BIOLOGY OF FEEDING IN THE SCAVENGING ISOPOD NATATOLANA-BOREALIS (ISOPODA, CIROLANIDAE)

The marine benthic isopod Natatolana borealis (Lilljeborg) displays at tributes of a voracious omnivorous scavenger. It exhibited no preferen ce for particular carrion types when given the choice between fish or crustacean tissue (variously treated) in situ. It was not attracted to live scampi (Nephrops norvegicus). Cannibalism of damaged or moulting individuals was observed frequently in the laboratory. Gut contents f rom field-collected animals frequently contained the remains of polych aetes and crustaceans, though whether these had been ingested live is unknown. Natatolana borealis processes food in the manner of a 'batch reactor'. It bolts food rapidly and unselectively, stores it in its ex tensible anterior hindgut, then takes a long time (weeks) to digest a single meal. It is inferred to have a high assimilation efficiency and can survive for long periods (months) without food. Sated isopods do not respond to food, but engage in a brief burst of post-prandial acti vity that would remove them from the immediate vicinity of a food-fall , and hence the attentions of predatory fishes. Response to food odour was kinetic and involved sensory organs situated on both pairs of ant ennae. The chemical signals to which the isopods react are thought to be simple molecules of universal occurrence.