Reproductive Leech

Scientists have established common bloodsucking insect the leech as a model for a study of reproductive behavior, with some twisting and turning results. The researchers at the California Institute of Technology and the University of California, San Diego have discovered that injecting simple hormones into leeches creates a new way of seeing how hormones and the nervous system produce species-specific reproductive behavior. “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. Wagenaar’s studies were initiated at UCSD. The twisting, which occurs with a period of approximately five minutes — making it one of the slowest behavioral rhythms ever discovered, aside from diurnal and annual rhythms — serves to align the reproductive pores on the ventral (under) side of one leech with the complementary pores on the ventral side of a partner, thus facilitating copulation. Without this behavior, copulation would fail.”