Lucilina lamellosa ( Quoy & Gaimard, 1835 )

Sirenko, Boris I. & Zhang, Junlong, 2019, Chitons (Mollusca: Polyplacophora) of Hainan Island and vicinity, South China Sea, Zootaxa 4564 (1), pp. 1-40 : 10-12

Lucilina lamellosa ( Quoy & Gaimard, 1835)

( Figs 3A, B , 5–12 )

Chiton lamellosus Quoy & Gaimard 1835: 386 , pl. 74, figs 29–32. Tonicia (Lucilina) lamellosa ; Kaas & Van Belle 1980: 71; 1998: 106; Kaas et al. 2006: 350 –352, fig. 147, maps 48, 61

(bibliography and synonymy). Tonicia lamellosa ; Saito 2000: 21, pl. 10, fig. 12. Lucilina lamellosa ; Schwabe 2006a: 102–104, figs 1C, 6A–F, 7; Schwabe et al. 2008: 22–24, fig. 5B (bibliography and

synonymy); Sirenko 2012: 80, pls. 13 F; 16 A; Saito 2017: 735, pl. 7, fig. 9.

Type material. Lectotype ( MNHN 6058 ) designated by Strack (1986).

Type locality. Tonga, Tongatapu (21°10’S, 175°13’W) .

Material examined. Lectotype ( MNHN 6058 ); South China Sea, Hainan Island. MBM 100297 , 55-610 , 1 spm, forma typical, BL 12 mm, 8 spms, forma costata, BL 6.0–19.0 mm, 20.04.1955; 55-640, 3 spms, forma typica, BL 14.0–15.0 mm, 14 spms, forma costata, BL 8.0–22.0 mm, 23.04.1955; Xincun, depth 0.5 m, on old corals 6 spms, forma costata, BL 9.0–15.0 mm, 21.04.1958, leg. O. Scarlato; Xincun, depth 1.0 m, on old corals, 2 spms, forma costata, BL 9.0–10.0 mm, 21.04.1958, leg. O. Scarlato; Xisha Islands , 58M-1246, 4 spms, forma typica, BL 25.0–29.0 mm; 1 spm, forma typica, BL 34.0 mm, 23.05.1981; MBM 100328 , 4 spms, forma typica, BL 16.0–28.0 mm, 1 spm, forma costata, BL 29.0 mm; Guangdong Province, 2 spms, forma costata, 10.0–15.0 mm; Submersed reef, R/ V Akademik Shirshov, 18°39’N, 111°40’E, depth 0.5–2.0 m, on old corals, 1 spm, forma typical, BL 15.0 mm, 25.07.1981,

Distribution. The species has a wide distribution in the Indo-Pacific: Andaman Sea, Vietnam, South China including Guangdong Province, Hainan Island and Xisha Islands, Australia and Samoa as well.

Remarks. While examining L. lamellosa , we found two forms: L. lamellosa forma typica ( Figs 3A , 5–6 ) and the new form L. lamellosa forma costata ( Figs 3B , 7–12 ). Both forms differ from each other in the sculpture of tegmentum of the pleural areas. Lucilina lamellosa forma typica has demonstrated the similarity of it with the lectotype (MNHN 6058) from Tonga. Both forms of L. lamellosa have a distinct diagonal ridge sculptured with concentric shingle-like ledges. In L. lamellosa forma typica, pleural areas are also sculptured with shingle-like ledges ( Fig. 5D ), whereas in L. lamellosa forma costata, the pleural areas are sculptured with longitudinal ribs ( Fig. 7E ). The latter form is similar to Lucilina nigropunctata ( Carpenter, 1865) in its sculpture of pleural areas. L. lamellosa forma costata differs from L. nigropunctata in having subtriangular pits on the central area and in the absence of radiating rows of small tubercles in lateral areas. Moreover, forma costata has the tail valve wider than the head valve and the longitudinal ribs do not curve towards the jugum as in L. nigropunctata . Lucilina lamellosa forma costata is also similar to L. truncata ( Sowerby, 1841) from the Philippines but differs from the latter in having longitudinal ribs on the pleural areas (vs. more or less concentrical, distinctly spaced, wavy grooves in L. truncata ), subtriangular pits on the central area (pits are unknown in L. truncata ). Both forms of L. lamellosa were found near Fujian Province, Hainan Island and Xisha Islands. The forma costata inhabits the coast of Guangdong Province. The examined specimen of L. lamellosa forma typica (BL 15.0 mm) has a radula of 4.2 mm in length and 27 gills extended from valve II to valve VIII. The slit formula of this specimen is 9/1/13. The radula of the specimen of L. lamellosa forma costata (BL 14.0 mm) is 4.5 mm long and its slit formula is 9/1/15. A smaller specimen of L. lamellosa forma costata (BL 9.0 mm) has a radula 3.5 mm long with 34 transverse rows of mature teeth and 20 gills extended from valve III to valve VII. The slit formula of this specimen is 9/1/14. The latter specimen is similar to L. mariae Kaas et al., 2006 in having longitudinal ribs on the pleural areas of the intermediate valves, but differs from it in having sparsely scattered subtriangular pits on the central area (vs. no pits in L. mariae ). Because both forms differ from each other only in the sculpture of the tegmentum of the pleural area and because there are specimens with intermediate sculpture, we refrain from describing a new subspecies or a new species. We assign a registration number of the Zoological Institute RAS (ZISP 2301) to Lucilina lamellosa forma costata.

Figures

FIGURE 3. Complete specimens of species of genera Lucilina, Onithochiton and Acanthopleura: A. Lucilina lamellosa forma typica, Xisha Islands, 58M-1246, BL 28.0 mm; B. Lucilina lamellosa forma costata, Hainan Island, 55-640, BL 21.0 mm; C. Lucilina tenuicostata, Hainan Island, stn 13, BL 10.0 mm; D. Onithochiton cf. hirasei, Guangdong Province, BL 29.0 mm; E. Onithochiton stracki, Guangdong Province, BL 19.0 mm; F. Acanthopleura loochooana, Hainan, stn 28, BL 26.0 mm.

FIGURE 5. Lucilina lamellosa forma typica, South China Sea, 18°39’N, 111°40’E, BL 15.0 mm: A. Valve I, dorsal view; B. Valve V, dorsal view; C. Valve VIII, dorsal view; D. Valve V, detail of tegmentum in central area; E. Valve V, rostral view; F. Valve VIII, lateral view.

FIGURE 6. Lucilina lamellosa forma typica, South China Sea, 18°39’N, 111°40’E, BL 15.0 mm: A, Dorsal scales; B. Radula; C. Ventral scales; D. Central and first lateral teeth of radula.

FIGURE 7. Lucilina lamellosa forma costata, Hainan, Xincun, depth 0.5 m on old corals, 21.04.1958, BL 14.0 mm: A. Valve I, dorsal view; B. Valve II, dorsal view; C. Valve V, dorsal view; D. Valve VIII, dorsal view; E. Valve V, detail of tegmentum in central area; F. Valve V, rostral view; G. Valve VIII, lateral view.

FIGURE 8. Lucilina lamellosa forma costata, Hainan, Xincun, depth 0.5 m on old corals, 21.04.1958, BL 14.0 mm: A. Dorsal and ventral scales; B. Marginal needles and ventral scales; C, Dorsal spicules; D. Ventral scales.

FIGURE 9. Lucilina lamellosa forma costata, Hainan, Xincun, depth 0.5 m on old corals, 21.04.1958, BL 14.0 mm: A. Radula; B. Central and first lateral teeth of radula.

FIGURE 10. Lucilina lamellosa forma costata, Hainan, Xincun, BL 9.0 mm: A. Valve I, dorsal view; B. Valve II, dorsal view; C. Valve V, dorsal view; D. Valve VIII, dorsal view; E. Valve IV, ventral view; F. Valve V detail of tegmentum in central area; G. Valve V, rostral view; H. Valve VIII, lateral view.

FIGURE 11. Lucilina lamellosa forma costata, Hainan, Xincun, BL 9.0 mm: A. Valve V, detail of tegmentum in pleural and lateral areas; B, C. Dorsal spicules; D. Ventral scales.

FIGURE 12. Lucilina lamellosa forma costata, Hainan, Xincun, BL 9.0 mm: A, B. Radula.