Jess Breda; William Kristan; Kathleen French, Westminster College
A long-standing hypothesis in the field of neuroethology has been that organisms performing similar behaviors use similar underlying neuronal circuitry. Recently, though, studies focused on locomotion have shown that this may not necessarily be true. Work in sea slugs has demonstrated that homologous behaviors can be generated by a variety of neuronal connections. Our work looks at reproductive behaviors and asks whether those behaviors are mediated by the same neuronal connections in two species of leech. Research in Hirudo verbana has shown that reproduction is mediated by a neurohormone, hirudotocin, that is stored in and is released from a circuit of characterized neurons called Leydig Cells. A second leech, Macrobdella decora, has the same reproductive strategy as H. verbana, including a similar progression of behaviors. Using immunohistochemistry, we have identified Leydig Cell homologs in M. decora. Additionally, when we inject either M. decora or H. verbana with a hormone similar to hirudotocin, we observe reproductive-behavior output that is nearly identical. We intend to compare these species further by fully characterizing the Leydig Cell network using electrophysiology. These results will clarify the relationship between reproductive behavior and neuronal circuitry in leeches and give insight as to how neural circuits evolve across species.