Design for large-scale maricultures of the Mediterranean demosponge Chondrosia reniformis Nardo, 1847 for collagen production

To support the use of marine demosponges for collagen production in integrated culture settings, we investigated a low-cost, easily applicable and sustainable production method for the culture of Chondrosia reniformis Nardo, 1847 (Demospongiae, Chondrosiida, Chondrosiidae). Novel methods were tested to culture this collagen-rich demosponge in three consecutive trials, during which recovery, survival and growth rates of explants were monitored cultured within a site with organic pollution site (urban water discharge) and a pristine site. During Culture Trial 1, orientation of the culture plates had a significant main effect on growth rates of glued explants, with vertically mounted explants showing faster growth compared to horizontal ones (range 63 +/- 46% to 116 +/- 54%). However, vertically glued explants detached more compared to horizontal ones (30% versus 7%), which was not the case for nailed explants where only 3% detached regardless of orientation. Thus, vertically nailed explants yielded overall highest success rates. An interactive effect of substrate and attachment method on sponge growth rates was also found: glued sponges growing faster on PVC and polypropylene (PP) as compared to iron as substrate, for nailed sponges no growth differences were found between substrates. During Trial 2, no growth differences between sites or orientation were found, although similar to Trial 1, vertically cultured explants showed higher detachment rates (40-52%) and lower survival Based on to the results of Trials 1 and 2, the combination PP/nail/horizontal was ultimately selected for scale up in Trial 3, with explants as well as colonies. Culture Trial 3 revealed survival rates of 75-92% for explants and 83-100% for colonies after 467 days of culture. Growth rates were similar at the polluted and pristine sites for both explants facing up/down (range 126 +/- 99% to 218 +/- 139%) and colonies (range 128 +/- 60% to 226 +/- 325%). These consecutive culture trials spanning 2 years yielded consistent growth rates and high survival rates over 1 year of culture, both under pristine and polluted conditions. We here report the successful culturing method for a collagen production pipeline using C. reniformis. The final 'Demosponge lantern' design, is simple, sustainable, enhances productivity and is adaptable to seawater environments combined with sources of variable organic particle load such as fish culture or sewage outfall.