Effects of environmental temperature on the susceptibility of Xenopus laevis and X-wittei (Anura) to Protopolystoma xenopodis (Monogenea)

Immune responses in ectothermic vertebrates and the life-processes of their parasites are profoundly linked to ambient temperature, but the functional effect of thermal environment on infectivity and host-specificity in helminths from ectotherms is poorly known. Primary infection establishment of Protopolystoma xenopodis (Monogenea) in compatible hosts (Xenopus laevis,: Anura) is strongly modulated by ambient temperature. Significantly fewer worms survived to the urinary bladder stage at 25degreesC than at 15degreesC (relatively high and low temperatures for this system in nature). Pre-infection exposure of X. laevis to cold (10degreesC) did not significantly affect parasite establishment in the urinary bladder (at 15 or 25degreesC p.i.), nor shorter-term postlarval survival in the kidneys (at 20degreesC p.i.), suggesting that residual immunosuppressive effects on host susceptibility are not important. Low temperatures had no permissive effect on the establishment of P. xenopodis in incompatible hosts (Xenopus wittei). The link between thermal conditions and parasitic infection of ectotherms is discussed.