Transmission of inducible defensive traits across generations and multiple broods in Daphnia

1. Daphnia, a type of global-distributed zooplankton in freshwater ecosystems, can develop a variety of inducible defensive traits when they sense predator kairomone and transmit the predation risk information from females to their offspring. However, limited research focused on how Daphnia females transmit predation pressure information across generations and multiple broods when the mother and the offspring are respectively exposed or not exposed to predation pressure.2. Here we simulated a prolonged predation risk transmission situation in a laboratory experiment, where Daphnia pulex individuals and their offspring were cultured with or without fish kairomone until they reproduce six broods of offspring, to investigate how inducible defensive traits were transmitted across generations and multiple broods in D. pulex.3. Our results showed that (1) D. pulex exposed to fish kairomone could perform typical defensive traits such as reduced body length, increased relative spine length, and increased reproduction; (2) the expression of inducible defensive traits transmitted from the mothers to the offspring were mainly determined by the offspring’s environment rather than the mother’s experience; (3) as the maternal individuals reproduced more broods of offspring, both the inducible defensive traits and the survival probabilities of the offspring showed variations, and the transmission of inducible defensive traits between multiple broods was gradually increased.4. The present study highlights the reversibility and the variations across generations and broods of the transmission of predation risk information via maternal effects, which provides a basis for further understanding of maternal effects in Daphnia. We suggest that it is necessary to simulate the transmission of defensive traits in more complex populations for studying maternal effects.