The structure of the penis with the associated baculum in the male greater cane rat ( Thryonomys swinderianus )

Abstract

In this study, the structures of penises of eight sexually mature male greater cane rats were examined at both macroscopic and histological levels. Each animal was sacrificed after anaesthesia with ether and then dissected open with the penis exposed from its root. The penises were first grossly examined, measured, and then prepared for histological examination. From this study it was observed that the body size has no allometry with penile size, but the testicular weight correlated with Os penis length in the greater cane rat. Grossly, the penis which was whitish in colour, with a mean length of 5.46 ± 0.36 cm, has no obvious collum penis but a flexura that turns it caudo-ventral and separates the corpus and glans penis. There was the presence of cornified papillae covering parts of the corpus and glans penis as well as a blind sac sacculus urethralis under the urethra on the glans penis. Histologically, the corpora cavernosa penis were completely separated by a connective tissue septum which sent the trabeculae network into the cavernous tissues and replaced the caverns as it moves from corpus to glans penis. The Os penis formed through endochondral ossification after 42 months of age in this animal. Therefore, from a histological standpoint, the cane rat penis belongs to the intermediate type. In conclusion, these findings provide vital information on the penile anatomy of the greater cane rat, which will serve as a basis for comparing penile morphology among the suborder hystricomorpha and expand knowledge of the reproductive biology in this animal. (Folia Morphol 2011; 70, 3: 197–203)