Anatomy of reproductive tract in Octodon degus Molina: a nonscrotal rodent.

O. degus reproductive tract is characterized externally by a perianal circle with the penis pointing posteriorly. Beneath the perianal circle is the cremasteric sac. Testes are always inside the abdomen, with the epididymis attached to them but the cauda epididymis lays inside the cremasteric sac. Vas deferens and seminal vesicles open independently into the urethra. Three pairs of lateral prostatic lobes open by many ducts into the urethra. The corpora spongiosa holds the urethra in the ventral groove of the corpus cavernosum. The corpus cavernosa are inserted into the bulbo cavernosum muscle and at its distal end are attached to the base of the baculum, that lay under the dorsal face of the glans. The glans has two openings: the urinary meatus and the intromittent sac. The characteristics of the testicular artery agree with the anatomy expected for animals with intrabdominal testes; it is relatively short, with few loops and a wide diameter. Many of these anatomical features are shared by other caviomorphal rodents. If testicular temperature is similar to body temperature in these animals as in O. degus (36.0 degrees and 37.2 degrees C respectively), they would exhibit little testicular thermal sensibility. Among these rodents O. degus has the lowest body temperature. Moreover this work reinforces the hypothesis that descent of the testis into the scrotum has occurred secondarily to the immigration of the cauda epididymis.