Differentiation and development of testis in the oviparous lizard,Calotes versicolor (Daud.)

Abstract

The differentiation and development of the testis in the lizard Calotes versicolor was studied histologically and histoenzymatically from the day of oviposition (stage 27) to 2 months after hatching. The study reveals the appearance of the gonadal component as a genital ridge at stage 27. The first sign of testis differentiation is observed at stage 33, which displays a well-developed medulla consisting of seminiferous cords comprising Pre-Sertoli cells. The sex differentiation of the embryonic gonads occurs at stage 34. At this stage, seminiferous cords of the testis are prominent and extensive with many pre-Sertoli cells and few spermatogonia. The interstitial space consists of immature fibroblast-type Leydig cells. Pre-Sertoli cells of the seminiferous cords differentiate into Sertoli cells with a triangular nucleus becoming apparent around stages 36-37. The fibroblast-like Leydig cells differentiate into round matured Leydig cells at stage 40. Quantitative estimation of germ cells reveals that the number of germ cells increases in individual gonads, and in 5-day-old hatchling's, this number multiplies by manifold. Spermatogonia show reductional division in the testis of 1-day-old hatchlings. Histochemical localization of Delta5-3beta-HSDH and G-6-PDH activity appears in the seminiferous cords (medulla) of the testis after sexual differentiation (stage 36), indicating that the embryonic medulla is the site of steroidogenesis and not the cortex in C. versicolor. This study also suggests that morphological differentiation of the gonad precedes detectable steroidogenesis in this species. In 10-day-old hatchling's, Delta5-3beta-HSDH activity is seen in the interstitial cells of the testis, which, however, is not detected in the seminiferous tubules. The intensity of the enzyme activity remains more or less the same in the testis up to 10 days after hatching and begins to increase thereafter. The increase in steroidogenesis parallels the progressive post-hatching increase of the interstitial/Leydig cells.

Sex of incubation neighbours influences hatchling sexual phenotypes in an oviparous lizard

“…In the studied population females oviposit eggs containing embryos at Dufaure and Hubert's (1961) stages 31-33 (Braña et al 1991, and additional unpublished data), at which time endogenous production of steroid hormones is unlikely. Detailed studies in the lizard Calotes versicolor indicated that gonadal diVerentiation begins at stage 34 and there was no appreciable steroidogenesis until stage 36 in both male and female embryos (Doddamani 2005(Doddamani , 2006. Similar results were reported in the lizard Sceloporus undulatus (Austin 1988) and in green anoles (Anolis carolinensis; Lovern and Wade 2003b).…”

Differential expression of estrogen receptor alpha in the embryonic adrenal–kidney–gonadal complex of the oviparous lizard, Calotes versicolor (Daud.)

“…Hence, steroidogenic potency of adrenocortical cells prior to gonad may be considered. This further supports earlier work from our laboratory (Doddamani, 1994(Doddamani, , 2000(Doddamani, , 2006.…”

“…The endogenous production of estrogen may act in a paracrine fashion to induce neighboring cells into ovarian differentiation pathway to direct ovarian differentiation at FPT. The enzyme immunohistochemistry of the developing gonad in C. versicolor has already revealed that morphological differentiation of gonad precedes the onset of steroidogenesis (Doddamani, 1994(Doddamani, , 2000(Doddamani, , 2006. The immunohistochemistry is more reliable and sensitive than enzyme histochemistry and the results of the current study suggest that the synthesis of estrogen in the developing gonad coincides with sexual differentiation of the gonad.…”

Molecular Mechanisms of Sex Determination in Reptiles

“…Another group of cells differentiates into peritubular myoid cells, which envelop the testis cords to form seminiferous tubules [Morrish and Sinclair, 2002]. A third cell type, the interstitial cells of Leydig, differentiates between the testis cords and seminiferous tubules [Doddamani, 2006]. The final distinguishing feature of testis morphogenesis is formation of the male-specific vasculature [Morrish and Sinclair, 2002].…”