Early differentiation of the testis in the native cat, Dasyurus viverrinus (Marsupialia)

The development of the testis in the native cat Dasyurus viverrinus (Marsupialia) is described, from Day 3 to 2.5 months post partum. The gonad rudiment consists of a mass of undifferentiated blastema cells of mesenchymal origin. The primordial germ cells populate the rudiment around the neonatal period. On Day 3 two cell types autodifferentiate from the gonadal blastema (pre-Sertoli and stroma cells) and the tunica albuginea begins to form. Pre-Sertoli cells are large, pale, cells which encompass the primordial germ cells and come to form a zone just beneath the tunica albuginea. By the end of the second week the cell complex has become transformed into a series of sex cords which encircle the gonad rudiment peripherally and converge on the rete cord in the hilar region. The stroma cells are fibroblast-like cells and occupy the central portion of the rudiment; by the eighth week, Leydig cells are appearing among them. No evidence was found for mesothelial invaginations or mesonephric contributions to the gonad. The classically recognised regions of 'cortex' and 'medulla' cannot be recognised and the seminiferous tubules differ in arrangement from that in eutherians.