Abstract
The isolated and purified aggregation factor of the siliceous sponge Geodia cydonium has been shown to act species-specifically in combination with three horny sponges (one of them: Ircinia muscarum), but unspecifically towards a variety of other sponge species to be classed with Calcispongiae, Demospongiae and Keratosa. The property of the Geodia aggregation factor to cause aggregates only with isolated Geodia cells and not with Ircinia cells is not determined by the aggregation factor itself, but by substances which are located on the cell surfaces of the mucoid cells from Ircinia. The Ircinia inactivator, capable to inactivate the Geodia aggregation factor, has a molecular weight of 9800 D and behaves like a protein: first it can be inactivated by heat, extreme pH conditions and by pronase and second it has a buoyant density of 1.39± 0.04 g/cm 3. The inactivation of the Geodia aggregation factor by Ircinia cells can be prevented by preincubation of the aggregation factor with reagents for thiol groups. The bonding of the Geodia aggregation factor to Ircinia cells can be split by adding excess of the thiol compound dithiothreitol. From the results presented it is supposed that the Geodia aggregation factor is bound to Ircinia mucoid cells via disulfate linkages. The biological relevance of the finding that the capacity of the Geodia aggregation factor is limited by alien cells can be seen in a defence mechanism of the Ircinia organism against gemmules from Geodia.
Published Version
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