Origin and evolution of the nervous system considered from the diffuse nervous system of cnidarians.

Abstract

Cnidarians have the most primitive nervous system in animal kingdom. Diffuse nerve net (called “diffuse nervous system”) covers the whole body. Cnidarians are considered the earliest metazoans to have evolved a nervous system and therefore offer possible insight into some of the fundamental properties of early nervous system. Recent studies show the cnidarian nervous system is much more complex than it was expected before. Genome projects and molecular developmental biological studies clarified indistinctness between Radiata and Bilateria. As to the nervous system, the situation is the same, namely there are many similarities between two animal groups. The cnidarian nervous system has all fundamental components with the molecular, morphological, and functional aspects. This might be also the case for the central nervous system, namely cnidarians are suggested to have primitive central nervous system.

I will make comprehensive description of the cnidarian nervous system based on morphological, functional, developmental studies in many biological levels from gene and molecule to individual, and compare with the concentrated nervous system of bilaterians. Subsequently, I will discuss the origin and evolution of the nervous system.