Thyonicola dogieli is a parasite of sea cucumbers such as
Cucumaria miniata. On encountering sea water the cocoons burst open and the free-living larvae are liberated. They are about long, and unless swallowed by a sea cucumber, they will soon die, However, any that are ingested undergo
metamorphosis in the host's gut, lose their shell and mantle and burrow into the wall of the gut with the aid of a glandular secretion. As the juvenile mollusc grows, its posterior end pushes its way into the sea cucumber's body cavity, and the gonads develop, the interior of the mollusc becoming a brood pouch. ==References==