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.
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
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.