Effects of temperature on azamethiphos sensitivity profile of Caligus rogercresseyi

It is well known that the biology of Caligus rogercresseyi is strongly affected by environmental conditions such as temperature. However, little is known if these variables can affect antiparasitic sensitivity. In this context, the aim of the study was to determine how temperature and light can induce changes in the parasite sensitivity profile to azamethiphos. Temperatures of 9, 12, 15, and 17 °C and two light conditions were evaluated through sensitivity evaluation in vitro bioassays. Parasites were exposed to an azamethiphos concentration gradient of 0, 3, 10, 30, 100, and 300 ppb. A range of temperature between 12 °C and 15 °C did not significantly change the sensitivity profile of the parasite. Moreover, light conditions did not induce significant changes in the sensitivity profile either. However, the temperature of 9 °C induced higher effective concentrations (EC50) than the rest of the temperatures, but also lower affectation and mortality of the parasite. This evidence suggested that sensitivity to azamethiphos decreases with temperature, regardless of the light conditions. These results are considered relevant since strong variations of environmental conditions (like temperature) among seasons and geographical areas could impact salmon–parasite interactions, but also the effectiveness of the treatments applied in the salmon industry. Even more, in a climate change context, for which temperature is considered one of the main variables, it is expected that important changes occur in the biology, metabolism, and population dynamics of parasites, fish, and marine animals, being these changes a matter of concern in the future sustainability of aquaculture.