Quantitative aspects of deposit feeding inAbra nitida(Müller) andA. longicallus(Scacchi) (Bivalvia, Tellinacea)

Abstract

The investigation is based on material from populations in the depths of Korsfjorden, western Norway. The faecal pellets are described and classified. The process of gut clearance of individuals placed in glass vessels without any sediment was much retarded compared to individuals dwelling in native sediment. Gut capacity increases with increased shell length in A. nitida and remains principally constant in A. longicallus. Gut capacity per unit weight of the animal gives curves of opposite slope for the two species. The relative amount of deposit ingested per 24 hours is principally constant in A. nitida, but decreases with increasing size in A. longicallus. Estimations concerning the degree of reworking of the deposit by a hypothetical population of A. nitida indicate that one individual takes the same deposit into the mantle cavity approximately 50 times during one year. It is assumed that only A. nitida, with regard to sediment reworking, can play an important role in the biotope, because of its occasional high abundance. A time of adaptation to the aquarium situation is necessary before any experimental results can be considered reliable.