Biology of feeding in the scavenging isopod Natatolana borealis (Isopoda: Cirolanidae)

abstract

The marine benthic isopod Natatolana borealis (Lilljeborg) displays attributes of a voracious omnivorous scavenger. It exhibited no preference 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 narvegicus). Cannibalism of damaged or moulting individuals was observed frequently in the laboratory. Gut contents from field-collected animals frequently contained the remains of polychaetes and crustaeeans, 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 extensible 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 activity 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 antennae. The chemical signals to which the isopods react are thought to be simple molecules of universal occurrence.