More about the biodiversity of parasites in Vietnam: a first report of microsporidia (opistosporidia, microsporidia) in coral fish

Abstract

This is the first report of microsporidia infection in marine fish from Vietnam. Microsporidia (Opistosporidia, Microsporidia) were identified in 4 species of coral fish Cheilinus chlorourus (Labridae), Abudefduf bengalensis (Pomacentridae), Pomacentrus brachialis (Pomacentridae), Atule mate (Carangidae) from Nha Trang Bay (East Sea), Khanh Hoa Province, Vietnam, in 2018 and 2019. Dry smears of blood, intestine and liver were stained using the Giemsa method. Gut and liver were fixed in Bouin’s fluid, processed for routine paraffin infiltration, and sections were stained with Hematoxylin and Eosin. Strong microsporidia infections were the same for all three species revealed in 1 of every 6 fish samples (prevalence 16.7%) of C. chlorourus, A. bengalensis, and P. brachialis. In C. chlorourus there were meronts, sporogonial plasmodia, and sporoblasts found in all layers of intestine (enterocytes, myocytes, mesotheliocytes), pancreas and liver. In A. bengalensis parasites were found in enterocytes of the small intestine and liver. In P. brachialis meronts, sporogonial plasmodia and sporoblasts were in enterocytes of the small intestine. Intracellular parasites are located in parasitophorous vacuoles covered with additional shell, which appeared to be in the process of forming xenoma. Microsporidia infection was revealed in 1 of 31 fish samples of A. mate (prevalence 3 %). Up to 30 of round and oval white xenomas were detected in the gills of fresh samples by microscopy. We tentatively assign the microsporidia to Glugeidae due to host affiliation (fish), localization (digestive system) and xenoma formation. They differ from Pleistophoridae by localization in non-muscular cells.