Endocrine Active Effects on Turtle Embryonic Development

Science Center Objects

The Challenge: Emerging contaminants may be in part responsible for recent endocrine disruption observed in fish in the Chesapeake Bay watershed. Endocrine active compounds implicated in the decline of fish populations may affect other wildlife as well. There are 6 species of turtles and 5 of snakes living within the main-stem and tidal areas of the Bay. As poikilotherms, reptiles are dependent on their surrounding habitat for seasonal and daily physiological and behavioral processes. In many cases, their response to changes in their environment is regulated directly or indirectly by their endocrine system. Because embryonic development and reproductive systems are so divergent in the reptilian class, to date in situ EDC research has focused on the oviparous reptile model.

The Science: Most turtles occupy a high trophic position, have limited geographic home ranges, and therefore can bioaccumulate locally available chemical contaminants. Many turtle species exhibit environmental sex determination: gender is based on the temperature range in which the embryos develop. As estrogens and the aromatase enzyme play a significant role this process, gender outcome can be manipulated experimentally to screen for effects from endocrine disrupting or emerging contaminants. Commercially available fresh red eared slider eggs will be artificially incubated at 26°C , the male producing temperature for this species, and will be exposed to extracts of water collected from a series of contaminated field sites. Measurements on the chemical taken up into the embryo will be analyzed to assess exposure, and a series of biochemical and endocrine related endpoints will be collected on hatchlings to evaluate potential effects on gonadal and other organs development. Abbreviated trials will be conducted on 2 additional turtle species to assess relative species sensitivity. Embryos and hatchlings will be processed as described above for the RES.

The Future: This study proposes a novel, environmentally relevant exposure protocol for assessing the sensitivity in oviparous reptiles. Data collected on exposure and effects will be analyzed to evaluate reptilian responses to environmental endocrine chemicals and the effectiveness of the protocol. Additional endpoints related to hatchling behaviors and metabolic costs may be sought to further enhance our understanding of risk assessment in poikilothermic vertebrates.