Laevichlamys weberi (Bavay, 1904)

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 291-293

Laevichlamys weberi (Bavay, 1904)

(Figs 27–28)

Chlamys weberi Bavay, 1904: 202 , pl. 6, figs 5–6; Lussi, 1995: 2, fig. 23; Steyn & Lussi, 1998: 212, fig.

859. Type locality: ‘Cost. Africae occidentalis’ (herein restricted to Durban , KwaZulu-Natal,

South Africa). Chlamys (Chlamys) weberi ; Wagner, 1983: 145–148, figs 9–11. Chlamys natalensis E.A. Smith, 1906: 60 , pl. 8, figs 7–7a, 8–8a; idem, 1910: 213; Barnard, 1964: 426, fig.

14d; idem, 1974: 761 (posthumous); Boshoff, 1965: 135, pl. 14, fig. 6; Kilburn & Rippey, 1982:

171. Type locality: Durban. Pecten natalensis ; Bartsch, 1915: 186; Turton, 1932: 222. Chlamys (Chlamys) natalensis ; Wagner, 1983: 145–146, 148, fig. 1 (holotype refigured).

Description: Shell height to ca. 30 mm (average 15–20 mm), rather compressed, RV slightly more convex than left, elongate, equilateral to somewhat inequilateral, auricles unequal, umbonal angle ca. 85–90°. Both valves sculptured with numerous, regularly closely spaced, rounded scabrous radial costae (ca. 35–45), strongly lamellose near ventral margin, interior regularly plicated. Microsculpture of antimarginal striae in preradial stage, followed by an abrupt change to shagreened or reticulate microsculpture in submarginal region, usually transforming again into antimarginal microsculpture near ventral margin, sometimes lacking. Intercostal commarginal lamellated microsculpture absent. Anterior auricles much larger than posterior ones, with ca. 10 squamose radial riblets and interstitial shagreened microsculpture (absent in RV), on posterior auricles weakly developed (ca. 5). Hinge line straight, near postero-dorsal margin somewhat sloping. Byssal fasciole rather broad, byssal notch deep, active ctenolium with 5–7 teeth on suture.Auricular crura well developed. Resilium triangularly elongate. Colour variable, greyish, creamy, pinkish, purplish-brown, faintly mottled, sometimes uniform yellow or orange.

Type material: C. weberi : holotype KBIN coll. Dautzenberg, I.G. no. 10.591, paratype ZMA Moll. 304.002. C. natalensis : holotype BMNH 1906.6 . 23.32. Seen by HD .

27 28

Figs 27–28. Laevichlamys weberi (Bavay, 1904) : NMSA 2423, Durban, Natal, pv, 24.1 x 21.0 mm. 27. LV exterior. 28. RV exterior.

Regional data (all NMSA, unless otherwise stated): MOZAMBIQUE: Baia dos Cocos, dead (F9683: A. Jenner); Bay of Maputo, Inhaca Island , dead (4486: P. H. Boshoff); Bay of Maputo, Cabo de Santa Maria, dead (9160: RK) . SOUTH AFRICA: Zululand: off Hully Point , 50 m, fine sand, dead (D7561: NMDP) ; SE of Port Durnford , 165 m, mud with sand, dead (E8721: NMDP) ; Sodwana Bay, Two Mile Reef, 10–15 m, stone washings, live (E787: D. Herbert & R. Broker). Natal: off Durban Bluff, 20–22 m, sand, dead (B5458: R. N. Kilburn & R. Fregona); same loc., 18–20 m, dead (B8984: R. N. Kilburn & D. Herbert); Durban, dead (2422, 2424, 2421: H. C. Burnup); same loc., dead (2423: H. C. Burnup); Durban, South Beach (B4893: R. N. Kilburn & R. Fregona); off Umlaas Canal, 200 m, coarse sand, dead (D881: NMDP) ; same loc., 50 m, fine sand, dead (D998: NMDP) ; off Amanzimtoti , 260–270 m, medium sand, dead (D1195: NMDP) ; Kelso, dead (A2221: RK) ; Port Shepstone , dead (D4485: H. C. Burnup); Melville, dead (5008: RK) . Transkei: Mzamba , beachdrift (D2761: R. N. Kilburn & D. Herbert); between Mzamba and Mtentu Rivers, dead (E6023: NMDP) ; off Port Grosvenor , 105 m, flat rocks, pebbles, mud, dead (C624: NMDP) ; same loc., 100–110 m, pebbles, some sand, dead (C605: NMDP) ; same loc., 120–128 m, coarse sand, some mud, solitary coral, shells, dead (C1154: NMDP) ; same loc., 120–128 m, coarse sand, some mud, solitary coral, shells, dead (C1155: NMDP) ; Mbotyi, beach drift (C8247: RK, D. Herbert); off Mgazi River , 100 m, coarse sand and rubble, dead (C2814: NMDP) ; off Whale Rock , 20–26 m, sand, gorgonians, dead (C3264) .

Extralimital material: KENYA: near Mombasa, amongst coral rubble on exposed reef, live ( HD6569 ) .

Distribution: Kenya and Malagasy Republic to eastern Cape, South Africa (Port Alfred fide Turton, 1932),

Habitat: Littoral to bathyal depths (living from intertidal region to ca. 24 m; dead shells down to 200 m (see note below).

Remarks: Wagner (1983) erroneously reported that the holotype of C. weberi had been deposited in the ZMA. The holotype was originally in Bavay’s personal collection (Bavay, 1904: 203), which after his death was auctioned by Gérets, a Paris dealer, and purchased by Dautzenberg. This specimen is now in the KBIN. However, Bavay mentioned a second individual, sent to him for identification by Weber; which is the one (with paratype status) now in the wet collection of the ZMA.

The microsculpture in Laevichlamys weberi changes with growth. Thus in early ontogeny, antimarginal striae are well developed and become transformed into intercostal shagreened microsculpture. However, the typical chlamiid, intercostal, commarginally lamellated microsculpture is lacking. In late ontogeny the shagreen microsculpture becomes more or less compressed into a reticulated microsculpture, sometimes abruptly transformed into intercostal antimarginal striae near the ventral margin, or else absent. The shagreen microsculpture of L. weberi is more prominent than in other species of Laevichlamys .

The southernmost samples dredged during the NMDP [off Mbashe River, 295–300 m (C8983) and off Kei R., 222 m (C4072)] represent old shells evidently originating in shell deposits from an early regression. The same may apply to most of the deeper water samples.