Physiological and morphological characteristics of the rhythmic contractions of the amnion in veiled chameleon (Chamaeleo calyptratus) embryogenesis

Nechaeva, M. V.; Макаренко, И. В.; Tsitrin, E. B.; Zhdanova, Nadezhda P.

doi:10.1016/j.cbpb.2004.09.024

Cited by 14 publications

(7 citation statements)

References 34 publications

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“…Early observers suggested that contractions of the amnion aid development by mixing the amniotic fluid (Romanoff ; Nechaeva et al ) and the susceptibility of the contractions to environmental stimuli have also prompted speculation that the contractions aid in environmental acclimation (Nechaeva et al , ). Our observations suggest that the amniotic contractions also function to facilitate the internalization of residual yolk.…”

Section: Resultsmentioning

confidence: 99%

“…The inner layer of the amnion is composed of ectoderm while the outer layer is mesoderm and contains spindle‐shaped smooth muscle cells. The smooth muscle cells in the amnion are not innervated and contract spontaneously as well as in response to environmental stimuli (Turpaev and Nechaeva ; Nechaeva et al , , ; Nechaeva ). Amniotic motor activity does not occur in mammals and its role in birds and non‐avian reptiles is still unclear (Nechaeva and Turpaev ).…”

Section: Introductionmentioning

confidence: 99%

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Hatching and residual yolk internalization in lizards: evolution, function and fate of the amnion

Pezaro

Doody

Green

et al. 2013

Evolution and Development

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Most egg-laying vertebrates hatch without depleting the entire yolk reserve. The residual yolk is internalized before emergence from the egg is completed and the yolk is subsequently metabolized during early neonatal life. Here we provide the first description of the mechanism of yolk internalization in non-avian reptiles. We describe the hatching of two lizard species (Physignathus lesueurii and Varanus rosenbergii) and provide a step-by-step account of sequence of events leading to yolk internalization and emergence from the egg. We also conducted incubation experiments to determine the cause of failed yolk internalization. Contraction of the ruptured amnion is the mechanism by which the residual yolk is internalized, which provides an explanation for the functional significance of amniotic contractions. Failures of internalization occur when the amount of residual yolk exceeds that which can be enclosed by the ruptured amnion. We conclude that, because of the connections formed between the amnion and both the allantois and chorion, the pipping and retraction of the amnion pulls the chorioallantoic membrane (CAM) off the surface of the eggshell, which impairs the capacity for gas exchange and forces the embryo to breach the eggshell to commence breathing. We further speculate that the loss of amniotic contractions in mammals may indicate an incompatibility of amnion-assisted yolk internalization with viviparity, an evolutionary process that could be tested by examining viviparous squamates.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hatching and residual yolk internalization in lizards: evolution, function and fate of the amnion

Pezaro

Doody

Green

et al. 2013

Evolution and Development

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show abstract

“…Incubation at 30°C is generally stressful given hatchlings are small and juveniles grow slowly (Tables and ). In fact, even slightly higher incubation temperatures (30.5 and 31.5°C) did not produce viable C. calyptratus hatchlings at all (Nechaeva, Makarendo, Tsitrin, & Zhdanova, ). If these suppositions are correct, then females will normally be overrepresented the cohort hatched from relatively large eggs in nature.…”

Section: Discussionmentioning

confidence: 99%

Developmental plasticity in reptiles: Insights into thermal and maternal effects on chameleon phenotypes

Andrews

2018

J Exp Zool Pt A

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Embryonic environments affect a range of phenotypic traits including sex and reproductive success. I determined (1) how the interaction between incubation temperature and egg size affects sex allocation of Chamaeleo calyptratus and (2) how incubation temperature and maternal parent (clutch) affect water uptake by eggs and body size, growth, and climbing speed of hatchlings and juveniles. Eggs from five clutches were exposed to five temperature treatments with clutches replicated within and among treatments. Temperature affected sex, but only when egg size was included as a factor in analyses. At intermediate (28°C) temperatures, daughters were more likely to be produced from large eggs and sons more likely to be produced from small eggs, while at 25 and 30°C, the pattern of sex allocation was reversed. Temperature and clutch affected water uptake and body size. Nonetheless, the direction of temperature and clutch effects on water uptake by eggs and on the size of hatchlings were not the same and the direction of temperature effects on body sizes of hatchlings and juveniles differed as well. Clutch affected hatchling size but not juvenile size and growth rate. Clutch, but not incubation temperature, affected climbing speed, but the fastest hatchlings were not from the same clutches as the fastest juveniles. The independent effects of incubation temperature and clutch indicate that hatchling phenotypes are influenced largely by conditions experienced during incubation, while juvenile phenotypes are influenced largely by conditions experienced in the rearing environment.

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“…However, despite similarity − decrease in HR and increase in BM − the relationship did not exhibit a strict linear dependency. Nonlinear relationship is documented also for chameleon, Chamaeleo calyptratus , during embryogenesis in ovo (Nechaeva et al, 2005).…”

Section: Introductionmentioning

confidence: 96%

Probability that there is a mammalian counterpart of cardiac clock in insects

Kodirov

2022

Arch Insect Biochem Physiol

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Whether or not the hyperpolarization‐activated cyclic nucleotide‐gated nonselective cation channel (HCN or funny current If) is involved in pacemaking − recurrent heartbeat, it is attributed to electrical activities in all excitable cells, including those of invertebrates. In latter group of animals prevailingly the electrical signals and function of heart in terms of chrono‐ and inotropy are elucidated. Although in simpler models including insects experimental outcomes are reproducible and robust, involvement of “cardiac clock” mechanism in pacemaking is not conclusive. In this assay, the mechanisms of heartbeat are synthesized by focused comparisons between insect and mammalian hearts.

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Physiological and morphological characteristics of the rhythmic contractions of the amnion in veiled chameleon (Chamaeleo calyptratus) embryogenesis

Cited by 14 publications

References 34 publications

Hatching and residual yolk internalization in lizards: evolution, function and fate of the amnion

Hatching and residual yolk internalization in lizards: evolution, function and fate of the amnion

Developmental plasticity in reptiles: Insights into thermal and maternal effects on chameleon phenotypes

Probability that there is a mammalian counterpart of cardiac clock in insects

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