The burrowing behaviour and diet of thyasirid bivalves from Bonne Bay, NL

Abstract

Thyasirids are an interesting model group due to the presence of sulfur-oxidizing symbionts in some species but not all. Symbiotic thyasirids form numerous burrows (i.e. pedal tracts) to obtain sulfides. Asymbiotic thyasirids were not expected to produce similar burrows as they have no need for sulfides. Comparisons of the burrowing behaviour of symbiotic and asymbiotic thyasirids from Bonne Bay, Newfoundland were made. Unexpectedly, no differences in burrowing depth, number or length of pedal tracts were found between symbiotic and asymbiotic thyasirids. To explore whether pedal tracts of asymbiotic thyasirids might be used for "farming" chemoautotrophic bacteria, we performed stable isotopic analysis (carbon and nitrogen). As expected, the symbiotic taxon consumes mainly thiotrophic bacteria, and one of the asymbiotic taxa consumes mainly suspended material. Contrary to expectations, the other asymbiotic taxon consumed mainly thiotrophic bacteria, in a greater proportion than the symbiotic taxon, indicating that “microbial farming” is likely occurring for that taxon.