Poromya granulata observed in a natural position in the sand, with its inhalant siphon fully extended. Note the projecting cowl, which is extended for capture of a 2.5 mm long crustacean, typical of food found in its stomach. The 15 tentacles and the siphon are a bright red color.

Drawing is reproduced by permission of the author, Brian Morton, from the article "Prey capture in the carnivorous septibranch Poromya granulata (Bivalvia: Anomalodesmata: Poromyacea)"; Sarsia, v. 66, pp. 241-256, 1981.

A Carnivorous Mini-Clam!

Species in the subclass, Anomalodesmata, account for over 70% of all those benthic and abyssal clams that feed carnivorously or by scavenging tissue fragments --a mode of feeding that is unusual and not at all characteristic of the vast majority of bivalves.

Among the Anomalodesmata, the small deep water clam, Poromya granulata, (Family: Poromyidae) shown at left, is fairly typical in feeding behavior. Like the Verticordiidae and Cuspidariidae families, which also comprise the Poromyacea superfamily, many genera have a similarly large, eversible inhalant siphon. The siphon can be quickly retracted, with the prey, by strong retractor muscles that invert the cowl to bring food to the mouth. It is believed that the tentacles, which bear ciliary sense organs, are used to detect motion and thereby serve to locate prey. Moreover, the intestine is remarkably modified for digestion of large food fragments.

Poromya also possesses red amoebocytes in the blood stream, which seem to carry a hemoglobin pigment. This and the several modifications described above point to a degree of evolutionary development that few other bivalves have achieved in adapting to new niches.