It has a very small, delicate shell which is internal, being entirely enclosed by large folds of the mantle which fuse above the hinge.

In a research study undertaken in 2010, 23 sea cucumbers known as brown sandfish (Holothuria spinifera) were gathered from shallow waters in Nha Trang Bay in Vietnam.

Another sea cucumber, Holothuria leucospilota, also acts as a host to the bivalve but of 30 specimens collected from the same locality, only one was found to harbour any of them, and that one contained just 5 molluscs.

The stomach was found to contain diatoms, therefore it is likely that the bivalve uses its gills to filter them and other fine organic particles from the contents of the sea cucumber's gut in which it is immersed.

Fertilization takes place when a male inserts spermatophores (bundles of sperm) into the gill cavity of a female.