| Various aspects of parasite host relationships (e.g., timing of first infection, distribution within the host population, seasonal sporogenesis, and pathology) between Hoferellus gilsoni (Myxozoa) of the American eel, Anguilla rostrata, were studied in south-central Nova Scotia, Canada. Juvenile and mature eel were sampled over an eight month period from three localities within a single watershed by electro-fishing; elver entering the same watershed were sampled using box type recirculating traps on three separate occasions in May and June. Elver entering the system in May 1998 from sea for the first time were not infected. Elver sampled at the same locality on June 8/98 and June 26/98 were infected, indicating infections were acquired at the river mouth shortly after the upstream migration. Histological examination of infected eel demonstrated synchronised development in each individual host with spore maturation taking 46 to 66 days. Eel held captive at winter temperatures (2–3°C) maintained H. gilsoni infections, suggesting that the parasite can over-winter in the bladder of the eel. In intense infections, pathology included epithelial cell vacuolation and distortion of the bladder wall. Infections of H. gilsoni had no apparent effect on hepatosomatic or body condition indices. H. gilsoni was widespread throughout the Timber/Connaught lake watershed in yellow eel, occurring at three widely separated localities, with varying habitat. Prevalence, which ranged from 27 to 90% in any one sample was not significantly different among the three sites. Significant seasonal variation in prevalence was also observed. In April, prevalence from the three respective sites (Timber, Connaught, and Coolan) was 44%, 36%, and 57% and by July reached 73%, 81%, and 79%. Prevalences remained at these levels until sampling ceased in November. Infections were also observed in migratory silver eel, indicating that H. gilsoni occurs in all phases of the life cycle of American eel. |
