CROATIAN UNDERSEA WORLD IV, sea orange I PRINT

Sea orange (Suberites domuncula) Sea orange (Suberites domuncula) is almost always found in symbiosis with a hermit crab. Their cohabitation begins in the early life phase of the hermit crab. A young crab inhabits an empty marine gastropod shell, to which the sponge larva then attaches. The sponge grows and it overgrows the gastropod shell over time. Since the crab still grows, the shell becomes too small for him, so he abandons it, inhabiting the inside of the sponge. Although abandoned, the gastropod shell still remains within the sponge. Thus the sponge becomes the home to the crab, always matching its dimensions through its growth. In addition, the sponge produces toxins so there are no animals that feed on it, protecting in that way the hermit crab as well. The symbiosis is also beneficial for the sponge in several ways. The crab transports it to various places, providing it with better conditions to obtain food from sea water; in case of danger it flees together with the sponge. The sponge usually reaches 5 cm in diameter. Its colouring is mostly light orange, but it can also be blue, white, brown, yellow or it can feature a combination of colours. As a response to stress, it can shrink to less than 50% of its volume. It can often be found in northern Adriatic, on sandy and muddy seabeds, where it was first described as a species in 1792.