The eggshell features and clutch viability of the broad-snouted caiman (Caiman latirostris) are associated with the egg burden of organochlorine compounds

Abstract

Organochlorine compounds (OCCs) are toxic and have been identified as endocrine-disrupting chemicals (EDCs). The broad-snouted Caiman (Caiman latirostris) is an oviparous species widely distributed in South America with potential to accumulate OCCs. The eggshell is formed during passage of the eggs through the oviduct. Since the oviduct is a target of hormone actions, exposure to OCCs could modify eggshell quality, thus affecting clutch viability. Eight clutches were collected from wetlands of Parana River tributaries, in north-eastern Argentina. Two to four eggs per clutch were used to establish the burden of OCCs, eggshell thickness and eggshell porosity. The remaining eggs were incubated in controlled conditions. Ten days after hatching, hatchling survival was assessed. Organochlorine pesticide residues (OCPs) were found in all clutches, while polychlorinated biphenyls (PCBs) were present in all but one clutch. The principal contributors to the OCP burden were members of the DDT family and oxychlordane. Eggshell thickness was 400.976.0 μm and, unexpectedly, no association between eggshell thickness and the OCC burden was found. The number of pores in the outer surface was 25.374.3 pores/cm2 . A significant inverse correlation between porosity and OCC burden was found (Pearson r¼ 0.81, p¼ 0.01). Furthermore, a decrease in caiman survival with decreased pore density was observed (Pearson r¼ 0.73, p¼ 0.04). Our findings highlight another potential negative impact of current and past use of OCCs on wildlife species.