Delectopecten musorstomi Poutiers, 1981

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 269-270

Delectopecten musorstomi Poutiers, 1981

( Figs 1–2 )

Delectopecten musorstomi Poutiers, 1981: 331 , pl. 1, figs 2–3; Dijkstra & Marshall, 1997: 88, pl. 8, figs 1–

6 (type data, distribution, discussion); Dijkstra & Knudsen, 1998: 51, pl. 7, figs 31–32. Type locality: Philippines, N of Lubang , 13°57' N, 120°16.5' E, 150–159 m.

Description: Shell fragile, height to ca. 5 mm, orbicular, equivalve, equilateral, anterior auricle slightly larger than posterior, umbonal angle ca. 120°. Prodissoconch height ca. 200 µm. Both valves sculptured with minute antimarginal radial striae and 14–20 fine, irregularly spaced, scaly radial lirae, plus fine regularly spaced, somewhat crenulated, commarginal growth lines; scales often damaged. External sculpture visible from the interior. Auricles continuous with disc and similarly sculptured. Anterior auricle of RV separated from disc by distinct suture, with 4–5 radial ridges and concentric lamellae, the latter strongly developed at dorsal margin. Hinge line straight. Byssal fasciole and

1 2

notch well developed. Active ctenolium with 2–3 teeth. Resilifer triangular. Valves transparent white, sometimes with white dots.

Type material: Holotype, MNHN (not registered), examined by HD.

Regional data: SOUTH AFRICA (all NMDP): Zululand: Sodwana Bay, 100 m, dead (A5823). S Natal: off Amanzimtoti, 300–305 m, medium sand, live (D1301); off Park Rynie, 140 m, sponge rubble, live (B3864); same loc., 136 m, sponge rubble, live (B3898); off Port Shepstone, 70 m, eroded shell, sponge rubble, live (B3672). Transkei: off Mtamvuna R., 111 m, sponge, live (E15); same loc., 120–140 m, live (E69); same loc., 140 m, sponge rubble, live (C817); same loc., 143 m, sponge rubble, live (C910); off Rame Head, 150–160 m, sponges, live (C1904); off Port Grosvenor, 110–115 m, sand, some mud, solitary corals, shells, dead (C1346).

Distribution: Philippines and Indonesia to New Caledonia and Norfolk Island ( Dijkstra & Marshall 1997), here extended to the Transkei shelf of South Africa.

Habitat: Sublittoral to bathyal, living byssally attached amongst sponge rubble on soft sediments (mud, sandy mud or muddy sand).

Remarks: South African specimens agree well with the holotype of D. musorstomi . This species is much smaller than either the Atlantic Delectopecten vitreus ( Gmelin, 1791) or the Indo-Pacific D. alcocki (E. A. Smith, 1904) , not exceeding about 5 mm in height against about 20 and 22 mm respectively. Juveniles of D. vitreus and D. alcocki can be distinguished from D. musorstomi by the absence of scaly radial lirae near the ventral margin. D. musorstomi is a new record for South Africa.

Figures

Figs 1–2. Delectopecten musorstomi Poutiers, 1981: NMSA C910, off Mtamvuna R., Transkei, 143 m, pv, 6.1 x 6.1 mm. 1. LV exterior. 2. RV exterior.