Award Date

8-1-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Committee Member

Carl L. Reiber

Second Committee Member

Megan Litster

Third Committee Member

Michelle Elekonich

Fourth Committee Member

Stephen Roberts

Fifth Committee Member

Jack Young

Number of Pages

129

Abstract

Aquatic poikilothermic animals must either cope with or compensate for the mismatch in oxygen supply and demand present at high temperatures. Oxygen limited thermal tolerance explains how aerobic scope is limited by insufficient oxygen supply and sets the performance window in animals. This work explores the effects of temperature on the different components of the oxygen delivery system, in both normoxic and hyperoxic conditions to determine if supplying more oxygen to the system mitigates the effects of temperature effects on the cardiorespiratory system and extends oxygen limited thermal tolerance to higher temperatures. The effect of temperature and oxygen condition was measured on both the whole organism and system level. Critical thermal maxima (CTmax) were established in both normoxic and hyperoxic conditions to determine if the mismatch in oxygen supply and demand could be mitigated by supplying more oxygen to the system. (CTmax) was higher in hyperoxia than normoxia indicating failure was not related to a specific temperature. Ventilatory measurements were made through the development of a novel high speed video microscopy method to measure ventilatory volumes in small aquatic crustaceans. Temperature had a significant effect on all ventilatory parameters measured including scaphognathite stroke volume, ventilatory rate, and ventilation volume. Hypometabolism and hypoventilation were observed in the hyperoxic condition compared to the normoxic condition. This may be a mechanism to save the cost of energy expended for ventilation. Cardiac parameters including heart rate, stroke volume, and cardiac output were also measured using high speed video microscopy. Heart rate exhibited a temperature dependent tachycardia as did increase in cardiac output, but stroke volume was temperature insensitive. There was a significant effect of oxygen condition on stroke volume with a higher stroke volume in hyperoxia. Analysis of pressure data for time in cardiac cycle points to a biomechanical limitation leading to cardiac failure. Cardiac measurements were expanded using integrated micropressure signals and high speed video microscopy to measure intracardiac pressure and cardiac volumes respectively to generate pressure-area loops. The change in pressure (∆ P) is reduced at high temperatures in hyperoxia compared to normoxia leading to a reduction in stroke and cardiac work in hyperoxia. This reduction in cardiac work leads to cardiac failure at higher temperatures in hyperoxia than normoxia. This data also provides further support of a biomechanical limitation of diastolic filling time leading to cardiac failure at high temperatures.

Keywords

Cardiovascular system; Cold-blooded animals; Crustacea; Crustacean; Oxygen consumption (Physiology); Oxygen limited thermal tolerance; Palaemonias; Temperature; Ventilatory

Disciplines

Biology | Marine Biology | Physiology

Language

English


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