Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli (Eoacanthocephala, Neoechinorhynchidae) of Pimelodus maculatus Lacépède (Siluroidei, Pimelodidae) of the São Francisco River, Brazil

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli, 1998, in Pimelodus maculatus Lacépède, 1803 collected in the São Francisco river during periods of drought (July 1995 and 1996) and floodings (January 1996 and 1997) of this river basin are provided. In tropical regions where the amount of rainfall alters the hydrological regimen of limnological systems water temperature has not had an important role in infections of N. pimelodi in P. maculatus. Prevalence was somewhat higher during drought periods. Intensity of infection varied slightly between collecting periods. Mature male and female acanthocephalans were present in all periods. Females were predominant. Mature females were present in higher numbers during flooding periods with a corresponding decrease in juvenile acanthocephalans. Recruitment and constant losses of N. pimelodi seem to be controlled by transmission mechanisms independently of density. Mechanisms may consist of infected prey availability (potential intermediate hosts) and changes of preferred alimentary items in the diets of juvenile and mature P. maculatus