Temporal variation in chemoautotrophic symbiont abundance in the thyasirid bivalve Thyasira cf. gouldi

Within the bivalve family Thyasiridae, symbioses with chemoautotrophic, sulphur-oxidizing bacteria do not occur in all lineages; variation in symbiont presence and in the degree of abfrontal expansion of gill filaments occurs on fine phylogenetic scales within the family. Thyasirid symbionts are harboured extracellularly and are periodically engulfed and digested by host gill epithelial cells. Symbiotic thyasirids are mixotrophic, retaining the …