Dolichiscus clarencensis Poore & Black, 2024, sp. nov.

Dolichiscus clarencensis sp. nov.

(Figs 10, 11)

Material examined: Holotype. Weddell Sea, 40 km N of Clarence I., 60°38.79’S–60°38.39’S, 53°57.42’W– 53°57.55’W, 315 m, 2 Feb 2002, Agassiz trawl, RV Polarstern (ANDEEP I stn 46-8), ZMH K-65090 (male, 10.2 mm).

Description of holotype: Body more or less cylindrical, largely smooth. Head twice as long as fused pereonite 1; front slightly concave, ventrolateral margin straight; eye circular, lateral. Pereonite 1 wider than long, ventrolateral margin with 3 small coxal teeth. Pereonites 2–4 increasing in length posteriorly, each with 2 subventromarginal tubercles. Pereonites 5–7 each short posterolateral tooth.

Pleonite 1 dorsally about one-sixth of length of remaining pleotelson, with 1 posterolateral tooth. Pleotelson with ventrolateral suture, with 1 strong submarginal lateral tooth plus 14 small submarginal teeth, last 2 pairs forming almost transverse with median apex, dorsolateral ridge ending in median spine with stronger spine below.

Antennula peduncle article 1 with dorsal spine; articles 2 and 3 together about as long as article 1; flagellum 1.5 times as long as peduncle, with minute second article. Antenna 1.5 times body length; peduncle article 2 as long as head, with 2 dorsal spines, distally overlapping article 3; article 3 twice as long as article 2; article 4 twice as long as article 3; article 5 1.2 times as long as article 4; flagellum 1.2 times as long as article 5, of 1 long plus 10 short articles.

Maxilliped with short broad coxa; basis and endite about twice as long as wide, apex with 4 plumose, 3 simple setae; ischium attaching near midpoint; merus, carpus, propodus of similar lengths, carpus 1.3 times as long as wide; dactylus one-quarter length of propodus, rectangular.

Pereopod 1 basis without marginal spines; merus with swollen extensor margin; propodus 2.2 times as long as wide, with mesial facial setae, flexor margin with row of setae; dactylus body 4 times as long as wide, unguis half as long as propodus body. Pereopod 2 coxa with small ventrolateral tooth; basis–carpus with 1, 1, 2, 5 spines along extensor margin; carpus 6 times as long as wide; propodus curved, as long as carpus; dactylus body quarter length of propodus, unguis 1.5 times as long as dactylus body. Pereopod 3 similar to pereopod 2, slightly longer. Pereopod 4 similar to pereopods 2, 3; basis relatively longer. Pereopod 5 coxa with posterolateral spine; basis 5.5 times as long as wide, flexor margin with 3 teeth; ischium as long as basis, extensor margin with 1 spine; merus half as long as ischium, without spines; carpus extensor margin with distal spine, flexor margin with 6 robust setae; propodus flexor margin with 4 robust setae; dactylus curved, shorter than propodus. Pereopod 6 coxa with 2 ventrolateral spines, 1 posterolateral spine; basis 4.6 times as long as wide, flexor margin with 3 teeth; ischium shorter than basis, flexor margin with 2 spines; merus half as long as ischium, without spines; carpus without spines, flexor margin with 5 robust setae; propodus flexor margin with 5 robust setae; dactylus curved, shorter than propodus. Pereopod 7 coxa with 1 ventrolateral spine, 1 posterolateral spine; basis 4.3 times as long as wide, flexor margin with 3 teeth; ischium shorter than basis, flexor margin with 4 spines; merus half as long as ischium, without spines; carpus–dactylus missing.

Pleopod 1 peduncle 4 times as long as wide, with uneven lateral tubercles, with 5 cincinnuli; endopod about as long as exopod, 1.3 times as long as peduncle; exopod with square distolateral angle, with oblique groove on posterior face. Pleopod 2 peduncle rectangular; exopod slightly shorter than endopod; endopod with simple acute appendix masculinis, 0.7 times length of ramus.

Uropod peduncle oval, 4 times as long as wide, with 18 teeth along free margin, 2 teeth at mesiodistal angle; exopod triangular with rounded apex, as long as wide; endopod slightly tapering, 1.5 times as long as wide, with 2 terminal setae.

Etymology: For Clarence Island near the type locality.

Remarks: Dolichiscus clarencensis lacks the dorsal and lateral spines or tubercles seen in other species from the Southern Ocean, such as D. anna (Beddard, 1886), D. debilis (Hale, 1937), D. diana Schultz, 1981, D. ferrazi Pirez & Sumida, 1997, D. gaussianus (Vanhöffen, 1914), D. georgei Kussakin & Vasina, 1980, D. hiemalis (Hodgson, 1910), D. ludmilae Kussakin & Vasina, 2001, D. marinae Kussakin & Vasina, 2001, D. mirabilis Brandt, 1990, and D. spinisetosus Brandt, 1999. The new species resembles more closely D. brandtae Pires & Sumida, 1997 found at a similar depth northeast of King George I. but differs in having short spines along the margins of the pleotelson, uropod and pereopods, absent in D. brandtae.