Skenea profunda ( Friele, 1879 )

Nekhaev, Ivan O., 2022, Skenea profunda (Vetigastropoda: Skeneidae) in the central Arctic, Ruthenica, Russian Malacological Journal (Weinheim an der Bergstrasse, Germany) 32 (2), pp. 105-109 : 106-108

Skenea profunda ( Friele, 1879)

( Figs 1 A-B, 2 A-D, 3)

Cyclostrema profundum Friele, 1879: 272 .

Cyclostrema profundum : Friele, 1886: 34.

Lissospira profunda : Bouchet, Warén, 1979: fig 9A, 40-41. Skenea profunda : Warén, 1991: 65, figs 5C, 7B, 9E.

Type material. 4 syntypes of Cyclostrema profundum . ZMB 20999 , Greenland Sea , 77°58’N, 5°10’E, 2438 m, VØringen sta. 353, 10.08.1878 . 3 syntypes of Cyclostrema profundum . ZMB 21000 , Greenland Sea , 78°03’N, 11°18’E, 229 m, VØringen sta. 357, 12.08.1878 . Several syntypes of Cyclostrema profundum . ZMO D4423 , Norwegian Sea, 69°46’N, 16°15’E, 1187 m, VØringen sta. 192, 7.07.1877 (see remarks for more information).

Material studied. Arctic Ocean, 81°50’N, 136°14’E, 3700-3800 m, R/ V Sadko, sta. 101, 24.07.1938, ZIN 1907 (3 specimens) .

Description. Shell small, skeneimorph, almost white, with convex rounded whorls, suture deep, periphery of penultimate whorl rounded, convex. Teleoconch surface with 20-30 thin spiral ribs crossed straight irregular growthlines. Protoconch covered with flocculate sculpture, partly organized in 2-3 spiral ribs. Aperture almost round with wide rounded angle in upper part. Umbilicus wide, deep. Operculum multispiral, semitransparent.

Radula ( Fig. 2D): n-4-1-4-n. Central tooth wide with narrow cutting edge, cusps on cutting edge of laterals less developed than on marginals.

Soft body ( Fig. 2C) partially macerated. Pigmented eyes absent, head tentacles triangular short. Snout wide twice as long as tentacles. Propodial penis present in right corner of foot.

Measurements of largest specimen: shell height = 3.6 mm, aperture height = 2.3 mm, last whorl height = 3.1 mm, shell width = 3.8 mm, aperture width = 2.2 mm, diameter of protoconch = 0.6 mm, whorls number = 2.75, protoconch whorls number = 0.6.

Distribution. The species is known from the several localities in the northern Atlantic (the Norwegian and Greenland Seas) and Lomonosov Ridge in the Arctic Ocean, 2830–3800 m ( Fig. 3).

Habitat. Skenea profunda is associated with the sunken wood habitats [ Friele, 1886; Høisaeter, 2009; Holovacev et a l., 2011].

Remarks. Friele [1879] described Cyclostrema profundum based on material from three stations by the Norwegian North Atlantic Expedition in 1877 and 1878. Samples from the stations 353 and 357 are currently stored in ZMB and collected from depths of 2438 and 229 m, respectively. The shells collected at both stations are identical, but the depth at station 357 is very different from the depths in other habitats of Skenea profunda . Bouchet and Warén [1979] suggested that the shallow-water finding of this species is erroneous. This opinion was supported by Hoisaeter [2009], who pointed out that the shallow-water sample (st 357) was taken immediately after the deep-water one (st 353). The material from station 192 (1187 m) should be stored in ZMO, but has not been studied by previous researchers and has not been found by me in the museum. Since the lectotype for this species has not been designated, formally all three samples are syntypes. However, when discussing the distribution of this species, I do not take into account samples from stations 192 and 357.

Skenea profunda differs from other species of the genus by the combination of a large diameter of the embryonic shell (more than 500 µm) and the presence of a sculpture on the teleoconch, which consists of many spiral ribs starting immediately from the border between the adult and embryonic shells ( Fig. 2A). Skenea basistriata which is the most similar with Skenea profunda in shell shape and sculpture has only one rib in the initial part of the teleoconch ( Fig 2F). Adult specimens of Skenea profunda have the largest sizes among the NorthAtlantic andArctic representatives of Skenea : the shell width of Skenea profunda reaches 3.8 mm, whereas in other large species of the genus ( Skenea basistriata and Skenea turgida ) it usually does not exceed 3 mm [ Warén, 1991; 1993; Nekhaev, 2014; unpublished observation].

Figures

FIG. 1. Shells of Skenea from the Arctic. A, B. Skenea profunda, Arctic Ocean, 81°50’N, 136°14’E. C, D. Skenea basistriata; C. Barents Sea, 70°00’N, 33°30’E. D. Kara Sea, 76°40’N, 88°09’E, ZIN 1900/6.