Ronita Dua, “Olfactory Receptor Placement in Daphnia”
Mentors: J. Rudi Strickler and Dave Spade, Biological Sciences
Poster #47

Organisms can respond to alterations in their physical and biological environments due to sensory inputs to their CNS. These inputs are often passed to it through receptors sensitive to specific stressors. While the very definition of a typical receptor explains as it being exposed to its stressor, Daphnia exhibit some unique sensory specializations unlike those seen in any other. Daphnia have their olfactory receptors hidden away inside the rostrum, a pyramidal cavity just below the eyespot. Though a series of experiments we found that this interesting placement of their receptors relates not only to the organism’s locomotory cycles but also to the general patterns of water flow around it. In our experiments, we tracked the motion of the organism while simultaneously tracking the flow in its environment using the movement of the hollow glass spheres suspended in it. Analyzing the two concomitant motions provided an explanation for the receptors’ placement. We saw that the pyramidal rostrum moved opposite to the flow of water enriched with olfactory cues or food particles, enabling it to trap them as the Daphnia continued with its characteristic hop-and-sink locomotion. Coordinate tracking of the animal also showed that single-daphnia dynamics can be modelled effectively with fairly simple time-series processes. This, alongside the positional analysis of the organism and the flow around it help us understand and provide an explanation for the unique placement of Daphnia’s olfactory receptors.