Meeting Abstract
Cnidarians exhibit diel rhythms including cycles in locomotor activity, tentacle extension, and spawning. Behavioral and molecular studies conducted in corals and the anemone Nematostella vectensis suggest the presence of an endogenous circadian clock. In bilaterian animals, the circadian clock is intimately involved in regulating energetic metabolism; however, circadian regulation of metabolism has not been described in cnidarians. Because Nematostella exhibits greater locomotor activity at night, we hypothesized that oxygen consumption would also increase at night. To test this, we entrained Nematostella to a 12 h light : 12 h dark cycle (LD), a reversed light cycle (DL) or constant darkness (DD). Oxygen consumption rates were measured during intervals within 24-hour periods using an optical oxygen meter. Contrary to our prediction, respiration rates were highest during the light period under either the LD or DL cycles and during daytime under DD conditions. During a second experiment with higher temporal resolution, respiration rates peaked during subjective afternoon (ZT 6-12, where ZT 0 is 7 am, the time of subjective dawn). Our results suggest that respiration rates in Nematostella are under circadian control and that the cycle in respiration rate is not driven by the daily cycle in locomotor activity.
