Ultrastructural study of the mental body of Hydromantes genei (Amphibia: Plethodontidae)

Abstract

The mental glands of Hydromantes genei are considered a specialized form of the urodele serous cutaneous glands. Use of a variety of techniques of maceration and digestion as well as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) has shown the three-dimensional morphology of secretory and myoepithelial cells. Secretory cells are pyramidal and rest on an almost continuous layer of myoepithelial cells. The latter have a long ribbon-like body from which branch off transversal and longitudinal processes with swallow-tailed ends. Cytoplasmic processes of secretory cells, containing irregular dense vesicles, squeeze through clefts between myoepithelial cells and may reach, at some points, the basal lamina. The interstices between myoepithelium and secretory cells are extraordinarily rich in nerve endings with clear vesicles. The glandular outlets appear as elliptical stomata in the superficial layer of the epidermis and are lined by horny cells, which invaginate to circumscribe the excretory duct. The morphological results indicate that the myoepithelium of Plethodontidae mental glands differ in some respects from that of amphibian serous cutaneous glands. A double polarity for the secretory cells is also suggested. © 1993 Wiley-Liss, Inc.

Ultrastructure of the mental gland of the Red‐Backed Salamander, Plethodon cinereus (Amphibia: Plethodontidae)

“…Neither Borgioli (, ) nor Riva et al . () studied seasonal variation in the mental glands of H. italicus , although Riva et al . () mention obtaining specimens from different times of the year.…”

“…The first hypothesis tested was that the mental gland of P. cinereus will be similar in cytology to that of the other two plethodontids that have been studied, Sever (1975) on Eurycea quadridigitata, and Borgioli (1977Borgioli ( , 1978 and Riva et al (1993) on Hydromantes italicus. The active mental glands of both of these species are characterized by the presence of numerous electron-dense secretory vacuoles as seen in P. cinereus, and the organelles for production of glycoproteins are present.…”

“…Neither Borgioli (1977Borgioli ( , 1978 nor Riva et al (1993) studied seasonal variation in the mental glands of H. italicus, although Riva et al (1993) mention obtaining specimens from different times of the year. Borgioli (1977) described some 'peculiar structures appearing as light parallel membrane stacks of unusual length, enlarging into vesicles at both ends'.…”

“…Borgioli (1978) was a short note describing the intercalary ducts through the epidermis. Riva et al (1993) provided descriptions utilizing both scanning and transmission electron microscopy. Their study has excellent electron micrographs of the intercalary ducts and pores.…”

“…Few studies, however, exist on the ultrastructure of these glands. Sever (1975) reported on seasonal changes in the cytology of the mental glands of the North American plethodontid Eurycea quadridigitata, and Borgioli (1977Borgioli ( , 1978 and Riva et al (1993) described ultrastructure of the mental gland of the European salamander Hydromantes italicus. The active mental glands of both species were characterized by the presence of numerous electron-dense secretory vacuoles.…”