Atrazine exposure shifts activity but has minimal effects on courtship in an agrobiont spider.

The behavior of many animals relies upon the input of chemical signals throughout the environment. Those animals that live in close proximity to humans may then be at risk, as the input of anthropogenic chemicals can have significant sublethal effects by masking or altering these naturally occurring signals. While the herbicide atrazine has been found to have the potential to alter such chemical information, research is lacking on how it may impact agrobiont arthropods which are the first and most direct line of exposure. Here we investigated the sublethal effects atrazine may be playing on an agrobiont wolf spider that makes up a major component of agricultural spider communities in the Eastern United States. We exposed spiders to ecologically relevant doses of atrazine and monitored general activity patterns as well as mating behaviors. We found that while sex determined a large portion of activity variation in these predators, both males and females spent more time mobile but at lower speeds in the presence of atrazine. We did not find any evidence for info-disruption based on male courtship rate and mating success, but with increasing dosage of atrazine came shortened bouts of courtship leading to copulation. These results suggest that atrazine changed activity patterns of a wolf spider, which may result in altered foraging, survival, and reproduction.

Impact of an atrazine-based herbicide on an agrobiont wolf spider.

For animals that live in association with humans, a key ecological question is how anthropogenic factors influence their life history. While major negative effects are obvious, subtle non-lethal responses to anthropogenic stimuli may provide insight into the features that lead to the success of species that thrive in habitats heavily impacted by humans. Here we explored the influence of the herbicide atrazine on various life history traits of a wolf spider that thrives in agroecosystems where it is commonly applied. We found that exposure delayed maturation and increased the probability of having molting errors. Atrazine also decreased the probability of producing an egg sac after mating, but increased the average mass of the initial egg sacs that were produced while not impacting the average number of eggs inside. The total number of eggs produced from a single mating on the other hand, was increased in the presence of atrazine through the production of multiple egg sacs. Finally, adult lifespan was shortened with exposure to atrazine. These results suggest that the atrazine based herbicides that are routinely applied to agricultural fields result in altered life history traits, potentially through endocrine disruption, that may counteract one another to allow persistence.