A coccidium parasitic in the heteronemertean Quasilineus lucidoculatus: first record of a coccidian infection in a nemertean

Abstract

Stages in the life cycle of an eimeriine coccidian parasitic in the gut of the heteronemertean Quasilineus lucidoculatus are described and illustrated. The absence of sporocysts and sporozoites prevents a generic diagnosis from being established. The pathogenic effects of the infection are discussed. A coccidian infestation has not previously been reported from any species of nemertean. Several references to parasitic infections in nemertean worms can be found in the literature. Although metazoan forms, such as nematodes or trematodes, have been encountered occasionally (Gibson, 1972), most infections reported concern unicellular parasites. These include gregarines in the gut or within blood vessels (Kölliker, 1848); Moore & Gibson, 1973; Roe, 1976), an unidentified 'sporozoan' in the gut (Punnett, 1901) and haplosporidia in a variety of other body structures, particularly the parenchyma (Brinkmann, 1917; Debaisieux, 1920; Jennings & Gibson, 1968; Gibson & Moore, 1979; Varndell, 1980). Ciliates have also been seen within the intestinal lumen (Fenchel, 1965; Jennings, 1968). An isolated instance of hyperparasitism, involving a microsporidian living in the tissues of monocystid gregarines inhabiting a nemertean gut, was reported by Vinckier et al. (1970). There are no previous records of coccidian infections occurring in nemerteans.