COMBINATIVE VARIABILITY IN THE TREMATODAS

Abstract

Objective: To study the combinational variability in trematodes based on micromorphological studies of their gametogenesis and fertilization.Trematodes: Fasciola hepatica, Opisthorchis felineus, Clonorchis sinensis, Paragonimus westermani were obtained by dissecting animals. Trematode marites were fixed in 10% neutral formalin. The treatment was carried out according to the histological method. The material was embedded in paraffin. Sections of 5–6 microns thick were stained using histological methods of staining: hematoxylin Carazzi-eosin, gallocyanin, azur-eosin according to Romanovsky-Giemsa. 400 histological specimens were manufactured; studied under a light microscope and took photomicrographs.Trematodes are characterized by true hermaphroditism. In each individual of the trematode, the sex glands are well developed – the testes and ovaries, in which the processes of gametogenesis take place: spermatogenesis and ovogenesis. As a result of gametogenesis, due to meiotic crossing-over, genetic material recombines, and trematode sex cells are formed with a unique genome. Two trematodes participate in fertilization, which, mating, fertilize each other in a cross way (simultaneous fertilization). As a result, the genetic material of each trematode is updated and a new generation of individuals with a new genotype ripens in each of them. The constant updating of the trematode genomes forms the basis of combinational variability and ensures the prosperity of species.