Dendrilla antarctica Topsent, 1905

Description

Mats of Dendrilla antarctica a few cm thick often carpet shallow rocky surfaces, sometimes extending over 3 or 4 square meters. Although the species is typically almost luminescent yellow it can have a variety of colour. Its prickly appearance makes it quite distinctive but it is does not feel spiky to touch, its tissue is soft and squashy. Other than the spiky texture it takes the form of whatever it is growing over, so when it encrusts macroalgae it often extends in lobes into the water column – slicing through a lobe reveals the alga inside entirely surrounded by the sponge. D. antarctica is a good competitor for space, so underneath encrusting sheets can often be found a wide variety of animals that it has suffocated. The tissues of this species have antibiotic properties and contain endosymbiotic diatoms. Frequently one or more individuals of the large sea slug A. kerguelenensis are seen on any large patches of the sponge. Occasionally found on the under-surfaces of boulders but if lifted out of the water it dries out to a thin yellow slime.