Bijdragen tot de Dierkunde, 60 (3/4) 277-282 (1990)

SPB Academie Publishing bv, The Hague

Comparison of oostegite shapes in some gammaroidean species (Crustacea:

Amphipoda)

D.H. Steele

Dept. of Biology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X9

Keywords: Oostegites, gammaroideans, Crustacea,

Abstract Whilethese revisions have found support, not all

of the changes have been accepted (e.g. Barnard&

Within the superfamily oostegites vary from Barnard, 1983; Barnard & Karaman, 1980; Lin- broad (primitive) to narrow (advanced). Broad oostegites are coln, 1979; Ruffo, 1982; and Stock, 1980). As a found in members of the , Macrohectopi- result, amphipod , especially as it relates dae and a few of the . Most species of the family to the family Gammaridae "is still in a state of Gammaridae have broad anterior oostegites and narrow poste- flux" (Stock, 1980). rior ones. Marine species and Echinogammarus

The of the is resolve show a narrowing trend in the anterior oostegites as well. purpose present study not to

this controversy, since this is probably impossible

given our present inadequate data base, but rather Résumé to illustrate how the structure of the brood pouch

can provide data that will contribute to the resolu- Dans la superfamille Gammaroidea les oostégites varient depuis tion of the problem. ceuxélargis (aspect primitif) à ceux étroits (aspect évolué). Des oostégites larges sont présents chez des membres des familles Oostegites have been recognized as morphologi-

et chez certains Gam- Acanthogammaridae,Macrohectoptidae, cal structures that should be more stable ("change maridae. La plupart des espèces de la famille Gammaridae ont resistant") than the traditional characters of the des oostégites antérieurs larges et des oostégites postérieurs mouthparts, antennae, telson, etc. (Bousfield, étroits. On observe chez les espèces marines de Gammarus et However, I have concluded in chez Echinogammarus une tendance au rétrécissement aussi 1977). (Steele, press)

that the pour les oostégites antérieurs. appearance of the major amphipod super-

families has predated changes in the oostegites,

since several of the superfamilies contain the full

of Introduction range oostegite types. Thus the structure of the

brood pouch should not be used to demonstrate

Prior to 1977, between of gammarid amphipods (family Gam- relationships major groups gammaride- maridae) made up the major portion of all de- an amphipods but may be used to follow trends

within scribed species and generaof amphipods. Bousfield these groups. The present study consists of

revised this and of the structure ofthe (1977) group assigned the species to an analysis oostegites in some six superfamilies, each containing several families. of the species in the superfamily Gammaroidea,

this which Subsequently revision was extended to all gam- prior to 1977 were all placed in the family maridean amphipods (Bousfield, 1979; 1982; Gammaridae.

1983). 278 D.H. Steele - Comparison of oostegite shapes in some gammaroidean species

Methods

Previous characterizationsof the oostegites for tax-

observations onomie have been based on purposes

this is inade- of one or two oostegites. However, quate as the oostegites on adjacent peraeopods can differmarkedly. The oostegites attached to the sec- ond to fifth peraepods function as a unit to form the brood pouch and the structure of all of them must be considered. They are numbered here ac- cording to the peraeopod to which they are at- tached.

The illustrations have been adjusted such that

size oostegite three is of the same on each figure.

Only the basal setae on the anterior and posterior margins and the distal setae have been illustrated.

In order not to prejudge the situation, the "gam- marid" species have been referred to as Gammarus.

A number of other species have been examined which are not illustrated here.

Results

been For comparative purposes, the species have grouped more or less as outlined by Bousfield

(1977; 1982; 1983).

Gammaracanthus loricatus (Sabine, 1821) (Fig.

1A) is here considered to have the most primitive Fig. 1. Oostegites of Acanthogammaridae:A,

and type of brood pouch (see discussion). The ooste- loricatus; B, Garjajewia sarsi; C, Spinacanthusparasiticus; Macrohectopidae: D, Macrohectopus branickii. gites are all broad, with relatively short marginal se- tae thatextend to the base of the oostegite. Gamma-

in racanthus was placed the family Acanthogam- Macrohectopidae, has broad oostegites quite dis- maridae by Bousfield (1977), but the bilobed tinct from those in the Acanthogammaridae. structure of its gills indicates that its affinities prob- The brood pouch of the Gammarus species (Figs. ably lie elsewhere. In the family Acanthogammari- 2, 3, 4) has a combinationof broad and narrow dae the available specimen of Garjajewia sarsi oostegites. The anterior oostegites (two and often

Sowinsky, 1915 (Fig. IB) lacked marginal setae, three) are broad, whereas four and especially five probably indicating ovarian diapause. The ooste- are narrow. The freshwater G. fossarum Koch, gites are similar in shape to those of Gammaracan- 1835, G. minus Say, 1818 and G. roeseli Gervais, thus, except that four and five are more elongated 1835 have oostegites similar to those of G. pulex and five is also slightly narrowed. However, in (Linnaeus, 1758) (Fig. 2A), whereas G. lawrencia-

Spinacanthus parasiticus (Dybowsky, 1874) (Fig. nus Bousfield, 1956, G. fasciatus Say, 1818, G.

1C) of the same family, the oostegites are similar to locusta (Linnaeus, 1758), G. crinicornis Stock, those of the freshwater Gammarus (Fig. 2). 1966, G. duebeni Liljeborg, 1852, G. salinus

branickii Macrohectopus (Dybowsky, 1874) Spooner, 1947, G. zaddachi Sexton, 1912, G. ocea-

(Fig. ID), the sole representative of the family nicus Segerstràle, 1947 and G. wilkitzkii Birula, - 279 Bijdragen tot de Dierkunde, 60 (3/4) 1990

Fig. 2. Oostegites of freshwater Gammaridae with subequal rami on uropod 3: A, Gammarus pulex; B, Gammarus pseu- dolimnaeus; C, Gammarus pseudosyriacus Karaman & Pink- ster, 1977.

Fig. 3. Oostegites of marine Gammaridae with subequal rami on 1897have oostegites similar to the marine species il- uropod 3 and Anisogammaridae: A, Gammarus setosus Demen- lustrated in 3. The with markedly un- Fig. species tieva, 1931; B, Gammarus mucronatus Say, 1818; C, Gammarus equal rami on uropod 3 (Echinogammarus grouped tigrinus Sexton, 1939; D, Eogammarus oclairi. in Fig. 4) tend to have narrower oostegites than those with subequal rami. However, Echinogam- The “Gammarus” species of Tasmania were as-

has the Bous field marus stoerensis (Reid, 1938) (Fig. 5C) quite signed to Crangonyctoidea by (1977)

and different oostegites. In this species, oostegites two, and assigned to the genera Austrogammarus

Williams & Barnard How- three, and four are expanded, and only oostegite Antipodeus by (1988).

observations of live of five is narrow. Eogammarus oclairi Bousfield, 1979 ever, specimens Antipodeus

(family Anisogammaridae) (Fig. 3D) has oostegites showed they behaved much like northern hemi-

those of Gam- Gammarus rather than In that are indistinguishable from sphere Crangonyx. par-

walk their sides than marus. ticular, they on (rather up-

six and reflexed In many species of Gammarus, oostegite two and right) using peraeopods five, seven

curved and have their dorsal surface. This is form to alesser extent oostegite three are over a specialized

of locomotion of Gammarus and ob- a concave posterior margin (Figs. 2, 3, 4). In others typical not yet

the such as G. pulex and G. pseudolimnaeus Bousfield, served in the other amphipod groups, including

The of 1958 (Figs. 2A, B) these oostegites have a straight crangonyctoids. oostegites Antipodeus niger posterior margin similar to that found in Gam- Williams & Barnard, 1988conform to the Gamma-

rather than maracanthus (Fig. 1A) or Crangonyx (Fig. 5A). rus type (Fig. 5B) to Crangonyx (Fig. 280 D.H. Steele - Comparison of oostegite shapes in some gammaroidean species

Fig. 5. Oostegites of Gammaroidea: A, Crangonyx richmonden-

sis Ellis, 1940; B, Antipodeus niger; C, Echinogammarus

stoerensis.

maroidea the from broad oostegites vary to nar-

in to described for the row, a pattern parallel that

Haustorioidea (Steele, in press). This observation

supports the conclusion that the oostegites have Fig. 4. Oostegites of Gammaridae with markedly unequal rami evolved independently in the major amphipod on uropod 3: A, Echinogammarus marinus (Leach, 1815); B,

Echinogammarusfinmarchicus ( Dahl, 1938); C, Echinogamma- groups. with is found rus obtusatus (Dahl, 1938); D, Echinogammarus planicrurus A broad oostegite short setae which

(Reid, 1940); E, Echinogammarusfoxi (Schellenberg, 1928). in mysids, isopods and amphipods is the most

whereas with primitive type, a narrow oostegite 5A). It might be noted that crangonyctoids do oc- long setae known only in amphipods is the ad- in cur Tasmania, but none with developed ooste- vanced type. gites were available for study. Withinthe Gammaroidea, the Acanthogammari-

dae (Gammaracanthus, Garjajewia) have the most

primitive type of brood pouch. However, the struc- Discussion ture of thebrood pouch on Spinacanthus indicates

that either it has evolved towards the gammarid Although the oostegites of only a small fraction of

(see below) or, as seems more likely, the species the described gammaroidean species have been in- type has been misclassified. vestigated, it is possible to make some tentative The Macrohectopidae (Macrohectopus) and generalizations. Within the superfamily Gam- (superfamily Crangonyctoidea) - 281 Bijdragen tot de Dierkunde, 60 (3/4) 1990

have broad oostegites but of somewhat different forms (Figs. 2 & 3). Even a freshwater species such

shape (especially oostegite two) from the Acan- as Gammarusfasciatus, which is closely related to

lawren- thogammaridae. the marine G. tigrinus Sexton, 1939 and G.

thus of marine has There is an overall similarity in the brood pouch cianus and probably origin,

structure of members of the Gammaridae. The curved anterior oostegites. Cole (1985) showed G.

brood pouch is composed of a mixture of narrow fasciatus as having a straight posterior margin, but

(posterior) and broad (anterior) oostegites. The it is distinctly curved in all the specimens I have

similar brood pouch of the Anisogammaridae (Eo- examined from southern Canada. The Gammarus

of found in the sulfatochlo- gammarus oclairi) indicates that the two families pecos complex species

that ride of Texas and New Mexico have are closely allied. It should be noted, however, springs also a

marine Priscillina (Haustorioidea) also has a combination curved margin and most probably a origin.

of broad and narrow oostegites (Steele, in press). The structure of the brood pouch of the Tasma-

Within the Gammaridae there is continualvaria- nianAntipodeus, together with its specialized man-

tion in the oostegites, particularly in the narrowing ner of walking, indicates thatit belongs in the Gam-

in all the maridae rather than in the It of the anterior ones, so that some species Crangonyctoidea.

narrowed. It is difficult therefore allied oostegites are to seems more closely to Echinogammarus

than to accept as valid the Lagunogammarus estab- (Gammaridae) Eogammarus (Anisogam-

lished by Sket (1971) on the basis of the shape of its maridae).

it oostegites and of all the other genera and subgenera From this analysis of oostegite structures can

based on other characters that were summarized by be speculated thatthe gammaroid amphipods origi-

nated in the fresh waters of Eurasia where the Bousfield (1977). The synonymy summarized by

Karaman (1982) in which Rivulogammarus, Cari- primitive Acanthogammaridae are now most abun-

dant. Gammaracanthus has into the dilute nogammarus, and Lagun ogammarus are syn- spread

onymized with Gammarus, and Pectenogammarus, surface waters of the Arctic Ocean, but has readily

Eulimnogammarus (European records), Chaeto- reinvaded fresh water in Canada and Europe. The

broad of freshwater indicatesthat gammarus, Marinogammarus, Homoeogamma- oostegites species

and the Gammaridae also in fresh water. rus, Ostiogammarus, Parhomoeogammarus developed

moved into estuaries and are synonymized with Echinogammarus seems They have subsequently

marine most satisfactory at the present time. to the margins of the oceans. In these

habitats the Reinvasions of All Echinogammarus (markedly unequal rami on oostegites are narrower.

uropod three) tend to have narrowed and curved fresh water have then taken place by species such as

anterior oostegites. Echinogammarus stoerensis Gammarus fasciatus and the Gammarus pecos

result of this the has the only atypical brood pouch. This, plus its complex. As a complex history, other known differences from typical gammarids, gammaroid fauna at any location is likely to com-

suggests that it should be reexamined critically to prise species of several differentbackgrounds. reassess its generic position.

The anterior oostegites of Gammarus vary from

broad without with the to narrow, but a correlation References groupings of Bousfield (1977). Sket (1971) distin- guished freshwater from marine species of Gamma- Barnard, J.L. & C.M. Barnard, 1983. Freshwater Amphipoda rus the of the second oostegite. Marine by shape of the world, 1: 1-358; 2: 359-830 (Hayfield Associates, Mt. species have a gradually widening oostegite whereas Vernon, Virginia).

Barnard, J.L. & G.S. 1980. Classification of freshwater species have a shoulder near the base. Karaman, gam- marid Amphipoda. Crustaceana, Suppl. 6: 5-16. However, the distinction is better characterized by look the of Bousfield, E.L., 1977. A new at systematics gam- the straight posterior margin found in the fresh- maroidean amphipods of the world. Crustaceana, Suppl. 4: water both in North America and Eurasia species 282-316. and the curved margin of marine and estuarine Bousfield,E.L., 1979. A revised classification and phylogeny of 282 DM. Steele - Comparison of oostegite shapes in some gammaroidean species

amphipod . Trans, roy. Soc. Can., (4) 16: Ruffo, E. (ed.), 1982. The Amphipoda of the Mediterranean.

("1978"): 343-390. Mém. Inst. Océanogr., 13 (1): 1-364.

Bousfield, E.L., 1982. Amphipoda.. In: S.P. Par- Sket, B., 1971. Zur Systematik und Phylogenie der Gammarini

ker (ed.), Synopsis and classification of living organisms: (Amphipoda). Bulletin Scientifique (Yougoslavie), (A) 16: 6.

255-285 Book New in Is related (McGraw-Hill Co., York). Steele, D.H., press. oostegite structure to ecology

Bousfield, E.L., 1983. An updated classification and palaeohis- or phylogeny? Hydrobiologia.

Schram tory of the Amphipoda. In: F.R. (ed.), Stock, J.H., 1980. Regression model evolution as exemplifiedby

phylogeny. Crustacean Issues, 1: 257-277 (Balkema, Rot- the genus (Amphipoda). Bijdr. Dierk., 50

terdam). (1): 105-144.

1985. An of the 1988. Cole, G.A., analysis Gammarus-pecos complex Williams, W.D. & J.L. Barnard, The taxonomy of cran-

(Crustacea, Amphipoda) in Texas and New Mexico, U.S.A. gonyctoid Amphipoda (Crustacea) from Australian fresh

J. Ariz.-Nev. Acad. Sei.,. 20: 93-103. waters: Foundation studies. Ree. Austr. Mus., Suppl. 10:

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1-658 (British Museum (Natural History), London). Revised: 12 February 1990