Contrasting behavioral responses by detritivorous and predatory mayflies to chemicals released by injured conspecifics and their predators

Larvae of the mayfly Siphlonisca are predators of the detritivorous mayfly Siphlonurus in floodplain wetlands in Maine (USA). Both mayflies are natura l prey of brook trout (Salvelinus fontinalis). Ne exposed larvae of Siphlon urus and Siphlonisca to chemicals from injured conspecifics and their preda tors. Significant decreases in movement activity by Siphlonurus were elicit ed by chemicals released from Siphlonisca, chemicals released from brook tr out fed conspecifics, and by chemicals released from injured conspecifics. A significant decrease in movement activity by Siphlonisca was elicited by chemicals released from brook trout fed either conspecifics or Siphlonurus. Movement activity by either Siphlonurus or Siphlonisca was not significant ly affected by chemicals released from trout feeding on brine shrimp (Artem ia). Both Siphlonurus and Siphlonisca were able to detect chemicals that pr ovided information about past feeding behaviour by brook trout. However, th eir response to the chemicals used in this study was context-specific. A re duction in movement activity, a behavior that presumably reduces the probab ility of being consumed by visual predators, occurred only when mayflies we re exposed to chemicals released by brook trout feeding on conspecific (Sip hlonurus) or confamilial (Siphlonisca) prey.