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Mass mortality associated with a Sphaerospora ‐like myxosporidean infestation in juvenile cobia, Rachycentron canadum (L.), marine cage cultured in Taiwan
Author(s) -
Chen SC,
Kou RJ,
Wu CT,
Wang PC,
Su FZ
Publication year - 2001
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1046/j.1365-2761.2001.00287.x
Subject(s) - biology , parasite hosting , ultrastructure , anatomy , lumen (anatomy) , juvenile , microbiology and biotechnology , zoology , pathology , ecology , medicine , world wide web , computer science
Cultured cobia, Rachycentron canadum , of 45–80 g exhibited anaemia and ascites, and a mottled red and grey, extremely enlarged kidney with cream‐coloured patches or spherical nodules. Cumulative mortality was about 90% within 1 month. Extrasporogonic or sporogonic stages of a myxosporean appeared in the blood, glomerulus, renal tubules and renal interstitium. The renal tubules were the main target tissue of the parasite and were completely occluded by sporogonic pseudoplasmodia at various degrees of maturity. Many sporogonic stages were attached to the brush border of the epithelium of the renal tubules. Mature spores were seen in the lumen of the tubules. They were elongated or spherical with numerous refractile granules in the cytoplasm. The polar filament formed 3–5 coils. No bacteria or viruses were isolated from the diseased fish. Based on the results of microbiological, histopathological and electron microscopical examinations, the cobia disease was believed to be caused by a Sphaerospora ‐like myxosporean. This is the first report of a myxosporean in cobia in aquaculture.