Browsing by Author "Takahashi, Hiroya"
A comparison of the annual changes in testicular activity and serum androgen levels between the early and delayed maturing groups of male Cottus hangiongensis Annual changes in testicular activity and concentration of two serum androgens were monitored in two groups of the river-sculpin Cottus hangiongensis collected from the upper and lower reaches of a river at southern Hokkaido, Japan. One of them (early maturing group) underwent testicular maturation with aberrant spermatids and spermatid masses produced during the reproductive cycle. Moreover, regular seasonal changes in serum testosterone and 11-ketotestosterone concentrations were observed. On the other hand, in the other group (delayed maturing group), although body size of the fish was large enough to undergo reproduction, annual changes in gonadosomatic index and testicular activity did not vary much. During the months of active testicular development in the early maturing group, spermatogenesis was observed to begin in some regions of the testes of delayed maturing fish, but always resulted in the formation of aberrant spermatids and spermatid masses. Moreover, concentration of serum androgens did not significantly vary throughout the year. Results suggest that low androgen production is a proximal factor for delayed sexual maturity in the delayed maturing group, and that the occurrence of aberrant spermatids and spermatid masses during spermatogenesis is not linked to the delayed maturity.
An ultrastructural study on the occurrence of aberrant spermatids in the testis of the river sculpin, Cottus hangiongensis GF Quinitio & H Takahashi -
Japanese Journal of Ichthyology, 1992 - The Ichthyological Society of JapanThe process of spermatogenesis and spermiogenesis in the river sculpin,Cottus hangiongensis, was observed ultrastructurally. During spermatogenesis, some germinal cysts in the seminal lobules were found to contain spermatocytes, which were provided with irregularly shaped nuclei, doughnut-shaped mitochondria, and atypical intercellular bridges with multiple disk-like cisternae. In addition, many cysts containing binuclear spermatids were observed in the testis. Within the condensed chromatin of the paired nuclei of the aberrant spermatids, highly electron-dense granules occurred, becoming the core of successively developing chromatin globules. The chromatin globules increased in size, resulting in an enlargement of the paired nuclei. These cells were finally released from the cyst into the lumen of the seminal lobules and underwent further degeneration, thus appearing as characteristic ‘spermatid masses’ in the mature testes.