the Dutch Rhine there were twelve fisheries in 1913 operating 1170 baskets (Seligo, 1920). In the Weser and the Elbe bottom weirs were installed and, in addition, moira made from willow fonces were erected on scaffolds.. The catch by means of such weirs is based on the observation that lampreys during the spawning migration prefer high water levels, to - be sure, but are deflected by strong currents. For this reason they swim at times of floods at the side of the river where they encounter the fence of the weir and enter the baskets sot to catch them. This type of gear has not existed for a long time. Although fishing with baskets in the Elbe has produced high catches it is no longer profitable (Bauch, 1948). The weir is the charaeteristic gear on the Untie Sea. Seligo (1926) reports (p. 241) that lamprey fishing operations in the Oder at Schwedt are carried out by bettom weirs hung across the stream on ropes. Even in the Stettiner Haff catching with weirs was widespread. In the years 1907- 1915 the average yearly catch was 10,576 baskets. In the lever Vistula round baskets were employed; these were 1.25 \\\ meters long and 0.25 meters high. Each fisherman had 8 lots. The‘traps I wore fastened by means of a rope 1.33 m, long called the string. A 200 U4 A A wire cable was attached to thestringand fastened to the bank so that • it ran .across the stream. In the district of Dirschau (Tczew) , wooden traps were characteristic (Vol. V .161). These large, somewhat loosely woven basket traps have two rather narrow throats 1.50 m. long with an entrance of 0.707180 m. - Tho whole:arrangement is head by a woven willow ring on the inside. The thin, looSely lying ends of the wands of the front -«a- II end of the trap--called theear+cling closely to the bottom. Frequently 'these traps are used to catch swimming lamprey since, at night, the animals prefer to swim close to the surface. About ton such traps are faetened with their sharp ends in a row. In the seine region large sacks are aise used in the lamprey fishery (Vol. V, • Fig. 03). In small lamprey fieheries in the Memel estuary unusual means of catching lamprey are employed (Soligo, 1025). They call these traps; "Dukkis" (Vol. V, Fig. 105). egg-shaped, woven out of willow wands to form baskets 1.25- 1.30 m. long and about one halt as high. The wall on the rounded end r o a bottle turned inside entend formed into a funnel and throad -sembles having an opening 12. - 15 cm. wide. On the sharp end is a plugged opening from which the fish.Qcan be removed. The Bukkis wore attached to willow ropes from the bank in cairn water. . In the catching of lamprey the Dukkis were mailer and were called p.333 ; Bukinells. nesides these mentioned other gear was used in the Meml region reminiscent of the moans used to catch lamprey in the Vistula. "Iron chains were strung across the Memel on which willow lamprey traps were hung at intervals of 40 - 50 cm. The openings were directed downstream so that the lamprey swimming upstream can enter the traps un- hindered." Floericke (1925) writes that lamprey are also caught in "Brickensaecken" at Elbing (Elblag), Memel (Xlaipeda) and the streams flowing into the • Nuriache Haft. In tho River Aa of Livioud (Gauja) weirs were constructed to catch - lampreys (eoliso, 1925, p. 259). Those are secured by 00 - 70 stakos stworted by severs./ euxilliary stakes.. Lamprey treps aro-sot in open- ings in tho voir prepared in advance The weirs go across the entire width of the river. 'in the River Du= (Dougsva) which hes a roce.,.y bottom, tho voir is woiebtod down with stones. The vole usod here (Murdon) con- . ring with bast or state of roda which are bound together on an inner cords made from roots. Tho length of such o trap is nnd the diameter at tho opening 0.78m. The bast catch occurs when the water does not cover the basket entirely. et conditions of high water two baskets ci be stacked ono on. tho other. According to Selig° (1 )20) ono basket can catch up to e00 lamprey under favourable conditions. • A specia1 way of catching lamprey in eYuhren" especially in holes cut in tho ice, in the eomel Delta. According te Biook, a good number' of lampreys were caught in thn ice. Seliem. describes tho observation - . pot s with which thei catching vas carried out: '4.eboy consist of n row 02 traps ton meters- long having wings 4-5 otors long and as high as the water depth (therefore 2-4 metera). Triangular vekon hoops are also present. Tho gauge oe the net at the entrance ts aPPronlntolY 25 mm and in the rear chamber (8tngge) where the' animals are captured, only 7 mm. Tho gear it ln the water such that the Wielff0 overlap each other and the row, which con contain as much ae 3G traps, eay roach as ear aa the niddle àe the river (Value° 4, Ftg. 164). When the ice cevor ls thick this means cannot be used. •Uxact information en the nodern -toehniques is ogy available for the Elbe region. - It can bo assumed that modoryeimethods do not depart essentially from the traditional methods. «,breemov 1:Iceeb> describes a new method of catching lamprey. By an of barriers of lieht the photo agativa lamprey are herded into pussagos containing traps. Bahr (10033 mentions that lamprey fisherman from the Memel region who se now in Hamburg use their traditional methods in the Elbe River. nnhr in 02 the opinion,' however, that the introduction of now mothode would not Improve the lamprey harvest. Un North Am-erica electrical methods are used . to decrease the population of lampreys, by Lining them during their annua1:spawn/1re migration. -120- According to Lanzing (1959) , lamprey were used up to 1915 as bait. From 1660 to 1961 there was in Vlaardingen aven a large holding tank (Prikkenwater) in which lamprey were hold for this and other purposes. Every ship i a crew included a "lamprey biter" who killed the animal by a p.334 bite in the head thus destroying the brain. The paralyzed lamprey was then placed on an angling hook. Lamprey larvae today are used in many places as bait for sportsfish. Ammoceetes may be collected in amp quantities for scientific pur- poses by draining a section of a stream below a dam. Tho larvae retreat first o al1 into the bottom but after the bottom becomes dry agnin come out, socking pools of water. More fruitful is still another method. A weir lying above an ammocoete bed is opened and closed after a short interval. The surge of water washes away sono et the muddy bank contain- ing the ammocoetes and the animals reurrow below the weir. Warm the weir is shut this area is dried and lamprey larvae may usually be collected here in great number. Individual apecimena con also be collected with a spade. Individual images . may be boat collected by picking them off weirs. 111. Value of Lamprey Theeommercial value of lampreys is limited by the low numbers of the catch, the average weight of the individual animal, end by psychological attitudes of the consumer. Only when the lamprey is considered from all these viewpoints and all these are favourable, is a lamprey fishery feasible. In Europe these three features are favorable for the river and the Caspian • • 7121- lamprey. Although the brook lamprey occurs in largo numbers, its average weight is only 10 g. The sea lamprey and the Danube lamprey occur in small numbers. The average weight of the river lamprey is small, oven with an average weight of SO - 140 g. However, an industry can exist because of its occurrence in largo nUmbers and because it is prized by the consumer. • It is of interest to note that, in contrast to Europe, the soa lamprey fishery in North America is of minor importance althoueh the sea lamprey living in the Great Lakes far exceeds the European river lamprey with respect of number and average size. The North American consumer considers the lamprey to be inferior. According to a personal communication from the University of 'Wisconsin, consumers are repelled by the snakelike form and the ugly head. For the ea= reason the eels Jal North America are çonsidered in the same light. ln Europe thelituation is revereed and the resemblance to the eel has even enhanced the value of the lamprey. For about 2,000 years the consumer has prized the zee lamprey. lbo value of the lamprey lias boon emphasized in many publications. Bloch (1785) writes the following: "The flash itself possesses an extremely delicate flavour and Galon phyeician living about epo A.D.) claimed it was (a amous Graeco-Roman easy to digest." And in other passages. al'resumably=th=geode,tes.te,e ee custom ozigi7 Au -neted-of a gift of lamprey pie from the city of Gloucester to the king of England overy.Christmas At te season lamprey are difficult to catth and A often cost as much as a guinea per animal." . • . Flocrike nlao writes concerning the value of the lamprey; "The or itt 1 In a., 'e-ed, e, 4, & te4: e. c.,e, 111 . ■ „ . .. . i I . -122- gourmets in the cities named (Elbing and Memel) wait with groat anticipa- tien for the appearance of the first lamprey fisherman in early autumn. remember the happy feeling in Memel when the rifle ehot or rod flag was flown over a beach snack bar proclaiming that fresh, roasted lampreys were available. All the gourmets ran to the stand and sampled the lampreys roasted in their own fat. There was a danger of eating too much since they were not easi/y digestible. Unfortunately thoge living inland did not have the opportunity of eating the fresh product and were restricted to eating the marinated fish.'' Mankowski writes: "Who ha s in recent years eaten or seen lampreys? Certainly they appear now and again in the fish markets as delicacies either mnrinated or roasted but their purchase depends on a well-filled purse." Writing about a visit on the Vistula: "To the great surprise of the guests there appeared,along with other delicacies, marinated lampreys in such a number that each guest was able to satisfy his appetite. Such s an abundance was difficult to imagine, and was due to good fishing gear, a good fishing season, and good circumstances." . The high gastronomical reputation enjoyed by lampreys has also found a place in proverbs and sayings, for example: "Uhey set lamprey before him", a saying which was used in the 17th, 18th, and 19th centuries in Northorn Germany when someone condemned a good dish without cause. In arecs where lamprey fisheries had developed due to the factors outlined above and where a market Wtle assured the food value of the lampreys assumed an importance. Because of its limited supply, the lamprey, however, cannot seriously be considered to he an important source of nourishment. It has commercial value because of the good price the lampreys fetch. -123- eish there is very little In contrite-.. to other commercially valuable \\ \ waste in lampreys since only the head is thrown away. Gut and accessory glands remain in "the fish. According to Selig° (1926) the lamprey belongs to the "fat fish" approaching the col in its Lut content (Reuter, 1935). Each 100 grams contain: . - ... • • ' Protein Fat Carbohydrates Calories 20.2% , 6.6% 328 Lamprey (smoked) 25.6% . Eel (smoked) . . . 18.7 27.7 . • i 1.0 -333 "Buockling" 20.7 9.6 174 • Roast Beef . 28.0 : 4.5 - . 157 . Roast Pork - 24.0 24.0 : 4., 322 It must be remembered, however, that the fat content of lampreys p.336 depends on the time elapsed during the anadromous migration for the fat content quickly declines with time. Nikolski (1957) found the following variations in the • at content of the Caspian lamprey with time: . ; Beginning of migration Volga estuary ' 34% fat During migration : . Stalingrad , 20% - . › (Volgograd) - - End of migration , Saratow 1-2% fat These results clearly show that fat is burned up to supply energy • during the 1,000 km. long journey lasting six months. In other lamprey regions of Europe similar relations obtain. Became of shorter distances the differencee are not as pronounced In any case - lamprey fisheries must take.this into especial consideration.: For detaila on metabolism during ,migration, see 1;et, - Although a portion of the fat of a fish is removed with the entrails almost all of the fat is . retained in the body of the lamprey. The protein content of lamprey is rather . higity pet„.1,ce.‘,435)e.,_ As Ranke (1959) was able to show the musculature -cd .lampreye contains not only i. • • -124- amino acids bound in peptides but also free amino acids. For the river lamprey the following were found: Cystinn Arginin Histlein Beta alanine (The content of beta alanine is especially high.) amino acids bound in peptides: Glutamic acid, Histidine, Leueine•-iso leueine Phenyl - alanine:- • • Quantitatively in 100 grams of :amino acids bound in peptides are found 1 - 5 gras. of free amino aeids. The content of free amino acids is influenced by temperature and salt content. However, it is yet to be shown that the keeping qualities of lamprey fleoh are as good as those of fish. •Arginine could . only be detected in 4 out of 30 fish inveetigated. Free amino acids are a favourable substrate for bacteria and this tact must be considered in the proservation . of lamprey. , (The following page le concerned with prices of floh and lamprey in European fish markets-a= not been trenslated) .IV.. The Preparation of Lamprey In most reports lampreys are regarded as a special delicacy. (Mankowski, 1924; Hoffman-Altona, 1933 et. al) These characteristics apply only to those lamprey caught . early in migration and coneequentIy in good shape . for proceseing. The flesh of lamprey only tastes good at the end of the feeding period and the beginning oe the migration. During the feeding period the flesh is dry, tough end tasteless.as it is at the end oe migration. Since in the region of the estuaries of the North end Deltic Seas the mi- gration begins in Auguet or September, persisting until spring with varying intensity, the autumn catch J,s the most valuable. Late or spring migrants -125- 7 naa e Wo have the lowest fat content as the early or autumn migrants (see.3eno t.)-) • r "' Aside from this the taste is controlled at the end of migration or by dolay... cd migration by certain changes in the metabolic products. , The processing of lamprey must be done immediately after slaughtering the animals since the keeping properties of the flesh is poor because of the high content of free amino acids. Direction s. in the preparation of lamprey may be found in Bloch, 1785; Mankowski, 1024; Nitache and Bein, 1932; Ruehmer, 1934; Worner, 1938; Schindler, 1053. Detailed reports have beau The lamprey are killed by written by Soligo (1926) and Buchholz (1938). pouring salt over them or, according to Selig°, by scalding them in boiling water. The dermal mucous may either be removed With a cloth or by the fingers. Only in certain regions are the entrails removed. UGually the ' head is cut off although in many regions the whole animal is processed. Lamprey can be bambecued, roasted, smoked, or marinated. Barbecueing of lamprey is carried out on special racks inserted in ovens. In the roast- ing barrel individual lampreys are skewered on steel spikes or on spits. In contrast the lampreys may.be cooked "swimming in their own'fat". Smoking is carried eut in the same manner as that of th o eel. Fresh . or.roasted' . are marinated.\ individual recipes or marinating differ greatly, lamprey but in general the process is Similar'to that carried out with the herring. mari- nated lamPrey are often packed -in-jelly., Finally, living lamprey are sometimes shipped live In many regions. According to Neune (1939) prepared lamprey come in-cans of 0.5, 1..1.2 1 of 4 liter or in wooden containers. - \\ Smoked lamprey wore sent in to 10 kg. boxes. (Buchholz, 1938) In the Ruegon district the lamprey were layod,ono 9n top ,..7.2, the other and pressed p.339 in flat wooden boxes. Special lamprey industries exist in regions where they -126- are caught in large numbers. however, In regions where they were present. in small numbers, hotels and street merchants prepared and sold them. Even as late as 1920 roast lampreys were sold in the streets in blagdeburg.. Finally it should'be mentioned that the fishermen themselves prepared some of,their catch. In North America lampreys have been made into fish flour and fish oil. V. The Reputed Toxicity of Lampreys In soma reports lampreys are reported es being toxic on certain occasions. According to Taschenborg (I009)-the serum of lampreys and the secretion of certain dermal glands are poisonous. Rnuther (1924) mentioned the toxicity of the serum with respect of the injection experiments of Cavazzini (1892). • Nowadays this toxicity has little significance since it merely involves the incompatibility of the serums of two species of.snimals an effect which plays no practical role in commerce. Even the toxicity of "certain dermal glands" is questionable. According toyaschenberg this secretion produces •severe diarrhea. All that is . known.about,the presumed poison is that it • is not destroyed by heat. Summing up the toxicity of lamprey seems questionable to me, since in each of the instances mentioned above, the, influence of other factors such as disturbances in general digestion' wore not investigated. It is conceiv- able that the excess of fat in the lamprey's body could lead to difficulties in digesting the animal. Even the high perishability of lamprey bas not . been reported to have the cause of poisoning. Zt may be the basis for ,. North American folklore that lamprey are inedible. • • -127- VI. Lampreys as Fish Parasites Damages to fish caused by Lampetra Fluviati/is in the Baltic Sen up to tho present time the ectoperasitism of metamorphosed river lamproys was seldom observed. This fact makes understandable the uncertain reports in early literature of the modeof feeding o£ this species. Often it would be reported "the adult lampreys feed as the sea lamprey on fish flesh nnd blood." Not less frequent were such reports that the river lamprey sto • small animals (worms,.snalls, crustaceans, and insect larvae) or ate carrion. • The first therough invostigation on tho harmfe effects wus carried . . out in tho vicinity of the coast of Samland by Bahr (1933). Fish display- ing wounds caused by the sucking of.lamprey have been known by fishermen in every region for a long time. The origin of those wounds was ascribed to the river lamproye partly on the basis oe sUpposition,.and partly on . • . the basis of observation. According to Bahr,'wounding bogina in this and p. 346 other areas about the end of June and attains j,te ugh point during the last weeks of September. Tho wounding begins to decline in October. From November to June of the following year fish with lamprey wounds are only sporadically seen. Tho fish attacked aro cod, herring, and sprats and rarely flounders. Intense attacks eccur in the close vicinity of tho coast at about 1 - 2 miles offshore. EVen in this zone, however, species are especially attacked which steekoar the bottom and aro fiehed with bottom book s (example, cod). Tho type of wounding is similar in herrings und sprats although different in cod. The wounds aro produced in the following eanner: (see also qt A The lamprey attaches itself on the fish and penetratee the skin of the fish -128- with the teeth of the oral funnel. The tooth-studded tongue thon rasps a deep hole into the musculature of the eish. On a cod 21.5 cm. long Bahr found six wounds, each about the size and shape of a two mark coin. In a typical wound the outer portion is the larger consisting only of a super ficial destruction of the epidermis. Tho inner portion, on the other hand, is a hole 5 mm. in diameter penetrating the musculature. The lower hole is causod by the action of the tongue. The wounds on Iprats have a largo area. In single instances almost half of the vertebral column was exposed and in other cases the wounded area extended over the side of the fish (Bahr, 1033). In no cases was the coelom opened. Schindler (1953) mentions, on the other hand, that lampreys not infrequently bore into the body cavity. Bahr (1952) showed by supporting laboratory experiments that lamprey fed upon fish floshand fish blood at relatively long intervals of time (as Petromyzon marinus b. Getàe, 1928). When:held in freshwater lamprey also attack each other. . Injured fish die frequently from an attack itself or by wound infeetion usually by a.eungus., The flush of a heavily bled eish is no. longer market.- able. , • • ■ •• In sprats the loss is not especially great since the fish themselves are small and can be picked out... The lose in a catch of cod is greater because of the size of the fish, and because a larger proPortion of fieh • have boon attacked. In . all, though, the loss in fish is small compared to the commercial worth of the river lamprey itself. • Eglito (1058) has made many observations on the parasitism of lampreys -129- in the Deltic Sea. By analyzing tho stomach contents the findings of Bahr (1933) have been confirmed. Eglito reports also that /horring,/Sprats and cod are attacked. The oral tentacles are said to be larger during the parasitic period than during the anadomous migration. A recent account of the damage doue to commercial fisheries by lampreys has been presented by Abakumow (1959). The Damage Bone by Petrom zou marinus (Land-locked) in the Great Lakes of North J%merica In contrast -to Europe where the paraaitism of the river lamprey has practically no commercial significance, the lamprey in some of the Great Lakes of eorth America has practically deetroyed the fishery. Since those damages have more than local importance they will be discussed here. The parasitic lamprey (Petromyzon marinus land-locked) which occurs in the Great Lakes is a form of the sea lamprey which spends its entire life . cycle in freshwater. The segments of the life cycle of this species (land-locked) corros«- ponds to that of the river lamprey. After a larval period of four yeara the catadromous migration to the lake occurs where, after a paraaitic period of 1 - 11/2 years, the animala return to the rivers to spawn. Each female carries about 51,500 eggs. The following presentation is based mainly on the work of Hilo (1956) and Tesch (1950). The work is concorned on the decline of tho commercially valuable lake trout. -130- Catch Statistic of Lake Trout /n Lake Michigan - In Lake Huron - 1044 3000 tons 1305-1935 850 to (ay.) . 1949 • 500 4'ovl.s 1043 2.5 tone 1954 53 kg. 1955 16 kg. Originally the land-lockod sea lamprey was . confinod to Lake Ontario since Niagara Falls prevented ita further migration. With the construction of the Welland Canal in 1332, this'natural barrier became ineffective (Oliver la Gorce, 1953). Due to the rapid spread into an environment con- taining an abundance of food fish the lampreys. multipled very rapidly. any fish attacked by lamprey bl ed to dteatbj (Lennon, 1954; Harland tr • and Speaker, 1056) (See also pages leure sek The Fisheries Institute at Ann Arbor han been mostly-responsible or the development of control methode. These have been electrical barriers mostly electrical nets (Cool Electric -.Co., Chicago). • With the aid of these nets the passage of. the lampreys to the spawn- • ing beds were blocked. From 1954-56 the number of lampreys caught in these • barriers rose from 5 to 16 thousand. Chemical control of the lamprey populations: Out ot 4346 tested Chemicals only eight showed any specific action and of these two wore onlylleacticable.. • • E. REASONS FOR TkIE DECLINE OF LAMPREY POPULATIONS IN CENTRAL EUROPE It has been often mentioned that lamprey populations in Central Europe have been declining for. the pst 70 years. An especially merked decrease has occurred in the drainage area of the Rhine, the Weser, tho Elbe, the Oder and the Vistula. Tho river lamprey Lampetra fluviatilis and the brook lamprey Lampetra planeri occur in the same numbers. Even the Danube lamprey (Eudontomyzon danfordi) has become rare. On the other hand, the populations in the rivers of the Mans und the tributaries of the Deltic Sea, apart from temporary zetbacks, have maintained a constant level. The best indication of the decreasing population in river systems is given by the collapses of lamprey fisheries in Central Europe. Even in 1024 Menkowski reported that, in districts where the harvest of lampreys as high--the Prische leaf nnd the :Vistula Delta--lamprey fishing was no longer profitable. Many fishermen were forced to give up their trade. Buchho1z(reporte4(103 that the catch of lampreys in the last four p.342 years in Passarge had markedly decreased. Many other authors made similar observations. In Germany today there are no registered lamprey fishermen and lamprey are caught accidentally in eel traps. The decline of the lamprey fisheries is due, in the eirst place, to the progressive development of industry which may be traced back to the pollution of water. .Although it vas first of all assumed that lamprey and their larvae were very sensitive to Chemicals, the work in North America has shown the contrary. ' Migrating river lamprey are able to pass through heavily polluted stretchee of the river. Only in , • certain places would pollution play an important role in limiting the 432- • spawning grounds. Since the passage oe migration consista of flowing :waters only a similltaneous oiling of the passage would have any serious 'effect on the lamprey (Bahr, 1952). • However, sewage bas other effects of the spamning grounds (Sterba, . 1953). The egga which are stirred into the sand and the.larvae which prefer muddy strenm bottoms are very-much influenced . by the presence of even slight impurities. The enrichment of components of sewage on the bottom of the stream, i.e., the environment of the larvae and embryonal lampreys, menns that even night pollution may destroy the population. Poisonous components of sewage, although present in great dilutions, may be concentrated in the etream deposits and exert direct lethal effecte. The accumulation of non-poisonous substances further limit the possibilities because of the products of decomposition. Finally it must be remembered that the larvae are filter feeders and would ingest small organisms living in the sewage sediments. In this way they would indirectly consume the components of the sewage. In addition to the destruction of larval. lamprey populations by sewage other factors have surely played their part in the decline of . lamprey populations in Central Europe. Thus impoundments und river imr. provements can exert an influence. 'According to Buceolz (1933) climatic influenees, changes in water courses and alterations in currents of the Baltic Sea could play a part. The fishermen of the Elbe attribute the decline to the low water levele. UnfortunateIi'our concept that the catadromous and anadromous ..populations of the river lamprey aro the same is in no'way supported. .The ql0 • -133- large numbers of lamprey caught in ' the estuary of the Maas and in the estuaries of the river flowing into the Baltic eoa l ads to tho thought that part of the parasitic lamprey'of the contral European area migrate . to these areas. • AU the factors mentioned above may because of their dependence on local circumstances have more or less contributed to the confinement of tho originally large populations of lampreys . and be threatening the • • residue of this population.' • • • F. ARTIFICIAL P&OPACATION AND REAUN0 or LAMPREYS In areas where lampreys are of commercial importance attempts have been made to encounter the progressive decrease in lamprey stocks by p.343 planned studios the culture lampreys. According to a report from the Fishery Institute in Leningrad, river lamprey have been roared with great success. Even in the region of the Caspian Sea and the lower Volga, according to NikolskiA.lampreyi breeding stations have arisen, since impoundments in the Volga have blocked the migration of the Caspian lamprey. Lamprey may, ea Bahr (1953) has stated, be stripped of their sexual products. Sexual mature animals release their sexual products out of the urinogenital papilla when stroked lightly from the front to the back. The animals are best held firmly with a moist cloth. As in trout culture it is preferable to add the mut to the eggs, mix the two carefully with a in bruah and then add water. Artificial fertilization Is a valuable aid especially in cross-breeding. For successful rearing running water is necessary. - N Ammocoetes may be reared in captivity for long poriods. In excepty:ional instances the specimens have been reared from tho egg to getamorphosis. In culturing the larvae large aquaria kept in a cool place are re- ' -quirod. The substrate should consist of the bottom material collected ' from the natural habitat where the larvae were captured. This ooze-sand mixture is spread to a depth-Of 5 - 10 cm. Cood *oration is essential. Still botter'is water circulated by a pump. They may be fed suspensions o£ diatoms, powdered nettles, oatreal, blood or yeast. In addition, small pieces oe liver or earth worms may als0 be sprinkled into the water. -135- The imagos of non-parasitic species may be easily held when are offered hiding places in the form of rocks. Spawning in captivity Is . favoured by the provision of strong water currents and sunshine. Imagos of parasitic. species may be hold only nfter the feeding period. (i.e., pro and spawning period.) Even with those, spawning.is encouraged by a gravelly bottom, circulating water and sunshlno. Bahr has reported ; ■ on the holding of lamprey during the feeding period. Detailed information on the holding of lamprey in captivity will be found by consulting Tagliani (1940), Bahr (1925b); Storba (1953),•gage1in ,and Steffner (195S), Uagelin (1959), and Schr611.(1959).. . ! • gle G. IIISTORY OF XE STUDY OF LAMPREYS AND THE ORIGIN OF THEIR NAMES Even at the time of Aristotle information on lampreys was available. The Roman naturel scientific writers, notab/y Strabo and Pliny concerned themselves with the details o2 those animais without arriving at any logical account. Up to the sixteenth century the concepts of the . classical period were retained almost unchanged. In the sixteenth century the nomenclature A. changed rapidly, _ because of the studies of Bellonius (1551), Rondelotius (1554), Selvianus (1554), Cleaner (1552), and Aldrovandus (1630. Gesner distinguished sea and river lampreys nn qdesignated these species as anadromous migratory fish. Rondeletius mentioned the stationary brook lamprey which later Bloch (1784) described anew. The systematic position of the lampreys remained next, as will be shown, rather uncertain. Aristotle 'e 384-322 B.C. "Shark" Strabo • 63-1D B.C. • . '"Leech, with gill openings" ■ ; GeSner 1553 ■ ."Shark" . Rondeletius 1554 ' °Cartilaginous fish" ' Aldrovandus 1638 "Murnenentt Linnaeus 1758 2 Amphibia nantes It was in the nineteenth century that, notably the work of Rathke, Rotzius and Johannes Mueller, established the proper place of lampreye in the animal kingdom and eonfirmed their relationship to the Myxinidae. The value of individual characteristics was over-emphasized so that the grOUP acquired a variety of names: Cyclestomi, Hemicraniota, Marsipobranchii Dermopteri, Monorhina. The systematic significant characteristics were, 1111 however, established. DUE DATE -137- • The histological and anatomical .v.rork vih the first half of the nineteenth century exte. century. However, not much work was done on of lampreys was extended only in recent years classical antiquity and in the Middle Ages thd Mustellae Mustela (Ausonius, 400; • Bollonius, to Gesner stems from the resemblance of the col A that of a weasel. Lampetra (Hondeletius, 1554) lambendis petris" (literally, stones which they come from "apyronos" (without spines). The namm error in writing which has been preserved, in the Printed 201-6503 In USA found a place in German commercial usage as "Laml The name Petromyzon was introduced by Artedi (1738) and means "stone • sucker." The old Uigh German "niunougha" became in middle High Gorman Niunougo and finally Neunauge. This name occurs in the sumo sense in other lang- uages: nine-eyers (England), Minoga (U.S.S.R.), negenoog (Holland), nojonoga (Sweden). In general these names refer to the gill peuches which were early considered to be eyes. Thus, gill pouches (7), eye itself (1), re median nostril (1),-and all considered to be eyes-'-an explanation, in my a : A • opinion, which is not satisfactory. Peculiarly the Japanese call the Petromyzontida "Nawayatsume", i.e., river eight eyos (according to Lanxing, 1959). The other Gorman apellation "Pricke" is derived from "geprikt" (prickod),Caartinet, 1778), wirich refers to rows of hole-like gill pouches.' • •