The interactive effects of chytrid fungus, pesticides, and exposure timing on gray treefrog (Hyla versicolor) larvae

Abstract

Aquatic organisms are often exposed to a wide variety of perturbations in nature, including pathogens and chemical contaminants. Despite the co-occurrence of these 2 stressors, few studies have examined the effects of chemical contaminants on host-pathogen dynamics. The authors tested the individual and combined effects on gray treefrog (Hyla versicolor) tadpoles of 2 commonly used pesticides (Roundup® and Sevin®) and the pathogenic fungus Batrachochytrium dendrobatidis (Bd). A fully factorial design was used, and tadpoles were exposed to Bd, Roundup, or Sevin alone, or a combination of Bd and either pesticide at 3 points during larval development (early, mid, late). It was predicted that pesticides would mediate the effect of Bd on tadpoles and reduce the likelihood of negative consequences of infection and that timing of exposure would influence these effects. Tadpoles exposed to Bd at the mid point experienced higher survival through metamorphosis than those exposed to Bd at the early or late points, while tadpoles exposed to Sevin at the early point experienced reduced survival compared with those exposed to Roundup or no-pesticide control at the same exposure point. Roundup ameliorated the effects of Bd on survival compared with tadpoles exposed to Bd alone, while there was no interactive effect of Sevin on survival. In addition, Sevin reduced mass of new metamorphs compared with Roundup and reduced snout-vent length compared with all other treatments. The present study supports the hypothesis that pesticides can mitigate the effects of Bd on amphibian hosts and that such effects may depend on the timing of exposure.

Challenges and opportunities in developmental integrative physiology

“…However, many studies that aim to detect critical windows do so using just a single dose of a stressor ( e.g. Koger et al, 2000; van Aerle et al, 2002; Hogan et al, 2008; Hanlon and Parris, 2014), and this may influence the detection of a critical window. Moreover, there is potentially a strong reliance on how successfully a critical window is detected based on the doses used.…”

Disentangling host, pathogen, and environmental determinants of a recently emerged wildlife disease: lessons from the first 15 years of amphibian chytridiomycosis research

“…Recent research has also focused on the identification of mechanisms leading to variation in effects of Bd across hosts or communities, such as understanding how behavior (Venesky et al. ), environmental contaminants (Hanlon and Parris ), microbial skin communities (Bletz et al. ), seasonality (Longo et al.…”

Infrared spectroscopy detects changes in an amphibian cell line induced by fungicides: Comparison of single and mixture effects

“…The life cycle of amphibians usually encompasses reproduction and early development in the aquatic environment, meaning that this group of organisms may be susceptible to run-off from agricultural sources, such as pesticide application, which is often coincident with this sensitive period of development (Hanlon and Parris, 2014;Hayes et al, 2006;Mann et al, 2009). Such factors, in addition to the permeable skin of amphibians (Quaranta et al, 2009), mean that this group is a be a sentinel organism, indicative of early deterioration in environmental quality (Sparling et al, 2010).…”