Date of Award

Summer 2000

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Director

Alan H. Savitzky

Committee Member

Keith A. Carson

Committee Member

Kerry S. Kilburn

Committee Member

William A. Velhagen, Jr.

Abstract

Rhabdophis tigrinus, an Asian natricine snake, possesses a series of integumentary glands located in the nuchal skin. Previous studies indicated that the nuchal glands are of mesodermal origin, contain cardiac steroids analogous to bufotoxins found in the parotoid glands of toads, which are included in the snake's diet. The nuchal glands are defensive in function. Preliminary histological studies revealed differences in quality of the gland tissue compared to previous studies, and difference in fixation techniques were suspected. Seven specimens of R. tigrinus were fixed by perfusion using a conservative fixation process standard for electron microscopy. The nuchal gland series of specimens from toad-present and toad-free populations were studied, including those of males, females, adults, and one juvenile was studied. Series of nuchal glands were fixed, excised, and randomly sampled for cellular structure, in order to determine whether cardiac toxins are produced in the gland or sequestered from a diet of toads. Cellular morphology, including low numbers of steroidogenic mitochondria, polyribosomes, and evidence of pinocytotic activity along nuchal gland cell membranes strongly suggests that the steroidogenic compounds in the gland product are derived from the diet and sequestered in the nuchal gland. The variable quality of nuchal gland tissue appears to reflect the holocrine nature of the gland, as well as demonstrate the effects of fixation. There were no apparent histological differences between specimens from toad-present and toad-free localities. There appears to be a difference in the gland cells of the single juvenile specimen when compared to adult specimens at scale of light microscopy, although there does not appear to be a difference in the cellular structure under transmission electron microscopy. The results of this study do not refute the hypothesized mesodermal origin of the nuchal glands.

DOI

10.25777/m0ba-t576

ISBN

9780599965294

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