Abstract
In the southeastern USA, the channel catfish Ictalurus punctatus is a host to at least eight different species of myxozoan parasites belonging to the genus Henneguya, four of which have been characterized molecularly using sequencing of the small subunit ribosomal RNA (SSU rRNA) gene. However, only two of these have confirmed life cycles that involve the oligochaete Dero digitata as the definitive host. During a health screening of farm-raised channel catfish, several fish presented with deformed primary lamellae. Lamellae harbored large, nodular, white pseudocysts 1.25 mm in diameter, and upon rupturing, these pseudocysts released Henneguya myxospores, with a typical lanceolate-shaped spore body, measuring 17.1 ± 1.0 μm (mean ± SD; range = 15.0–19.3 μm) in length and 4.8 ± 0.4 μm (3.7–5.6 μm) in width. Pyriform-shaped polar capsules were 5.8 ± 0.3 μm in length (5.1–6.4 μm) and 1.7 ± 0.1 μm (1.4–1.9 μm) in width. The two caudal processes were 40.0 ± 5.1 μm in length (29.5–50.0 μm) with a spore length of 57.2 ± 4.7 (46.8–66.8 μm). The contiguous SSU rRNA gene sequence obtained from myxospores of five excised cysts did not match any Henneguya sp. in GenBank. The greatest sequence homology (91 % over 1,900 bp) was with Henneguya pellis, associated with blister-like lesions on the skin of blue catfish Ictalurus furcatus. Based on the unique combination of pseudocyst and myxospore morphology, tissue location, host, and SSU rRNA gene sequence data, we report this isolate to be a previously unreported species, Henneguya bulbosus sp. nov.
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Acknowledgments
We would like to thank Neely Alberson, Sarah Stonefield, and Ethan Woodyard for their assistance in parasite isolation and imaging. This research was supported by the Mississippi State University College of Veterinary Medicine, the Mississippi Agricultural and Forestry Experiment Station, and the USDA-ARS Catfish Health Initiative (CRIS 6402-31320-002-02). This is MAFES publication number: J-12552.
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Rosser, T.G., Griffin, M.J., Quiniou, S.M.A. et al. 18S rRNA gene sequencing identifies a novel species of Henneguya parasitizing the gills of the channel catfish (Ictaluridae). Parasitol Res 113, 4651–4658 (2014). https://doi.org/10.1007/s00436-014-4156-6
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DOI: https://doi.org/10.1007/s00436-014-4156-6