Lubomirskia baicalensis

Lubomirskia baicalensis is a freshwater demosponge that is found at depths between 3 and 120 m (10 and 394 ft) in Lake Baikal, Russia. It is commonly called Lake Baikal sponge and it is the most abundant sponge in the lake, but all 14 species in the family Lubomirskiidae are Baikal endemics. This sponge is in mutual symbiosis with a green dinoflagellate, making it green in appearance. Okadaic acid produced by the dinoflagellate assists the sponge to survive when Lake Baikal is iced over in winter, and the water temperature is close to 0 °C (32 °F). L. baicalensis can grow to a large size for a freshwater sponge, reaching a height of more than 1.2 m (4 ft) in some locations. It takes 1 year for it to grow 1 cm (0.39 in) taller.