On 7th January 2018 Anne and Grant Nicoll from Nedd found a number of these curious orange sponge-like objects along the shoreline at Raffin (NC0131). They are up to 7cm across, firm, leathery in texture and multi-lobed. The upper surfaces have a tight pattern of fine holes, with an occasional larger one and the undersides show signs of having been attached to a smooth surface.
They do in fact appear to be detached examples of a sponge known as the sea orange Suberites sp. There are two closely related species S. domuncula and S. ficus, distinguished by the microscopic characters of the siliceous spicules making up their internal skeleton.
Sea oranges are widespread around British coasts, usually below low water mark. They are said to be ‘frequently associated with whelk shells occupied by hermit crabs’, where ‘the sponge may gradually dissolve away the whelk shell to provide the crab with shelter directly’. In these circumstances the growth form is ‘globular and up to 30cm in diameter’, but ‘occasionally it is less round and encrusts rocks and piles, etc.’
These examples fit the latter case, and were presumably loosened by recent gales from rocky substrates offshore.
Ian M. Evans