New records of three commercial fish hosts for two Unicapsula spp. and Kudoa megacapsula (Myxozoa: Myxosporea: Multivalvulida).

ABSTRACT

Infections caused by multivalvulid myxosporeans belonging to genera Unicapsula and Kudoa (Cnidaria Myxozoa) occasionally affect commercial marine fish species. Postmortem myoliquefaction caused by a variety of Kudoa spp., including K. thyrsites, and unsightly cyst or pseudocyst formation, caused by K. amamiensis, U. muscularis, and other kudoid species, negatively affect commercial values of fillets. However, multivalvulid infections are often latent and imperceptible in the market. Biodiversity, host range, and epidemiology remain to be explored. Here, myxosporean infection was detected in four commercial fish species from southern China, using morphological and molecular analyses. Three Unicapsula spp. (U. pyramidata in Nemipterus japonicus; U. pflugfelderi in Dentex angolensis transported from the Eastern Central Atlantic Ocean, off West African coast; and U. aequilobata in Decapterus macarellus) and Kudoa megacapsula in Nemipterus virgatus were observed to form pseudocysts in the myofibers of the host trunk muscles. All fish hosts identified here, except for U. pyramidata, are new records. Kudoa megacapsula was morphologically characterized by gigantic, cruciform myxospores with four wing-like shell valves morphologically comparable to previous Japanese records of the same species in aquaculture facilities, acquiring fly from China or Korea (Sphyraena pinguis and Seriola quinqueradiata, respectively). Molecular analyses established the conspecificity of the present Chinese isolate with previously recorded Japanese isolates. To our knowledge, for the first time, a partial large subunit ribosomal RNA gene sequence of K. megacapsula was obtained, showing close phylogenetic relationships with Kudoa spp. harboring cruciform myxospores, such as K. thyrsites, K. gunterae, K. whippsi, and K. lateolabracis.