PATHOGENS IN Crassostrea rhizophorae (OSTREIDAE) FROM FARMED AND NATURAL STOCKS IN BAHIA, NORTHEASTERN BRAZIL

Diseases can have a damaging effect on natural and farmed shellfish stocks and, worldwide, there have been many reports on the harm that it cause to the production.  This study investigated pathogens in the oyster Crassostrea rhizophorae from mangrove swamps and from farmed stocks in the coast of Bahia, northeastern Brazil. Samples were taken in 2012 and 2013, being the oysters (n = 330), all measuring from 5 to 7 cm in height, were obtained from a long-line cultivation system and from roots of the red mangrove Rhizophora mangle . The oysters were opened and macroscopically examined and then fixed in Davidson's solution. The tissues were processed by use of conventional histological technique, with staining using Harris’s hematoxylin and eosin. There was no macroscopic evidence of parasites or clinical signs of diseases. Microscopic analysis identified the following pathogens: Rickettsiae -like organisms (RLOs), in the digestive gland, with prevalence (P) of 2 to 6%; Sphenophrya sp. (Ciliophora) (P: 2-6%), in the gills; Nematopsis sp. (Apicomplexa) (P: 44-94%), in several organs, and it was more common in oysters from the mangrove swamp (where this pathogen has a greater chance of completing its life cycle due the presence of crustaceans) than from the farmed stocks (p<0.05 by Chi-square test); Perkinsus sp. (Perkinsozoa) (P: 88-100%), mainly in the stomach and intestine, where it caused changes to the epithelium and hemocytic reaction; Urastoma sp. (Turbellaria) (P: 2-4%), in the gills; Bucephalus sp. (Digenea) (P: 2%), in the digestive gland, mantle and gonad, with parasitic castration; Tylocephalum sp. (Cestoda) (P: 2%), in digestive gland; and an unidentified copepod (P: 2-4%), in the palial cavity, next to the gills. The pathogens were not considered to be important with regard to the health of C. rhizophorae yet, but constant monitoring and studies can promote the sustainability of the oyster farming in the region.