Gross signs and histopathology of Ostrea puelchana infected by a Bonamia exitiosa-like parasite (Haplosporidia).

Haplosporidian microcells belonging to the genus Bonamia parasitise various species of oysters around the world. In Argentina, Bonamia sp. was the causative agent of mass mortality among Ostrea puelchana cultured in San Antonio Bay (San Matías Gulf), and it was detected in natural beds inside San Matías Gulf. In order to describe the gross and histopathological signs caused by Bonamia sp. in O. puelchana, cultured and wild oysters were sampled and analysed by traditional techniques including heart imprints and histology. Cells of Bonamia sp. were observed in connective tissue, free or within haemocytes, in gills and around the digestive gland, stomach, intestine and gonad. Gross signs, histopathological alterations in O. puelchana, and Bonamia sp. cytological morphology resemble those reported for B. exitiosa. However, I propose to treat the Argentinean species as B. exitiosa-like until more molecular and ultrastructural studies are conducted to determine the correct taxonomy.