No abstract

(Wood land. 1935 ) was lhe only species Ihal presel1led a relalion ship helween lhe illlensily of infeclion and lhe environmenl. ln S. borelli only Cllcllllal/lIs pil/I/oi Travassos. Anigas & Pereira. 1928 rrcsel1led a relalionship wilh lhe env ironmenl. ln lhis case lhe mea n illlensi ly was grea ler in kl1lic env ironmel1l s. The high va lue s of lhe similarily ind ex in lhe lhrec environlllel1ls sludied indicale a considerable homoge neily of lhe endohelminths' species wilh regard 10 P. corruscol/S and S. borelli. This is probably due lO whal occurs wilh environmellls eluring lhe high waler period when lhey are interlinked . The hyelro log ical level was a le ss intluential variahle in endoparasilic infrapopulalions of lhe hOSlS studied . ln P. corruscal/s only lhn:e species. S. spillll/ifera, NO/lli/l/osco/e.r SlIdobi/l/ Woodland . 1934 aml MegalhrloC/(,I'

The life cycle of the digenetic trematode Clinostomum complanatum was studied on the floodplain of the high Parana´river, Brazil. Sampling was done between June 1999 and June 2000. The mollusc Biomphalaria peregrina was the first intermediate host with a prevalence of infection of 0.75%. The fish Loricariichthys platymetopon, Hoplosternum littorale, Parauchenipterus galeatus, Hoplias malabaricus and Loricaria sp. were second intermediate hosts, with the prevalence varying from 2.45% (H. malabaricus) to 60.8% (L. platymetopon). The birds Ardea cocoi, Phalacrocorax brasilianus, Egretta alba and Egretta thula were definitive hosts, with the prevalence ranging between 5.5% (E. thula) and 95% (A. cocoi). The high prevalences in birds, especially in A. cocoi, suggest some kind of mechanism facilitating the predation of infected fish. The importance of the various hosts is discussed, and it is concluded that the floodplain of the high Parana´river has suitable conditions for the maintenance of the life cycle of C. complanatum.

RESUMO.Objetiva-se avaliar o efeito da carga parasitária de Rondonia rondoni sobre o fator de condição de armados, Pterodoras granulosus. Foram necropsiados 51 espécimes de armados, coletados no rio Paraná (Porto Rico/Paraná). Para as análises, utilizaram-se os testes de "t", de Student, para determinar se o comprimento dos hospedeiros machos e fêmeas eram semelhantes; "U", de Mann-Whitney, para determinar o efeito do sexo do hospedeiro na intensidade de infecção da espécie de parasito; "G" Log-likelihood, para determinar o efeito do sexo do hospedeiro na prevalência do parasito; coeficiente de correlação (CC) "r", para determinar a correlação entre o comprimento do hospedeiro e a prevalência de infecção; CC por postos de Spearman "rs", para determinar as possíveis correlações entre a intensidade de infecção e a diversidade parasitária com o comprimento do hospedeiro e para verificar a correlação entre a intensidade parasitária e o fator de condição (K). Os resultados permitiram concluir que, apesar das variações no comprimento entre machos e fêmeas, o sexo não influencia na intensidade e na prevalência de infecção. Porém a intensidade de parasitismo e a prevalência aumentaram com o incremento do comprimento do hospedeiro, e a intensidade parece não afetar o fator de condição de armado, o qual parece estar em equilíbrio com esse parasita nesse ambiente.Palavras-chave: carga parasitária, fator de condição, Pterodoras granulosus, Rondonia rondoni.ABSTRACT. Effect of parasitic load of Rondonia rondoni, Travassos, 1920 (Nematoda, Atrictidae) over the condition factor of thorny catfish Pterodoras granulosus (Valenciennes, 1833) (Pisces, Doradidae). Aiming to evaluate the effect of parasitic load of Rondonia rondoni over the condition factor of Pterodoras granulosus. Fifty one specimens of P. granulosus were collected in Paraná River, (Porto Rico/Paraná). To analyze were used: Student's "t", to determine if length of hosts males and females were similar; Mann-Whitney test "U", to determine the effect of sex of host on the intensity of infestion of the parasite; "G" Log-likelihood test, to determine the effect of sex of the host on the prevalence of parasite; coefficient of correlation "r", to determine the correlation between the length of host and the prevalence of infection; Spearman rank correlation coefficient "rs", to determine as possible correlation's between the intensity of infection and the parasitic diversity with the length of the host, and to examine the correlation between the parasitic intensity and the condition factor (K). Based in this results we conclude, that despite of variations in the length, between males and females, the sex does not influence in the intensity and prevalence of infection. However, the intensity of parasites and the prevalence of R. rondoni increased with the length of host being that, the intensity does not affect the condition factor of Pterodoras granulosus, which mean to be in equilibrium with the parasite in this local.

The prevalence of Clinostomum complanatum Rudolphi, 1814 (Digenea, Clinostomidae) in fishes Loricariichthys platymetopon, Parauchenipterus galeatus and Hoplosternum littorale, which are second intermediate hosts, was studied at the floodplain of the high Paraná River, Brazil. Season (alternation flood-drought), habitat (lentic and semi-lotic), and sex were not related to its prevalence. For L. platymetopon, the immature and smaller fish had the lowest prevalence, whilst the opposite was observed for P. galeatus and H. littorale. This suggests that the probability of being predated is unchanged by parasitism for L. platymetopon; thus, a cumulative effect of repeated infections is observed; for the two other species, the highest parasitised fish may have higher predation mortality rates. While H. littorale is the preferred item in birds' diet, L. platymetopon is the most abundant fish species and has the highest C. complanatum prevalence, which makes it the most likely path of transmission to the bird, the definitive hosts of C. complanatum.