A Bursatella leachii, or sea slugs, living in the coastal waters of Puerto Rico display a daily rhythm of behavior patterns. They tend to be found together the closest at midnight with an average distance of 8 centimeters away from each other, and as most isolated individuals at 4 P.M. with an average distance of 174 centimeters. They were observed to assemble following sunset approximately after 4 P.M. and to disperse in the morning after 8 A.M. with the greatest distances. The cycle repeats itself each day.

What could cause the slugs to vary their distance from each other? Three possible variables that could be responsible for such a pattern are 1) circadian rhythms, 2) feeding behaviors, 3) way of defending themselves against predators.

The circadian rhythm is the internal body clock that regulates the cycle of biological processes in animals and plants. It is important in determining the sleeping and...