Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)
RESULTS Adults of P. scolecina were detected in 41 out of the 45 cormorants examined. In the majority of these birds, specimens with a complete strobila occurred, but some specimens had only a few segments on the scolex. The average number of helminths per bird was 47 (extreme values: 20 and 550). The shape and size of the hooks located on the helminths' rostellum corresponded to those reported for P. scolecina (Fig. 1A), and proved to be identical with the corresponding formations of plerocerci collected from fishes (Fig. IB). Of the cyprinids examined, only the bream and the gibel carp were found to have P. scolecina infection. In Lake Balaton breams, P. scolecina plerocerci were first detected in 1994, when the occurrence of larvae was recorded in the abdominal cavity of 13 out of the 60 three- to five-summer fish examined. At that time, 1 out of the 19 gibel carp proved to be infected (Molnár and Székely, 1995). Thirteen out of 48 and 13 out of 53 breams were found to harbour plerocerci in 1995 and 1996, respectively. The parasite could not be detected in any of the 9 gibel carp specimens examined in these years. No Paradilepis infection was found in the 164 fish specimens belonging to other cyprinid species. In each infected fish 2-25 parasite specimens were present, in most cases adhering to the serous membrane of the duct connecting the gallbladder with the gut but often also on the serous membrane of other gut portions. In these fish, the hardly observable plerocerci very often occurred together with the much more conspicuous Tetracotyle fluke larvae as a combined infection. The plerocerci adhering to the serous membrane of the intestine were easily detectable in histological preparations. The plerocercus was consistently located within a capsule (Figs ÎC-E) which contained the helminth surrounded by fluid. That capsule containing the plerocercus was often connected with the serous membrane by host tissue consisting of a few cell rows (Fig. 1C) while at other times the wall of the capsule was embedded in the serous membrane (Fig. ID). In the majority of cases the cyst wall and the bile duct was c )imected by a serous membrane layer adhering to the two opposite poles of the cyst (Figs 1E-F). In the larva bordered by a thin larval tegument the suckers and the rostellum were clearly retracted (Figs 1D-E). Although in some cases the parasite closely adhered to the wall of the capsule (Fig. 1D), in our preparations we could not unambiguously determine whether the larva was connected to the wall at a certain point or was floating freely in the lumen of the capsule. Histologically, the capsule consists of three distinct layers. The internal structureless hyaline layer is of uneven thickness (Fig. IF), reaching 10pm in some places while becoming expressly thin elsewhere. From the outside, the hyaline layer is covered by a 6-8 pm thick cellular layer which is presumably of parasitic origin (Fig. 1F) and consists of a fibrillated tissue containing markedly flattened nuclei. In some cases the same layer contains also round nuclei. This capsule of parasitic origin is consistently covered by a tissue capsule of host origin, detached from the serous membrane, which often completely extenuates (Fig. 1C) while at other times forms a multilayered wall (Fig. IF).