Improving reptile ecological risk assessment: Oral and dermal toxicity of pesticides to a common lizard species (Sceloporus occidentalis)

Abstract

Reptiles have been understudied in ecotoxicology, which limits consideration in ecological risk assessments. The goals of the present study were 3-fold: to improve oral and dermal dosing methodologies for reptiles, to generate reptile toxicity data for pesticides, and to correlate reptile and avian toxicity. The authors first assessed the toxicity of different dosing vehicles: 100 μL of water, propylene glycol, and acetone were not toxic. The authors then assessed the oral and dermal toxicity of 4 pesticides following the up-and-down procedure. Neither brodifacoum nor chlorothalonil caused mortality at doses ≤ 1750 μg/g. Under the "neat pesticide" oral exposure, endosulfan (median lethal dose [LD50] = 9.8 μg/g) was more toxic than λ-cyhalothrin (LD50 = 916.5 μg/g). Neither chemical was toxic via dermal exposure. An acetone dosing vehicle increased λ-cyhalothrin toxicity (oral LD50 = 9.8 μg/g; dermal LD50 = 17.5 μg/g), but not endosulfan. Finally, changes in dosing method and husbandry significantly increased dermal λ-cyhalothrin LD50s, which highlights the importance of standardized methods. The authors combined data from the present study with other reptile LD50s to correlate with available avian data. When only definitive LD50s were used in the analysis, a strong correlation was found between avian and reptile toxicity. The results suggest it is possible to build predictive relationships between avian and reptile LD50s. More research is needed, however, to understand trends associated with chemical classes and modes of action.

Tissue distribution, metabolism and hepatic tissue injury in Chinese lizards (Eremias argus) after a single oral administration of lambda-cyhalothrin

“…Walker and Ronis (1989) have presumed that reptiles may be more susceptible to pesticides than mammals or birds due to their low metabolic rate and simple enzymatic systems, which results in the slow breakdown of deltermethrin in the body (Walker and Ronis, 1989). However, predictive relationships between birds and reptile LD 50 were found in another study (Weir et al, 2015). These different conclusions may result from different exposure methods and levels.…”

“…Our previous study demonstrated that the elimination rate of LCT in earthworms was lower than that of bifenthrin (Chang et al, 2016). Weir et al (2015) recently found LCT to be more acutely toxic to Western fence lizards than avians (Weir et al, 2015). Little is known about the toxicokinetics of LCT in reptiles.…”

“…Several studies have focused on the toxic effects of metals in turtles (Meyer et al, 2014) or conducted ecological risk assessment of industry chemicals on lizards (Weir et al, 2014). As little information on reptilian ecotoxicology is available, birds are often used, perhaps inappropriately, as surrogates in risk assessment (Weir et al, 2015). It is essential to obtain toxicokinetic data for the absorption, distribution, metabolism and excretion of pesticides in reptiles.…”

Exposure to rodenticides in Northern Spotted and Barred Owls on remote forest lands in northwestern California: evidence of food web contamination

“…Although BO are also predominantly consumers of mammal species (60-70% rodents and lagomorphs), their diets include a higher portion of birds and insects as well as amphibians, fish, reptiles, snails, and crayfish. Previous studies have detected AR in insects, reptiles, fish, and mollusk species, but many of these accounts stem from experimental toxicity studies or were part of monitoring efforts after accidental AR discharge or intensive AR application for eradication of invasive species (Eason and Spurr 1995, Primus et al 2005, Rueda et al 2005, Weltje et al 2013, Weir et al 2015.…”

Baseline values of immunologic parameters in the lizard <i>Salvator merianae</i> (<i>Teiidae</i>, Squamata)

“…The implementation of a system that combines the use of new technologies includes use/application of chemicals in bulk. The effects of these agents, combined with environmental factors (i.e., habitat fragmentation/degradation, draining of wetlands) have produced a decline in the populations of various wild species, among them several types of reptiles (Gibbons et al, 2000;Santos and Llorente, 2009;Weir et al, 2015). In particular, tegu lizard populations have plummeted in areas where agricultural activity has advanced.…”