Hydroniscus watlingi, George, 2004

George, Robert Y., 2004, Deep-sea asellote isopods (Crustacea, Eumalacostraca) of the north-west Atlantic: the family Haploniscidae, Journal of Natural History 38 (3), pp. 337-373 : 363-365

Hydroniscus watlingi n. sp.

(figure 14)

Diagnosis. Hydroniscus with cephalic rostral lobe broad, apically truncated and extending beyond the anterolateral angles of the cephalon. Pleotelson without any posterolateral projection. Uropods lacking. In ventral view, anal plates show crenulated edges at apex, and infra-uropodal spines are distinct.

Material examined. Holotype: female, length 2.9 mm, width 0.9 mm. USNM Cat. No. 138682.

Type locality. R / V Eastward Sta. G-6228, site Sigma over the Carolina continental rise. Also collected from the following stations : R / V Eastward Sta. G-7813 at site Beta over the Carolina lower slope, three female specimens ; R / V Eastward Sta. G-7814 at site Beta over the Carolina lower slope, two female specimens ; R / V Eastward Sta. G-6228 at site Sigma over the Carolina continental rise, two female specimens ; R / V Eastward Sta. G-7798 at site Alpha-A at the base of the west side of the Bermuda Pedestal, north-west Atlantic, one female specimen .

Etymology. This new species is named in honour of the American carcinologist Prof. Les Watling of Darling Marine Laboratories, University of Maine.

Description. Body about three times as long as wide. Cephalon with a large rostral lobe, truncated anteriorly. Posterolateral angles of cephalon produced to half the length of the rostral lobe. Cephalon as long as the anterior two pereonites combined. First pereonite longer than the second. Pereonite 4 one-third longer than pereonite 3. Pereonites 5–7 fused with the pleotelson, with slight indication of fusion at the lateral extremities. Pleotelson conical in shape, apex somewhat truncated.

Antenna 1 with a flagellum of five articles. Antenna 2 about twice the length of antenna 1, with flagellum composed of nine articles. Uropods absent.

Remarks. This new species exhibits a close morphological similarity with a northern species H. abyssi Hansen, 1916 which was collected from the Davis Strait south-west of Greenland at 3520–3610 m during the Danish Ingolf expedition. Both species lack a sharp posterolateral angle or projection to the pleotelson, the anal cavity is separated from the branchial chamber, they lack uropods and have infrauropodal spines. However, these two species are clearly differentiated in several characters, such as the anterolateral angles of the cephalon, which are rounded and prominent in H. watlingi but with a minute conical spine in H. abyssi ; posterolateral extremities of pereonite 5 projecting in H. watlingi but coalesced in H. abyssi , and the pleonal apex is truncated in H. watlingi but rounded in H. abyssi .