Ultrastructural observations on sporozoite stages of piscine Coccidia: Goussia carpelli and G. subepithelialis from the intestine of tubificid oligochaetes

Abstract

Sporozoites of the piscine coccidians Goussia carpelli and G. subepithelialis excysted from sporocysts when ingested by tubificid oligochaetes Tubifex tubifex and Limnodrilus hoffmeisteri, and invaded cells of the alimentary tract. There the sporozoites were found singly in membrane-bound parasitophorous vacuoles and persisted for 9 wk for G. carpelli and 3 wk for G. subepithelialis. The fine structure of the sporozoites agreed with ultrastructural details known from other eimerian type sporozoites. The cells possessed e.g. refractile bodies, micronemes and dense granules, and were limited by a 3-layered pellicle. G. carpelli sporozoites, which were studied in more detail, showed no alteration in ultrastructure during 9 wk of observation and remained infective for carp. © Inter-Research.