Evaluation of the use of dermal scutes and blood samples to determine organochlorine pesticides in Crocodylus moreletii: A non-destructive method for monitoring crocodiles and environmental health

This study determines the suitability of using blood plasma and dermal scute samples as a non-destructive technique for monitoring the health of Morelet’s crocodiles and the presence of organochlorine pesticides (OCPs) in the environment. We collected samples (blood plasma and caudal scutes) from 30 Morelet’s crocodiles (C. moreletii); 16 were wild, and 14 were captive. The 30 samples were analyzed for 24 different OCPs and compared in 10 groups based on chemical affinities (isomers and degradation products). Endrin and Chlordane were the most frequent OCP groups detected, found in 63% and 57% of the samples, respectively. We did not find significant differences in OCP concentrations in tissues (plasma and scutes) between wild and captive crocodiles; there were also no significant correlations among concentrations in tissues. Blood plasma and scutes are good indicators of OCP body burdens in Morelet’s crocodiles for monitoring the presence and fluctuation of toxicity in the environment; however, it is not possible to infer the concentrations in one tissue from the concentrations detected in the other tissue. Selecting which tissues to use for OCP analyses depends on the specific objectives of the researcher. For research, on individual health and local exposure to contaminants, plasma is suitable. For evaluating the presence over time of OCPs in the environment, the caudal dermal scutes are the most appropriate tissue. Overall, it is important to take into account the body condition to avoid biases due to bioamplification effects.