Organochlorine pesticides in the chorioallantoic membrane of Morelet's crocodile eggs
Pepper, Christopher B
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Organochlorine (OC) pesticides such as DDT were once globally applied. While having relatively low acute toxicities, OCs persist and accumulate in the environment. Such characteristics may present long-term health risks for long-lived, top-level predators, including humans. These risks are amplified in developing countries, where OC pesticides have generally been misused. The presence of OC contaminants in the environment has been extensively studied. Unfortunately, these studies often involve the trapping and killing of wild species; such sampling techniques are known as lethal sampling. There is a need to develop non-lethal sampling techniques for monitoring OC exposure in endangered and threatened species. A proposed example of a non-lethal sampling technique involves using the chorioallantoic membrane (CAM) for estimating OC exposure in oviparous species. Morelefs crocodiles found in Belize are a top-level predator and considered a good sentinel species for investigating OC contamination in the environment. Listed as an endangered and threatened species, non-viable eggs of these crocodiles are also known to contain OC contaminants (Wu et al., 2000a). In this study, viable and non-viable Morelefs crocodile eggs were collected from wild nests located in Gold Button Lagoon, Orange Walk, Belize. The viable eggs were allowed to hatch in natural incubators. As the eggs hatched, CAMs and scute samples from the respective neonates were removed CAM samples were obtained from 7 different nests. Non-viable eggs were obtained from 4 different nests. All samples, CAMs (122), non-viable eggs (19), and scutes (25), were screened for OCs using gas chromatography with electron capture detection. OC contaminants were detected in all three types of samples (CAMs, nonviable eggs, and scutes). DDE was the most prevalent contaminant, and was detected in 69% of the CAMs, 100% of the non-viable eggs, and 4% of the scutes. DDE concentrations in CAMs ranged from 0.3-17.2 ppb. Other contaminants detected in the CAMs included lindane, heptachlor, dieldrin, endrin, DDT, and methoxychlor. DDE concentrations in non-viable eggs ranged from 2.4-144 ppb. Besides DDE, other contaminants found in the non-viable eggs included methoxychlor, aldrin, dieledrin, and heptachlor. Only 2 of the 25 neonate scutes had detectable amounts of OCs. Specifically, scute 3888 was contaminated with methoxychlor (4350 ppb) and scute 3822 was contaminated with both DDE (350 ppb) and DDT (720 ppb). Detection of OC contaminants In CAMs of Morelefs crocodile is cause for concern. This species should continue to be listed under Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and efforts should be maintained to monitor its status.