New Evidence of the Freshwater Sponge Radiospongilla inesi (Nicacio & Pinheiro, 2011) in Net Cage Aquaculture Systems: A Case Study from Southeastern Brazil

We investigated the occurrence of Radiospongilla inesi in a tilapia aquaculture facility located at the Chavantes Reservoir, Paranapanema River, Brazil. Specimens were collected from both artificial (net cages) and natural substrates along the reservoir margins in October and November 2024. Morphological analyses of 8 sponge samples, including 20 structures per sample (gemmules, megascleres, microscleres and spicules), identified the species as Radiospongilla inesi (Spongillidae). This is the third documented record of R. inesi in Brazil, and the first within the Paraná River Basin and in aquaculture net cage systems. Morphological features were consistent between individuals from natural and artificial substrates, although gemmules were absent in specimens colonizing the cages. The proliferation of R. inesi poses biofouling challenges by obstructing cage mesh openings, reducing water flow and dissolved oxygen levels, and potentially compromising fish welfare and production efficiency. These impacts increase operational costs and highlight the need for sustainable management strategies in freshwater aquaculture. Additionally, this study raises questions regarding the species’ native status in the Paraná Basin versus potential invasive dispersal, emphasizing the need for further ecological and distributional investigations. Potential dispersal mechanisms and possible biofouling impacts are discussed, with recommendations for future quantitative and molecular studies.