Meeting Abstract
There is a great deal known about leech neuronal circuitry, however, their visual system has not been thoroughly studied. European medicinal leeches, Hirudo verbana, have 5 pairs of cephalic eyes and an additional 7 pairs of sensillar eyes along the surface of each mid-body segment. These cephalic eyes and sensilla contain photoreceptors that allow the leech to sense and respond to light. Recent work has shown that medicinal leeches display negative phototactic behavior when exposed to UV light—a portion of the electromagnetic spectrum between 395 and 405 nm— with a difference in the behavioral response of the leech depending on if the light was applied to the head or tail. Application to the head causes shortening and backward locomotion, while exposure to the tail causes forward locomotion. The circuitry and how UV light information is encoded underlying this negative phototactic response remains to be determined. We first characterized the animal’s behavioral response to varied intensities of UV light ranging from about half their normal environmental exposure to 4 times greater. Further, we recorded electrical activity resulting from the same light intensities applied to the sensillar photoreceptors. Raw data indicates a more negative phototactic response to higher intensities of UV light. In addition, there seems to be a difference in the electrical activity between different intensities of UV light as well.
