Khoa Vo
Effect of Artificial Night Lighting and Time on Aquatic Snail (Physa acuta) Activity Patterns. Khoa Vo, Thomas McCarthy, Bryant Buchanan and Sharon Wise
Light pollution (artificial night lighting) affects the behavior of many vertebrate and insect species. However, few studies have examined the effect of artificial night lighting on behavior of aquatic invertebrates. Physa acuta is a common aquatic snail found throughout North America. We investigated the activity of P. acuta exposed to a 14L:10D photoperiod with 100 lx illumination during photophase (diurnal) and illuminations of 100 lx (daylight), 1 lx (dim daylight), 0.01 lx (full moon light), and 0.0001 lx (dark night) during scotophase (nocturnal). Infrared cameras were used to record snail movements at 0700-0900 h, 1230-1330 h, 1700-1900 h, and 0030-0130 h. We found no differences in activity due solely to variation in nocturnal light levels. Snails did show significant variation in activity based on time of day with more activity during the dark-to-light transition period (0700-0900 h) than during the light-to-dark transition period (1700-1900 h). There was no difference in activity between mid-photophase (1230-1330 h) and mid-scotophase (1700-1900 h). We did find a significant interaction effect of night lighting treatment by time: only snails exposed to the dark night treatment (0.0001 lx) showed significant variation in activity between the light-to-dark and dark-to-light transition periods; those in the continuous lighting treatment (100 lx) showed relatively low activity during both transitional periods. These results suggest that individuals of P. acuta are crepuscular (being more active at dawn than during other periods) and that constant bright light at night (constant day-night lighting) may reduce snail activity at dawn.