Environmental determinants of escape reflex performance in a freshwater oligochaete

Abstract

This manuscript has been reproduced from the microfihn master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from airy type of computer printer.The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrougb, substandard margins, and inq)roper alignment can adversely affect reproduction.In the unlikely event that the au±or did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book.Photogr^hs iacluded in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. In Char^] of Major Work Iowa State University Ames, Iowa 1995Signature was redacted for privacy.Signature was redacted for privacy.Signature was redacted for privacy.Signature was redacted for privacy. GENERAL INTRODUCTIONIn purely physical or mechanical systems, a stress or force induces a strain. Similarly, from a physiological standpoint, an environmental stress induces a strain on an organism that must be compensated for or tolerated. Each of the five chapters in this thesis addresses the effect of an environmental stress on touch-evoked rapid escape reflexes in aquatic oligochaetes-Chapter one will assess the lethal limits of dissolved cadmium and will relate these limits to sublethal pre-treatment with cadmium.Chapter two will assess the effect of acute and prolonged exposure to anoxia on escape reflex function. Chapter three will assess the lethal limits and sublethal effects of pH and amiaonia/ammonium exposure. Chapter four will assess the effect of temperature, both acute and prolonged exposure, on 3 escape reflex function. Chapter five will assess the effect of repeated tactile stimulation on escape behavior and, although it represents a sensory cue more than a stress, it is included because repeated tactile stimulation routinely occurs within the worm's environment. These particular stresses were chosen because of their relevance to the freshwater environment and worm's survival within that environment.The specific effects (strains) to be examined are the changes in the physiological performance of selected components of the escape reflex including: touch sensitivity, giant fiber conduction velocity, and giant fiber-mediated muscle electrical potentials. Touch sensitivity is a measure of...