Three types of cutaneous glands in the skin of the salamandrid Pleurodeles waltl. A histological and ultrastructural study

Abstract

Histological and ultrastructural investigations revealed three different multicellular skin gland types in the salamandrid Pleurodeles waltl. The mucous glands are small, with one layer of secretory cells surrounding a central lumen; they produce the viscous and slippery mucus film that has various functions in amphibians. The serous glands can be divided based on their histological and ultrastructural characters into the granular gland Type I (GGI) and the granular gland Type II (GGII). The first type (GGI) is moderately sized and distributed throughout the body surface, with higher concentrations in the parotoid and back regions. In contrast, the second type (GGII) is very large (for Pleurodeles) and was found only in the tail, with highest concentration in the tail dorsum. Both granular gland types contain mainly proteinaceous materials but differ in their morphological features including size, shape, cellular organization and vesicle distribution, vesicle size and vesicle shape. Both GGI and GGII are especially concentrated in body parts that are presented to an attacking predator and are hypothesized to produce repellent to poisonous substances to thwart potential aggressors.