Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

that two other distinct tapeworm species, which might be mistaken fori? macrophallus occur in this fish. Examining these two, he described the P. microscopicus and refrained from naming the other. In agreement with the above mentioned authors (Mitchell and Hoffman 1980, Thatcher 1981) the final host infested by the adult cestodes hardly ever suffers from pathological lesions caused by the invaders. However the results of histological examination and epizootological studies show that plerocercoids are potentially pathogenic to various young fry in the hot neotropical regions. Local fish species in such climate can feed on infested copepods even as their first food, and so they may be invaded by hundreds of parasites during the first days of their life. According to our estimate the first 5-7 days are the most crucial from this aspect. Remarkable losses can occur, and a considerable decrease of the yield can be manifested. Weak and impaired specimens can easily fall prey to cannibalism, which is a very common phenomenon in tropical fish cultures, and thus a further production drop will occur. Later on, fishes can more easily withstand heavy parasite invasion. The adult fish is positively able to tolerate encysted plerocercoids, though some researchers believe that the larvae located near the testes or ovary may inhibit the development of the sexual product thus causing possible sterility (Freeman 1964, Hoffman 1967). We found plerocercoid invasion exclusively in such water systems, where tucunare had been introduced previously from the Amazon. This fish is a delicacy for the local people, which explains the large demand for its increased production. The parasitic invasion was particularly intense in waters where plankton density had been artificially boosted by the use of fertilizers. This is a common practice in the fish farms of the Brazilian Northeast, too. No effective method has been found to control the parasites yet. A possible means would be the technique of selective plankton production by the use of organophosphates (Dipterex, etc.) which eliminate copepod plankton populations for a few days (Woynárovich 1985). This alone may be sufficient to prevent parasite invasions of dangerous level. We are convinced that the metacestodosis caused by the larvae of proteocephalid cestodes of tucunare is a potential threat to several fish species in the neotropical regions. Effective control methods should be developed for the practice, as fish propagation has an overwhelmingly important role in regions deficient in animal protein. Békési L., Assis Feitosa V. és Cabrai F. A. B.: Tenyésztett halivadékban Proteocephalida galandférgek (Cestoda) plerocercoidjai által okozott metacestodosis Északkelet-Brazíliában A szerzők a Brazil-Északkeleten tenyésztett halfajokban egy eddig ismeretlen metacestodosist írnak le, amelyet proteocephalida galandférgek plerocercoidjai okoznak. Tárgyalják a paraziták