A new species of freshwater sponge (Porifera:Spongillidae) of the genus Radiospongilla from Lake Pedder in Tasmania

Lake Pedder is the home of a number of relictual organisms. One of those, a new species of freshwater sponge of the genus Radiospongilla, is described herein. Radiospongilla pedderensis sp. nov. occurs throughout most of the lake and often is found in very large numbers in many bays. Radiospongilla is widely distributed in tropical and sub-tropical regions of all continents. The pneumatic layer of the gemmule contains numerous abnormal gemmoscleres a condition probably caused by the chemistry of the lake. The morphology and dimensions of the megascleres, gemmoscleres and aberrant gemmoscleres, as well as the location, structure and size of gemmules, are provided for R. pedderensis. The sponge is a bright green colour due to intracellular zoochlorellae. Their presence in local members of Radiospongilla has been the subject of considerable speculation but herein they are illustrated for the first time in an Australian species.