Tilden Andrea R, Shanahan J Kearney, Khilji Zahra S, Owen Jeffrey G, Sterio Thomas W, Thurston Kristy T
Biology Department, Colby College, 5720 Mayflower Hill, Waterville, Maine 04901, USA.
J Exp Zool A Comp Exp Biol. 2003 May 1;297(1):80-7. doi: 10.1002/jez.a.10230.
The influence of melatonin on locomotor activity levels was measured in the fiddler crab Uca pugilator. First, activity in untreated, laboratory-acclimated crabs was measured over 48 hours in a 12L:12D photoperiod; this study showed a nocturnal increase in activity. In eyestalk-ablated crabs, overall activity was significantly reduced, and no significant activity pattern occurred. Next, crabs were injected with melatonin or saline (controls) at various times during the 12L:12D photoperiod (0900h, 1200h, and twice at 2100h; each trial was separated by 3-4 days) and monitored for 3 hr post-injection. Control crabs had low activity during early photophase, high at mid-photophase, increasing activity during the first scotophase trial, and decreasing activity during the second scotophase trial. Melatonin had no significant influence on activity when injected during the early-photophase activity trough or early-scotophase activity decline, but significantly increased activity when injected during the mid-photophase activity peak and early-scotophase activity incline. Next, crabs were injected during an early scotophase activity trough and monitored throughout the twelve-hour scotophase. Melatonin did not increase activity until the mid-scotophase activity increase, approximately 6 hours later, showing that the pharmacological dosage persisted in the crabs' systems and had later effects during the incline and peak of activity but not the trough. Eyestalk-ablated crabs were injected with melatonin or saline during early photo- and scotophase. Melatonin significantly increased activity in the photophase but not the scotophase trial, indicating that the responsiveness to melatonin continues following eyestalk removal, but the timing may not match that of intact crabs. Melatonin may be involved in the transmission of environmental timing information from the eyestalks to locomotor centers in U. pugilator.
在招潮蟹中测量了褪黑素对运动活动水平的影响。首先，在12小时光照：12小时黑暗的光周期下，对未经处理、已适应实验室环境的螃蟹进行了48小时的活动测量；这项研究显示活动在夜间增加。在切除眼柄的螃蟹中，总体活动显著减少，且没有明显的活动模式。接下来，在12小时光照：12小时黑暗的光周期中的不同时间（09:00、12:00以及21:00注射两次；每次试验间隔3 - 4天）给螃蟹注射褪黑素或生理盐水（对照组），并在注射后监测3小时。对照螃蟹在光照前期活动较低，光照中期活动较高，在第一次暗期试验期间活动增加，在第二次暗期试验期间活动减少。在光照前期活动低谷期或暗期早期活动下降期注射褪黑素时，对活动没有显著影响，但在光照中期活动高峰期和暗期早期活动上升期注射时，显著增加了活动。接下来，在暗期早期活动低谷期给螃蟹注射，并在整个12小时暗期进行监测。褪黑素直到大约6小时后的暗期中期活动增加时才增加活动，这表明药理学剂量在螃蟹体内持续存在，并在活动上升期和高峰期产生后期影响，但对低谷期没有影响。在光照期和暗期早期给切除眼柄的螃蟹注射褪黑素或生理盐水。褪黑素在光照期试验中显著增加了活动，但在暗期试验中没有，这表明切除眼柄后对褪黑素的反应性仍然存在，但时间可能与完整螃蟹的不同。褪黑素可能参与了从眼柄到招潮蟹运动中心的环境时间信息的传递。
