Anoxycalyx joubini
The giant volcano sponge (Anoxycalyx joubini) is a species of  Antarctic sponge. It is one of the largest sponge in the world which can grow up to a diameter of 1.5 metres (5 feet) and 1.95 metres (6.5 feet) in height. The species may have an extremely long lifespan, with estimates of up to 1,500 years. A. joubini occurs in deeper waters than the similar species Cinachyra antarctica, which is also very long-lived. Antarctic sponges live at  below the surface, in extremely cold temperatures and constant pressure. This may slow down their growth rate and other biological processes because one caught specimen of A. joubini, did not show any growth in a span of 10 years. References

Hexactinellida
Animals described in 1916
Marine fauna of Antarctica