Ultrastructural characteristics of the reproductive organs of adult male helminth Heterakis dispar (Nematoda: Heterakidae)

Abstract

Nematodes belonging to the Heterakidae family are similar in appearance and their identification causes certain difficulties. For this reason, there is a need to define new taxonomic characteristics. On the other hand, despite the fact that the nematode Heterakis dispar Schrank, 1790, included in the same family, has a wide distribution area, there is little information about the ultrastructure of the parasite. Research on the ultrastructure of the reproductive system of this helminth hase not been conducted. Parasitic worms collected from the caeca of birds were identified, following which, based on the accepted methods of electron microscopy, blocks were prepared, cut, stained, pictures and electrograms were prepared and described. In the present study, the ultrastructural characteristics of the reproductive organs (testis, seminal vesicle, vas deferens and ejaculatory duct) of the adult nematode H. dispar, a specific parasite of domestic waterfowl, were studied with the help of light and electron microscopic methods. The obtained results were compared with the structure of other studied species (H. gallinarum Gmelin, 1790 and H. spumosa Schneider, 1866) of the Heterakidae family. Firstly, it was revealed that the reproductive organs of the male nematode H. dispar are located in the pseudocoelomic cavity, which is considered a taxonomic sign of this family. As in other species of the family, the testis, seminal vesicle, and wall of the vas deferens of the male nematode H. dispar consist of a basement membrane and an epithelial layer. In addition to the basement membrane, muscular and epithelial layers, the wall of the ejaculatory duct is also composed of glandular cells in the front part of the duct. It was revealed that, in the lumen of the tubular reproductive organs of the adult male nematode H. dispar, germ-cells turn into spermatogonia in the germinal zone and spermatocytes in the growth zone of the testis, spermatids in the seminal vesicle, incomplete formed spermatozoa in the vas deferens, and fully formed spermatozoa in the ejaculatory duct of the parasite. The spicules of the parasite nematode, which are the secondary sexual organs consist of a thick cuticle on the outside, and hypodermal origin cells and processes of nerve cells (dendrites and axons) on the inside. Two processes are found on the spicules, which is not observed in other nematodes of the same family.