First Modern Record of a Freshwater Sponge from South Africa’s East Coast

By Dr Dylan Clarke Curator of Marine Invertebrates and Dr Toufiek Samaai Marine Biology Honorary Research Associate – Both Iziko Museum of South Africa A recent study by researchers from Iziko Museums of South Africa and international collaborators has documented the occurrence of the freshwater sponge Ephydatia fluviatilis in Lake Sibaya, located within KwaZulu-Natal’s internationally recognised iSimangaliso Wetland Park. The finding provides important new insights into South Africa’s poorly understood freshwater sponge fauna and demonstrates the value of integrating museum collections, field research and molecular science to better understand the country’s biodiversity. Freshwater sponges are among the least studied aquatic animals in Africa. While they may appear inconspicuous, these organisms play an important ecological role in freshwater ecosystems by filtering water and creating habitats for other aquatic organisms. Despite their global distribution, relatively few freshwater sponge species have been recorded in South Africa, and many historical records have never been revisited using modern scientific methods. The newly documented specimen of Ephydatia fluviatilis was discovered attached to a submerged mooring line at a depth of approximately 28 metres in Lake Sibaya, South Africa’s largest natural freshwater lake. The sponge exhibited a distinctive branching growth form and was characterised by numerous small openings through which water circulates as part of its filter-feeding process. The specimen was collected and deposited in the natural history collections of Iziko Museums of South Africa, where it will be permanently curated and made available for future scientific research. Museum collections such as these are essential repositories of biodiversity knowledge, preserving evidence of species occurrences and enabling future generations of researchers to revisit material as scientific methods continue to evolve. To confirm the identity of the sponge, researchers combined traditional taxonomic techniques with modern DNA sequencing. Detailed microscopic examination of the sponge’s skeletal structures revealed characteristics consistent with Ephydatia fluviatilis, one of the most widely distributed freshwater sponge species in the world. Genetic analyses further confirmed the identification and demonstrated links with other South African populations of the species. The discovery is significant because it represents one of the first modern, integrated morphological and molecular investigations of a freshwater sponge from South Africa’s east coast. It also highlights how little is currently known about freshwater sponge diversity across the region. The researchers suggest that many additional populations may exist in lakes, rivers, wetlands and reservoirs throughout southern Africa but remain undocumented due to limited sampling and specialist expertise. Importantly, the study demonstrates the growing role of molecular techniques in biodiversity research. DNA sequencing allows scientists to verify species identifications, uncover hidden diversity and better understand how populations are connected across landscapes and continents. When combined with traditional taxonomy and museum collections, these approaches provide powerful tools for documenting and conserving biodiversity. Lake Sibaya, situated within the iSimangaliso Wetland Park World Heritage Site, is renowned for its exceptional ecological diversity and unique freshwater ecosystems. Discoveries such as this emphasise the importance of protecting these habitats, which continue to yield new scientific knowledge and support a remarkable array of plant and animal life. For Iziko Museums of South Africa, the discovery reinforces the institution’s ongoing commitment to collections-based research and biodiversity documentation. As scientists continue to explore South Africa’s inland waters, new findings such as Ephydatia fluviatilis remind us that even familiar landscapes can still hold important scientific surprises. The study contributes valuable new knowledge to the understanding of Africa’s freshwater biodiversity and underscores the vital role that research collections play in advancing science, conservation and environmental management.