Comparative Aspects of Structure and Function of Cnidarian Neuropeptides.

Toshio Takahashi

doi:10.3389/fendo.2020.00339

Abstract

Cnidarians are early-branching animals in the eukaryotic tree of life. The phylum Cnidaria are divided into five classes: Scyphozoa (true jellyfish), Cubozoa (box jellyfish), Hydrozoa (species, Hydra and Hydractinia), Anthozoa (sea anemone, corals, and sea pen), and Staurozoa (stalked jellyfish). Peptides play important roles as signaling molecules in development and differentiation in cnidaria. For example, cnidaria use peptides for cell-to cell communication. Recent discoveries show that Hydra neuropeptides control several biological processes including muscle contraction, neuron differentiation, and metamorphosis. Here, I describe the structure and functions of neuropeptides in Hydra and other cnidarian species. I also discuss that so-called primitive nervous system of Hydra is in more complex than generally believed. I also discuss how cnidaria use peptides for communication among cells rather than in higher animals.

Highlights

Molecular phylogenetic studies show that Cnidaria are the sister group of Bilateria
The primary aim of the present review is to describe the structures and functions of peptide signaling molecules such as neuropeptides in cnidarians, especially in Hydra
Neuropeptides released from nerve cells in response to a variety of stimuli are mandatory for fine-tuned regulation of behavior, reproduction, metamorphosis, and tissue maintenance (Figure 4)

Summary

Introduction

Molecular phylogenetic studies show that Cnidaria are the sister group of Bilateria. Ancestral Cnidarians diverged over 500 million years ago in animal evolution. Despite the long course of evolution, the nervous systems of cnidarians are differentiated [1]. Cnidarian species are mainly classified into two groups according to the unique life cycle, the anthozoans and medusozoans [1]. Cubozoa and Scyphozoa predominantly live as medusae. Hydrozoa usually follows a life cycle where the species alternate between these two forms except for Hydra and Hydractinia.

Objectives

Findings

Conclusion