Early development, pattern, and reorganization of the planula nervous system in Aurelia (Cnidaria, Scyphozoa) |
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Authors: | Nagayasu Nakanishi David Yuan David K Jacobs Volker Hartenstein |
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Institution: | (1) Department of Ecology and Evolutionary Biology, UCLA, 621 Young Drive South, Los Angeles, CA 90095-1606, USA;(2) Department of Molecular, Cellular and Developmental Biology, UCLA, 621 Young Drive South, Los Angeles, CA 90095-1606, USA |
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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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Keywords: | Cnidaria Scyphozoa Neurogenesis Planula Polyp |
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