Effect of Acute Exposure to Malathion and Lead on Sprint Performance of the Western Fence Lizard (Sceloporus occidentalis)

Abstract

There are few ecotoxicological studies involving reptiles, despite the fact that anthropogenic pollutants have been identified as a major threat to reptile populations worldwide. Particularly lacking are effects-based studies in reptiles exposed to known concentrations of contaminants. We hypothesized that acute exposure to neurotoxic metals and pesticides could influence locomotor performance of reptiles. To test this hypothesis, we exposed western fence lizards (Sceloporus occidentalis) to two common and widely studied neurotoxic contaminants, malathion and lead (Pb). Single doses were administered via oral gavage at order-of-magnitude levels ranging from 0.2 to 200 and 1.0 to 1,000 mg/kg (body weight basis) for malathion and Pb, respectively. Lizard sprint velocity was determined using a 2.3-m sprint track interfaced with a laptop computer 24 hrs prior to dosing and again at 4, 24, 120, and 312 hrs post-dose. Twenty percent and 30% mortality occurred at the highest malathion and Pb dose levels (200 and 1000 mg/kg) and 70% of the lizards exposed to 200 mg/kg malathion exhibited clinical symptoms of organophosphate poisoning. Contrary to our predictions, exposure to Pb had no effect on locomotor performance, and exposure to the highest concentration of malathion increased sprint velocity. Based on the fact that the lower and most ecologically relevant concentrations of Pb and malathion had no effect on sprint velocity, we suggest that other performance parameters that require fine locomotor skills (e.g., climbing ability) may be more sensitive metrics of acute neurotoxicity and warrant further study.

High levels of maternally transferred mercury disrupt magnetic responses of snapping turtle hatchlings (Chelydra serpentina)

“…We placed hatchlings at the start of a 2.3 m sprint track lined with pairs of photocells projecting infrared beams at 10 cm intervals which were interfaced with a laptop computer (Columbus instruments, Columbus, OH; described in full by Holem et al (2006) in an environmental chamber maintained at 25 C. We stimulated hatchlings with a pair of blunt forceps at the base of their tail to elicit a forward locomotor response. Once the hatchling ceased moving, we waited 10 s before administering an additional stimulus and repeated this process as needed until the hatchling covered a distance of one meter.…”

Estimating maximum performance: effects of intraindividual variation

“…Locomotor performance of S. occidentalis has been studied in diverse contexts (e.g. Bennett, 1980;Bennett and Gleeson, 1976;Garland et al, 1990;Gleeson, 1979;Holem et al, 2006;Marsh and Bennett, 1986;Schall et al, 1982;Sinervo and Adolph, 1989;Sinervo and Huey, 1990;Sinervo and Losos, 1991;Tsuji et al, 1989;van Berkum, 1988;van Berkum and Tsuji, 1987;van Berkum et al, 1989).…”

Fitness Consequences of Infection by Batrachochytrium dendrobatidis in Northern Leopard Frogs (Lithobates pipiens)

“…Locomotory ability correlates positively with hunting success, escape from predators (Christian and Tracy 1981;Trombulak 1989), dispersal (Phillips et al 2006), and mating success in several vertebrate species, the latter specifically through achieving victory in male combat via speed or agility (Able 1999;reviewed in Lailvaux and Irschick 2006;Husak and Fox 2008). Locomotor performance has also previously been used as an indicator of the health of an individual (Holem et al 2006;Richard et al 2010; but see Vervust et al 2008), and declines prior to signs of morbidity or mortality associated with infection (Goater et al 1993;Oppliger et al 1996). Similarly, testis size, germinal epithelium depth, and spermatic cyst diameter are closely tied to reproductive success in several vertebrate taxa, and collectively may be used as a proxy for reproductive fitness among males (McCallum and Trauth, 2007).…”