ИСТИНА

Echiuran worms (Thalassematidae) are a special group of non–segmented annelids that lead a secretive lifestyle, hiding their bodies in burrows. Bonellia viridis Rolando, 1822 is an organism that performs environmental engineering. Studying morphology is one of the main ways to shed light on the physiology and ecology of these mysterious worms. This thesis is aimed at studying the morphology, microscopic anatomy and details of the ultrathin organization of organ systems in B. viridis females and their analysis in the light of the evolutionary, physiological and reproductive characteristics of the group. This study mainly aimed (1) to describe the colocalization and general histological organization of all organ systems, the fine structure of the organs of B. viridis females, (2) to conduct a comparative analysis of the data obtained and (3) to identify common patterns and features in the structure of the organ systems of echiurids in general and B. viridis in particular. This was achieved by using a set of morphological methods such as microCT, SEM, TEM, histological techniques. Autopsies and three-dimensional reconstructions of a series of sections were used to determine the colocalization of various organs and their microscopic anatomy. The main features of the organization of echiurids are associated with the loss of metameria and a special type of nutrition, the effectiveness of which allows echiurids to colonize oligotrophic waters of the world ocean. The revealed structural details of B. viridis females, which distinguish them from other echiurids, are primarily associated with the presence of large terminal proboscis lobes and associated additional functional structures, as well as with the features of reproductive biology: accelerated vitellogenesis and the presence of a large androecium, which is lined with glandular epithelium and provides attraction and nutrition for dwarf males.