Morphological and molecular genetic characterization of two Kudoa spp., k. musculoliquefaciens, and k. pleurogrammi n. sp. (myxosporea: multivalvulida), causing myoliquefaction Of commercial marine fish
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Date
2016-01
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
Genetic characterization of myxosporean species,
including members of the genus Kudoa, has advanced dramat-
ically throughout the last decade. This is in stark contrast to
those species described further back in time. Kudoa
musculoliquefaciens described from the jellied muscle of
swordfish, Xiphias gladius, in the western Pacific Ocean off
the Sanriku Coast, northern Japan, is one such species. In the
present study, multiple pseudocysts (0.66–1.35 mm average
length and 0.06–0.10 mm average width) containing
K. musculoliquefaciens spores were collected from three host
groups: muscle blocks of swordfish caught in the western
Pacific Ocean off the Sanriku Coast, or the northern Indian
Ocean, and Indo-Pacific sailfish, Istiophorus platypterus, in
the western Pacific Ocean off Kochi, western Japan.
Subspherical K. musculoliquefaciens spores, 8.0–10.3 μm in
width, 7.3–10.0 μm in thickness, 6.4–7.9 μm in sutural thick-
ness, and 5.5–8.1 μm in length, had four subspherical polar
capsules, 2.8–4.0 μm in length by 2.2–3.2 μm in width. The
kudoid spores found in the different host groups showed mor-
phometric variations to some extent but had essentially iden-
tical nucleotide sequences of the ribosomal RNA gene
(rDNA), closest to those of Kudoa hemiscylli or Kudoa carcharhini recorded from elasmobranchs in the
Indo-Pacific Ocean. Another kudoid species, Kudoa pleurogrammi n. sp., was recorded from the jellied and normal
muscles of Atka mackerel, Pleurogrammus monopterygius
and Pleurogrammus azonus, fished in the northern Pacific
Ocean or northern Sea of Japan. Subquadrate spores found
in round-ended pseudocysts (1.15–3.85 mm in length and
0.11–0.26 mm in width) in myofibers were 8.2–9.1 μm in
width, 7.1–8.2 μm in thickness, 5.4–7.7 μm in sutural thick-
ness, and 5.6–6.8 μm in length, with four ovoid polar cap-
sules, 2.7–2.9 μm in length by 1.4–2.0 μm in width. Kudoid
spores from both jellied and normal muscles or different host
fish species had identical 18S or 28S rDNA nucleotide se-
quences. Thus, molecular genetic characterization of kudoid
species with the potential to induce post-mortem
myoliquefaction will facilitate the reliable and specific identi-
fication of myxosporeans found in either jellied or normal
muscles of important commercial fish
Description
Journal Article
Keywords
Kudoa musculoliquefaciens, Kudoa pleurogrammi n. sp, Multivalvulida, Xiphias gladius, Pleurogrammus spp, Stiophorus platypterus