Associative learning in male rusty crayfish (Orconectes rusticus): conditioned behavioural response to an egg cue from walleye (Sander vitreus)
Chemical communication governs a diversity of life processes in aquatic organisms. Crayfish use chemoreception during reproduction, social hierarchy formation, predation avoidance, and resource localization. Fish eggs release recognizable chemoattractants for vertebrate predators of
eggs that can motivate crayfish to engage in egg predation as well. We hypothesized that male rusty crayfish (Orconectes rusticus (Girard, 1852)) from a lake free of walleye (Sander vitreus (Mitchill, 1818)) would not possess an innate recognition of a walleye egg cue. However, if conditioned by employing a single 2 h paired stimulus exposure (known food cue + egg cue), then male rusty crayfish would be
attracted to the same egg cue upon subsequent exposure. Using a Y-maze behavioural arena we discovered that once conditioned, crayfish took significantly less time to choose the arm containing the egg cue alone relative to a control. Our study suggests that male rusty crayfish exhibit second-order
conditioning through associative learning, allowing them to quickly and easily learn to identify novel odour stimuli from fish eggs under laboratory conditions.