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THE PHYSIOLOGICAL AND MORPHOLOGICAL BASIS FOR OLFACTORY PERCEPTION OF STEROIDS DURING AGONISITC BEHAVIOR IN LOBSTER
Citation:
Horowitz, D B., K. Randall, A. Fini, M. Boseman, D. L. Coglianese, G. KassSimon, AND S. Cromarty. THE PHYSIOLOGICAL AND MORPHOLOGICAL BASIS FOR OLFACTORY PERCEPTION OF STEROIDS DURING AGONISITC BEHAVIOR IN LOBSTER. Presented at 30th Annual East Coast Nerve Net Conference, Woods Hole, MA, April 2-4, 2004.
Description:
During fighting, American lobsters urinate on each other with antennule flicking highest during this period. Blocking excretion of urine obliterates previously established dominance relationships, suggesting that individual recognition requires a urine signal (Breithaupt et al., 1999). While some research focuses on various "signal peptides" in the urine, it is our hypothesis that the steroid hormone, 20-Hydroxyecdysone (20-HE) plays a major role in signaling an opponent?s aggressive state (Cromarty et al., 2001).
Hemolymph and urine concentrations change over the molt cycle with the highest ecdysteroid concentrations found in aggressive premolt (Snyder and Chang, 1990 1991). This coincides with the findings of differences in agonistic behavior of lobsters over the molt cycle (Tamm and Cobb, 1978, Cromarty et al., 1991) and with the differential effects of pre- and post-molt hemolymph on EJPs size of the claw opener muscle (Schwanke, et al., 1990). Hemolymph injections of 20-HE have been shown to increase the aggressiveness of lobsters in agonistic encounters (Bolingbroke and Kass-Simon, 2001) and to increase EJP amplitude and MEJP frequency in the claw opener muscle (Cromarty & Kass-Simon, 1998).
Physiology: Our experiments indicate that perfusion of 20-HE over lateral antennule filaments, causes large-scale excitation of individual olfactory receptor neurons (ORNs) in the Spiny lobster, Panulirus argus and the American lobster, Homarus americanus. Inactive forms of the steroids or controls have significant lower levels of excitation. Our current experiments suggest that while 20-HE does indeed evoke responses in the olfactory receptor neurons, other steroids may also be involved in signaling state (Cromarty et al., 2001).
Morphology: Preliminary experiments and protocol refinement suggest that it will be feasible to search for ecdysteroid receptors (both intracellular and membrane bound) using histochemical and immunohistochemical staining techniques to characterize and localize 20-HE and alpha-ecdysone (the precursor to 20-HE) receptor sites in the main olfactory sensors of the lobster.
Results from these studies so far suggest that steroids alter not only the internal state of an animal, but are also used by lobsters as signaling tools with which to orchestrate agonistic strategies.