Organochlorine compound egg burden and eggshell features in Caiman latirostris

ZAYAS MARCELO; STOKER CORA; FERREIRA MARIA; DURANDO MILENA; GALOPPO GERMÁN; RODRÍGUEZ HORACIO; BELDOMÉNICO, HR; CALDINI, EG; LUQUE ENRIQUE; MUÑOZ DE TORO MÓNICA

Santa Fe

Workshop; 2nd Latin American Pesticide Residue Workshop; 2009

Organochlorine compounds (OCCs) present in the environment include agricultural and industrial compounds. Due to their widespread use, lipid solubility, persistence in the environment, biomagnification through the food net and endocrine disrupting activity, OCCs are a serious concern for wildlife. Caiman latirostris is an oviparous species with aquatic habits widely distributed in South America. Because of their position in the upper trophic levels, prey preferences, nonmigratory habits, and longevity, caimans have the potential to accumulate high concentrations of OCCs. The eggshell is formed during passage of the eggs through the oviduct. Since the oviduct is a target of hormone actions, OCCs exposure could modify oviductal histofunctional characteristics. In birds, reduced eggshell quality due to OCCs exposure has been reported. A decrease in eggshell thickness and porosity could affect gas and water exchange contributing to poor hatch rate. In this background, we assessed the relationship between the burden of OCCs in C. latirostris eggs, eggshell thickness and porosity. Eleven clutches were collected from wetlands on Parana River tributaries, in northeastern Argentina. Eggs were collected shortly after oviposition, two eggs by clutch were used to establish OCCs burden and eggshell thickness, while one egg by clutch was used for eggshell porosity. A high diversity of OCCs was found in 95% of egg samples. OCCs most frequently found were: p,p´-DDE; oxychlordane and PCBs. Eggshell thickness, measured from photomicrographs by image analysis, was 397.4±5.24 m and no association with OCCs burden was found. Eggshell porosity was examined by scanning electron microscopy. The number of pores in the outer surface was 29.5±7 pores/cm2. A trend for an inverse correlation between porosity and OCCs burden was found. These results support the use of caiman eggs for OCCs monitoring in wetlands. Furthermore, a reduced eggshell quality due to OCCs pollution suggests that caiman embryonic viability could be threatened. The preservation of the caimans entails the preservation of whole wetland ecosystems, which would otherwise be drained and converted to croplands causing loss of biodiversity and habitat fragmentation.