Semipallium aktinos ( Petterd, 1886 )

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 : 261-263

Semipallium aktinos ( Petterd, 1886)

Figs 78B,D, 79, 80A–B

Pecten aktinos Petterd, 1886: 320 .

Pecten bednalli Tate, 1887a: 73 , pl. 4, figs 3a–b.

Chlamys bednalli (Tate) .–Hedley, 1900: 495, pl. 25, figs 10–13.

Pecten actinos [sic] Petterd.–Tate & May, 1901: 441.

Chlamys aktinos (Petterd) .–Pritchard & Gatliff, 1904a: 265; Hedley, 1918a: M8; May, 1921: 10; May, 1923: pl. 3, fig. 10; Wells & Bryce, 1985: 158, fig. 580; Richmond, 1992: 85, fig. 121.

Mimachlamys (Belchlamys) aktinos (Petterd) .– Iredale, 1929: 164.

Scaeochlamys atkinos [sic] (Petterd).–Macpherson & Chapple, 1951: 145.

Chlamys (Camptonectes) aktinos Petterd [sic].–Gabriel, 1956: 14.

Belchlamys atkinos [sic] (Petterd).–Cotton, 1953: 22; Cotton, 1961: 100, fig. 86.

Mimachlamys aktinos (Petterd) .–Iredale & McMichael, 1962: 11.

Chlamys atkinos [sic] (Petterd).–Macpherson & Gabriel, 1962: 303, fig. 345.

Chlamys (Chlamys) aktinos (Petterd) .–Dijkstra, (1983–1989) 1983: 3, figs; Ludbrook & Gowlett-Holmes, 1989: 642.

Chlamys (Belchlamys) aktinos (Petterd) .– Rombouts, 1991: 22, pl. 8, fig. 5; Lamprell & Whitehead, 1992:[22], pl. 9, fig. 49.

Semipallium aktinos (Petterd) .–Beu & Darragh, 2001: 75, figs 18A–D, 21A–G; Raines & Poppe, 2006: 232–233, upper figs; pl. 184, figs 1–7; Huber, 2010: 206.

Type data. Pecten aktinos Petterd : possible syntypes ( QVM9 : 105—lv; 1 pr QVM9 : 106—pr). Type locality: Northwest coast of Tasmania.

Pecten bednalli Tate : lectotype (pr) SAM D14170, herein designated, possible paralectotypes (1 pr + 5 v, SAM D16381 ; 1 v, SAM D15644). Type locality: South Australia, Aldinga Bay, near Adelaide .

Comments on type data. The articulated possible syntype QVM9:106 (H 39 mm, W 34 mm, D 14 mm) of Pecten aktinos is closest to the measurements of the original description (“Long. 42 mm, lat. 36 mm, alt. 15 mm ”), but cannot be considered a syntype with any certainty as it does not bear a label identifying it as Petterd material.

Figure 79. Distribution of Semipallium aktinos (Petterd) (circles), S. dianae (Crandall) (stars) and S. dringi (Reeve) (triangles).

Additional material examined. — AUSTRALIA: QUEENSLAND: Capricorn Channel, 16.8 ml NE of North Reef, 23°08'S 152°12'E, dead, 115 m (1 v, C.345467); off S end Frazer Island, 25°48'S 153°46'E, dead, 73 m (1 v, C.345468); Alexandra Head , 26°40'S 153°07'E,dead (6 v,C.119535); Caloundra , 26°49'S 153°10'E, dead (5 v, C.012777; 1 v, C.012778; many v, C.097504; 4 v, C.119536; 1 v, C.132068; 2 v, C.132069;1 v,C.345465); NE of Cape Moreton , 26°55'S 153°33'E, dead, 115–124 m 3 v, C.345379; 2 v, C.345466); E of Moreton Bay, 26°55' S 153°33' E, dead, 115–176 m (1 v, C.345469) . NEW SOUTH WALES: Woolgoolga, 30°06'S 153°12'E, dead (1 v, C.132067); South West Solitary Island ( Groper Island ), 30°09'S 153°13'E, alive (2 pr,C.099833); South West Solitary Island ( Groper Island ), 30°09'S 153°13' E,alive, 6–9 m (2 pr, C.137033); South West Solitary Island ( Groper Island ), 30°16.2'S 153°22.7'E, alive, 9 m (1 pr, C.157579); Split Solitary Island , N side, 30°15' S 153°11' E, dead, 9–12 m (1 v,C.156352);Camden Haven Inlet, 31°38'S 152°49'E,alive (2 pr,C.344184); S of Port Macquarie, 32°02'S 152°40'E,dead, 47 m (3 v,C.345353);Sydney, Collaroy Beach, S end, 33°44'S 151°18'E, dead (3 v, C.119533); Sydney, Port Jackson , Watsons Bay , Green Point, 33°50'S 151°16' E,alive, 15 m (1 pr,C.008095); Sydney, Port Jackson ,off Sow & Pigs Reef, 33°50' S 151°16' E,dead, 9 m (1 pr,C.097505); Sydney, Port Jackson , 33°51'S 151°14' E,dead (1 v,C.132066) . VICTORIA: Sandy Point, Western Port, just N of North Arm, 38°24' S 145°14'E,dead, 7.5 m (1 v,C.127100); Rye , Port Phillip , 38°25' S 144°49'E,dead (1 v,C.345413); Western Port Bay , Flinders , 38°29'S 145°01'E,dead (2 v, C.119532) . TASMANIA: Black River Beach, near Stanley , 40°51'S 145°18'E,dead (1 pr, C.097503;1 pr,C.103821); Devonport, W of Don River mouth, 41°09'S 146°19'E,dead, 7 m (2 v,C.143410) . SOUTHAUSTRALIA: NuytsArchipelago, N of St Francis Island, 32°29' S 133°18'E, dead, 20–30 m (3 v, C.345414); Spencer Gulf, Tumby Bay , 34°22'S 136°08'E,dead (2 v,C.095652); Port Stanvac , 35°06'S 138°28'E,dead (7 v,C.303773); Port Noarlunga , Horseshoe Reef , 35°08'S 138°27'E,alive, 3 m (2 pr,C.114446); Royston Head , 35°11'S 136°51'E,dead (4 v,C.008665); Neptune Islands , 35°17'S 136°05'E,dead, 73 m (1 v,C.019245); Aldinga Bay , 35°17'S 138°29' E,alive (1 pr,C.007882);S coast of Kangaroo Island , 36°0'S 137°11'E, dead (8 v, C.090610); Yorke Peninsula , Edithburgh Jetty , alive, 4–5 m (2 pr, SAM D18998); Sir Joseph Banks Group , reef NW of Hareby Island, alive, 2–6 m (1 pr, SAM D18999); Encounter Bay , Whalers Wharf , The Bluff , alive, 2 m (1 pr, SAM D19000); O’Sullivans Reef ,alive, 3 m (1 pr, SAM D19001); Gulf of St Vincent , c. 3 km N of Wirrina boat ramp, alive, 5–6 m (3 pr, SAM D19002); Nuyts Archipelago, N of St Francis Island, dead, 27–37 m (2 v, SAM D190003 ) . WESTERN AUSTRALIA: RechercheArchipelago,off Remark Island, 34°04'S 122°0'E,dead (1 pr, C.132062); Great Australian Bight , E of Hood Point, 34°21'S 121°16' E, dead, 82 m (3 v,C.345451); off Albany , 35°14'S 118°30'E, dead, 124 m (1 v, C.345464); South Point , S side of Two Peoples Bay , near Albany , 34°58'S 118°11'E, dead (1 v, C.099888; 1 v, C.345450);off Albany , 35°09'S 117°46'E,dead, 62 m (1 v,C.345463); S of Wilson Inlet, 35°12'S 117°0'E, dead, 73–77 m (2 v, C.345449); E of Cheyne Bay, 34°55' S 119°0'E, dead, 71–76 m (1 v,C.117452); Windy Harbour , 34°50'S 116°0'E,dead (1 v,C.345455); South Cowaramup , 33°53'S 114°59'E, dead, beach (2 v, C.345454); Geographe Bay , 33°37'S 115°18'E, dead (3 v, C.018016); Dunsborough , 33°36' S 115°06'E,alive, 0–3.6 m (1 pr + 1 v, C.345456); Garden Island , S of Perth, 32°14'S 115°41'E, dead, beach (3 v, C.345457); Fremantle , 32°03'S 115°44' E, dead (1 v, C.345453); Fremantle , Hall Bank , 32°02'S 115°43'E,alive, 8 m (2 pr, C.345459); Perth , Cottesloe Beach & nearby beaches, 31°98.3'S 115°75' E, dead (many v, C.345476); Scarborough , near Perth , 31°54'S 115°44' E, dead (1 v, C.345458); Triggs , near Perth , 31°52'S 115°45'E, dead (1 v, C.345452); W of Jurien Bay, 30°16'– 30°17.9'S 114°39.0'– 114°39.9'E, dead, 82 m (1 v, C.345462); W of Green Head, 30°04' S 114°47'E, dead, 51 m (1 v, C.300339); W of Green Head, 29°45' S 114°42'E, dead, 50 m (1 v, C.345461); approx. 24 km SW Dongara, 29°20' – 29°21'S 114°43' – 114°42'E, dead, 40 m (2 v, C.345460); Kimberley, Long Reef, S side, 14°01' S 125°44'E, dead (1 v, WAM 522 ) .

Description. Shell up to c. 42 mm high, most specimens under 30 mm; elongate, moderately prosocline, weakly

Figure 80. A, B, Semipallium aktinos (Petterd) , specimen in Fig. 78B, D; lv exterior (A), rv exterior (B).C, E, J, Semipallium dringi (Reeve) , specimen in Fig. 78G, I; lv exterior (C), lv interior (E), rv exterior (J).D, Semipallium dianae (Crandall) , specimen in Fig.78H;lv exterior.F, G, Semipallium flavicans (Linnaeus) , AM C.131558, subtidal, Broadhurst Reef, E of Townsville, GBR, QLD; lv exterior (F), rv exterior (G). H, I, Semipallium fulvicostatum (A.Adams & Reeve) , AM C.131560, subtidal, Broadhurst Reef, E of Townsville, GBR, QLD; rv exterior (H), lv exterior (I). Scale bars represent 20 mm (A–C, E–J), 10 mm (D).

inflated, valves almost equally convex, auricles highly unequal in shape and size, umbonal angle c. 85°; colour variable, yellow, purple, pink to reddish and brown, with patches and streaks, interior shining white or tinted pink.

Left valve sculptured with 9–11 low, narrow, widely spaced primary radial costae or weak plicae, variable in prominence, more subdivided on right valve into 18–20 narrow costae, increasing by intercalation to 60–80 delicate, narrow, closely spaced, weakly squamous radial riblets near ventral margin. Shagreen microsculpture present throughout. Anterior auricles much larger and longer than posterior, bearing c. 8–10 radial riblets on left valve and c. 6 on right; posterior auricles bearing fewer, weaker riblets. Byssal notch relatively deep, byssal fasciole rather narrow. Functional ctenolium well-developed, with c. 5 teeth. Internal plicae with carinate edges around ventral margin. Hinge with moderately prominent resilial and dorsal teeth.

Dimensions. Illustrated specimen: SA, Port Stanvac, under rock slabs (AM C.303773): rv: H 38.4, L 32.4 mm; lv: H 38.6, L 31.5 mm; D 11.5 mm.

Habitat. Living cryptically in the littoral zone, byssally attached under rocks or on ledges, and hidden in reef crevices, many specimens covered with sponges.

Distribution. This endemic species is most common in temperate waters, and is not recorded from the tropical Indo-West Pacific outside Australia. Present specimens alive in the intertidal zone to 15 m.

Remarks. A closely similar congeneric cryptically living species is Semipallium hallae (Cotton, 1960) , known only from South Australia. Semipallium hallae differs from S. aktinos in its larger size (up to c. 55 mm high, S. aktinos up to 42 mm), in having a more nearly circular shape ( S. aktinos is more elongate), in having larger posterior auricles (in S. aktinos very small, almost rudimentary), in having 7–8 broad primary radial plicae on both valves ( S. aktinos has 9–11 narrow plicae on the left valve, more subdivided on the right valve), and in its purplish, almost monochrome coloration ( S. aktinos is more polychrome).