THE APICAL COMPLEX OF THE GREGARINE DIGYALUM-OWENI (PROTOZOA, APICOMPLEXA)

The aseptate gregarine Digyalum oweni is parasitic in the gut of some species of Littorina, marine gastropod molluscs. The apical complex comprises a mucron (described previously), polar ring, polar ring extension, subpellicular microtubules and rhoptries; and possibly also micronemes and dense granules. The polar ring extension is possibly a microtubule organizing centre. The method by which D. oweni attaches to its host cell may be similar to that used by intracellular apicomplexans to invade host cells. After attachment of D. oweni to the host cell the rhoptries may secrete enzymes into the host cell prior to digestion.