Diminished Conspecific Odor Recognition in the Rusty Crayfish (Orconectes rusticus) Following a 96-h Exposure to Atrazine.

The presence of agricultural contaminants has been shown to disrupt olfactory-mediated behaviors in aquatic animals. We assessed the effects of atrazine on the ability of reproductively active (form I), male crayfish (Orconectes rusticus) to identify and respond to conspecific chemical signals involved in mating. Male crayfish were exposed to atrazine (80 ppb) and water (control) for 96 h. We analyzed odor localization and locomotor behaviors of herbicide-treated and control male crayfish to two different odor sources: female odor or water (control) delivered from the proximal end of a test arena. Control crayfish spent more time in the proximal region of the test arena and at the odor source. Atrazine-exposed crayfish showed no preference for the proximal region of the test arena and odor source when female odor was delivered. Atrazine exposure did not affect locomotor behaviors. Overall, atrazine-mediated chemosensory deficits have the potential to disrupt mating and affect population size.

Acute Atrazine Exposure has Lasting Effects on Chemosensory Responses to Food Odors in Crayfish (Orconectes virilis).

The herbicide atrazine is known to impact negatively olfactory-mediated behaviors in aquatic animals. We have shown that atrazine exposure has deleterious effects on olfactory-mediated behavioral responses to food odors in crayfish; however, recovery of chemosensory abilities post-atrazine exposure has not been investigated. We examined whether crayfish (Orconectes virilis) recovered chemosensory abilities after a 96-h exposure to sublethal, environmentally relevant concentrations of 80 ppb (µg/L) atrazine. Following treatment, we analyzed the ability of the crayfish to locate a food source using a Y-maze with one arm containing fish-flavored gelatin and the other containing unflavored gelatin. We compared the time spent in the food arm of the Y-maze, near the food source, as well as moving and walking speed of control and atrazine-treated crayfish. We also compared the number of crayfish that handled the food source and the amount of food consumed. Following 24-, 48-, and 72-h recovery periods in fresh water, behavioral trials were repeated to determine if there was any observable recovery of chemosensory-mediated behaviors. Atrazine-treated crayfish spent less time in the food arm, at the odor source, and were less successful at finding the food odor source than control crayfish for all times tested. Additionally, atrazine-treated crayfish consumed less fish-flavored than control crayfish; however, treatment did not affect locomotion. Overall, we found that crayfish are not able to recover chemosensory abilities 72 h post-atrazine exposure. Because crayfish rely heavily on their chemosensory abilities to acquire food, the negative impacts of atrazine exposure could affect population size in areas where atrazine is heavily applied.

Atrazine exposure affects the ability of crayfish (Orconectes rusticus) to localize a food odor source.

Environmental pollutants, found in aquatic ecosystems, have been shown to have an effect on olfactory-mediated behaviors including feeding, mate attraction, and other important social behaviors. Crayfish are polytrophic, meaning that they feed on and become prey for all levels of the aquatic food web as well as are also important for the transfer of energy between benthic and terrestrial food webs. Because crayfish are a keystone species, it is important to investigate any factors that may affect their population size. Crayfish are active at night and rely heavily on their sensory appendages (e.g., antennulues, maxillipeds, and pereopods) to localize food sources. In this experiment, we investigated the effects of atrazine (ATR) exposure on the chemosensory responses of male and female crayfish to food odors. We exposed crayfish to environmentally relevant, sublethal levels of ATR [80 ppb (µg/L)] for 72 h and then examined the behavioral responses of both ATR-treated and control crayfish to food odor delivered from one end of a test arena. We used Noldus Ethovision XT software to measure odor localization and locomotory behaviors of crayfish in response to food (fish) odor. We found that control crayfish spent more time in the proximal region of the test arena and at the odor source compared with ATR-treated crayfish. Furthermore, there were no differences in the time spent moving and not moving, total distance travelled in the tank, and walking speed (cm/s) when control and ATR-treated crayfish were compared. Overall, this indicates that acute ATR exposure alters chemosensory abilities of crayfish, whereas overall motor function remains unchanged.