Dead-end evolution of the Cnidaria as deduced from 5S ribosomal RNA sequences |
| |
Authors: | Hori H Satow Y |
| |
Institution: | (1) Center of Marine Biotechnology, Univ. of Maryland, 600 East Lombard St., 21202 Baltimore, MD, USA;(2) Dept. of Genetics, Gen-Iken, Hiroshima Univ., 734 Kasumi, Hiroshima, Japan |
| |
Abstract: | Using nucleotide sequences of 5S ribosomal RNAs from 2 hydrozoan jellyfishes, 3 scyphozoan jellyfishes and 2 sea anemones, a phylogenetic tree of Cnidaria has been constructed to elucidate the evolutionary relationships of radial and bilateral symmetries. The 3 classes of Cnidaria examined herein belong to one branch, which does not include other metazoan phyla such as the Platyhelminthes. The Hydrozoa (having radial symmetry without septa) and the Scyphozoa (having radial symmetry with septa) are more closely related to each other than to the Anthozoa (having bilateral symmetry with septa). In classical taxonomy, multicellular animals are considered to have evolved through organisms with radial symmetry (e.g., Cnidaria) to bilateral symmetry. Our results, however, indicate that the emergence of the Bilateria was earlier than that of the Radiata, suggesting (in opposition to Haeckel's view) that the radial symmetry of Cnidaria is an evolutionary dead end. |
| |
Keywords: | Hydrozoa Scyphozoa Anthozoa 5S ribosomal RNA phylogeny evolution body plan |
本文献已被 SpringerLink 等数据库收录! |
|