Antarctodius noncarinatus, Labay, Vjacheslav S., 2010

Labay, Vjacheslav S., 2010, A new species and subspecies of Ochlesidae Stebbing, 1910 (Amphipoda: Gammaridea) from the Okhotsk Sea, Zootaxa 2354, pp. 35-44 : 36-39

Antarctodius noncarinatus , sp. n.

Figs. 1–4

Material. Holotype: Okhotsk Sea, 12 Aug. 2007, 54°82'N, 144°43'E, 200 m, male, length 18 mm. Collection of a Museum of Marine Biology Institute, Vladivostok: N 18861 .

Diagnosis. Body smooth dorsally, without up-right teeth. Bases of pereopods 5–7 with rounded right angle posterodistally. Eye large, long reniform. Maxilla 1 palp 2-articulate, long, reaching end of outer plate, with few setae on the distal margin. Maxilliped palp 4-articulate, article 4 strongly reduced. Carpus lobe of preopod 2 (gnathopod 2) exceeding 1/3–1/4 length of propodus. Telson visibly entire.

Description. Body smooth dorsally, without teeth and humps. Sculpture of cover is large punctuation (fig. 1). Rostrum well-developed, reaching a distal margin of peduncle article 1 of antenna 1. Lower corner of cephalon subrectangular. Coxa 1–3 longer than wide, slightly curved anteriorly (fig. 3a-c). Coxa 1 distally subacute; coxa 2–3 with smoothly rounded right angle anterodistally. Coxa 4 excavated posteroproximally with rounded posterodistal margin (fig. 3d). Coxa 5–7 each with produced posterior lobe. Eye large, long reniform, about 4/7 of the head height. Antenna 1 longer than antenna 2; lacking accessory flagellum; flagellum with numerous sensible setae along lower margin (fig. 2a). Antenna 2 with short flagellum slightly longer than last palp article (fig. 2b).

Mandible conical; incisor multidentate, accessory plate present on left side; molar prominent, setose; strong spine row presents between incisor and molar (fig. 2c,d). Palp of mandible 3-articulate, articles 2 and 3 subequal in length, article 3 with a row of comb spines and a row of short thin setae, distally with two long comb spines. Lower lip notched along midline, apices narrow pointed, setose (fig. 2e). Maxilla 1: 2-articulate palp exceeding length of outer plate and carrying few setae; outer plate carrying short heavy bidentate spines distally, densely setose proximally; inner plate with 3 plumose setae distally (fig. 2f, 3). Maxilla 2: outer plate narrower than inner; setae on outer plate subequal to those on inner (fig. 2g). Maxilliped: palp 4-articulate, article 2 slightly expanded medially, article 4 small concealed among long distally setae; inner plate of maxilliped with a few incised spines distally (fig. 2h).

Pereopod 1 (gnathopod 1) subchelate, with very short transverse palm margin (fig. 3a). Posterior margin of basis prominent with few long setae. Carpus and propodus subequal; palm of propodus with strong spine on the posterior distal corner that forms something like a chela. Base of dactylus with few strong comb setae.

Pereopod 2 (gnathopod 2) (fig. 3b). Basis elongate, posterior margin distally with few spines. Merus with rectangular lobe, border with stout plumose setae. Carpus long, with distinct lobe that is 1/3–1/4 as long as propodus; lobe and posterior margin armed a row of double-pointed strong plumose setae. Propodus rectangular, strong; palm transverse with two bidental stout spines at palm angle; posterior margin with 6 bidental spines. Dactylus strong, bidental, as long as palm of propodus.

Pereopods 3–4 (fig. 3c,d). Basis elongate; anterior margin concave, with few setae, posterior margin curved. Merus slightly longer than carpus, with distinct acute lobe at the anterior distal angle. Carpus about 0.6–0.7 times as long as propodus, with 2–3 groups of small spines along posterior margin. Propodus linear, long, armed 6-7 small spines along posterior margin. Dactylus about 1/2 as long as propodus.

Pereopods 5–7 (fig. 3e-g): basis subrectangle, with distinct hind lobe; posterior distal angel slightly rounded (pereopods 5–6) or right angle (pereopod 7); wing (posterior lobe) of base separated with curved crest; anterior margin proximally with tuft of setae. Merus drawn out posterodistally into long acute lobe, about 0.7 as long as carpus, posterior margin bearing 3–4 small spines. Carpus sublinear, about 0.6–0.7 as long as propodus, with 4–5 spines along anterior margin. Propodus linear, armed 6–7 spines along anterior margin. Dactylus long, about 1/2 as long as propodus.

Epimeral plate 1: hind corner slightly obtuse; posterior margin slightly excavate (fig. 4a). Epimeral plate 2 with oblique crest; hind corner subrectangular; posterior margin slightly excavate (fig. 4b). Epimeral plate 3 with oblique crest; hind corner pointed; posterior margin with large distinct tooth medially (fig. 4c).

Pleopods normal (fig. 4d). Peduncle with two specific toothed coupling spines on the inner corner. Basis of inner ramus with a row of specific stout two-pointed plumose setae along inner margin.

Length of uropods 1–3 decreases from 1 to 3. Peduncle borders of uropod 1 armed numerous spines (fig. 4e). Inner ramus slightly shorter than outer, both with few spines along posterior margin. Uropod 2: peduncle with numerous spines along borders; inner ramus about 2/3 as long as outer ramus, both with 5–6 spines along posterior margin (fig. 4f). Uropod 3: peduncle subequel to outer ramus; inner ramus about 2/3 as long as outer ramus, both rami lanceolate, with few small spines along posterior margin (fig. 4g).

Telson entire, long triangular (fig. 4h).

Remarks. Antarctodius noncarinatus differs from Antarctodius antarcticus ( Watling et Holman, 1981) by the following characters. Absence of body carination. Eyes large, black, reniform ( Antacrtodius antarcticus :eyes small, not reniform). Presence of a distinct posterior lobe on bases of pereopods 5–6 with a rounded obtuse angle; on a basis of pereopod 7 with right angle ( Antarctodius antarcticus : bases of pereopods 5–7 with out angle on posterior margin, rounded). Telson entire.

Antarctodius noncarinatus differs from Antacrtodius rauscherti Coleman et Kauffeldt, 2001 by the following characters. Cuticle strongly sclerotized, not transparent. Eyes present, black, reniform ( Antacrtodius rauscherti : eyes not present or weakly distinguishable). Rostrum surpassing ventral margin of head, slightly curved and stout. Apex of coax 2 and 3 truncate with anterior angle rounded. Presence of a distinct posterior lobe on bases of pereopods 5–6 with a rounded obtuse angle; on a basis of pereopod 7 with right angle ( Antacrtodius rauscherti : bases of pereopods 5–7 with out angle on posterior margin, rounded). Telson entire ( Antacrtodius rauscherti : telson strongly cleft).

Figures

FIGURE 1. Antarctodius noncarinatus, sp. n., holotype male, 18 mm, Okhotsk Sea. Lateral.

FIGURE 2. Antarctodius noncarinatus, sp. n., holotype male, 18 mm, Okhotsk Sea. a, antenna 1; b, antenna 2; c, right mandible; d, left mandible; e, lower lip; f, maxilla 1; g, maxilla 2; h, maxilliped.

FIGURE 3. Antarctodius noncarinatus, sp. n., holotype male, 18 mm, Okhotsk Sea. a, pereopod 1; b, pereopod 2; c, pereopod 3; d, pereopod 4; e, pereopod 5; f, pereopod 6; g, pereopod 7.

FIGURE 4. Antarctodius noncarinatus, sp. n., holotype male, 18 mm, Okhotsk Sea. a, epimeral plate 1; b, epimeral plate 2; c, epimeral plate 3; d, pleopod 3; e, uropod 1; f, uropod 2; g, uropod 3; h, telson.