Study Of Fetal Sex Determination Based On External Genitalia And Gonadal Differentiation In Water Buffalos

摘要

This study was performed on 102 embryos and fetuses that were collected from Ahvaz slaughter house. The specimens was divided in three group, on the basis of external genitalia differentiation and crown Rump Length (CRL), as groups 1,2 and 3. The embryos of group 1 (No. 63, CRL-10-83cm) showed completely developed external genitalia of male and female, so there was no doubts in the recognition of their sexes. The embryos of group 2 (No. 19, CRL-4-10cm) also showed clear sex on the basis of genital tubercle (clitoris in the female and penis in the male embryos) and genital swellings (lips of vulva in the females and scrotum in the males). The tip of genial tubercle of females embryos have showed dorso-caudally and of males ventro-cranially directions, respectively. In the embryos of group 3 (No. 20, CRL=0.38-4 cm). The determination of sex was not possible by help of external genitalia. So, the gonads of these embryos, were removed from abdominal cavity and after histological preparations, stained by H & E and PAS methods. On the basis of histological studies, the sex differentiation of gonads to testis and ovary were recognized in embryos with CRL=2.1 cm, and CRLl<2.3 cm respectively. The gonads of embryos with CRL<2.1 cm were recognized as undifferentiated. These findings indicated that the sex differentiation starts earlier in the gonads compare to external genitalia but the differentiation of gonad and external genitalia of male has priority to female embryos.The sex of embryos were not recognized in undifferentiated gonad neither by external genitalia nor histological structure. Introduction Mammalian sex determination proceeds in three distinct phases. In the first stage, genetic sex is determined at the time of fertilization by the chromosomal complement of the fertilizing spermatozoon. Later, during embryonic development , this genetic information is translated in to gonadal sex that determines the growth of either a testis or ovary from a bipotential early indifferent gonad.The third stage which is the phenotypic sex determination, begins in fetal or early post-natal life and continues through puberty, a period in which endocrine products of the gonads direct the differentiation of the accessory sex ducts and external genitalia (Loffler and Koopman, 2003). External and gonadal sex differentiation has been studied in human and domestic animals with different results.In male human fetus, at 7th week of fetal life, under the influence of Y chromosome, primary sex cords containing proliferated coelomic epithelium and primordial germ cells continue their proliferation and form medullary (testicular) cords. Synchronously a thick fibrous layer called tunica albuginea forms due to proliferation of mesenchyme. The female gonads differentiate later than male. Because of the absence of Y chromosome, the primary sex cords degenerate and coelomic epithelium proliferates and form cortical or secondary sex cords that are characteristic of early female gonad (Sadler, 2004).Sex differentiation has been studied in human (Baker and Scrimgeour, 1980), swine (Inomata et al., 1993), dog (Evans, 1979), bovine (Erickson, 1966), horse (Sakai, 1955) and goat (Harshan et al., 1994 and banankhojasteh et al., 2006). However, only few studies on ovarian differentiation in water buffalo fetuses was reported (Ghannam and Deeb,1969).In many parts of the world, water buffaloes (bubalus bubalis) are raised for production of milk, meat, hide and down. Water buffaloes have high adaptability and can live in different climates. During recent decades, universal concentration on water buffaloes has in creased especially in Asian countries and new initiatives have been starting for development of related industries. Therefore, conduction of basic and applied research regarding various aspects of water buffaloes seems necessary.Because there is no comprehensive study on external and gonadal sex differentiation in fetus and in view of the fact that studies on va