Mirapecten boutetorum Dijkstra, 2011
DIJKSTRA, H. H. 2011. A new species of living scallop of the genus Mirapecten (Bivalvia, Pectinidae) from French Polynesia. Basteria 75 (4-6): 63-69, figs. 1-24. [p. 64, figs. 1-12]
2011 Mirapecten bouchetorum Dijkstra, 2011
H. H. Dijkstra, 2011, figures 1-12.
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Gloripallium spiniferum (Sowerby); Dijkstra, 1989: 15, fig., [31], colour photograph;
Rombouts, 1991: pl. 15 fig. 6; Raines & Poppe, 2006: 125 (figured rv), pl. 74 fig. [5] (lv). Not Pecten spiniferus G.B. Sowerby 1st, 1835. Material examined.— French Polynesia: Society Islands, Tahiti, NNWcoast, Arue, ocean-side of barrier reef, 17°30’S 149°31’W, 60 m, alive, dive, 2008, 2 pr (holotype, MNHN 23879, paratype ZMAMoll. 4.11.013); Maupiti, 16°25’S 152°17’W, 437-536 m, dead, dredged, N.O. “Alis”, leg. P. Bouchet et al., 12.x.2009 (TARASOC, stn DW3408), 1 lv (MNHN); Moorea, 17°28’S 149°48’W, 485-560 m, dead, dredged, leg. P. Bouchet et al., 19.x.2009 (TARASOC, stn DW3459), 1 lv (MNHN); Tahiti, 17°47’S 149°21’W, 400-440 m, dead, dredged, leg. P. Bouchet et al., 23.x.2009 (TARASOC, stn DW3487), fragment rv (MNHN); Tahiti, 17°34’S 149°18’W, 350 m, dead, dredged, leg. P. Bouchet et al., 25.x.2009 (TARASOC, stn DW3503), fragment rv (MNHN).
Austral Islands, Rurutu, Avera, 22°29’S 151°21.8’W, 212-450 m, dead, dredged, N.O. “Alis”, leg. IRD-MNHN, 23.xi.2002 (BENTHAUS, stn DW1995), fagment lv (MNHN). Marquesas Islands, Ua Pou, 9°19’S 140°06’W, 200 m, dead, dredged, N.O. “Alis”, leg. BDR, 22.viii.1997 (MUSORSTOM 9, stn DW1146), 1 rv (MNHN); Nuku Hiva, 8°45.6’S 140°03.9’W, 90-120 m, dead, dredged, N.O. “Alis”, leg. P. Bouchet, B. Dayrat & B. Richer de Forges, 26.viii.1997 (MUSORSTO(M 9, stn DR 1182), 2 rv (MNHN); Hiva Oa, 9°52.7’S 139°02.2’W, 60-61 m, dead, dredged, N.O. “Alis”, leg. BDR, 28.viii.1997 (MUSORSTOM 9, stn DW1203), 1 rv (MNHN); Hiva Oa, 9°48.9’S 139°09.5’W, 117 m, dead, dredged, N.O. “Alis”, leg. BDR, 28.viii.1997 (MUSORSTOM 9, stn DW1208), 2 rv (MNHN); Hiva Oa, 9°50.2’S 139°02.5’W, 85 m, dead, dredged, N.O. “Alis”, leg. BDR, 29.viii.1997 (MUSORSTOM 9, stn DW1209), 1 lv (MNHN); Hiva Oa, 9°44.2’S 138°52.5’W, 84-85 m, dead, dredged, N.O. “Alis”, leg. BDR, 30.viii.1997 (MUSORSTOM 9, stn CP 1227), 2 lv (MNHN); Hiva Oa, 9°44.6’S 138°51.5’W, 107-108 m, dead, dredged, N.O. “Alis”, leg. BDR, 30.viii.1997 (MUSORSTOM 9, stn CP 1228), 1 lv (MNHN); Hiva Oa, 9°42’S 139°04’W, 95-305 m, dead, dredged, N.O. “Alis”, leg. BDR, 31.viii.1997 (MUSORSTOM 9, stn CP 1237), 1 lv (MNHN); Fatu Hiva, 10°28’S 138°42.1’W, 1015-1020 m, dead, dredged, N.O. “Alis”, leg. BDR, 01.ix.1997 (MUSORSTOM 9, stn DR 1244), 1 lv (MNHN); Eiao Island, 7°54.6’S 140°40.1’W, 100-120 m, dead, dredged, N.O. “Alis”, leg. BDR, 05.ix.1997 (MUSORSTOM 9, stn DW1274), 7 lv, 5 rv (MNHN), 1 lv (ZMA); Motu One, 7°48’S 140°21’W, 450-455 m, dead, dredged, N.O. “Alis”, leg. BDR, 07.ix.1997 (MUSORSTOM 9, stn DW1281), 10 lv, 5 rv (MNHN), 1 rv (ZMA); Eiao, 7°54’S 140°40’W, 163-245 m, dead, dredged, N.O. “Alis”, leg. BDR, 07.ix.1997 (MUSORSTOM 9, stn DW1287), 1 lv, 3 rv (MNHN); Ua Huka, 8°54.1’S 139°37.8’W, 95-100 m, dead, dredged, N.O. “Alis”, leg. BDR, 08.viii.1997 (MUSORSTOM 9, stn DR 1292), 1 juvenile lv (MNHN); Nuku hiva, 8°49’S 140°17’W, 405-418 m, dead, dredged, N.O. “Alis”, leg. BDR, 09.ix.1997 (MUSORSTOM 9, stn DR 1299), 1 lv (MNHN). Tuamotu Archipelago, Tuamotu, ocean-side of reef, 18°23’S 140°43’W, 14-16 m, dead, leg. M. Marescot, 1985, 1 lv, 1 rv (ZMA); Niau, 16°10’S 146°23’W, 490-560 m, dead, dredged, leg. P. Bouchet et al., 03.x.2009 (TARASOC, stn DW3363), 2 lv, 1 rv (MNHN); Kaukura, 15°41’S 146°54‘W, 390-420 m, dead, dredged, leg. P. Bouchet et al., 05.x.2009 (TARASOC, stn DW3385), 2 lv (MNHN). Description. — Shell up to c. 35 mm high, weakly inflated, valves almost equally convex, strongly inequivalve, nearly equilateral, circular (immature specimens) to slightly elongate (mature shells), auricles unequal in shape and size, umbonal angle c. 100°. Colour pale orange or yellowish with reddish maculations on left valve, right valve more uniform reddish or yellowish, exterior pigmentation not prominent.
Left valve sculptured with 7 regularly arranged radial plicae, which are widely spaced, bearing prominent curved scales on their crests (c. 5 per cm on central part of disc) and one small lateral lira anterior and posterior to each plica; plical interspaces smooth, bearing microscopic, close-set, weakly developed, commarginal lamellae near ventral margin. Auricles also with microscopic, closely spaced commarginal lamellae; scales strongly developed on antero- and postero-dorsal margins. Right valve with 6 regularly arranged radial plicae of dissimilar widths, bearing prominent, closely spaced, imbricated scales on their crests (c. 12 per cm on central part of disc, almost covering radial interstices), with two radial lirae on each side of each plica, bearing more widely set scales; interstices each narrower than one plica, with similar commarginal microsculpture to that of left valve. Auricles with similar commarginal microsculpture to that of left valve, with 3-4 radial ribs on anterior auricle, bearing strongly developed scales on antero- and postero-dorsal margins. Hinge line of left valve straight, of right valve slightly raised; 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 and glossy, with short and weak internal rib, carinate edges on interior ridges corresponding to interspaces between exterior plicae. Dimensions of holotype: H 31.1 mm,W 31.2 mm, C 8.7 mm. Distribution. — Society Islands, Austral Islands, Marquesas Islands and Tuamotu Archipelago (French Polynesia), living amongst coral in shallow water outside reefs. Comparison.— The present species has been identified incorrectly in the past (Dijkstra, 1989: 15; Rombouts, 1991: pl. 15 fig. 6; Raines & Poppe, 2006: 125) as Gloripallium spiniferum (Sowerby 1st, 1835), also known from French Polynesia. Both coral-dwelling species are rare and only very few specimens have been collected alive, probably due to the habitat. Immature specimens could easily be confused with other species, especially single immature right valves. Mirapecten boutetorum spec. nov. differs morphologically from G. spiniferum (see Waller, 1978: 4, pl. 4 figs 58-63) by having 6 radial plicae on both valves (G. spiniferum has 7 on the lv, 8 on the rv), by having more widely spaced scales on the plicae of the left valve (more closely set in G. spiniferum), by lacking macrosculpture on the auricles of the left valve and on the posterior auricle of the right valve (radial macrosculpture is present in G. spiniferum), and by having commarginal microsculpture on the auricles and radial interspaces, at least in the late growth stage (radial microsculpture on the plicae and interspaces in G. spiniferum). Mirapecten boutetorum spec. nov. differs from M. spiceri (Rehder, 1944), known from the Line Islands, by having broader plicae and narrower interspaces (narrower plicae and wider interspaces in M. spiceri), by having strongly developped scales on the plicae (almost lacking or with small, weak nodules in M. spiceri), and by lacking delicate radial sculpture on both valves (present in M. spiceri).
Mirapecten boutetorum spec. nov. differs from M. rastellum (Lamarck, 1819), a well-known Indo-West Pacific species (Raines & Poppe, 2006: 132, pl. 81 figs 1-6, pl. 82 figs 1-6), by having strongly developed and closely arranged scales on the plicae of both valves (almost lacking or weakly developed and more widely spaced on the left valve, and delicate spines on the right valve of M. rastellum), by having more weakly developed commarginal microsculpture (more prominent in M. rastellum), and by lacking secondary radial sculpture in the late growth stage near the ventral margin (present in M. rastellum). Mirapecten yaroni Dijkstra & Knudsen, 1998, known from the Red Sea, is much larger (up to c. 70 mm in height) than the present species (up to c. 35 mm) and has only small scales on the radial plicae of the right valve (strongly developed, large, imbricated lamellae on the present species). Etymology. — Named after Mr Michel Boutet and Mrs Hélène Boutet (Papara, Tahiti, French Polynesia).» HENK H. DIJKSTRA, 2011
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