Ultrastructure of the Midgut of the Copepod Mytilicola Intestinalis Steuer, an Endoparasite of the Mussel Mytilus Edulis L.

Mytilicola intestinalis is a parasitic copepod in the intestine of the blue mussel Mytilus edulis. The copepod midgut was examined by means of transmission electron microscopy to determine whether gut cell structure resembled that of other copepods in which the alimentary system is functional. Several characteristic cell types were found in the midgut of Mytilicola, along with detrital matter in the gut lumen. It is concluded that the alimentary canal of Mytilicola is not vestigial and is actively involved in the uptake of nutrients.