Homology relationships in Medusozoa (Cnidaria) based on the anatomy of the different stages of the life cycle

Abstract

Phylogenetic studies based on different data have shown that evolutionary relationships among cnidarian classes remain contentious. Consequently, different hypotheses suggest conflicting interpretations about the evolution of the life cycle in the phylum, with direct implications for understanding important innovations, including the origin and metamorphosis of the medusa stage. This project aims to establish homology relationships among the different stages of the life cycle of medusozoan classes, inferring the morphological evolution from dissonant evolutionary hypotheses. In order to achieve this purpose, we will: (1) comparatively describe the anatomical changes during the development for the different stages of the medusozoan life cycle; (2) infer the correspondence of the stages of the life cycle in Staurozoa with the polyp and medusa stages in the other medusozoan classes, verifying if/when metagenesis occurs in Staurozoa; (3) compare the evolution of the main morphological systems among the classes; (4) identify, in these models, expressions of the morphological diversity with historical origin (synapomorphic) in contrast to those with functional origin (homoplastic), based on the most recent phylogenetic proposals for Cnidaria. After reaching our aim, we will have an integrative and comparative view about the morphological evolution in Medusozoa. This is the first study to describe changes in the internal anatomy during the different stages of the life history stages, contributing to comprehend patterns and processes involved in the morphological evolution and diversification in Cnidaria. (AU)