THE INFLUENCE OF SURFACE ANGLE AND OF LIGHT ON THE ATTACHMENT OF BARNACLES AND OTHER SEDENTARY ORGANISMS

Abstract

In the curves describing the attachment of 6 groups of organisms in relation to the angle at which glass plates were held, the largest populations were always found at 0[degree] (the under surface of plates in the horizontal position) and the numbers decreased as the angle increased. The areas of 2 spp. of colonial bryozoans were likewise a function of the angle at which the plates were held, the greatest growth being at 0[degree]. This geotropic response was not found for the ivory barnacle, Balanus eburneus. Under conditions of natural day-night exposure, twice as many barnacles became attached to black as to opal or clear glass plates. In expts. conducted exclusively at night no difference was observed in the size of populations attached to black, opal or clear plates. This suggests that a photic factor is of primary importance in the attachment of this barnacle.