Abstract
We examined the development of the nervous system in Aurelia (Cnidaria, Scyphozoa) from the early planula to the polyp stage using confocal and transmission electron microscopy. Fluorescently labeled anti-FMRFamide, antitaurine, and antityrosinated tubulin antibodies were used to visualize the nervous system. The first detectable FMRFamide-like immunoreactivity occurs in a narrow circumferential belt toward the anterior/aboral end of the ectoderm in the early planula. As the planula matures, the FMRFamide-immunoreactive cells send horizontal processes (i.e., neurites) basally along the longitudinal axis. Neurites extend both anteriorly/aborally and posteriorly/orally, but the preference is for anterior neurite extension, and neurites converge to form a plexus at the aboral/anterior end at the base of the ectoderm. In the mature planula, a subset of cells in the apical organ at the anterior/aboral pole begins to show FMRFamide-like and taurine-like immunoreactivity, suggesting a sensory function of the apical organ. During metamorphosis, FMRFamide-like immunoreactivity diminishes in the ectoderm but begins to occur in the degenerating primary endoderm, indicating that degenerating FMRFamide-immunoreactive neurons are taken up by the primary endoderm. FMRFamide-like expression reappears in the ectoderm of the oral disc and the tentacle anlagen of the growing polyp, indicating metamorphosis-associated restructuring of the nervous system. These observations are discussed in the context of metazoan nervous system evolution.
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Acknowledgements
We thank Mike Schaadt and Kiersten Darrow of the Cabrillo Marine aquarium, San Pedro, CA, for providing us with the Aurelia material. This work was supported by the UCLA Edwin W. Pauley fellowship (to N.N.) and the NASA Astrobiology Institute. We also thank anonymous reviewers for helping us to improve the clarity of the manuscript.
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Communicated by M.Q. Martindale
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Nakanishi, N., Yuan, D., Jacobs, D.K. et al. Early development, pattern, and reorganization of the planula nervous system in Aurelia (Cnidaria, Scyphozoa). Dev Genes Evol 218, 511–524 (2008). https://doi.org/10.1007/s00427-008-0239-7
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DOI: https://doi.org/10.1007/s00427-008-0239-7