While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the controlof an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be control...While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the controlof an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be controlled by a separateclock system. In the laboratory, this system drives clear activity rhythms throughout much of the year, not just during the matingseason when horseshoe crabs express clear tidal rhythms in the field. Water temperature is a key factor influencing the expressionof these rhythms: at 17℃ tidal rhythms are expressed by most animals, while at 11℃ expression of circatidal rhythms is rarelyseen, and at 4℃ rhythms are suppressed. Neither long (16:8 Light:Dark) nor short (8:16) photoperiods modify this behavior atany of these temperatures. Synchronization of these circatidal rhythms can be most readily effected by water pressure cycles bothin situ and in the lab, while temperature and current cycles play lesser, but possibly contributory, roles. Interestingly, Light:Darkcycles appear to have synchronizing as well as 'masking' effects in some individuals. Evidence that each of two daily bouts ofactivity are independent suggests that the Limulus circatidal rhythm of locomotion is driven by two (circalunidian) clocks, eachwith a period of 24.8h. While the anatomical locations of either the circadian clock, that drives fluctuations in visual sensitivity, orthe circatidal clock, that controls tidal rhythms of locomotion, are currently unknown, preliminary molecular analyses have shownthat a 71 kD protein that reacts with antibodies directed against the Drosophila PERIOD (PER) protein is found in both the protocerebrumand the subesophageal展开更多
文摘While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the controlof an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be controlled by a separateclock system. In the laboratory, this system drives clear activity rhythms throughout much of the year, not just during the matingseason when horseshoe crabs express clear tidal rhythms in the field. Water temperature is a key factor influencing the expressionof these rhythms: at 17℃ tidal rhythms are expressed by most animals, while at 11℃ expression of circatidal rhythms is rarelyseen, and at 4℃ rhythms are suppressed. Neither long (16:8 Light:Dark) nor short (8:16) photoperiods modify this behavior atany of these temperatures. Synchronization of these circatidal rhythms can be most readily effected by water pressure cycles bothin situ and in the lab, while temperature and current cycles play lesser, but possibly contributory, roles. Interestingly, Light:Darkcycles appear to have synchronizing as well as 'masking' effects in some individuals. Evidence that each of two daily bouts ofactivity are independent suggests that the Limulus circatidal rhythm of locomotion is driven by two (circalunidian) clocks, eachwith a period of 24.8h. While the anatomical locations of either the circadian clock, that drives fluctuations in visual sensitivity, orthe circatidal clock, that controls tidal rhythms of locomotion, are currently unknown, preliminary molecular analyses have shownthat a 71 kD protein that reacts with antibodies directed against the Drosophila PERIOD (PER) protein is found in both the protocerebrumand the subesophageal
