Haumea minuta ( Linnaeus, 1758 )

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 312-313

Haumea minuta ( Linnaeus, 1758)

(Figs 52–53)

Ostrea minuta Linnaeus, 1758: 696 ; Dijkstra, 1999: 397, fig. 8c (lectotype). Type locality: ‘in Oceano

Indico’.

Pecten inaequivalvis G. B. Sowerby 2nd, 1842: 50, pl. 19, figs 193–195; Reeve, 1852: pl. 1, figs 1, 6;

Deshayes in Maillard, 1863: 31; von Martens, 1880: 138; Melvill & Standen, 1898: 46. Type locality: Philippine Islands.

Haumea inaequivalvis ; Dijkstra & Kastoro, 1997:275, fig. 150 (references, type data, description, distribution,

discussion).

Description: Shell up to 30 mm high, orbicular (juvenile), obliquely suborbicular (mature), RV more convex than LV, inequilateral, auricles unequal, umbonal angle ca. 100–110°. Both valves with regularly spaced, prominent radial costae (18–20). Radial ribs near antero- and postero-margins weakly commarginally striated. Intervals with closely spaced commarginal lamellae. Anterior auricle larger than posterior. Auricles with weak radial riblets (2–4). Inner surface strongly plicated near ventral margin. Hinge line straight. Byssal fasciole narrow, byssal notch moderately deep. Resilifer oblique, triangular.Active ctenolium weak with 4–5 teeth on suture. Colour of LV black grey or

52 53

Figs 52–53. Haumea minuta ( Linnaeus, 1758) : NMSA H4962 , Lunga Bay , Mozambique, 18 m, pv, 28.2 x 29.9 mm. 52. LV exterior. 53. RV exterior .

reddish-brown, marked with few white spots and black or red streaks, RV more uniform whitish, creamy or pale brown.

Type material: Ostrea minuta : lectotype UUZM 158 (designated Dijkstra 1999) . Pecten inaequivalvis : lectotype BMNH 1994126 / 1, designated by Dijkstra & Kastoro (1997: 276); 2 paralectotypes BMNH 1994126 /2-3.

Regional data (selected records only, all NMSA unless otherwise stated): MOZAMBIQUE: Pemba, 18–20 m, sandy bottom, live (HD6625); SW Lunga Bay, 18 m, muddy gravel, Thalassodendron , live (H4962: K. J. Grosch); SW Conducia Bay, ca. 9 m, from gravel and sparse Thalassodendron , dead (H4966: K. J. Grosch). SOUTH AFRICA: Zululand (all NMSA, unless otherwise stated): off Kosi Bay, 45 m, fine muddy sand, dead (D6040); SE of Kosi Bay, 50 m, fine muddy sand, dead (D7851); same loc., 45–50 m, fine sand, algae, gorgonians, dead (D8871); same loc., 40 m, fine sand, dead (D8783); same loc., 40 m, shell rubble, dead (D8129); same loc., 50 m, coarse sand, shells, dead (D6975); same loc., 50 m, fine, slightly muddy sand, dead (D8331); off Hully Point, 50 m, fine sand, live (D7554); same loc., 60 m, shell rubble, dead (D6708); off Jesser Point, 42 m, medium sand, dead (D8548); same loc., 40 m, shell rubble, dead (D7146); off Sodwana Bay, 49–53 m, sand, live (S4754); off Cape Vidal, 75–80 m, broken shell, dead (E4524). Natal: Durban Bay, shallow dredgings, dead (A1737: RK).

Distribution: Throughout tropical Indo-Pacific, except Red Sea and Hawaii.

Habitat: Free-living (perhaps in colonies) on sandy or muddy sand bottoms with rubble or sediments at littoral to sublittoral depths. [ H. loxoides from Hawaii lives in dense colonies on beds of sand at 15 m depth ( Calabrese & Cook 1970: 3; Earle 1985: 4)].

Remarks: The present specimens from Mozambique and South Africa resemble the type material of Pecten minuta and P. inaequivalvis , although coloration is somewhat paler.

This species has not previously been recorded from Mozambique or South Africa.

Haumea loxoides from Hawaii is very similar to H. minuta , but has a more fragile and oblique shell. Juveniles of H. minuta could be confused with Haumea rehderi (Grau, 1960) , a small species (maximum height ca. 5 mm), occurring throughout much of the tropical Indo-West Pacific; it has more prominent radial costae with more widely set commarginal lamellae in their intervals.