Cyclopecten kapalae Dijkstra, 1990

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 : 150-151

Cyclopecten kapalae Dijkstra, 1990

Figs 17A–C,E,H, 18

Cyclopecten kapalae Dijkstra, 1990c: 29–32 , figs 1-5; Dijkstra & Marshall, 1997: 87, pl. 6, figs 7–12; Dijkstra & Marshall, 2008: 16, figs 14, 15A–F; Dijkstra & Maestrati, 2008: 97; Spencer et al., 2009: 198; Dijkstra & Maestrati, 2015: 619, figs 7H–J.

Type data. Holotype (pr) AM C.155831.1; 47 paratypes (v) ( AM C.155800, C.155813, C.155814, C.155822, C.155823, C.155831.2, C.155832, C.155837, C.165060). Type locality:

Figure 18. Distribution of Cyclopecten kapalae Dijkstra.

Australia, New South Wales, off Sydney , 33°31'– 33°33'S 152°08'– 152°07'E, alive, 907–914 m (FRV Kapala stn K 80-20-08) .

Additional material examined. — AUSTRALIA: QUEENSLAND: NE of Sandy Cape , 24°25.2'– 24°06'S 153°23.5'– 153°22.4'E, dead, 830 m , 1 v, dead (1 v, C.165445); E of Sandy Cape , 24°43.5' – 24°43.8' S 153°33.4'– 153°33.3'E, dead, 604 m , 1 v, dead (1 v, C.165475; 3 v, C.157675); Frazer Island , off S end, c. 26°01'S 153°50'E, dead, 732 m (1 v, C.165472) . NEW SOUTH WALES: E of Broken Bay , 33°26' S 152°11'E, alive, 822–877 m (1 pr, C.339127; 6 v, C.165470) ; off Sydney , 33°31'– 33°33'S 152°08'– 152°07'E, alive, 907–914 m (1 pr, C.155831; 7 pr + 10 v, C.165060) ; E of Broken Bay , 33°32'S 152°08'E, dead, 914 m (1 v, C.155813) ; E of Broken Bay , 33°32'S 152°08' E, dead, 914 m (1 v, C.155814) ; E of Sydney , 33°33'S 152°05'E,dead, 750 m (3 v,C.155800) ; off Sydney ,33°37'– 33°39'S 152°04'– 152°02'E, alive, 896–924 m (3 pr, C.339126) ; off Broken Bay , 33°38' S 152°06'E, dead, 1000 m (1 v, C.165471) ; NE of Sydney , 33°41' S 151°56'E, dead, 741 m (4 v, C.155837) ; off Broken Bay , 33°44'S 151°57'E, dead, 805 m (many v, C.155832) ; off Sydney , 34°05'S 151°43.6'E, dead, 750 m (many v, C.165469) ; off Nowra , 34°50' S 151°13'E, dead, 550 m (1 v, C.155822) ; off Nowra , 34°50'S 151°13'E, dead, 786–841 m (4 v, C.155823) . VICTORIA: 35 ml S of Tamboon Inlet,Gippsland, 38°02'S 149°08'E,dead, 732 m (1 v, C.337235) ; S of Point Hicks , 38°19.60' S 149°24.30'E,alive, 930 m (4 pr, VM F60158 ) ; S of Point Hicks , 38°21.90' S 149°20' E, alive, 1000 m (4 pr, VM F60159 ) ; S of Point Hicks , 38°25.0'S 149°00.0'E,alive, 1500 m (2 pr,VM F60155 ) ; 76 km S of Point Hicks , 38°29.33'– 38°26.81'S 149°19.98'– 149°20.78'E, alive, 1750–1840 m (4 pr [juv.], VM F60250 ) . TASMANIA: off Freycinet Peninsula , 42°00.20'S 148°37.70'E, alive, 720 m (13 pr, VM F60156 ) ; off Freycinet Peninsula , 42°02.20'S 148°38.70'E, alive, 800 m (7 pr, VM F60157 ) ; 12 ml E of Cape Mistaken , 42°42'10"S 148°17'25"E, dead, 695 m (3 v, C.165473) . SOUTH AUSTRALIA: 160 km SSW of St. Francis Island , dead, 33°65'S 132°13'E, 635 m (3 v, C.165474) . WESTERN AUSTRALIA: off Albany , 35°23'33"– 35°24'04"S 118°18'32"– 118°18'22"E,alive, 748–776 m (1 pr WAM S77660 , 15 v WAM S77666 -9 ) . KERMADEC ISLANDS : Raoul Island , SE of Chanter Island, alive, 512–549 m (NMNZ M225614) . TASMAN SEA: Lord Howe Rise , 27°58.99'S 162°51.55'E, alive, 1250 m (3 pr [lv smooth], C.165410).

Description. Shell small, c. 6 mm in height, slightly higher than wide, sub-circular, inequivalve, left valve somewhat more convex than right, anterior and posterior auricles unequal, umbonal angle about 90°, dirty to milky white, some specimens translucent.

Left valve with reticulate sculpture of weak unevenly spaced radial costae and more prominent commarginal lamellae, interstices microscopically scratched. Radial ribbing commencing 1 mm below umbo; commarginal lamellae commence near umbo. Radial riblets and commarginal lamellae increasing in prominence towards ventral margin. Anterior auricle with coarser commarginal lamellae than posterior one, lacking radial riblets.

Right valve with commarginal lamellae, somewhat higher and coarser at ventral margin than higher up, interstices with microscopic scratches. Anterior and posterior auricles also with commarginal lamellae, slightly more irregular on anterior one. Byssal fasciole small, byssal notch hardly distinguished from outer margin of anterior auricle. Dorsal margin almost straight. Hinge dentition with strong irregular grooves. No internal riblets.

Habitat. Living in the bathyal zone, amongst rubble on soft sediment (sand and mud).

Distribution. Australia (New South Wales), 907–914 m (Dijkstra, 1990c: 29); Kermadec Islands , 512–549 m (Dijkstra & Marshall, 1997); New Zealand: Norfolk Ridge, from N of Norfolk Island (26°15.9'S 167°10.8'E, 750–774 m, 30 v, NMNZ M.172012) to the Chatham Rise, of E central South Island (43°56.8'S 178°01.7'E, 680–736 m, 1 v, NMNZ M.107607), alive in 512–914 m; the Solomon Islands , 611–1598 m, dead (Dijkstra & Maestrati, 2008). Now also from Queensland, Victoria, Tasmania and South Australia and the Tasman Sea. Recently also extended into the Indian Ocean from the Mozambique Channel and southern Madagascar, in 707–708 m (Dijkstra & Maestrati, 2015). Maximum depth range of live-taken specimens is 512–1840 m.

Remarks. A closely similar species from off California ( USA), Cyclopecten bistriatus (Dall, 1916) , differs from C. kapalae in size (height and length of C. bistriatus up to 7 mm) and in having more closely spaced radial riblets on the left valve. Okutani (1962: 18) reported Cyclopecten bistriatus from Sagami Bay, Japan (710–1385 m). However, the reticulate sculpture is finer and weaker than that of both Cyclopecten bistriatus from the eastern Pacific and C. kapalae , and the species reported by Okutani is unnamed.

Cyclopecten thyrideus (Melvill in Melvill & Standen, 1907) from the Arabian Sea, Cyclopecten secundus Finlay, 1927 from New Zealand, Cyclopecten cancellus Dijkstra, 1991 from Indonesia, and Cyclopecten ryukyuensis Hayami & Kase, 1993 from southern Japan all differ from the present species by having more prominent reticulate sculpture and fewer radial costae on the left valve (Dijkstra, 1991: 22).

The present specimens from Western Australia are more weakly sculptured on the left valve than the type material of Cyclopecten kapalae , and some are even almost smooth .