Mirapecten yaroni Dijkstra & Knudsen, 1998
DIJKSTRA, H. H. & J. KNUDSEN. 1998. Some Pectinoidea (Mollusca: Bivalvia: Propeamussiidae, Pectinidae) of the Red Sea. Molluscan Research, 19 (2): 43-104, pls. 1-10. [p. 67, pl. 8, figs. 36-39, text-figs. A-B]
1998 Mirapecten yaroni Dijkstra & Knudsen, 1998
Dijkstra, H. H. & J. Knudsen, 199, plate 8, text-figures A, B.
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«Mirapecten rastellum (Lamarck).- Sharabati, 1984: pI. 44, figs. 1, 1a-g [not Pecten rastellum Lamarck, 1819].
Description: Shell medium of size to approximately 70mm, convex, inequivalve, subequilateral, orbicular (immature) to slightly elongate (mature), auricles inequal in size, urnbonal angle ca. 90º. Left valve sculptured with 6 regularly arranged radial plicae bearing widely spaced, prominent scales, and a small radial rib near the anterior and posterior margins, interstices with microscopic close-set commarginal lamellae, inconspicuous in early growth stages and more prominent in late growth stages near ventral margin, also produced on plicae. Auricles also with microscopic close-set commarginal lamellae and weak radial riblets (one on anterior, 4 on posterior), on antero- and postero-dorsal margins strongly developed scales. Right valve with 5 regularly arranged radial plicae with weaker and more closely arranged scales than on left valve, two radial riblets on each side, interstices broader than lirae, interstitial microsrulpture similar to that on left valve. Auricles with similar commarginal microsculpture to that on left valve, with 4 radial ribs on anterior, 2 on posterior auricle (much weaker), strongly developed scales on antero- and postero-dorsal margins. Hinge line straight, byssal fasciole broad, byssal gape rather shallow, active ctenolium with 6 teeth, auricular crura well developed, resilium triangular elongate, weak auricular ridges near anterior and posterior margins. Inner surface plicated with small radial ridges. Colour pale red with dark red maculations on left valve, much paler on right valve, exterior pigmentation translucent, interior red near ligament and ventral margin, yellowish near auricular margins. Type material: Holotype (H 43.8mm, L 44.3mm, D 12.0mm) ZMUC BIV·323 , 45 paratypes (34 HD, 6 HUJ. 1 NS, 1 ZMTAU, 3 ZMUC). RED SEA: Elat, opposite Old Port, 121 m, 1 v (paratype), 10.ix.1968, MO 28536; Tiran. 68m, 1 spm. (juv.) (paratype), 17.x.1969, NS 16 473; Elat, 3 spms. (paratypes), 1964/65, leg. M. Blom, ZMUC; Elat, 3 v (paratypes), HUJ 35744; Aqaba, 3 v, HUJ 35743; off Elat, 10m, amongst dead coral, live, 1 spm. (paratype), HD 180; off Elat, 6-10m, amongst corals, sand, Live, 3 spms. (paratypes), HD 427; off Elat, 6-10m, attached to corals, live, 3 spms. (paratypes), HD 915; off Elat, 4-15m, attached to corals, sand, live, 5 spms. (paratypes), HD 1583 [figured in Rombouts (1991: pI. 12 fig. 4b)]; off Elat, 6-10m, amongst coral rubble, sand, live, 3 juvenile spms. (paratypes), HD 2857; off Elat, 6-12m, among corals, live, 9 spms. (paratypes), HD 3690; Elat, 2·5m, amongst coral rubble on sand, 10 spms. (paratypes), HD 6745. Type locality: Israel, Gulf of Aqaba, Elat. Distribution: Red Sea. Littoral to sublittoral depths, living on the underside of coral boulders or amongst coral rubble on sandy bottoms. Discussion: Mirapecten yaroni is morphologically closely similar to the lnde-West Pacific species Mirapecten rastellum (Lamarck, 1819) (Dijkstra, 1994: 474). M. yaroni grows larger (up to ca. 70mm high, M. rastellum ca. 45mm). The regularly arranged radial lirae of both species are identical, although the sculpture on the Iirae is different. Strongly developed lamellae are produced in mature specimens of M. yaroni, these are nearly absent or weakly spinose on M. rastellum. Radial riblets present on the auricles of M. yaroni are absent on M. rastellum. The colour of the present species is darker with red and brown spots, whereas M. rastellum is paler with more cream colouration. The bathymetric range of both species is also different: M. yaroni lives in shallow waters, whereas M. rastellum lives in deeper waters. Mirapecten moluccensis Dijkstra, 1988, also known from the Indo-West Pacific, differs from M. yaroni in its nodulose Iirae, more numerous radial riblets on the aurides, and in colour (whitish, with black and reddish linear spots on the left valve). Mirapecten mirificus (Reeve, 1853), also known from the lndo-West Pacific with a distribution similar to that of M. rastellum and a wider distribution than M. moluccensis, is strongly inequivalve and inequilateral, with a nearly flat left valve and irregularly developed radial lirae. Etymology: This species is dedicated to the late Dr. Isaac Yaron (1934-1985), who for many years studied the Red Sea molluscan fauna, and tragically lost his life on April 11th 1985 while diving in the the Gulf of Aqaba. Remarks: Oliver (1992: 77, pI. 12, figs. 6a-b) erroneously described and figured specimens he called M. rastellum from the Gulf of Suez and Jeddah, Red Sea. These are in fact an undescribed Mirapecten species. This species will be discussed elsewhere by Dijkstra & Kilburn (in prep,), Cahill (1979: 36, fig. 6) and Dijkstra (1994: 475) mentioned a new subspecies of M. rastellum from the Red Sea, herein described as M. yaroni. For other remarks on Mirapecten species, see in Dijkstra (1988a, 1991a, 1991b, 1994).» HENK H. DIJKSTRA & JØRGEN KNUDSEN, 1998
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