THE ANALYSIS OF POSSIBLE PATHWAYS OF MONO GENEAN INFESTATION (MONOGENEA, PLATHELMINTHES)

According to our data, the swimming larvae of dactylogyrids settle on the body surface not only of young fishes, but also of adult ones. The opinion of Wunder-Llevellin about three pathways of monogenean infest ation of hosts is wellconfirmed. The cutaneous way is settling of swim ming larvae of lower monogeneans on the body surface of a host. Subseq uently, it either stays on the surface or, after a certain period of g rowth, the postlarva moves onto the site of attachment of abult worm ( usually gills). The address way is when the swimming larva reaches imm ediately the site of parasitizing of adult worms (for example, gills f or higher monogeneans). The contact way is observed in non-ciliated la rvae, when eggs are attached to worms or hosts, when invasive stages a re adults, when worms are transferred by crustaceans or fishes, under reproduction by the means of non-ciliated larvae in urinary bladder of amphibians, or in the cases of infestation at the time of copulation of hosts (Eupolystoma, Isancistrum). The address way evolved from the cutaneous one. Different forms of contact infestation are explained. T he transition from non-ciliated larva of acanthocotilids to viviparity in gyrodactylids is shown. The hypothesis of primary absence of swimm ing ciliated larvae In monogeneans is suggested. The cutaneous way of infestation is considered as primary one and, therefore, ectoparasitis m of some monogeneans on body surface of hosts - as a primitive charac ter. If the haptor of pro-monogeneans was armed only with marginal hoo ks, than the absence of anchors in some ectoparasitic groups of monoge nens could be considered as a primitive character. The hypothesis of i ndependent origin of anchors, saucerlike pseudohaptors and clamplike s tructures in different groups of monogeneans is suggested.