Delectopecten fosterianus ( Powell, 1933 )

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 : 167-169

Delectopecten fosterianus ( Powell, 1933)

Figs 24, 25B,G

Palliolum fosterianum Powell, 1933: 370 , pl. 40, figs 6, 7. Delectopecten fosterianus (Powell) .–Beu, 1970: 117; Powell,

1979: 379, pl. 73, fig. 3; Dell, 1990: 36; Beu, 1995: 11;

Dijkstra & Marshall, 1997: 89; Beu & Darragh, 2001: 37;

Figure 25. A, C–E, Delectopecten alcocki (Smith) , AM C.157677, pair, FRV Soela stn SO1-84- 12, 200 km NNW of Dampier, WA, 18°53'S 116°10'E, 450 m; rv anterior auricle exterior (A), lv anterior auricle exterior (C), lv exterior (D), rv exterior (E). B, G, Delectopecten fosterianus (Powell) , pair, AM C.449254, off Broken Bay, NSW, 1000 m; rv exterior (B), lv exterior (G). F, H–J, Delectopecten musorstomi Poutiers , pair, AM C.165233, HMAS Kimbla stn 6, Barwon Bank, ESE Noosa Heads, QLD, 26°32'S 153°32'E, 37 m; rv anterior auricle exterior (F), lv anterior auricle exterior (H), rv exterior (I), lv exterior (J). Scale bars represent 1 mm (A, C, F, H), 10 mm (B, G), 3 mm (D, E, I, J).

Raines & Poppe, 2006: 56–57, lower figs; pl. 2, figs 5, 7–8; Dijkstra & Marshall, 2008: 49, figs 40A, B, D–F, 41.

Cyclopecten (Delectopecten) fosterianus (Powell) .– Rombouts, 1991: 77.

Delectopecten fosterianum [sic] (Powell).–Spencer & Willan, 1995: 45; Spencer et al., 2009: 198.

Type data. Holotype (pr) ( Powell, 1933: pl. 40, fig. 6) AIM AK70582, paratype (pr) AIM AK71427 ( Powell, 1933: pl. 40, fig. 7). Type locality: New Zealand, Tasman Sea, 400 ml W of New Plymouth, 39°0'S 168°50'E, byssally attached to deep-sea cable, alive, 1080 m.

Additional material examined. — AUSTRALIA: QUEENSLAND: 24.5 mls E of Lady Musgrave Island, 23°33'S 152°37' E, dead, 339–348 m (3 v, C.338772); NE of Lady Musgrave Island, 23°38' S 152°45'E,alive, 365 m (2 pr + 14 v,C.338773);c. 40 km E of Lady Musgrave Island, 23°44'S 152°49'E,dead, 348–357 m (3 v,C.338771); Capricorn Channel, E of Lady Elliott Island , 24°0' S 153°06'E, dead, 476–531 m (1 v, C.338770) . NEW SOUTH WALES: ENE of Danger Point, 28°01'– 27°58' S 154°0'E, alive, 550 m (2 pr, C.375392); off Tweed Heads, 28°06'S 153°58'E, alive, 412 m (2 pr, C.165240); ENE of Clarence River,29°26'– 29°20'S 153°49'– 153°50'E,alive, 457 m (1 pr, C.375398);off Newcastle, 32°58'S 152°41' E,alive, 951–1150 m (many,C.310673); E of Broken Bay, 33°25'– 33°30'S 152°03'– 152°07' E,dead, 640 m (1 v,C.155812);off Broken Bay,33°31'– 33°28'S 152°11'– 152°13'E,alive, 1040–1110 m (4 pr,C.375388);off Broken Bay, 1000 m (C.449254;illustrated,Fig.14B,G,collected after initial list compiled);off Sydney , 33°36'S 152°09'E, alive, 1097 m (1 v, C.155796; 1 pr, C.375396); off Sydney , 33°36'S 152°09'E, dead, 1097 m (1 v, C.155827); E of Broken Bay, 33°40'– 33°37'S 152°04'– 152°06'E, alive, 988–1016 m (3 pr, C.375391); off Sydney , 33°38'– 33°36'S 152°02'– 152°09'E,alive, 960–988 m (1 pr,C.375395);off Botany Bay , 33°41'S 151°53'E, dead, 366 m (1 v,C.155807); NNE of Sydney, 33°42'S 151°53'– 152°0'E,alive, 406 m (1 pr, C.375399); off Newcastle, 33°59'– 33°54' S 152°42' – 152°44'E, alive, 960–988 m (3 pr, C.375390); NE of Wollongong, 34°18'– 34°24'S 151°26'– 151°21'E, alive, 457–466 m (4 pr, C.338769); off Wollongong , 34°21'– 34°19' S 151°23'– 151°25'E, alive, 439 m (1 pr, C.375397); off Wollongong , 34°22'– 34°19'S 151°27' – 151°25'E, alive, 439–446 m (2 pr, C.375393); off Shoalhaven Bight, 34°50'– 34°54'S 151°15'– 151°17'E, alive, 1130–1180 m (3 pr,C.305399);off Shoalhaven Bight,34°51'– 34°55'S 151°15'– 151°14'E, alive, 1043–1051 m (many,C.155804);off Shoalhaven Bight,34°51'– 34°55'S 151°15'– 151°17'E, alive, 1161–1207 m (1 pr,C.375394); off Shoalhaven Bight,34°53'– 34°56' S 151°15'– 151°13' E, alive, 1097 m (many, C.375387); off Shoalhaven Bight, 34°54' – 34°50'S 151°14'– 151°15' E, alive, 988–1006 m (many, C.155795); off Shoalhaven Bight, 34°54'– 34°50'S 151°14'– 151°15' E, alive, 988–1006 m (1 pr, C.155820); off Nowra, 34°56'– 34°54'S 151°15'– 151°17'E, alive, 1115–1152 m (2 pr, C.375389); E of Brush Island, 35°36'– 35°34'S 150°44' – 150°46'E, alive, 603 m (1 pr, C.110844); E of Merimbula, 36°56'– 36°57'S 150°23' – 150°22.5' E, dead, 1600 m (1 v, C.310675); E of Eden, 36°59'– 36°58'S 150°21'– 150°22.7' E, dead, 716–900 m (2 v, C.310674); 53 km SE of Green Cape, 37°33'– 37°36'S 150°26'– 150°30' E, dead, 860 m (1 v, C.338774) . VICTORIA: S of Point Hicks , 38°19.60'S 149°24.30' E,alive, 930 m (1 pr,VM F.60158) . SOUTH AUSTRALIA: off Beachport, 37°49'S 139.34'E, alive, 1219 m (1 pr, ZMA Moll. 145011); 100 miles SW off Port Lincoln , 35°53'S 134°63'E, dead, 1000 m (2 v, ZMA Moll. 146143) . WESTERN AUSTRALIA: off Albany , 35°23'33"– 35°24'04"S 118°18'32"– 118°18'22"E,dead, 748–776 m (1 v, WAM S77671 ) .— NEW ZEALAND: E North Island,off Castlepoint,alive, 1020–1040 m (1 pr, ZMA Moll. 145009);off Cook Strait , 39°02' S 171°09'E, alive, 492 m (many, AM C.031263); W of New Plymouth, alive, 400 m (3 pr, SAM D13015) . TASMAN SEA: c.400 mls W of New Plymouth , 39°03'S 167°20'E, dead, 1100–1280 m (2 pr, C.160465). New Zealand material also listed by Dijkstra & Marshall (2008, p. 40, fig. 41) .

Description. Shell up to c. 20 mm high, almost circular, hyaline to opaque, whitish, equivalve, equilateral, compressed, both valves almost equally convex, auricles almost equal in size, umbonal angle c. 125°.

Both valves sculptured with delicate antimarginal microsculpture, somewhat coarser marginally, and unevenly spaced commarginal growth lines. Macrosculpture almost absent, with only a few squamous radial ridges anteriorly on right valve and delicate vesicles on commarginal growth lines of some specimens. Auricles of left valve sculptured identically to disc, continuous with disc. Anterior auricle of right valve with 4–6 squamous radial ridges, separated from disc by a suture. Byssal fasciole and notch strongly developed. Functional ctenolium with 3–5 teeth. Resilifer triangular, somewhat oblique.

Dimensions. Illustrated specimen, AM C.449254, NSW, off Broken Bay, 1000 m; rv: H 19.2, L 17.6 mm; lv: H 19.5, L 17.3 mm; D 5.7 mm .

Habitat. Living in the abyssal zone on soft sediment (mud or muddy sand).

Distribution. Previously recorded from New Zealand (Three Kings Rise to the Chatham Rise and Doubtful Sound, SW South Island), the Tasman Sea and the Pacific-Antarctic Ridge (Dijkstra & Marshall, 2008: 40, fig. 41). Now also extended to Australia: eastern and southern Australia, from off Queensland, New South Wales, Victoria, South Australia and southernmost WesternAustralia. Present specimens from Australia taken alive in 365–1207 m.

Remarks. Australian specimens are identical to the type specimens from New Zealand in all morphological characters.

Delectopecten fosterianus differs somewhat from D. alcocki by having an almost smooth surface ( D. alcocki has more strongly developed vesicles or scales on the commarginal growth lines) with more delicate and finer antimarginal microsculpture ( D. alcocki has coarser antimarginal scratches).

Delectopecten fosterianus is a new record for Australia.