Comparison of the Homology Between Muskrat Scented Gland and Mouse Preputial Gland

Muskrats ( Ondatra zibethica ) develop special glands in the lower abdomen that secrete muskrat musk. The lower abdomen of mice, which are also rodents, has a pair of preputial glands. The muskrat scented glands are suggested to be a specialized form of the preputial glands and homologous to the preputial glands of mice, but little evidence is available to support this notion. Here, we performed histomorphology and metabolomic and transcriptomic analyses of the muskrat scented gland and mouse preputial gland by tissue sectioning, gas chromatography-mass spectrometry (GC–MS), and transcriptome sequencing to determine the similarities between the two organs. The cells of the scented glands and the preputial glands were morphologically similar, with both exhibiting the characteristics of endocrine cells. GC–MS analyses revealed that the secretions from both organs contained large amounts of fatty alcohols, wax esters, and cholesterol, with their secretions having similar components, and may serve as the functional substances of chemical signals. Transcriptome analysis also revealed several genes related to fatty alcohol synthesis, such as FAR1 , and genes related to cholesterol metabolism pathways, such as steroid hormone biosynthesis and primary bile acid biosynthesis, that were expressed in both the scented gland and the preputial gland, thereby confirming the findings of tissue sectioning and GC–MS. Our data indicate that the muskrat scented gland and the mouse preputial gland are similar at multiple levels, providing some evidence for the homology of the two organs.