Entovalva nhatrangensis
Entovalva nhatrangensis is a species of small marine bivalve mollusc in the family Lasaeidae. It was first described in 2010 and its specific name "nhatrangensis" derives from the locality where it was originally found, Nha Trang Bay in Vietnam. It lives inside the oesophagus of certain species of sea cucumbers. It is considered to be an endosymbiont rather than a parasite because it does not harm its host. Description Entovalva nhatrangensis can grow to about in length. It has a very small, delicate shell which is internal, being entirely enclosed by large folds of the mantle which fuse above the hinge. The gills are small but their structure is similar to those of other free-living bivalves. The foot extends permanently from the ventral side of the animal. This is relatively large compared to other bivalves and contains the visceral mass and the gonads. Entovalva nhatrangensis can be distinguished from the other three previously described species in the genus Entovalva by the different shape of its body and foot, and by the fact that its outer body epithelium is distinctively folded. Biology Entovalva nhatrangensis is an endosymbiont living inside the oesophagus of a sea cucumber. In a research study undertaken in