Mimachlamys sanguinea ( 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 : 305-307

Mimachlamys sanguinea ( Linnaeus, 1758)

( Figs 44–45 )

Ostrea sanguinea Linnaeus, 1758: 698 ; Dijkstra, 1999: 413 (identity), Figs 4 A-B (lectotype). Type locality:

‘in O. australiore’ [= Moluccas (Maluku). Indonesia, designated Dijkstra 1999].

Ostrea senatoria Gmelin, 1791: 3327 (based on Chemnitz 1784: 320, pl. 65, fig. 617 [non-binomial]). Type locality: ‘Oceano indico’.

Pecten senatorius ; Paes da França, 1960: 90, pl. 21, fig. 1.

Chlamys senatoria ; Barnard, 1964: 430; Spry, 1964: 15, pl. 2, fig. 71; Oliver, 1992: 74, pl. 13, figs 1a–b;

1995: 230, fig. 1003; Steyn & Lussi, 1998: 212, fig. 61.

Chlamys senatorius [sic]; Boshoff, 1965: 135.

Mimachlamys senatoria ; Dijkstra & Marshall, 1997: 101, pl. 9, figs 1–4 (references, synonymy, type data,

distribution, discussion); Dijkstra & Knudsen, 1998: 83 (further references and synonymy), pl. 4,

fig. 16.

Pecten testudineus Reeve, 1853 : pl. 34, fig. 160. Type locality: ‘Amboyna’ (Ambon, Maluku, Indonesia). Chlamys testudineus [sic]; E. A. Smith, 1910: 212.

Description: Shell height to 80 mm (average ca. 60 mm), suborbicular, LV more convex than RV, slightly equilateral, auricles unequal, umbonal angle ca. 90°. Both valves sculptured with numerous, regularly spaced, squamous primary radial ribs (22–27, usually 24), flanked by fine squamous secondary radial riblets, starting in the central part of the disc, and duplicating (or sometimes triplicating) near the periphery. Intercostal microsculpture with irregularly interrupted longitudinal or divaricating scratches on the central part, more antimarginal on the antero- and postero-marginal parts. Auricles with several homogeneous scaly riblets (6–10), more prominent on anterior one. Hinge line straight. Inner surface plicated near ventral margin. Cardinal crura well developed,

44 45

resilial teeth strong. Resilifer elongate, triangular and oblique. Byssal fasciole wide, byssal notch deep. Active ctenolium well developed with strong teeth (4–7) on suture. Colour extremely variable, either patterned or uniform.

Type material: O. sanguinea : lectotype, designated Djikstra 1999, in LSL, paralectotypes in LSL and MSNP. O. senatoria : lectotype ZMUC BIV-45, designated by Dijkstra & Marshall (1997: 102). P. testudineus : 3 syntypes BMNH (unregistered). See also Dijkstra & Knudsen (1998).

Regional data (all NMSA unless otherwise stated, selected records only): MOZAMBIQUE: Moçimboa da Praia (G4951, G4956: A. Ramalho); Quirimba Is. on Thalassodendron at LST, covered in dark red sponge, live (K435: RK); off Pemba, 15–18 m, muddy sand, live (HD6473); Nacala Bay, S Belmore, 1 m, small rock amongst Thalassodendron , live (H4506: K. J. Grosch); SW Lunga Bay, Thalassodendron , 0.6 m, gravelly sand, live (H4497: K. J. Grosch); Conducia Bay (H4668: K. J. Grosch); SW Conducia Bay, washed up during cyclone (H4500, H4667:K. J. Grosch); Conducia Bay (H4668: K.J. Grosch); SW Conducia Bay, NW of Choca, 0.6 m, Thalassodendron , muddy sand, on pebble, live (H4495: K. J. Grosch); SW Conducia Bay, Conducia, 1.5 m, Thalassodendron flat, on small rock, live (H4502:K. J. Grosch); Mozambique Bay, S Chembas, 0.6 m, Thalassodendron with rocks, muddy gravel (H4499: K. J. Grosch); W shore Mozambique Island, on Thalassodendron in soft sand (H4493: K. J. Grosch); Bazaruto Is., live, 25–30 m, muddy sand and rubble (HD4392); Benguera, North Bay (G3464: E. Roscoe); Santa Carolina Island, West Reef (G960: E. Roscoe); reef between Santa Carolina Island and mainland (G4630: E. Roscoe); between Bazaruto Island and mainland, 3–15 m, in sponge, live (F7914: R. Cruickshank); off Inhassoro, 3–15 m, live (F8762: R. Cruickshank); Inhambane (F7106: R. Cruickshank); Inhaca Island, on Thalassodendron on muddy sandflats (9577: RK), same loc. (4487: P. Boshoff). SOUTH AFRICA: Zululand:SE of Kosi Bay, 48 m, sand and rubble,live (D8731); same loc., 45 m, sand, stones, large algae, live (S4836); same loc., 50 m, medium sand, algae, dead (D6236); off Dog Point, 74 m, sandstone rubble, gorgonians, live (S6520); off Gypsey Hill, 52 m, fine sand, dead (S5231: NMDP); SE of Rocktail Bay, 60 m, coarse sand, dead (S5231: NMDP); off Sodwana Bay, 61 m, sand, dead (S3852: NMDP); Two Mile Reef, Sodwana Bay, 10–15 m, deep crevice in rock, live (D5200: D. Herbert). Natal: Durban (2412-3, 4480:H.C. Burnup);offAmanzimtoti, 180 m, medium sand, dead(D1234); Aliwal Shoal, off Umkomaas, 25–28 m, dead (S8807: D. Herbert). Transkei: off Whale Rock, 150–165 m, coarse sand, discoid corals, dead but in fresh condition (C2346).

Distribution: Throughout the tropical Indo-West Pacific (except Hawaii and French Polynesia) to southern Natal (with single record off Transkei).

Habitat: Living byssally attached to rocks or corals (in deep crevices it may dispense with a byssal anchor); in Mozambique generally attached to the marine angiosperm Thalassodendron on sand or muddy sandflats at LST or in a few metres. Toward the southern end of its range it inhabits deeper water, presumably correlated with the progressively offshore flow of the warm Agulhas current. Individuals may have a mutualistic relationship with sponges of the genera Mycale and Callyspongia ( Van Soest 1994).

Remarks: Mimachlamys sanguinea , better known as Chlamys s enatoria, is a common, widely distributed, polymorphic and polychromatic Indo-West Pacific species. Not only has it attracted numerous synonyms, but it has been confused with other species, such as M. crassicostata (G. B. Sowerby 2nd, 1842) and M. gloriosa (Reeve, 1853) . M. crassicostata (= P. nobilis Reeve, 1852 ) from the N. W. Pacific differs from M. sanguinea mainly in size (up to ca. 130 mm high), higher, more angular plicae and less well-developed secondary sculpture. M. gloriosa from the SW Pacific differs from M. sanguinea in having stronger lamellate sculpture on the primary ribs, and reduced secondary radial riblets which are developed only in late ontogeny (near periphery). The present specimens from Mozambique are morphologically similar to the type material of M. sanguinea , although the lamellae on the radial ribs are more prominent and more widely arranged.

The M. sanguinea -complex is still under study and will be treated elsewhere in more detail.

Figures

Figs 44–45. Mimachlamys sanguinea (Linnaeus, 1758): NMSA G3464, Benguera Is., Mozambique, pv, 53.2 x 50.1 mm. 44. LV exterior. 45. RV exterior.