DEVELOPMENT OF FLASHING BEHAVIOUR IN DYAKIA STRIATA

Abstract

Dyakia striata is the only known land pulmonate that exhibits true luminescence. Greenish - yellow light flashes are produced by a photogenic organ situated at the anterior region of the head - foot. Not all individuals are capable of light production. It is known that flashing behaviour of young snails differs from that of older snails (Haneda,1981). However, there has been little investigation of intermediate stages. The objective of this study was to document the pattern of the changes in the light output of the photogenic organ during development and to observe the rate of growth. The effects of time and temperature were also examined. The results indicate that larvae start flashing about three to four days after hatching and that flashing rates and intensities gradually decrease as the snail grows older. Time and temperature affected flashing rates, especially in older snails. Rates of flashing and intensities were ( highest in very young snails suggesting that flashing plays a more crucial role in juveniles.