Few data exist regarding maternal-embryonal transfer of organochlorine pesticides (OCPs) in reptiles. The objective of the present study was to evaluate maternal transfer of OCPs in American alligators (Alligator mississippiensis) from low-, intermediate-, and high-OCP-exposure sites. Overall, total OCP burdens ranged from less than 0.8 ppb in blood to more than 44,000 ppb in abdominal adipose tissue (wet wt concentrations). Lipid-adjusted ratios of maternal adipose burdens (total OCPs) to yolk burdens were close to one (0.94 +/- 0.31:1), suggesting that animals were in steady state and that OCPs in eggs originated from adipose lipids. In contrast, lipid-adjusted muscle and liver OCP burdens were greater than yolk OCP burdens, suggesting that lipids in muscle were not utilized during oogenesis and that nonlipid liver tissue sequesters OCPs. Predictive equations were derived for several tissues and several OCP analytes with r2 values ranging from 0.40 to 0.99 (p < 0.05). We suggest that yolk burdens are predictive of maternal tissue burdens for certain tissues and OCPs and that certain OCPs are maternally transferred in the American alligator. Furthermore, we suggest that future studies should investigate the applicability of these predictive equations for assessing maternal exposure in other crocodilian species.

In central Florida, alligators (Alligator mississippiensis) inhabiting lakes contaminated with organochlorine pesticides (OCPs) produce eggs that have high OCP concentrations and low clutch viability (proportion of eggs in a clutch that yield a live hatchling) compared to those from less contaminated lakes (reference lakes). However, a clear dose-response relationship has not been established between OCPs and poor clutch viability. In order to better elucidate a cause and effect relationship between OCP exposure and clutch viability, we conducted concurrent field and laboratory studies. Our field study reaffirmed that eggs of wild alligators from OCP-contaminated lakes and wetlands continue to have lower clutch viability and higher OCP burdens than eggs from reference lakes. Our field study also demonstrated that OCP egg burdens were strongly correlated with clutch viability for some of the OCP-contaminated sites, but not all. To better test causal relationships, a parental exposure study was conducted using captive adult alligators. Our laboratory study demonstrated that dietary exposure of captive alligators to an ecologically relevant OCP mixture caused alligators to produce eggs with higher OCP burdens and reduced clutch viability, as compared to the captive-control population. The experimentally induced egg burdens and clutch viability reductions were similar to those of wild alligators from OCP-contaminated sites. Our field and laboratory results suggest parental OCP exposure may be contributing to low clutch viability in wild alligators inhabiting OCP-contaminated habitats, raising some concern for endangered crocodilians living in OCP-contaminated habitats.

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Thiamine deficiency has been linked to early mortality syndrome in salmonids in the Great Lakes. This study was conducted to compare thiamine concentrations in American alligators (Alligator mississippiensis) and Florida largemouth bass (Micropterus salmoides floridanus) eggs from sites with high

Previous population genetic studies of diamondback terrapins (Malaclemys terrapin) have typically focused on either the entire range or relatively small spatial scales. The Louisiana coastline contains vast salt marshes suitable for terrapins; however, two major freshwater inputs (Atchafalaya River and Mississippi River Deltas) break up the seemingly contiguous habitat and may isolate populations of terrapins. To determine population genetic structure and connectivity of terrapins occupying Louisiana marshes, we collected 573 individuals from 26 study sites across the Louisiana coastline. Twelve microsatellite loci were used to evaluate population structure using standard genetic and spatially explicit approaches. Patterns of gene flow were examined via model testing, including those to determine if freshwater inputs serve as barriers to movement. We also assessed levels of genetic diversity, inferred the historical demography and estimated effective population sizes across our sampling. While we did not detect significant population structure, we found that terrapins are not panmictic, and demonstrated a pattern of isolation by distance along the Louisiana coastline. Genetic diversity in this study was comparable to the Atlantic coast, but was higher than other sites within the Gulf of Mexico. Though terrapins in eastern Louisiana were historically harvested and apparently experienced a genetic bottleneck, this is not reflected in estimates of effective population sizes. Although, there was no strong genetic structuring across Louisiana, historical differences and patterns of habitat loss suggest that it may be necessary to develop separate management strategies for the western and eastern portions of the state.

Since the early 1900s, the lakes of the Ocklawaha basin in central Florida have experienced ecological degradation due to anthropogenic development. One species affected by this degradation is the American alligator Alligator mississippiensis, which has suffered from poor clutch viability and embryo mortality. Although some studies indicate that organochlorine pesticides (OCPs) may be involved, OCPs do not account for all of the variation seen in hatch rates. Indeed, nutrition and non-OCP contaminants have been associated with developmental problems in fish and birds. Our study evaluated embryo mortality in alligators at reference and OCP-contaminated sites as a function of exposure to OCPs, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs), along with egg nutrients (Zn, Se, and vitamins A, E, and B1). The four-pronged study consisted of a case-control cohort study, an expanded field study, a topical egg treatment thiamine amelioration experiment, and a topical egg treatment thiamine antagonist experiment. The results from the two field studies suggested that the total thiamine levels in the eggs were positively associated with clutch viability and negatively associated with the lipid content and certain OCPs measured in egg yolks. In addition, PCBs, PAHs, Zn, Se, and vitamins A and E were not found to be associated with the observed clutch viability defects. The thiamine levels in the eggs explained 38% of the variation in clutch survival in the case-control cohort study and 27% in the expanded field study. The topical egg treatment experiments were successful in elevating the thiamine concentrations in the albumin but not the yolk. No significant differences were noted among treatment groups in either egg treatment experiment with respect to clutch survival. In summary, thiamine egg concentrations explain some of the variation in the clutch viability of free-ranging alligators, but the cause-effect relationships are still unclear.

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