Temperature dependent population growth of Gyrodactylus derjavini on rainbow trout, Oncorhynchus mykiss

Abstract

AbstractRainbow trout were experimentally infected with the ectoparasitic monogenean Gyrodactylus derjavini at three temperatures, 5.5°C, 11.6°C and 18.7°C. Subsequently, the infection level was monitored during the following 6 weeks. The population growth was positively correlated with temperature in the initial part of the investigation. At 18.7°C growth of the parasite population was fast reaching a peak abundance within 3 weeks, whereafter the infection level decreased significantly. Peak abundance was recorded in week 5 at 11.6°C. A very slow but steady parasite reproduction was noted at 5.5°C, but no peak abundance was reached within 6 weeks. The decline in parasite population after reaching peak levels is likely to be caused by a host response. The host response is also indicated by the parasites' active selection of particular microhabitats. This anti-monogenean response developed fastest at 18.7°C, more slowly at 11.6°C and was not recorded within 6 weeks at 5.5°C.