Remarks on Eimeria cotti from the intestine of bullhead (Cottus gobio).

Eimeria cotti, a gut dwelling coccidian parasite from bullhead (Cottus gobio) is described from fish collected from waters of a natural resort area in North-West Germany. All age groups of bullhead were found to be infected throughout the year at a prevalence of 43 out of 92 fish examined. Infected tissue contained merogonic, gamogonic and sporogonic developmental stages. Ultrastructural features of these stages conformed with those of other eimerian coccidia. Merozoites were formed by ectomerogony, macrogamonts exhibited a prominent electron dense inclusion, and mature oocysts had a stieda body.