Reproductive strategies have evolved from a series of trade-offs between cost and timing of reproduction. We tested whether the reproductive effort of female Danube crested newts, Triturus dobrogicus, was environmentally or energetically constrained. We collected females migrating towards the water and kept them separately, with males. Deposited eggs were collected daily during the experiment. More eggs were deposited by older females and by females starting to reproduce earlier. Batches of eggs from females depositing more eggs had a lower hatching success, suggesting decreased viability. Oviposition lasted on average 22.7 days. Female newts showed no loss of weight during this period. At the end of the egg deposition period we injected a subset of females with hormones that triggered the deposition of additional eggs. This suggests that egg deposition in Danube crested newts is environmentally constrained, as females stopped oviposition despite having mature eggs in their ovaries.
We investigated the effect of salinity on larval development and survival rate to metamorphosis in the common spadefoot toad Pelobates fuscus (Laurenti, 1768). Our hypothesis was that higher salinity would decrease tadpole survival rate and body size at metamorphosis, and delay metamorphosis. The response of the tadpoles was evaluated through an experimental design with three salinity treatments of 2, 4, and 8‰ compared to a control (deionized water). Survival varied across the treatments: neither of the tadpoles in 8‰ salinity treatment survived the experiment, nor achieved metamorphosis. Salinity levels of 2 and 4‰ had no significant influence on the mean time to metamorphosis, body mass and SVL at metamorphosis. Our results suggest that P. fuscus tadpoles have a tolerance threshold for brackish water up to 4‰, above which survival is impaired.
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