Cryptoplax burrowi (E. A. Smith, 1884)

Sirenko, Boris I. & Saito, Hiroshi, 2017, New species of chitons of the superfamily Cryptoplacoidea (Mollusca: Polyplacophora) from Vietnamese waters, Zootaxa 4299 (4), pp. 451-506 : 497-499

Cryptoplax burrowi (E. A. Smith, 1884)

Figs 39–42 , 44 G

Chiton (Chitonellus) burrowi E. A. Smith 1884: 85 .

Cryptoplax burrowi: Sykes 1907: 33 ; Iredale & Hull 1927: 96, pl. 11, figs13, 31, 32; Leloup 1940b: 15, fig. 5, pl. 3, fig. 3; Kaas 1979: 877; Kaas & Van Belle 1980: 20; 1998: 36; Kaas et al. 1998: 189; Slieker 2000: 54, pl. 15, fig. 11; Gowlett-Holmes 2001: 46; Schwabe 2005: 54, pl. 2, fig. 12; Burghardt et al. 2006: 30; Strack 2003: 15; Dell’Angelo et al. 2010: 26, figs 11A–L, 12R–X, 13O–R, 14B–C.

Type material. Syntypes, BMNH 1881.11.1.100 (1 spm) and BMNH 1992053 (4 spms).

Type locality. Port Molle , northern Queensland, Australia.

Material examined. South China Sea, Macclesfield Bank, 15°30´N, 114 º 51´E, 21 m, 1 spm, BL 29 mm, 1982, leg. V. Mjasnikov.

Description. Animal medium in size, vermicular. Anterior four valves in contact, remaining valves separated from each other. Valves V and VI apparently smaller than other valves. Color of tegmentum light brown in valve I, brownish orange in remaining valves. Girdle light brown with irregular patches of brown, light greenish gray and white.

Head valve bell-shaped, slightly longer than wide, wider than other valves; anterior slope convex. Intermediate valves small, oblong; valves V and VI apparently smaller than other valves. Jugum narrow wedge-shaped in valves II and III, very narrow, almost parallel-sided in valves IV–VIII. Tail valve with low mucro at posterior end. Tegmentum sculptured with pustules which are irregularly fused with each other peripherally in head valve, with 3–4 ribs which are slightly radiating from the apex in remaining valves; interspaces between ribs narrow. Jugum and ribs on lateropleural area convex at top. Macraesthete pores rather sparsely distributed, quincuncially arranged on jugum, also sparsely distributed along midline on ribs of lateropleural area.

Articulamentum thick, yellow in apophyses and light-brown in middle part of valves. Apophyses narrow, moderately projected anteriorly in valves II–VI, rather short in valves VII and VIII. Insertion plate moderate in length; posterior end of insertion plate only slightly expanded posteriorly in valve VIII. Slits rather wide and short. Slit formula 3/0/0.

Girdle moderate in width. Dorsal side of girdle beset with minute slightly curved, strongly grooved, clubshaped spicules, up to 77 µm x 26 µm, intermingling with large flattened, finely grooved spicules, attaining 233 µm x 68 µm and slender, parallel sided, finely grooved needles. Sutural tufts of up to 5 slightly curved, smooth blunt tipped needles, up to 610 µm x 45 µm. Marginal needles similar to those of sutural tufts, but often with several fine grooves, up to 418 µm x 22 µm. Ventral spicules flat, with 5–7 strong ribs on both surface, measuring 75–84 µm x 12–18 µm.

Gills extending from beginning of valve VIII to valve VII, composed of 10 ctenidia on each side.

Radula 4.6 mm long with 24 transverse rows of mature teeth. Central tooth small, deeply concave at upper half which is wider than the basal half, bluntly pointed at blade, strongly keeled near the base. First lateral (centrolateral) tooth with nodulous antero-dorsal corner and notch underneath nodulous portion. Major lateral tooth with tricuspid cup; denticles blunt at tip and about equal length.

Distribution. Queensland, Australia; Sulawesi, Lombok, Damar and Banda Islands, Indonesia; Sulu Archipelago, Philippines; Macclesfield Bank, South China Sea; Christmas Island; Wassin Island, Kenya, East Africa and Maldive Islands.

Remarks. The present species is characterized by the small valves V–VII which are distinctly smaller than other valves, the large flattened, finely grooved dorsal girdle spicules and the curved, finely grooved marginal spicules. The greenish coloration of the perinotum, which was described in the original description (E. A. Smith 1884), appears to be another characteristic feature of this species, but we need to examine more specimens to confirm it. This is the second record of the species on Macclesfield Bank. The first was mentioned in Leloup (1940b).

Figures

FIGURE 39. Cryptoplax burrowi, South China Sea, Macclesfield Bank, BL 29 mm: A. Valve I, dorsal view; B. Valve III, dorsal view; C. Valve V, dorsal view; D. Valve II, ventral view; E. Valve VIII, dorsal view; F. Valve III, detail of tegmentum in jugal and lateropleural areas; G. Valve VIII, lateral view; H. Valve III, rostral view.

FIGURE 40. Cryptoplax burrowi, South China Sea, Macclesfield Bank, BL 29 mm: A. Dorsal scales, marginal needles and ventral spicules; B, C. Dorsal spicules; D. Marginal needles.

FIGURE 41. Cryptoplax burrowi, South China Sea, Macclesfield Bank, BL 29 mm: A. Dorsal spicules; B, D. Radula; C. Ventral spicules.

FIGURE 42. Cryptoplax burrowi, South China Sea, Macclesfield Bank, BL 29 mm: A. Needle of tufts; B. Dorsal spiculees; C. Dorsal needle, D. Marginal needle; E. Ventral spicules. F. Head of major lateral tooth of radula; G. Central and first lateral teeth of radula. Scale bars: 100 µm.

FIGURE 44. Images of species of genus Acanthochitona and Cryptoplax: A. A. achates, near Da Nang, intertidal, on barnacles, BL 15 mm; B. A. biformis, Southern Vietnam, Cau Id., 13 – 17 m, on old shells, BL 11 mm; C. A condaoi n. sp., Gulf of Thailand, Vang Id., 9 – 11 m, on old shells, paratype, BL 6 mm; D. A. lanae n. sp., near Da Nang, intertidal, on barnacles, paratype, BL 12 mm; E. A. ostreaphila n. sp., Nha Trang Bay, Tre Island, Dambay Inlet, intertidal, mangrove community, on oysters, paratype, BL 12 mm; F. A. ostreaphila n. sp., Gulf of Tongking, Cat Ba Island, 0.5 m, on oysters, paratype, BL 5.5 mm; G. Cryptoplax burrowi, South China Sea, Macclesfield Bank, 21 m, BL 29 mm.