1038 



SUBMAMMALIAN VERTEBRATES 



partly obscured, before spawning, by the 

 crowding and distention of the testis with 

 sperm.- Follenius (1953) showed that if 

 prepubertal Lebistes are exposed to x-rays 

 the testes become completely sterile and 

 Sertoli cells are also destroyed, but second- 

 ary sex characters nevertheless develop on 

 schedule. Since the interstitial cells are the 

 only functional tissue remaining, this ex- 

 ])criment is strong evidence for origin of 

 androgen from these cells. In several tele- 

 osts in which intersitial cells are not seen, 

 there are specially developed cells in the 

 wall of the testicular lobule or crypt (Hoar, 

 1957b; Marshall and Lofts, 1956). When 

 the spawning season approaches, these 

 "lobule boundary cells" acquire fat inclu- 

 sions, give a positive test for cholesterol, 

 and generally resemble the interstitial cells 

 of higher vertebrates. 



Amphibians 



There are conflicting opinions as to 

 wiiether androgen is produced by the in- 

 terstitial cells of the amphibian testis. In- 

 deed, it is likely that the term "interstitial" 

 is not appropriate in this case. The urodele 

 testis does not have seminiferous tubules, 

 l)ut rather seminiferous lobules or cysts 

 (Perez, 1921). Between the lobules there 

 are only thin layers of connective tissue 

 which, according to Perez, is not at all 

 homologous with the interstitial tissue seen 

 between the seminiferous tubules of higher 

 vertebrates. 



Aron (1924a, 1926), on the other hand, 

 refers to testicular interstitial tissue in 

 Bana and says that its cyclic evolution is 

 correlated directly with the seasonal de- 

 velopment of secondary sex characters, par- 

 ticularly the growth of glands in the callos- 

 ity of the thumb. This has been confirmed 

 in Discoglossus, another anuran, in which 

 interstitial tissue is said to be abundant 

 (Bcnoit, Kehl, and Leportois, 1941; Kehl, 

 1 944a ) . Because the administration of tes- 

 tosterone also induces development of the 

 callosity of Discoglossus, it is concluded 

 that the interstitial cells produce andro- 

 gen. The male secondary sex characters of 



-Couirier, 1921a, c, 1922a, b; Craig-Bennett, 

 1931; Stephan and Clavert, 1938; Potter and Hoar, 

 1954 ; Marshall and Lofts. 1956. 



Triturus, a newt, are highly developed dur- 

 ing the fall, winter, and spring; at the same 

 time a variety of mature cells— sperm, in- 

 terstitial cells, and Sertoli cells — is also 

 abundant (Adams, 1940). 



Noble (1931) has much support for his 

 conclusion that in the amphibian testis 

 male hormone is derived from sperm or 

 Sertoli cells rather than from interstitial 

 cells. In the urodele some of the testicular 

 stromal cells develop into interstitial cells, 

 but only after the breeding season, when, of 

 course, the secondary sex characters have 

 regressed. Thus, although the interstitial 

 cells increase in number, size, and lipid con- 

 tent, thereby coming to resemble mamma- 

 lian interstitial cells, there is no direct 

 evidence for their endocrine function, and 

 the reason for their development is unex- 

 plained. In addition, these cells are en- 

 tirely undeveloped at the time when the sex 

 characters indicate by their prominence 

 that male hormone is being released.-^ Fur- 

 ther research on the source of testicular 

 androgen is required. 



Reptiles 



The rei)tilian testis produces male hor- 

 mone, as shown by the results of castration. 

 Valle and Valle (1943) extracted the testes 

 of the rattlesnake, Crotalus t. terrificus, 

 and of the related viper, Bothrops jararaca; 

 10 mg. testicular tissue contained enough 

 androgen for positive results in two non- 

 quantitative biologic tests. 



The role, if any, of interstitial cells in the 

 production of androgen in reptiles has not 

 been established. Interstitial cells have been 

 seen in turtles of the genera Emys, Terra- 

 pene (Cistudo), and Testudo; the cells in- 

 crease in size and lipid content before and 

 during the breeding season.'* Since inter- 

 stitial cell volume decreases in June when 

 the epididymis is undergoing seasonal de- 

 velopment, the interstitial cells are prob- 

 ably not responsible for epididymal changes 

 (Dornesco, 1926a). In Terrapene the in- 

 crease in cell size may be related to the se- 



=* Humphrey, 1921, 1925; Champy, 1922a, b, 

 1923c, 1924, i932; Harms, 1926a; Oslund, 1928. 



'Ganfini, 1902; Pellegrini, 1925; Dornesco, 

 1926a; Stieve, 1933; Altland, 1951; Combescot, 

 1954a. 



