Species in the Order, 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, (Superfamily: Poromyoidea) shown at right, is fairly typical in feeding behavior to other Superfamilies in this Order; e.g., the Verticordioidea and Cuspidarioidea. Many of the genera in these superfamilies 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.
The classification system below follows that of
Bouchet et al. (2010), in which the Anomalodesmata are now considered to be monophyletic, based on molecular analysis, anatomical analysis, shell morphology and shell microstructure; also, followed by the Worldwide Mollusc Species Data Base (WMSDB).
- Class: Bivalvia
- Subclass: Heterodonta
- Order: Anomalodesmata
- Superfamily: Poromyoidea
- Family: Poromyidae
- Major Genera
Poromya granulata (Nyst & Westendorp, 1839)
Drawing reproduced by permission of author; Brian Morton, "Prey capture in the carnivorous septibranch Poromya granulata (Bivalvia: Anomalodesmata: Poromyacea)". In, Sarsia 66:241-256, 1981.
(above) 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.
The Poromyidae also possess red amoebocytes in their blood stream that carry a high molecular weight hemoglobin pigment. This and the shared modifications described at left point to a degree of evolutionary development that few other bivalves have achieved in adapting to new habitats.