Taxonomic problems, seasonality and histopathology of Henneguya creplini (Myxosporea) infection of the pikeperch Stizostedion lucioperca in Lake Balaton

Plasmodia of a Henneguya species measuring 70-900 mu m and exhibiting seaso n-dependent stages of development were detected throughout a three-year stu dy on gill myxosporosis of Lake Balaton pikeperch (Stizostedion lucioperca (L.)). Sixty-five out of 160 fish (41%) examined in the period of study wer e infected by the parasite. Infection was the most prevalent (48%) among pi keperch specimens exceeding 40 cm in length. The highest prevalence of infe ction (58%) was recorded in 1995-1996 while the lowest (30%) in 1996-1997. The youngest plasmodia appeared in April, and started to develop within the capillaries of the secondary lamellae of the gill filaments. The round or ellipsoidal plasmodia which continued their gradual growth in the subsequen t months of the year achieved a size of 800-900 mu m by the late autumn mon ths, but remained in intralamellar location throughout the developmental cy cle. Mature spores developed in the plasmodia by the end of winter. On the basis of their shape and size, the spores were identified as Henneguya crep lini (Gurley, 1894). However, because of the uncertain taxonomy of species assigned to the genus Henneguya the taxonomic position of the parasite requ ires further study. The host reaction consisting of epithelial proliferatio n and granulation tissue formation starts around the infected secondary lam ella only after the maturation of spores and the disruption of plasmodia.