Myxosporidia and macrophage centres in chub (Leuciscus cephalus) - quantitative interactions focus on Myxobolus cyprini

Six myxosporidian species were found in chub (Leuciscus cephalus) originati ng from Lon er Austrian rivers. The frequency of the parasites and their lo calization was recorded. In all chub, independent of size and origin, Myxob olus cyprini occurred predominantly in the macrophage centres (MCs) of the haematopoietic organs, spleen and kidney. Exclusively in the head kidne? of young fish not yet described vermicular plasmodia containing spores of M. cyprini were Found. In muscle tissue the prevalence of M. cyprini was compa ratively low. Other species of Myxobolus characterized by plasmodial cysts frequently occurred in gills and swimbladder but were rarely detected, and only in small numbers, in the haematopoietic organs. The number of M. cypri ni spores and the relative volume of MCs in the haematopoietic organs were estimated in order to examine possible correlations. Significant interrelat ed changes were found only in juvenile fish up to a size of 15 cm. In bigge r fish, the number and size of macrophage aggregates were highly variable a nd independent of infection intensity and fish size, but the number of spor es never exceeded that of the aggregated macrophages. The data suggest that due to an early date of infection M. cyprini is the only species which is closely associated with macrophage aggregation.