Decatopecten radula radula (Linnaeus, 1758)
LINNAEUS, C. 1758. Sistema Naturae per Regna tria NaturaeNaturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio Decima, Reformata. Holmiae: Laurentii Salvii, iii + 824 p. [p. 697, sp. 161]
1758 Ostrea radula Linnaeus, 1758
1939 Comptopallium pauciplicatum Iredale, 1939
1939 Comptopallium pauciplicatum Iredale, 1939
«Habitat. Commonly living free in the littoral zone in several different habitats: 1) Under large slabs in silty mud at extreme low tide; 2) Amongst branching corals and rubble inside calm lagoons, usually in clean shallow water; 3) In shallow water on clean sand, surrounded by large groups of sea urchins; 4) Amongst coral slabs and rubble in shallow water on soft sediment (muddy bottoms) in strong currents; 5) Rarely in deep water amongst rubble on soft sediment, muddy sand or mud.
«Distribution. Throughout the Indo-West Pacific from southern Japan southwards to northern Australia, westwards to the Maldive Islands, according to Huber (2010) to East Africa, and eastwards to the Samoan Islands; South China Sea, intertidal zone to 20 m (Bernard et al., 1993: 50); Philippines, intertidal zone to c. 80 m (Raines, 2010: 604; Dijkstra, 2013: 31); Indonesia, intertidal to 6 m (Dijkstra, 1991: 43); Papua New Guinea, 2–30 m (Dijkstra, 1998a: 18); East Africa to East China, 0–32 m (Huber, 2010: 198). Maximum depth range from intertidal to 120 m (unpublished data, HHD). Present material from Australia living at subtidal to 55 m.
Remarks. The 9–11-ribbed geographical form with weak commarginal lamellae on the radial plicae, similar to Comptopallium pauciplicatum, has a wide distribution from the Northern Territory through Queensland, P. N. G. and eastwards to Samoa. Examined material from off Kimberley (northwestern Australia) is more closely similar to Decatopecten radula griggi (9-ribbed with closely spaced, strong commarginal lamellae on the radial plicae). This ecomorph is restricted to the northwestern coast of Australia. Most examined material from the Cocos Keeling Islands and Indonesia and northwards to China and southern Japan has 11–13 radial plicae, although a few specimens have been examined with 9–10 costae from Singapore and southern Japan (NSMT). The present specimens from the Montebello Islands region (WA) are similar in radial sculpture to those from Indonesia, although the commarginal lamellae on the plicae are slightly more prominent.
The geographical morphs recognized are: Decatopecten radula radula (11–14 ribs, most specimens 11–13): Cocos Keeling Islands, Monte Bello-Onslow area (WA), Scott Reef, Seringapatam Reef and Ashmore Reef (Timor Sea), Indonesian Archipelago, Philippine Islands, China and southern Japan. Decatopecten radula pauciplicatus (9–11 ribs, most specimens 9–10): Northern Territory, S Arafura Sea (Indonesia), Papua New Guinea, Solomon Islands, Coral Sea, New Caledonia, Fiji Islands, Samoa. The 9-ribbed Kimberley (Northwestern Australia) ecomorph described by Webb (1957) in our opinion is a “sister-population” of the D. radula pauciplicatus morph. It is observed that other pectinid species (viz. Mimachlamys scabricostata and Complicachlamys wardiana) from northern Western Australia also have extremely strongly developed commarginal lamellae on the radial costae, possibly due to ecological conditions in that area. Again, the specific epithet radula is an indeclinable noun (Latin, a scraper).» DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 187]
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Decatopecten radula (Linnaeus, 1758); H. H. Dijkstra & A. G. Beu, 2018, Living scallops of australia and adjacent waters, figures 36A, 36C, 38A, 38C.
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«Description. — Shell solid, up to c. 120 mm high, most specimens 60-70 mm, oblong, left valve flat to weakly inflated, right valve more convex, inequivalve, inequilateral (posterior margin longer than anterior), auricles well-developed, slightly unequal in shape and size, umbonal angle about 85˚; left valve cream with commarginal brown spots and bands, right valve paler or whitish, interior of hinge plate dark brown. Both valve sculptured with 9-13 primary radial plicae; secondary riblets on plicae and in interspaces in late growth stage. Closely spaced, delicate to coarse commarginal lamellae on plicae. Auricles with 3-8 weak to coarse radial costae. Hinge line straight. Byssal notch shallow, byssal fasciole moderately wide, functional ctenolium weak or lacking in mature specimens. Resilial pit triangular and oblong. Hinge teeth very weak or lacking.
Distribution. — Throughout the Indo-West Pacific from southern Japan southwards to Australia, westwards to the Maldive Islands and eastwards to the Samoa Islands. South China Sea: intertidal zone to 20 m (Bernard, Cai & Morton, 1993: 50), Philippines: 9-25 m (Raines, 2010: 604), Indonesia: intertidal to 6 m (Dijkstra, 1991: 43), Papua New Guinea: 2-30 m (Dijkstra, 1998a: 18). Present specimens from the Philippines alive at intertidal to c. 80 m. The bathymetric range of live-taken specimens is from intertidal to 120 m (ZMA, unpublished data). Commonly living free in different habitats: 1) Under large slabs in silty mud at extreme low tide. 2) Amongst branched corals and rubble inside calm lagoons usually in clean shallow water. 3) In shallow water on clean sand, surrounded by large groups of sea urchins. 4) Amongst coral slabs and rubble in shallow water on soft sediment (muddy bottoms) in strong currents. 5) Rarely in deep water amongst rubble on soft sediments of muddy sand or mud. Remarks. — Most examined material from Indonesia and northwards to China and southern Japan has 11-13 radial lirae, although a few specimens have been examined with 9-10 costae from Singapore and southern Japan (NSMT). The 9-11 ribbed geographical form with weak commarginal lamellae on the radial lirae, similar to Comptopallium pauciplicatum, has a wide distribution from the Northern Territory through Queensland, P.N.G. and eastwards to Samoa. Examined material from off Kimberley (northwestern Australia) is more similar to Decatopecten radula griggi (9-ribbed with closely spaced, strong commarginal lamellae on the radial lirae). This ecomorph is restricted to the northwestern coast of Australia. The present specimens from the Philippines are morphologically similar to the type specimens. Geographical subspecies could be determined as: Decatopecten radula radula (11-14 ribbed, most specimens 11-13): Indonesian Archipelago, Philippine Islands, China and southern Japan. Decatopecten radula pauciplicatus (9-11 ribbed, usually 9-10): Northern Territory, S Arafura Sea (Indonesia), Papua New Guinea, Solomon Islands, Coral Sea, New Caledonia, Fiji Islands, Samoa. The 9-ribbed D. radula griggi (Webb, 1957) from Kimberley (Northwestern Australia) is in my opinion a junior synonym of D. radula pauciplicatus.» DIJKSTRA, H. H. 2013. Pectinoidea (Bivalvia:
Propeamussiidae and Pectinidae) from the Panglao region, Philippine Islands. Vita
Malacologica, 10: 1-108, pls. 1-32 pls, 2 tabs. [p. 31, 33]
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Decatopecten radula radula (Linnaeus, 1758); H. H. Dijkstra, 2013, Pectinoidea from the Panglao region, plate 6, figures 1a-d.
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«Type locality
“Habitat in O. Indico”. Restricted herein to Indonesia. Specimens examined (ZMA) from China have more radial costae (13–14) than are mentioned by Linnaeus (1758, 1764, 1767), and than occur on specimens from Australia to the Samoa Islands (9–10).
UUZM (isolated by Odhner):
(1) A box with one specimen and two handwritten Thunberg labels ‘‘Mus.Gust.Ad.’’ and ‘‘radula’’. On the outside of the posterior auricle an ink number ‘‘161’’, referring to Ostrea radula number 161 of the tenth edition (1758: 697), is visible, and on the inside of each valve ‘‘Radula’’ is marked in pencil. This specimen matches the diagnosis of Linnaeus (1758, 1764) and is designated herein as the lectotype (Fig. 8A) (see also Wallin, 1993: 88, Ostrea radula # 491). (2) A box with one specimen and two handwritten Thunberg labels ‘‘Mus.Gust.Ad.’’ and ‘‘radula’’ without other marks (see also Wallin, 1993: 88, Ostrea radula # 492). UUZM (general collection): Another box with one specimen and a printed Swartz label ‘‘Radula’’, no Thunberg labels (see Wallin, 1993: 88, Ostrea radula # 1051). LSL (isolated by Hanley): The specimen isolated by Hanley (1855: 104), marked ‘‘radula’’ in pencil on the inside of the right valve near the umbo, was probably added by the younger Linnaeus (Hanley, 1855: 105). Remarks The conflicting references used by Linnaeus (1758, 1764, 1767) were discussed by Hanley (1855: 104), Iredale (1939: 360) and Dodge (1952: 167). Only figure A of plate 44 (Rumphius, 1705) matches the present species, cited by Linnaeus (1764: 525) as ‘‘f.AA’’. The specimens isolated by Odhner (1953: 5) accord with Rumphius’ fig. A, and not with fig. D [ = Lima vulgaris Link, 1807, det. Dijkstra], nor with fig. B [ = Ostrea pallium Linnaeus, 1758, det. Dijkstra].» DIJKSTRA, H. H. 1999. Type specimens of Pectinidae (Mollusca: Bivalvia) described by Linnaeus (1758-1771). Zoological Journal of the Linnean Society, 125: 383-443, figs. 1-10. [p. 402, 403]
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Ostrea radula Linnaeus, 1758; H. H. Dijkstra, 1999, Type specimens of Pectinidae (Mollusca: Bivalvia) described by Linnaeus (1758-1771), figure 8A.
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«In the tenth edition of the 'Systema,' Rumphius, pl. 44, f. D, and its copy in Klein (pl. 9, f. 34) were inadvertently cited for a species ("radiis 12"), to which they bear no resemblance; the references were removed in the final edition to Ostrea lima, and the present citation substituted. The name radula, though appertaining properly to the former figures only, was still retained and appended falsely to the changed letters. In his own revised copy Linnaeus has erased the reference to B, which letter was not cited either in the 'Museum Ulricae,' The description in that work coincides with the characters of the Pecten which, recognised generally as the representative of the species, bears its name in both modern and ancient publications. That shell (Knorr, Délices, pt. 5, pl. 9, f. 4) is present in the Linnean cabinet, but as its presence is not indicated in our author's list, it was probably added by his son, whose citation of "List. Conch, t. 175, f. 12 suprema.— Arg. t. 24 (= 27 of the edition cited by the father), f. D — Gualt. t. 74, f. L" favours the received opinion.»
HANLEY S. C. T. 1855. Ipsa Linnaei Conchylia. The Shells of Linnaeus, Determined from his Manuscripts and Collection. Williams & Norgate. London [p. 104, 105]
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Knorrs, G. W., 1774, Verlustiging der oogen en van den geest, volume 5, plate 9.
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