HIGH TEMPERATURE TOLERANCE AND THYROID ACTIVITY IN THE TELEOST FISH, TANICHTHYS ALBONUBES

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Abstract
The thyroid of this fish was rendered hypofunctional by 30-40 days'' immersion in 0.05% thiourea. This treatment affected the thyroid histology to a significant degree, resulting in hyperemia, follicular hyperplasia, and cellular hypertrophy with a loss of stored colloid. After each group had been acclimated at 15.0[degree]C, the upper lethal temperatures were determined for the thiourea-treated and control fish. The upper lethal temperature of the controls was 31.0[degree]C and that of the experimentals was 30.0[degree]C. This indicates that in this species decreased thyroid function does not result in increased high-temperature tolerance but, in fact, slightly decreases it.