RECENT KNOWLEDGE ON THE DEVELOPMENT AND P ATHOLOGY OF MYXOSPOREAN FISH PARASITES - REVIEW ARTICLE

Myxosporeans are frequent and pathogenic parasites of fish. They are c haracterized by a complicated way of development, a relatively strict host specificity and a strict tissue specificity. During intrapiscine development (in the organism of the fish), myxosporeans have a vegetat ive stage and a sporogenic stage. Extrapiscine development takes place in Oligochaeta alternative hosts in which another spore producing sta ge, regarded earlier as Actinosporea, develops. Fish become infected b y actinosporean spores. The author has distinguished three main types of myxosporean development (Myxobolus-, Hoferellus- and Sphaerospora-t ypes), In the Myxobolus-type development (Fig. 8), spores are formed i n large plasmodia in a tissue specific for the given parasite; coelozo ic (Hoferellus-type) development (Fig. 9) means that the early develop ment of myxosporeans takes place in the cells lining the efferent duct s while the second stage occurs in the lumen of the aforementioned duc ts. During Sphaerospora-type development (Fig. 10), a short intracellu lar stage, one or two blood stages characterized by a series of intern al cleavage and a coelozoic or intercellular sporogonic stage can be d istinguished.