Infection levels of proteocephalidean cestodes in Cichla piquiti (Osteichthyes: Cichlidae) of the Volta Grande Reservoir, Minas Gerais, Brazil, relative to host body weight and gender.

Abstract

We evaluated the relationship between infection by proteocephalid cestodes and the sex and weight classes of tucunar&#xe9; (Cichla piquiti) captured between August 1999 and June 2001 in the Volta Grande Reservoir, Minas Gerais, Brazil. A total of 96 fish, 75.9&#xa0;&#xb1;&#xa0;9.3% males and 88.9&#xa0;&#xb1;&#xa0;6.4% females, were parasitized by Proteocephalus macrophallus and P. microscopicus, with total mean intensities of 76.6&#xa0;&#xb1;&#xa0;23.9 and 145.2&#xa0;&#xb1;&#xa0;36.7, respectively, during this period. In the majority of the months analysed, males showed 71.4-100% prevalence of parasitism and females 80-100%. Although there was no significant difference, females showed a higher mean intensity of infection (145.2&#xa0;&#xb1;&#xa0;36.7) than males (76.6&#xa0;&#xb1;&#xa0;23.9). Fish weighing 300-800&#xa0;g showed a higher mean abundance of parasites (P&#xa0;<&#xa0;0.05) compared with the biggest specimens weighing 801-2750&#xa0;g. Analysing both males and females together, the greatest mean intensities of infection were found in October and December (P&#xa0;<&#xa0;0.05) independent of the year, which coincides with the months of highest rainfall. These results show that fish living in reservoirs may be more susceptible to intermediate hosts than those that live in rivers.