Date of Award

1968

Document Type

Thesis

Degree Name

Master of Arts (M.A.)

Department

Biological Sciences

First Advisor

Anne Funkhauser Mathias

First Committee Member

John S. Tucker

Second Committee Member

Walter Hewitson [?]

Abstract

Oxygen consumption can most readily be related to wet weight. However, the weight of a tadpole increases so long as it is feeding, then decreases during final non-feeding stages. Oxygen uptake may also be related to dry weight, but dry weight increases significantly from early tadpole stages to adult (Funkhouser and Mills, in press). There is change in one factor at the same time the change in the the other factor is in the opposite direction. Total nitrogen content may be used as an index of the metabolizing tissue, but is subject to the same criticism as dry weight (Moore, 1964). Ideally, the animal's respiration should be related to as many criteria as possible. The pattern of thyroid activity during amphibian metamorphosis has been described by a number of investigators using a variety of methods. Histological criteria for the functional activity of the thyroid glad include epithelial cell height, the number of epithelial cells in serial sections of gland, "vacuolization" of the colloid, the number of secretion droplets present in the follicle, the number of mitochondria, and changes in the size of the Golgi apparatus. Not all of these criteria are considered to be of equal validity (Etkin, 1930; Gorbman and Bern, 1962).

The amount of iodine accumulate in the follicle has been used as an index of the activity of the gland. Kaye (1961) using radioactive iodine (I131) and radioautography found a 12% increase in I131 accumulation during early metamorphic stages, and a 43% increase during or near the later stages of metamorphosis. The rate of development is significantly increased in normal tadpoles immersed or injected with thyroxine. Kollros (1961) was able to reproduce the normal metamorphic pattern in thyroidectomized Rana pipiens with gradually increasing concentrations of T4. All of these studies indicate that during normal metamorphosis there is a gradual increase in the concentration of thyroid hormone reaching a climax in the last stages and dropping metamorphosis has been assumed to increase because the increase in thyroxine levels accompanying metamorphosis in amphibia would be sufficient to cause a marked increase in metabolic rate in mammals. The latent period between exposure to thyroxine and maximum calorigenic effect has been described for many animals, In man this period is about two weeks (Guyton, 1964).

The present study was designed to show that the small increase in oxygen uptake observed in a number of amphibians during metamorphic climax (Table II) is the result of the increase in thyroxine levels in the immediately preceding stages. Oxygen consumption of Hyla regilla was measured from hatching through metamorphosis and correlated with activity of the thyroid gland

Pages

43

Included in

Biology Commons

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