Agonistic behavior enhances adult neurogenesis in male Acheta domesticus crickets

We examined the effect of agonistic behavior on cell proliferation and neurogenesis in the central nervous system (CNS) of adult male Acheta domesticus crickets. We combined 5-bromo,2'deoxyuridine (BrdU)-labeling of dividing cells with immunocytochemical detection of the neuronal marker horseradish peroxidase to examine the proliferation of progenitor cells and the survival of newborn neurons. In crickets, the mushroom bodies of the brain contain clusters of proliferative cells that divide and generate new neurons in adulthood. Pairs of male crickets were allowed to fight and establish social rank and were then injected with BrdU. Proliferation of mushroom body neurogenic cluster cells was unaffected by agonistic interactions; 24 h after a fight, the number of BrdU positive cells in fought and un-fought males did not significantly differ. However, agonistic interactions did influence cell survival. Two weeks after an agonistic interaction, fought males had more newborn neurons than males that did not fight. There was also a rank-specific effect because dominant males had significantly more new neurons than subordinates. We also report for the first time that neurogenesis in adult crickets can occur in other regions of the brain and in other CNS ganglia, including the terminal abdominal ganglion (TAG). Agonistic interactions enhanced the proliferation of these distributed precursor cells but did not increase the survival of the newborn neurons generated by these cells.