Decatopecten strangei ( Reeve, 1852 )

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 : 187-189

Decatopecten strangei ( Reeve, 1852)

Figs 32G,I, 34G–H, 37

Pecten strangei Reeve, 1852 : sp. 22, pl. 4, fig. 22; Küster & Kobelt, 1888: 169, pl. 47, fig. 2.

Pecten strangei var. Reeve, 1853: sp. 148, pl. 32, fig. 148.

Decatopecten strangei (Reeve) .– Iredale, 1936: 269, pl. 20, fig. 3; Iredale, 1939: 361; Allan, 1950: 280, fig. 6; Iredale & McMichael, 1962: 11; Slack-Smith, 1990: 134, 147; Lamprell & Whitehead, 1992: [28], pl. 12, fig. 68; Slack- Smith & Bryce, 2004: 237; Taylor & Glover, 2004: 262; Huber, 2010: 198.

Decatopecten edentiplica [sic] Iredale, 1939: 362.

Decadopecten (Decadopecten) strangei (Reeve) .– Rombouts, 1991: 37, pl. 13, figs 9–9a.

Type data. Pecten strangei Reeve : three syntypes NHMUK 1950.11.14.74-76. Type locality: Moreton Bay , Australia.

[ Decatopecten edentiplica Iredale : holotype (1 pr, immature) AM (not registered). Type locality: GBR, Low Isles, 9–12 fathoms [16–22 m], mud & muddy sand, leg. Dr C. M. Yonge ( Iredale, 1939: 220–221)].

Comments on type data. Iredale (1939: 362) did not treat “ Decatopecten edentiplica ” clearly according to the ICZN Code. He did not introduce a new species name, but only a new epithet “Edentiplica” (the initial capital is presumably a typographical error). It is possible that he only wanted to distinguish the “immature” specimen from the Low Isles, the only specimen mentioned under this name, from D. plica and not to introduce a distinct new species.The immature holotype is identical to young specimens of Decatopecten strangei .

Additional material examined. — AUSTRALIA: QUEENSLAND: Torres Strait, 10°22.14'S 141°42.42'E,dead, 16 m (2 pr,C.164910);Cape York Peninsula, 10°41.3'S 142°31.75'E, alive (1 pr, C.097567); Cape York Peninsula,Albany Passage, 10°45'S 142°37' E, dead, 7–26 m (2 v, C.036134); GBR, off Cape Grenville, Sunday Island, 11°56'S 143°12'E, dead (1 v, C.075231); Gulf of Carpentaria, 10 ml SW of Mapoon, 12°05'S 141°40'E, dead, 18 m (8 v, C.014080); Gulf of Carpentaria, 12°38'S 141°0'E, dead, 59 m (1 pr, WAM); Gulf of Carpentaria, 16°27.15'S 140°01.20' E, dead, 29 m (1 v, WAM); GBR, 0.5 ml NW of Howick Isle, 14°29'S 144°57'E, dead, 18 m (1 v, C.075243); GBR, 0.5 ml N of Eagle Isle, 14°41'S 145°22'E, dead, 18 m (1 v, C.119738);Gulf of Carpentaria,W of Edward River, 14°46'S 141°20.7' E,dead, 18 m (1 v, C.372104);GBR,Decapolis Reef,off Cape Flattery, 14°50'S 145°17'E,dead, 12–14 m (1 v,C.372111);GBR,0.5ml W of Two Isles, 15°01'S 145°26'E,dead, 30 m (1 v,C.119737); Cairns Reef lagoon & between Cairns Reef & Hope Island, 15°42'S 145°30'E,dead, 9–18 m (8 v, C.027534); between Cairns & Endeavour Reefs, 15°45'S 145°35'E, dead, 37 m (2 v, C.044615); E Gulf of Carpentaria, W of Nassau River, 15°51'S 140°54.2'E, alive, 22 m (1 pr, C.372156);E Gulf of Carpentaria, W of Nassau River, 15°53.5' S 140°42'E, alive, 25.6 m (2 pr + 7 v,C.111135); Gulf of Carpentaria,SW of Nassau River, 16°06'S 141°01.8'E, dead, 14.6 m (1 v, C.107314); Gulf of Carpentaria, SW of Nassau River, 16°08.5'S 140°52.6'E, dead, 18 m (1 v,C.107300); GBR, Low Isles, 16°23'S 145°34'E, dead, 16–22 m (5 v, C.093401); off Cairns, 16°51.6'– 16°51'S 146°01.2'– 146°0.4'E, dead, 33–35 m (2 v, C.372113; 25 v, C.372124); off Cairns,16°52'– 16°53'S 146°0.6'E, dead, 37–38 m (1 v, C.372125);Gulf of Carpentaria,28 ml S of Sweers Island, 17°06'S 139°37'E, dead (1 v, C.372108); Horseshoe Bay, Magnetic Island, 17°07'S 146°51'E, dead, 6–9 m (1 v,C.372126);Forrest Beach,S of Lucinda, 18°43'S 146°18' E, dead (8 v, C.372155);off Townsville, 19°06'S 146°48'E, dead, 8–9.5 m (1 v,C.372128);Magnetic Island, 19°08'S 146°50'E, dead (1 v, C.075240); S of Townsville, 19°17'S 147°32'E, dead, 24 m (3 v, C.123883); between Bowen & Townsville, 19°30'S 148°0'E, alive, 37 m (1 pr, C.097568); off Cape Upstart, 19°42'S 147°45'E, dead, 36 m (1 pr, C.097571); off Bowen, 19°44' S 148°14'E, dead, 40 m (2 v, C.119548); E of Bowen, 19°45.7'S 148°19'E,dead, 46 m (1 v,C.372136);Gloucester Island, 20°01'S 148°27'E,dead (1 pr, Figure 36. A, C, Decatopecten radula (Linnaeus) , pair, AM C.049664, Montebello Islands , WA, 20°26'S 115°32'E; lv exterior (A), rv exterior (C). B, E, Glorichlamys quadrilirata (Lischke) , separate valves,AM C.165151, 80 nautical miles NNE of Port Hedland,WA, 19°03.6'– 19°03.4'S 119°03.4'– 119°03.5'E, 82 m; rv exterior (B), lv exterior (E). D, F, Excellichlamys spectabilis (Reeve) , pair, WAM S43979 , MV Davena, N end of Flying Foam Passage, Dampier Archipelago, WA; lv exterior (D), rv exterior (F). G–I, Glorichlamys elegantissima (Deshayes) , pair, NTM P054288, off NE side of Flinders Reef, N of Cape Moreton, Moreton Island, QLD, 27°01'S 153°43'E, 12–15 m; lv interior (G), lv exterior (H), rv exterior (I). Scale bars represent 50 mm (A, C), 10 mm (B, E, G–I), 20 mm (D, F).

C.067817); W of Hayman Island , 20°03'S 148°50' E,dead, 33 m (4 v,C.120138) ; Bowen, 20°04' S 148°22'E,dead(1 pr,C.103806); Whitsunday Passage, Lindeman Island, 20°27'S 149°02'E, dead (21 v, C.058939); off Shaw Island , N of Mackay , 20°29' S 149°0.5'E, dead, 37 m (6 v, C.372138) ; Whitsunday Passage , 20°32.3'S 149°01.4' E,dead, 27 m (2 v,C.120173) ; E of Mackay , 20°52'S 149°29'E,dead, 35 m (4 v, C.116567) ; E of Sarina , 21°27.5' S 150°08'E,alive, 42 m (1 pr + 4 v,C.119586) ; E of Sarina , 21°28'S 150°08.5'E, dead, 40 m (1 v,C.372139) ; SE of Sarina , 21°47'S 150°34' E,dead, 59 m (1 v,C.116488) ; off Broad Sound , 22°06'S 150°49'E,dead, 53 m (1 v, C.116498) ; off Yeppoon , 22°40' S 151°16' E, dead, 58 m (1 v, C.372140) ; Keppel Bay , W of North Keppel Island , 23°04' S 150°53' E, dead, 3.5 m (2 v, C.372143) ; Keppel Bay, North Keppel Island, 23°04'S 150°54' E, dead (2 v, C.077224); Keppel Bay , between Outer Rock & Man & Wife , NE of South Keppel Island , 23°08'S 150°56' E,dead, 24–26 m (8 v,C.372142) ; Keppel Bay , 1.5 ml NW of South Keppel Island , 23°08'S 150°56'E,alive, 13–20 m (1 pr,C.372157) ; Keppel Bay , 1.5 ml NW of South Keppel Island , 23°09'S 150°57' E,dead, 13–20 m (1 v, C.372141) ; Keppel Bay, Humpy Island , 23°13'S 150°58'E,dead, 3.5 m (2 v,C.124012) ; Keppel Bay, 23°25'S 150°55'E, dead (1 pr, C.130887); Port Curtis, 23°55'S 151°23'E, dead (1 v, C.012050); Port Curtis , Hummock Hill Island , 24°01'S 151°28'E, dead (1 pr, C.069959); off Burnett Heads, 24°46' S 152°24' E, alive, 27–46 m (3 pr, C.097570; 6 pr,C.097572) ; Bargara, near Bundaberg, 24°49' S 152°28'E, (2 pr, alive,C.130888; 4 v, dead, C.130889); Hervey Bay , 25°06'S 152°49'E, alive, 18–27 m (3 pr, C.130890) ; Hervey Bay, off Picnic Point , 25°06'S 152°49'E, alive, 15 m (2 pr, C.097565) ; Hervey Bay, Frazer Island, Moon Point , 25°13'S 153°0'E, alive (1 pr, C.071651); Hervey Bay , Torquay , 25°17'S 152°52'E, dead (10 v, C.103804); Hervey Bay , Urangan , 25°17'S 152°54'E, alive (1 v, C.070049; 2 pr, C.071924; 2 pr, C.103801; 18 v, C.130891); Hervey Bay, Dundowran, 25°18'S 152°46'E, alive (2 pr, C.083154; 6 pr, C.097573; 3 v,C.372144); Hervey Bay, Dundowran Beach, 25°18'S 152°46'E,dead(2 v,C.372145); Hervey Bay , S of Woody Island , 25°18.5'S 152°56'E,alive, 9 m (3 pr,C.097569) ; off Tin Can Bay, 25°50' S 153°27.5'E, alive (1 pr, C.062511); Moreton Bay, 27°15'S 153°15'E, dead (1 pr, C.303784); off S end of Stradbroke Island , 27°43'S 153°35'E, alive, 48–59 m (1 pr, C.372150) ; Moreton Bay, Stadbroke Island, Amity Point , alive (7 pr, WAM). NEW SOUTH WALES : SE of Yamba , 29°28' – 29°33'S 153°30'– 153°25'E, dead, 51–55 m (6 v, C.154253) ; Sydney Harbour , 33°51'S 151°14'E, 1 v, dead (C.060601). WESTERN AUSTRALIA: Dirk Hartog Island, SE corner, 26°04'S 113°12' E, dead, 4–7 m (1 v, WAM) ; Dirk Hartog Island, E side, Louisa Point , 25°43'S 113°15'E, dead, 18 m (4 v, WAM) ; Shark Bay , 10 mls W of Bernier Island , 24°52'S 112°58' E, alive, 73 m (1 pr, WAM) ; Shark Bay, Denham Sound , 25°43'S 113°15'E, alive, 16–18 m (1 pr, WAM) ; Shark Bay, approx. 25°30' E 113°30'E, alive (1 pr, WAM); Shark Bay, 26°07'S 113°25'E, alive (1 pr, C.119736); Shark Bay , Useless Loop , 26°08'S 113°25'E, dead (1 v, C.372154); Exmouth Gulf, off Exmouth, Town Beach , 21°57'S 114°07'E, dead, 10 m (1 v, WAM) ; Onslow , c. 10 mls NNW, 21°30'S 115°03'E, dead, 119 m (1 v, WAM) ; DampierArchipelago, North Enderby Island , 20°36' S 116°30' E,dead, 16 m (1 v, WAM) ; Dampier Archipelago, Causeway Beach , 20°40.5'S 116°41.5'E, alive (1 pr,C.372158) ; ENE of Montebello Islands , 20°18' –16'S 116°01'E, alive (1 pr, WAM); North West Shelf , 26 n. ml NNE of Dampier , 20°14.6'S 116°50.9'– 116°50.6' E, dead, 40–41 m (1 v, C.149897) ; North West Shelf , 44 n. ml NW of Port Hedland , 19°56.7'– 19°56.9' S 117°53.6' – 117°53.4'E, alive, 40 m (2 pr, C.372159) ; North West Shelf , 45 n. ml NNE of Port Hedland , 19°55.2'– 19°55.6' S 117°56' – 117°55.6'E, dead, 40 m (2 v, C.372093) ; 72 mls NW of Bedout Island , dead, 46 m (2 v, WAM) ; Dampier Archipelago , N of Rosemary Island , 19°47'–45'S 116°33'–35'E, dead, 60–64 m (1 v, WAM) ; North West Shelf , 52 n. ml NNE of Port Hedland , 19°30.9' – 19°28.2'S 118°49.2'– 118°55.4'E, alive, 36–37 m (2 pr + 9 v, C.148705) ; North West Shelf , 76 n. ml NNE of Port Hedland , 19°04.9'– 19°04.7' S 118°50.6' – 118°50.8'E,dead, 81 m (1 v,C.148671) ; North West Shelf , 80 n. ml NNE of Port Hedland ,19°03.6'– 19°03.4'S 119°03.4'– 119°03.5'E,dead, 82 m (6 v, C.147423) ; 10–20 mls W of Lagrange Bay , dead, 22–46 m (1 v, WAM) ; c. 200 mls ENE of Troughton Island , dead, 64 m (2 v, WAM) . NORTHERN TERRITORY: E of Darwin, Gun Point, dead (3 v, WAM); Clarence Strait , NW of Charles Point , 12°08'S 130°06.7' E, dead, 33 m (1 v, WAM) ; Arafura Sea , 10°13'S 133°58'E, dead, 72 m (1 v, C.129686) ; Arnhem Land, North West Crocodile Island, 11°42'S 135°10'E, dead (1 v, C.090470); Gulf of Carpentaria , Groote Eylandt , 14°0'S 136°25'E,dead (4 v,C.372100) .

Description. Shell up to c. 50 mm high, solid, inflated, many specimens pyxoid to more compressed, oblong, almost equally convex, almost equivalve and equilateral; left valve almost flat, right valve slightly more convex; auricles slightly unequal in shape and size, the anterior longer; umbonal angle 85–90°; left valve uniform cream, yellowish, pinkish or brownish, many specimens maculated with dots and streaks; right valve paler or whitish; interior of hinge plate dark brown, paler ventrally.

Both valves sculptured with 5–7 primary radial plicae, most specimens with 5; with a narrow, weak plica at anterior and posterior ends of disc; numerous fine, closely spaced secondary riblets on plicae and in interspaces in late growth stage. Closely spaced commarginal microsculpture on pre-radial and radial stages. Auricles with closely spaced commarginal microsculpture, on left valve with numerous radial riblets, on right valve fewer in number, weak or absent on some specimens. Dorsal margin straight. Byssal

Figure 37. Distribution of Decatopecten strangei (Reeve) .

notch, fasciole and functional ctenolium lacking. Intenal rib carinae prominent near ventral margin. Resilifer narrowly triangular. Hinge teeth consisting of weak resilial teeth and 3–7 prominent intermediate and dorsal teeth.

Dimensions. Illustrated specimen: QLD, Hervey Bay, Dundowran Beach (AM C.097573): rv: H 42.3, L 39.4 mm; lv: H 42.3, L 40.1 mm; D 12.4 mm.

Habitat. Juveniles byssally attached to clumps of oysters, adults free-living amongst clumps of oysters and sea grass ( Zostera ) on soft sediment in the littoral zone (sand or muddy sand).

Distribution. Restricted to Australia, from Dirk Hartog Island (Western Australia) northwards to the Northern Territory, eastwards to Torres Straits (northern Queensland) and southwards to Yamba, northern New South Wales. The single valve from Sydney Harbour, New South Wales (AM C.060601; Iredale, 1936: 269, pl. 20, fig. 3) was dredged from beneath the harbour floor and is possibly a fossil from a previous warm interglacial period. Decatopecten strangei does not occur in other areas of the Indo-West Pacific. The maximum living depth range is from intertidal to 73 m.

Remarks. Decatopecten strangei is closely allied to D. plica ( Linnaeus, 1758) , a common species from the tropical Indo-West Pacific. The two species can be moreor-less distinguished by the characters identified in Table 2 . It is possible that the present species is only a southern geographical variant of Decatopecten plica , because their differences in shape, size and sculpture are weak.