Thermoarcturus venezuelensis Paul & Menzies, 1971

Poore, Gary C. B., 2015, Thermoarcturidae, a new crustacean family of three genera (Isopoda: Valvifera), Zootaxa 4007 (3), pp. 409-418 : 414-417

Thermoarcturus venezuelensis Paul & Menzies, 1971

Figs 4, 5

Thermoarcturus venezuelensis Paul & Menzies, 1971: 33 –34, figs 6, 7.— Kensley & Schotte 1989: 255, fig. 107h.

Holotype. Off Venezuela, 11°03’N, 64°37.5’W, 95 m, USNM 136427 (female, 4.5 mm)

Material examined. West Indies [ US Virgin Islands], Saint Croix, W of Frederiksted, [c. 17°S, 65°W], 500 fm [900 m], T. Mortensen, Ingolf Expedition, 18 Jan 1906, ZMUC CRU- 7102 (male, 8.8 mm); ZMUC CRU- 7141 (ovigerous female, 7.4 mm); ZMUC CRU- 7142 (4 mancas, 3.0– 4.2 mm; 9 males, 5.1–6.2 mm; 2 ovigerous females, 7.1 mm); NMV J58377 (1 manca, 3.2 mm; 5 males, 5.4–7.3 mm; 2 ovigerous females, 6.7 mm).

Description. Male, 8.8 mm. ZMUC CRU-7102. Cuticle with tomentum of fine setae over body and appendages. Body linear, strongly geniculate, length about 8.5 times greatest width (pereonite 3); head comprising 0.15 and pleotelson 0.25 total length. Head with pair of dorsolateral spines; pereonites 1–4 each with pair of sublateral acute tubercles long, less prominent on pereonite 1; pereonites 2–4 each with pair of triangular lateral supracoxal projections, slightly anteriorly directed, coxae unarmed; pereonite 5 with small tubercles on posterior margin; pereonites 5–7 each with median tubercle, pair of short dorsolateral tubercles and pair of supracoxal tubercles; pleonite 1 0.2 length of whole pleotelson, marked from it by dorsal and lateral groove, with pair of lateral tubercles; remaining pleotelson tapering in lateral profile, parallel-sided in dorsal view over two-thirds length, with pair of small lateral wings before tapering to acute apex.

d c n p4

e o p b

p5 p5 a k l m f g h i j a b d

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e Antennule 0.2 body length; flagellum with annular basal article, article 2 as long as peduncle, with 4 single and 3 pairs of aesthetascs. Antenna 0.75 body length, peduncular articles 4 and 5 of equal length, longer than articles 1– 3 together, articles 4 and 5 each with 4 and 5 pairs of long setae respectively; flagellum of 1 linear article and fine claw. Maxillipedal endite with 6 distal plumose setae; palp article 3 broadest, with distinct concavity on mesiodistal margin; article 4 ovate, with 3 marginal setae; article 5 with 4 distal setae.

Pereopod 1 with compact ischium–carpus, dactylus as long and closing on propodus; ischium with 1 marginal and 2 mesial pectinate setae; merus with 2 marginal and 2 mesial pectinate setae; carpus with 6 marginal pectinate setae; propodus with 6 marginal pectinate setae, mesial face with oblique rows of 1, 2, 8 and 6 pectinate setae; dactylus with 3 mesial and 2 marginal (extensor) pectinate setae, unguis half as long as dactylus body. Pereopod 2 carpus as long as ischium and merus together, convex on flexor margin, propodus and dactylus of similar lengths and slightly shorter than carpus; ischium and merus each with 2 marginal and 2 submarginal setae, carpus with 6 marginal and 4 mesial setae, propodus with 5 marginal-lateral and 3 mesial setae, dactylus with 4 setae near midlength, unguis half as long as dactylus body. Pereopods 3 and 4 progressively slightly longer than pereopod 2, of similar proportions and similar setation. Pereopods 5–7 of simple articles with few setae, progressively shorter.

Pleopod 1 exopod thickened proximally, with an oblique keel on anterior face (ventral in situ) ending in a rounded tooth at about midpoint; groove ending on a ventral subterminal distolateral lobe curved mesially; lamellar apex rounded, with long marginal setae, posterior (dorsal) surface with irregular row of sharp robust setae; endopod narrow, little longer than exopod. Pleopod 2 with appendix masculina tapering to sharp apex, 1.3 times as long as endopod. Pleopods 3–5 with lamellar rami, exopods shorter than endopods and with 1, 2 and 3 distal setae respectively.

Uropodal endopod triangular, with distal robust seta; exopod triangular, of similar dimensions to endopod, with 2 distal robust setae.

Ovigerous female, 7.4 mm. ZMUC CRU-7141. Body 4.6 times as long as wide. Pereopods 1–4 with broad overlapping oostegites; coxae with narrow ventral plates, without extended coxal supports; pereonite 5 with paired small midventral oval oostegites forming a hemispherical dome covering oopores.

Distribution. Caribbean Sea, off Venezuela; Saint Croix; 95– 900 m.

Remarks. Paul & Menzies’ (1971) description and small figures are sufficient to identify the species. The female holotype was examined by me in the 1990s but not reillustrated. However, the abundant new material from near the type locality could confidently be assigned to this species. The collection, especially the presence of both sexes, enables to species to be redescribed in more detail and the genus to be better diagnosed. The pleopod 1 of the male has a complex exopod unlike anything seen elsewhere in valviferans. It is figured from more than one aspect.