The Queen Scallop, Chlamys opercularis (L., 1758) (Bivalvia, Pectinidae), as a food item of the sea anemone Urticina eques (Gosse, 1860) (Actiniaria, Actiniidae)

Scantly detailed knowledge is available about the food of sea anemones, but we do know that many species, especially intertidal forms, are opportunistic feeders on sizeable prey, such as other Coelenterata, Crustacea, Echinodermata and Mollusca, notably gastropods. Representatives of the genus Urticina Ehrenberg, 1834 ( = Tealia Gosse, 1858) occurring both intertidally and in moderate depths, are well-known as large prey predators (Slinn, 1961; Den Hartog, 1963; Sebens & Laakso, 1977; Shimek, 1981; Thomas, 1981). Slinn (loc. cit.) reported an incidental record of two actinians brought in by Port Erin scallop fishermen, identified as Tealia felina (L., 1761), but more likely to represent Urticina eques (Gosse, 1860), each of which had ingested an individual of the sea urchin Echinus esculentus L., 1758. Den Hartog (loc. cit.: 77-78) referring to the Dutch coast reported the starfish Asterias rubens L., 1758, to be the main food item of the shore-form of Urticina felina (L., 1761) [often referred to in the older literature as Tealia coriacea (Cuvier) or the var. coriacea; cf. Stephenson, 1935], including specimens considerably exceeding the basal diameter of the anemones. Second-common was the crab Carcinus maenas (L. 1758) (carapax width up to 30 mm) and further noteworthy is a record of a specimen of the rather rigid scyphozoan Rhizostoma octopus (L., 1788) [as R. pulmo (Macri, 1778)] with an umbrella almost twice the basal diameter of its swallower. Thomas (loc. cit.) presented a photograph made in situ at Point Lobos, California, of an Urticina lofotensis ¹ (Danielssen, 1890) engulfing a sizeable starfish, Patiria miniata (Brandt, 1835), remarkably itself a species reported as a predator of the sea anemone Anthopleura elegantissima (Brandt, 1835) (cf. Francis, 1973: 80) and belonging to the same family as the genus Urticina (!); one therefore wonders whether this record might not actually refer to the superficially similar Dermasterias imbricata (Grube, 1857) occurring in similar habitats and known to feed primarily on Corallimorpharians and sea anemones (Lambert, 1981: 94; Annett & Pierotti, 1984), including Anthopleura elegantissima (cf. Mauzey et al., 1968: 610). The presence of sizeable starfish, viz., Henricia leviuscula (Stimpson, 1857) (diameter: 80-120 mm) in the gastric cavity of Urticina lofotensis, again from the U.S. west coast (San Juan Archipelago, Washington State), was also reported by Sebens & Laakso (1978: 161), and these same authors reported pholidid fish (up to 150 mm long) from a new Urticina species, which they appropriately named Tealia piscivora. Shimek (loc. cit.) mentioned the sea-urchin Strongylocentrotrus droebachiensis (O.F. Müller, 1776) to be the principal food item of Urticina crassicornis (O.F. Müller, 1776) in the vicinity of Flomer, Alaska.