A parasitological survey of slipper-cupped oysters (Crassostrea iredalei, Faustino, 1932) in the Philippines

Abstract

This paper describes the first screening in the Philippines of slipper-cupped oysters (Crassostrea iredalei) for the presence of parasites. Slipper-cupped oysters were sampled at 2 sites in Ivisan, Capiz, from September to December 2007. Macroscopical and histological analyses were carried out in oyster tissues. Histological examination showed gregarine protozoan Nematopsis sp. as the most prevalent parasite (71.33% and 65.0%) at 2 sites with a moderate intensity of infection. Tylocephalum sp. cestode was found in the connective tissue around the digestive gland, with a prevalence of 60% and 52.3% in 2 sites, with a moderate intensity of infection. Digenean trematodes had a 37.80% prevalence at site 1 and a 22.45% prevalence at site 2. Ciliates were also observed with a prevalence of 18.75% (site 1) and 13% (site 2). The observed infection of oysters had no apparent effect on oyster production at these sites maybe due to low infestation levels or to the fact that the parasites have no pathological effect.