Doctoral Dissertations

Date of Award

8-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

Gerald L. Vaughan, Thomas G. Hallam

Committee Members

Jim Hall, Gary McCracken, James Lawler

Abstract

My research objective was to investigate the detection of atmospheric pressure as a sensory modality in flying animals. For flying animals, atmospheric pressure is a potential source of information that might be used as the basis of a pressure altimeter and / or meteorological forecasting. The prominent properties of variation in atmospheric pressure are absolute pressure magnitude and the rate of pressure change. Absolute pressure magnitude is a reliable indicator of altitude while pressure changes can be separated into two types; rapid changes associated with altitude changes in flight and relatively slow changes associated with meteorological events. A prerequisite for an animal to have a functional response to variation in atmospheric pressure is that the animal be able to detect the variation. I have demonstrated that insectivorous bats are able to detect and respond to the atmospheric pressure changes associated with flight altitude changes and meteorological events using behavioral assays. In laboratory tests, individuals of three species demonstrated spontaneous responses to induced atmospheric pressure changes that are equivalent to a 35m altitude change over 15 seconds. Monitoring of wild bat foraging activity demonstrated that wild bats might use atmospheric pressure changes associated with storm fronts to avoid poor flying conditions. The paratympanic organ is a putative atmospheric pressure receptor. In the avian paratympanic organ, it has been suggested that air pressure changes induce conformational changes that stimulate mechanoreceptors in the sensory epithelium via fluid displacement. Using microscopy techniques, I discovered that the lumen of the paratympanic organ is not just a fluid- filled space. The lumen of the paratympanic organ is filled with an extracellular collagenous matrix that is an apparent accessory structure. I propose that the function of the paratympanic organ matrix is to couple conformational changes in the paratympanic organ with the mechanoreceptors in the sensory epithelium, a function analogous to that of other accessory structures in the lateral line system. My anatomical survey of individuals from 11 bat species failed to confirm a previous report of a bat paratympanic organ.

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