SURFACE ILLUMINATION AND BARNACLE ATTACHMENT

¹ University of Miami Marine Laboratory

1. Experiments were designed for the purpose of investigating the various anomalies reported in the response of barnacle larvae to black and to white surfaces. The apparatus consisted of panels of similar size but checkered with black and white squares of sides varying from eight inches to one inch.

2. Average attachment density over the entire panel increased slightly with diminishing size of squares. Attachment density to white squares increased with diminishing size of squares. Attachments to black squares did not vary continuously with size of squares. The distribution ratio between black and white decreased from over 3 on eight-inch squares to unity on 2-inch squares.

3. As an explanation of the results and of previously reported anomalies it is suggested that cyprids are stimulated to attachment by a low optimum light intensity of light, and that diffuse light rather than unidirectional light is the principal factor involved.