title: Hatching behavior of eastern long-necked turtles (Chelodina longicollis): The influence of asynchronous environments on embryonic heart rate and phenotype.
abstract: Variable temperatures within a nest cause asynchronous development within clutches of freshwater turtle embryos, yet synchronous hatching occurs and is thought to be an important survival strategy for hatchlings. Metabolic compensation and circadian rhythms in heart rates of embryonic turtles indicate the potential of communication between embryos in a nest. Heart rates were used to identify metabolic circadian rhythms in clutches of an Australian freshwater turtle (Chelodina longicollis) and determine whether embryos metabolically compensate and hatch synchronously when incubated in asynchronous environments. The effects of a group environment during incubation on egg development and incubation period were also investigated during the final 3 weeks of development. Chelodina longicollis hatch synchronously and metabolically compensate so that less advanced embryos catch up to more advanced clutch-mates. Heart rates of embryos remained stable from week 4-7 in asynchronous (M=89 bpm) and synchronous (M=92 bpm) groups and declined in the final 2 weeks of incubation (M=72 and 77 bpm). Circadian rhythms were present throughout development and diel heart rates of embryos in asynchronous groups showed less deviation from the mean (M=-0.5 bpm) than synchronous groups (M=-4 bpm). Eggs incubated in groups had a significantly shorter incubation period than eggs incubated individually. Phenotypic traits including size, performance, and growth of all hatchlings were not affected. Egg position within a turtle nest is important for coordinating development throughout incubation and facilitating synchronous hatching.
authors.affiliation: School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 2751, Australia. Electronic address: j.mcglashan@uws.edu.au.
authors.forename: Jessica K
authors.initials: JK
authors.lastname: McGlashan
authors.affiliation: School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 2751, Australia.
authors.forename: Fiona K
authors.initials: FK
authors.lastname: Loudon
authors.affiliation: School of Biological Sciences, The University of Sydney, NSW 2006, Australia.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Thompson
authors.affiliation: School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 2751, Australia.
authors.forename: Ricky-John
authors.initials: RJ
authors.lastname: Spencer
mesh_terms: D000818:Animals; D001315:Australia; D002940:Circadian Rhythm / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000502:physiology*; D004777:Environment; D005260:Female; D005618:Fresh Water; D006339:Heart Rate / Q000502:physiology*; D010063:Ovum / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D014426:Turtles / Q000502:physiology*; D015017:Yolk Sac / Q000196:embryology / Q000502:physiology
keywords: Egg; Embryo; Embryonic communication; Embryonic development; Environmentally cued hatching; Incubation; Metabolic compensation; Nest environment; Synchronous hatching; Turtle