Anti-parasite treatment results in decreased estimated survival with increasing lead (Pb) levels in the common eiderSomateria mollissima

Abstract

Field experiments where parasites are removed through treatment and contaminant levels in host tissues are recorded can provide insight into the combined effects of parasitism and contaminants in wild populations. In 2013 and 2014, we treated northern common eider ducks ( Somateria mollissima ) arriving at a breeding colony with either a broad-spectrum antihelminthic (PANACUR ® ) or distilled water, and measured their blood lead (Pb) levels. Breeding propensity and clutch sizes were inversely related to Pb in both treatment groups. In comparison, a negative effect of Pb on resight probability the following year was observed only in the anti-parasitic treatment (APT) group. These contrasting patterns suggest a long-term benefit to survival of intestinal parasitism in eiders experiencing Pb exposure. The arrival date of hens explained some, but not all, of the effects of Pb. We weigh the merits of different hypotheses in explaining our results, including protective bioaccumulation of Pb by parasites, condition-linked thresholds to costly reproduction and the direct effects of APT on eider health. We conclude that variation in helminth parasitism influences survival in this migratory bird in counterintuitive ways.

Potential Benefits of Acanthocephalan Parasites for Chub Hosts in Polluted Environments

“…11,16 Consequently, intestinal parasites may mitigate the production of highly reactive molecules generated from parent pollutants, thereby lowering toxicity. 5 This explanation is however not fully supported by our results, since infected and uninfected chub did not differ in their pollutant load. On the other hand, individual quality could be a potential confounding factor.…”

“…In fact, even stronger impacts on the oxidative status may be expected, since phthalate metabolites were associated with lower antioxidant capacity in chub, which is further supported by Qu et al Recent findings also evidenced that parasites were beneficial to crustacean intermediate hosts exposed to pollution, by increasing antitoxic defenses, , thus favoring their own survival and transmission to the final host. Possible explanations for our results include the sequestration of chemicals in parasites, which might affect the internal distribution and levels of contaminant in fish. , Consequently, intestinal parasites may mitigate the production of highly reactive molecules generated from parent pollutants, thereby lowering toxicity . This explanation is however not fully supported by our results, since infected and uninfected chub did not differ in their pollutant load.…”

“…Parasitic interactions can switch to mutualistic ones, and vice versa, under stressful biotic and environmental − conditions. Among the multiple factors investigated, the effect of chemical pollution on species interaction remains poorly investigated . In aquatic environments, such an effect is however of primary importance given the direct proximity to contamination sources (poor wastewater treatment, stormwater runoff, leaching from green spaces and agriculture, accidental discharge; see the work of Pierce et al).…”

“…29 On the other hand, cestode infection has been shown to reduce intermediate host mortality across a range of arsenic concentrations. 30 Similarly, decreased survival with increasing lead (Pb) levels was observed in common eiders (Somateria mollissima) treated with an antiparasite drug, 5 suggesting a protective effect of parasites in Pb-exposed individuals. General biomarkers are known to respond to a variety of stressors, natural or anthropogenetic, 31 being thus appropriate to investigate the response of host-parasite systems to pollutant exposure.…”

Evidence of Low-Habitat Contamination Using Feathers of Three Heron Species as a Biomonitor of Inorganic Elemental Pollution

“…Lead is a toxic metal to wildlife, especially in gamebirds such as Anatidae and Galliformes [50]. The use of lead shot in hunting can cause toxic or sublethal effects, altering hematocrit level, impairing breeding activity, and reducing clutch sizes as observed in seagulls [51], in Great tit Parus major [52], and [53] Common eider Somateria mollissima. Pb concentrations of 4 mg Kg −1 in feathers are known to be potentially toxic [16], and levels exceeding a threshold concentration have been related to lower eggshell thickness and impaired eggshell structure [54], decreased survival of nestlings, altered recognition of siblings, and thermoregulation imbalance [48]; even lower Pb concentrations can induce severe histopathological damages and necrosis associated with reduced enzymatic functionality [55].…”