Date of Award

Summer 1992

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Robert K. Rose

Committee Member

Deborah Waller

Committee Member

Keith A. Carson

Call Number for Print

Special Collections LD4331.B46 D49

Abstract

Winter survival mechanisms in the southern short-tailed shrew, Blarina carolinensis, were studied by examining cellular changes in interscapular brown adipose tissue (ISBAT) and pelage characteristics in specimens collected each month of the year in eastern Virginia. On capture, each specimen was anesthetized with ether and then perfused with a 2.5% glutaraldehyde-2% formaldehyde solution. ISBAT tissues were examined histologically with the transmission electron microscopy. Because BAT is know to produce heat by nonshivering thermogenesis and is more developed in winter animals than summer animals, it was hypothesized that mitochondrial area of BAT would be relatively greater in winter than in summer. Measurements of the areas of mitochondria, lipid droplets, nuclei and blood vessels were made using a digital measurement system and the SigmaScan computer program by Jandel. The percentages of total cell area occupied by mitochondria and lipid droplets were calculated by dividing the total organelle area by the quadrant area minus blood vessel area, thereby giving a percentage value per cell for each micrograph. A two-sample student's t-test was used to determine differences between winter and summer tissues. Both the percentage of cell occupied by mitochondria and maximum mitochondrion size were greater in winter shrews than in summer shrews. The inverse was true for the lipid droplets; both the percentage of cell area occupied by lipid droplets and the maximum lipid droplet size were greater in summer shrews than in winter shrews.

Skins from shrews which died in the traps, when no time of death could be established, were pinned flat, and later shaved, marked into 1-mm2 grids, and prepared for scanning electron microscopy. Counts of hair follicles were taken from each grid and then an average count was made for each individual. Individual hairs were also removed and mounted for length measurements using a micrometer eyepiece. There were no seasonal differences in hair density. Type I guard hairs and Type II guard hairs were significantly shorter in the summer than those of the other three seasons (1.3 times shorter in summer than in winter). Even though there was not a significant seasonal difference in the length of woolly hairs, the summer woolly hairs were 1.2 times shorter than winter hairs.

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DOI

10.25777/vc1b-3a35

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