Desdimelita spicatimanus Jarrett & Bousfield 1996, sp. nov.

Desdimelita (?) spicatimanus sp. nov.

Figures 1–7

Diagnosis. Pleon segment 2 with or without small single mid-dorsal tooth. Pleon segment 3 with small single middorsal tooth. Urosome segment 1 with small mid-dorsal tooth; urosome 2 with 2 pairs of short dorsal teeth, with single cuspidate seta among each lateral pair. Eye small, suboval; inferior antennal notch relatively large, open. Antenna 1 peduncle 1 with posterior marginal robust setae in distal half, article 2 slightly shorter than article 1; flagellum relatively long, with 31 articles; accessory flagellum 4-articulated. Antenna 2 flagellum short, with 14 setose articles.

Mandible, comb row with 10–12+ raker setae; palp article 3 setose. Maxilla 1, inner plate with 14 marginal setae. Maxilla 2, inner plate with submarginal facial row of setae. Maxilliped, inner plate with 4 apical teeth-like setae; outer plate medium, 3/5 of palp article 2 length.

Coxa 1 medium, distally broad, deeper than wide, with rounded lower margin. Coxa 4 medium, deeper than broad. Propodus of pereopod 1 relatively small, shorter than carpus, not broadened distally; palm regularly oblique; dactylus curved, slightly shorter than palm. Pereopod 2 carpus, posterior lobe broad; propodus large, longer than deep, palm convex and oblique, longer than posterior margin, with a row of strong long robust setae; dactylus thin, curved, with few long outer marginal setae. Pereopod 3 similar to pereopod 4; dactylus long, 0.7 of article 6 length. Pereopods 5–7, basis dissimilar, broadened from 5 to 7.

Uropod 1, peduncle short, rami with 4–5 robust setae marginally. Uropod 3, outer ramus relatively long, margins subparallel, each with 3–4 groups of robust setae; terminal article very small. Telson lobes with acute tips, with single distolateral and medial strong cuspidate setae each.

Coxal gills large, broadly saclike, gills 5 and 6 similar in size, distinctly smaller than 2–4.

Type material. Holotype female, 11.5 mm, 54398/Cr-2426, slope of western Kamchatka Peninsula, Sea of Okhotsk, Far East of Russia (56º0997’N 153º948’E, 702 m), silt, N. V. Shalaputin, 07 August 2020. Paratype: female, 6.8 mm, 54399/Cr-2427, with same data as holotype.

Type locality. The western slope of Kamchatka Peninsula, Okhotsk Sea, Far East of Russia (700 m).

Description. Female (11.5 mm). Vital body color unknown. Specimens of alcohol fixation are colorless, translucent; coxal plates, basal article of pereopods, and epimeral plates with moire patterns (Fig. 5). Pereon segments smooth dorsally (Fig. 2a). Pleon segment 1 without teeth; pleon segments 2 and 3 with small mid-dorsal tooth each. Urosome segment 1 with small tooth pulled back; urosome segment 2 with two dorsolateral pairs of small teeth and with single cuspidate seta among each lateral pair (Figs. 2a, b, 6k).

Head: (Fig. 2a, c) slightly longer than pereonite 1 with an indistinct rostrum; eye small, suboval, poorly distinguishable, with scattered ommatidia; anterior margin of head with broad subrounded anterior head lobe, lower antennal corner acute, pointed, lower margin without prominent accessory process.

Antenna 1: (Fig. 2d) 65% of body length, slender; flagellum 0.6 times length of peduncle, 31 articles, few very thin and short setae scattered along flagellum; peduncle article 0.9 times length and double as wide of article 2, with two strong simple robust setae along lower margin, and without acute protrusion at the distal margin, article 3 1/3 of article 2 length; accessory flagellum 4-articulate.

Antenna 2: (Fig. 2e) flagellum 0.4 times as long as peduncle, 14 articles, bundle of thin setae on each article; peduncle article 5 shorter than article 4, articles 1 + 2 + 3 together shorter than the length of article 5, article 1 with lower protruding lobe reaching the 0.5 of article 3, article 3 with short protruding lobe, article 5 with 2–3 tufts of thin setae spaced along upper and lower margins of the article.

Mouthparts.

Labrum incised (Fig. 2f).

Mandible: (Figs. 3a–d) incisor crenulate, 4–5 dentate and stretching in a rounded tip; left lacinia 5 dentate, right lacinia 4 dentate; raker setae strong and plumose, numerous (10–12+), shorter then incisor on left and as long as right incisor; molar cylindrical triturative, chewing plate flattened; palp articles 2 and 3 setose, first article without protruding lobe, the percentage of total length of the articles of the palp are 18% (article 1), 42–43% (article 2), 39–40% (article 3).

Labium: (Fig. 2g) inner lobes small but well defined, rounded; outer lobes rounded at distal margin.

Maxilla 1: (Fig. 3e) inner plate suboval, distally angular, lined with a row of 14 simple setae; outer plate elongate, apically with 2 rows of 9 strong comb setae; palp 2-articulate, article 2 1.6 times as long as article 1, article 2 apically with two rows of numerous (11+) simple setae each.

Maxilla 2: (Fig. 3f) inner plate slightly shorter than outer plate, facial setae of inner plate numerous, closely submarginal, tip covered with numerous simple setae; outer plate with numerous simple setae on the tip, subapically with a rare row of 7–8 setae.

Maxilliped: (Fig. 3g) inner plates large, fully cleft, distal margin with a row of 4 teeth and with a row of cuspidate setae, posterior surface submarginally with a row of plumose setae (4–5 setae); outer plates reaching the 3/5 of palp article 2 length, inner margin lined with few dense transverse rows of short stout teeth like setae, smoothly into the apical row of long plumose setae; palp 4-articulate, the percentage of total length of the articles of the palp are 12–15% (article 1), 41–46% (article 2), 21–22% (article 3), 21–22 (article 4), article 2 with setae along distal part of inner margin; tip of article 3 bilobed with a row of long simple setae and densely bushy at the inner lobe; article 4 with nail, inner margin with a line of simple setae.

Pereopod 1 (gnathopod 1): (Figs. 4a, b) coxa extended distally, with rounded anterior corner and with single notch at the posterior distal angle; basis straight with a row of simple setae along anterior and posterior margins each; merus subrectangular, with a cushion of short setae along distal part of posterior margin, distal margin with a row of long simple setae; carpus long, 1.3 times as long as propodus, 7 oblique rows of long plumose setae along outer posterior margin, 3 transverse rows of long setae at the inner surface near the hind margin, 4 clusters of setae along anterior margin, with a row of long setae along anterior and posterior parts of distal margin and with tomentose spot at the anterior-distal corner; propodus suboval, with 6 groups of long setae along posterior margin, with 2 tufts of long simple setae along anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palm oblique and minutely serrate with a row of numerous short thin simple setae, with the subpalmar inner row of medium size setae and with the posterior palmar row of long setae; dactylus slightly shorter then palm, curved, with a row of small setae along posterior margin.

Pereopod 2 (gnathopod 2): (Figs. 4c, d) coxa with subparallel anterior and posterior margins, rounded distally, with single notch at the posterior distal angle; basis straight, slightly longer than coxa, with a row of long simple setae along posterior margin and with rare short setae along anterior margin; merus subrectangular with distinct acute protrusion at the posterior distal corner, with 3 clusters of simple setae at the posterior margin; carpus long triangular, 0.7 as propodus length, with 6 tufts of long setae along posterior margin and with the distal group of long setae at the anterior margin only; propodus, palm rounded oblique, without distinct postero-distal tooth, anterior margin lined with 6 groups of long setae, posterior margin with 6 tufts of simple setae, palm with a row of 5–6 rare long robust setae; dactylus as long as palm, slightly curved to the inside of propodus, outer margin rarely setose, tip of dactylus with acute nail.

Pereopod 3: (Fig. 5a) coxa as long as coxa 2, slightly narrowed and rounded distally, with single notch at the posterior distal angle; basis long, narrow, 1.6 times as long as coxa, with concave anterior and convex posterior margins, with rare minute setae along anterior margin, and with long simple setae along posterior margin; merus long with 4 clusters of thin setae along anterior margin and with 2 thin cuspidate setae at the anterior distal corner, posterior margin with 3 bunches of long setae and with a tuft of long setae at the distal corner; carpus of 0.7 length of merus, with 2 clusters of long setae along posterior margin; propodus linear, as long as carpus, with 2 bunches of long setae along posterior margin; dactylus long (0.7 of propodus length), narrow, slightly curved inside.

Pereopod 4: (Fig. 5b) similar to that of the pereopod 3; coxa as long as coxa 3, wide, anterior corner rounded, pulled down, posterior angle broadly rounded, posterior margin excavated in proximal half.

Pereopods 5–7 elongated from pereopod 5 to pereopod 6, pereopods 6 and 7 equal in length; propodus and dactylus of each turned outward. Pereopod 5: (Fig. 5c, d) coxa with rounded front margin, with skew hind margin and anterior lobe pulled back and down; basis elongated, with straight posterior wing and with rounded posterior distal corner, anterior margin slightly convex, width is 0.5 of length, hind margin crenulated, anterior margin with small strong cuspidate setae; merus slightly broad medially, with 2–3 cuspidate setae along anterior margin, and with a cluster of 2 long cuspidate setae at posterior and anterior distal corner each; carpus more narrow and 0.8 as long as merus, with two groups of cuspidate setae at the anterior margin and with a single cluster of cuspidate setae at the anterior and posterior distal corners each; propodus linear, 1.1 times as carpus length, with 4–5 bunches of strong cuspidate setae along anterior margin and with 2 long simple setae along posterior margin; dactylus medium in length (0.5 of propodus length), with nail.

Pereopod 6: (Fig. 5e, f) coxa with skew anterior and hind margins and with small anterior lobe pulled back and down; basis slightly expanded, with posterior wing, rounded at the posterior distal corner, width is 0.5 as length, hind margin slightly concave, crenulated, anterior margin slightly convex, with small robust setae; merus slightly broad medially, with 3–4 clusters of cuspidate setae along anterior margin, with 3 clusters of cuspidate setae along posterior margin and with a cluster of 2–3 long cuspidate setae at posterior and anterior distal corner each; carpus as in pereopod 5; carpus with 2 tufts of strong cuspidate setae along anterior and posterior margins each; dactylus medium in length (0.5 of propodus length).

Pereopod 7: (Fig. 5g) coxa small, with indistinct anterior lobe and with rounded posterior lobe; basis expanded, with rounded posterior wing, width is 0.6 of length, posterior distal corner rounded, posterior margin crenulated, anterior margin with small robust setae; merus, carpus and propodus similar to that in pereopod 6; dactylus medium in length (0.4 of propodus length).

Coxal gills 2–6. Coxal gill 6 subequal to gill 5 in length.

Epimeral plates: (Fig. 6a, b, c) plate 1 is rounded anteriorly, posterior margin with 1–2 notches, hind corner with small tooth; plate 2 ventral margin convex, hind corner with tooth, posterior margin with 2–3 notches, ventral margin with a row of 4–5 strong robust setae; plate 3 hind corner produced, acute, posterior margin oblique, ventral margin convex, with a row of 7–8 strong robust setae.

Pleopods (Fig. 6 d, e, f): normal; peduncle with two specific toothed setae (retinacula) on the inner corner; inner ramus slightly longer than outer, basis of inner ramus with 5 specific stout two-pointed plumose setae along inner margin.

Uropod 1: (Fig. 6g) peduncle with strong and curved interramal spur; rami subequal in length, 0.9 times as peduncle length; peduncle and rami with tiny simple spiniform setae along outer and inner margins, both rami with few robust setae at tip each.

Uropod 2: (Fig. 6h) peduncle shorter than outer ramus (0.8 ramus length); inner ramus shorter than outer (0.9 ramus length), with numerous robust setae along outer and inner margins; uropod 2 shorter than uropod 1 (0.7 length).

Uropod 3: (Fig. 6i) peduncle 2 times shorter than peduncle of uropod 1, with 2 tufts of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (7 times the length of inner ramus, 2.3 times as long as peduncle), with 3 tufts of strong cuspidate setae along the anterior margin and with 4 tufts of strong cuspidate setae along the posterior margin of article 1, article 2 minute, as long as crowning setae, 8.8 times shorter then article 1; inner ramus short and ovoid, with two cuspidate setae subapically.

Telson: (Fig. 6j) fully cleft; lobes diverging distally; proximal notch positioned laterally; tips of lobes acute, with 1 distal lateral and 1 medial strong cuspidate seta each.

Variations. In paratype (female, 6.8 mm, with same locality data as holotype) dorsal tooth on pleon segments 2 is absent.

Etymology. Species name spicatimanus based on a Latin words “spicati” (spiked) and “manus” (hand) that is coused to the armament of the palmar margin of the propodus of pereopod 2 (gnathopod 2) with a row of long strong robust setae.

Ecology: Desdimelita (?) spicatimanus was found in the depth of 700 m on the silt bottom.

Distribution: The slope of Sea of Okhotsk near the western Kamchatka Peninsula.

Remarks. D. (?) spicatimanus sp. nov. differs from other Desdimelita species by the morphology of propodus of pereopod 2: broadened; palm with a row of 5–6 rare strong long robust setae). In other species of the genus Desdimelita propodus of pereopod longer and without of the row of strong long robust setae.

Differences of the new species from other species of the genus are observed in ecology. D. (?) spicatimanus was collected from a continental slope at a depth of about 700 m. Other species of the genus Desdimelita are found in the upper parts of the shelf from the lower littoral to a depth of 120 m (Alderman 1936; Barnard 1962, 1969; Barnard & Barnard 1983; Jarret & Bousfield 1996; Karaman 1981; Staude 1987).

Keys to the world species of the genus Desdimelita is provided below.