Digeneos parásitos de Porichthys porosissimus (Teleostei: Batrachoididae) en el estuario de Bahía Blanca

Abstract

En el presente estudio se eligió como modelo de hospedador a Porichthys porosissimus por ser habitante permanente del estuario de Bahía Blanca. Los objetivos fueron: describir las especies de digeneos y analizar cambios respecto de reportes previos. Se examinaron 200 ejemplares de P. porosissimus. El análisis de los datos se realizó utilizando estimadores poblacionales de rutina y tests no paramétricos. Las especies registradas fueron: Aponurus laguncula Looss, 1907, Lecithochirium cfr. microstomum, Parahemiurus cfr. merus, Stomachicola sp., Opecoeloides feliciae Martorelli, 1992 y un espécimen no determinado perteneciente a la familia Bucephalidae. La especie más prevalente, abundante, dominante y única componente de la comunidad de digeneos fue A. laguncula. El pez estudiado permanece asociado al sedimento limoarenoso, en el cual depositan elementos contaminantes de origen antropogénico. Las poblaciones de digeneos adultos y metacercarias en los peces muestran tendencias a incrementar en medios eutrofizados y sometidos a descargas de contaminantes urbanos. Tal es la principal presión de impacto ambiental que viene experimentando el estuario de Bahía Blanca. De aquí que la misma puede explicar las variaciones temporales en la abundancia y riqueza específica de digeneos registrada en el presente análisis.

The aims of the present study were to describe the morphology of the digenean parasites recorded in P. porosissimus and to analyse the temporary fluctuations in their communities. Two hundred hosts were examined between May 2008 and April 2011. The parasites were extracted from the stomachs of fish. The data analysis was performed using non-parametric tests. Six species of digenean parasites were recorded: Aponurus laguncula Looss, 1907, Lecithochirium cfr. microstomum, Parahemiurus cfr. merus, Stomachicola sp., Opecoeloides feliciae Martorelli, 1992 and an unidentified specimen belonging to the family Bucephalidae. The most prevalent, abundant, dominant and unique species of the digenean community was A. laguncula. Its abundance did not reflect any significant differences in respect to the host’s sex. There was no correlation between the parasitic abundance of this species and the condition factor of the fish. Although the life cycle of this species has not yet been elucidated, it appears to colonize the host via a trophic pathway. Three of the six species recorded were immature worms reflecting that conditions in the stomach of P. porosissimus were unsuitable for the reproductive stage. The present study showed an increase in the digenean species richness as well as in the parasitic abundances of P. porosissimus in respect to previous surveys carried out from 1997. The fish is a permanent resident of the Bahía Blanca estuary which lives associated with the silty-sandy sediments containing various anthropogenic pollutants It is known that both adult digeneans and metacercariae from fish tend to increase in eutrophic environments, e.g. untreated sewage effluent in coastal environments. This environmental impact may partly explain the increasing trend in the abundance and species richness of the digeneans observed.