They live and feed and grow in the mussels, but their complete life cycle stumped researchers because eggs were never observed in these hosts.
About 24 days later, the young hatch out (shown in the photo), make their way out of the cocoon and swim off to find new mussel hosts.
Urastoma cyprinae is believed to feed on the mucus secreted by its host and its presence alters the protease composition of gills in C. virginica.
Urastoma cyprinae is negatively phototatic and is more attracted to oysters when compared to other mollusc species such as mussels and clams.
It exhibits some similarities with the Chlamydiales reported in marine invertebrates, but differs in the morphology of its elementary bodies.