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

Abstract

Low-oxygen conditions (hypoxia; <21% O ) are considered unfavorable for growth; yet, embryos of many vertebrate taxa develop successfully in hypoxic subterranean environments. Although enhanced tolerance to hypoxia has been demonstrated in adult reptiles, such as in the painted turtle (Chrysemys picta), its effects on sensitive embryo life stages warrant attention. We tested the hypothesis that short-term hypoxia negatively affects growth during day 40 of development in C. picta, when O demands are highest in embryos. A brief, but severe, hypoxic event (5% O for 0.5 h) moderately affected embryo growth, causing a 13% reduction in mass (relative to a normoxic control). The same condition had no effect during day 27; instead, a nearly anoxic event (1% O for 72 h) caused a 5% mass reduction. All embryos survived the egg incubation period. Our study supports the assumption that reptilian embryos are resilient to intermittently low O in subterranean nests. Further work is needed to ascertain responses to suboptimal O levels while undergoing dynamic changes in developmental physiology.

Transplanting gravid lizards to high elevation alters maternal and embryonic oxygen physiology, but not reproductive success or hatchling phenotype

“…This corroborates our previous work in this system in demonstrating that early-life stages are relatively resilient to hypoxia and therefore would not limit future colonization of high-elevation habitats beyond the current species range. We emphasize that even our extreme high elevation treatment represents a moderate and biologically relevant reduction in oxygen availability (approximately 72% of sea level equivalent), which explains why we did not find the clear negative effects of hypoxia as have other studies in reptiles exposed to more severe hypoxia, even for short periods of time (Andrews, 2002;Cordero et al, 2017b;Iungman and Piña, 2013;Kam, 1993). The lack of effect of our maternal gestation treatments implies that embryos pre-oviposition did not face a mismatch between oxygen supply and demand.…”

Physiological plasticity in lizard embryos exposed to high‐altitude hypoxia

“…Following a stop‐flow respirometry protocol (Lighton, ; Lighton, & Halsey, ), 16 eggs drawn from eight split clutches (control: N = 8; hypoxia: N = 8) were individually placed in 65‐ml sealed glass jar chambers with moist vermiculite (50 ml) held at a constant 24°C, for example, Cordero et al. (). The egg chamber was then flushed and sealed for 180 min, incurrent air flow (200 ml/min; from chamber to respirometer) was restored and water scrubbed from air using drierite desiccant (Hammond Drierite, Xenia, Ohio, USA).…”

“…Similarly, physiological processes that enhance O 2 transport have the potential to evolve in birds (Rahn et al., ; Hammond et al., ; Storz, ; Monge, & Leon‐Velarde, ). Whether responses to cope with hypoxia in high‐altitude environments are general to non‐avian reptiles is unclear (McNab, ; Powell, & Hopkins, ), though laboratory manipulations at low altitude would support this assumption (Kam, ; Warburton, Hastings, & Wang, ; Andrews, ; Du, Thompson, & Shine, ; Eme, Altimiras, Hicks, & Crossley, ; Harrison, Shingleton, & Callier, ; Liang, Sun, Ma, & Du, ; Smith, Telemeco, Angilletta, & VandenBrooks, ; Cordero, Karnatz, Svendsen, & Gangloff, ; Crossley, Ling, Nelson, Gillium, Conner et al., ).…”

Substrate Influences Turtle Nest Temperature, Incubation Period, and Offspring Sex Ratio in the Field

“…We have no clear explanation for why our results did not accord with the prior research from laboratory and field based experiments. Other factors unmeasured in our experiment, such as oxygen levels, might have varied among substrate types and influenced developmental rates and other phenotypes of eggs (Ackerman 1981;Cordero et al 2017). Nevertheless, the failure of prior work to predict the patterns observed in this experiment highlights a gap in our knowledge.…”