Geographical variation in Cavolinia Tridentata

(, Pteropoda)

by

S. van der Spoel

Institute of Taxonomie Zoology, University of Amsterdam, The Netherlands

Abstract pedition respectively.

At the time five forms of C. tridentata A redescription is given for five formae of Cavolinia are de-

to tridentata and four formae new science are described. scribed, viz.: formatridentata (MS. Forskâl) (Nie- The distribution of the is given and the zoogeo- buhr, 1775) from the Mediterranean, forma kraussi graphy of the formae is discussed. Tesch, 1913 from the Southern Atlantic and South-

ern Indian Ocean, forma occidentalis (Dall,

1908) from the North Pacific, forma platea Tesch, INTRODUCTION 1948 from the Malayan waters and the forma

affinis (d'Orbigny, 1836) from the East Pacific Studying cavoliniid pteropods it seemed neces- Ocean. The forma bermudensis from the Western sary to change existing views on the variation in Atlantic, the forma dakarensis from the North- Cavolinia tridentata (MS. Forskâl) (Niebuhr, eastern Atlantic, the forma atlantica from the 1775). Southern Atlantic and the forma danae from the

Forskâl (spelling: Forsskâl according to Wolff Indian Ocean are described as new to science in (1968)) is usually considered the author of this taxon. the present paper. Moreover, it proved to be In this my opinion is incorrect since Petrus Forskâl, the for the justified to propose new name teschi according to Wolff (1968), wrote only a manuscript forma first named consisting of 1800 loose leaflets which had been sent platea.

back from the Danish Expedition to "Arabia Felix"

(1761 —1767). Wolff (1968) supposed that Niebuhr is

not the actual author either but only the editor, while ACKNOWLEDGEMENTS

another expert, probably Johan Zoëga, made the

manuscriptready for publication. The author wishes to acknowledge the kind aid of Dr.

to author and of C. F. E. from the United States National Reference original year publica- Roper Museum,

tion is not D.C. who collected also of the only of administrative value but also an Washington part material,

indication of the expert responsible for the descrip- and of Dr. J. Knudsen from the Zoological Museum at

who tions as finally published; therefore it is proposed to Copenhagen made the Dana collections available.

maintain the citation mentioned above. Niebuhr was Thanks are also due to Dr. H. Janus from the Staatliches

the only man to survive the expedition, who took Museum für Naturkunde at Stuttgart, Dr. A. Zilch from

for the the the the at responsibility material, notes, manu- Forschungs-Institut Senckenberg Frankfurt, Mrs.

scripts, and for the final publication of this and other A. H. Testud from the Muséum d'Histoire Naturelle at

works by Forskâl. Since it is unknown who made the Paris, and to Mr. L. A. van der Laan who made the

selection from the 1800 leaflets for the manuscript photographs.

which and changes, if any, were made in editing, it

seems not correct to consider Forskâl the only sci-

entist responsible for the final descriptions. ZOOGEOGRAPHY

The majority of the material used in this study In fig. 1 the distribution of C. tridentata is given was collected by the United States National Mu- together with the eleven faunal centres (indicated seum at Washington D.C. in the Atlantic Ocean and MediterraneanJ and in the Indo-Pacific ) *) This material was collected by the Ocean Acre Pro-

2 of Oceans ). Additional material was available from gram the U.S.N.M. supported by funds from the U.S. Navy. the Zoological Museum at Copenhagen and the In- 2 ) Study of this material in the collections of the stitute of Taxonomie Zoology at Amsterdam, col- U.S.N.M. was made possible by funds of the U.S. lected the Dana Expeditions and the by Siboga Ex- National Science Foundation.

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which will be discussed below. real by roman numerals) pling rather than to absence, since the south-

From this map it is clear that C. tridentata is a ern populations from the Indian and Pacific

of warm and transitional absent in Oceans resemble each other Geneflow species waters, very closely. cold in waters and rare halostaze centres. Though between the two southern populations seems to

in its distribution, is exist and is cosmopolitan discontinuity not interrupted by a real gap in dis-

obvious. The absence of the species south of the tribution.

Australian continent seems due to insufficient sam- The isolated population in the North Atlantic is

Distributional for tridentata Fig. 1. map Cavolinia with the eleven faunal centres indicated by roman numerals. The

numerals in indicate the localities from which material is studied and refer the numbers squares to of the centres (cf. list The numerals indicate page 103). the forma.tridentata (1), bermudensis (2), dakarensis (3), atlantica (4), kraussi

(5), danae (7), teschi (8), affinis (10) and occidentalis (11).

2. Distributional Cavolinia tridentata water Fig. map for (cf. fig. 1) with the movements in the distributional areas and, thick the of and in the arrows, transport specimens genes between different centres.

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VIII here. in all probability an instable population developing sentatives of the centre are also met from time to time by migration of from Probably with the Equatorial Counter Current and the central Atlantic. Schiemenz (1906) described the northern parts of the West Wind Drift, trans-

of the this is an uninterrupted distribution species from port of populations towards area possible

the In 60°N to equator. my opinion, however, (fig. 2). Albatross and the self-supporting isolated faunal elements are not to Material from the Expeditions be expected in the faunal centres VI and IX. original material described by Dall (1908; 1921) in the The populations around the southern islands of proved that the forma occidentalis occurs

mentioned Japan and around the Galapagos Islands take an faunal centre XI. This forma is not by isolated position. Still they are not considered as McGowan (unpubl.), in all probability he consid-

faunal elements. The south ered forma with the forma separate populations this synonymous de- forma of Japan are in all probability related to, or affinis. Tesch (1904) did not mention the scending from the faunal centre VIII while the occidentalis either, which seems logical as only the same is assumed for the populations around the forma teschi (see below) is found in the Indo-

Galapagos Islands. Specimens studied from both Malayan waters. But the forma affinis is given by

inves- in areas do not differ in characters from those Tesch (1904) as occurring the Indo-Malayan tigated from the faunal centre VIII. Archipelago. The specimen considered by Tesch

Truly different, self-supporting and rather isolat- to belong to the forma affinis and collected at Si-

faunal elements found in the is reexamined and ed are centres I, II, boga station 116 it proved to

III (with VI), IV, V (with IX), VII, VIII, X and resemble most the forma occidentalis. The occur-

XI. These faunal centres are considered hydro- rence of this forma at 00°58.5'N 122°42.5'E (Si-

due graphically determined areas where special plank- boga sta. 116) is exceptional, probably to trans- tonic faunas and where the the Pacific Currents. occur existing species port through by Equatorial have developed special formae, as representative In the present study the formae occidentalis and

forma elements of these faunas. Between the centres, affinis are both considered valid. The affinis

interbreed and discussed areas are found where the formae and as described by d'Orbigny (1836) by merge gradually into each other. Boas (1886) consists of the two formae mentioned.

Concerning the Northern and Eastern Pacific, The most typical difference between affinis and

is of the caudal McGowan (unpubl.) stated: "The indications are, occidentalis not the curvature spine from the SIO-POFI data that C. tridentata var. as described and pictured by Boas (1886), but it is

less affinis is the commonest form present in the formed by the greater average size and the surface in Eastern North Pacific. However, it seems possible perfect round shape of the ventral

is that these varieties are merely growth stages since affinis. The original description by d'Orbigny there is size increase and of with shell in- a regular gradation based on a specimen the embryonic

which form from one (var. platea) to the other (var. affinis tact, and it is only this embryonic shell

is normal for both and var. kraussi) and populations of var. kraussi strongly bends dorsad, which did in formae occidentalis and occur areas where var. affinis were caught the affinis. at neighbouring stations". The populations of Indo-Malayan waters are

McGowan (unpubl.) was correct when consider- clearly separated from the otherPacific populations.

Pacific has led sub- ing the var. platea a mere growth stage. Tesch Microevolution in the not to

described (unpubl.; 1948) this variety from Malay- species formation as the mixture of populations by an, Indian and Pacific waters but it occurs also currents is still too intensive, but the differences

than in the Atlantic; and it is the growth stage of this between the Indo-Pacific formae are greater species which I (van der Spoel, 1967; 1970) called those between the Atlantic formae. the minute stage (fig. 5k). It should be mentioned Representatives of the Atlantic and Indian Ocean that McGowan did not distinguish between the have incorrectly been considered always to be formae the Mediterranean The occidentalis and affinis. From the area of identical to form. popula- centre IX, Dana material and material of the col- tions from the southern oceans, found in the cen- lections of Dall were studied, which proved the tres V and IX, consist of the forma kraussi, and kraussi in but forma to occur this centre. The forma are usually considered as such; the populations

is a of the Indian Ocean and North Atlantic Ocean affinis typical element of the centre X over-

the IX. differ in size the lapping partly centre This area in the also strongly shape and from

South East Pacific is rather Mediterranean which not complicated as repre- ones, was usually recog-

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nized. The first who recognized differences be- does not make it easier to identify specimens but

Indian Ocean studies the be tween Atlantic and populations was more accurate on biology can exe-

Fryer (1869). The zoogeography and description cuted with this more accurate subdivision of taxa.

which For of the three species are recognized by Fryer the forma concept one is referred to van der

to be here. In are, however, too vague reproduced Spoel (1971). In this the synonymy to the formae the names used by paper the name teschi is proposed for the

where The Medi- Fryer (loc.cit.) are given possible. Indo-Malayan populations replacing the name

terranean populations show special characters, platea, though the growth stage mentioned by

Tesch which is explained by the isolated character of (unpubl.; 1948) is undoubtedly a young stage

the of the forma The this ocean basin. Less easily explained are living there. name given by

differences between the faunal elements of the Tesch is to be considered a nomen nudum as it is

centres II, III and IV. These centres are not at not accompanied by a description in the 1948 pub-

all isolated. The coincide with the lication. centre IV may

South Atlantic halostaze limited in the north by Affinis and kraussi are treated in the present

formae the Equatorial Current and in the south by the paper as though they do sometimes occur

Tropic Front. Probably different ecological selec- sympatrical as stated also by McGowan (unpubl.).

for the differences But when tive pressures are responsible they actually occur sympatrically they

show between the populations in the areas II and III. interbreeding as indicated by the high num-

An indication for clinal variation is not found in ber of intermediates. In some samples I found two

formae the North Atlantic; therefore the ecological or together without their intermediates but

these are from hauls climatological influences could not be traced. samples always open net from

The special characters of the forma living in greater depth.

Most of the faunal centre VII can be explained by the relatively iso- centres and their populations

lated need detailed than position of this warm water centre separated a more study is possible at this

land from the other but few remarks be by warm water areas. The only moment a can made already. The C. contact with other representatives of the present "typical" tridentata form is considered re-

species of this faunal element is formed by the stricted to the Mediterranean; Cavolinia tridentata

forma kraussi from transitional waters. was originally described from material collected in

the Mediterranean. The forma kraussi shows not

only interbreeding with the forma affinis in the Pacific as mentioned, but also with the forma at-

The total number of different formae which lantica in the Atlantic and with the forma danae

in the may be recognized in C. tridentata is nine, viz.: Indian Ocean. Populations in the Caribbean

Cavolinia Sea tridentata forma tridentata near 10°N show strong influences of the for-

from faunal centre I ma atlantica. Consequently strong interbreeding Cavolinia the tridentataforma bermudensis among formae bermudensis and atlantica is to

from faunal II be which be centre expected, may explained by a trans-

Cavolinia tridentata forma dakarensis port by Equatorial Currents of the latter forma. The

from forma dakarensis faunal centre III (and VI) may show in the periphery of its

Cavolinia tridentata forma atlantica range a gradual changeover into the formae atlan- from faunal centre IV tica and bermudensis. A clear interbreeding be-

the Cavolinia tridentata forma kraussi tween formae tridentata and dakarensis is not from faunal V the centre (and IX) expected at moment because a changeover

Cavolinia tridentata forma danae between the two could not be demonstrated. The from fauna! centre VII contact between the faunal centres V and IX and

Cavolinia tridentata their is forma tesc hi populations already mentioned.

faunal The forma from centre VIIT occidentalis from the faunal centre

Cavolinia tridentata forma affinis XI shows a clear affinity to the forma affinis from from faunal centre X faunal centre X. From a morphological point of Cavolinia tridentata forma occidentalis view one should be inclined to consider the forma from faunal centre XI occidentalis as a forma of Cavolinia uncinata

idea (Rang, 1829), an already given byTesch (1904). The description of these infra-subspecific taxa The formae affinis and teschi however, constitute

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other clear intermediate forms to the representa- formae viz.: atlantica, bermudensis and dakaren-

of C. tridentata. tives sis, an Indian Ocean group of two formae viz.:

danae and teschi of which teschi is also found in The forma teschi penetrates the East Pacific the Pacific and an endemic Pacific group com- north of 25°S and interbreeds there with the forma posed of affinis and occidentalis. affinis and kraussi which gives the teschi popula- Size differences between the formae are not of tions of 180°W another than those east appearance discriminating value. The formae bermudensis, from the Indo-Malayan waters but there is no teschi, danae and kraussi are of an average size, reason to distinguish between eastern and western the forma dakarensis is the largest forma while the teschi populations as a boundary between the two formae tridentata, atlantica, occidentalis and affinis is absolutely absent. Closely related to teschi is the constitute of smaller a group types (fig. 3). Clinal forma danae from the Indian Ocean, though fre- variation in size, however, is not concerned. In fig. is be the dis- quent interbreeding not to expected as 2 the distribution of the formae is given with pos- tribution is discontinuous. Contact of the forma sible movements of specimens in between the cen- danae with the forma atlantica south of the Afri- indicated thick tres by arrows. Water current pat- can continent is at least restricted as the forma terns in the area of distribution are given with thin kraussi has its northern limit north to the Cape of arrows. From this map it is clear that exchange of Good Hope. and specimens, as a consequence of genes, may

From the above exist between all the faunal This mentioned relations one can centres. explains

conclude that there are two clearly separate formae the great resemblance between the formae and the

within kraussi and tridentata, an Atlantic group of three identity populations.

Fig. 3. Length-width relation for Cavolinia tridentata forma tridentata (1), forma bermudensis (2), forma dakarensis

(3), forma atlantica (4), forma kraussi (5), forma danae (7), forma teschi (8), forma affinis (10) and forma occiden-

talis (11) in mm.

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forma bermudensis forma. DESCRIPTION OF THE FORMAE OF Cavolinia tridentata n.

CAVOLINIA TRIDENTATA Figs. 4d; 6a.

In the respective lists of material the localities Synonymy for measured are given only or figured specimens, This forma is usually named C. tridentata in previous

while in fig. 1 all identified material is represented works or considered to belong to the typical subspecies

forma as it has been as a separate used in the lists below or never recognized by a square. Abbreviations forma. are U.S.N.M. for United States National Museum Material the at Washington D.C., Z.M.U.C. for Zoological Off Sambo Reef, Fla. (U.S.N.M. 357035); Albatross Museum at Copenhagen and Z.M.A. for the In- sta. 2385 (U.S.N.M. 614075); off Pelican Isl., Barbados of Taxonomie stitute Zoology at Amsterdam, (U.S.N.M. 502290); Barbados (U.S.N.M. 199037); off

while Med. stands for the Mediterranean cruises Havana, Cuba (U.S.N.M. 199041); several stations off

Bermuda made during the Ocean Acre Program (U.S. executed in 1971 by the U.S.N.M. N.M.); George Banks (U.S.N.M. 52104); Gulf of Mexico

(U.S.N.M. 223656); 27°20'N 51°54'W (Dana sta. 1325 Cavolinia tridentata forma tridentata III, Z.M.U.C.).

(MS. Forskàl) (Niebuhr, 1775).

Figs. 4a;6c. Description shows The hyaline or opaque shell a slightly Synonymy vaulted dorsal surface, with moderately or even Monoculus telemus Linnaeus, 1758: 635; Anomia tri- poorly developed ribs. The dorsal lip is separated dentata (MS. Forskâl) Niebuhr, 1775: 124, 1776: pl. 40,

from the dorsal surface a well developed arch- figs. B, bl, b2; Cavolinia natans Abildgaard, 1791: 175; by Cavolinia tridentata (part) Philippi, 1853: 290; Hyalaea shaped rib. In ventral view the lateral margins of Cavolinia tridentata tridentata (part) Fryer, 1869: 266; and form smooth regular upper lip shell-body a forma tridentata (part) van der Spoel, 1967 : 94, fig. 89. line without clear incisions near the base of the

Material is rounded. The dorsal lip. The upper aperture lip 40°32'N 12°28'E (Med. 3—20 M, U.S.N.M.) (fig. 4a); lateral sides show no keels and the lateral spines 40°23'N 12°43'E (Med. 3—24 M, U.S.N.M.); 40°26'N do not caudad. The caudal is 12°33'E (Med. 3—18 P, U.S.N.M.); 40°27'N 12°52'E project spine straight,

(Med. 3 —3 B, U.S.N.M.); Napels (coll. Schepman, while the shell margins between the caudal and lat-

Messina Z.M.A.); (Z.M.A.). eral spines are composed of a concave and a

straight section. The ventral side is moderately Description vaulted. The has The The shell of nature is aperture a triangular shape. hyaline or opaque triangu- shell structure consists of tiny transversal ribs and lar in ventral view, showing a relatively flat, dorsal invisible lines. The whole shell is surface with moderately developed dorsal ribs. The nearly growth yel- lowish-brown in colour. The shell length varies dorsal lip is separated from the dorsal surface by

between 12.0 and 19.5 mm, while the width varies a prominent arch-shaped rib between the aperture

between 9.5 and 13.5 the are 15.8 closing mechanisms. The dorsal lip is rounded and mm, averages and 10.2 mm respectively. sometimes even pointed, so that the aperture is Range triangular in shape. Lateral sides show no keels.

The lateral The forma occurs in the North West Atlantic spines are directed sligthly caudad. The (centre II). Type locality: Off Martha's Vingard, shell margin between caudal and lateral spines is U.S. Fish. Com. sta. 876. The holotype (U.S.N.M. regularly concave. The ventral surface is vaulted. 38334) (fig. 4d) is kept dry in the United States The structures on the shell consist of clearly de- National Museum, together with four (U.S.N.M. veloped transversal ribs and faint growth lines. The

703761, 703762, 703763, 703764) paratypes, one shell shows a chestnut brown colour over its entire paratype is kept in the Institute of Taxonomie surface. The shell length varies between 10.0 and at Amsterdam. 18.0 mm, its width varies between 7.5 and 11.5 Zoology

the mm, averages are 11.2 and 8.5 mm respective- Cavolinia tridentata forma dakarensis forma. ly. n.

Range Figs. 4b;6b.

This form is endemic for the Mediterranean Synonymy (centre I). Type locality: The type material could This forma is usually referred to as Cavolinia triden- not be traced. The species, and this forma is orig- tata in previous works. Hyalaea tridentata (part) Fryer, described from the Mediterranean. inally 1869: 266, fig. 1.

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Material rib on the dorsal side is well developed, the lateral Atlantic (U.S.N.M. 127281); 29°13'N 14°42'W (Dana ribs are much less developed. A well developed sta. 4017 XI, Z.M.U.C.); 28°09'N 15°19'W (Dana sta. arch-shaped rib is found at the base of the dorsal 4014 IV, Z.M.U.C.); 34°15'N 16°52'W (Dana sta. 1141 lip. The lateral sides are not with keels. IV, XVI, XX, Z.M.U.C.); 31°30'N 12°12'W (Dana sta. provided The lateral 4018 n, Z.M.U.C.); 30°17'N 20°44'W (Dana sta. 1152 spine points are directed slightly cau-

V, Z.M.U.C.). dad, the caudal spine is short and straight. The shell

margin between caudal and lateral spines is con-

Description cave with a more or less straight horizontal section.

The sometimes shell The ventral side is usually hyaline or opaque moderately vaulted. The aper-

rather flat dorsal surface with is in The dorsal shows a moderately ture triangular shape. aperture lip

ribs. The dorsal is from is rounded it be with small ad- developed lip separated or may provided a

ditional the dorsal side by a moderately or poorly develop- part with a short straight section of about ed arch-shaped rib between the closing mecha- 3 mm length. The growth lines on the shell are

and nisms. The lateral sides have no lateral keels, faint and the transversal striation on the shell is

and forms the margin of upper lip shell-body an poorly developed. A light-brown hue covers nearly

irregular line by the incisions at the base of the the whole shell. The shell length varies between

lip. This dorsal lip is truncated so that a more or 11.5 and 16.0 mm, the width varies between 8.0

of about and less straight upper border 4 mm length 10.5 mm, with averages of 15.2 and 9.9 mm

is found. The aperture is irregular, triangular in respectively.

shape. The caudal spine is straight and relatively Range

This forma in the Southern Atlantic be- long. The lateral spines curve caudad. The margin occurs of the shell between the caudal and lateral spines tween 5°N and 40°S (centre IV). Type locality: St.

shows and The ventral coll. Turton. The a concave a straight part. Helena, holotype (U.S.N.M.

side is moderately vaulted. The structure on the 123920) (fig. 4c) and one paratype (U.S.N.M.

is in the United National shell consists of faint growth lines and a very 703765) kept dry States

faint transversal striation. The yellowish-brown Museum, one paratype is kept dry in the Institute

of Taxonomie hue over the shell is less intense on the dorsal lip Zoology at Amsterdam. and along the lateral sides. The shell length varies between and width varies be- Cavolinia tridentata forma kraussi 1913. 14.5 21.5 mm, the Tesch,

tween 9.5 and 14.5 mm, the averages are 16.9 and Figs. 4e; 6f.

11.4 mm respectively. Synonymy Range Hyalaea truncata (non Lesueur, 1821) Krauss, 1848: This forma occurs in the Northeastern Atlantic 34, pl. 2, fig. 12; Hyalaea teniobranchia (part) Fryer, (centres II and 32°55'N VI). Type locality: 21°51' 1869: 266, fig. 2; Cavolinia tridentata kraussi Tesch,

W, Dana sta. 1913: Cavolinia tridentata forma kraussi van der 1148 VII. The holotype and 10 para- 51;

Spoel, 1967 : 97, fig. 94; Cavolinia tridentata var. kraussi types (fig. 4b) are kept in alcohol in the Zoologi- McGowan, unpubl.: 129. cal Museum 2 at Copenhagen; paratypes are pre-

Material served in the Institute of Taxonomie Zoology at 40°00'S 30°35'W; 39°53'S 21°33'W; 40°35'S 09°57'W; Amsterdam. 40°34'S 09°50'W; 40°03'S 07°30'W; 40°02'S 07°28'W;

40°01'S 07°25'W; 38°06'S 01°12'E; 34°25'S 14°47'E; Cavolinia tridentata form atlantica n. forma. 24°22'S 00°29'E, Walter Herwig Exped. 1971, sta. 371 II,

Figs. 4c; 6i. 380 m, 399 II, 402 I, 402 II (fig. 4e), 402 III, 409 I, 419 I and 439 I respectively (U.S.N.M.); 33°36'S 179°

10'W (Dana sta. 3629 I, Z.M.U.C.); West of Tristan da Synonymy Cunha (Z.M.A.). This forma is usually named C. tridentata in previous

works. Description Material The hyaline or opaque shell shows a slightly South Atlantic (U.S.N.M. 127289); 5°S 20°W (U.S. vaulted dorsal surface with three well developed N.M. 169292); 40°S 30°35'W (Walter Herwig Exped. ribs and two less prominent ribs along 1971 sta. 371 II, U.S.N.M.). longitudinal the lateral sides. The dorsal aperture lip is separat- arch- Description ed from the dorsal side by a prominent

The less The hyaline or frequently opaque shell shows shaped rib between the closing mechanisms.

vaulted surface. central is a moderately dorsal The aperture lip strongly truncated, usually even

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Shell showing two anterior projections. The lateral sides ed over the shell. length varies between 12.0

keels and 16.0 and width varies between 8.0 and are provided with strong side composed by mm with of 14.8 and 9.5 thin "wings" of the ventral and the dorsal shell 10.5 mm, averages mm re-

directed surface. The lateral spine points are cau- spectively. dad. The caudal spine is straight. The shell margin Range between the caudal and lateral spines is irregularly This forma is endemic in the Indian Ocean north

of 25°S 14°16'S 41°48' concave. The ventral side is strongly vaulted. The (centre VII). Type locality:

The Dana 3951 IV. The shell aperture is trapezoid in shape. structure E, Exped., sta. holotype (fig.

is in alcohol in the Museum at on the shell consists of growth lines and transversal 5f) kept Zoological

two in alcohol ribs on the ventral side which are very variable, Copenhagen, paratypes are preserved

sometimes faint. The in the Institute of Taxonomie Zoology at Amster- sometimes they are coarse, dam. colour of the shell consists of a brown to dark- brown or purple pattern over the ventral and dor-

Cavolinia tridentata forma teschi n. forma. sal side. The dorsal aperture lip is always lighter in colour and the lateral keels are whitish. The Figs. 5g, j, k; 6d.

the shell length varies between 10.5 and 16.0 mm, width and 10.5 with Synonymy varies between 8.0 mm, aver- Hyalaea affinis (non d'Orbigny, 1836, non Sowerby, of 13.3 and 10.2 ages mm respectively. 1878) (part) Fryer, 1869: 262, 266, pi. 21, fig. 3; Cavo- Range linia tridentata platea (part) Tesch, 1948 : 25, fig. 21 This forma in the Subantarctic waters of occurs E—F; Cavolinia tridentata forma platea (part) van der

Atlantic, Indian and Pacific Oceans (centre V and Spoel, 1967 : 96, fig. 93; Cavolinia tridentata var. platea

MeGowan, 129. IX). Type locality: Vals Bay (South Africa). The (part) unpubl.: type material, formerly kept in the Staatliches Mu- Material seum für Naturkunde at has been lost Stuttgart, Ally Isl. Ujae Atoll (U.S.N.M. 607392); 7°24'S (Dr. Janus in lit.). 118°15.2'E (fig. 5j); 52.9°S 119°56.7'E; 0°34.6'N 119° 8.5'E; 5°43.5'N 119°40'E; 6°11'N 120°37.5'E; 2°40'S

128°37.5'E; 5°39'S 122°12'E; 6°24'S 124°39'E; Banda, Cavolinia tridentataforma danae n. forma. Siboga sta. 45, 52, 88, 95, 100, 178, 208, 221 and 240 Figs. 5f;6e. respectively (Z.M.A.); 3°40'30"N 137°53'E (Dana sta.

3751 III, Z.M.U.C.) (fig. 5k). Synonymy This forma is usually named C. tridentata in previous Description works and Tesch (1948) probably used var. platea for shell shows rather flat The hyaline or opaque a part of this taxon. Hyalaea affinis (non d'Orbigny, 1836, dorsal surface with slightly developed longitudinal non Sowerby, 1878) (part) Fryer, 1369: 266.

ribs. The dorsal aperture lip is separated by a mod- Material arch between erately developed rib forming an Gulf of Bengal (U.S.N.M. 12726); Indian Ocean the closing mechanisms of the aperture. This dor- (U.S.N.M. 127290; this sample shows some characters of the next forma). sal aperture lip is rounded, only in some of the

older specimens provided by a small additional

Description part giving rise to a truncated part with a straight

The shell is with rather flat The lateral sides have hyaline or opaque a margin of only about 3 mm. dorsal directed surface, provided by nearly invisible longi- no keels, the lateral spine points are cau- tudinal ribs. The dorsal lip is separated from the dad. The caudal spine is straight and the shell dorsal side by a very flat but distinct arch-shaped margin between this spine and the lateral spines is rib. lateral The sides have no keels, the lateral spine concave. The ventral side is moderately vaulted. tops are directed caudad. The dorsal aperture The wide shell aperture has a lunar shape. Growth lip is truncated rise to and the transversal giving a straight upper lines are very faintly developed

of about 4 The caudal striae the ventral side nowhere margin mm. relatively long on are very thin,

is and the shell spine straight margin between cau- disturbing the smooth character of the shell. The dal and lateral The ventral hue spines is concave. colour pattern consists of a yellowish-brown side is moderately vaulted. The growth lines and over the shell, the central parts of ventral and transversal ribs the ventral on surface are not dis- dorsal side are usually lighter than the remaining tinct. The is The colour shell The shell varies between 10.0 aperture trapezoid. pattern parts. length consists of a yellowish-brown irregularly distribut- and 19.0 mm, the width varies between 7.5 and

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4. of shells of Cavolinia tridentata 3 in the dorsal views, Fig. Photographs (magnification X approx.); upper row in the middle row ventral views and in the lower row lateral views of the formae tridentata (a), dakarensis (b), atlantica (c), bermudensis (d), and kraussi (e).

12.0 mm, with averages of 13.7 and 8.9 mm re- To show the development of the shell during its spectively. growth a photograph (fig. 5k) of a young shell,

in minute der Range with an stage (cf. van Spoel,

This forma is found in the and of devel- Indo-Malayan waters, 1967) a photograph (fig. 5j) a more

Equatorial and Tropical Pacific (centre VIII). Type oped but still not yet fullgrown specimen is given. locality: 5°40.7'S 120°45.5'E(Siboga sta. 211). The It was a growth stage like given in fig. 5k on which

and three Tesch holotype (fig. 5g) paratypes are kept (unpubl.; 1948) based the variety “platea”. dry in the Institute of Taxonomie Zoology at Am- Cavolinia tridentata forma affinis sterdam. (d'Orbigny, 1836). Tesch (1948) did not publish a description, Figs. 5i; 6h. and he did as never indicate type material Synonymy the name “plate a”is in fact a nomen nudum. As a Hyalaea affinis (non Sowerby, 1878, non Fryer, 1869) nomen nudum is not available according to the (part) d'Orbigny, 1836: 91 (1846), pi. 5, figs. 6—10; code is the name teschi proposed for this forma Hyalaea tridentata var. affinis (part) Boas, 1886: 116, new to science in honour to the late Dr. J. J. Tesch. 212, fig. 100; Cavolinia tridentata var. affinis (part)

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5. of shells of Cavolinia tridentata 3 in the dorsal Fig. Photographs (magnification X approx.); upper row views,

and the lower lateral views of the formae danae teschi occidentalis in the middle row ventral views in row (f), (g),

(h), affinis (i), early adult stage of teschi (j), and the minute stage of teschi (k).

Tesch, 1904: 39, pl. 2, fig. 32; McGowan, unpubl., 129; formae though it occurs always to a lesser extent

Cavolinia tridentata affinis (part) Tesch, 1913: 51, Tesch than in the forma occidentalis. The usually opaque 1948: 25, fig. 21 C—D; Cavolinia tridentata forma affinis surface with shell shows a slightly vaulted dorsal van der Spoel, 1967 : 96. normally developed longitudinal ribs. The dorsal

Material aperture lip is rounded and the lateral sides show 19°37.7'S 108°27.7'W (U.S.N.M. 670196) (fig. 5i). no keels. The lateral spine points are not or only

slightly directed caudad. The arch-shaped rib at

is Description the base of the dorsal aperture lip not as strong

The shell is small in relation to the other formae, as in most other formae. The shell margin between though the average size seems still higher than in the caudal and lateral spines is concave. The aper- the forma The caudal lunar occidentalis. spine is curved ture has a shape. The ventral aperture lip is dorsad in some specimens, but usually the spine relatively small while the ventral side is strongly is and straight projecting a little caudad, so that vaulted. This side is, however, not circle round in its axis makes an angle with the shell axis. This profile view like in the next forma as the greatest oblique position is typical for all the Indo-Pacific shell thickness is found anterior to the middle.

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shell are faint. The ventral is small in Growth lines and structures very part. aperture lip very

The number of transversal striae on the ventral comparison with the other forms. The ventral side

side is The shell colour consists of a is strongly vaulted, in profile view it is very high. perfectly the whole shell. The circle round. has light purple brown hue over The aperture a triangular lunar

shell length varies between 8.5 and 11.5 mm, the shape. The sculpture on the shell consists of growth

few lines and to width varies between 6.0 and 8.0 mm; too up 20 transversal ribs on the lateral

specimens were available to give averages. side. The shell shows only a light brown or yellow-

ish hue colour the and lateral Range pattern, upper lip sides The shell This forma occurs in the Southeastern Pacific are lighter. length varies between

(centre X). Type locality: South Pacific between 7.5 and 11.5 mm, the width between 5.5 and 8.5 with 30° and 34°S and between 80° and 92°E (Paris- mm, averages of 10.3 and 6.6 mm respec-

longitude). The two syntypes are kept dry in the tively.

Museum of Natural History at Paris, the adult Range specimen (11.4 mm length, 7.2 mm width) is in-

the This forma occurs in the North East Pacific dicated as lectotype, young specimen (11.2 38°4'N 137°W, coll. mm length, 6.8 mm width) is indicated as paralec- (centre XI). Type locality:

Dall. The and four totype. holotype (U.S.N.M. 110591) in the The two specimens forming the type ma- paratypes (U.S.N.M. 110590) are kept dry United States National Museum terial are in all probability less "typical" for this at Washington D.C. forma as they are representing intermediate speci-

mens.

Cavolinia tridentata forma occidentalis Dall, 1908.

Figs. 5h; 6g.

Synonymy

Hyalaea affinis (non Sowerby, 1878, non Fryer, 1869)

(part) d'Orbigny, 1836: 91; Cavolinia tridentata var.

affinis (part) Tesch, 1904: 39, pi. 2, fig. 32; McGowan,

unpubl.: 129; Cavolinia occidentalis Dall, 1908: 223, pi.

12, fig. 1; Dall, 1921: 59; Cavolinia tridentata affinis

(part) Tesch, 1913: 51; Tesch, 1948 : 25, fig. 21 C—D;

Cavolinia tridentata forma tridentata (part) van der Spoel,

1967 : 94.

Material

Taka Islet, Marshall Isis. (U.S.N.M. 615457); 40°11'N

125°9'W (U.S.N.M. 253050); S. coast of Oahu; Hawaii

Isis. (U.S.N.M. 334809) (fig. 5h); 00°58.5'N 122°42.5'E (Siboga Exped. sta. 116, Z.M.A.).

Description

The shell is very small in relation to those of

theother formaeof this In species. general appear- ance the specimens resemble Cavolinia uncinata,

though the caudal spine is completely straight. The opaque shell shows a relatively strongly vaulted

dorsal surface with three moderately developed

central ribs and two faintly developed lateral ribs.

The dorsal aperture lip is separated from the dor- sal surface by a prominent arch-shaped rib. The dorsal lip is rounded and the lateral sides show

The lateral Fig. 6. Outlines of shells of Cavolinia tridentata in ven- no keels. spine tops are not or only

tral view made with the camera lucida of the formae slightly directed caudad. The shell margin between bermudensis (a), dakarensis (b), tridentata (c), teschi (d), the caudal spine and lateral is composed spines danae (e), kraussi (f), occidentalis (g), affinis (h), and of a more or less section and straight a concave atlantica (i).

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dorsal is continuous KEY TO THE FORMAE OF aperture lip not

forma teschi CAVOLINIA TRIDENTATA the b) Caudal spine length 1/4 of the distance between sides and lateral spine tops, the outline of lateral The resemblance between the formae great dorsal aperture lip is continuous without interrup-

their identifi- tion forma atlantica makes it necessary to give a key for 7 Ventral side in lateral view perfectly circle round, cation. In fig. 6 the outlines of the different forms a) caudal forma occidentalis spine straight .... seen from the ventral side are given for compari- b) Ventral side in lateral view not circle round but son when the the shell using key. During growth bulging more in cranial direction, caudal spine

remarkable In forma shows two changes. older specimens directed or bended caudad affinis .... the shell is thicker than in the minute 8 spine not curved caudad, or lateral keels younger (Lateral is Se- present see 4) stages so that the shell thickness variable. a) Lateral spine curved caudad, shell larger than 16.5 the continues condly, upper aperture lip growing dakarensis mm forma for a show al- long period. Very young specimens b) Lateral spine curved caudad, shell smaller than 16.5

while older forma danae ways a rounded aperture lip, in speci- mm mens an additional part is formed which tends

be Shell thickness is to more blunt. not used Summary in the key. In point 3 of the key the aperture lip The geographical variation in Cavolinia triden- is given as discriminating character and it should tata is discussed, and nine formae of the species be mentioned that older specimens show some- described are described. The material originally times a small blunt addition to the lip though it is from the Mediterranean belongs to the endemic considered "rounded" in the key. In the formae forma tridentata. The forma bermudensis from the kraussi, dakarensis and danae, however, a large Western Atlantic between 5° and 50°N, the forma blunt, or straight aperture part is found in all dakarensis from the Eastern Atlantic between 5° specimens, whereas the other formae show only a and 65°N, and the forma atlantica from the South- blunt of maximal 3 in small, aperture part mm formae new to ern Atlantic are described as some of the older specimens.

science. In the southern oceans south of about

1 a) Shell triangular in ventral view, dorsal aperture lip 30°S the forma kraussi is found. In the North-

rounded forma tridentata eastern Pacific the forma occidentalis is found and

b) Shell not triangular or without rounded aperture in the Southeastern Pacific the forma affinis is pres- lip 2 known ent. The three latter formae were already 2 a) Shell with keels along the lateral sides their is for forma kraussi but a general picture of distribution

Shell without keels the lateral sides b) along ... 3 the first time given in this paper. For the Indian 3 a) Dorsal aperture lip rounded 4 Pacific Ocean and Indo-Malayan and Central wa- Dorsal with anterior b) aperture lip straight margin or ters two formae new to science are described. In with two points 8 the Indian Ocean the forma danae is found and in 4 a) Shell longer than 13.5 mm 5 the of the for- b) Shell length less than 13.5 mm 7 Indo-Malayan waters a population

5 Lateral not directed caudad a) spine points .... is found which into the Cen- ma teschi penetrates forma bermudensis tral Pacific. Lateral b) spine points directed usually caudad . . 6 between The more or less intensive interbreeding 6 a) Caudal spine length 1/3 of the distance between the is discussed. lateral spine tops, the outline of lateral sides and the formae

LITERATURE

P. 1791. det skal- 1921. of the marine shell-bearing mollusks ABILDGAARD, C., Nyere efterretning om —, Summary

dyr fra middelhavet, form Forskâl har beskrevet under of the North West Coast of America, from San Diego,

navn of Anomia tridentata. Skr. Naturh.-Selsk. Kj0ben- California to the Polar Sea, mostly contained in the

havn, 1 (2) : 171—175. collection of the United States National Museum, with

BOAS, J. E. V., 1886. Spolia Atlantica. Bidrag til Pteropo- illustrations of hitherto unfigured species. Bull. U.S.

dermes. samt 1—22. Morfologi og Systematik til kundskaben natn. Mus., 112 : 1—217, pis.

om deres geografiske udbredelse. Vidensk. Selsk. Skr. FORSKAL, P., see NIEBUHR, C.

6 Raekke, naturv. mathemat. Afd. IV (1) : 1—231, FRYER, G. E., 1869. A contribution to our knowledge of

pis. 1—22. pelagic Mollusca. J. Asiat. Soc. Beng., 38 (2) : 259 —

DALL, W. H., 1908. The Mollusca and the Brachiopoda. 268, pl. 21.

Bull. Mus. Zool. Ein comp. Harv., 43 (6) : 205—487, pis. KRAUSS, F., 1848. Die Südafrikanischen Mollusken.

1—22. Beitrag zur Kenntniss der Mollusken des Kap- und

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Natallandes und zur geographischen Verbreitung der- lusques (1846): i—iv, pis. 1 —85. (Bertrand, Paris; Levrault, Strasbourg). selben, mit Beschreibung und Abbildung der neuen

Arten: i— iv, 1 —140, pis. I—VI. (Ebner & Seubert, PHILIPPI, R. A., 1853. Handbuch der Conchyliologie und

Stuttgart). Malacozoologie: i—xx, 1 —548. (E. Anton, Halle).

1758. tria SCHIEMENZ, 1906. Die der Plankton LINNAEUS, C., Systema naturae per régna natu- P., Pteropoden

secundum II — rae, classes, ordines, genera, species, cum Expedition. Ergebn. Plankton-Exped., (F) (b) : 1

characteribus, differentiis, synonymis, locis. Tomus I. 30, fig. 1, pis. I—III.

Editio reformata: 1 —824. S. 1967. with décima, i—iv, (L. Salvii, SPOEL, VAN DER, Euthecosomata, a group

Holmiae). remarkable developmental stages (, Ptero- MCGOWAN, J. A. (unpubl.). The systematics, distribution poda) : 1 —375. (Noorduyn & Zn., Gorinchem).

and abundance of Euthecosomata of the North 1970. data with notes —, Morphometric on ,

Pacific: 1 —197. (Ph. D. Thesis Univ. of California on a new form of Cuvierina columnella (Rang, 1827)

at San Diego, 1960). (Gastropoda, Pteropoda). Basteria, 34 (5/6) : 103— NIEBUHR, C., 1775 (MS. P. FORSKÂL). Descriptiones 151.

animalium 1971. Some in classification of avium, amphibiorum, piscium, insectorum, —, problems infraspecific

in itinere Orientali observavit vernium; quae Petrus holoplanktonic animals. Zeitschr. Syst. Evol., 9 (2) :

Forskâl. Prof. Haun. Post mortem auctoris edidit 107—138.

Carsten Niebuhr. Adjuncta est materia medica Kahi- TESCH, J. J., 1904. The Thecosomata and Gymnosomata

rina tabula Maris Rubri : —164, of atque geographica 1 the Siboga Expedition. Siboga Exped., LII [16] :

1 map. (Mölleri, Hauniae). 1—92, pis. I—VI.

1776. Icones rerum naturalium in itinere Orien- 1913. 36 1 —154. —, quas —, Pteropoda. Tierreich, : i—xvi,

tali curavit Prof. 1948. The thecosomatous The Indo- depingi Petrus Forskâl, Haun. Post —, pteropods. II.

mortem auctoris ad Regis mandatum aeri incisas Pacific. Dana Rep., V (30) : 1 —45, pis. 1—3.

edidit Carsten Niebuhr 1 XXI—XLIII. and Biol. Res. Snel- : —15, pis. —, (unpubl.). Pteropods heteropods. (Mölleri, Hauniae). lius Exp. (MS.).

ORBIGNY, A. D', 1835—1846. Voyage dans lAmérique WOLFF, T., 1968. The Danish Expedition to "Arabia

méridionale (...), exécuté pendant les années 1826, Felix" (1761—1767). Bull. Inst, océanogr. Monaco.

1832 et V No. 2 int. Hist. 581 — 1827, 1828, 1829, 1830, 1831, 1833, ... (3). spécial [Congr. Océanogr., 1] :

Mollusques: i—vi, i —xliii, 1 —758. Atlas des mol- 601.

Received : 23 May 1973

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