Pulses Within the Egg: Uncovering Amnion Rhythms in Chameleon Embryos

This study investigates the amnion rhythmic contractions (ARCs) and heart rate (HR) in veiled chameleon embryos during development. Using non-invasive optical methods, the researchers monitored the frequency and coordination of ARCs and HR under varying temperature conditions (25–30 °C). They found that both ARCs and HR are temperature-dependent and reversible, meaning that changes in ambient temperature directly influenced the frequency of these physiological rhythms, but the effects were not permanent.

The ARCs were observed to begin early in development and persisted throughout embryogenesis. Interestingly, the frequency of ARCs was lower than HR, and the two rhythms were not synchronized, suggesting that ARCs are regulated independently of cardiac activity. The study also noted morphological changes in the amnion tissue, including the development of contractile elements, which may be responsible for generating these rhythmic movements.

The authors propose that ARCs may play a role in fluid circulation within the egg and possibly in mechanical stimulation of the embryo, contributing to normal development. The findings highlight the functional complexity of extraembryonic membranes in reptiles and suggest that veiled chameleons could serve as a valuable model for studying embryonic physiology in oviparous reptiles.

Original Article

Efimova, M. A., Tzareva, N. V., & Veselkin, N. P. (2005). Physiological and morphological characteristics of the rhythmic contractions of the amnion in veiled chameleon (Chamaeleo calyptratus) embryogenesis. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 141(4), 412–420. https://doi.org/10.1016/j.cbpb.2004.12.004