CASKEY, J.L.; BAUER, R.T.; Univ. of Louisiana, Lafayette; Univ. of Louisiana, Lafayette: Behavioral Tests of a Contact Pheromone in Male Recognition of Receptive Females in the Shrimp Palaemonetes Pugio

Palaemonetes pugio is a small estuarine shrimp found along the Atlantic and Gulf coasts. Males recognize (suddenly attempt to grasp and to mate) newly molted (postmolt) parturial females upon contact of their chemotactile antennal flagella with any part of the female cuticle. Our objective was to determine if male sexual attraction to postmolt, prespawning parturial females is due to visual, chemical, or textural cues (a soft cuticle). Males allowed visual but not direct contact with sexually attractive females did not respond with copulatory behavior. We tested the nature of the chemotactile stimulus by exposing males to (a) postmolt females with mature ovaries, (b) premolt females with mature ovaries, (c) postmolt females with immature ovaries, (d) intermolt females incubating embryos, and (e) postmolt males. Postmolt individuals have a soft exoskeleton while premolt and intermolt individuals have hard ones. Males only responded with sexual behavior (grasping, copulation) to postmolt females with mature ovaries and with a slight positive response (following) to postmolt females with immature ovaries. Male response to postmolt females with mature ovaries was tested as a function of time after the female molt using time-lapse video observations. There was a gradual decrease in attractiveness of postmolt parturial females to males from 0-8 hours after the female molt. Our results indicate that males detect receptive females by a nonsoluble substance on the newly molted female cuticle that degrades or changes rapidly with time from the molt. The texture (softness) of the newly molted exoskeleton is not a stimulus. The pheromone appears to be perceived by contact chemoreceptive (taste; gustation) sensilla on the male second antennae.