Odius cassigerus ochoticus, 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 : 40-43

Odius cassigerus ochoticus , subsp. n.

Figs. 5–8

Material. Holotype: Okhotsk Sea, 12 Aug. 2007, 54°82'N, 144°43'E, 200 m, female, length 16 mm. Collection of a Museum of Marine Biology Institute, Vladivostok: N 18861 . Paratype: 1 male, length 8 mm. Collection of a Museum of Marine Biology Institute, Vladivostok: N 18861 .

Diagnosis. Body with dorsal carination on pereonites 1–4 and with distinct teeth on pereonites 5–7 and on all plronites. Lower corner of cephalon subrectangular. Epimeral plate 3 with obtuse tooth medially. Posterior margin of bases of pereopods 5–7 with large triangular teeth in distal part. Maxilla 1 palp 1-articulate, short, about 1/5 of the outer plate length; with one setae on the distal margin. Maxilliped palp 4-articulate. Carpus lobe of preopod 2 (gnathopod 2) exceeding 1/2 of propodus length. Telson cleft 1/7.

Description. Body with dorsal carination on pereonits 1–4, with distinct teeth on pereonits 5–7 and on all pleonites (fig. 5). Sculpture of cover with large punctuation. Rostrum well-developed, reaching ½ of peduncle article 2 antenna 1 length. Lower corner of cephalon subrectangular. Pereonite 1 forming a sharp visor on an anterior margin that covers a posterior part of cephalon. Coxa 1–3 long, slightly curved anteriorly (fig. 7a,c.e). Coxa 1 rounded, pointed distally. Coxa 2 with smoothly rounded right angle anterodistally. Coxa 3 with acute angle anterodistally. Coxa 4 excavated with obtuse posterodistal angle (fig. 7f). Coxa 5–7 with processed posterior lobe. Eye medium size, long reniform, about 1/3 of the head height. Antenna 1 no longer than antenna 2; accessory flagellum lacking; flagellum with numerous short sensory setae along lower margin (fig. 6a). Antenna 2 with short flagellum which is slightly longer than last peduncle article (fig. 6b).

Mandible narrow conical, claw shaped; incisor multidentate, accessory plate present on left side; molar prominent, setose; short spine and setae row present between incisor and molar (fig. 6d,e). Palp of mandible 3-articulate; articles 2 slightly longer than 3; article 3 with a row of two-claw spines, distally with two oar shaped spines. Lower lip notched along midline; apices narrow pointed, without setation (fig. 6f). Maxilla 1 with short 1-articulate palp, about 1/5 of the outer plate length and carrying one setae distally (fig. 6g,h). Outer plate narrow, pointed, carrying short, heavy bidentate spines distally, densely setose proximally. Inner plate short, about ½ length of the outer plate, with 2 plumose setae distally. Maxilla 2 outer plate narrower than inner; setae on outer plate subequal to those on inner (fig. 6i). Maxilliped palp 4-articulate; article 2 slightly expanded medially; article 4 long (fig. 6j).

Pereopod 1 (gnathopod 1) chelate (fig. 7b). Anterior margin of basis with a row of setae; posterior margin prominent with out setae. Propodus slightly shorter than carpus; palm of propodus forming chela, with distinct finger, distally with short spine. Base of dactylus with two strong ridge setae.

Pereopod 2 (gnathopod 2) (fig. 7d). Basis elongate; posterior margin prominent, distally with few spines; anterior margin with a row of setae. Merus with processed lobe; border with stout setae. Carpus short; with distinct lobe that is a little more than 1/2 of propodus length; lobe and inner margin armed a row of strong plumose setae. Propodus expanded distally, strong; palm toothed, with two spines at palm angle. Dactylus slightly shorter than propodus palm, two-claw.

Pereopods 3–4 (fig. 7e,g). Basis elongate; anterior margin concave, with numerous setae; posterior margin curved. Merus slightly longer than carpus, with distinct acute lobe at the anterior distal angle. Carpus about 0.6 times as long as propodus; with 2–3 groups of small spines along posterior margin. Propodus linear; armed 6-7 small spines along posterior margin. Dactylus about ½ as long as propodus.

Pereopod 5–7 (fig. 7h-j): basis with distinct hind distal rounded lobe; posterior margin with large triangular teeth in distal part; wing of base separated with curved crest; anterior margin armed a row of setae. Merus produced distally, posterior long acute lobe, as long as carpus; posterior margin bearing 4–6 small spines. Carpus about 0.5–0.6 times as long as propodus. Propodus linear, armed 4 spines along anterior margin. Dactylus short, about 1/3 as long as propodus.

Epimeral plate 1: posterior margin slightly excavate (fig. 8a). Epimeral plate 2 with oblique crest; posteroventral corner pointed; posterior margin with obtuse tooth (fig. 8b). Epimeral plate 3: posteroventral corner angularly rounded; posterior margin with obtuse tooth medially (fig. 8c).

Pleopods normal (fig. 8d). 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 (fig. 8e-g).

Length of uropods 1–3 decreases from 1 to 2; 2 and 3 subequel. Peduncle margins of uropod 1 armed numerous spines proximally (fig. 8h). Inner ramus subequal to outer; both with numerous spines along posterior margin. Uropod 2 peduncle with numerous spines along borders (fig. 8i). Inner ramus about 0.7 as long as outer ramus, both with 7 spines along posterior margin. Uropod 3 peduncle subequel to inner ramus (fig. 8j). Inner ramus about ½ as long as outer ramus, lanceolate, with few small spines along hind margin. Outer ramus with numerous spines along posterior margin.

Telson longer than wide, cleft 1/7 (fig. 8k).

Remarks. The nominal subspecies Odius cassigerus cassigerus Gurjanova, 1972 was originally described from the south outlying part of Okhotsk Sea near south Kuril Islands. In Gurjanova´s (1972) there was an error: in the legends of plates 42 and 43 the type locality is given as Tatarsk Strait (Sea of Japan); in the descriptive text, however, the south part of Okhotsk Sea (44°49'N, 144°26'E) is given as the type locality. The author has found this nominal subspecies also in a southern part of Okhotsk Sea in Aniva bay. Odius cassigerus cassigerus Gurjanova, 1972 has the granulated sculpture of covers. Rostrum straight. Pereonite 1 anterodorsally with peak which covers a posterior part of head. Lower corner of cephalon forming acute angle. Coxa 2 rounded anterodistally. Posterior margin of epimeral plate 3 with distinct acute upwards curved tooth. Odius cassigerus ochoticus subsp. n. was found in the north-west part of Okhotsk Sea (54°82'N, 144°43'E). This subspecies differs from the nominative subspecies by a head shape: lower corner of cephalon subrectangular. Coxa 2 has smoothly rounded right angle anterodistally. Epimeral plate 3 has obtuse tooth medially. Sculpture of cover with large punctuation.

Figures

FIGURE 5. Odius cassigerous ochoticus s sp. n., holotype female, 16 mm, Okhotsk Sea. Lateral.

FIGURE 6. Odius cassigerous ochoticus ssp. n., holotype female, 16 mm, Okhotsk Sea. a, antenna 1; b, antenna 2; c, labrum; d, right mandible; e, left mandible (palp articles not shown); f, lower lip; g, left maxilla 1; h, right maxilla 1; i, maxilla 2; j, maxilliped.

FIGURE 7. Odius cassigerous ochoticus ssp. n., holotype female, 16 mm, Okhotsk Sea. a, coxa 1; b, pereopod 1; c, coxa 2; d, pereopod 2; e, pereopod 3; f, coxa 4; g, pereopod 4; h, pereopod 5; i, pereopod 6; j, pereopod 7.

FIGURE 8. Odius cassigerous ochoticus ssp. n., holotype female, 16 mm, Okhotsk Sea. a, epimeral plate 1; b, epimeral plate 2; c, epimeral plate 3; d, pleopod 2; e, inner setae of the inner ramus of pleopod 1; f, inner setae of the inner ramus of pleopod 2; g, inner setae of the inner ramus of pleopod 3; h, uropod 1; i, uropod 2; j, uropod 3; k, telson.