MICROMORPHOLOGY OF THE MEHLIS' GLAND, AN ORGAN OF THE FEMALE TREMATODE REPRODUCTIVE SYSTEM

The article describes histological features of the structural organization of the Mehlis’ gland, an organ of the female reproductive system in some trematode species. Studies of the morphological structure of the Mehlis’ gland in some trematodes demonstrate that the organ has a spherical shape with sharply defined or undefined boundaries. It is located near the ovary and consists of two types of glandular cells immersed in the basic substance. Numerous large cells with an irregular drop-shaped form located along the periphery of the gland perceive basic dyes and contain granules. These cells have all the characteristics of secretory cells. Small central cells perceive an acid dye. They do not exhibit secretory activity. The inner part of the gland is eosinophilic. The Mehlis’ gland architectonics was found to be represented by two types: 1) a compact organ with a clear boundary, relatively isolated from the surrounding parenchyma; 2) an organ consisting of loose cells scattered as bundles, radially diverging in different directions, and not isolated from the parenchyma. The first type of organ structure in our studies had paramphistomes. The second type of the Mehlis’ gland structure pertained to Fasciola, Dicrocelia and Opisthorchidae. Morphological features of the gland structure and location evidence that the Mehlis’ gland cells are in close functional contact with mature yolk cells and participate in the formation of the shell membrane of trematode eggs.