Lepidochitona, Gray, 1821

Sirenko, B. I., 2023, Lepidochitona bondarevi sp. nov. (Mollusca: Polyplacophora) from the Black Sea and its relatives, Ruthenica, Russian Malacological Journal (Berlin, Germany) 33 (4), pp. 149-165 : 153-164

Lepidochitona bondarevi sp. nov.

( Figs 1B, C, 8–16)

urn:lsid:zoobank.org:act:171C55DA-9552-

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Chiton polii . – Kowalevsky, 1883:1; Zernov, 1913: 245, part, non Chiton polii Philippi, 1836 .

Chiton marginatus .– Milachewitch, 1916: 142, part, not Chiton marginatus Pennant, 1777 .

Lepidochiton marginatus .– Jakovleva, 1952: 72, fig. 29, part, not Chiton marginatus Pennant, 1777 .

Lepidochitona corrugata . – Kaas, Van Belle, 1985: 86, fig. 40, map 19; Bondarev, Revkov, 2017: 15, part., not Chiton corrugatus Reeve, 1848 .

Lepidochitona (Lepidochitona) caprearum .– Dell’Angelo, Smriglio, 2001: 143, pls 46–48, figs 73–76; Micu 2004:88, part, not Chiton caprearum Scacchi, 1836 .

Lepidochitona caprearum . – Sirenko, 2015: 23; Teaca et al., 2010: 10, not Chiton caprearum Scacchi, 1836 .

Type material. Holotype ( ZIN 2470 ), and two paratypes ( ZIN 2471 , ZIN 2472 ), now disarticulated consisting of SEM stub of valves I, V, VIII, part of perinotum and radula, mount of part of perinotum and radula and vial with other valves,

Type locality. Black Sea, Crimea Peninsula, Fiolent Cape, 44°29′55″N, 33°29′20″E, 0.2 m

Etymology. Named after Igor Bondarev (FRC IBSS), specialist of gastropods who helped me to collect chitons off Crimea Peninsula.

Material examined. More than 600 spms. All of the material listed here is stored in ZIN. Black Sea , Zmeinij Island , 45°15′18″N, 30°12′15″E, 0–3 m, 6 spms, BL 3.0–8.0 mm, 20.09.2003 ; Crimea Peninsula, Tarkhankut Cape, 45°20′52″N, 32°29′46″E, 0 m, stones, 1 spm, BL 5.0 mm, August 1969 ; Kazachja Bight , 1 m, on Cystoseira sp. , 95 spms, BL 2.0–3.0 mm, 23.06.1971 ; Omega Bight , 20 m, on Phyllophora sp. 102 spms, BL 2.0– 3.5 mm, 25.02.1971 ; Fiolent Cape, 0.5–1.5 m, holotype ( ZIN 2470 ), 96 spms, BL 3.0–7.0 mm, 25.02.1984 ; Fiolent Cape, 0–0.2 m, 30 spms, BL 3.0–9.0 mm, 25.02.1984 ; Fiolent Cape,2.0–4.0 m, stones, 87 spms, BL 4.0–6.0 mm, 02.05.1984 ; Fiolent Cape, 0.3–0.7 m, stones, 25 spms, BL 3.0–7.0 mm, 02.05.1984 ; Fiolent Cape, 0.5–1.5 m, 26 spms, BL 3.0–7.0 mm, 22.05.1987 ; Fiolent Cape, 1–3 m, 46 spms, BL 3.0–8.0 mm, 21.05.1990 ; Golubaja Bight , 4–6 m, on Rapana venosa , paratype ( ZIN 2471 ), BL 5.5 mm, 6 spms, BL 2.0–6.0 mm, 12.08.2015 ; Omega Bight , 1–1.5 m, 50 spms, BL 4.0–8.0 mm, 11.02.1984 ; Kamishovaja Bight , 1.0 m, 1 spm, BL 5.0 mm, April, 1984 ; Kazachja Bicht , 11-12 m, 1 spm, BL 5.0 mm, 26.05.1977 ; Streletskaja Bight , 0.3 m, paratype ( ZIN 2472 ), 28 spms, BL 3.0– 5.5 mm, 17.09.2018 ; Streletskaja Bight , 0 m, 7 spms, BL 4.0–12.0 mm, 17.09.2018 ; Laspi Bight , 44° 25’ 43’’ N, 33° 42’ 39.2’’ E, 5 m, on Phyllophora , 6 spms, BL 3.5 –4.0 mm, June 1992 ; Yalta Bight , 10–12 m, 3 spms ( ZIN 229 ), BL 4.5 –7.0 mm, March, 1870 ; Kara Dag , 2–6 m, on Rapana venosa , 73 spms, BL 3.0– 6.5 mm, 27.08.1998 ; Kara Dag , 3 m, on Rapana venosa , 8 spms, BL 4.0–8.0 mm, 15.07.2004 ; Novorossijskaja Bight, 3 m, on Zostera sp., 1 spm, BL 5.0 mm, 06.1870 ; Gelendjik , 0.2 m, 12 spms, BL 2–4 mm, October 2015 ; Sukhum Bight , 0.5–2.5 m, 1 spm ( ZIN 235 ), BL 8.2 mm, May, June, 1876 ; Batum Port , 0-7,3 m 1 spm ( ZIN 222 ), BL 10.0 mm, May, 1910 ; Marmara Sea, Istanbul , 3 spms ( ZIN 213 ), BL 2.0– 3.5 mm .

Distribution. Black Sea from the Romanian coast and Zmeinij Island in the northwest, along the entire Crimean Peninsula, and to the port of Batum, as well as the Sea of Marmara, at depths from 0 to 20 m (more often found from 0 to 1 m).

Diagnosis. Chiton small, up to 8.0 mm, rarely up to 10-12 mm, color of tegmentum very variable, usually rose blotched with brown, black and blue patches in different, symmetrical patterns, head valve significantly wider than tail valve ( Table 1), valves subcarinated, little beaked, slightly elevated, postmucronal area long, mucro anterior. Tegmentum all over evenly covered with round or oval granules arranged in irregular quincunx pattern, each granule with about 7–15 pores of aesthetes. Slit formula 8/1/10. Girdle dorsally clothed with small, slightly flattened, pointed spicules with 7–8 longitudinal grooves around their upper half; tufts of long, bent, smooth needles scattered between the spicules. Upper part of first lateral teeth of radula is not higher than blade of central teeth. Eleven gills per side in holotype, arranged between valve IV and VII.

Description. Holotype small, BL 7.2 mm, elon- gate oval. Shell lowly elevated (dorsal elevation in valve V 0.26), back subcarinated, valves with side slopes weakly convex, little beaked. color of tegmentum olive with narrow longitudinal brown and blue spots usually rose blotched with brown, black and green patches in different, symmetrical patterns.

Head valve semicircular, significantly wider than tail one (ratio of width of head to width of tail valve 1.38) posterior margin widely V-shaped, intermediate valves broadly rectangular, front margin anteriorly elevated in valve II, little convex in valves III–VII, hind margin concave at both sides of the prominent apex, lateral areas weakly raised, side margins rounded. Tail valve with short antemucronal area, mucro anterior, ratio of length of postmucronal area to length of antemucronal area 1.68, postmucronal slope slightly convex.

Tegmentum all over evenly covered with round or oval granules arranged in irregular quincunx pattern, eventually forming more or less longitudinal rows in pleural areas of intermediate valves and flexuous rows in other areas of valves, each granule with about 7–15 pores of aesthetes.

Articulamentum well developed, white.Apophyses broad and rather long (ratio of length of tail valve to length of apophyse in tail valve 2.81), triangular in valve II, broadly rounded in other intermediate valves and trapezoid in tail valve, with concave front edge, insertion plates short, wide, slit formula 8/1/10, slits narrow, slit rays present on all valves, very fine, eaves narrow, porous.

Girdle narrow, colored in alternating bands of olive and white, dorsally covered with small, slightly flattened and bent, pointed spicules (55 x 31 μm) with 7–8 longitudinal furrows around them in upper half of spicules; tufts of 1–4 long, bent, smooth needles (up to 260 x 25 μm) scattered between the spicules, Marginal fringe formed by stout, longitudinally ribbed in dorsal side, sharply pointed needles (170 x 33 μm). Ventral part of girdle with two kinds of scales: one row of sharply pointed scales (100 x 25 μm) along margin and sharply pointed scales (60 x 21 μm) in other part of hyponotum.

Radula of holotype 2.0 mm long with 27 rows of mature teeth. Central tooth short, tulip-shaped with a wide, straight blade, Upper part of first lateral teeth of radula is not higher than top of central teeth, major lateral teeth with tridentate cusps, central denticle slightly larger.

Holotype has 11 long gills per side arranged from valve IV to valve VII.

Remarks. Intraspecific variability in the new species is noticeably expressed in the ratios of different parts of the shell valves ( Table 1). The values of ratios of different parts of the valves overlap in some cases, which does not always allow them to be used. How- ever, a number of features of the shell, perinotum, and radula support the opinion that this is definitely a new species. The following characters distinguish the new species from the second Black Sea species of this genus, Lepidochitona cinerea , which is often found in the same biotopes with the new species. L. bondarevi sp. nov. differs from L. cinerea in having head valve noticeably wider than tail valve (ratio of width of head to width of tail valve 1.16–1.38 in L. bondarevi sp. nov. and 1.00– 1.16 in L cinerea from the Black Sea); lower ratio of length of tail valve to length of apophyse in tail valve (2.81–3.70), (vs. 3.80-4.89 in L. cinerea from the Black Sea); longer postmucronal area than antemucronal area (ratio of length of postmucronal area to length of antemucronal area 1.42–2.17, vs. 1.00– 1.08 in L cinerea from the Black Sea); 7–8 longitudinal grooves around dorsal spicules in upper half of them (vs. no grooves or 1–2 very short grooves on the top of spicule in L. cinerea from the Black Sea); the first lateral teeth never rise above the top of the central tooth (vs. the first teeth always rise above the top of the central tooth in L. cinerea ). Aditionaly, new species has longer apophyses than L. cinerea ( Table 1).

The new species is closest morphologically to five other species inhabiting the Mediterranean Sea and the eastern Atlantic coast, namely L. caprearum (Scacchi, 1836) , L. monterosatoi Kaas, Van Belle, 1981 , L. piceola (Shuttleworth, 1853) , L. canariensis (Thiele, 1909) , and L. granpoderi Dell’Angelo, Sirenko, Anseeuw, 2022

The main differences of L. bondarevi sp. nov. from L. caprearum ( Figs 17–19 ) are the following: ratio of width of head to width of tail valve 1.16–1.38 (vs. 1.40–1.45 in L. caprearum ), ratio of length of tail valve to length of apophyse in tail valve 2.81–3.70 (vs. 1.50–1.63 in L. caprearum ), ratio of length of postmucronal area to length of antemucronal area 1.42–2.17 (vs. 1.00– 1.14 in L. caprearum ), dorsal spicules have 7–8 longitudinal grooves around their upper half (vs. 16–18 sharp, longitudinal ribs around spicule in L caprearum ). The number of aesthetes on the tegmental granules 7-15 (vs. 16-20 in L. caprearum . Moreover the new species has smooth dorsal needles (vs. ribbed dorsal needles in L. caprearum ).

L. bondarevi sp. nov. differs from L. monterosatoi by having grooves in pointed dorsal girdle spicules (vs. spicules somewhat pitted at the round top in L. monterosatoi ), smooth dorsal needles (vs. finely longitudinally grooved needles in L. monterosatoi ), front margin of apophyses in tail valve concave (vs. straight in L. monterosatoi )

The new species differs from L. piceola by having subcarinated valves (vs. regularly rounded in L. piceola ), slilghtly convex front margin (vs. regularly concave front margin in L. piceola ).

L. bondarevi sp. nov. differs from L. canariensis by having pointed spicules with 7–8 longitudinal grooves around them in upper half of spicules (vs. oval spicules on a narrow, striated base embedded in the girdle tissue in L. canariensis ), postmucronal slope slightly convex (vs. postmucronal slope concave in L. canariensis )

The new species differs from L. granpoderi in that the upper part of the first lateral teeth of radula is not higher than the blade of the central teeth (vs. the upper part of the first lateral teeth of radula is noticeably higher than the blade of the central teeth in L. granpoderi ) and in that the pores of aesthetes are located only on the granules (vs. the pores of the aesthetes are located on and between the granules in L. granpoderi ).

The new species often behaves like a true phyto- philic species. Young individuals with body length up to 2.0– 3.5 mm often form mass settlements on thallus of Cystoseira sp. and Phyllophora sp. Larger specimens can be found on the shells of the gastropod mollusk Rapana venosa Valenciennes, 1846 and on stones.

The new species belongs to the group of brood- ing juveniles in the pallial groove to the trochophora stage [ Sirenko, 2015]. In the beginning of May 1984, females of L. bondarevi sp. nov. with eggs and lar- vae that had not grown out of the outer shell were collected in the Black Sea near the southern coast of Crimea at a depth of 0 to 0.3 m.

Figures

FIG. 17. Lepidochitona caprearum, Mediterranean Sea, Capri Island, intertidal, on rocks, BL 8.0 mm. A. Head valve, dorsal view. B. Valve II, dorsal view. C. Valve IV, dorsal view. D. Valve VIII, dorsal view. E. Valve V, ventral view. F. Valve IV, tegmentum sculpture in central area. G. Valve IV, frontal view. H. Valve VIII, lateral view.