Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

DISCUSSION Paradilepis scolecina is an extremely common parasite of cormorants of the Lake Balaton region. Cormorants are infected by plerocercus larvae parasitic in fish. It is remarkable that, of the numerous cyprinids indigenous in the lake, only the bream plays an important role in the transmission of infection, and the only other fish species harbouring a plerocercus infection of lower prevalence was the gibel carp (see also Molnár and Székely, 1995). The predominance of infection in the bream seems to be a feature typical of Lake Balaton, as in other habitats other cyprinid species show an infection of similar prevalence as the bream (Kozicka 1971, Scholz 1989). In the fish studied by us, the plerocerci typically occurred in encapsulated form, adhered to the serous membrane of the bile duct or less frequently to the serous membrane of the foregut. The majority of tapeworms belonging to the Dilepididae family develop without a second intermediate host. Most of the species that develop by two intermediate hosts are located in the gut (Valipora) or gallbladder (Gryporhynchus) in non-encapsulated form before they get into the definitive host. The plerocercus larva of P. scolecina markedly differs from the above species in its location. The larvae can always be found in encapsulated form in the abdominal cavity of the second intermediate host, and the capsule surrounding the plerocercus is formed by layers of both parasitic and host origin. As with the larvae of Choanotaenia and Taenia species (Voge 1961, Slais et al. 1971, Slais 1973), the internal hyaline layer is undoubtedly of parasitic origin. Probably the layer consisting of flattened cells and covering the hyaline layer is also generated by the parasite during plerocercus formation. The thinner and thicker layers of connective tissue which sometimes closely adhere to or are separated from the above layer obviously represent parts of the host's serous membrane surrounding the parasite. The pathological significance of P. scolecina plerocerci is not known, although in some cases they are present in the abdominal cavity of breams in large numbers. Their number, however, never reaches that of the Ichthyocotylurus metacercariae found in the same location; thus, P. scolecina plerocerci can at most play a role in aggravating a possible tetracotylosis. Murai, É., Molnár, K. és Gubányi, A.: A Paradilepis scolecina (Rudolphi, 1819) (Cestoda: Dilepididae) aduit és plerocercus formájának előfordulása a Balatonban A Paradilepis scolecina a kormorán gyakori élősködője. A Kis-Balaton (Keszthelyi-öböl) területén vizsgált gazdák 91 %-a volt fertőzött. Lárvaformáit első ízben 1994-ben 299, 15 fajba tartozó hal parazitológiai vizsgálatával sikerült kimutatni. A dévérkeszegek (Abramis brama) 12 %-os fertőzöttsége mellett az ezüstkárászból (Carassius auratus gibelio) sikerült még kimutatni a P. scolecina plerocercus lárvaformáját. A többi vizsgált halfaj nem bizonyult közti gazdának. A szerzők leírták az ezidáig alig ismert plerocercus lárva szövettani felépítését is. REFERENCES Bona, F. V. (1975): Etude critique et taxonomique des Dilepididae Fuhrm., 1907 (Cestoda) parasites des Ciconiiformes. Considérations sur la spécificité et la spéciation. — Monitore Zoologico Italiano, N. S. Monográfia I. 750 p. Czaplinski, B., Sulgostowska, T. and Czaplinska, D. (1992): Catalogus faunae parasiticae Poloniae. IV. —Towarzystwo Parasitologiczne, Warszawa, 186 pp.