Pecten sulcicostatus G. B. Sowerby, 1842

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 286-288

Pecten sulcicostatus G. B. Sowerby 2nd, 1842

(Figs 20–22)

Pecten sulcicostatus Sowerby, 1842: 47 , pl. 13, figs 35–36; Sowerby, 1892: 89, pl. 5, figs 97–98; Dunker,

1858: 67, pl. 23, figs 4–6; Küster & Kobelt, 1888: 144, pl. 40, figs 6–7; Bartsch, 1915: 186;

Turton, 1932: 222; van Bruggen, 1961: 31, pl. 1, fig. 4; Barnard, 1964: 421; idem, 1974: 761; De

Villiers, 1976: 1, textfigs 1–10, tables i–vii; Rombouts, 1991: 53, pl. 19, fig. 8; Kilburn & Dijkstra,

1995: 271; Lussi, 1995: 1, 2, fig. 1; Steyn & Lussi, 1998: 212, fig. 863. Type locality: unknown;

here designated as False Bay , South Africa, 40 m.

Pecten maximus sulcicostatus ; Fleming, 1957: 10; Kilburn & Rippey, 1982: 171, pl. 38, fig. 13.

Pecten (Vola) capensis [Gray] G. B. Sowerby 3rd, 1892: 66 (nomen nudum).

Description: Shell height to ca. 100 mm (most adults 60–80 mm), solid, suborbicular, strongly inequivalve, LV flat, RV convex, equilateral, auricles equal, umbonal angle ca. 90–100°. Both valves sculptured with 12–15 radial costae, on LV high and rounded with secondary radial riblets, interstices wider than primary ribs with closely spaced commarginal lamellae, on RV primary ribs subangular also with secondary radial riblets, interstices narrower than primary ribs, with secondary radial riblets and microscopic interstitial commarginal lamellae. Auricles with 4–9 weak radial riblets and fine, closely arranged commarginal lamellae. Hinge line straight. Auricular and disc gape narrow. Byssal fasciole small, byssal notch shallow, no ctenolium. Inner surface with angular ribs near ventral margin and auricular denticles near anterior and posterior margins. Cardinal crura with intermediate teeth. Resilifer elongate-triangular. Colour off-white with pink, salmon or brown markings, RV paler than LV.

Type material: Sowerby (1842: 47) mentioned that the described specimen was in ‘Mr. Norris’s Collection’ (= Thomas Norris of Preston), which was auctioned in 1873 by J. C. Stevens ( Dance 1986: 166, 169, 232). The holotype is now untraceable.

Regional data (all NMSA): SOUTH AFRICA: False Bay: off Buffels Bay, 47 m, slightly muddy sand, live (S8434); off Miller’s Point , 34 m, sand, dead (S7724); between Seal Is. and Simonstown, 30 m, fine sand, dead (S8080); off Partridge Point, 45 m, muddy sand, live (S3730); N of Simonstown, 28 m, sand, shell, dead (S3533); False Bay , 42 m, live (A1919); 2 km NE of Miller’s Point, 34 m, sand, live (S9266). Agulhas Bank: SW of Stilbaai, 60 m, dead (B2465); SE of Mossel Bay, 73 m, live (E5254); off Mossel Bay , 73 m, live (A920); off Bird Is., Algoa Bay , 73–110 m, live (4498); St. Francis Bay , 70 m, fine muddy sand, worm tubes and pennatulids, live (B1622); off East London , 70 m, fine sand, broken shell, dead (B8413); same loc., 70 m, muddy sand, dead (B8332). W Cape Littoral : Struis Bay , Cape Agulhas , beachdrift (E6458); Die Mond , Cape Agulhas , beachdrift (E6615). E Cape Littoral : Jeffreys Bay , beachdrift (B646); Port

22

Figs 20–22. Pecten sulcicostatus Sowerby,1842 : HD 3669 , False Bay, ca. 40 m, pv, 72.9 x 80.9 mm. 20. LV exterior. 21. LV interior. 22. RV exterior .

Elizabeth, beachdrift (2431); Port Elizabeth, beachdrift (4495); Philip’s Reef, Port Elizabeth, 11 m, dead (E7232–3).

Distribution: Endemic to inner continental shelf of South Africa, relatively limited distribution from False Bay to East London.

Habitat: Mainly sublittoral depths, in 30–70 m, free-living on sandy or muddy sand. Shallower water individuals are smaller and often more brightly patterned than those from the continental shelf.

Remarks: Sowerby (1892) used the manuscript name Pecten (Vola) capensis Gray MS , for this species, without any description, but on p. 89 corrected the name to P. sulcicostatus . Fleming (1957), followed by Kilburn & Rippey (1982), treated P. sulcicostatus as a subspecies of Pecten maximus ( Linnaeus, 1758) from the eastern Atlantic. The present species ‘probable arose from a Pliocene or Pleistocene relation of maximus which it closely resembles’ ( Fleming, 1957: 23). Waller (1991: 18, 37) also considered P. sulcicostatus to be morphologically close to P. maximus , but treated it as a full species. No intermediate populations are known from western Africa.

De Villiers (1976) conducted exploratory surveys in False Bay and off Mossel Bay, with a view to establishing whether a local scallop-fishing industry would be viable. Population density off Mossel Bay was inadequate, but False Bay proved promising, although it was concluded that the exploitable area was too small.