Abstract
The ‘Schlauchdrüsen’ or paracnids of Coelogynopora axi Sopott, 1972 consist of two components: a muscle cell and a secretory cell.
The secretory cell is provided with a tube, which bears a border of microvilli. In the normal position the tube is situated in the interior of the secretory cell, and the microvilli stand at the inner side of the tube. After expulsion of the tube the microvilli are situated at its free surface.
The evagination takes place in response to chemical stimuli and is effected by the contraction of the myofibrils of the muscle cell.
The paracnids are supposed to be mechanisms of defense.
However, conformities with nematocysts and spirocysts of the cnidarians do not exist.
The paracnids in other species of the Coelogynoporidae, for example in Invenusta paracnida (Karling, 1966) and Carenscoilia bidentata Sopott, 1972 differ from those of C. axi in many details.
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Abbreviations
- bl-:
-
basement lamina
- ep-:
-
epidermis
- hd-:
-
hemidesmosomes
- mc-:
-
muscle cell
- mt-:
-
microtubules
- mv-:
-
microvilli
- nsc-:
-
nucleus of the secretory cell
- sb-:
-
bowl containing secretion granules
- sc-:
-
secretory cell
- sd-:
-
septate desmosome-like structures
- sg-:
-
secretion granules
- t-:
-
tube
- tf-:
-
tonofilaments
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Sopott-Ehlers, B. Ultrastructural observations on paracnids. I: Coelogynopora axi Sopott (Turbellaria, Proseriata). Hydrobiologia 84, 253–257 (1981). https://doi.org/10.1007/BF00026187
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DOI: https://doi.org/10.1007/BF00026187