The giant spicule of the sponge

The results of new research on the giant siliceous basal spicule of the deep water sponge Monorhaphis chuni complemente and partially undermine previous observations and interpretations of the structure of these spicules. We identified and described four morphologically and structurally different layers/zones in its construction, explained their relations, and proposed their functional role. As a result, we proposed a new model of growth of the basal spicule of Monorhaphis chuni, substantially different from the model that is currently accepted. At the same time, we showed that the spicule of Monorhaphis cannot be a structural model for other spicules of hexactinellid sponges, because of its unique function which determines its structure..