Diatom invasion in the antarctic hexactinellid sponge Scolymastra joubini

Sponges often host large amounts of symbionts, mainly represented by cyanob acteria and dinoflagellates. Recent findings show a widespread presence of symbiotic diatoms living inside antarctic demosponges. In this paper, the i nvasion by large populations of the diatom Melosira sp. into specimens of t he hexactinellid sponge Scolymastra joubini is reported. SEM analyses suppo rt the hypothesis that the embedded living diatoms have a negative impact o n sponge tissues, leading to degenerative processes.