Daytime light intensity affects seasonal timing via changes in the nocturnal melatonin levels

Daytime light intensity can affect the photoperiodic regulation of the reproductive cycle in birds. The actual way by which light intensity information is transduced is, however, unknown. We postulate that transduction of the light intensity information is mediated by changes in the pattern of melatonin secretion. This study, therefore, investigated the effects of high and low daytime light intensities on the daily melatonin rhythm of Afro-tropical stonechats (Saxicola torquata axillaris) in which seasonal changes in daytime light intensity act as a zeitgeber of the circannual rhythms controlling annual reproduction and molt. Stonechats were subjected to light conditions simulated as closely as possible to native conditions near the equator. Photoperiod was held constant at 12.25 h of light and 11.75 h of darkness per day. At intervals of 2.5 to 3.5 weeks, daytime light intensity was changed from bright (12,000 lux at one and 2,000 lux at the other perch) to dim (1,600 lux at one and 250 lux at the other perch) and back to the original bright light. Daily plasma melatonin profiles showed that they were linked with changes in daytime light intensity: Nighttime peak and total nocturnal levels were altered when transitions between light conditions were made, and these changes were significant when light intensity was changed from dim to bright. We suggest that daytime light intensity could affect seasonal timing via changes in melatonin profiles. Professor Dr. E. Gwinner died on 07 September 2004.     

Self-organization of circadian rhythms in groups of honeybees (Apis mellifera L.)

Workers in social groups of honeybees (Apis mellifera L.) synchronize their individual free-running circadian rhythms to an overall group rhythm. By monitoring the activity of bees by recording the oxygen consumption and intragroup temperature, it is shown that the rhythm coordination is in part achieved by temperature fluctuations as an intragroup Zeitgeber. Trophallaxis was shown to have only a minor (if any) effect on circadian rhythm synchronization. A model incorporating a feed back loop between temperature and activity can plausibly explain the observed synchronization of individual rhythms in social groups as a self-organization phenomenon. Correspondence to: R.F.A. Moritz     

Sex-dependent obesogenic effect of tetracycline on Drosophila melanogaster deteriorated by dysrhythmia

Antibiotics have been identified as obesogens contributing to the prevalence of obesity. Moreover, their environmental toxicity shows sex dependence, which might also explain the sex-dependent obesity observed. Yet, the direct evidence for such a connection and the underlying mechanisms remain to be explored. In this study, the effects of tetracycline, which is a representative antibiotic found in both environmental and food samples, on Drosophila melanogaster were studied with consideration of both sex and circadian rhythms (represented by the eclosion rhythm). Results showed that in morning-eclosed adults, tetracycline significantly stimulated the body weight of females (AM females) at 0.1, 1.0, 10.0 and 100.0 µg/L, while tetracycline only stimulated the body weight of males (AM males) at 1.0 µg/L. In the afternoon-eclosed adults, tetracycline significantly stimulated the body weight of females (PM females) at 0.1, 1.0 and 100.0 µg/L, while it showed more significant stimulation in males (PM males) at all concentrations. Notably, the stimulation levels were the greatest in PM males among all the adults. The results showed the clear sex dependence of the obesogenic effects, which was diminished by dysrhythmia. Further biochemical assays and clustering analysis suggested that the sex- and rhythm-dependent obesogenic effects resulted from the bias toward lipogenesis against lipolysis. Moreover, they were closely related to the preference for the energy storage forms of lactate and glucose and also to the presence of excessive insulin, with the involvement of glucolipid metabolism. Such relationships indicated potential bridges between the obesogenic effects of pollutants and other diseases, e.g., cancer and diabetes.     

Drowsy drivers: The effect of light and circadian rhythm on crash occurrence

Drowsiness has been recognized as a pervasive problem for drivers, with effects comparable to alcohol. Alcohol, however, has a clear legal limit for impairment; there are no comparable criteria to suggest sleepiness. Drowsiness has been associated with light and circadian rhythm. To investigate the joint effects of these factors on crash occurrence, along with other factors, single vehicle crashes reported in Ontario (1999–2004) were analyzed. Crashes occurring at four times of day, when light varies and circadian rhythm is low (2–5 a.m. and 2–4 p.m.) and with similar light conditions and higher circadian rhythm (9–11 p.m. and 10 a.m.–12 noon). Logistic regression was used to see how light and other factors are associated with single vehicle crashes occurring at times of low circadian rhythm, when drowsiness is more likely.Initial results indicated many circumstances associated with occurrence at these times: the age and sex of the driver and reported driver condition as well as weather. There is, however, an interaction between light and presumed alertness. In separate analyses for daytime and night time crashes most variables were significant for nighttime crashes but not for daytime events. The effects of alcohol and youth remained. A lack of light may exacerbate the effects of other factors at times of low alertness; this should be further investigated in controlled environments such as sleep laboratories and/or driving simulators.     

Fractionating dead reckoning: role of the compass,odometer, logbook,and home base establishment in spatial orientation

Rats use multiple sources of information to maintain spatial orientation. Although previous work has focused on rats’ use of environmental cues, a growing number of studies have demonstrated that rats also use self-movement cues to organize navigation. This review examines the extent that kinematic analysis of naturally occurring behavior has provided insight into processes that mediate dead-reckoning-based navigation. This work supports a role for separate systems in processing self-movement cues that converge on the hippocampus. The compass system is involved in deriving directional information from self-movement cues; whereas, the odometer system is involved in deriving distance information from self-movement cues. The hippocampus functions similar to a logbook in that outward path unique information from the compass and odometer is used to derive the direction and distance of a path to the point at which movement was initiated. Finally, home base establishment may function to reset this system after each excursion and anchor environmental cues to self-movement cues. The combination of natural behaviors and kinematic analysis has proven to be a robust paradigm to investigate the neural basis of spatial orientation.     

香溪河大型底栖动物24 h漂流规律研究

漂流行为是大型底栖动物适应河流水文过程的重要生物行为,也是研究河流底栖动物时空分布过程的重要依据,研究底栖动物的漂流规律对了解河流生态系统纵向格局的形成过程和演变机制具有重要意义.2017年8月选择湖北省香溪河的2条支流（九冲河与高岚河）研究大型底栖动物的漂流种类、昼夜节律和功能摄食类群构成.结果表明:①九冲河与高岚河漂流底栖动物均以蜉蝣目（Ephemeroptera）占绝对优势,相对丰度分别为76.9%、96.1%.九冲河的漂流物种数（35种）远高于高岚河（14种）.②优势物种分析表明,九冲河的优势物种为高翔蜉（Epeorus sp.）、弯握蜉（Drunella sp.）、四节蜉（Baetis sp.）、花翅蜉（Baetiella sp.）、扁蚴蜉（Ecdyonurus sp.）、沼石蛾（Limnophilidae sp.）、等翅石蛾（Philopotamidae sp.）和蚋（Simulium sp.）,高岚河的优势物种为花翅蜉和高翔蜉.③2条河流大型底栖动物的漂流均为显著的夜漂流类型,且漂流高峰期均出现在06:00.九冲河的夜漂者以襀翅目（Plecoptera）为主,高岚河以蜉蝣目为主.不同物种漂流的昼夜节律不同,高翔蜉、弯握蜉、扁蚴蜉、沼石蛾、等翅石蛾和蚋的第1个漂流密度高峰期均出现在20:00-22:00;四节蜉的第1个漂流密度高峰期出现在04:00-06:00;而花翅蜉的第1个漂流密度高峰期在九冲河出现的时间为04:00-06:00,在高岚河为02:00-04:00.④昼夜间漂流底栖动物的功能摄食类群和生活类型群落组成也有一定差异,但总体来看,漂流者的功能摄食类群均以收集者为主,以游泳生活者占主要优势.研究显示,九冲河与高岚河底栖动物的漂流节律表现出明显的差异性,其人为活动强度的差异是造成漂流规律差异的主要原因.      

关中盆地地-气系统灾变的节律性及耦合关系

依据丰富而系统的历史资料，建立了关中盆地历史地震与旱涝灾害两个数据库，分析了近2000a来地-气系统环境灾变的节律性及耦合关系。结果发现：(1)地震活动具有一定的节律性，并先后经历了3个平静期和3个活跃期，平静期与活跃期呈交替出现，具有3～4个世纪的周期；(2)较为严重的干旱、洪涝灾害亦具有一定的周期性，先后经历了2个洪涝期和3个干旱期，其较长尺度的转换周期亦为3～4个世纪；(3)在世纪尺度上，地震活动与旱涝灾害具有某种耦合关系，表现为在地震活动的活跃期，旱涝灾害呈多发性，而在地震活动的平静期，旱涝灾害较为稀少；(4)以较大级别的地震群发为节点，地气系统环境灾变的耦合关系具有先旱→后震→再涝的演替特征。基于上述事实，提出了一个地-气系统环境灾变的概念模型，对地震与旱涝灾害的耦合关系给出了确定性解释。为关中盆地世纪尺度的环境灾变群发性预测提供了新的依据。     

Chronotoxicological studies on dichlorphos in mice and humans

Chronotoxicological studies were performed with dichlorphos (DDVP) and its timing toxic effects on mice and humans. The circadian rhythms were revealed in the blood cholinesterase (ChE) activity in intact mice and normal persons, as well as in mice mortality treated at different daily times. The inverse relationship of the two rhythm suggested that the risk of exposure to DDVP might be much higher at evening hours than in other clocks of the day, and the disappearance of the ChE rhythms in DDVP-treated mice and DDVP-exposed workers implicated a disturbing effect of DDVP on the maintenance and regulation of the rhythmic mechanisms.     

Circadian Rhythm of Heart Rate,Urinary Cortisol Excretion,and Sleep in Civil Air Traffic Controllers

The examination of Air Traffic Controllers (ATCs) from the Warsaw Airport (Poland) included 24-hr ECG monitoring. The participants were 10 civil ATCs, 9 males and 1 woman. The study was carried out on a group of 19 ATCs during their duty periods, 14 of them working 12-hr shifts and 5 performing 24-hr duties. The participants collected urine every 4 hrs, and Cortisol concentration was determined. Further, the survey included the quality and duration of sleep, and subjective fatigue in the 62 participants.

In ATCs, shift work modifies natural rhythms of the circulatory system and decreases the ability for intensified mental work at night. In consequence ATCs experience frequent sleep disorders.     

奥陶纪以来生物贝壳生长纹层与地月轨道参数的演化

通过显微镜、扫描电镜以及微量化学成分分析，对现代瓣鳃类粗饰蚶、花蛤和腹足类纺锤螺，第三纪美壳螺，三叠纪克氏蛤，石炭一二叠纪燕海扇，泥盆纪云南贝、颠石燕，奥陶纪震旦角石、赫南特贝等贝壳生长纹层进行了综合研究。结果表明，奥陶纪以来贝壳生长纹层具有年、半年、双周、日、半日生长周期的变化，年中所含双周生长纹层数、双周所含日生长纹数均呈递减的趋势。通过观测计算得出：奥陶纪每年的日数为415．69d，泥盆纪为407．1d，石炭一二叠纪为400．51d，三叠纪为393．98d，第三纪为374．13d，第四纪为367．4d，表明白奥陶纪以来有地球自转速度变慢、地月距离增大、月球后退速率减小等变化趋势，