MODIFICATION OF THE RESPONSES OF TWO SPECIES OF BUGULA LARVAE FROM WOODS HOLE TO LIGHT AND GRAVITY : ECOLOGICAL ASPECTS OF THE BEHAVIOR OF BUGULA LARVAE

Abstract

Larvae of Bugula flabellata and B. turrita. normally photopositive in diffuse light for the first 3-4 hrs. of larval life and then photonegative during the remainder, became photo-negative immediately when placed in sea water buffered to a pH of 9.6 or diluted by 50%; sea water containing CuCl2 either re-duced the intensity of their photopositive phase or reversed their phototropism depending on the concn. In mixtures of 80 cc. sea water/20 cc. of either N CaCl2 or N MgCl2 they were indifferent to light. More larvae (67%) attached in the red end of a test tube, one half of which was illuminated by red light and the other half by blue. The source was a 500-watt incandescent bulb; Wratten filters, no. 76 (transmitting wave lengths of approx. 4200-4800 A) and no. 72 (5800-6600 A), gave colored lights of approx. equal intensities. The excess of 17% in the red end is more than 5 times the S. E. p, 0.0292, obtained by the formula, [image] . Heating sea water to 30[degree]C favored surface attachment and hastened metamorphosis, but development was poor or lacking. Darkness favored surface attachment and delayed metamorphosis 2 or 3 days beyond the normal time; differentiation was poor. In mixtures of equal amts. of sea water and N soln. of NaCl, KCl, CaCl2 and MgCl2 the larvae became geopositive immediately and remained so during the expt.