Mimachlamys cloacata (Reeve, 1853)

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 280-282

Mimachlamys cloacata (Reeve, 1853)

Figs 86H,J, 88B–D,F, 89

Pecten rugosus G. B. Sowerby II, 1842: 66 , pl. 19, fig. 226 (junior primary homonym of Pecten rugosus Lamarck, 1819 ).

Pecten cloacatus Reeve, 1853 : sp. 166, pl. 34, fig. 166.

Pecten valdecostatus Melvill, 1888: 281 , pl. 2, fig. 10.

Pecten (Chlamys) pelseneeri Dautzenberg & Bavay, 1912: 8 (replacement name for P. rugosus Sowerby, 1842 ).

Mimachlamys curtisiana Iredale, 1939: 351 , pl. 5, figs 19–19a.

Chlamys asperulata pelseneeri (Dautzenberg & Bavay) .– Kira, 1962: 137, pl. 49, fig. 11.

Chlamys asperulata (A.Adams & Reeve) .–Abbott & Dance, 1982: 313, fig. (misidentification).

Chlamys (Mimachlamys) valdecostatus [sic] (Melvill).– Wang, 1983c: 50, pl. 1, fig. 7.

Chlamys (Mimachlamys) asperulata (A.Adams & Reeve) .– Wang, 1983c: 51, pl. 1, fig. 3.

Chlamys (Chlamys) cloacata (Reeve) .–Dijkstra, 1990a: 10; Rombouts, 1991: 10, pl. 4, fig. 4; Higo et al., 1999: 442.

Chlamys cloacata (Reeve) .–Dijkstra, 1991: 29; Wang, 2002: 179, pl. 5, fig. 6; Dharma, 2005: 248, pl. 99, figs 6a–m.

Chlamys (Chlamys) curtisiana (Iredale) .–Lamprell & Whitehead, 1992: [20], pl. 8, fig. 42.

Chlamys pelseneeri (Dautzenberg & Bavay) .–Bernard et al., 1993: 49.

Chlamys valdecostata (Melvill) .–Bernard et al., 1993: 49.

Mimachlamys cloacata (Reeve) .–Dijkstra, 1998a: 41, pl. 8, figs 4–5; Dijkstra, 1998b: 254; Raines & Poppe, 2006: 268–269, upper figs; pl. 214, figs 3, 5–6, 8–9; Huber, 2010: 210; Raines, 2010: 638, pl. 1010, figs 5–8; Dijkstra, 2013: 89, pl. 23, figs 2a–d, pl. 31, figs 4a–b.

Mimachlamys asperulata (A. Adams & Reeve) .–Hayami, 2000: 901, pl. 448, fig. 22.

Mimachlamys gloriosa (Reeve) .–Xu & Zhang, 2008: 83, fig. 233 (misidentification).

Type data. Pecten rugosus Sowerby : two possible syntypes NHMUK1996438 . Type locality: Philippine Islands , Bureas Island .

Pecten cloacatus Reeve : lectotype (pr) NHMUK1995 . 158.1, paralectotype (pr) NHMUK1995158.2 , designated by Dijkstra (1998a: 41). Type locality: Philippine Islands .

Pecten valdecostatus Melvill : holotype (pr) NMW1955 . 158.5. Type locality: Hong Kong.

Mimachlamys curtisiana Iredale : holotype (pr) AM C.089670 (Fig. 88D, F). Type locality: Australia, QLD, Gladstone , Port Curtis.

Additional material examined. — AUSTRALIA: QUEENSLAND: Gulf of Carpentaria,28 ml S of Sweers Island, 17°06'S 139°37'E,dead (1 v,C.375622);Cape York, Peak Point, 10°43'S 142°26'E, alive, 5–11 m (1 pr, C.375625; 2 pr, C.375745); Cape York, Somerset, Stover Bay, 10°44.1'S 141°35' E, alive (1 pr, C.376074); Cape York Peninsula,Albany Passage, 10°45'S 142°37'E, dead, 7–26 m (many v, C.375623; 19 v,C.375746);Cooktown, 15°28'S 145°15'E,alive (1 pr,C.375624);GBR, Low Isles, 16°23'S 145°34'E, dead (1 v, C.375740); Cairns Harbour, 16°53'S 145°48'E, dead (2 v, C.107992;1 v, C.375744); Kurramine Beach, S of Innisfail, 17°47'S 146°06'E,dead (1 v,C.375626);Cardwell, 18°16'S 146°01'E,dead (8 v,C.375627);off Great Palm Island, 18°43'S 146°37' E, alive (2 pr, C.303769); Dingo Beach, Cape Gloucester, 20°05'S 148°30.5'E, dead (1 v, C.375759); Whitsunday Passage, 20°13.5'S 148°47.5'E, dead, 24 m (4 v, C.375629);Whitsunday Group, Hamilton Island, 20°22'S 148°57' E, dead (1 pr,C.375758);Whitsunday Group,Lindaman Island,dead(1 v,C.380453);Whitsunday Passage, Lindeman Island, 20°27'S 149°02' E, dead (many v, C.375631; 1 v, C.375756; 1 v, C.375757); Whitsunday Group, off Shaw Island, dead, 37 m (3 v, C.132023); Repulse Bay, Conway Beach, 20°28.5'S 148°45'E, dead (2 v, C.103808); off Shaw Island, N of Mackay, 20°29'S 149°05'E,dead, 37 m (many v,C.375628);Seaforth, N of Mackay, 20°54'S 148°58'E,dead (1 v, C.132020; 7 v,C.375630);E of Sarina, 21°27.5'S 150°08'E, dead, 42 m (3 v, C.375741); E of Sarina, 21°28'S 150°08.5'E, dead, 40 m (2 v, C.375742); off Broad Sound, 22°06' S 150°49'E, dead, 53 m (1 v, C.375743); Broad Sound,Clairview, 22°11'S 149°34'E,alive (1 pr,C.074842);Pearl Bay, E of Shoalwater Bay, 22°25' S 150°44' E,alive (2 v,C.070504);SE of Swain Reefs, 22°31.4'S 152°32.6'E, dead, 100 m (1 v, C.375760); Keppel Bay, North Keppel Island, 23°04' S 150°54'E, dead (1 v, C.375632); Keppel Bay, Yeppoon, 23°08' S 150°45'E, alive (1 pr, C.132019); Keppel Bay, Emu Park, 23°15'S 150°49'E, dead (3 v, C.132018); Keppel Bay, 23°25'S 150°55' E,alive (13 v,C.103819);Capricorn Group,Mashead Island, 23°32'S 151°45'E, dead, 31–37 m (2 v, C.021215); Port Curtis, off Gatcombe Head, 23°54'S 151°22'E, alive, 13–18 m (9 v, C.018678); Port Curtis, 23°55'S 151°23'E, alive, 16–22 m, (3 v, C.012051; 1 pr [holotype Mimachlamys curtisiana ], C.089670; 3 pr, C.097539; 1 pr, C.132017; 5 v, C.375633); Port Curtis, Gladstone, 23°54' S 151°22'E, alive, 13–18 m (many, C.375734); Port Curtis, Quoin Island, 23°49'S 151°17'E, dead, 2–5.5 m (13 v, C.375736);Port Curtis,Facing Island, 23°49'S 151°22'E,alive (many v, C.375735;1 pr + 1 v, C.375737); Port Curtis,South Channel, Jenny Lind Buoy, 23°56.5' S 151°30.5'E, alive (2 pr + 1 v, C.036984); Tannum Sands, S of Gladstone, 23°57'S 151°22'E, dead (5 v, C.375739); Hervey Bay, off Picnic Point, 25°06' S 152°49'E, alive, 9–12 m (2 pr, C.103803); Hervey Bay, S of Woody Island, 25°18.5' S 152°56'E, alive, 9 m (2 pr, C.097433); Hervey Bay, Mary River mouth,North Head, 25°25.6' S 152°55'E, alive (1 pr + 1 v,C.375738);Moreton Bay, Redcliffe Peninsula,Clontarf,Woody Point, 27°16'S 153°06'E, dead (1 v,C.103823). WESTERN AUSTRALIA: Exmouth,Bundegi Reef, 21°51'S 114°11'E, alive, 6 m (1 pr, C.160987). NORTHERN TERRITORY: Darwin, 32 km off Point Charles, 12°10'S 130°22'E, dead, 27–37 m (19 v, C.375761); Melville Island, near Garden Point, 11°24.5'S 130°24.7'E, dead (1 v, C.375621); Darwin, Sandbar No.2, 12°24'S 130°44' E,dead (9 v,C.375599); Darwin, West Point, 12°26.5' S 130°46'E,alive (1 pr,C.376075);Port Darwin entrance, 12°25'S 130°46.5'E,dead, 36 m (1 pr, C.375768); Darwin, Sandbar, 12°26'S 130°48'E, dead (1 pr, C.375769); Darwin Harbour,Weed Point,alive (1 pr, WAM 448);Darwin, 36 km off Point Charles, 12°16.7' S 130°36.7'E, dead, 27–37 m (many v, C.165427); Darwin, off Point Charles, 12°16.7'S 130°36.7'E, dead, 27–37 m (17 v, C.165429); Darwin, Fannie Bay, W of East Point, 11°24.5'S 130°48.5'E, alive, 8–10 m (1 pr,C.376073);Darwin, 12°27'S 130°50'E,dead (1 v, C.131216;1 v, C.375619;3 v,C.375764);Darwin,Dudley Point, 12°25'S 130°49'E, alive (1 pr,C.375762);Port Darwin, 12°28'S 130°50'E,alive, 15 m (3 pr, C.057357;1 v, C.375620;1 pr, C.375751); Darwin,Waigait, 11°28'S 130°50'E,alive (1 pr, C.165225); Darwin,Waigait, 11°28'S 130°50'E (1 pr,alive,C.072324;6 v, dead,C.375765);Darwin, Casuarina Beach , 12°21'S 130°52'E, dead (1 v,C.375766);Arafura Sea, c. 110 ml N of Melville Island, 9°34'S 131°22'E, dead, 135 m (2 v, C.160976); 100 km NE of Melville Island, 10°22.5'S 131°37'E, dead, 71 m (1 v, C.160975); Arafura Sea, c. 95 ml N of Cobourg Peninsula, 9°45'S 132°04'E,dead, 108 m (1 v, C.160978);Arafura Sea, c. 100 ml N of Croker Island, 9°30'S 132°34'E, dead, 124 m (2 v, C.160971);Arafura Sea, c. 45 ml N of Croker Island, 10°17'S 132°38'E, dead, 65 m (7 v, C.160977); 180 km N of Croker Island, 9°24'S 133°02' E,dead, 125 m (2 v,C.160972); 68 km NE of Croker Island, 10°39'S 133°05' E, dead, 62 m (1 v, C.160973); 91 km N of Goulburn Island, 10°42'S 133°36'E,alive, 58 m (2 pr + 1 v,C.160974);Arafura Sea, c.210 ml NE of Croker Island, 8°18'S 133°58'E, dead, 132 m (2 v, C.160970); Arafura Sea, c. 250 ml NE of Croker Island, 8°09'S 134°50'E, dead, 115 m (4 v, C.375750). — JAPAN:Shikoku Island, Iyo, 33°43'N 132°42'E,alive(2 pr,C.045722).— CHINA:off Hong Kong,21°17.4' – 21°20.4' S 114°48.1'– 114°52.8'E, dead, 87–97 m (1 v, C.143458); Hong Kong, Mirs Bay (Tai Pang Wang), SE of Ping Chau Island, 22°33' N 114°24'E, dead, 0–8 m (5 v,C.375603). TAIWAN: NE of Taiwan, alive, 40–50 m (3 pr, ZMA Moll.143127). — PHILIPPINE ISLANDS : Bohol,Balicasag Island,alive, 130–140 m (1 pr, ZMA Moll.144227); Davao, Talikud,alive, 80–200 m (3 pr, ZMA Moll.144236);SuluArchipelago,Jolo Island,alive, 45 m (2 pr, ZMA Moll.143724). SINGAPORE:Pulau Sudong, Selat Sulong & vicinity, 1°12'N 103°44'E, dead (6 v,C.127293); Sentosa Island, W end of Silosa Beach, 1°15'S 103°48'E, dead, beach (1 v, C.375601). — VIETNAM: Nha Trang, Hon Mieu, alive, 4–5 m (1 pr, ZMA Moll.139639). — THAILAND: Gulf of Siam, Samui Island, alive, 5–20 m (20 pr, ZMA Moll.145792); Andaman Sea, Phuket Island, alive, 10–35 m (2 pr, ZMA Moll.142130).— INDONESIA:E Sumatra, near Singkep Island,alive, 50–60 m (4 pr, ZMA Moll.143709); Java Sea, alive, 30–34 m (3 pr, ZMA Moll.142186); Kei Islands ,alive, 18 m (1 pr, ZMA Moll.142184).— PAPUA NEW GUINEA: New Britain, Rabaul, 4°12'S 152°11' E, dead (2 v, C.375602); Gulf of Papua, off Yule Island, 8°50'S 146°32'E,alive, 37 m (1 pr,C.375747); Gulf of Papua,1.5 ml SW of Yule Island, 8°51'S 146°30'E, dead, 22–23 m (3 v, C.375749); off Port Moresby, Manubada Island, off W end, 9°31'S 147°10'E, dead, 18–22 m (1 v, C.375600). CORAL SEA: Marion Reef, 19°07'S 152°23'E, dead (1 pr,C.357993).— NEW CALEDONIA:Bay of Prony, Ouen Island, alive, 44–55 m (1 pr, ZMA Moll.142270).

Description. Shell up to 44 mm high ( Raines, 2010), rather solid, moderately well inflated, almost equally convex, triangularly ovate, equivalve, slightly inequilateral, anterior auricles much larger and longer than posterior ones, umbonal angle c. 75–85°; colour polychromatic.

Both valves sculptured with c. 16–18 evenly spaced, narrowly rounded, lamellate, primary radial plicae, in some specimens flanked by secondary riblets in late growth stage. Commarginal lamellae on plicae of most specimens, widely to more closely spaced, present in radial interspaces of some specimens. Intercostal “herringbone” microsculpture on disc, in late growth stage transformed into antimarginal microsculpture. Anterior auricle of left valve with 6–7 prominent radial costae with closely spaced intercostal commarginal lamellae; posterior auricle with c. 5 weak, squamous radial riblets and intercostal granular or antimarginal microsculpture, or with closely spaced irregular commarginal lamellae.Anterior auricle of right valve with c. 5 prominent squamous radial costae, weaker and narrower on posterior auricle. Byssal notch deep, byssal fasciole rather broad. Functional ctenolium well developed, with c. 5–7 teeth. Internal rib carinae prominent, short, in narrow zone around ventral margin. Resilial and dorsal teeth prominent.

Dimensions. Illustrated specimen: QLD, Hervey Bay, off Picnic Point , 9–12 m ( AM C.103803): rv and lv both H 26.8, L 23.7 mm; D 11.4 mm. Iredale (1939: 351) stated the dimensions of the holotype of Mimachlamys curtisiana as H 28, L 25 mm .

Habitat. Living in the littoral zone to on the continental shelf, most specimens byssally attached to undersides of rocks or coral boulders, or amongst coral rubble on sandy bottoms; often encrusted with sponge.

Distribution. Tropical Indo-West Pacific, from southern Japan, southwards to northern Australia, westwards into the Indian Ocean to the Gulf of Bengal, and eastwards to New Caledonia (Raines & Poppe, 2006: 270); Japan to the Andaman Islands , 1–58 m (Huber, 2010: 210); Philippines, 20–111 m ( Raines, 2010: 638; Dijkstra, 2013: 92); Indonesia, 58 m (Dijkstra, 1991: 29); Papua New Guinea, 20–30 m, dead (Dijkstra, 1998a: 41). Maximum depth range of live-taken specimens is 1– 140 m. Present specimens from Australia alive at 5– 58 m.

Remarks. The present specimens ( curtisiana morph) from Australia resemble the type material of Mimachlamys cloacata , but differ somewhat in the number of radial plicae (c. 20, typically 16–18) and secondary radial sculpture (present in the late growth stage of most specimens, typically almost lacking). Other characters are identical, and small specimens are indistinguishable from equal-sized specimens of Mimachlamys cloacata from the Philippine Islands .

Mimachlamys cloacata has a polymorphic microsculpture (see description) and also varies in convexity (moderately to rather strongly inflated) and macrosculpture (prominence of the radial sculpture and development of the lamellae).