Spongilla lacustris

Spongilla lacustris is a species of freshwater sponge from the family Spongillidae that inhabits rivers and lakes, often growing on logs or rocks. Lacustris is a Latin word meaning "related to or associated with lakes".

Spongilla lacustris is a demosponge with a broad distribution ranging from North America to Eurasia. It is the most common freshwater sponge in Central Europe, is the most widespread sponge in Northern Britain, and is one of the most common species of sponges in lakes and canals. It has the ability to reproduce both sexually and asexually. They become dormant during winter. The growth form ranges from encrusting, to digitate, to branched, depending upon the quality of the habitat.