Dolichiscus clarencensis, Poore & Black, 2024

Poore, Gary C. B. & Black, Jay R., 2024, Four new species of Valvifera (Crustacea: Isopoda) from ANDEEP cruises in the Weddell Sea, Zootaxa 5477 (3), pp. 295-314 : 306-308

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 .

Figures

FIGURE 10. Dolichiscus clarencensis sp. nov. ZMH K-65090 (holotype male, 10.2 mm). a, habitus (lateral) view; b, antennula, antennal peduncle article 2, head –pereonite 4 (dorsal); c, pereonite 7, pleonite 1, pleotelson (dorsal); d, pereonites 1–3, coxae 1–3 (oblique lateral, left side); e, head, clypeus, antennal peduncle articles 1–3; f, antennula; g, right uropod (lateral); h, right uropodal rami (mesial); i, maxilliped; j, right pleopod 1 (anterior face, marginal setae not shown); k, right pleopod 1 exopod (posterior face, marginal setae not shown); l, right pleopod 2 (anterior face, marginal setae not shown). Scale bars = 1 mm.

FIGURE 11. Dolichiscus clarencensis sp. nov. ZMH K-65090 (holotype male, 10.2 mm).a, pereopod 1; b, pereopod 1 propodus, dactylus) c, pereopod 2; d, pereopod 2 dactylus; e, pereopod 3; f, pereopod 4; g, pereopod 5; h, pereopod 6; i, pereopod 7 (basis–merus). Scale bars = 1 mm.