Necturus Testis and Reproduction 73 



mechanisms controlling spermatogenesis is still rudimentary. It would 

 appear that in order to approach and elucidate some of these problems 

 more attention should be made in choosing the correct and appropriate 

 animal model. Nature, fortunately, has been very generous to investiga- 

 tors of male reproduction by offering a wide range of animals displaying 

 different reproductive strategies. No one species per se is capable of 

 providing all the answers. By judicious selection, however, one can elect 

 to investigate a particular animal because, due to some unique or novel 

 morphological or biochemical parameter, it is more suited for studying 

 one particular aspect of male reproduction. Thus, in Necturus testis the 

 development of the glandular tissue plus the formation of high levels of 

 estrogen make this species an excellent animal model for studying the 

 relationship between spermatogenesis and Leydig cells and the role of 

 estrogen in the testis. Both these problems are difficult to approach in 

 the more acceptable laboratory animals, which illustrates and defines 

 the importance of studying the so-called unconventional animal models 

 in order to understand more fully the phenomena associated with male 

 reproduction. 



ACKNOWLEDGMENTS.— We would like to acknowledge and 

 thank Ray E. Ashton, Jr., North Carolina State Museum of Natural 

 History, for supplying specimens of Necturus lewisi. Supported by 

 USPHS HD16715. 



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