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We performed a screening on 21 Mediterranean sponge species in order to know from which ones primmorphs can be obtained, with a comparison of their formation among the outputs. Thirteen species produced primmorphs, evidencing a high variability among species concerning the number and size of primmorphs, without evidencing any taxonomical specificity. Additionally, the formation process and trend of growth during 1 month of monitoring were studied from a quantitative point of view. The dynamics of primmorphs formation follow different patterns: slow and quick formation, short and long-time survival and in the case of long-time survival, the fission and fusion models are proposed. Besides these patterns, each analysed species showed characteristic trends in the time required for the aggregation of cells, the time required for the production of small primmorphs, growth fluctuation and the acquirement of a final stable size., Introduction Sponges are a widely represented phylum in the marine benthos (Sara and Vacelet 1973) and because of their primitive organization, they occupy a particular phylogenetic position among Metazoa (Muller [...]

The siliceous spicules of the Antarctic hexactinellid Rossella racovitzae were analyzed to determine if spicules allow light energy to reach the inside of the bodies of demosponges and hexactinellids. The results showed that the spicules can act as optical fibers and that larger light-capturing surfaces enhance the transmission of light. This ability to transfer light may be related to the survival of diatoms inside the sponge.