Seasonal variation in the covering behaviour of the echinoid Paracentrotus lividus (Lamarck)

Covering behaviour is displayed by several regular echinoid species but its functional significance has yet to be quantified. Some of the most popular theories have interpreted this behaviour as an adaptive response to avoid over-exposure to light and/or as an anti-predator strategy. Since both predation pressure and light intensity may be seasonal as well as diurnal in nature, the aim of the present study was to quantitatively examine, in situ, the potential seasonality of covering behaviour in the purple sea urchin, Paracentrotus lividus (Lamarck). Data were collected over a one-year period at Lough Hyne, Co. Cork in Ireland. A peak in covering activity was observed over the summer months. Predator density and light intensity (sunlight hours) were also shown to vary seasonally at Lough Hyne. Covering behaviour in P. lividus, as in other echinoids, may be a response to a number of simultaneously interacting factors. At Lough Hyne, however, light intensity and covering item availability appear to be particularly important factors.