Organochlorine pesticides and mercury in cottonmouths (Agkistrodon piscivorus) from northeastern Texas, USA

Abstract

Despite their ecological importance and global decline, snakes remain poorly studied in ecotoxicology. In this study, we examined organochlorine (OC) pesticide and mercury accumulation in cottonmouths (Agkistrodon piscivorus) living on a contaminated site in northeastern Texas (USA). Mercury and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) were detected in all snakes examined. Other OCs, including p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), methoxychlor, aldrin, and heptachlor, also were detected, but less frequently. Concentrations of p,p'-DDE were higher in fat than in liver, while mercury concentrations were highest in liver, followed by kidney and tail clips. One animal contained the highest mercury concentration yet reported for a snake (8,610 ng/g). Mercury concentrations in liver and kidney were higher in males than females, while no intersex differences in p,p'-DDE concentrations were observed. Concentrations of p,p'-DDE in fat were correlated positively with body size in male cottonmouths but not females, suggesting a slower rate of accumulation in females. Body size strongly predicted mercury concentrations in liver, kidney, and tail clips of both sexes. Tail clips were strong predictors of mercury in liver and kidney in males but not females, suggesting possible sex-dependent differences in mercury toxicokinetics. Both long-term field studies and controlled laboratory investigations are needed to adequately assess the response of cottonmouths to chronic contaminant exposure.

Assessment of Pathogens and Toxicants in New Orleans, LA Following Hurricane Katrina

“…Concentrations of these contaminants were generally lower than, but in some cases similar to, those detected in conspecifics examined in previous studies (19)(20)(21)(22)(23)(24). For example, DDE concentrations in cottonmouth fat analyzed in this study (range ) nondetectable [ND] to 0.1 µg/g; n ) 6) were predominantly lower than those recently reported for cottonmouths in eastern Texas (range ) 0.1 -14.0 µg/g; n ) 19) (24). Conversely, mercury concentrations in some cottonmouth livers examined in this study (range ) ND to 0.4 µg/g) fell within the range of those reported in cottonmouths from eastern Texas (range ) 0.1 -8.6 µg/g) (24) and northern water snakes (Nerodia sipedon) from eastern Tennessee (range ) 0.09 -3.98 µg/g; n ) 47) (23).…”

Ecological factors regulating mercury contamination of fish from Caddo Lake, Texas, USA

“…Similar benchmarks have been proposed by Eisler [65], who recommends less than 100 ng/g of total Hg in food items as a protective level for sensitive species of birds and mammals that regularly consume fish and aquatic invertebrates. Previous studies at Caddo Lake have found that piscivorous snakes captured near wetland habitats had Hg concentrations as high as 8,610 ng/g wet weight [66], confirming that Hg is bioaccumulating to high levels in piscivorous wildlife. Six of the eight species collected from the wetland had mean Hg concentrations above the U.S. EPA critical value for birds.…”

Inter‐ and Intraspecific Variation in Mercury Bioaccumulation by Snakes Inhabiting a Contaminated River Floodplain

“…Mercury concentrations in tissue of giant garter snakes ( T. gigas ) did not differ between sexes . Conversely, Rainwater et al found that male cottonmouths exhibited significantly higher Hg concentrations in liver and kidney tissue than females. Campbell et al found that male northern watersnakes had significantly higher Hg concentrations in muscle than females, although their data were not corrected for body size.…”