Nutrient and Organochlorine Pesticide Concentrations in American Alligator Eggs and Their Associations with Clutch Viability

Abstract

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.

Intrinsic and extrinsic factors interact during development to influence telomere length in a long‐lived reptile

“…This resulted in eight treatment groups, and the sample sizes of each are reported in Table 1. The dose of DDE is based on levels previously measured in field collected eggs from contaminated lakes (Rauschenberger et al, 2009). Following dosing, eggs were returned to their temperature treatments and incubated until hatching.…”

Assessing the Ability of Developmentally Precocious Estrogen Signaling to Recapitulate Ovarian Transcriptomes and Follicle Dynamics in Alligators from a Contaminated Lake

“…Both locations and populations are well characterized; AP is characterized by high levels of OCP contaminants, the product of long-term agricultural runoff and an acute spill event of dicofol, a dichlorodiphenyltrichloroethane (DDT) and DDTmetabolite-containing miticide, in the 1980s. These contaminants have been detected at high levels in adult and juvenile alligators and in egg yolk (Guillette et al 1994(Guillette et al , 1999Heinz et al 1991;Rauschenberger et al 2007Rauschenberger et al , 2009Woodward et al 2011). In contrast, WO is a site for which minimal anthropogenic disturbance or contaminant input has been detected and is used herein as a reference site (Crain et al 1998;Guillette et al 1994;Milnes et al 2005aMilnes et al , 2008Moore et al 2010bMoore et al , 2010cPickford et al 2000).…”

“…Among wildlife models, studies on a population of American alligators inhabiting a highly contaminated freshwater system, Lake Apopka (AP), in central Florida (Orange County, FL) helped to pioneer our early understanding of how contaminant exposure during embryonic stages determines future reproductive health. There, developmental exposures to a complex mixture of organochlorine pesticides (OCPs) (Heinz et al 1991;Rauschenberger et al 2007Rauschenberger et al , 2009 have been associated with a suite of reproductive abnormalities, including ovarian and testicular morphological abnormalities (Guillette et al 1994) and shifts in gonadal transcription that persist into juvenile stages (Hale et al 2019;Kohno et al 2008;Moore et al 2012). Reproductive pathologies at AP have been repeatedly observed in juvenile animals collected as eggs and raised under controlled laboratory settings, demonstrating a persistent site-of-origin effect that appears to have developmental origins (Guillette et al 1994;Hale et al 2019;Moore et al 2012).…”

Incubation Temperature and Maternal Resource Provisioning, but Not Contaminant Exposure, Shape Hatchling Phenotypes in a Species with Temperature-Dependent Sex Determination

“…At stage 19, eggs were topically dosed with one of three treatments: vehicle control (0.2 mg g 21 egg weight absolute ethanol), low-dose DDE (0.1 mg g 21 egg weight; ∼100 ppb; 4,4 0 -DDE Pestanal, Sigma Aldrich, St. Louis, MO), or high-dose DDE (1 mg g 21 egg weight; ∼1 ppm) (Kohno and Guillette, 2013). Doses were chosen based on levels measured in field-collected alligator eggs from contaminated lakes and associated with impaired reproductive function (Rauschenberger et al, 2009). Eggs were then maintained at their respective thermal regimes until hatching.…”