Tailflick escape behavior in larval and juvenile lobsters (Homarus americanus) and crayfish (Cherax destructor).

We examined the escape behavior of larvae and postlarvae of the American lobster (Homarus americanus) and of adult immature (stage ADI) crayfish (Cherax destructor). Responses to standardized water jet stimuli delivered through a pipette were observed and analyzed. Lobster larvae did not respond to stimuli within 60 ms, indicating that they do not have functional giant fibers. The first movement by lobster larvae in response to water jet stimuli was a hyperextension of the abdomen. Larval escape responses also showed very little habituation. Postlarval lobsters and ADI crayfish showed the same range of responses as adult animals. Displacement efficiency of tailflicks exhibited by the different animals and stages was examined and related to the morphology of the animals. A separate behavior from tailflicking by larval lobsters in response to water jet stimuli was also observed. Here, the abdomen was hyperextended and the thoracic appendages were promoted. We termed this behavior a "starburst" response. The features of the tailflicking behavior suggest that it evolved to make the larvae difficult prey to handle for small, slower moving predators, and possibly to allow them to ride the bow waves of faster moving predators.