Secretory and basal cells of the epithelium of the tubular glands in the male Mullerian gland of the caecilian Uraeotyphlus narayani (Amphibia: Gymnophiona)

Abstract

Caecilians are exceptional among the vertebrates in that males retain the Mullerian duct as a functional glandular structure. The Mullerian gland on each side is formed from a large number of tubular glands connecting to a central duct, which either connects to the urogenital duct or opens directly into the cloaca. The Mullerian gland is believed to secrete a substance to be added to the sperm during ejaculation. Thus, the Mullerian gland could function as a male accessory reproductive gland. Recently, we described the male Mullerian gland of Uraeotyphlus narayani using light and transmission electron microscopy (TEM) and histochemistry. The present TEM study reports that the secretory cells of both the tubular and basal portions of the tubular glands of the male Mullerian gland of this caecilian produce secretion granules in the same manner as do other glandular epithelial cells. The secretion granules are released in the form of structured granules into the lumen of the tubular glands, and such granules are traceable to the lumen of the central duct of the Mullerian gland. This is comparable to the situation prevailing in the epididymal epithelium of several reptiles. In the secretory cells of the basal portion of the tubular glands, mitochondria are intimately associated with fabrication of the secretion granules. The structural and functional organization of the epithelium of the basal portion of the tubular glands is complicated by the presence of basal cells. This study suggests the origin of the basal cells from peritubular tissue leukocytes. The study also indicates a role for the basal cells in acquiring secretion granules from the neighboring secretory cells and processing them into lipofuscin material in the context of regression of the Mullerian gland during the period of reproductive quiescence. In these respects the basal cells match those in the epithelial lining of the epididymis of amniotes.

Light and electron microscopic observations of fabrication, release, and fate of biphasic secretion granules produced by epididymal epithelial principal cells of the fan-throated lizardSitana ponticeriana cuvier

“…A comparable situation was reported in the secretory cells of the Mullerian gland of the caecilian Uraeotyphlus narayani. The mitochondria accumulate as dense aggregations around the secretory vesicles and an intimate association between the mitochondria and condensing vacuoles was noticed (George et al, 2004). Further studies are required to explain these observations.…”

Development of pancreatic acini in embryos of the grass snake Natrix natrix (Lepidosauria, Serpentes)

“…They are structures containing secretory enzymes in high dilution similar as in pancreatic acinar cells of other amniotes (Jamieson & Palade, 1967;Lew, Hammel, & Galli, 1994;Novikoff, Mori, Quintana, & Yam, 1977) as well as in the acinar cells of salivary glands (Amsterdam, Ohad, & Schramm, 1969). Their structure is also similar to that of the mental gland in salamanders (Sever, 2017) and the Müllerian gland in amphibians (George et al, 2004). Condensing vacuoles in the pancreas of N. natrix were formed by fusion of tiny vesicles containing flocculent material.…”