Article Review: Critical Windows of Cardiovascular Susceptibility to Developmental Hypoxia in Common Snapping Turtle (Chelydra serpentina) Embryos

Environmental fluctuations have serious impacts on all organisms in the animal kingdom, especially animals such as turtles whose sex is environmentally determined. As climate changes coupled with environmental pollutants alter the chemical balance of nature we will see animals affected in a more negative way than we have seen so far. An interesting study I came across was conducted by a team of Biologist in North Texas that focused on the susceptibility of the cardiovascular systems in common snapping turtles when they were in low oxygen zones. Hypoxia is the scenario when the body or a region of the body is deprived of oxygen leading to incomplete development and other health problems. In common snapping turtles Chelydra serpentina developmental hypoxia has been shown to negatively inhibit the cardiovascular formation in developing embryonic turtles. Decreased oxygen levels at certain points in embryonic turtle development lead to different alterations in cardiovascular development. To investigate the effects of anaerobic periods on the development on common snapping turtles, researchers gathered seven clutches of turtle eggs and incubated them in a lab. Previous studies on turtle development have shown that cardiovascular development differs between male and female embryos, thus researcher’s incubated all the eggs gathered at 30 C to produce a female only study group. The scientists then divided the eggs into five study groups, each receiving different amounts of O2 during the developmental phase. All five groups were given normal oxygen levels for the first 50% of their developmental phase at which point two groups had changes in their oxygen level, then two more groups experienced changes in their oxygen level a70% in to their developmental phase while the fifth group did not experience change in its oxygen level at all. The study showed that embryonic development was greatly affected by hypoxia and that turtles who experienced hypoxia were significantly smaller than the control group that developed under normal oxygen levels. Statistical analysis indicated that there was no differences in the mass of heart tissue for turtles who had experienced hypoxia and turtles who had not, but relative heart mass was found to be significantly affected by hypoxic conditions. By assessing the data and interpreting the results, scientists concluded that a critical window exist between 50%-70% development where turtle embryo are extremely sensitive to hypoxic conditions. At this point turtle are prone to heart enlargement relative to body size while at other points no noticeable problems arise from hypoxia. Turtles like many other reptiles and amphibians provide no parental care for their young and thus it is important for eggs to be laid in stable environments with ample resources. As humans continue to alter ecosystems with our pollutants many environmental factors such as oxygen levels can change drastically in a short time. These changes can drastically impact the development of key species such as turtles and the impact can be detrimental to a species. For this reason it is important for humans to monitor and deter dumping pollutants into the air and land not only for the health of the people but also for the safety of the animals.