Testicular Descent in the Marsupial Trichosurus vulpecula (Kerr)

Abstract

In T. vulpecula testicular descent is not completed until the 10th week of pouch life. The testes are abdominal in position during the first 2 weeks and inguinal from the 3rd to the 8th week inclusive. The final or scrotal stage of descent requires a further 2 weeks. The left testis descends slightly before the right. In advance of the testis. the saccus vaginalis penetrates the transversis muscle and subsequently the aponeurosis of the external oblique muscle to become subcutaneous in location. During passage of the testis into the canal provided by the saccus. the testis undergoes a ventrolateral rotation about its longitudinal axis through an angle of about 90°. Upon entry into the scrotum. the testis rotates in a reverse direction through at least 180°. This results in the testis becoming enfolded, around its lateral aspect, by the elongated mesorchium.