Environmental challenges improve resource utilization for asexual reproduction and maintenance in hydra
Experimental Gerontology, 46:10, 794–802 (2011)
Variation in life history can reflect genetic differences, and may be caused by environmental effects on phenotypes. Understanding how these two sources of life history variation interact to express an optimal allocation of resources in a changing environment is central to life history theory. This study addresses variation in the allocation of resources to asexual reproduction and to maintenance of Hydra magnipapillata in relation to differences in temperature and food availability. Hydra is a non-senescent, persistent species with primarily clonal reproduction. We recorded changes in budding rate and mean survival under starvation, which indicate changes in the allocation of resources to asexual reproduction and maintenance. In constant conditions we observed a clear trade-off between asexual reproduction and maintenance, where budding increased linearly with food intake while starvation survival stayed rather constant. In contrast, an environment with fluctuations in temperature or food availability promotes maintenance and increases the survival chances of hydra under starvation. Surprisingly, asexual reproduction also tends to be positively affected by fluctuating environmental conditions, which suggests that in this case there is no clear trade-off between asexual reproduction and maintenance in hydra. Environmental stresses have a beneficial impact on the fitness-related phenotypical traits of the basal metazoan hydra. The results indicate that, if the stress occurs in hormetic doses, variable stressful and fluctuating environments can be salutary for hydra. A closer examination of this dynamic can therefore enable us to develop a deeper understanding of the evolution of aging and longevity.
Keywords: life histories