Ectoparásitos (Crustacea: Branchiura) de Pseudoplatystoma fasciatum (surubí) y P. tigrinum (chuncuina) en planicies de aguas blancas en Bolivia

The ectoparasites of Pseudoplatystoma fasciatum (surubi) and P. tigrinum (chuncuina) from Rio Ichilo, from oxbow lakes in the Rio Ichilo floodplain and from Rio Beni were studied. Sampling was carried out between August 1996 and February 1997 and in August and September 1999. Overall, the ectoparasites from the skin, the branchial cavity, the fins and the gills of 163 P. fasciatum and of 42 P. tigrinum were collected. All fish were found to be infested with ectoparasites. Seven species of Branchiura were recorded, all belonging to the family Argulidae: Argulus juparanaensis, A. pestifer, A. elongatus, A. nattereri, Dolops discoidalis, D. carvalhoi and Dipteropeltis hirundo. The data of 1996-1997 show that P. fasciatum and P. tigrinum harbour the same parasite species, D. hirundo being the only species that was not recorded on the latter, and the infestation levels on both hosts were similar. In general, A. juparanaensis, A. pestifer and D. carvalhoi were the most common species on both fish species. There was a marked difference between the parasite community of P. fasciatum in the Rio Ichilo (dominated by Argulus species) and oxbow lakes (dominated by Dolops carvalhoi). For this fish species, the similarity between ectoparasite communities from different rivers (Ichilo and Beni) was higher than the similarity between ectoparasite communities from different habitats (river channel and oxbow lakes in the Ichilo basin). The relevance of these results for the ecology of the fish host species is discussed.