Regeneration of planarians: Experimental object

We discuss the expediency of using invertebrates, such as flatworms and planarians, as experimen� tal objects. Freeliving planarian flatworms (phylum Plat yhelminthes, class Turbellaria) are invertebrate ani� mals in which a bilateral symmetry appears for the first time in evolution and organs and tissues form. As the highest ecological link of the food chain—predators—these animals are characterized by a set of behavioral reactions controlled by a differentiated central nervous system. Planarians have unsurpassed ability to regen� erate lost or damaged body parts. Owing to the ease of their cultivation and their convenience for manipula� tions, these animals are used to study the influence of chemical and physical factors on the processes of life, growth, and reproduction. Currently, planarians are recognized as a model for biological research in the field of regeneration, stem cell biology, study of their proliferation and differentiation, as well as the regulatory mechanisms of morphogenetic processes. The genome of the planarian Schmidtea mediterranea was fully sequenced, which opened up the opportunity to work with this object at the molecular biological level. Fur� thermore, planarians are used in neurobiological and toxicological studies, in studying the evolutionary aspects of centralization of the nervous system, mechanisms of muscle contraction, and in the development of new antiparasitic drugs. This review aims to demonstrate the relevance and diversity of research conducted on simple biological objects—planarians—to a wider audience to show the historical continuity of these studies and their wide geographical distribution and to focus on the studies carried out in Russia, which, as a rule, are not included in the foreign reviews on planarian regeneration.