Histochemical characteristics of Gyrodactylus derjavini parasitizing the fins of rainbow trout (Oncorhynchus mykiss)

Histochemical studies of enzyme activities and structural elements in Gyrod actylus derjavini Mikailov, 1975 parasitizing fins of Oncorhynchus mykiss W albaum were conducted. Marked activities of non-specific esterase, acid pho sphatase, alkaline phosphatase and amino-peptidase were found in the intest inal caeca of the parasite. A strong activity of acetylcholinesterase was s een in the nervous system. Extraintestinal non-specific and eserine-sulphat e resistant esterase was localized in the distal part of the hamulus sheath . Activities of peroxidase and glucuronidase were not detected. In the embr yo, developing hamuli were enclosed in a sheath rich in phospholipids. Depo sits of neutral lipids were sparse. The fully developed ventral and dorsal hamulus bars stained strongly for calcium. Lectin binding assays showed a m annose rich region in the cephalic duct openings, strong reactions for gala ctose in the glycocakyx whereas reactions for lactose were weak. These find ings are discussed with respect to the parasite-host relationship.