The telotrophic ovary known from Neuropterida exists also in the myxophagan beetle <Emphasis Type="Italic">Hydroscapha natans</Emphasis> |
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Authors: | Email author" target="_blank">Jürgen?BüningEmail author |
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Institution: | (1) Developmental Biology Unit, Institute of Zoology, University of Erlangen-Nürnberg, Staudtstr. 5, 91058 Erlangen, Germany |
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Abstract: | The ovary structure of the myxophagan beetle, Hycdoscapha natans, was investigated by means of light and electron microscopy for the first time. Each of the two ovaries consists of three
ovarioles, the functional units of insect oogenesis. The ovary type is telotrophic meroistic but differs strongly from the
telotrophic ovary found among all polyphagous beetles investigated so far. All characters found here are typical of telotrophic
ovaries of Sialidae and Raphidioptera. Both taxa belong to the Neuropterida. As in all telotrophic ovaries, all nurse cells
are combined in an anterior chamber, the tropharium. The tropharium houses two subsets of germ cells: numerous nurse cell
nuclei are combined in a central syncytium without any cell membranes in between, surrounded by a monolayer of single-germ
cells, the tapetum cells. Each tapetum cell is connected to the central syncytium via an intercellular bridge. Tapetum cells
of the posterior zone, which sufficiently contact prefollicular cells, are able to grow into the vitellarium and develop as
oocytes. During previtellogenic and early vitellogenic growth, oocytes remain connected with the central syncytium of the
tropharium via their anterior elongations, the nutritive cords. The morphological data are discussed in the light of those
derived from ovaries of other Coleoptera and from the proposed sister group, the Neuropterida. The data strongly support a
sister group relationship between Coleoptera and Neuropterida. Furthermore, several switches between polytrophic and telotrophic
ovaries must have occurred during the radiation of ancient insect taxa. |
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Keywords: | Insect Oogenesis Ultrastructure Development Phylogeny |
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