Morphology and Seasonal Variation of the Nasolabial Glands of Eurycea quadridigitata (Holbrook)

Abstract

The morphology and seasonal variation of the nasolabial glands of the plethodontid Eurycea quadridigitata were studied by gross dissection, light microscopy, and transmission electron microscopy. Nasolabial glands of E. quadridigitata are simple, branched, tubular exocrine glands found from the snout posterior to the level of the eye with orifices along the nasolabial groove. The glands are directly beneath the dermis and largely outside of the bony skull elements. Those glands along the lip are the most numerous and highly developed, and they turn ventrally as the nasolabial groove reaches its termination on the upper lip. Seasonal growth from September through January of the nasolabial glands along the lip results in development of a ventral elongation, the cirrus. The fine structure features of the nasolabial glands include wide intercellular canaliculi, abundant mitochondria, dense bodies in the lumen and cytoplasm, and absence of ergastoplasm. Nasolabial glands of both sexes show only slight cytological changes throughout the year. Nasolabial glands of females are similar morphologically to those of males but do not hypertrophy seasonally. * * *