Alvania Risso, 1826: 140

Hasegawa, Kazunori, 2022, Bathyal Rissoidae (Gastropoda: Rissooidea) off the Russian Far East coast of the Sea of Japan, with redescription of Punctulum reticulatum Golikov, 1986, Ruthenica, Russian Malacological Journal 32 (2), pp. 85-92 : 86-87

Genus Alvania Risso, 1826: 140

Type species. Alvania europea Risso, 1826 , subsequent designation by Nevill [1885: 105].

Remarks. Criscione et al. [2017] suggested in their molecular phylogenetic study that all the rissoid species examined by them from bathyal depths in the Sea of Japan, e.g. Alvania cf. akibai , Frigidoalvania asura , Puctulum flavum and P. tanseimaruae , formed a well-supported clade with small genetic distances, and are clearly separated from Alvania sensu stricto. It is thus apparent that the following two species cannot ultimately be assigned to the genus Alvania . However, they are here provisionally retained therein, both because of the incompleteness of our understanding of the phylogenetic relationships of genera in the family and the absence of an appropriate genus to accommodate them.

“ Alvania” akibai ( Yokoyama, 1926)

( Fig. 2A )

Rissoa (Alvania) akibai Yokoyama, 1926: 275 , pl. 34, fig. 3 (see Hasegawa [2014] for more detailed synonymy).

Material examined. SoJaBio A 2-10, MIBM 39336 ( Fig. 2A ); SoJaBio B 6-7, MIBM 14492; SoJaBio B 7-7, MIBM 39342 [depth range: 455–1011 m].

Additional material examined (cited from Hasegawa, 2014). ZIN, non-registered, off Primorsky Krai, 44°48.5’N, 136°46.0’E, 373–494 m (voucher specimen of Punctulum sp. fide Golikov et al., 2001: 158) .

Distribution. Off Primorsky Krai coast on the northern slope, and from Musashi Bank to off Shimane Prefecture on the southeastern slope in the Sea of Japan, within the depth range of 220–1011 m.

Remarks. This species was originally described based on fossils from the Pliocene Sawane Formation on Sado Island in the Sea of Japan, and is characterized by the peculiar pockmarked protoconch sculpture [ Hasegawa, 2014: fig. 37D]. Its previously known vertical distribution range was 220–635 m, and that is significantly extended to 1011 m in the present study.

“ Alvania” nihonkaiensis Hasegawa, 2014

( Fig. 2B )

Alvania nihonkaiensis Hasegawa, 2014: 132–135 , figs 38 D–I, 39 D–F, 40 C–D, 43–45, 49H; table 8.

Material examined. SoJaBio A 2-10, MIBM 39337

(depth range: 455–456 m).

Distribution. Off Primorsky Krai coast on the northern slope, and from off Rebun Island south to off Oki Island on the southeastern slope in the Sea of Japan; off Abashiri in the Okhotsk Sea, within the depth range of 176– 635 m.

Remarks. As with the preceding one, this species is also characterized by its distinct protoconch morphology, in this case a zigzag sculpture.Although only one juvenile specimen was recognized among the present material, it was confidently identified based on this character. This is the first record of this species from the northern slope of the Sea of Japan, as well as in any Russian waters.

Figures

FIG. 2. Species of Rissoidae. A. Punctulum akibai (Yokoyama, 1926), SoJaBio stn. A2-10 (455-456 m), MIBM 39336. B. Punctulum nihonkaiensis (Hasegawa, 2014), SoJaBio stn. A2-10 (455-456 m), MIBM 39337. C-D. Frigidoalvania asura (Yokoyama, 1926), SoJaBio stn. B7-7 (470-528 m), MIBM 39340. E-F. Frigidoalvania tanseimaruae Hasegawa, 2014, SoJaBio stn. B6-7 (1,001-1,011 m). G-J. Punctulum flavum (Okutani, 1964); G-H, “shallow-water form”, SoJaBio stn. A2-10 (455-456 m), MIBM 14270; I-J, “deep-water form”, SoJaBio stn. A6-7 (2,511-2,534 m), MIBM 39334. All at the same scale; scale = 1 mm.