Tissue‐Specific Resident and Transient Microbial Communities of the Quagga Mussel, Dreissena bugensis , and the Eastern Elliptio, Elliptio complanata

Microbial symbioses are common across invertebrate taxa, in part because the suspension‐feeding strategy of many species exposes them to free‐living and particle‐associated microbes. Most research on bivalve microbiomes has involved marine species, but less focus has been on freshwater bivalves.

Marine bivalves show a resident and transient framework associated with digestive tissues, with some microbes likely forming persistent, residential associations and others exhibiting transitory associations.

The purpose of this study was to characterize the resident and transient microbial communities of the gut and gill from the quagga mussel, Dreissena bugensis , and eastern elliptio, Elliptio complanata .

Mussels were collected from natural populations and dissected to isolate tissues immediately or after 24 h of depuration. Environmental water samples and faeces deposited during depuration were collected, and all samples underwent 16S SSU rRNA marker gene sequencing. Organs from both mussel species displayed distinct microbial communities from their source water.

Allowing animals to egest faeces, or depurate, affected tissue microbial communities, indicating that the resident and transient framework is prevalent in freshwater bivalve species.

Taxonomic differences between quagga mussels and elliptios may indicate that phylogenetic history, habitat, and gill structure play a role in determining the composition of host‐associated microbial communities in these species.