Onset of Sensory Function and Embryonic Discrimination of Ecologically Relevant Cues in Fish

Embryos of oviparous species use a variety of sensory modalities to perceive and respond to environmental cues. However, the timing and mechanisms by which prenatal sensory experiences are acquired, encoded, and translated into lasting behavioral outcomes remain poorly understood. Here, we identified the developmental window of the onset of behavioral responses to olfactory cues in a teleost model of embryonic behavioral development, the fathead minnow (Pimephales promelas), and tested the hypothesis that embryos are sensitive to differences in the information content of cues indicative of predation on eggs vs. free-swimming conspecifics. Assays conducted at regular intervals during embryogenesis showed that a behavioral response to olfactory cues emerges well before hatching, with individuals responding to cues that indicate egg threat. Embryonic exposure to olfactory cues indicative of predation did not significantly alter the timing of emergence from the egg or larval behavior after hatching, but individuals reared in the presence of olfactory cues from injured conspecifics tended to hatch at an earlier stage of development. Our findings suggest that the timing of cue exposure relative to sensory development during embryogenesis may be an important factor contributing to behavioral plasticity in oviparous animals.