Differentiation of two locally sympatric Protopolystoma (Monogenea : Polystomatidae) species by temperature-dependent larval development and survival

The developmental response of egg stages to different environmental tempera ture regimes was studied in Protopolystoma xenopodis and Protopolystoma ori entalis (Munogenea: Polystomatidae) isolates from southern Africa. Eggs fai led to develop at 10 degrees, whilst at 15 degreesC only P. xenopodis compl eted larval development, hatching 49-88 days post-collection. Respective ha tching windows were 26-34 (P. xenopodis) and 37-49 (P. orientalis) days at 20 degreesC. and 18-26 and 27-37 days at 25 degreesC. Continuous maintenanc e at 30 degreesC was lethal for eggs of both species. There were no consist ent interspecific differences in the response of egg stages to low and high temperature shocks during early embryonic development. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All right s reserved.