Influence of rocky substrata on three-dimensional sponge cells model development.

Many marine and freshwater organisms are rocky bottom dwellers, and the mineralogical composition of the substratum is known to potentially condition their biology and ecology. In this work, we propose the use of 3D sponge cellular aggregates, called primmorphs, as suitable models for a multidisciplinary study of the mechanisms which regulate the biological responses triggered by the contact with different inorganic substrata. In our experiments, primmorphs obtained from the marine sponge Petrosia ficiformis (Poiret, 1789) were reared on calcium carbonate or on quartzitic substrata, respectively, and their morphological development was described. In parallel, the quantitative expression levels of two genes, silicatein and heat shock protein 70 (HSP70), were evaluated. The first gene is strictly correlated to spiculogenesis and sponge growth, while the second is an important indicator of stress. The results achieved with this in vitro model clearly demonstrate that quartzitic substrata determine the increase of silicatein gene expression, a lower expression of HSP70 gene, and a remarkable difference in primmorphs morphology compared to the analogous samples grown on marble.