Persistence of Eclosion Rhythm in Drosophila melanogaster After 600 Generations in an Aperiodic Environment

 The ubiquity of circadian rhythms suggests that they have an intrinsic adaptive value (Ouyang et al. 1998; Ronneberg and Foster 1997). Some experiments have shown that organisms have enhanced longevity, development time or growth rates when maintained in environments whose periodicity closely matches their endogenous period (Aschoff et al. 1971; Highkin and Hanson 1954; Hillman 1956; Pittendrigh and Minis 1972; Went 1960). So far there has been no experimental evidence to show that circadian rhythms per se (i.e. periodicity itself, as opposed to phasing properties of a rhythm) confer a fitness advantage. We show that the circadian eclosion rhythm persists in a population of the fruitfly Drosophila melanogaster maintained in constant conditions of light, temperature, and humidity for over 600 generations. The results suggest that even in the absence of any environmental cycle there exists some intrinsic fitness value of circadian rhythms. Received: 2 November 1998 / Accepted in revised form: 22 April 1999     

Exposure to endocrine disrupting chemicals perturbs lipid metabolism and circadian rhythms

A growing body of evidence indicates that exposure to environmental chemicals can contribute to the etiology of obesity by inappropriately stimulating adipogenesis as well as perturbing lipid metabolism and energy balance. One potential mechanism by which chemical exposure can influence lipid metabolism is through disturbance of circadian rhythms, endogenously-driven cycles of roughly 24hr in length that coordinate biochemical, physiological, and behavioral processes in all organisms. Here we show for the first time that exposure to endocrine disrupting compounds (EDCs), including the pesticide tributyltin, two commercial flame retardants, and a UV-filter chemical found in sunscreens, can perturb both circadian clocks and lipid metabolism in vertebrates. Exposure of developing zebrafish to EDCs affects core clock activity and leads to a remarkable increase in lipid accumulation that is reminiscent of the effects observed for longdaysin, a known disruptor of circadian rhythms. Our data reveal a novel obesogenic mechanism of action for environmental chemicals, an observation which warrants further research. Because circadian clocks regulate a wide variety of physiological processes, identification of environmental chemicals capable of perturbing these systems may provide important insights into the development of environmentally-induced metabolic disease.     

Clocks for sex: loss of circadian rhythms in ants after mating?

This paper describes experiments on the locomotor activity rhythm of queens of the ant species Camponotus compressus, which were performed to investigate the consequences of mating on circadian clocks. Locomotor activity rhythm of virgin and mated queens was monitored individually under constant conditions of the laboratory. The locomotor activity rhythm of virgin queens entrained to a 24 h (12:12 h) laboratory light/dark (LD) cycle and free-ran under constant dim red light (RR) with a free-running period () of approximately 24 h. The locomotor activity of the mated queens on the other hand was arrhythmic during the period when they were laying eggs, and robust rhythmicity appeared soon after the egg-laying phase was over. The of the locomotor activity rhythm of mated queens was significantly greater than that of virgin queens. These results are contrary to the commonly held belief that the role of circadian clocks in ant queens ceases after mating flights, thus suggesting that circadian clocks of ant queens are adaptively plastic and display activity patterns, perhaps depending on their physiological state and tasks in the colony.     

A comparative review of entrainment survival studies at power plants in estuarine environments

Steam-electric power plants drawing cooling water from surface waters entrain a variety of plankton and weak-swimming nekton. These small organisms pass through the intake screens and are carried along with the cooling water through the plant and are subjected to thermal, physical, and chemical (biocide) stresses. In once-through cooling systems, entrained organisms are returned to the source water body, where they are subjected to rapidly decreasing temperatures as cooling waters are mixed into receiving waters. With 4316(b) of the Clean Water Act as the impetus, studies were conducted at many power plants to quantify the number of entrained organisms. Early studies focused on simple abundance, and assumed total mortality. By the late 1970s and early 1980s, advances in sampling technology demonstrated that many entrained organisms survived. Continuing refinement of sampling techniques revealed impressive survival statistics for many species (>90% in some cases), with concomitant reductions in perceived impacts. This paper reviews state-of-the-art sampling methods and results of field entrainment studies at seven power plants. This review demonstrates that high entrainment survival of a variety of aquatic organisms does, in fact, occur and specifies the plant-operating and environmental conditions under which high survival occurs.     

What is ‘normative’ at cooling water intakes? Defining normalcy before judging adverse

Judgments of adverse environmental impact from cooling water intake structures need to be preceded by an appreciation of what is normal. In its report, Return to the River, the Independent Scientific Group (now called the Independent Scientific Advisory Board) — the scientific peer review arm of the Northwest Power Planning Council — advanced the notion of a ‘normative river ecosystem’ as a new conceptual foundation for salmonid recovery in the Columbia River basin. With this perspective, the sum of the best scientific understanding of how organisms and aquatic ecosystems function should be the norm or standard of measure for how we judge the effects of human activities on aquatic systems. For the best likelihood of recovery, key aspects of altered systems should be brought back toward normative (although not necessarily fully back to the historical or pristine state); new alterations should be judged for adversity by how much they move key attributes away from normative or what might be considered normal. In this paper, I ask what ‘normative’ is for the setting of cooling water intake structures and how this concept could help resolve long-standing disputes between groups interested in avoiding damage to all organisms that might be entrained or impinged and those who take a more population or community perspective for judging adverse environmental impact. In essence, I suggest that if a water intake does not move the aquatic ecosystem outside the ‘normative’ range, based on expressions of normalcy such as those discussed, then no adverse impact has occurred. Having an explicit baseline in normal or normative would place 316(b) analyses on the same conceptual foundation as 316(a) analyses, which strive to demonstrate the continuation of a balanced, indigenous community of aquatic organisms at the power station location.     

Chronotype differences in Drosophila are enhanced by semi-natural conditions

Morning and evening chronotypes of sleep/wake cycles in humans are often metaphorically termed as ‘larks’ and ‘owls’. We derived Drosophila populations early and late, displaying lark- and owl-like emergence chronotypes by imposing selection for adult emergence during morning and evening hours. Preference for morning and evening emergence in these populations was accompanied by divergence in their circadian period (τ) and photic phase response curve. To test if lark- and owl-like emergence chronotypes displayed by these flies under weak environmental cycles of the laboratory would also persist in nature where several zeitgebers are present in the strongest form, we examined the emergence rhythm of early and late flies under semi-natural conditions. The early and late flies not only continued to exhibit divergent emergence waveforms under semi-natural conditions, the differences became even more prominent. However, phases of early and late emergence waveforms did not match natural morning and evening transitions, unlike that observed under laboratory conditions. These results thus provide evidence consistent with the notion that chronotypes are the result of interactions between circadian clocks and natural environmental cycles.     

Zelluläre Mechanismen der inneren Uhr eines Einzellers

Gonyaulax polyedra, many different circadian rhythms have been described in detail and some of them can be recorded automatically for several weeks. Slowly, we are beginning to understand how light reaches the circadian system and how the oscillator controls key proteins on the output side and find that the single cell's timing system contains at least two separate circadian oscillators.     

Pinealectomy shortens resynchronisation times of house sparrow (Passer domesticus) circadian rhythms

In many birds periodic melatonin secretion by the pineal organ is essential for the high-amplitude self-sustained output of the circadian pacemaker, and thus for the persistence of rhythmicity in 24 h oscillations controlled by it. The elimination of the pineal melatonin rhythm, or a reduction of its amplitude, renders the circadian pacemaker a less self-sustained, often highly damped, oscillatory system. A reduction in the degree of self-sustainment of a rhythm should not only increase its range of entrainment but also shorten the resynchronization times following phase-shifts of the zeitgeber. This hypothesis has not yet been directly tested. We therefore carried out the present study in which house sparrows (Passer domesticus) were subjected to both 6-h advance and 6-h delay phase-shifts of the light–dark cycle before and after the pinealectomy, and the rhythms in locomotion and feeding were recorded. The results indicate that following the delay, but not the advance, phase shift, resynchronization times were significantly shorter after pinealectomy. The dependence of resynchronization times on the presence or absence of the pineal organ is not only of theoretical interest but might also be of functional significance in the natural life of birds. A reduction or elimination of the amplitude of the melatonin secretion rhythm by the pineal organ might be responsible for faster adjustment to changes in zeitgeber conditions in nature. Professor Dr E. Gwinner died on 07 September 2004.     

四氯乙烯胁迫对草鱼抗氧化酶活性的影响及其机理

研究了四氯乙烯(PCE)对草鱼的肝胰脏、肾脏和鳃组织的超氧化物歧化酶(SOD)和过氧化物酶(POD)的影响.结果表明:草鱼肝胰脏SOD活性,在PCE低浓度胁迫时其SOD活性“先升后降”[72h SOD是(6665.84±106.87)U/g·FW,168h SOD是(3021.26±16.96)U/g·FW],高浓度胁迫时“先降后升再降”[24h SOD是(2175.16±185.14)U/g·FW, 96h SOD是(5692.19±44.17)U/g·FW,168h SOD是(1297.70±11.52)U/g·FW];草鱼肾脏SOD活性在PCE所有浓度组胁迫均是“先降后升再降”的趋势;草鱼鳃组织SOD酶活性只有在PCE较低浓度短时间内没有显著变化,其它情况始终降低.在PCE低浓度和中等浓度胁迫时,草鱼肝胰脏POD活性始终降低,较低浓度和高浓度胁迫时肝胰脏POD活性“先降后升再降”;草鱼肾脏POD活性在PCE低浓度胁迫时“先升后降再升又降”的趋势,而高浓度胁迫时“先降后升又降”;PCE对草鱼鳃组织POD活性“先升后降”的趋势.但是草鱼鳃组织的SOD和POD活性明显低于肝胰脏和肾脏组织的SOD和POD活性.     

Where clocks are redundant: weak circadian mechanisms in reindeer living under polar photic conditions

Biological rhythms are a result of interplay between endogenous clocks and the ambient light–dark (LD) cycle. Biological timing in resident polar organisms presents a conundrum because these experience distinct daily LD cycles for only a few weeks each year. We measured locomotor activity in reindeer, Rangifer tarandus platyrhynchus (SR, n = 5 and 6) and R. tarandus tarandus (NR, n = 6), ranging freely at 78 and 70°N, respectively, continuously throughout 1 year using data loggers. NR, but not SR, are gregarious which enabled us to examine the integrated effects of differences in social organisation and the photic environment at two different latitudes on the organisation of activity. In both sub-species, ultradian bouts of activity and inactivity alternated across the 24-h day throughout the year. This pattern was modified by the LD cycle in NR but barely at all in SR. Periodogram analysis revealed significant ultradian rhythmicity in both sub-species; the frequency of daily cycles of activity increased from three per day in winter to nearly five in summer. We conclude that this increase, and a concomitant increase in the level of daily activity, reflected the seasonal increase in the animals’ appetite and the quality of their forage. Secondly, the combination, most evident in SR, of a weak photic response, weak circadian mechanisms and a weak social synchronization reduces the constraints of biological timing in an environment which is effectively non-rhythmic most of the year and permits expression of the basic ultradian pattern of ruminant activity. Third, the weaker 24-h rhythmicity in SR compared to NR indicates a latitudinal decrease in circadian organization and photic responsiveness in Rangifer.     

Circannuale Rhythmen bei Tieren und ihre photoperiodische Synchronisation

During the last years, evidence has been accumulated indicating that the annual cycles of physiological and behavioral functions in animals are often preprogrammed as endogenous circannual rhythms. Under seasonally constant environmental conditions these rhythms persist for several cycles with periods deviating from year, whereas under natural conditions they are usually synchronized by seasonal changes in the environment, particularly that of photoperiod. Hence, the annual rhythm of photoperiod constitutes a Zeitgeber for the endogenous rhythmicity rather than providing causal stimuli that release particular activities at particular times of the year. On the basis of this new concept several peculiarities of annual biological rhythms under the influence of photoperiodic cycles with different properties can be better understood, at least at a formal level.     

Circadian consequences of social organization in the ant species<Emphasis Type="Italic"> Camponotus compressus</Emphasis>

The locomotor activity rhythm of different castes of the ant species Camponotus compressus was monitored individually under laboratory light/dark (LD) cycles, and under continuous darkness (DD). The colony of this ant species comprises two sexual castes, the queens and the males, and three worker castes, namely the major, media, and minor workers. The virgin males and virgin queens display rhythmic activity patterns, but the mated queens were arrhythmic while laying eggs, with the rhythmicity resuming soon after egg-laying. Under the LD regime, major workers showed nocturnal patterns, while about 75% of the media workers displayed nocturnal patterns and about 25% showed diurnal patterns. Under the DD regime, most major workers exhibited circadian rhythm of activity with a single steady state, whereas media workers displayed two types of activity patterns, with activity patterns changing after 6–9 days in DD (turn-arounds). The pre-turn-around of the ants that showed nocturnal activity patterns during LD entrainment was <24 h after release into DD, which then became >24 h, after 6–9 days. On the other hand, the pre-turn-around of those ants that exhibited diurnal patterns during LD entrainment was first >24 h after release into DD, and then became <24 h, after 6–9 days. The activity of the minor workers neither entrained to LD cycles nor showed any sign of free-run in DD. It appears that the circadian clocks of the ant species C. compressus are flexible, and may perhaps depend upon the tasks assigned to them in the colony.     

Die Sinneszellen der Wirbeltiernetzhaut

Vertebrate visual cells represent a system in an extraordinarily dynamic state. Major parts of the photoreceptors are continually degraded and resynthesized, thus, the cell's morphological and functional integrity is maintained. Some components of visual cell renewal processes follow an endogenous, circadian rhythm driven by an ocular oscillator. Regulative mechanisms of these circadian rhythms may comprise interactions between the neurohormone melatonin and the putative retinal neurotransmitter and neuromodulator dopamine.     

Differences in the behavior characteristics between Daphnia magna and Japanese madaka in an on-line biomonitoring system

It is important to select suitable organisms to adapt the requirement of di erent environment monitoring purposes. Following our previous study, the behavioral responses of Daphnia magna and Japanese madaka (Oryzias latipes) were investigated and compared under flow-through conditions in an on-line biomonitoring system. The results showed that both D. magna and Japanese madaka had similar biological clock, but the circadian rhythms of Japanese madaka was more clearly recorded than that of D. magna. And the sensitivity of D. magna was about two orders of magnitudes higher than that of Japanese madaka in di erent types of toxic chemicals (dichlorovos, deltamethrin and cadmium chloride). However, when both animals were used in an on-line biomonitoring system, the life span of D. magna was less than 7 days and Japanese madaka could last for more than one month without feeding. Therefore, D. magna was proposed to be a more sensitive bioindicator and was suitable for short term monitoring the pollution events at concentration level closing to the water quality standard, while Japanese madaka was more suitable for the long-term monitoring for accidental discharges.     

modifications of ultradian and orcadian rhythms of fetal heart rate after fetal-maternal adrenal gland suppression: A double blind study

In order to verify whether fetal and maternal adrenal gland suppression induces effects on fetal behaviour, triamcinolone was administered to five healthy pregnant women at 35 weeks of gestation. Five patients of the same gestational age were used as control. Fetal heart rate (FHR) and fetal movements were recorded continuously over 2-h interval by means of cardiotocography. After 3 weeks (38 weeks of gestation) the recordings were repeated without drug administration. Cortisol, adrenocorticotropin hormone, 17 β-estradiol and unconjugated estriol were measured at the same time every 2 h in maternal peripheral plasma. At 35 weeks we found a loss of circadian rhythms of the hormones investigated and modifications of ultradian and circadian patterns of FHR in the treated group with respect to the control. No differences in hormonal and biophysical parameters were found between the two groups after the end of treatment (38 weeks). These data suggest that the inhibition of fetal and maternal adrenal glands could cause modifications of FHR patterns.     

Advertent/inadvertent effect on ‘rainfall center’ displacement in Northern Israel

This study of cloud seeding and urbanization effects on the spatial rainfall distribution was carried out in two stages. In the first stage the location of a ‘rainfall center’ (the area with the rainfall maximum) for annual amounts of rainfall was established by applying the Distance Correlation Matrix (DISTCORMAT) technique. Besides ‘natural’ climatic fluctuations there are two other factors which could also cause a shift in the ‘rainfall center’, namely, cloud seeding operations and the inadvertent urban influences. Rainfall centers were computed for the two experimental cloud seeding periods and for a subsequent period of operational seeding.Comparison of the DISTCORMAT outputs revealed that the ‘rainfall centers’ are located, as expected, in the Upper Galilee for the first experimental period and later were displaced westward by 2–4 km. Since in the second random experiment the seeding flight route and target area were shifted eastward, it seems that there is no evidence supporting the cloud seeding rainfall excess determined by various statistical methods. However, it is possible to attribute the center's displacement to the massive urbanization process along the Mediterranean coastal plane.In the second stage only 40 rain stations in the extreme northern part of the country were used and the DISTCORMAT was computed separately for ‘seeded days’ and ‘non-seeded days’. The results indicate that, although the center moved eastward on ‘seeded days’ during the second experiment, it moved westward for the ‘non-seeded days’ sample. Thus the finding offers evidence of both effects: advertent cloud seeding and the inadvertent urbanization factor.     

Nuclear power and post-2012 energy and climate change policies

At present there is no binding agreement (at a global level) to address the risk of anthropogenic climate change after 2012. Disagreements abound with respect to a post-2012 climate change agreement, on issues such as economic development, policy criteria, environmental effectiveness, cost-effectiveness, equity, dynamic flexibility, complementarity, enforceability and so on. One such disagreement is whether or not nuclear power should play a role in a post-2012 climate change agreement. This qualitative analysis explores the conditions under which nuclear power could contribute to addressing climate change in post-2012 architectures. It reveals that – given the right framework conditions – some architectures, like ‘cap and trade’ regimes or ‘policies and measures’ can improve the competitiveness of nuclear power plants, while others are unlikely to provide incentives for nuclear energy development in the short to medium term, such as adaptation and technology cooperation. Overall, the study concludes that post-2012 climate change policy should aim at providing policy flexibility without compromising technology flexibility. For example, the provision of long-term commitment periods has the potential to enable better investments in existing low-carbon technologies but stifle the policy flexibility that political decision makers are often keen to retain so that they can respond more quickly to new scientific evidence or advances in clean technology development.     

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.     

Emissions of perchloroethylene from dry cleaned fabrics

A study was conducted to evaluate the emissions of perchloroethylene (tetrachloroethylene) from dry cleaned fabrics to determine: (a) how the introduction of fresh dry cleaning into a home affects the indoor concentration of perchloroethylene, and (b) the effectiveness of ‘airing out’ dry cleaned clothes in reducing perchloroethylene emissions. Small chamber tests were conducted to determine perchloroethylene emission characteristics for three fabrics at several air exchange rates. Test house studies were conducted to determine the indoor concentration of perchloroethylene due to the placement of dry cleaned clothing in the house. Based on the study results, and assuming that test conditions were representative of normal dry cleaning and consumer practices, the following conclusions were reached.

• (1)Emissions from freshly dry cleaned clothing cause elevated levels of perchloroethylene in residences.
• (2)For the three fabrics tested, ‘airing out’ of dry cleaned clothing by consumers for short time periods (4–8 h) will not be effective in reducing perchloroethylene emissions.
• (3)Adsorptive surfaces (i.e. sinks) in residences may have a major impact on consumer exposure to perchloroethylene.

It is emphasized that these conclusions are based on the results of the study reported. Significant variations in dry cleaning practices and/or in the mix of fabrics and clothing being cleaned could provide different results and conclusions.     

Quantification and control of microbial pollution from agriculture: a new policy challenge?

Faecal indicator organisms (FIOs) are commonly used to quantify pollution of public health significance. Health protection, as indexed by FIO control, is a central aim of new ‘catchment-scale’ water quality management required in the USA by the Clean Water Act and in the European Union (EU) by the Water Framework Directive (WFD). Experience of the former, after a decade of implementation, suggests that the most significant reason for water quality ‘impairment’ is elevated FIO concentrations, mainly in recreational and shellfish harvesting waters. This provides an early warning of possible problems which the EU regulatory authorities are likely to face. To date, however, a surprising lack of EU attention has been given to prediction and control of catchment fluxes of this key parameter. This is likely to prove embarrassing if the experience of the US regulatory community is not acted upon with some urgency. There is a growing, though still partial, body of empirical science to form the ‘evidence-base’ for good regulatory practice. However, adoption of ‘best management practices’ (BMPs) to effect remediation of impacted waters will require close integration of water policy with policies on financial support for the farming community. This is likely to require enhanced communication and integration within the discrete policy communities addressing the agricultural sector through the Common Agricultural Policy and water regulation through the Water Framework Directive.