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Data from: To hatch and hatch not: Rejecting the hypothesis that heterochrony in vestibular mechanosensing explains poor escape-hatching success of Agalychnis spurrelli in snake attacks compared with its congener A. callidryas

Güell, Brandon A.1; Warkentin, Karen M.1

Published Dec 13, 2023 on Dryad. https://doi.org/10.5061/dryad.cnp5hqc8x

Data files

Dec 13, 2023 version files 347.47 KB

Abstract

Phyllomedusid treefrogs hatch prematurely to escape egg predation, but escape success varies among species. During spontaneous hatching of Agalychnis spurrelli, snake attacks elicited 55% less escape-hatching than did attacks on less developed A. callidryas. Agalychnis callidryas use their vestibular system and, secondarily, their lateral line to sense physical disturbances that cue hatching. Since A. spurrelli develop faster, we hypothesized that heterochronic shifts in the onset timing of vestibular mechanosensory function, relative to hatching ability, might explain their lower escape response to mechanosensory cues. To test this, we compared the onset timing of hypoxia- and mechanosensory-cued hatching (MCH) and vestibular mechanosensory function in developmental series of A. spurrelli and A. callidryas embryos. Across species, most sibships began responding to each cue at the same developmental stage. MCH onset in A. spurrelli was associated with vestibular function onset, as indicated by measurements of the vestibulo-ocular reflex (VOR). Indeed, the first A. spurrelli embryos to show MCH had VOR amplitudes similar to those previously found for A. callidryas at the onset of MCH.  These results indicate that low escape-hatching success in A. spurrelli is not caused by a relative delay in the onset of vestibular mechanosensory function, rejecting our initial hypothesis; the developmental timing of vestibular mechanosensing and its role in predator-induced hatching appears conserved. Our observations of both higher escape success of larger clutches in snake attacks and hatching complications in flooded A. spurrelli suggest, instead, that differences in egg capsule and clutch structure may contribute to species differences in escape-hatching success.