Morphology of the Mental Hedonic Gland Clusters of Plethodontid Salamanders (Amphibia, Urodela, Plethodontidae)

Mental hedonic gland clusters of 18 species of eastern United States plethodontids were studied by gross dissection and light microscopy. In the Plethodontinae examined, the glands are largely or completely posterior to the mandibular symphysis. In the Plethodontini, the glands are relatively short, vertically oriented in a circular cluster, and bordered dorsally by the dense inner layer of the dermis, the stratum compactum. Within the Hemidactylini genus Eurycea, the glands are more elongate and excretory ducts only occur ventral to and immediately posterior of the mandibular symphysis. The glands then pass horizontally between the intermandibularis posterior muscle ventrally and the geniohyoideus muscle dorsally. The stratum compactum is reduced to a thin sheath over the glands. Reduced or specialized glands resembling those of the Plethodontini occur in the hemidactyliines Hemidactylium, Typhlotriton, and E. multiplicata. From literature reports, the Bolitoglossini contain seven genera with glands like the Plethodontini and one (Oedipina) with glands like Eurycea. In the Desmognathinae, except for Desmognathus wrighti, the excretory ducts are in a fleshy protrusion anterior to the mandibular symphysis, and the short glands extend posteriorly, terminating ventral to and just posterior of the mandibular symphysis. In D. wrighti the gland cluster bifurcates anteriorly with elongate glands then extending posteriorly between the dermis and throat musculature along the medial borders of the dentaries. The excretory ducts in D. wrighti pass dorsally around the anterior ends of the dentaries.