Oocytes Development in Ixodid Tick of the Genus Dermacentor

Abstract

Introduction. Ixodid ticks are the carriers of many infectious and parasitic diseases. Transmissible tick-borne diseases include borreliosis, viral encephalitis, anaplasmosis, ehrlichiosis and babesiosis, they can be dangerous for both humans and animals. Since the forest areas stopped being treated with pesticides, the reproduction of ixodid ticks became almost unregulated, and their population is constantly growing. In addition, ixodid ticks, the carriers of a number of dangerous anthropozoonosis, have high fecundity.Therefore, the aim of the study was to investigate the process of ectoparasites development, specifically, the dynamics of the oocytes maturation process in ixodid ticks of the genus Dermacentor. Materials and methods. The ixodid ticks of the genus Dermacentor were the object of the study. The study was conducted on the basis of the Chair “Parasitology and Veterinary-Sanitary Expertise, Anatomy and Pathoanatomy named after Prof. S. N. Nikolsky” and the Scientific-Diagnostic and Medical Veterinary Center of the Federal State Budgetary Educational Institution of Higher Education "Stavropol State Agrarian University", as well as on the basis of veterinary clinics "Veterinary Center named after Pirogov” of the individual entrepreneur Zaichenko. The reproductive system of females served the material for the research. The females were treated and filled into paraffin according to the routine histological technique, afterwards the sections of 5-7 µm. thick were made. For routine examination, histological sections were stained with hematoxylin and eosin, as well as by Mallory staining method. Microscopic examination of the histological sections of female ticks was carried out using the Olympus BX53 microscope (Japan) at 4×, 20×, 40×, 100× magnification.Results. The macroscopic examination of female ixodid ticks of the genus Dermacentor showed that ovary is an azygos, horseshoe-shaped organ to which oocytes are attached. It was observed that oocytes develop asynchronously. Immature oocytes predominated mostly in the distal part of the ovary, while mature — in the proximal. The oocytes of this species of tick are classified by five main stages of maturation and are described based on the cytoplasm external view, the presence of the germinal vesicle, the presence of yolk granules and the chorion formation, and the morphometric data. The process of oocytes maturation at different stages is not linear. During vitellogenesis, the active and verified dynamics of growth is recorded from I to V stage of oocytes development the increase of their size by 55 times is observed.Discussion and conclusions. In female ticks of the genus Dermacentor, maturation of oocytes goes through 5 stages. The process of oocytes maturation at different stages is not linear, since both mitotic and meiotic processes occur simultaneously in the ovary. At the same time, in the oocytes development the active verified dynamics of growth is recorded.