Embryonic development and metamorphosis of the scyphozoan <Emphasis Type="Italic">Aurelia</Emphasis> |
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Authors: | David Yuan Nagayasu Nakanishi 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;(3) Department of Molecular, Cell, and Developmental Biology, UC Los Angeles, Los Angeles, CA 90095, USA |
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Abstract: | We investigated the development of Aurelia (Cnidaria, Scyphozoa) during embryogenesis and metamorphosis into a polyp, using antibody markers combined with confocal
and transmission electron microscopy. Early embryos form actively proliferating coeloblastulae. Invagination is observed during
gastrulation. In the planula, (1) the ectoderm is pseudostratified with densely packed nuclei arranged in a superficial and
a deep stratum, (2) the aboral pole consists of elongated ectodermal cells with basally located nuclei forming an apical organ,
which is previously only known from anthozoan planulae, (3) endodermal cells are large and highly vacuolated, and (4) FMRFamide-immunoreactive
nerve cells are found exclusively in the ectoderm of the aboral region. During metamorphosis into a polyp, cells in the planula
endoderm, but not in the ectoderm, become strongly caspase 3 immunoreactive, suggesting that the planula endoderm, in part
or in its entirety, undergoes apoptosis during metamorphosis. The polyp endoderm seems to be derived from the planula ectoderm
in Aurelia, implicating the occurrence of “secondary” gastrulation during early metamorphosis. |
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Keywords: | Cnidaria Scyphozoa Embryogenesis Planula Polyp |
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