ИСТИНА

There is a high abundance and diversity of the modes of asexual reproduction among the representatives of the class Scyphozoa. During some modes of asexual reproduction, the morphogenesis of main body parts goes independently of the body parts of the parent organism. During others – parental body parts are inherited by the offspring or transformed into body parts of the offspring. We summarized the data on the asexual reproduction in Scyphozoa, gained from literature and from our research on Aurelia (Semaeostomeae) and Cassiopea (Rhizostomeae). The relative orientation of the parental and offspring body axes, as we found out, varies significantly and the same body parts of the offspring can be formed from different parts of the parental organism. There are two main life forms in this group: sessile polyps and free-swimming medusae. The polyp-to-medusa transition, strobilation, goes through terminal budding, when already differentiated cells of polyp are used to build the medusa body parts. The tentacle bases expand to form the lobes of the first medusa, the polyp manubrium becomes the manubrium of the forming medusa. Our data confirms the homology between some tentacles of the polyp and the sensory organs (rhopalia) of the oralmost medusa. The manubrium, lobes and rhopalia in all subsequent medusae (in the case of polydisc strobilation) form independently from the structures of the parental polyp. Each disc of the future medusa is able to complete the development independently of the strobila. The polyp septa take part in determining the location and in the formation of the medusae structures. Remnants of septa are involved in the formation of gastric filaments of the medusae. The high plasticity of scyphozoan developmental processes can be explained by the assumption that in this group various types of asexual reproduction evolved from regeneration processes. The work was supported with RFBR Grant no. 19-04-01131.