Haumea rehderi (Grau, 1960)

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 : 303-304

Haumea rehderi (Grau, 1960)

Figs 87, 100D,F–I,K

Pecten (Aequipecten) aequisulcatus Carpenter. –Dautzenberg & Bavay, 1912: 19 (misidentification).

Chlamys (Argopecten) rehderi Grau, 1960: 15 , pl. 2, figs 1–3.

Argopecten rehderi (Grau) .–Dijkstra, (1983–1994) 1988: 3, figs; Dijkstra, 1989: 2, 12, figs; Dijkstra et al., 1989: 24; Dijkstra et al., 1990: 9–10, figs; Rombouts, 1991: 8.

Chlamys (Argopecten) rehderi Grau. –Dijkstra, 1990a: 11, pl. 2, figs 16–17.

Haumea rehderi (Grau) .–Dijkstra, 1997: 332, figs 39–40; Dijkstra, 1998a: 44, pl. 9, figs 1–4; Raines & Poppe, 2006: 318–319, lower figs; pl. 274, fig. 2; Dijkstra, 2013: 100, pl. 21, figs 5a–b, pl. 25, figs 4a–d; Dijkstra & Maestrati, 2013a: 374.

Type data. Holotype (pr) USNM612201. Type locality: French Polynesia, Society Islands , Leeward Group , Bora Bora Island, Tereia Point, alive, 13–16 fathoms [24–29 m].

Additional material examined. — AUSTRALIA: QUEENSLAND: Torres Strait, Darnley Island, 9°35'S 143°46' E,alive, 55 m (4 pr + 1 v,C.161025);Torres Strait,off Murray Island , 9°56'S 144°04'E,dead, 9–15 m (many v,C.161024);GBR, Low

Isles, 16°23'S 145°34'E,dead(2 v,C.161019);Palm Islands ,18°66.7'S 146°55'E,dead, 27 m (1 v, C.165161;13 v,C.010257);Moreton Bay,off Peel Island, 27°50' S 153°35'E,dead, 9–11 m (1 v, C.165162). — SRI LANKA:off E coast, N of Kokkilai, 9°21' N 80°49'E, dead, 13 m (1 v, C.161031). — THAILAND: Phuket Island, S Ko Lone, alive, 8–10 m (1 pr, ZMA Moll.146094). — INDONESIA: Makassar Strait, alive, 24 m (2 pr, ZMA Moll.142811).—SOCIETY ISLANDS :Tahiti, 17°53.3'S 149°56.7'W,dead, 29 m (2 v, C.161029). — PAPUA NEW GUINEA: New Britain, Rabaul Harbour, Matupi Island, 4°14'S 152°12'E, dead, beach grit (3 v, C.161034); SW of Port Moresby, off W side of Lolorua Island, 9°05'S 147°10.8'E,dead, 13–18 m (4 v,C.161032); Port Moresby,Fairfax Harbour,0.5 ml off Wharf, 9°26'S 147°06'E, alive, 15–18 m (1 pr, C.161033); off Port Moresby, on sheltered NW side of Manubada Island, 9°31'S 147°10'E, dead, 23 m (1 v, C.161032).— NEW CALEDONIA:Nouméa, 22°26.7'S 166°45' E,dead (1 v, C.004333; 1 v,C.161035); Nouméa,alive, 28 m (1 pr, ZMA Moll.142802).— FIJI ISLANDS :Viti Levu, Nadi Bay, 16°57'S 178°47'E,dead, 9–35 m (11 v, C.161027;11 v,C.161028);Viti Levu,Nadi Bay, Newtown Beach, 16°58'S 178°47'E,dead (1 v,C.161026).—SOCIETY ISLANDS :Tahiti, Papeari, alive, intertidal (1 pr, ZMA Moll.144613).

Description. Shell up to c. 10 mm high, most specimens smaller, to 6 mm; moderately inflated, equally convex, subcircular to circular, almost equivalve and equilateral, umbonal angle c. 95°; colour polychromatic, maculated with streaks and/or blotches, right valve paler.

Both valves sculptured with 18–23 narrow, evenly spaced, high, rounded radial plicae bearing weak commarginal lamellae. Each interplicl space equal in width to one plica, bearing prominent commarginal lamellae. Anterior auricle of left valve bearing 5–7 imbricate radial riblets, more prominent than on posterior auricle, weaker and more lamellose on posterior auricle.Anterior auricle of right valve with 4 strongly imbricate riblets. Byssal notch moderately deep, byssal fasciole narrow. Functional ctenolium well-developed, with 5–6 teeth. Interior of valves weakly furrowed, internal rib carinae prominent in narrow zone around ventral margin. Anterior resilial and dorsal teeth prominent, posterior teeth weak.

Habitat. Living in the littoral to sublittoral zones, amongst coral rubble or shell grit on soft bottoms (sand and/or mud).

Distribution. Tropical Indo-West Pacific, from the Philippines southwards to northern Australia, westwards to Sri Lanka, and eastwards into the Pacific to French Polynesia. Not recorded from the western Indian Ocean, northwestern Pacific ( Japan) or the Hawaiian Islands (Raines & Poppe, 2006: 318); Philippines, 2–123 m, dead (Dijkstra, 2013: 101); Papua New Guinea, 30–36 m (Dijkstra, 1998a: 44); Vanuatu, 3–12 m (Dijkstra & Maestrati, 2012: 403–404); Society Islands , 24–29 m, alive, 32–38 m, dead (Dijkstra & Maestrati, 2013a: 374). Maximum depth range of live-taken specimens is from the intertidal zone to 60 m (Dijkstra, 2013: 101). Present material from Australia alive at 55 m.

Remarks. This species is a new record for Australia. The present specimens from Australia are indistinguishable from the type material.

Haumea rehderi can easily be confused with juveniles of the equal-sized, congeneric species Haumea minuta ( Linnaeus, 1758) , more generally known as Haumea inaequivalvis (G. B. Sowerby II, 1842) , occurring in the tropical Indo-West Pacific. The two species can be distinguished by the convexity of the left valve ( Haumea rehderi moderately inflated, H. minuta almost flat), the size of the anterior auricle of the right valve ( H. rehderi has a much larger auricle with a deeper byssal notch), the radial sculpture of the right valve ( H. rehderi has narrower plicae with wider interplical spaces than H. minuta ), and their colour ( H. rehderi is much more polychromatic; most specimens of H. minuta are brown or maculated black on the left valve and white on the right valve).