Endogenous Twenty-Four Hour Rhythms of Locomotor Activity and Oxygen Consumption in the Crawfish Orconectes clypeatus

Abstract

Twenty-four hour rhythms of metabolic rate and locomotor activity have been observed in several crustaceans. Kalmus (1938) described a 24-hour locomotor activity rhythm in the crawfish Astacus astacus. The animal exhibited greater activity between 4 P.M. and midnight than at other times of day. By contrast, for several days after eyestalk ablation the Astacus were highly active throughout the 24-hour day and did not exhibit a 24-hour locomotor rhythm. Approximately 10 days after removal of the eyestalks the spontaneous locomotor activity of Astacus decreased to a level of very little activity at any time of day. Roberts (1941) observed a 24-hour locomotor activity rhythm in the crawfish Orconectes virilis. The rhythm disappeared in darkness. Eyestalkless specimens of this species also did not exhibit a locomotor activity rhythm. In constant darkness eyestalkless crawfish were recorded in fewer and shorter rest periods indicating that the animals were more active than normal. Schalleck (1942) observed 24-hour spontaneous locomotor activity rhythms in the crawfishes Orconectes virilis, Procambarus clarki, and Cdmbdrus diogenes, kept in constant darkness. He described three types of individuals in each species. One type was more active at midnight than at other times of day, the second was more active at noon than at other times of day, and the third type was more active at dawn and dusk than at other times of day. In general, specimens of the three species were more active at night than during the day. Eyestalkless individuals were continually active and showed no rhythm of locomotor activity. Edwards (1950) described 24-hour rhythms of metabolic rate and spontaneous locomotor activity in the fiddler crabs Ucd pugilator, U. pugnax, and U. minax. Their oxygen consumption was normally higher at night than during the daytime. The 24-hour cycle of locomotor activity closely corresponded with the cycle of oxygen consumption. Brown, Bennett, and Webb (1954) described in detail the endogenous 24-hour rhythms of oxygen consumption in the fiddler crabs U. pugilator and U. pugnax. The maximum oxygen consumption of specimens of both species occurred at 6-8 A.M. A second lesser maximum was found about 10-11 P.M. The minimum oxygen consumption occurred about noon and a lesser minimum occurred about midnight. Eyestalkless U. pugildtor also exhibited a persistent 24-hour rhythm of metabolic rate that differed slightly in form from that of normal indi1 This investigation was supported by Grant No. B-838 from the National Institutes of Health. 383