Morphological and molecular genetic characterization of Kudoa konishiae n. sp. (Myxosporea: Multivalvulida) in the muscle of Japanese Spanish mackerel (Scomberomorus niphonius)

Abstract

The Japanese Spanish mackerel (Scomberomorus niphonius; Perciformes: Scombridae) is widely distributed in the continental shelves of the northwestern Pacific Ocean around Japan, Sea of Japan, and East China Sea. In the present study, small, spindle-shaped myxosporean plasmodia (0.15-0.53 mm by 0.04-0.13 mm) were frequently encountered in the myofiber of trunk muscles of two Japanese Spanish mackerels; one fished in the Sea of Japan off western Japan and the other in the northwestern Pacific Ocean off southern Japan in the autumn of 2016. Isolated myxospores of Kudoa konishiae n. sp. (Myxosporea: Multivalvulida) from these two fish were stellate with six equal shell valves and polar capsules, 8.1-9.7 μm in width, 7.1-8.8 μm in thickness, and 7.1-8.8 μm in length. The polar capsules were teardrop-shaped, 2.7-4.7 μm by 1.2-2.5 μm. The lateral view of spores revealed a drawstring-pouch shape. The nucleotide sequences of the 18S and 28S ribosomal RNA gene (rDNA) were distinct from any recorded species. Phylogenetic trees demonstrated a close relationship of the present new species with Kudoa spp. with stellate spores with five or more shell valves/polar capsules, recorded in scombrid fishes. To clarify the phylogenetic relationships between three closely related species, i.e., Kudoa konishiae n. sp., Kudoa hexapunctata, and Kudoa neothunni, three mitochondrial DNA genes (cytochrome c oxidase subunit 1 gene (cox-1) and the small and large subunits of the ribosomal RNA gene (rns-rnl)) of two isolates of the new species, six isolates of K. hexapunctata, and 13 isolates of K. neothunni were sequenced. The interspecific and intraspecific variations of the newly obtained cox-1 and rns-rnl nucleotide sequences of K. hexapunctata, K. neothunni, and K. konishiae n. sp. were clarified for the first time.

Morphological and Molecular Characteristics of Kudoa viseuensis n. sp. (Myxosporea: Multivalvulida), Found in the Muscle of Batrachoides surinamensis (Teleostei: Batrachoididae) in the Brazilian Amazon Region

“…The new parasite is clearly aligned with other Kudoa species, although this is the first kudoid species from a Brazilian estuary for which molecular data have been obtained. Infection by this new parasite is characterised by the formation of a pseudocyst in the musculature of its host (Yokoyama et al 2012;Kasai et al 2016, Kasai et al 2017Sakai et al 2018). The infection of Kudoa species presents muscle tissue tropism, as observed in the present study, with Kudoa viseuensis n. sp.…”

“…Although the morphology of the spores is essential for the taxonomic classification of species, the phenotypic similarities among kudoid species and the intraspecific variation found in many cases hampers the reliable diagnosis of species based solely on morphology (Urawa et al 2009, Burger and Adlard 2010, Heiniger and Adlard 2012, Heiniger et al 2013. Phylogenetic analyses have provided a better understanding of the diversity and biogeographic relationships among these parasites and their hosts (Urawa et al 2011, Kasai et al 2017, Sakai et al 2018.…”

The Phylogenetic Position of the Enigmatic, Polypodium hydriforme (Cnidaria, Polypodiozoa): Insights from Mitochondrial Genomes

“…Nevertheless, this cutoff threshold seems to be below 10% even in fast-evolving myxozoans. As a case in point, the distance between two Kudoa sequences, which belong to different species, can be as low as 3–5% ( Sakai et al 2018 ; Sakai et al 2019 ). However, it should be noted that in this case, the comparison involves a different COI region than the barcoding one.…”