Trace elements determined in turtles trachemys scripta elegans from the urban area of São Paulo

Abstract

The red-eared-turtle Trachemys scripta elegans, belonging to the suborder Cryptodira and family Emydidae, is farmed in the Mississippi Valley in the USA and sold throughout the world as one of the most traded pets. An increasing number of species are frequently released by owners in natural wetlands and in urban areas. This species is resistant and may spread parasites and threaten native turtle populations. Many countries chose to perform euthanasia to control its population, avoiding the threat to local biodiversity. Animals were studied here using Instrumental Neutron Activation Analysis (INAA) to determine metallic elements Ca, Fe, Na, Zn, aiming to assess the concentrations on different tissues in the body of ten female specimens. All of them donated already euthanized by DEPAVE (Parks and Green Areas Department) U City of São Paulo. The bodies were open with electric saw, with size between 18 and 23 cm of Carapace Length (CL), being all of them adults. The samples analyzed were: superficial and bone carapaces liver, heart, lung, muscle and kidneys. Approximately 200mg of the samples and reference materials, Soil 1 from IAEA and Montana II soil from NIST, were used. Those were irradiated at the IEA-R1 nuclear research reactor at IPEN under a thermal neutron flux of 1012 n per cm2 per s for 6h. Gamma spectrometry was used with a HPGe with relative efficiency of 23% with an associated electronics, to perform the measurements. Methodology validation regarding precision and accuracy were done using reference materials SL- 1 (Lake Sediment – IAEA) and Montana II soils (NIST). The Na, Ca, Zn and Fe concentrations in shell bone and scute were in the same magnitude founded in the literature. The majority of their growth occurs in early years of life then it would be possible to infer that the concentrations found in the central part of their carapace were related to previous years, and the concentrations that were found in the edges can be related to the last months of animals life. Studies regarding cadmium intake focuses in contamination based on animals diet, but as in this study there is few information about the food source the animal received before living in city parks, and before being euthanized they were put in a diet restricted to ration. The Zn concentrations found in the carapace showed higher values in the scute when compared with shell bone. Ca and Na presented the opposite behavior. Future studies related to the metal concentrations in other parts of the animals could indicate the possibility of using this specie as an environmental bioindicator.