Occurrence of two myxosporean species, Myxobolus hakyi sp. n. and Hoferellus pulvinatus sp. n., in Pangasianodon hypophthalmus fry imported from Thailand to Europe as ornamental fish

Abstract

Fingerlings of the sutchi catfish Pangasianodon hypophthalmus, a favorite food fish in South Asia, is regularly imported by European fish traders and sold in pet fish shops. In shipments from Thailand, a skin and a kidney infection of this fish caused by myxosporean parasites was found both in Hungary and Russia. In the skin of the fish, small millet-sized nodules containing great numbers of a Myxobolus species were found, while in the renal glomeruli, spores and sporogonic stages of a Hoferellus species developed. The skin-infecting species described as Myxobolus hakyi sp. n. had 15.9 x 6.6-microm-sized spores with elongated polar capsules, while the renal species described as Hoferellus pulvinatus sp. n. had roundish spores with a size of 6.5 x 5.0 microm and had a characteristic pillow-like structure at its posterior end. Besides morphology, histology of infection and 18S rDNA sequences were studied.