Andaniotes abyssorum Stebbing, 1888

Berge, JØrgen, 2001, Revision of the Amphipod (Crustacea: Stegocephalidae) genera Andaniotes Stebbing, 1897 and Metandania Stephensen, 1925, Journal of Natural History 35 (6), pp. 787-832 : 789-794

Andaniotes abyssorum Stebbing, 1888

(®gures 1±4)

Andaniotes abyssorum Stebbing, 1888: 739 .

Andaniotes abyssorum: Stebbing, 1906: 96 (part).

? Stegocephalus abyssorum: Della Valle, 1893: 629 , pl.59, ®gure 38.

Not Andaniotes corpulentus: Stebbing, 1897: 31

Material examined

HOLOTYPE: Nat. Hist. Mus. London; 1889.5.15.4 2 (slides), female, 40 ss 28 ¾ S, 177 ss 43 ¾ E, 2012 m; Australian Museum P 52719: ®ve specimens, 43 ss 06.70 ¾ S, 145 ss 13.60 ¾ E, 200 m; AM P 52721: one specimen, 43 ss 06.70 ¾ S, 145 ss 13.60 ¾ E, 200 m; J24060 (Victoria): 26 specimens, 38 ss 17 ¾ S, 149 ss 11 ¾ E, 400 m; (?) Berlin 22753: 14 specimens, 52 ss 29 ¾ S, 60 ss 36 ¾ W, 197 m.

Distribution 38±43 ss S, 145± 177 ss E, 200±2012 m (but see also Remarks).

Description

Length of males and females: 5±8 mm.

Rostrum very small.

Antennae short. Antenna 1 longer than antenna 2; ¯agellum four-articulate; accessory ¯agellum article 2 present. Antenna 2 peduncle (articles 3±5) longer than ¯agellum; article 3 short, about as long as broad; article 4 as long as article 5.

Epistome produced laterally; broad and round; epistomal plate large and conical (not a keel).

Mouthparts not elongate or pointed. Mandible incisor transverse, smooth; left lacinia mobilis present, reduced, laterally straight, conical.

Maxilla 1 palp uni-articulate, rectangular; setae long simple, slender; apex reaching above the apex of outer plate; outer plate distally rounded; ST in two parallel rows, ®rst marginal and second submarginal; ST ®rst row with six setae (ST1±5, ST7); ST 1 ordinary (similar to ST 2±4); gap between ST 5 and ST 7; ST A± C, part of second row; inner plate without a well developed shoulder; setae pappose.

Maxilla 2 ordinary; outer plate setae without distal hooks or cleft; inner plate setae row A covering the entire margin; appressed to row B; row A setae pappose; ®rst three or four setae diOEerentiated from the other setae (weakly pappopectinate); row B setae proximally pappose; distally with cusps; row C present; row D absent.

Maxilliped palp four-articulate; article 2 distally unproduced; dactylus distally simple (pointed); inner plate not exceeding base of palp article 1; with three nodular setae; medial setae-row present, not reduced, vertical, setae cuspidate; distal setaerow present; inner setae-row present, row reduced to one seta, not conspicuously large; outer plate outer setae-row present, marginal, setae attached normally, setae long robust, straight; inner setae-row present but strongly reduced, setae short simple, slender, parallel but not appressed to outer row; distal setae-group absent.

Labrum very short; lobes symmetrical and reduced.

Labium distally broad, oval.

Coxal plates and basis on the pereopods smooth. Coxae 1±3 contiguous.

Pereopod 1 coxal plate not as deep as basis; propodus subovate.

Pereopod 2 longer and thinner than pereopod 1; ischium elongate, ratio length:- breadth exceeding 1.5; ischium distal posterior margin with plumose setae; propodus subovate; palm developed.

Pereopod 4 coxa posteroventra l lobe large, reaching about the base of the pereon segment 7; basis anterior and posterior margins without long setae; no plumose setae on distal anterior and posterior margins; ischium with plumose setae on posterior distal margin.

Pereopod 6 basis posteriorly expanded; expansion conspicuous; rounded posteriorly; without a row of long plumose setae.

Pereopod 7 basis anterior margin straight; distally rounded; medial row of setae absent.

Oostegites on pereopods 2±5, gills on pereopods 2±7.

Pleonites 1±3 dorsally smooth.

Urosomites 2 and 3 free. Uropod 1 peduncle longer than rami, outer ramus longer than inner. Uropod 2 peduncle longer than rami, outer ramus longer than inner. Uropod 3 peduncle longer than half the length of rami, outer ramus twoarticulate, outer ramus longer than inner.

Telson as long as broad; shorter than uropod 3 peduncle; no submarginal setae on apex of each lobe; cleft, apically rounded.

Males. Epistome very large: conspicuously broad and rounded. Pereopods 1 and 2 propodus larger in males than in females. Urosome conspiciously larger than in females; uropod 1 outer ramus enlarged, curved upwards; uropod 2 outer ramus enlarged, curved upwards; uropod 3 rami reduced.

Remarks

The present species is herein re-established as a valid species, after it was synonymized with A. corpulentus by Stebbing (1897). This is ®rst of all the result of the very diOEerent morphology of the males of the two species (see descriptions), as the females are, except for the morphology of the epistome, very similar.

The material from Berlin (14 specimens, see details above) appears to be rather distinct from the`true’ A. abyssorum , in that the epistome is much more rectangular (versus broad and round) and the palm on pereopod 2 is much less developed. Furthermore, its origin also diOEers signi®cantly as it is from the western Antarctic region. However, since the material in question does not include any males, and as the males of this species are highly distinct from all other known stegocephalid species, I will not at the present describe these specimens as a species distinct from A. abyssoru m.

The holotype of the present species is from very deep waters (2012 m, hence the species name), while all the remaining material is from 200±400 m. Nevertheless, although the holotype is in a very poor condition, the material at hand correlates very well with Stebbing’s (1888) original description.