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The cellular organization ofConvoluta convoluta, an acoel turbellarian: A cytological, histochemical and fine structural study

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Summary

A cytological (light microscopical, cytochemical and fine structural) analysis of the cellular organization of the acoel turbellarianConvoluta convoluta (Abildgaard) is presented. The controversial problem as to the cellular organization has been clarified. The animal has been found to be composed of cells, and contrary to what is usually supposed it is not syncytially or plasmodially organized.

Descriptions are given of the epidermal cells, muscle cells and the different cell types in the peripheral and central (digestive) parenchyma. Using methods for acid mucopolysaccharides a differentiation between the peripheral and central parenchyma is easily obtained, the central parenchyma exhibiting the strongest reactions.

The main cell type in as well the peripheral as the central parenchyma is a large branched cell containing mucopolysaccharides. All cells in the animal are closely apposed, leaving no extracellular space except for the few hundred Å wide space usually found between apposing cells. No intercellular filaments or extracellular matrix have been observed.

In the peripheral parenchyma two cell types are present besides the large, branched cells. One contains centrally a dense, small nucleus which is surrounded by a sparse dense cytoplasm which gives off numerous extremely thin and branching processes. Another type is reminiscent of the neoblasts found in triclad turbellarians.

In the posterior part of the animal acaudal cell pad is described and its significance discussed.

The morphological and cytochemical observations are discussed in relation to physiological activities of the animal. Also the significance of the proposed interpretation of the cellular organization for terminological and phylogenetic problems is considered.

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Authors and Affiliations

  1. Institute of General Zoology, University of Copenhagen, Denmark

    Knud Jørgen Pedersen

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  1. Knud Jørgen Pedersen
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Acknowledgments. The kind help of Prof.G. Thorson andMrs. Birgitte Kanneworff, M. Sc., The Marine Biological Laboratory, Elsinore, in obtaining the animals is greatly appreciated.

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Pedersen, K.J. The cellular organization ofConvoluta convoluta, an acoel turbellarian: A cytological, histochemical and fine structural study. Z.Zellforsch 64, 655–687 (1964). https://doi.org/10.1007/BF01258542

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  • DOI: https://doi.org/10.1007/BF01258542

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