Structure and Function of the Male Mullerian Gland in Caecilians, with Comments on Its Evolutionary Significance

The Mullerian glands of adult male caecilians, which are derived from the undifferentiated Mullerian ducts, secrete many constituents similar to those found in the semen of birds and mammals. These include fructose, acid phosphatase, and mucopolysaccharides. The pH of the secretion is similar to that of semen. Caecilians reproduce terrestrially using intromission and internal fertilization. It is likely that the secretion of the Mullerian glands provides fluid and metabolites for use in sperm transport since an aquatic medium for reproduction is obviated. Since part of the mammalian prostate is lined with epithelium of Mullerian duct origin, and the prostate secretes certain of the constituents of semen, it is possible that the caecilian condition is a primitive state in the evolution of accessory reproductive glands which facilitate terrestrial reproduction.