Equichlamys bifrons ( Lamarck, 1819 )

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 : 232-235

Equichlamys bifrons ( Lamarck, 1819)

Figs 63B,D–H, 64, 65A–C,F

Pecten bifrons Lamarck, 1819: 164 , no. 4; Deshayes, 1836: 131, no. 4; Delessert, 1841: pl. 15, figs 5a–c; Chenu, 1843: 3, pl. 22, figs 3–3b; Reeve, 1852: sp. 45, pl. 12, fig. 45; Chenu, 1862: 184, figs 925–926; Tenison Woods, 1878a: 33, 56; Tate & May, 1901: 440; Chapman, 1920: 229; Dijkstra, 1994: 472, pl. 2, figs 4–5, pl. 3 figs 6–7 [lectotype].

Pecten subbifrons Tate, 1882: 44 ; Tate, 1886: 104, pl. 3, fig. 2.

Pecten consobrinus Tate, 1886: 104 , pl. 3, fig. 6; Tate & Dennant, 1893: 224; Harris, 1897: 317; Tate, 1899: 269.

Pecten palmipes Tate, 1886: 105 , pl. 5, fig. 4, pl. 7, figs 4a–b; Harris, 1897: 318.

Chlamys bifrons (Lamarck) .–Pritchard & Gatliff, 1904a: 263; Hedley, 1918a: M9; May, 1921: 10; May, 1923: pl. 3, fig. 6; Coleman, 1975: 273, fig. 626.

Equichlamys bifrons (Lamarck) .– Iredale, 1929: 162; Cotton & Godfrey, 1938: 94, fig. 79; Macpherson & Chapple, 1951: 145; Cotton, 1957: 127; Cotton, 1961: 97, fig. 82; Macpherson & Gabriel, 1962: 306, fig. 348; Iredale & McMichael, 1962: 11; Richmond, [1990]: 46, fig. 126; Waller, 1991: 30, pl. 3, figs 9–10; Rombouts, 1991: 38, pl. 14, figs 3–3a; Lamprell & Whitehead, 1992: [24], pl. 10, fig. 60; Slack-Smith, 1998: 275, 277, text-fig. 6.18D, pl. 13, fig. 2; Beu & Darragh, 2001: 53, text fig. 1, figs 13A–H, 14A–F; Raines & Poppe, 2006: 190–191, upper figs; pl. 137, figs 1–5; pl. 138, figs 1–5; Huber, 2010: 206.

Chlamys (Equichlamys) consobrina (Tate) .– Ludbrook, 1955: 31; Ludbrook, 1959: 225, pl. 1, fig. 2.

Chlamys (Equichlamys) subbifrons (Tate) .– Ludbrook, 1959: 224, pl. 1, fig. 1.

Chlamys (Equichlamys) palmipes (Tate) .– Ludbrook, 1959: 225, pl. 1, figs 3–6.

Chlamys (Equichlamys) bifrons palmipes (Tate) .– Ludbrook, 1978: 46, pl. 2, fig. 5.

Chlamys (Equichlamys) bifrons subbifrons (Tate) .– Ludbrook, 1978: 47, pl. 2, figs 6–7; Ludbrook, 1983: 47; Ludbrook, 1984: 240.

Chlamys (Equichlamys) bifrons (Lamarck) .– Ludbrook, 1984: 160, 296, pl. 8f, figs 38a–b; Ludbrook & Gowlett-Holmes, 1989: 642, figs 11.37a–b, pl. 42, fig. 5.

Type data. Pecten bifrons Lamarck : lectotype (pr) MNHN Moll21188, designated by Dijkstra (1994: 472), 3 paralectotypes (pr) MNHN Moll21189, one paralectotype (pr) MHNG 1088/14/2, figured by Delessert (1841: pl. 15, figs 5a–c) and by Chenu (1843: pl. 22, figs 3–3b; 1862: figs 925–926), one possible paralectotype (pr) MHNG 1088/14/1. Type locality: “Les mers australes et de la Nouvelle Hollande. Péron ”. This type locality is in part incorrect as the species is restricted to southern Australia (see Dijkstra, 1994: 472).

Pecten subbifrons Tate : lectotype SAM T959A, designated by Ludbrook (1959: 224), Tate’s (1886: pl. 3 fig. 2) figured specimen, 4 paralectotypes SAM T959B–D. Type locality: “Adelaide”, i.e., Hallett Cove Sandstone, late

Figure 63. A, C, Coralichlamys madreporarum (G. B. Sowerby II) , pair, AM C.090374, holotype of Coralichlamys acroporicola Iredale, Low Isles , near Port Douglas, QLD; rv exterior (A), lv exterior (C). B, D–H, Equichlamys bifrons (Lamarck) ; (B–F) 2 pairs, AM C.097523, Henley Beach, SA; rv exteriors (B, D), lv exteriors (E, F); (G, H) large pair, AM C.102328, off Hobart, TAS; lv exterior (G), rv exterior (H). Scale bars represent 10 mm (A, C), 30 mm (B, D–H).

Pliocene ( Ludbrook, 1959). See also Beu & Darragh (2001). Pecten consobrinus Tate : lectotype SAM T937B, designated by Ludbrook (1959: 225, 233) as “ holotype ” statement, Tate’s (1886: pl. 3 fig. 6) figured syntype, paralectotype

SAM T937 A. Type locality: “Oyster Banks, Aldinga”, i.e., Hallett Cove Sandstone, late Pliocene. Four paralectotypes SAM T968 A–D, unfigured, not conspecific with lectotype and from other localities. See also Beu & Darragh (2001).

Figure 64. Distribution of Equichlamys bifrons (Lamarck) (circles) and Hemipecten forbesianus A. Adams & Reeve (stars).

Pecten palmipes Tate : lectotype SAM T932A, designated by Ludbrook (1959: 225), Tate’s (1886: pl. 7 figs 4a–b) figured syntype, paralectotype SAM T932B. Type locality: Edithburgh, South Australia, Hallett Cove Sandstone, late Pliocene.

Comments on type data. See Beu & Darragh (2001: 55).

Additional material examined. — AUSTRALIA: VICTORIA: Between Green Cape & Snowy River mouth, 38°0'S 149°30'E, alive, 91–183 m (1 pr,C.374883) ; S of Gabo Island , 38°08'S 149°55'E, alive, 183–457 m (8 v, C.037005) . TASMANIA: Bass Strait, Flinders Island, Settlement Point , 40°01'S 147°51'E, dead (5 v,C.129066); Bass Strait, Flinders Island , Arthur Bay , 40°03' S 147°56'E, dead (1 v, C.129068); Bass Strait, Flinders Island , S side of Trousers Point Beach, 40°13'S 148°02'E, dead (1 v, C.129067); Tomahawk Point, S of Tomahawk Island, 40°52'S 147°46'E, dead (1 v, C.080634);Bass Strait,off Devonport, 41°05'S 146°22'E,dead, 26–69 m (1 v,C.375045) ; Hobart, 42°53'S 147°19'E, alive (2 pr, C.002417; 1 pr, C.102328); Hobart, Derwent River , 42°53'S 147°19'E,dead (1 pr, C.375033;1 pr,C.375037); Derwent River ,opposite Hobart ,Bellerive, 42°53'S 147°22.5' E,dead (5 v,C.111413); Hobart , Sandy Bay , 42°54'S 147°20'E,dead (1 pr, C.086689;1 v,C.111406); Cremorne Bay , 42°58'S 147°32'E, dead (2 v,C.375043);D’Entrecasteaux Channel,Pierson’s Point to SE, 43°02.7'S 147°20.83'E, dead, 14.5–16.5 m (1 v, C.375032) ; Tinderbox Bay , S of Hobart, 43°03' S 147°20'E, dead, 15 m (10 v, C.300340) ; D’Entrecasteaux Channel , 43°03.5' S 147°20.5'E, alive, 12–27 m (9 v, C.058571; 4 pr, C.097524; 4 v, C.097526) ; D’Entrecasteaux Channel, Killora Bay , 43°05.6'S 147°19.2'E, alive, 7.5 m (1 pr + 1 v, C.096121) ; Port Arthur, Long Bay , 43°06'S 147°51.5'E, dead (1 pr,C.375039); D’Entrecasteaux Channel, 1 ml W of Simpsons Point, 43°14.6'S 147°15'E,dead, 9–13 m (7 v,C.374890) ; Bruny Island, off Simpsons Point , 43°14'S 147°19'E, alive, 11 m (2 pr, C.086644) ; D’Entrecasteaux Channel, Simpsons Bay, South Bruny Island , 43°17'S 147°18'E, alive (1 pr,C.054110); Mills Reef,off W coast Bruny Island , 43°19.5'S 147°14.5' E,dead, 2 m (1 v,C.375030) . SOUTH AUSTRALIA: Lacepede Bay, SE of Kingston, 36°50'S 139°51'E, dead (2 v, C.104184); Port Elliott, 35°32'S 138°41' E,dead (1 v,C.132128);Henley Beach, 34°56'S 138°31'E,dead (2 pr,C.097523); Adelaide ,Outer Harbour, 34°49' S 138°29'E,alive (3 pr, C.073487); Adelaide , Outer Harbour Beach, 34°49'S 138°29'E, alive (2 pr, C.097525); Adelaide ,Semaphore Beach, 34°50'S 138°29'E,alive (4 v, C.097527;2 pr, C.374887; 1 pr,C.374888);PortAdelaide, 34°52'S 138°30'E,dead (3 pr,C.374889); Adelaide beaches, 34°51'S 138°30' E, dead (3 pr, C.089653); Largs North Beach , c. 19 km N of Adelaide, 34°49' S 138°29'E, dead (2 v, C.116884); Adelaide , off Glenelg, 34°59'S 138°28.5'E, alive, 3.5 m (10 v, C.374885) ; Adelaide, 3.2 km off Glenelg , 34°59' S 138°28.5' E,alive, 11 m (1 pr,C.375056) ; Port Noarlunga, 35°09.1'S 138°27.8'E,dead (3 v,C.374886); Port Noarlunga, Onkaparinga Point , 35°10'S 138°27.5'E, alive, 14 m (2 pr, C.375054) ; Port Pirie, Solomontown Beach , 33°12'S 138°01'E, dead (1 v, C.124976); Sir Joseph Banks Group, N of rocks between Lusby and Partney Islands ,alive, 6 m (1 pr, SAM D18993) ; St.Vincents Gulf , 35°0'S 138°0'E,dead (2 pr,C.004560); Yorke Peninsula, Lowly Point, alive, 9–18 m (7 pr, SAM D18995) ; Yorke Peninsula, Edithburgh Jetty , alive, 5 m (2 pr, SAM D18997) ; NE of Kangaroo Island, Penneshaw , 35°43'S 137°56'E, alive, 5 m (2 pr,C.375058) ; Kangaroo Island, Eastern Cove, Rocky Point , 35°48' S 137°50.2'E,dead (3 v, C.374872); Kangeroo Island , American River near Ballast Point jetty, 35°45.8' S 137°48'E, alive, 3 m (2 pr, C.111265) ; Whyalla, Backy Point, 32°55'S 137°47'E, dead (1 pr, C.119784); Upper Spencer Gulf , Port Bonython , 33°01'S 137°45'E, alive, 15 m (1 pr, SAM D18994) ; Edithburgh, 35°05'S 137°45'E, alive (1 pr, C.375055); Yorke Peninsula, off Edithburgh , 35°05'S 137°45.5'E, alive, 9 m (4 pr, C.375050) ; Kangaroo Island, American River, 35°48'S 137°45' E, dead (2 v, C.132130); Tickera Bay , near Kadina , 33°46'S 137°43'E,dead (1 pr,C.080132); Kangaroo Island , Kingscote , 35°39'S 137°38'E, dead (1 v, C.049182); Tiparra Reef, off Point Hughes , 34°03'S 137°24' E, alive, 6–7.5 m (1 pr, C.112554) ; Wallaroo, 33°55'S 137°36'E, dead (6 v, C.374884); off Kangaroo Island, 35°0'S 137°0'E,dead (6 v, C.030802); Spencer Gulf , Tumby Bay , 34°22' S 136°08'E, dead (3 v, C.374870); Donington Island ,off Port Lincoln , 34°43.3'S 136°0'E, dead, 7–9 m (1 pr, C.303778) ; Sir Joseph Banks Group, SE point of Lusby Island , alive, 6 m (1 pr, SAM D18996) ; Port Lincoln , 34°44'S 135°54'E, alive, 15 m (3 pr, C.375051) ; Port Lincoln , 34°47'S 135°51'E, alive, 9 m (3 pr, C.012162; 1 pr, C.119786; 3 pr, C.108902) ; Coffin Bay , 34°37'S 135°27'E, alive, 6 m (3 pr,C.375052) ; Smoky Bay, 32°18' S 133°50'E,dead (2 v,C.070260);W side of Thevenard,near Ceduna, 32°09'S 133°39'E, dead (6 v, C.095245); Petrel Bay , N of St Francis Island, 32°29'S 133°18'E,dead, 20–30 m (1 v,C.374871) . WESTERNAUSTRALIA: GreatAustralian Bight , 33°05'S 128°40'E, dead, 75 m (1 v, C.374868) ; Great Australian Bight , 34°21'S 121°16' E, dead, 82 m (4 v, C.374869).

Description. Shell up to 135 mm high (Huber, 2010), most specimens smaller than 80 mm; solid, circular, right valve slightly more convex than left, to equally inflated; somewhat equivalve and equilateral, auricles almost equal, umbonal angle c. 100–115°; cream with purplish radial streaks, most specimens purplish, a few orange or brownish, interior of most specimens purplish.

Both valves sculptured with 7–11 obvious, evenly spaced radial plicae (most specimens with 8–10), varying greatly in prominence, narrowly angular to more broadly rounded. Interspaces of left valve each wider than one plica, plicae of right valve each wider than one interspace. Numerous widely to closely spaced radial riblets on plicae and interspaces; coarse shagreen microsculpture throughout on juveniles and some unabraded adults, more developed into commarginal lamellae near ventral margin on some adults. Auricles with 6–10 weak, narrow radial riblets. Byssal notch moderately shallow, byssal fasciole very weak. Functional ctenolium present in juveniles, lacking in adults. Internal rib carinae prominent near ventral margin.

Dimensions. Illustrated specimens: TAS, off Hobart (AM C.102328): rv: H 103.5, L 106.5 mm; lv: H 103.8, L 107.5 mm; D 33.4 mm; SA, Henley Beach (AM C.097523), larger specimen: rv: H 79.4, L 83.7 mm; lv: H 81.9, L 88.0 mm; D 27.5 mm; smaller: rv: H 65.5, L 67.0 mm; lv: H 68.0, L 68.9 mm; D 23.6 mm.

Habitat. In South Australia living free in the littoral to sublittoral zones on soft sediment, prefering clean sand, and on seagrass, Zostera (“ribbon weed”). In Tasmania on silty-muddy bottom conditions amongst shell rubble, generally in deeper water. Wolf & White (1997) discussed the factors affecting the distribution of Equichlamys bifrons in fishing grounds in D’Entrecasteaux Channel, Tasmania. Mendo et al. (2014) also commented on the environments preferred by the three commercial scallops E. bifrons , Mimachlamys asperrima ( Lamarck, 1819) and Pecten fumatus in D’Entrecasteaux Channel. They concluded that P. fumatus is associated with fine-grained sediment, shells and macroalgae, and is affected by the abundance of the invasive seastar Asterias amurensis . Equichlamys bifrons is strongly associated with macroalgae and seagrass cover, and abundant M. asperrima is strongly associated with sponge cover.

Distribution. Southernmost New South Wales, Victoria, Tasmania, South Australia westwards to the Great Australian Bight, SE Western Australia (present data; Raines & Poppe, 2006: 190). Present specimens alive at 3–91 m (minimum depth range).

Remarks. For synonymy and comparison with fossil species see Beu & Darragh (2001: 57). The present species is aquacultured and utilized for commercial

Figure 65. A–C, F, Equichlamys bifrons (Lamarck) , specimens in Fig. 63B, D–F; rv exterior (A), lv interior (B), lv exterior (C), rv interior (F). D, E, Hemipecten forbesianus A. Adams & Reeve , pair, AM C.303801, Torres Strait, QLD; lv exterior (D), rv interior (E). Scale bars represent 30 mm (A–C, F), 10 mm (D, E).

consumption. Dix (1976) and Cragg (2016) described the unusual lecithotrophic development of Equichlamys bifrons , which contrasts strongly with the planktotrophic development and correspondingly long larval life of most other common shallow-water scallops. Cragg (2016: 36) noted that “Lecithotrophic development occurs in a temperate-water pectinid ( Equichlamys ), sublittoral cavedwelling cyclochlamydids and propeamussiids … the coral reef Caribachlamys … the hydrothermal vent Catillopecten (= Bathypecten ) vulcani and bathyal to abyssal pectinids ( Hyalopecten ) and propeamussiids … Planktotrophic development is the dominant mode in euphotic waters, but where suspended particulate food is limited … or where the parental environment is extremely patchy … lecithotrophic development may improve the chances of survival to settlement in the parental environment. Lecithotrophic development may also correlate with small adult size”. Another southern Australian species, Notochlamys hexactes ( Lamarck, 1819) , also has lecithotrophic development, acquired independently. Presumably this mode of development is responsible for the great range of variation shown by both E. bifrons and N. hexactes , because of the lack of genetic exchange between distant populations.