Occurrence of Kudoa prunusi and K. lateolabracis (Myxozoa: Myxosporea: Multivalvulida) in Philippine-Sea Japanese parrotfish (Calotomus japonicus)

Kudoa tanakai n. sp. (Myxozoa: Myxosporea: Multivalvulida), a new kudoid species with spheroid myxospores from the scalpel sawtail (Actinopterygii: Prionurus scalparum) from western Japan

We describe a new kudoid species, Kudoa tanakai n. sp., in the scalpel sawfish, Prionurus scalprum (Actinopterygii: Acanthuriformes: Acanthuridae), from the natural water around western Japan. The plasmodia were filamentous, localized in pseudocysts in the myofibers of the trunk muscles. The occurrence of plasmodia in the trunk muscle showed no site preference. Its myxospores were spheroid, measuring 6.6-7.6 (7.0) µm by 5.8-6.9 (6.3) µm in apical view (width) and 5.7-6.6 (6.2) in length (n = 30), with four shell valves and a corresponding number of spheroid polar capsules. Shell valves lacked apical protrusions, but scanning electron microscopy revealed that one of the four shell valves had two semi-lunar flaps at its apical terminus. Nucleotide sequencing of the small and large subunit ribosomal RNA genes of the present isolate showed phylogenetic affinities to kudoid species characterized by spheroid myxospores, such as K. musculoliquefaciens, K. hemiscylli, and K. carcharhini, but was molecularly and morphometrically distinct from these and other kudoid species. For direct comparison, Kudoa hemiscylli was collected from the Pacific spadenose shark, Scoliodon macrorhynchos (Elasmobranchii: Carcharhiniformes: Carcharhinidae), in the South China Sea off Guangdong Province, China, and the myxospore surface of the species was observed using scanning electron microscopy. Our study describes the new host and distribution record of this kudoid species originally described from a variety of elasmobranchs in the Australian Coral Sea.

Descriptions of Three New Species and New Host or Distribution Records of Five Species of the Genus Kudoa (Myxozoa: Myxosporea: Multivalvulida) in Commercial Fishes Collected from South China Sea

PURPOSE

Myxosporeans of the genera Kudoa and Unicapsula (Cnidaria: Myxozoa: Myxosporea: Multivalvulida) may be causative agents of diseases that substantially lower the commercial value of certain marine fishes; thus, species identification is important to effectively manage outbreaks and control infections.

METHODS AND RESULTS

Our investigations of commercial fishes in the families Leiognathidae (three species), Ambassidae (one), Carangidae (five) and Gerreidae (one) in the South China Sea revealed new host records for Kudoa lutjanus (Ambassis martanus, and Gerres limbattus), Kudoa trachuri (Decapterus maruadsi, and Decapterus macrosoma), Kudoa uncinata (Photopectoralis bindus), and Kudoa longichorda (D. macrosoma) and new geographical distribution records for Kudoa javanensis (Alepes djedaba), K. trachuri, and K. longichorda. Moreover, three new Kudoa spp. were described based on detected specimens forming pseudocysts in trunk muscle myofibres. These included Kudoa corniculata n. sp. from Eubleekeria jonesi, and Leiognathus equulus; Kudoa hirsuta n. sp. from Trachurus japonicas, D. maruadsi, and D. macrosoma; and Kudoa parvibulvosa n. sp. from Megalaspis cordyla. To identify these species, their myxospores were morphologically and molecularly characterised based on the small and large subunits of their ribosomal RNA genes.

CONCLUSIONS

In this study, we demonstrated morphometric variations in the myxospores of various species and an atypical K. uncinata morphotype with unequal polar capsules. Hence, taxonomic identification of myxosporeans require molecular characterisation.