Attraction of Conspecifics to Molt Signals in Crayfish

ADAMS, J.A.*; MOORE, P.A.: Attraction of Conspecifics to Molt Signals in Crayfish

For many organisms olfaction plays a key role in communication. Crayfish use olfactory signals to find mates, warn of predators, and relay social status. While many of these situations have been studied in detail, behavior of conspecifics toward molted individuals has not. The physiology of crayfish changes dramatically during molting (ecdysis), which in turn changes both the content and concentrations of the chemical cues released into the water. We hypothesized that conspecifics would pick up these changes in chemicals released and move toward the molt signal. A Y-maze was used to test for a differential attraction to various odors presented to intermolt (non-molting) crayfish. All crayfish used were of the species Orconectes rusticus. The odor sources were molt crayfish, intermolt crayfish, aged tank water (control), or food (fish carrion). Variables measured included initial arm choice, time spent in each arm, walking speed toward source, meral spread, and straightness of path. On average, crayfish spent more time the presence of molt signals when paired with intermolt or control stimuli. The food stimulus was more attractive than over any of the other stimuli. These results demonstrate that there is a difference in the way a conspecific perceives a recently molted individual versus an intermolt individual. Since cannabalism and aggressiveness toward molted individuals has been observed in laboratory situations, the ability of a conspecific to recognize a molted individual by olfaction has implications for both social interactions and survival of individuals in crayfish populations.

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