Anatoma crispata ( Fleming, 1828 )

Nekhaev, I. O. & Krol, E. N., 2020, A review of the genus Anatoma in the Eurasian Arctic seas (Gastropoda: Vetigastropoda: Anatomidae), Zoosystematica Rossica (China) 29 (1), pp. 128-137 : 129-135

Anatoma crispata ( Fleming, 1828)

( Figs 1A–G; 2A–F; 3A–F; 4C)

Scissurella crispata Fleming, 1828: 385 , pl. 6, fig. 3.

Scissurella angulata Lovén, 1846: 20 .

Anatoma schioettei HØisaeter et Geiger, 2011: 103– 105, figs 48–60; Geiger, 2012: 1086–1089, figs 886–889, syn. nov.

Scisurella crispata : Herzenstein, 1885: 67; Thiele, 1928: 565.

Anatoma crispata : Golikov et al., 2001: 104 (partim); Kantor & Sysoev, 2006: 24, fig. 9A (partim); HØisaeter & Geiger, 2011: 90–94, figs 1–18; Nekhaev, 2014: 78; Geiger, 2012: 832–847, figs 674–680.

Anatoma sp. : Nekhaev & Krol, 2017: 2283.

Material examined. Norway, Norwegian Sea, Fin-

nmark, S. Lovén leg., 1 shell ( SMNH 4394 , lecto-

type of Scissurella angulata ). Russia: Barents Sea :

60 m, 71°54.26′N, 47°51.52′E, 18 Aug. 2006, R / V

Dal’nie Zelentsy, 2 spms, 1 shell; Motovskiy Bay, 197

m, 69°36.87′N, 32°16.43′E, 26 May 1996, M/S GS-

440, 4 shells ( ZIN 62141/36); Murman Coast, 42 m,

69°40.82′N, 31°37.00′E, 6 July 2005, R / V Dal’nie

Zelentsy, 1 shell; Murman Coast, 18–20 m, 69°36.5′N,

32°29.5′E, 29 May 1901, R / V Andrey Pervozvannyy ,

3 shells ( ZIN 1607 /7); Ura Inlet, 17 m, 69°22.70′N ,

32°54.88′E, 6 Oct. 2006, 4 shells; Ura Inlet, 158 m,

69°27′N, 33°08′E, 2 Oct. 2006, 1 spm; Ura Inlet, mouth of Shalimskaya Bay , 24–40 m , 13 Aug. 1887, 1 shell ( ZIN 1602 /1); Ivanovskaya Inlet , 54 m , 68°22.46′N, 38°32.30′E, 30 July 2008, R / V Dal’nie Zelentsy, 1 spm; Kola Inlet, 22 m , 69°16.81′N, 33°32.99′E, 28 May 2013, Yu.A. Zuev & S. V. Goldin leg., 4 shells ( ZIN 32142 /37); off Teriberka, 150–170 m , 6 Aug. 1884, 1 shell ( ZIN 1603 /2); Dal’ne-Zelenetskaya Bay , 66 m , 69°08.41′N, 36°04.54′E, 4 June 2009, R / V Dal’nie Zelentsy, 2 spms; Franz Joseph Land: 251 m , 80°44.19′N, 53°36.85′E, 23 Aug. 2006, R / V Dal’nie Zelentsy, 2 shells ( ZIN 62140 /35), 76 m , 80°31.60′N, 52°34.12′E, 29 Aug. 2007, R / V Dal’nie Zelentsy, 1 shell, 102 m , 79°52.05′N, 51°49.13′E, 24 Aug. 2006, R / V Dal’nie Zelentsy, 3 spms, 53 m , 80°14.5′N, 73°51′E, 14 Sept. 1936, R / V Sadko, 4 spms ( ZIN 1615 /15), Hooker I., Tikhaya Bay , 120 m , 25 Aug. 1992, R / V Pomor, 2 spms ( ZIN 58716 /34); Novaya Zemlya, Chernaya Inlet, 46 m , 70°35′N, 54°55′E, 8 Oct. 2000, R / V Dal’nie Zelentsy, 2 spms.; Kara Sea : 446 m , 80°58.5′N, 73°32′E, 9 Sept. 1936, R / V Sadko, 4 shells ( ZIN 1614 /14); 41 m , 80°11′N, 75°02′E, 18 Aug. 1934, R / V Sedov, 21 shells ( ZIN 37030 /20) .

Redescription. Shell small, globular, fragile, matt or slightly shiny, from white to yellowish, semitransparent or opaque. Spire low; upper whorls from rounded to stepped; body whorl relatively large, lenticular; shell base convex. Protoconch of 0.75–1.0 whorls, with sculpture of coarse flocculae which usually tending to form two or three spiral riblets. Diameter of protoconch from 210 to 320 µm, nucleus 70–180 µm wide. Teleoconch I of 0.25–1.0 whorls. Teleoconch II of 0.7– 2.0 whorls. Upper parts of body whorl with 3–14 thin spirals riblets, shell base with 7–21 ones. Teleoconch I with 13–25 axial riblets, sometimes weak spiral cord present in position of selenizone ( Fig. 2C). First whorl of teleoconch II with 33–65 axial riblets. Body whorl with 43–80 axials. Axials irregularly spaced ( Fig. 1F). Spirals weaker than axials. Spirals and axials on base forming reticulate pattern. Aperture rounded; outer lip above selenizone arciform or almost straight, out- er lip under selenizone and columellar lip round- ed. Umbilicus open, deep with distinct funiculus. Space between selinizone ( Fig. 1D, s) and suture of subsequent whorl variable ( Fig. 1G).

Mean values of measurements of 34 specimens: NW 2.9 ± 0.04, SH 1.38 ± 0.06 mm, BWH 1.25 ± 0.05 mm, AH 0.93 ± 0.03 mm, SW 1.73 ± 0.06 mm, AW 0.90 ± 0.03 mm. Measurements of the largest specimen (Franz Josef Land, 76 m): NW 3, SH 2.05 mm, BWH 1.82 mm, AH 1.30 mm, SW 2.34 mm, AW 1.17 mm.

Radula ( Fig. 3A–F): rachidian tooth trapezoidal, with prominent central denticle and 3–6 narrow pointed denticles on either side. Five lateral teeth with narrow pointed denticles. Lateral teeth 1–3 usually with 5–8 denticles. Fourth lateral tooth reduced, with distinct terminal denticle. Fifth lateral tooth with approximately 7–9 denticles. Tips of lateral teeth directed towards inner margin, rachidian and lateral teeth with slightly serrate edges. Inner marginal teeth with triangular tips directed towards outer margin, bearing approximately 7–9 narrow denticles. Outer marginal teeth spoon-shaped, with approximately 15–20 thin sharp denticles.

Distribution and habitat. Anatoma crispata is known from Baffin Bay, Greenland, Shetland Islands, Scandinavian coast, Barents Sea and northwestern Kara Sea ; the depth range is from 10 to 1083 m ( HØisaeter & Geiger, 2011; Geiger, 2012). The records of A. crispata from the northeastern Pacific ( Sirenko et al., 2013) probably refer to another species and need confirmation. Also, we did not find any specimens identified as A. crispata in ZIN collection. The findings of A. crispata in the Laptev Sea and East Siberian Sea (e.g. Gorbunov, 1946; Golikov et al., 2001) actually belong to A. schanderi . Anatoma crispata was found on different substrates. The minimum observed temperature at the collection site of living specimens was −0.8°C (Franz Josef Land).

Remarks. HØisaeter & Geiger (2011) described A. schioettei from the upper slope of Greenland. This species differs from A. crispata in having a wider sutsel (space between the beginning of selenizone and the suture of the subsequent whorl) and in having about 1.5 times as many or more distinct axials (e.g. 22 vs 15 on teleoconch I) ( HØisaeter & Geiger, 2011). However, these characters were variable in our material and numerous specimens displayed significant non-discrete variation: they differed in the position of selenizone ( Fig. 1G), in the number of axial riblets and in the distance between them ( Fig. 1F); the variability occurred even between the different parts of the same shell.

The number of axial ribs varied from 8 to 25 (mean 14.64 ± 0.74, n = 22) on teleoconch I and from 33 to 65 (mean 46.86 ± 1.09, n = 36) on the first whorl of teleoconch II. The hypothesis of normal distribution cannot be statistically rejected for both values (teleoconch I: Shapiro-Wilk test = 0.919, p = 0.073; first whorl of teleoconch II: Shapiro–Wilk test = 0.971, p = 0.45).

Both the forms also do not substantially differ from each other by other characters such as shell shape, sculpture and size of protoconch, and

I.O. Nekhaev & E.N. Krol. Review of the genus Anatoma radular morphology (see Figs 1B, 2B, 2E, 2F, 3D for typical A. crispata ; Figs 1A, 2A, 2C, 2D, 3A– C, 3E, 3F for typical A. schioettei ; and Figs 1C–D for transitional forms). Therefore, we consider A. schioettei as a synonym of A. crispata .