Award Date

8-1-2022

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Life Sciences

First Committee Member

Frank Van Breukelen

Second Committee Member

Allyson Hindle

Third Committee Member

Jenifer Utz

Fourth Committee Member

Edwin Oh

Number of Pages

82

Abstract

Common tenrecs are the largest species within the family Tenrecidae and are endemic to Madagascar, a vast and hypervariable landscape. Malagasy tenrecs undergo hibernation for several months during the Austral winter but use burrows during their active and hibernation seasons. Previously normoxic and normocapnic (20.95% O2, 0.04% CO2) experiments on active and hibernating tenrecs have shown the bizarre nature of tenrec aerobic metabolism. Active tenrecs have up to a 25-fold variation in resting oxygen consumption (V̇O2), with values similar to a hibernating tenrec V̇O2 up to values typical for most mammals. Regardless of physiological state and ambient temperature, tenrec resting V̇O2, body temperature (Tb), and heart rate (HR), intimately associated physiological variables, are not well connected. Further, tenrecs may hibernate socially within a completely enclosed burrow. Such circumstances may produce abiotic stresses, mainly hypoxic (< 20.95% O2) and hypercapnic (> 0.04% CO2) environments. This brings into question the hypoxic and hypercapnic tolerances of common tenrecs. Active animals were exposed to increasingly hypoxic (16 to 4% O2) or hypercapnic (2 to 10% CO2) exposures followed by a return to normoxia and normocapnia in ambient temperatures (Ta) of 16 and 28°C, while responses in V̇O2, Tb, and HR were measured. Separate experiments exposed active tenrecs to 16 or 7% O2 followed by a return to normoxia to measure decreases in Tb mediated by hypoxia in an attempt to compare responses to endothermic mammals. Tenrec responses to either stressor appear partially dependent on Ta. Active tenrecs depressed V̇O2 by 57.9-69.8% in 7% O2 and by 62.1-69.9% in 4% O2 environments at 16°C. Progressively hypercapnic conditions at 16°C depressed V̇O2 by 62.9-82.4% when animals reach 10% CO2 treatment. Tenrec Tb reached a 4.74°C decrease after 4 h of 7% O2 exposure, but this most likely resulted from passive measures, a stark contrast in strategy compared to endothermic mammals. Reductions in tenrec V̇O2 as a response to 7% O2 or increasingly hypoxic or hypercapnic conditions are followed by higher V̇O2 variability between tenrecs during recovery periods, meaning animals depress V̇O2 with minor coordination between processes at 16°C. Common tenrecs do not markedly modify V̇O2 and instead may rely on ventilation and/or vasodilation changes at 28°C which may explain a small decrease in Tb seen at 4% O2 and 10% CO2. Ultimately, active common tenrec V̇O2, Tb, and HR remain partially disconnected in strenuous environments with Ta dependent responses that are possibly ancestral strategies for a placental mammal.

Keywords

Ambient temperature; Body Temperature; Hypercapnia; Hypoxia; Oxygen consumption; Tenrec

Disciplines

Biology | Medical Physiology | Physiology

File Format

pdf

File Size

10600 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

Download

Available for download on Sunday, August 15, 2027


Share

COinS