Testis of Non-Mammalian Vertebrates
The testis of non-mammalian vertebrates is also made up of tubules. The tubules contairi nest of cells which undergo spermatogenesis asynchronously. Each nest of cells is called, a cyst, which contains germ cells of the same stage of differentiation. For example in a tubule there may be cysts of spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa. In the breeding season testis lobules contain maximum number of cysts of spermatozoa and also the spermatozoa released into the lumen of the tubule. During the non-breeding season there are more number of cysts of spermatogonia and spermatocytes. You have studied earlier in this section that in mammalian testis the interspaces between the seminiferous tubules is occupied by Leydig cells. In the testis of non-mammalian vertebrates the interspaces between the tubules is occupied by the lobule boundary cells; These are homologous to the Leydig cells and apparently have the same endocrine function.
Figure : Testis of Non-Mammalian Vertebrates