Lucilina sp.

Dell’Angelo, Bruno, Gori, Sandro, Baschieri, Leonardo & Bonfitto, Antonio, 2010, Chitons (Mollusca, Polyplacophora) from the Maldive islands, Zootaxa 2673 (1), pp. 1-38 : 16-18

Lucilina sp.

( Figures 6A–O , 12G , 13I–K )

Material examined: M07: 1 spm (juv., 4 x 2.5 mm, Fig. 12G ); M13: 6 valves (2 head and 4 intermediate); M20: 2 valves (1 head and 1 intermediate); M26: 1 head valve; M65: 7 valves (2 head, 2 intermediate and 3 tail); MLD02A: 8 valves (3 head, 3 intermediate and 2 tail); MLD05A: 1 head valve; LB05: 5 intermediate valves.

Description: The 30 studied valves are flesh to roseate-yellowish in colour.

Head valve semicircular, tegmentum sculptured with about 16–22 low, wide, radiating riblets, decorated with flat, inverted V-shaped warts directed towards the umbo, and with irregular rows of ocelli in shallow interstices . Intermediate valves with front margin sinuous, slightly concave in a wide central part, hind margin concave at both sides of the prominent apex, lateral areas little raised, separate from central areas by a granulose rib, a similar rib accompanying the posterior margin, the interspace showing a few irregular tubercles, ocelli confined to a narrow band close to the diagonal ridge, central area smooth. Tail valve triangular, front margin straight, mucro subcentral, not prominent, antemucronal area smooth, postmucronal area with many obsolete, subgranulose radial ridges, both areas separated by a more elevated, granulose rib.

Articulamentum white or roseate, apophyses rather wide, well rounded, slit formula 8–10/1/10–12, slits deep, teeth strongly grooved outside.

Remarks: The valves show similarity with those determined as Lucilina carnosa , but differ in certain features:

The 10 head valves available are similar to the ones of L. carnosa , except for the number of radiating riblets and consequently of the rows of the ocelli, up to 9–10 in L. carnosa (also considering the intraspecific variability). In the present material are six valves with 15–16 rows of ocelli, two valves with 17–18 rows, one valve with 19–20 rows, and one valve with 22 rows ( Fig. 6H ). The rows are irregular and not clearly visible, and it is difficult to count them. The 15 intermediate and five tail valves have pleural areas and antemucronal areas respectively completely smooth without any trace of longitudinal grooves ( Figs 13J–K ), which are always present in L. carnosa .

A species very similar to L. carnosa is L. indica ( Leloup, 1981) , considered by Kaas (1986) and subsequent authors ( Kaas & Van Belle 1998: 94) conspecific with L. carnosa , but recently revived by Schwabe (2004: 3153, figs 7, 8, 17G–H) in his study of material from Rodrigues, the smallest of the Mascarene Islands. L. indica has the head valve sculptured with 40 granulated, radially arranged ribs, and ocelli situated between the ribs, pleural areas with 11 weakly granulated, longitudinal ribs (on each side of the jugum), and tail valve semicircular (and not subtriangular as in L. carnosa ). These characters do not match with those of our valves, also if the general appearance is similar (the general valve surface is stronger sculptured in L. carnosa than in L. indica ), as can be seen comparing with Fig. 12H , that shows the holotype of L. indica (already illustrated in Schwabe 2004: fig. 17H). So, we prefer to leave the collected material undetermined, as Lucilina sp.

Regarding the only available juvenile living specimen (M07, Figs 6A–O , 12E ), we have the same problems with determination. This specimen is very similar in general appearance to L. indica (compare with the Fig. 12F of the holotype), but differs in several characters: the valve’s surface is smooth, the number of ocelli is reduced, the perinotum spicules differ from those of L. indica .

Distribution: Lucilina sp. is known only from the Maldive Islands.

Figures

FIGURE 6A–O, Lucilina sp., Maldive. A–G, juvenile living specimen, M07. A, dorsal view of the complete specimen. B, close-up of the head valve. C, close-up of the tail valve. D, ocelli in the lateral area of intermediate valves. E, close-up of Fig. D, showing the ocelli. F, lateral view of the tail valve. G, perinotum elements in situ. H–J, head valve, MLD02A, dorsal, lateral and frontal views, respectively. K–L, intermediate valve, M13. K, dorsal view. L, detail of the sculpture. M–O, tail valve, M65, dorsal, lateral and posterior views, respectively. Scale bars 1 mm: A, K; 500 µm: H–J, L–O; 100 µm: B–D, F; 10 µm: E, G.

FIGURE 12A, Parachiton hylkiae mauricejayi Schwabe, 2002, living specimen, Maldive, LB03B, length 12.8 mm. B, Ischnochiton albinus Thiele, 1911, living specimen, Maldive, M13, length 5.2 mm. C, Ischnochiton feliduensis E.A. Smith, 1903, Maldive, Felidhoo Atoll, Holotype, NHM 1903.9.17.25, length 6 mm. D, Tegulaplax hululensis (E.A. Smith, 1903), living specimen, Maldive, M28, length 10.5 mm. E–F, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), length 6.6 mm. G, Lucilina sp., living specimen, Maldive, M07, length 4 mm. H, Lucilina indica (Leloup, 1981), holotype (MNHN), Madagascar, Tuléar, length 8 mm. I, Acanthopleura miles (Carpenter in Pilsbry, 1893), living specimen, Japan, Okinawa, Sesoko Island, length 29.2 mm. J, Schizochiton incisus (Sowerby, 1841), living specimen, Indonesia: inside lagoon of Woka Island, off South Halmahera, 1°2.02’S, 128°13.97’E (ZSM Mol 20052075), length 40 mm. K, Acanthochitona penicillata (Deshayes, 1863), living specimen, Maldive, MLD04A, length 6.5 mm. L, Craspedochiton cf. laqueatus (Sowerby, 1842), living specimen, Maldive, M59, length 13.5 mm. M–Q, Craspedochiton laqueatus (Sowerby, 1842), NHM type material, Philippines, Mindoro, Calapan. M, lectotype (NHM 1988071/1), length 17.4 mm. N, paralectotype (NHM 1988071/2), length 17.5 mm. O–Q, paralectotypes (NHM 1988071/3-5), length respectively 16, 13.2 and 11.3 mm. R–S, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Maldive, M07, length ca. 11.7 mm. T, Cryptoplax burrowi (E.A. Smith, 1884), living specimen, Indonesia, ZSM Mol 20033081, length 25.4 mm. U–X, Cryptoplax burrowi (E.A. Smith, 1884), NHM 1992 053, syntypes, H. Cuming colln., Port Adelaide, S. Australia, length respectively 56.4, 38.5, 47 and 45.1 mm.

FIGURE 13A–B, Callochiton sp., S. Nilandu Atoll, Maldive, NHM 1903.4.11.71 (living specimen collected by J.S. Gardiner), close-up of the head and tail valves. C–H, Lucilina carnosa (Kaas, 1979), valves, Maldive. C–D, head valves, M13, showing differences in the number of ocelli rows, widths 3 and 3.1 mm, respectively. E, intermediate valve, M13, width 3.5 mm. F, tail valve, M13, width 3.3 mm. G–H, anomalous tail valve, dorsal and posterior views, respectively, M20, width 3.2 mm. I–K, Lucilina sp., valves, Maldive. I, head valve, M13, width 3.1 mm. J, intermediate valve, M20, width 4.7 mm. K, tail valve, M65, width 3.4 mm. L–M, Craspedochiton cf. laqueatus (Sowerby, 1842), head and intermediate valves, Maldive, M65, widths 5.7 and 5.2 mm, respectively. N, Craspedochiton sp., tail valve, Maldive, M65, width 5.8 mm. O–R, Cryptoplax burrowi E.A. Smith, 1884, NHM 1881.11.1.100, syntype, detached valves, coll. Coppinger, Port Molle, Queensland. O–P, intermediate valve, length 4 mm, dorsal and right lateral views, respectively. Q, intermediate valve, length 4.2 mm. R, head valve, length 3.5 mm.