EXPOSURE TO THE HERBICIDES ATRAZINE AND METOLACHLOR AFFECTS THE CHEMOSENSORY DISCRIMINATION OF FEMALE ODORS BY MALE CRAYFISH (ORCONECTES RUSTICUS)

Sabhapathy, Gita, Sana Khan, and Rachelle Belanger

The presence of environmental pollutants has been shown to have an effect on olfactory-mediated behaviors in aquatic animals. Previous research demonstrates that exposure to the herbicides atrazine and metolachlor affects social signaling during agonistic encounters, localization of food and responses to alarm cues. Crayfish are a keystone species and play an integral role in energy transfer between benthic and terrestrial food webs and thus healthy crayfish populations are vital for sustainability in the systems they inhabit. Male crayfish rely on the presence of chemical signals, released from reproductively active females, in order to locate those females for mating purposes. In this study, we exposed form I (reproductive) male crayfish to ecologically relevant, sublethal levels of atrazine (80 ppb), metolachlor (80 ppb), an atrazine and metolachlor mixture (80 ppb of each) and water only (control) for 96 hours. We analyzed the behavioral reactions of herbicide-treated and control form I male crayfish to two different odor sources: reproductive female-conditioned water or water (control) delivered from one end of a test arena. We measured odor localization and locomotory behaviors of male crayfish in response to female odors and water (control) from all treatments. Crayfish that were not exposed to the herbicides spent more time closer to a reproductive female odor source, whereas crayfish in all herbicide exposure treatments showed no preference for the female odor. Further, control crayfish had an increased walking speed (cm/s) when female odor was present in the test arena. Male crayfish treated with atrazine and metolachlor showed no significant increases in walking speed when female odor was delivered. We conclude that sublethal concentrations of atrazine and metolachlor interfer with the ability of crayfish to receive or respond to reproductive signals and thus may negatively affect population growth and the ecosystems they occupy.