Oedicerina vaderi, Coleman, Charles Oliver & Thurston, Michael H., 2014

Coleman, Charles Oliver & Thurston, Michael H., 2014, A redescription of the type species of Oedicerina Stephensen, 1931 (Crustacea, Amphipoda, Oedicerotidae) and the description of two new species, Zoosystematics and Evolution 90 (2), pp. 225-247 : 227-228

Oedicerina vaderi sp. n. Figs 6, 7, 8, 9, 10

Type material.

Male holotype, 7.3 mm; NHMUK 2014. 398, Discovery Stn 7709#73.

Type locality.

North Atlantic, East Iceland Basin: 60°07.1'N 19°30.3'W - 60°06.1'N 19°24.8'W, 5 May 1971, BN 2.4, 2636-2646 m.

Paratypes.

1 female, 6.3 mm; 2 specimens of unknown sex, 4.2 mm and 5 mm; NHMUK 2014. 399-401, Discovery Stn 7709#73, from the type locality.

Etymology.

The specific name vaderi recognises the important contributions to amphipod studies made by Professor Wim Vader.

Description.

Holotype male, 7.3 mm. Head (Fig. 6c): longer than high, longer than pereonites 1-2 combined; no eyes or ocular pigment visible; rostrum (Fig. 6c) strongly deflexed, the ventral margin concave. Antenna 1 (Fig. 6f): length ratios of peduncle articles 1-3 1:0.5:0.3; flagellum [broken], proximal flagellum articles wider than long; accessory flagellum 1-articulate, slender, about half the length of peduncle article 3. Antenna 2 (Fig. 6g): peduncle weakly setose; length of article 4 1.5 × article 5; flagellum shorter than peduncle article 5, 9-articulate. Upper lip (labrum) (Fig. 6d): wider than long, apically rounded. Mandible (Fig. 7a, e): incisors and laciniae mobiles 5-dentate; palp 3-articulate, article 2 swollen proximally, article 3 tapered, length ratios of articles 1-3 1:4.3:6.1. Lower lip: inner lobes prominent and broad, hypopharyngeal gap wide, outer lobe mandibular processes short and rounded. Maxilla 1 (Fig. 7d): inner fig tapered, with two distal setae; outer fig with nine acute setal-teeth; palp 2-articulate, article 2 5 × length of article 1. Maxilla 2 (Fig. 7b): inner fig 1.3 × wider than outer fig; both figs with relatively sparse apical setation. Maxilliped (Fig. 7c): inner fig short, extending just beyond base of palp article 1; outer fig extending 30% along palp article 2; concave medially; palp 4-articulate; article 1 tapered; article 2 broad, strongly expanded medially, lobe broadly rounded; article 3 narrow proximally and expanded mediodistally; article 4 curved, acute; length ratios of articles 1-4 1:2.2:0.8:1.3.

Pereon.Pereonite 1 (Fig. 6a): longer than 2; pereonite 2 shortest. Gnathopod 1 (Fig. 8a): coxa subtriangular, posterior margin straight, anterodistal corner broadly rounded, posterodistal corner rectangular, distal margin straight, weakly setose; basis curved, posterior margin with a row of plumose setae; merus, posterodistal lobe rounded, setose; carpus strongly expanded, subrectangular posterior lobe with posterior and distal margins setose; propodus strongly expanded, as long and as wide as carpus, anterior margin convex, palm convex, transverse, crenellate, setose; dactylus falcate, as long as palm. Gnathopod 2 (Fig. 8b): coxa as long as coxa 1, tapering distally, apex truncate with few setae at the distal margin; basis subrectangular, with a posterodistal group of plumose setae and an anterodistal group of simple setae; merus, posterodistal lobe narrow, setose; carpus strongly expanded, wider than propodus, posterodistal lobe subacute, posterior and distal margins setose; propodus as long as carpus, expanded distally, palm convex, crenellate; dactylus slender, curved, as long as palm. Pereopod 3 (Fig. 9a): coxa subequal to coxa 2, apex rounded, weakly setose; basis shorter than coxa, long plumose setae distally along posterior and anterior margins; merus expanded anterodistally, setose; carpus 1.3 × length and about as wide as merus, posterior margin densely setose; propodus oval, anterodistal and posterior margins setose; dactylus lanceolate, subequal to propodus. Pereopod 4 (Fig. 9b): coxa wider than long, anterior margin broadly rounded, distal margin straight, posterodistal lobe very strong, subrectangular; basis shorter than coxa, anterior and posterior margins setose distally; merus expanded anterodistally, setose; carpus 0.8 × merus, but subequal in width, posterior margin strongly setose, long setae anterodistally; propodus, anterior margin setose; dactylus, straight, lanceolate, 1.5 × propodus. Pereopod 5 (Fig. 9c): coxa about as deep as coxa 4, bilobed, posterior lobe expanded distally, distal margin straight, anterior lobe 0.7 × length of posterior lobe, rounded distally; basis shorter than coxa; merus as long as basis; carpus 0.3 × length of merus; propodus slender, subrectangular, 0.9 × merus, about as long as straight lanceolate dactylus; articles 2-6 variously setose. Pereopod 6 (Fig. 10a): coxa 0.8 × length of coxa 5, bilobed, posterior lobe long, distal margin rounded, anterior lobe subrectangular, 0.4 × length of posterior lobe; basis subrectangular; merus, posterior margin weakly convex; carpus subrectangular, 0.4 × length of merus; propodus and straight dactylus as long as merus; articles 2-6 variously setose. Pereopod 7 (Fig. 10b): long; coxa wider than long, oval, posterodistal corner rounded; basis posterior margin weakly convex, anterior margin strongly convex; merus elongate; carpus, 0.9 × merus; merus and carpus with groups of short setae on anterior and posterior margins; [propodus and dactylus unknown].

Pleon.Pleonites 1-3 (Fig. 6a): smooth, lacking carinae or teeth. Epimera (Fig. 6e): 1 and 3 evenly rounded; epimeron 2, posterodistal angle produced, rounded, posterior margin sinuous. Pleopod 1: peduncle stout, 0.8 × length of rami; rami subequal in length.

Urosome.Urosomite 1 (Fig. 10e): longest, with low boss close to the posterior margin; urosomite 3 longer than 2, with short, acute mid-dorsal projection. Uropod 1: peduncle elongate, lateral margin with robust setae, mesial margin setose; inner ramus, [broken], both margins setose; outer ramus 0.7 × length of peduncle, setae on lateral margin only. Uropod 2 (Fig. 10d): peduncle not tapering, both margins with short setae; [rami damaged], inner ramus, both margins setose; outer ramus, lateral margin setose. Uropod 3 (Fig. 10c): peduncle short, about as long as telson, with ventral subacute projection; outer ramus just longer than inner ramus. Telson (Fig. 10f) tapered, notched 40%.

Variability.

The paratypes bear a small posteriorly directed tooth on pleonite 3. It may be that this process has been present and is worn down in the holotype. Antenna 1 of the female (Fig. 6b) has a longer and more slender peduncle and fewer and more elongate flagellum articles compared to the male.

Distribution.

North Atlantic, south of Iceland, 2636-2646 m.