Feeding behavior of the infaunal bivalve Tagelus dombeii (Lamarck, 1818). Suspension vs. deposit feeding

The feeding behavior of two populations of the bivalve Tagelus dombeii (Lamarck, 1818) was studied through laboratory experiments, with the purpose of establishing a possible dual feeding strategy (suspensivore/detritivore). Individuals from both the intertidal population of Coihuín (near Puerto Montt, Chile) as well as those from the subtidal of Corral Bay (near Valdivia) showed continuous suspension feeding with total absence of deposit feeding when immersed, and always showed their open siphons flush with the sediment surface. These observations were confirmed by the high clearance rates shown by both populations of T. dombeii, similar to the ones described for obligate suspension feeding bivalves. Different results were obtained during emersion, since T. dombeii individuals from both populations displayed their siphons on the sediment (3-5 cm), thus behaving as deposit feeders. Deposit feeding was observed in up to 80% of individuals. The present study allows to conclude that T. dombeii is primarily a suspension-feeder, which might be related to the dominance of sand (>92%) in the habitat of both populations studied. Growth coincides with periods of suspended particulate food supply increase in the natural environment. This suggests that T. dombeii would be competing for the particulate food supply with the community of obligate suspension feeding bivalves in these habitats.