Poroleda ushakovi Scarlato, 1981

Lisitsyna, Kseniya N. & Kamenev, Gennady M., 2024, New and rare bivalve species for the fauna of the Kuril Islands (northwestern Pacific Ocean): A study of materials collected over 70 years of expeditions (from 1949 to 2019), Zootaxa 5523 (2), pp. 231-253 : 237

Poroleda ushakovi Scarlato, 1981

( Fig. 2 G, H )

Poroleda ushakovi Scarlato, 1981: 213 , 214; photos 84–87.

Material examined: 13 specimens from the ocean and sea slopes of the northern Kuril Islands (Shumshu and Atlasova Islands) (386–810 m) .

Distribution: Sea of Okhotsk; northern Kuril Islands (135–810 m) ( Scarlato 1981; Kantor & Sysoev 2005).

Remarks: This is a new record from the region of the Kuril Islands. Previously, this species had only been found in the Sea of Okhotsk at a depth of 135–664 m ( Scarlato 1981). Huber (2010) synonymized Poroleda uschakovi Scarlato, 1981 , with Propeleda conceptionis ( Dall, 1896) . Having examined 43 specimens of P. uschakovi, Scarlato (1981) pointed out a great variability of the species. We examined the holotype and about 100 specimens of P. uschakovi and noted that this species varies in the position of the beaks, the relative height of the shell, the degree of inclination of the antero-dorsal and the concavity of the postero-dorsal shell margins. Nevertheless, comparison of this species with the syntypes of Leda conceptionis Dall, 1896 (USNM 107426, 122588, 34056) ( Coan & Valentich-Scott 2012) showed that P. uschakovi is well distinguished from P. conceptionis by a less elongate shell with beaks more shifted anteriorly, a more gently sloping antero-dorsal margin, sometimes being almost horizontal and forming a noticeable angle at its transition to the posterior margin, a narrower and upwardly curved rostrum, a more strongly curved ventral margin as well as sparse concentric ribs in the beak area. Therefore, we consider P. uschakovi to be a valid species.

Figures

FIGURE 2. New and rare bivalve species for the fauna of the Kuril Islands. (A, B) Acila divaricata (Kunashir Strait, 200 m, shell length 29.7 mm). (C, D) Acila insignis (Yuri Island, 1000 m, shell length 11.0 mm). (E, F) Nuculana ensiformis (Shikotan Island, 200 m, shell length 22.5 mm). (G, H) Poroleda ushakovi (Shumshu Island, 820 m, shell length 17.1 mm). (I, J) Robaia robai (Kunashir Strait, 300 m, shell length 16.3 mm). (K, L) Yoldia hyperborea (Paramushir Island, 215 m, shell length 19.0 mm). (M, N) Scanning electron micrographs of Huxleyia pentadonta (Paramushir Island, 214 m, shell length 2.3 mm). (O, P) Samacar kurilensis (Iturup Island, 265–270 m, shell length 16.5 mm). (Q, R) Tetrarca boucardi (Shpanberg Strait, 55 m, shell length 20.0 mm). (S, T) Limopsis oliveri (Urup Island, 50 m, shell length 9.0 mm). (U, V) Limopsis vaginata (Iturup Island, 600 m, shell length 26.3 mm).