On the functional significance of masking behaviour in sea urchins - an experiment with Paracentrotus lividus.

Much literature in marine biology describes the extraordinary behaviour of sea urchins, e.g., Paracentrotus lividus, who cover their body with shells, stones and debris. The function of this strange behaviour, described as 'masking', is still a puzzle. Our experiment shows that sea urchins are loaded with more mussel shells when the delicate apical openings of their water vascular system which powers all their movements, are in danger of being occluded by floating sand. 'Masking' shells appear to function as an umbrella against floating particles