Skeletal development in two species of Tethya (Porifera, Demospongiae)

Changes in skeletal structure occurring in differently sized specimens of t wo species of Tethya (T. aurantium and T. citrina) were studied. In the two species, differences in sponge consistency were found to be affected by th eir radial strongyloxeas skeleton and by aster sheets reinforcing their col lagenous ectosomes. In T. aurantium,body enlargement was enhanced by the pr oduction of new megasters, while in T. citrina a proliferation of strongylo xea bundles accompanied its growth. These differences are related to the di fferent ecological strategies of the two species. In both species, strongyl oxea length was clearly related to individual size.