Interstitial cell cycle of Ameiva ameiva (Sauria, Teiidae)in the Cerrado region of Central Brazil.

The patterns of annual variations in spermatogenic and interstitial cell activities were investigated in Ameiva ameiva from Central Brazil. Testis mass, germinative epithelium height, and seminiferous tubule diameter were used as indicators of spermatogenic activity, while the cell density and the height of the interstitial cell subtunic were used as indicators of the activity of interstitial cells. Monthly means of these parameters were compared by means of an ANOVA, using size-adjusted values. Significant differences among monthly means were observed in the spermatogenic activity of A. ameiva, which is reduced during the dry months. Conversely, no significant monthly differences were observed in the activity of interstitial cells. There was a negative correlation between spermatogenic activity and interstitial cell activity parameters. It is suggested that spermatogenesis is induced by gonadotropins but not by testosterone, and that there may exist a negative feedback mechanism between testosterone and pituitary hormones. The continuous activity of interstitial cells in A. ameiva may be adaptive, being maintained by ongoing intrasexual selection or may be a phylogenetically conservative trait. J Morphol 233:99-104, 1997. © 1997 Wiley-Liss, Inc.