Astacilla frigida ( Hansen, 1916 ) Stransky & Svavarsson & Poore & Kihara, 2020

Stransky, Bente, Svavarsson, Jörundur, Poore, Gary C. B. & Kihara, Terue Cristina, 2020, Revision of Pleuroprion zur Strassen, 1903 (Holidoteidae) and re-evaluation of Spectrarcturus Schultz, 1981 (Arcturidae) (Crustacea, Isopoda, Valvifera), Zootaxa 4894 (1), pp. 1-52 : 45-49

Astacilla frigida ( Hansen, 1916) comb. nov.

( Figs 34–35 )

Arcturus hystrix .— Ohlin, 1901: 30, fig. 6a–r (non G.O. Sars, 1877).

Pleuroprion frigidum Hansen, 1916: 196–197 , pl. XV, fig. 7a–b.— Boone, 1920: 30–31.— Kussakin, 1982: 427–428, fig. 317. Material examined: Syntypes, ZMUC-CRU-6464 (1 adult female), ZMUC-CRU-9401 (1 juvenile male), ZMUC- CRU-9402 (1 adult female, 1 juvenile male, 1 adult male), ZMUC-CRU-9403 (1 male, 1 Manca II stage, 4 females), all from 72°53´N, 20°36´W.

Other material. ZMH-K-39770 (1 specimen, male, 8.5 mm length, ARK IX/2, station 179, Northeast Water Polynya , off Greenland) .

Diagnosis: Body of females with many long and narrow, bluntly pointed spines, spines forming neat row across each pereonite; five rows of spines across pereonite 4, additionally pair of spines between first and second row; pereonite 4 0.3 times body length, anteriorly paralell, narrowing posteriorly; 5.9 times longer than third pereonite; dorsally wider than pereonite 3. Pereonites 5 to 7 progressively shorter posteriorly; pleotelson oval, tapering towards rounded apex, with rows of spines across anterior and middle part of pleotelson, lateral margins with spines, distal end without spines. All pleonites fused into pleotelson; total length of pleotelson about combined lengths of pereonites 5 to 7. Eyes rounded, lateral. Antennula short, reaching little beyond distal end of second peduncular segment of antenna. Antenna long, about 0.7 of total body length; robust, with few large spines on second segment; large spines distally on third segment. Pereopod 1 with long and strong unguis on dactylus, pereopods 2–4 without dactylus. Three spines present on each basis of pereopods 5 to 7. Pereopods 5–7 with two ungues, secondary robust. Oostegites present on pereopod 1–4.

Male smaller than female. Pattern of spination as in females, spines smaller than in females and more robust; pereonite 4 narrow, dorsally about as wide (excluding spines) as pereonite 3. Penial plate laminar, with ridge on one side. Pleopod 1 with 5 coupling hooks on peduncle; exopod with proximal 2 plumose setae; 5 apical plumose setae respectively on endo- and exopode. Pleopod 2 endopod with 7, exopod with 11 (omitted in Fig. 35 ) apical plumose setae. Endopod slightly longer than exopod. Exopod fringed on outside with small fine setae. Appendix masculina without ridge, bifid, slightly longer than endopod. Uropod with exopod, inner ramus with 3 apical setose setae and one distal setose seta.

Remarks: Hansen´s (1916) description of this species was rather short and sparsely illustrated. No description was provided of the pereopods and the pleopods. Examination of the type material reveals that this species does belongs in neither Pleuroprion nor Spectrarcturus . The species is here transferred for the time being to Astacilla , as diagnosed by King (2003). Astacilla needs revision ( King 2003).

Distribution: East Greenland, at depths between 90 and 320 m ( Kussakin 1982; Brandt 1997).

Figures

FIGURE 34. Astacilla frigida (Hansen, 1916). Female syntype. A, habitus, dorsal view; B, habitus, lateral view; C, pereopod 2; D, pereopod 3. Scale: a, b = 1 mm (A, B).

FIGURE 35. Astacilla frigida (Hansen, 1916). A–C, male syntype (ZMUC CRU 9403), 8.5 mm. A, habitus, dorsal view; B, habitus, lateral view; C, pereopod 1, detail distally; D–J, male (ZMH–K–39770). D, pereopod 4, distal part; E, pereopod 5, distal part; F, pereopod 6, distal part; G, uropod, distal end; H, penial plate; I, pleopod 1 (apical setae omitted on exopod); J, pleopod 2. Scales: a, b = 1 mm (A, B); c–j = 0.1 mm.