Crustacea: Amphipoda
Total Page：16
File Type：pdf, Size：1020Kb
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, Amphipoda Abstract Whilethese revisions have found support, not all of the changes have been accepted (e.g. Barnard& Within the superfamily Gammaroidea 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 Acanthogammaridae, Macrohectopi- result, amphipod taxonomy, especially as it relates dae and a few of the Gammaridae. 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 Gammarus 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, Gammaracanthus 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