Pseudokoroga spongiophila, Lörz & De Broyer, 2004

Lörz, Anne-Nina & De Broyer, Claude, 2004, Description and ecology of a spongicolous lysianassoid amphipod (Crustacea) from Antarctica, Journal of Natural History 38 (7), pp. 889-899 : 890-897

Pseudokoroga spongiophila sp. nov.

(figures 1–5)

H: ovigerous female 5.4 mm, Zoological Museum Hamburg (ZMH K 39943 ), Polarstern ANT XVII-3, St. 124-1, symbiotic in Jophon spatulatus (Kirkpatrick, 1907) .

P: males (3.5–5.15 mm) and females (3.0– 5.16 mm), ZMH K39943 - K 39946 ; IRScNB Brussels and ZMB Berlin.

Distribution Eastern Weddell Sea and Bransfield Strait, 266– 666 m. Diagnosis

Lateral cephalic lobe regularly rounded. Eyes suboval. Peduncle of antenna 1 elongated, first article of flagellum short. Dorsal length ratio head: pereonite 1 about

1:1. Epimeral plates posterodistal angle rounded. Gnathopod 1 with tubercle in the

middle of the palm. Urosomite 1 with a prominent rounded dorsal hump.

Description

Body. Rather slender, dorsally smooth, except urosomite 1 bearing a rounded dorsal boss. Coxa 1–4 short, slightly longer than the corresponding pereonites, slightly longer than broad, slightly overlapping, broadly rounded distally. Antero- and posteroventral angles of epimeral plates 1–3 rounded. Colour white in live and preserved specimen.

Head (figure 1). Half as long as deep, dorsally as long as first pereonite, rostrum small; lateral cephalic lobe short, rounded; eyes large, broadly oval.

Antenna 1 (figure 2). Peduncle longer than head, article 1 elongated, article 2 and 3 ordinary. Callynophore poorly developed. Primary flagellum long, 1.5 times as long as peduncle, of 13 articles, first article short, calceoli absent in female, present in male. Simple setae and aesthetascs on peduncle and flagellum. Accessory flagellum with seven articles, more than half as long as primary flagellum.

Antenna 2 (figures 1, 4). Only slightly longer than antenna 1. Peduncular article 4 slightly longer than article 5, flagellum subequal to peduncle.

Mouthparts. Mouthparts forming subquadrate bundle. Epistome and upper lip separate, blunt, epistome slightly prominent.

Mandible (figure 2). Incisor smooth; lacinia mobilis on left mandible, three raker spines present, molar triturative, of medium size, palp three-articulate attached strongly proximally to molar; article 1 shorter than wide, article 2 1.4 times as long as article 3, with a row of long D2 setae on distal third of posterior margin; lacina mobilis digitiform. Article 3 bearing D3 and E3 setae.

Maxilla 1 (figure 2). Inner plate weakly setose, narrow, with two long, plumose setae at distal margin; outer plate with a 7/4 crown setal-tooth arrangement; ST A not reaching two-thirds height of ST 1; palp two-articulate, distal article large, with three distal robust setae.

Maxilla 2 (figure 2). Inner plate narrow with one setal row distally, consisting of six long setae; outer plate 1.3 times as long as inner plate. Both plates tapering apically.

Maxilliped (figure 2). Inner and outer plate well developed, inner plate with three robust setae on distal margin; outer plate with two apical robust setae and one smaller seta just below, palp strongly exceeding outer plate, dactylus well developed.

Gnathopod 1 (figure 1). Robust, smaller than gnathopod 2; coxa 1 slightly expanding anteroventrally, small setae on ventral margin; basis bearing setae anteriorly and posteriorly; carpus lobate; propodus 3.5 times as long as carpus, slightly widened proximally, strongly subchelate, palm oblique, excavate, with two setulated robust setae on produced posterior corner; dactylus large. Inner side of propodus with two pectinate setae as seen in figure 5A, B. Dactylar article ventrally grooved, claw ornamented with longitudinal furrows as seen in figure 5C.

Gnathopod 2 (figure 1). Coxa subrectangular with anterior margin strongly convex; ischium elongated; carpus 1.9 times as long as wide, anterior and posterior margin convex, carpus nearly twice as long as propodus; propodus chelate and strongly setose; dactylus fitting palm, with a minutely dentate cutting margin as seen in figure 5D.

Pereopod 3 (figure 3). Coxa 3 similar to coxa 2; propodus 1.5 times as long as carpus, posterior margin with a row of single and paired robust setae.

Pereopod 4 (figure 3). Similar to pereopod 3; coxa 4 broader than coxa 3, posterior margin concave.

Pereopod 5 (figure 3). Coxa 5 equilobate, each lobe semi-circular; basis broadly expanded, with a row of slender robust setae along anterior margin, weakly crenulate along posterior margin. Basis, ischium and merus with a long robust seta on anterodistal angle; merus slightly expanded, three robust setae on posterior margin; propodus 1.4 times as long as carpus; dactylus half as long as propodus.

Pereopod 6 (figure 3). Coxa 6 small, slightly wider than long; basis almost 1.5 times as long as wide, almost oval, with a row of single robust setae on anterior margin. Basis, ischium and merus with long robust setae on anterodistal angle; merus similar to merus of pereopod 5, but with only two strong robust setae on posterior margin; propodus about twice as long as dactylus.

Pereopod 7 (figure 3). Coxa 7 suboval; basis 1.2 times longer than wide, row of single robust setae on anterior margin, posterior margin strongly convex, posterior border slightly crenulated. Basis, ischium and merus with long robust setae on anterodistal angle; merus twice as long as wide, posterodistal angle of merus produced; carpus and propodus similar to those of pereopod 6.

Epimeral plates 1–3 (figure 4). With rounded posterodistal angle.

Pleopods (figure 4). Well-developed, rami subequal.

Gills (figures 1, 3). Simple, on pereopods 2–7.

Uropod 1 (figure 4). Outer ramus about as long as inner ramus, reaching threequarters of the length of peduncle; both rami with serrated margins and one large apical robust seta.

Uropod 2 (figure 4). Inner ramus without notch; rami equal in length, slightly longer than peduncle; both rami with large apical robust setae and serrated margins.

Uropod 3 (figure 4). Peduncle short, rami lanceolate, without plumose setae, inner ramus slightly shortened, outer ramus two-articulate, twice as long as peduncle, article 2 short, reaching a third of the length of article 1. As in uropods 1 and 2 rami margins densely serrated.

Telson (figure 4). As long as broad, 40% cleft, with two apical robust setae.

Sexual dimorphism weakly developed. Compared to females the eyes in males are larger and closer to the head anterior margin. Only males have calceoli on their first antennae, located on the first 5–11 articles (figure 4). The first articles of the antennae 1 flagellum are thicker than those of females, the length/width ratio is about one-half compared to nearly three-quarters. Uropod 3 of males extends a little further and the second article of uropod 3 is relatively longer in males.

Etymology Named after the habitat of the new species.