Behaviour 2019
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Multimodal mechanosensing enables treefrog embryos  to escape egg-predators
Julie Jung1, Shirley J. Serrano-Rojas2, Karen M. Warkentin1,2. 1Boston University, Boston, MA, United States; 2Smithsonian Tropical Research Institute, Gamboa, Panama, Panama

Arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, hatch to escape predation, cued by physical disturbance in snake attacks. When otoconial organs in the vestibular system begin to function, this hatching response strengthens, but its earlier occurrence indicates another mechanosensor must also contribute. We assessed the role of lateral line neuromasts. Prior to vestibular function, ablating neuromast function with gentamicin effectively ablated the hatching response to manual egg-jiggling, a complex simulated attack cue, revealing that neuromasts mediate very early escape-hatching. Vestibular function onset increased hatching regardless of neuromast function, indicating young embryos use multiple sensory systems to detect egg-jiggling cues. Gentamicin did not affect the hatching response of older embryos, but did slow their hatching decision. However, we found no effect of gentamicin on hatching response or timing in vibration playbacks, with a simpler motion-only cue. Our findings provide insight into the functional roles of two developing mechanosensory systems prior to hatching and reveal new possibilities for exploring embryonic sensory perception across taxa.