A new microsporidium, Potaspora macrobrachium n.sp. infecting the musculature of pond-reared oriental river prawn Macrobrachium nipponense (Decapoda: Palaemonidae).

This paper described a novel microsporidian infection in the pond-reared oriental river prawn Macrobrachium nipponense. A conspicuous symptom of the infection was progressive white opacity associated with the musculature. Although neither bacteria nor viruses were detected in routine diagnostic tests, apparently degenerated microsporidian cells or spores were frequently observed in wet smears of the musculature from diseased prawns. Histological observations also revealed characteristics typical of microsporidian infection throughout the host. Transmission electron microscopy revealed multiple life stages of a microsporidian parasite within the cytoplasm of host muscle cells. In addition, partial small subunit ribosomal RNA (SSU rRNA) gene was obtained by a nested PCR using microsporidian specific primers. A consensus sequence was then deposited in GenBank (accession no. KU307278) and subjected to a general BLASTn search that yielded hits only for microsporidian sequence records. Phylogenetic analysis showed that the isolate was most similar to the fish microsporidian clade containing the genera Kabatana, Microgemma, Potaspora, Spraguea, and Teramicra. The highest sequence identity, 87%, was with Potaspora spp. Based on histological, ultrastructure and molecular phylogenetic data, we erected a new species, Potaspora macrobrachium for the novel microsporidium. The description of microsporidium in this important commercial host was fundamental for future consideration of factors affecting stock health and sustainability.