Research Description
Sensory capabilities underlie the behavior of any organism. My research focuses on understanding mechanosensory phenomena utilizing a model crustacean system. I am examining the relation between physiological and structural properties of a mechanosensory system and its relation to the behavior and ecology of the organism possessing it. Working on marine copepods, an important group in marine ecosystems, my collaborators and I have found exceptional mechanosensitivities (in the nanometer range, close to vertebrate ear capabilities), exceedingly fast reaction times (1 msec), and unusually high power-output rates associated with the sensory-triggering of behavioral (escape) reactions.
Studies on sensory mechanisms involve electrophysiological recordings of primary afferent discharges from mechanoreceptors. Research includes investigation of sensitivities and timing relations in sensory responses. Mechanisms for extremely high-frequency (5 kHZ, higher than most mammals) nerve impulse firing capabilities are under investigation.
Structure-function approaches are being used in studies of sensory transduction. Unusual rigidity of sensory structures derived from dense microtubule elaboration helps explain the high mechanical sensitivities and exceptional frequency response of receptors.
Escape responses ("jumps") triggered by abrupt mechanical stimuli are a primary focus of behavioral investigations. Reaction times have been correlated, among different species, with morphological adaptations for increasing nerve impulse propagation speed, including the development of myelin. Studies on the energetics of the behavioral reaction have been pursued through kinematic measurements and modeling of the biomechanical components of the escape swim system.
Bioluminescence, triggered by strong mechanical stimulation in certain deep-sea copepods, is another predator-evasion response being investigated. Simultaneous recording of the forces produced during kicks with the light produced in bioluminescence permits a comparison of triggering conditions and timing for the two different responses.
These studies are providing insights into the exceptional physiological capabilities of organisms under strong evolutionary selection pressure. They are leading to the discovery of novel design principles for both sensory and motor systems in a model organism capable of high performances. They are helping explain the extraordinary success of the copepod group in penetrating so many ecological niches in the aquatic environment.