Morphology of the reproductive system in Marmosa robinsoni (Mammalia: Didelphidae)

Abstract

Marmosa robinsoni (Didelphidae) is a small-sized marsupial characterized by a prehensile tail, nocturnal, solitary, and predominantly arboreal/semiscansorial habits, and the absence of a marsupium. Descriptions of the reproductive system remain scarce for most neotropical marsupials, despite this system representing a major distinguishing feature between metatherians and eutherians. This study describes the external morphology and histology of the male and female reproductive systems of M. robinsoni, as well as secondary sexual characters indicative of reproductive activity. Eight individuals (five females and three males) were collected, processed, and examined. The reproductive tracts were described, and morphological patterns previously reported for other marsupials were observed with respect to anatomical arrangement, histological composition, and characterization of the organs and ducts comprising this system. However, some species-specific features were identified when compared with the few other species for which these characters have been studied, including the number of bulbourethral glands, the non-bifid configuration of the glans penis, pigmentation of the tunica vaginalis in the testes, and the presence of a submammary pigmented patch. Examination of the correspondence between gametogenic status and secondary sexual characters indicated that mammary arrangement and the presence of prominent testes are reliable indicators of reproductive activity.