The Effect of Thiourea, Administered by Immersion of the Maternal Organism, on the Embryos of Lebistes Reticulatus, With Notes on the Adult Gonadal Changes

The adult thyroid of Lebistes reticulatus after exposure, by immersion, to a 0.04% thiourea solution displayed an extreme hyperplasia. An increase in follicle size and number and their establishment in abnormal areas took place. The heart kidney, spleen, and intestines were invaded by the thyroid epithelial cells. The mean height of the follicular cells of the fish receiving the shortest thiourea treatment increased approximately 130%. With longer periods of exposure to thiourea greater heights were produced. 2. The thyroid gland of the newborn of thiourea-treated females had undergone hyperplasia and metastasis during ontogeny. The thyroid became afollicular, lost colloid and possessed tall epithelial cells. Hearts, kidneys, spleens and intestines harbored the invading cells. A transfollicular transmission of an agent causing these changes took place. 3. Lebistes reticulatus, while not having an anatomical uterus, placenta or other means of attaching the developing embryo firmly to a part of the adult female reproductive system, does have maternal and embryonic modifications which permit an exchange of material. The species is therefore not a true ovoviviparous form. 4. The gametogenic function of the adult ovary was suppressed by thiourea administration as evidenced by abortions, decrease in brood size, longer brood intervals and smaller than normal number of ova in the gonad. This finding may be a reflection of a decreased gonad-stimulating hormone titer. The latter may be due to a shift to a greater thyroid-stimulating hormone production at the expense of a gonad-stimulating hormone by the pituitary.