ISSN:
1573-5117
Keywords:
Hydrozoa
;
Scyphozoa
;
Anthozoa
;
5S ribosomal RNA
;
phylogeny
;
evolution
;
body plan
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00026505
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