Delectopecten vitreus ( Gmelin, 1791 )

Dijkstra, H. H. & Kilburn, R. N., 2001, The family Pectinidae in South Africa and Mozambique (Mollusca: Bivalvia: Pectinoidea), African Invertebrates 42, pp. 263-321 : 270-271

Delectopecten vitreus ( Gmelin, 1791)

(Figs 3–4)

Ostrea vitrea Gmelin, 1791: 3328 ; Dillwyn, 1817: 263. Type locality: ‘Oceano septentrionali’ (= ‘ Norwegen, Island und Grönland’ fide Chemnitz, 1784).

Pecten vitreus ; Locard, 1888: 135 (varieties).

Palliolum vitreum ; Barnard, 1962: 254; idem, 1963: 5, 14; idem, 1964: 431 (in part); 1974: 761.

Delectopecten vitreus vitreus ; Nordsieck, 1969: 47, pl. 7, fig. 31.10.

Chlamys (Delectopecten) vitrea ; Tebble, 1976: 64, textfigs 27A–B.

Delectopecten vitreus ; Lucas, 1979: 18, figs; Waller, 1984: 208, figs 3d–e; Wagner (1991): 13, textfig. 5 (synonyms, variation); Poppe & Goto, 1993: 65, pl. 9, fig. 7.

Cyclopecten (Delectopecten) vitreus ; Rombouts, 1991: 78, pl. 27, fig. 3; Lussi, 1995: 2, 12, fig. 20.

Chlamys papyracea Röding, 1798: 164 . Type locality: not given [= ‘Drontheim’ (= Trondheim, Norway) fide Chemnitz, 1784].

Pecten gemmellari filii Biondi, 1859: 118 , pl. 1, fig. 4. Type locality unknown.

Pecten abyssorum [Lovèn] G. O. Sars, 1878: 22, pl. 2, figs 6a–c; Küster & Kobelt, 1888: 241, pl. 63, figs 6– 7. Type locality: Lofoten, 300 fath. (549 m), Sognefjord, 650 fath. (1189 m), Christianifjord (= Oslofjord), 230 fath. (421 m).

Chlamys chaperi Dautzenberg & H. Fischer, 1897: 190 , pl. 5, figs 5–8. Type locality: Azores, 38°31'N, 26°09'30'' W, 845 m; 39°11'N, 32°44' 30'W, 1600 m.

Description: Shell to ca. 20 mm high, suborbicular (usually higher than wide), RV slightly more convex than LV, inequilateral, auricles unequal (posterior larger than anterior), umbonal angle ca. 80–90°. Both valves sculptured with commarginally crenated growth lines with vesicular tubercles, except on anterior auricle of RV, which has 5–6 lamellose radial riblets. Posterior auricles weakly defined. Microsculpture of antimarginal striae throughout ontogeny, sometimes only in early growth stages. Postero-dorsal margin spiny or tuberculated. Hinge line straight. Byssal fasciole broad, byssal 3 4

Figs 3–4. Delectopecten vitreus ( Gmelin, 1791) : NMSA K3886, off Walvis Bay, Namibia, ca. 200 m, pv, 13.9 x 13.9 mm. 3. LV exterior. 4. RV exterior.

notch moderately deep. Active ctenolium with 3–6 teeth on suture. Auricular crura weak. Resilifer triangularly oblique. Colour dull translucent white or hyaline.

Type material: O. vitrea : 10 syntypes ZMUC (not registered); seen by HD. C. papyracea : syntype ZMUC (not registered), seen by HD. P. abyssorum : syntypes ZMUO (not traced). P. gemmellari filii : not traced. C. chaperi : syntypes MOM 28.0148–9, seen by HD.

Regional data (both NMSA): SOUTH AFRICA: Atlantic Cape: off Saldanha Bay , 308– 310 m, green mud (V270). NAMIBIA: off Walvis Bay, ca. 200 m, ex pisce (K3886: S. Whatmough) .

Distribution: Arctic Ocean, NW and E Atlantic to off west coast of South Africa.

Habitat: Sublittoral to abyssal depths, usually byssally attached to rocks, stones, gorgonians or hydroids on a substratum of soft sediments (mud or muddy sand).

Remarks: Some authors (e.g. Grau 1959; Rombouts 1991; Wagner 1991) include Pseudamussium gelatinosum Rochebrune & Mabille, 1889 , from southern Argentina and southern Chile, in the synonymy of D. vitreus . Morphologically D. gelatinosus is more similar to D. fosterianum ( Powell, 1933) of S Australia, New Zealand and the Pacific-Antarctic Ridge ( Dell 1990: 36). Although Barnard (1964: 431) synonymised Pecten alcocki E. A. Smith, 1904 , of the Indo-West Pacific with D. vitreus, Knudsen (1967: 283) clearly differentiated the two species.