Metal and metalloid exposure and oxidative status in free-living individuals of Myotis daubentonii

Abstract

Metal elements, ubiquitous in the environment, can cause negative effects in long-lived organisms even after low but prolonged exposure. Insectivorous bats living near metal emission sources can be vulnerable to such contaminants. Although it is known that bats can bioaccumulate metals, little information exists on the effects of metal elements on their physiological status. For example, oxidative status markers are known to vary after detoxification processes and immune reactions. Here, for two consecutive summers, we sampled individuals from a natural population of the insectivorous bat, Myotis daubentonii, inhabiting a site close to a metal emission source. We quantified metals and metalloids (As, Ca, Cd, Co, Cu, Mn, Ni, Pb, Se, Zn) from individual fecal pellets. We measured enzymatic antioxidants (GP, CAT, SOD), total glutathione (tGSH) and ratio between reduced and oxidized glutathione (GSH:GSSG) from their red blood cells together with biometrics, hematocrit and parasite prevalence. In general, metal concentrations in feces of M. daubentonii reflected the exposure to ambient contamination. This was especially evident in the higher concentrations of Cd, Co, Cu and Ni close to a smelter compared to a site with less contaminant exposure. Annual differences were also observed for most elements quantified. Sex-specific differences were observed for calcium and zinc excretion. SOD and CAT enzymatic activities were associated with metal levels (principal components of six metal elements), suggesting early signs of chronic stress in bats. The study also shows promise for the use of non-invasive sampling to assess the metal exposure on an individual basis and metal contamination in the environment.

Bats Oxidative Stress Defense

“…An understanding of oxidative stress status in bats can help reveal the pattern of transmission of the virus from bats to other vulnerable hosts. Exposure to toxins, ectoparasites, weather changes, and physiological cycles can interfere with bat oxidative homeostasis and result in oxidative stress (Lilley et al, 2013;Oliveira et al, 2018;Ruiz, Eeva, Kanerva, Blomberg, & Lilley, 2019). The use of pesticides (e.g., Deltamethrin) on fruit plantations impacts the increase in stress oxidative markers in fruit bats (Oliveira et al, 2018).…”

“…The use of pesticides (e.g., Deltamethrin) on fruit plantations impacts the increase in stress oxidative markers in fruit bats (Oliveira et al, 2018). Heavy metal contamination in bat habitat also impact on decreasing endogenous antioxidants and increasing ROS in bats (Ruiz et al, 2019). Stress on bats due to the infection of white-nose syndrome, which is highly pathogenic to bats, can causes increased viral replication and viral shedding from bats (Davy et al, 2018).…”