v Alligators from sites with moderate to high [OCPs] produced clutches that hatched at lower rates when compared to sites with low to no [OCPs] (Figs. 2 and 3A). The primary pesticides observed were DDE (a DDT metabolite) and toxaphene (Fig. 3B).
v Concentrations of total and free thiamine were significantly higher in eggs from the reference site (Lochloosa/Orange) when compared to Griffin, Apopka, and Emeralda. (Fig. 4). However, there were no differences in the concentrations of mono and pyrophosphate thiamine across sites. Concentrations of total thiamine in the impacted sites fell below the threshold known to induce embryo mortality syndrome in salmonids.
v Thiamine monophosphate and triphosphate (the active form of thiamine), are not produced until after day 25 of embryo development (Fig. 5).
v Free thiamine and thiamine monophosphate were decreased in clutches with high early and late embryo mortalities (Figs. 6A & B). Likewise, there was a significant positive relationship between free thiamine in yolk and hatch rates (all clutches combined) (Fig. 6E). However, there were no differences in thiamine concentrations among clutches with low, moderate, and high percentage of unbanded eggs (Figs. 6A, B & C).
v There was not a clear pattern in total yolk OCP concentrations among clutches with different viabilities and thiamine concentrations (Fig. 6D).
v All combined these results would suggest that thiamine deficiency might be playing a role in the alligator embryo mortalities observed in some Florida Lakes. Causes for the decline in the concentration of this thiamine are unknown at this time, but might be related to differences in the nutritional value of prey items across the sites studied.
v An additional mechanism that could explain the alligator embryo mortalities, relates to the exacerbation of the oxidative damage caused by exposure of embryos to environmental contaminants. Since thiamine is a cofactor required in many essential enzymatic processes (including repair and prevention of oxidative damage), its deficiency coupled with the presence of contaminants, could act synergistically to increase the incidence of alligator mortalities.
v These hypotheses should be further tested through the conduction of laboratory controlled studies.