Exposure to lead induces hypoxia-like responses in bullfrog larvae (Rana catesbeiana)

Amphibians collected around mining sites, areas with extensive automobile t raffic, and shooting ranges have been documented to contain high levels of lead. Lead-exposed amphibians might respond as if in hypoxic conditions bec ause exposure is known to decrease hemoglobin levels, damage erythrocytes, and alter respiratory surfaces. Therefore, we exposed bullfrog larvae to ei ther 0 or 780 mu g/L Pb and either 3.50 or 7.85 mg/L oxygen for 7 d and mon itored activity, trips to the surface, and buccal ventilation rates. Activi ty was significantly decreased in larvae exposed to low oxygen, Pb, or both compared to activity of larvae in high oxygen with no Pb. Larvae exposed t o both Pb and low oxygen displayed higher buccal ventilation rates than lar vae exposed to either treatment separately. Lead-exposed larvae surfaced si gnificantly more often than unexposed larvae even under high-oxygen conditi ons. Lead-exposed larvae decreased in mass during the exposure period, wher eas unexposed larvae increased in mass. Lead exposure could decrease surviv al of larvae in the field not only because of physiological problems due to decreased oxygen uptake but also because of greater predation pressure due to increased presence at the surface and reduced growth rates.