Do developmental changes in fitness trade-offs
predict how embryos use mechanosensory cues for
FOUILLOUX, C*1; JUNG, J2; OSPINA, AM3; SNYDER, R4; WARKENTIN, KM2
1MHNM, Université Cadi Ayyad, Morocco, 2Boston University, USA, 3IAVH, Colombia, 4John Carroll University, USA
Q1. Do embryos use motion cues, tactile cues, or both?
Q2. If both, are modalities redundant or non-redundant?
Q3. Does cue use change developmentally?
Red-eyed treefrog (Agalychnis callidryas) embryos use physical
disturbance in egg-predator attacks to cue escape-hatching.
Missing predator cues is always costly, but false alarm
costs decrease with development.
E3. We applied tactile stimuli manually directly on embryos or indirectly
on the membrane away from the body.
Young embryos treat
direct contact as more
risky than indirect
contact, but older
embryos do not.
Younger embryos require more indication of risk before
hatching, accumulated over time or across modalities.
Results and Conclusions
and / or
E1-2. We used a playback system to present tactile contact
(rubbing), motion (vibration), or both cues, to embryos.
Escape-hatching response to playbacks. Both modalities elicited hatching. Bimodal stimuli
elicited more hatching than either unimodal stimulus at 4 d embryos, but not at 5 d.
Latency to hatch in playbacks. In both experiments, latency to hatching decreased with age.
in E1 (more ‘scary’ stimulus) younger embryos hatched faster to bimodal cues.
Acknowledgements: This research was supported by the US National Science Foundation,
Boston University, and Smithsonian Tropical Research Institute. Thanks to Team Treefrog for
encouragement and friendship, to Bibiana Rojas and Mohammed Znari for support and guidance,
and to A. callidryas for all the eggs.
E1. ‘scary’ stimulus. E2. moderate stimulus.
0.5 s noise,
1.5 s silence 1–250 Hz
1 s noise, 1 s silence
Latency to hatch in response to localized
tactile stimuli.Both direct and indirect
tactile stimuli elicited hatching. Younger
embryos tolerated a longer period of
indirect stimulation before hatching.
H: Embryos use multiple mechanosensory cues and show
adaptive ontogenetic changes in cue use.
2 TEST AGES: 5 days –Midway through hatching period
4 days –Near onset of predator-induced hatching
Younger embryos treat motion and tactile stimuli as non-
redundant risk cues; for older embryos they are redundant.
Stimulus P = 0.030
Age P = 0.0059 Age P = 0.016
Age P = 2.352 e-16
Stimulus P = 1.96 e-08
aAge P = 0.00015
Stimulus P = 0.0031
Interaction P = 0.0047
Age P: 1.151 e-11
Stimulus P: 0.00025
Interaction P: 0.0001
Conclusion: Embryos use both motion and tactile cues
to assess risk and show adaptive ontogenetic changes
in how they combine information.