Desiccation plasticity and diapause in the Argentinian pearlfishAustrolebias bellottii

Background The annual life history strategy with diapauses evolved repeatedly in killifish. To understand their and to characterize their variation between species, patterns of desiccation plasticity seem central. Plasticity might have played a role in the origin of these developmental arrests, when annual fish evolved from non-annual ones. The consequences of desiccation on survival and developmental rates of embryos of annual fish are poorly known. Using detailed demographic modelling of embryonal life histories, we investigate plasticity for desiccation in the Argentinian pearlfish Austrolebias bellottii . The treatment protocol contains changing environmental conditions with successive phases of mild desiccation and rewetting. Results We observed no clear diapause II and thus no increased incidence caused by mild and prolonged desiccation. Embryos arrest development in the pre-hatching stage (DIII) or in the dispersed cell phase (DI) irrespective of environmental conditions. There are limited effects of desiccation on survival, limited developmental delays and an acceleration of development into the pre-hatching stage. We found significant parental variance components on developmental rates, but hardly any effect of parental age. Hatching probabilities increased with age, when embryos had been in air at 100% RH and increased further when embryos were rewetted a second time after a two month interval. Conclusions Mild desiccation and rewetting affect survival, rates of development and hatching probability, but not the fractions of embryos that arrest development in particular stages. We can conclude that the incidences of diapause have become relatively independent of the occurrence of mild desiccation, as if they have become assimilated. In contrast to the responses to mild desiccation observed in the non-annual rivulids, Austrolebias accelerates development into the pre-hatching stage.