Dictionary of Ichthyology  

endoparasite = an internal parasite, e.g. the fish Carapus apus living in the body cavity of holothurians and feeding on the gonads and water lungs. But see also inquiline.

Fierasfer (= Carapus) from Lydekker et al. "Reptiles, Amphibia, Fishes and Lower Chordata", 1912. Photograph by Brian W. Coad.

Canadian Museum of Nature
www.briancoad.com