Food items of Crassostrea rhizophorae (Guilding, 1828) (Bivalvia: Ostreidae) cultivated in a tropical estuary in Northeast Brazil.

The study of the feeding habits of oysters enables us to show aspects of their biology and to recognize anthropogenic changes in the ecosystem. This study analyzed and identified food items in the stomach contents of Crassostrea rhizophorae (Guilding, 1828), obtained in a region of cultivation in a tropical estuary in Northeast Brazil. A total of 210 specimens were collected on a monthly basis between May and November 2005, during low tide. The gastrointestinal tract was removed in the laboratory for quantitative and qualitative analysis. Depending on the degree of repletion, the digestive tubes were classified as “full”, “almost full”, “almost empty” and “empty”. There was a higher incidence of individuals in the “full” stage (57%), indicating the existence of good availability of food. The analysis of stomach contents showed the presence of 97 food items belonging to the groups: Cyanobacteria, Xanthophyta, Bacillariophyta, Dinophyta, Euglenophyta, Chlorophyta, Protozoa, Rotifera, Annelida, Arthropoda, Mollusca, as well as other organisms (fragments of Phytoplankton, Zooplankton and Phanerogamae) and sediments (grains of sand). Bacillariophyta was the dominant group (63%) followed by Chlorophyta (12%). This study showed that C. rhizophorae tends to ingest any microscopic particles carried in suspension in the water irrespective of nutritional value.