

SEASONAL MODIFICATIONS IN TESTES OF VERTEBRATES 



2-57 



From the above data it is almost impos- 

 sible to arrive at any positive conclusions 

 regarding cytological changes throughout 

 the year. Though Courrier, Champy, 

 and Van Oordt made observations on the 

 same species, Gasterosteus aculeatus, the 

 data offered are very meager and do not 

 cover the entire year. Much interpola- 

 tion is necessary. Chart I, which is 

 based on all available data, makes it quite 

 certain that the interstitial cells do not 

 promote the appearance of nuptial apparel 

 in this species. These cells develop after 

 maturity of spermatozoa. They increase 

 as the mating season closes and are most 

 abundant during the summer months, 

 when the testes contain no sperm. When 



intertubular tissue. Under certain con- 

 ditions some of the intertubular connective 

 tissue cells become modified into intersti- 

 tial cells. 



Anura generally breed in the spring, and 

 their eggs may be seen in ponds or along 

 the stream banks during high water of 

 early spring. Urodeles, however, breed 

 largely during midsummer and early fall. 

 Some may breed in spring. With each 

 species care must therefore be taken to 

 note the cytological modifications of the 

 testis and the anatomic and physiologic 

 peculiarities with reference to the actual 

 time of mating rather than to calendar 

 month or seasonal period of the year. 

 In most species spermatogenesis takes 



JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. 



CHART I GASTEROSTEUS ACULEATUS 

 - QUANTITY OF SPERMATIC TISSUE, • • « QUANTITY OF INTERSTITIAL TISSUE 



spermatogenesis again takes place they 

 decrease. They follow rather than pre- 

 cede mating and are abundant in the testis 

 when the tubules are empty. The latter 

 fact has been emphasized by Van Oordt, 

 who concludes from this relationship and 

 from the cytological changes taking place 

 in the interstitial cells that they are 

 trophic cells. He maintains that they are 

 abundant when the fatty material they 

 contain is not being consumed by develop- 

 ing germinal cells. 



MODIFICATIONS IN TESTES OF AMPHIBIA 



The structure of the amphibian testis 

 somewhat resembles that of the fishes. 

 The spermatogenic cells are found in cysts 

 and lobules, the latter being separated by 



place in the summer immediately after 

 mating and the spermatozoa are retained 

 in the testis and spermatic passages during 

 the winter. 



Friedman (15) found tubuli of Rana 

 fusca — now Pelobates fuscus — well filled 

 with spermatogonia at the end of March, 

 through April and May, and even in June. 

 The tubules are angular in outline at that 

 time from being pressed tightly together. 

 There is little room for intertubular 

 substance, and only blood vessels and con- 

 nective tissue cells are present between the 

 tubules. Toward the end of June, with 

 spermatogenic progress, interstitial cells 

 appear. In the fall, when all stages of 

 spermatogenesis are found, the intertubu- 

 lar spaces are richly filled with interstitial 



