Arrested embryonic development: a review of strategies to delay hatching in egg-laying reptiles

Abstract

Arrested embryonic development involves the downregulation or cessation of active cell division and metabolic activity, and the capability of an animal to arrest embryonic development results in temporal plasticity of the duration of embryonic period. Arrested embryonic development is an important reproductive strategy for egg-laying animals that provide no parental care after oviposition. In this review, we discuss each type of embryonic developmental arrest used by oviparous reptiles. Environmental pressures that might have directed the evolution of arrest are addressed and we present previously undiscussed environmentally dependent physiological processes that may occur in the egg to bring about arrest. Areas for future research are proposed to clarify how ecology affects the phenotype of developing embryos. We hypothesize that oviparous reptilian mothers are capable of providing their embryos with a level of phenotypic adaptation to local environmental conditions by incorporating maternal factors into the internal environment of the egg that result in different levels of developmental sensitivity to environmental conditions after they are laid.

Effect of rainfall on loggerhead turtle nest temperatures, sand temperatures and hatchling sex

“…2). Eggs cease embryonic diapause once they are laid (Miller 1997, Miller et al 2003, Rafferty & Reina 2012. At our site, sand temperature is near or above the pivotal temperature at the time eggs are laid.…”

Potential sources of intra-population variation in painted turtle (Chrysemys picta) hatchling overwintering strategy

“…The mass and dimensions of the eggs were measured for a long-term study (R. J. Brooks, University of Guelph, and J. D. Litzgus, Laurentian University). Measuring occurred within 24 h post-oviposition, prior to the vitteline membrane adhering to the shell surface (Yntema, 1968;Rafferty and Reina, 2012), ensuring no trauma to developing embryos (Samson et al, 2007).…”

“…In order to examine variation in overwintering strategy, our study had multiple objectives. (1) To explore whether variation in overwintering strategy can be explained by nest environmental factors, concentrating on factors that have been highlighted in previous studies -heat units accumulated over incubation (Storey et al, 1988), vegetative cover, nest oxygen availability (Costanzo et al, 2001;Rafferty and Reina, 2012), oviposition date, and soil moisture (Costanzo et al, 2000;Costanzo et al, 2001), organic content (Costanzo et al, 1998) and texture qualities (Packard and Packard, 1997;Costanzo et al, 1998). (2) To determine whether overwintering strategy benefitted hatchlings.…”

Chelodina oblonga Gray 1841 – Northern Snake-Necked Turtle

“…Nesting underwater and laying multiple clutches, coupled with high levels of inter-and intra-clutch variation in incubation period (Beynon 1991;Kennett et al 1993b), shorter incubation periods with increasing inundation periods, and embryonic estivation (Ewert 1985;Beynon 1991;Rafferty and Reina 2012), are likely adaptations to the highly variable timing of wet season rains and flooding in the wet-dry tropics (Fordham et al 2006b;Shine and Brown 2008). Collectively they allow turtles to: 1) start and complete nesting during periods of high food availability when waterholes are full (and so also to accumulate fat stores for dry season estivation); 2) to avoid the need to find dry nesting sites in mostly flooded habitats that extend for thousands of square kilometers and that may later be flooded; 3) to select nest sites that will be closer to the water's edge when waterholes refill and so increase hatchling survivorship; and 4) to increase the probability that their eggs will complete incubation and be ready to emerge when aquatic habitats re-flood.…”