Embryonic responses to variation in oviductal oxygen in the lizard Sceloporus undulatus from New Jersey and South Carolina, USA

Abstract

Viviparity in reptiles is hypothesized to evolve in cold climates at high latitudes and high elevations through selection for progressively longer periods of egg retention. Oxygen consumption of embryos increases during development and therefore longer periods of egg retention should be associated with maternal or embryonic features that enhance embryonic oxygen availability. We tested the hypotheses that embryos of the oviparous lizard Sceloporus undulatus from a high-latitude population in New Jersey are oviposited at more advanced developmental stages and have a higher growth rate at low oxygen partial pressures ( p O 2 ) than embryos from a low-latitude population in South Carolina. These hypotheses were rejected; embryos from the two populations did not differ in embryonic stage at oviposition, survival, rate of differentiation or growth in mass when incubated under simulated in utero conditions at low oxygen concentrations. We also estimated the effective p O 2 experienced by lizard embryos in utero . At an effective p O 2 of 8.6 kPa (9% O 2 ), development of S. undulatus embryos is arrested at Dufaure and Hubert stage 30 and at a dry mass of 0.8 mg. Physiological and morphological features of gravid females, embryos, or both, that facilitate oxygen uptake for developing embryos appear to be a critical early step during the evolution of reptilian viviparity.

Incubation temperature and phenotypic traits of Sceloporus undulatus: implications for the northern limits of distribution

“…The capacity of gravid females of S. undulatus to retain eggs, however, does not appear to vary among populations in cool versus warm climates. For example, the mean embryonic stage at oviposition for S. undulatus females from a population near the northern latitudinal limit at 39°N in New Jersey was very similar to that of females from a southern population at 33°N in South Carolina (New Jersey mean stage = 28.4 versus South Carolina mean stage = 28.8) (Parker et al 2004). These values are similar to the mean embryonic stage at oviposition of 28.8 observed for S. undulatus females in Virginia.…”

CONVERGENT EVOLUTION OF EMBRYONIC GROWTH AND DEVELOPMENT IN THE EASTERN FENCE LIZARD (SCELOPORUS UNDULATUS)

“…But available data indicate variation among populations was likely neither significant nor systematic. In a recent study of S. undulatus (Parker et al 2004), embryos of females induced hormonally were no less developed than embryos of females that oviposited naturally; moreover, developmental stages at oviposition did not differ between females from NJ and those from SC-two of the populations included in our experiment. Similarly, Qualls and Shine (1998) observed very little variation in embryonic stage within and between populations of scincid lizards (Lampropholis guichenoti).…”

Effects of low‐oxygen conditions on embryo growth in the painted turtle, Chrysemys picta

“…In oviparous tetrapods, embryo growth may be disrupted when gaseous O 2 in the egg incubation environment decreases below normal atmospheric conditions (< 21%; hypoxia hereafter) (Stock and Metcalfe 1987;Kam 1993a;Warburton et al 1995;Dzialowski et al 2002;Parker et al 2004;Chan and Burggren 2005;Eme et al 2013;Tate et al 2015). Still, many tetrapods (e.g.…”