Rachel Schulz

Dopamine is an important neuromodulator that alters many sensory and motor systems. To better understand the role of dopamine in sexual dimorphism and species-specific behavior, we focused on cricket acoustic signaling for a mate. In many cricket species, males produce songs to attract a female to mate. We examined whether the architecture and numbers of dopamine-labeled neurons differed across the nervous systems of males and females in the local ground cricket species, Allonemobius allardi. To label dopamine neurons, we used a highly specific monoclonal antibody to tyrosine hydroxylase, which is the rate-limiting enzyme for the synthesis of dopamine. We found that this labeling protocol allowed for a highly detailed visualization of individual dopaminergic neurons in the brains and nerve cords of male and female A. allardi. Dopamine innervation in the prothoracic ganglion, abdominal ganglia, and subesophageal ganglion is conserved across male and female A. allardi. Sexually dimorphic dopamine innervation was greatest in the terminal abdominal ganglion. Males have more dopamine innervation in the terminal abdominal ganglion, and also have commissures showing heavily fasciculated tracks of dopamine neural fibers traveling across the ganglion. In females, these commissures show much less fasciculation of neural fibers traveling across the ganglion. This is the first study in the cricket A. allardi to characterize dopaminergic neurons in the CNS. To our knowledge, it is the first study in any cricket species to use confocal microscopy to visualize dopaminergic neurons. Future studies should address how dopamine regulates sexually-dimorphic behaviors involving reproduction and song detection.