Leptochiton hiriensis Schwabe & Lozouet 2006, n. sp.
Creators: name: Schwabe, Enrico
name: Lozouet, Pierre
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Polyplacophora
Neoloricata
Leptochitonidae
Leptochiton
Leptochiton hiriensis

description: Leptochiton hiriensis n. sp.
(Figs 2-4; 10A)
TYPE MATERIAL. — Holotype: type locality (MNHN).
Paratypes: type locality, 7 paratypes (MNHN). — Stns 16 and 30, 2 paratypes (ZSM).
TYPE LOCALITY. — French Polynesia, archipel des Australes, Rapa, Baie de Hiri, RAPA 2002, stn 9, 27°37.3’S, 144°22.2’W, 3-24 m, coral bottom.
ETYMOLOGY. — From the type locality.
MATERIAL EXAMINED. — A total of 25 specimens (3 lots). French Polynesia. Rapa Island, Baie de Hiri, 27°37.3’S, 144°22.2’W, RAPA 2002, stn 9, 3- 24 m, coral bottom, 8 spms. — W of Tauna islet, 27°36.3’S, 144°18.4’W, RAPA 2002, stn 16, 5 m, dead corals, 13 spms. — Pointe Mei, 27°38.2’S, 144°18.2’W, RAPA 2002, stn 30, 16- 20 m, dead corals, 4 spms.
DIAGNOSIS. — Elongate-oval animal, minute.Tegmentum strongly sculptured with comarginal ridges. Dorsal girdle with strongly ribbed scales and long needles. Ventral girdle with smooth, elongate-rectangular scales. Radula with c. 80 rows, about 365 µm in length. Central tooth broad rectangular with a simple inwardly directed blade, second lateral with an elongate-rectangular, tridentate head. Ctenidia unknown.
DESCRIPTION
Minute, to 1.4 mm in length, with an elongateoval outline. Dorsum evenly convex. Head valve comparatively large, posterior margin widely V-shaped with a shallow notch in the centre. Intermediate valves rectangular, without apex, posterior margin concave. Tail valve semicircular with a central, slightly elevated, posteriorly directed mucro. Postmucronal slope flat and straight. Lateral areas of intermediate valves moderately elevated.
Tegmentum sculptured with relatively prominent, comarginal ridges (12 in the head valve of the holotype), which are stronger towards the outer margin and lateral areas. Central part of the valves more or less distinctly sculptured and appears partly smooth, except for concentric granulated growth marks. Ridges bearing inconspicuous granules. Each granule with a central macropore of 3.5 µm in diameter. Micropores seem to be present among the granules, on their bases.
Articulamentum builds thin apophyses, triangular in intermediate valves, rectangular in tail valve. They are widely separated and not connected by a sutural lamina.
Perinotum (Fig. 2) very narrow. Dorsally covered with strongly ribbed (with up to 15 ribs), imbricated, rectangular scales, which are 34.5 × 20 µm in size (in situ). There are also long, smooth needles (78.3 × 8.4 µm), which are irregularly arranged among the scales. Suturally, there are longitudinal-ribbed (probably up to 12 ribs) needles, which reach c. 50 × 8.3 µm. Ventral girdle scales (Fig. 4E) smooth, rectangular to oval (24-30 × 11.3-12.7 µm) with a small nipple-like tip. Marginal girdle elements consist of: finely ribbed (up to 12 ribs), rectangular scales (57.3 × 18.7 µm) with a sharply pointed distal end; and long, slender, smooth needles, attaining 48.5 × 3.8 µm.
Radula of a 1.3 mm specimen from stn 16 about 365 µm in length, consists of c. 80 rows. Central tooth rectangular, 5.6 × 5.2 µm, with a simple inwardly directed blade. Second lateral tooth about 12.4 µm in length, with an elongate-rectangular tridentate head, measuring 7.2 × 4 µm. Central denticle sharp-pointed and longest. Radula cartilage 104 µm in length.
Due to the condition and the small size of the specimens the number of ctenidia could not be determined.
REMARKSThe species was found at 3-24 m depth on corals, but probably reaches its highest density at about 5 m. The high number of growth marks, the constant size and the relatively “thick” valves lead us to assume that this species is full-grown. The minute size, in combination with the strong sculpture make it easy to distinguish it from other Indo-Pacific
shallow-water species so far known.
description: Published as part of Schwabe, Enrico & Lozouet, Pierre, 2006, Chitons (Mollusca, Polyplacophora) from Rapa, the southernmost island of Polynesia, pp. 617-633 in Zoosystema 28 (3) on pages 619-621, DOI: 10.5281/zenodo.5754452