Activite mecanique comparee des huitres portugaises et des Ciones, Epibiontes.

The Portuguese oyster (Crassostrea angulata) and the sea-squirt Ciona intestinalis are both filter-feeders and compete for space in the oyster beds. Valve movement in oysters and shortening and elongation in Ciona were recorded on a smoked drum. Oysters showed a slow (3 one half min) spontaneous opening/closing rhythm, which was speeded up by stimulatory (vitamin) substances and increased in amplitude by toxic accumulated waste substances, or sudden change in temperature. Ciona showed a regular contraction rhythm of similar to 1 min and single sharp shortening after a strong light stimulus or a food particle touch stimulus to the oral tentacles. The neural ganglion discharges spikes 3 times faster than in the dark, after light stimulation. Filtration rates of the 2 organisms seem to be similar.