ISSN:
1365-2427
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SUMMARY. 1. Over 13 months, fifty Phagocata vitta were collected from a smalt tributary of the Afon Anafon (Wales) and the occurrence of the ciliate Tetrahymena pyriformis and an unnamed nematode studied.2. During the study, prevalence ranged from 5% to 22% and mean intensity from two to twenty-nine ciliates per infected triclad, whilst relative density never exceeded three per triclad. There was a trend for these values to be highest in summer and lowest in winter, but a significant positive correlation with field temperature was only found for mean intensity. The mean values of mean intensity and relative density were not significantly correlated with triclad size.3. For the nematode, prevalence varied from 2% to 6% and relative density from 0.02 to 0.08 individuals per triclad, whilst mean intensity remained about one per infected triclad. No significant correlations between seasonal fluctuations of any of these values and field temperature were obtained.4. In laboratory experiments lasting 5 weeks, triclads which had been initially fed tubificid worms infected with T. pyriformis and kept in uninfected water had much higher prevalence and mean intensity values than triclads fed uninfected tubiticids and kept in infected water. The main source of infection by the ciliate in the field seems likely to be through the ingestion of infected food. In infected triclads cultured at either 5, 10, 15 or 20°C, prevalence, mean intensity and relative density values increased with rising temperatures, whilst mortality was negligible at the two lowest temperatures and substantial at the two highest. Laboratory findings are related to field events.5. It is concluded that the ciliate and nematode parasites may not cause significant mortality in the fieid population of P. vitta.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2427.1990.tb00311.x
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