The duration of the cycle of the seminiferous epithelium of the South American white-belly opossum, as obtained by autoradiography after intratesticular injection of tritiated thymidine, was estimated to be 17.3 +/- 0.1 days (mean +/- s.d.). Quantitative histological analysis was performed on testes from animals caught both in mating and non-mating periods of the annual reproductive cycle. Significant differences were found in the volumetric proportion of Leydig cells, but the spermatogenic yield remained constant throughout the year. The numerical ratio between type A spermatogonia and zygotene primary spermatocytes (1:12.0), as well as daily sperm production (4.8 x 10(6) sperm cells per g of testis parenchyma per day), were found to be lower than those reported in most eutherian mammals.

The recent capture of a prepubertal male specimen of the rare opossum Glironia venusta provided the description of its genital system and a comparison with other Brazilian didelphids. Glironia is remarkable for the morphology of its short-clefted glans penis in which the urethral grooves terminate near the tips. This taxon shows two pairs of bulbo-urethral glands which arc similar in number to those observed in species of the genus Caluromys and Gracilinanus, but different from other Didelphidae which have three-pairs. The lack of segmentation of the prostate in Glironia may be due to the immaturity of the single specimen examined.Resume. -La recente capture d'un specimen male pre-pubere du rare opossum Glironia venusta nous permet de decrire son appareil genital, et d'en comparer la morphologic avec celle d'autres Didelphidae vivant au Bresil. Glironia est remarquable par les aspects morphologiques du court gland bifurque de son penis s'ouvrant par une courte fente distale. Ce taxon possede deux paires de glandes bulbo-urethrales, tout comme les especes etudiees ä ce jour des genres Caluromys et Gracilinanus, alors que les autres Didelphidae dccrits en ont trois paires. L'absencc de segmentation de la prostate de Glironia peut etre due a Timmaturite de l'unique excmplaire examine.

The objectives of this study were to evaluate the effects of pinealectomy, adrenalectomy and pinealectomy-adrenalectomy upon the quantification of spermatogenic cells of rats. As such, 32 adult Wistar rats with a mean body weight of 331.7± 15.5g were assigned into one of the following treatments: (a) a sham-operated control group, consisting of nine animals; (b) ten pinealectomized animals; (c) seven adrenalectomized animals and (d) six pinealectomized plus adrenalectomized animals. No significant differences were observed between groups for the following parameters: body, testes, prostate and seminal vesicle weights, seminiferous tubular diameter, number of cells per seminiferous tubular cross sections (primary spermatocytes at pachytene, round spermatids, Sertoli cells) and numbers of germ cells per Sertoli cell (primary spermatocytes at pachytene and round spermatids ). Although no increase in testicular weight was observed following pinealectomy, a significant (P<0.05) increase of approximately 11.5% in the number of round spermatids per Sertoli cell (Sertoli cell ratio) occurred thus suggesting that short-term pinealectomy abolishes the antigonadal effect of the pineal gland upon adult Wistar rat testes.

The testicular arteries of Didelphis azarae originate from the abdominal aorta either independently from each other or by way of a common trunk. Accessory testicular arteries may be found. At the spermatic cord they form a rete mirabile having 26.8 ± 5.0 and 29.3 ± 4.9 slender branches on the right and left sides, respectively. The arterial branches are intermingled with veins of similar caliber and number. Near the testis the branches of the rete reunite in a single vessel which then penetrates the parenchyma of the testis. Inside the testis the artery divides usually into two main branches that course toward the caudal pole. The rectal, scrotal and testicular temperatures were 32, 28.5 and 30.4 °C, respectively, appearing that an abdominotesticular gradient temperature exists in this animal. Whether this mechanism is thermoregulatory for the normal spermatogenesis cannot be inferred from the present work.