Researchers at the California Institute of Technology (Caltech) and the University of California, San Diego (UCSD) have discovered that injecting a simple hormone into leeches creates a novel way to study how hormones and the nervous system work together to produce species-specific reproductive behavior.A paper describing the work appears in the March 11 online edition of the journal Current Biology.Daniel Wagenaar, Broad Senior Research Fellow in Brain Circuitry at Caltech and first author of the paper, found that injecting a particular hormone into a medicinal leech (Hirudo verbana) induced a series of movements that closely mimic natural reproductive behavior, including a stereotypical 180-degree twisting of the body.