Persisting Wolffian and Müllerian ducts in female and male southern tamanduas (Tamandua tetradactyla)?

Abstract

The southern tamandua (Tamandua tetradactyla) and the giant anteater (Myrmecophaga tridactyla) belong to the anteater family Myrmecophagidae and both species share basic morphological characteristics including the general features of reproductive organs. However, in female and male giant anteaters, persisting Wolffian and Müllerian ducts have been observed that have not been described in the southern tamandua, so far. Therefore, the present study evaluated whether those persisting genital ducts of the opposite sex can be observed in the southern tamandua as well. For this purpose, the reproductive organs of adult roadkill male and female specimens were studied in Brazil. In female southern tamanduas, persisting Wolffian ducts extended from the opening of the uterovaginal canal into the sinus urogenitalis in cranial direction through the ventral wall of the uterovaginal canal and the uterus and followed the course of the uterine tubes until the lateral pole of the ovaries. Those ducts showed the same characteristics as described in giant anteaters and revealed similarities to male epididymal and deferent ducts. Furthermore, glandular structures in the wall of the urethra and the sinus urogenitalis were observed that showed microscopic characteristics corresponding to male prostate and bulbourethral glands, similarly to observations in female giant anteaters. In male southern tamanduas, on the contrary, only rudimentary tubules were found in the prostatic urethral wall while well-differentiated Müllerian ducts have been previously described in the male giant anteater. In conclusion, well-developed Wolffian ducts are a shared characteristic in both female southern tamanduas and female giant anteaters whereas well-developed Müllerian ducts are unique to male giant anteaters and only rudimentary Müllerian vestiges were observed in the male southern tamandua. Data on those persisting genital ducts are of interest for studies on reproductive biology and physiology of southern tamanduas and sexual development of mammalian species in general.