EFFECT OF TEMPERATURE ON SURVIVAL AND INFECTIVITY OF ECHINOSTOMA-TRIVOLVIS CERCARIAE - A TEST OF THE ENERGY LIMITATION HYPOTHESIS

Trematode cercariae typically become unable to successfully infect a h ost many hours before they die. We examined the hypothesis that both t ime to 50% mortality and time to loss of infective capacity are contro lled to the same degree by rates of energy expenditure, by determining the relative effects of temperature on both parameters. Infective cap acity was assessed by exposing Echinostoma trivolvis cercariae of diff erent ages to a suitable second intermediate host (the gastropod Biomp halaria glabrata) and counting 1-2 days later the number of metacercar ial cysts formed. Temperature had a remarkably similar effect on time to 50% mortality and loss of infective capacity, supporting the hypoth esis that both absolute and functional cercarial life-spans are limite d by the rates at which energy stores are utilized.