Particle selection and feeding behaviour in two cirratulid polychaetes

Abstract

Cirratulid polychaetes are abundant and diverse members of the benthic macrofauna and their particle collection mechanisms may strongly affect particle mixing and sediment grain size distribution in sediments. The feeding morphology differs in having a pair or many feeding tentacles and the ecological importance of both methods of food collection needs to be better investigated to understand their costs and benefits. Particle selection and feeding behaviour of a bitentaculate (Aphelochaeta honouliuli) and a multitentaculate species (Timarete hawaiensis) were comparatively observed. Feeding behaviour observations were done with individuals with or without feeding tentacles and exposed to three different size ranges of glass beads (0–20, 40–70 and 70–110 µm in diameter). Particle selection was tested for coated and uncoated glass beads of three different size ranges in 20 specimens of each species. Feeding behaviour was similar in both species and the methods of particle collection and ingestion are described. Individuals of T. hawaiensis, in which the feeding tentacles were removed, were observed collecting particles with the aid of branchiae. The multitentaculate species studied was more successful in collecting particles from greater foraging radii and at a faster rate than the bitentaculate species but the experimental design may have disfavoured the latter. Two-way ANOVA results showed that both bitentaculate and multitentaculate species significantly selected in favour of smaller particle sizes. Further studies about particle encounter, selection and ingestion are needed and may aid understanding of the phylogenetic relationships between the bitentaculate and multitentaculate cirratulids.