On Coelenterata: Validation and Des­cription of the Superphylum Coelenterata (Leuckart, 1847)

Abstract

It has been suggested to combine the following three phyla of lower invertebrates in the superphylum Coelenterata (Leuckart, 1847): Plathelminthes Schneider, 1873, Cnidaria (Leuckart, 1847), and Ctenophora (Leuckart, 1847). Their representatives have a complete digestive tract, which forms a gastrovascular system performing the function of allocation of nutrients in addition to digestion. The mouth is located on the posterior end of the body in all coelenterates or in the most primitive forms. Attacks and protection are ensured by secretions of the specialized cells of the ectoderm that are reproducible due to the outer cambium of endodermal origin. Based on the above-described body plan organization and one of the variants of the parenchymal (or phagocytal) hypotheses, the phylogeny of lower invertebrates can be presented as described below. Their division into Pro- and Eumetazoa occurred at the parenchymal level of body organization in accordance with the competitive exclusion principle. Prometazoa retained the protozoan type of feeding (microphagia) and stayed at the parenchymal level of organization. Eumetazoa turned to macrophagia and active lifestyle in the near-bottom layers of water. As a result of the physiological differentiation of effort between the cells of kinoblast and phagocytoblast, bilateral symmetry and acoelous organization of the body (class Turbellaria from Plathelminthes). They initiated the development of Cnidaria with the bottom mode of life and Ctenophora dwelling in the pelagic zone. This approach makes it meaningless to distinguish animals into Bilateria and Radiata.

Keywords

• coelenterata
• gastrovascular system
• epithelial-muscular cells
• fully formed secretion
• external cambium