Dissociation–Reaggregation Experiments in Cnidarians as a Model System for the Study of the Regulative Capacity of Metazoan Development

Abstract

Developmental processes of cnidarians, representatives of the basal metazoan, possess extremely high regulative ability. It is known that any isolated fragment of the freshwater polyp hydra’s body can regenerate an intact animal. Moreover, in many cnidarian species, the suspension of single dissociated cells can form aggregates, which regenerate the normal body plan of a polyp or a medusa. This process can be considered an extreme case of regeneration. The development of cell reaggregates of Hydra is a conventional experimental system to study the physical basis of morphogenesis. Studies of the cnidarians’ reaggregate development help to clarify the basic rules and mechanisms of the metazoan body-plan formation and the role of selforganization in the metazoan early development. In this review, we summarize the data revealed by dissociation–reaggregation experiments performed on representatives of different cnidarian taxa. We also analyze the data on the morphogenetic and molecular basis of the reaggregate development from a randomly organized group of cells to the cnidarian-specific body plan.