Hatching responses of temporary pool invertebrates to signals of environmental quality

Many temporary pool invertebrates survive dry periods as diapausing eggs. Theory predicts that the proportion of diapausing eggs that hatch when the pool fills with water should vary with signals of likely reproductive success, if such signals are available. Reproductive success in temporary pool invertebrates is influenced by the presence of predators and desiccation. We studied hatching responses of temporary pool invertebrates to the presence of fire salamanders (Salamandra salamandra L., an important predator in temporary pools), and to manipulations of nutrients. Nutrient manipulations may mimic the increase in conductivity associated with high evaporation and risk of desiccation, but might also affect food availability or modify signals associated with the presence of Salamandra. Fewer eggs of the conchostracan Cyzicus sp. hatched in the presence of Salamandra, and in pools to which nutrients had been added. Other taxa (bdelloid rotifers and chydorids) did not show unambiguous hatching responses to the presence of Salamandra or nutrients. We discuss these results in the light of simple models for optimal hatching fractions. Large crustaceans such as Cyzicus are particularly likely to show strong hatching responses to signals of environmental quality. However, we also expect to find such responses in many other crustaceans.