O tecido adiposo, através da leptina, desempenha um papel permissivo sobre a maturação sexual do indivíduo. Apesar da importância do tecido adiposo para a puberdade, pouco se sabe a respeito do processo de formação deste tecido neste período da vida. Estudos em humanos têm descrito a presença de resistência à insulina puberal. Assim, frente à importância do tecido adiposo para a puberdade, o objetivo do trabalho foi investigar a resposta do tecido adiposo à insulina no período puberal. Foram utilizados os coxins adiposos subcutâneo e periepididimal. Na puberdade, paralelamente à intolerância à glicose transitória que ocorreu nas semanas iniciais, e, portanto, prejuízo da utilização da glicose pelos tecidos insulino-dependentes, o tecido adiposo (SC e PE) teve sua responsividade normal à insulina e uma melhor capacidade de incorporação de glicose em lipídeos o que leva a crer que há um desvio da utilização deste substrato energético, a glicose, para a formação do tecido adiposo. / The adipose tissue is critical to puberty. Leptin exerts a permissive role to hypothalamic-hypophysial-gonadal maturation and, thereby, adipose tissue is necessary to pubertal development. Despite its importance to puberty, little is known about the process of adipose tissue formation during this period of life. Researches have described insulin resistance at pubertal period in humans. The adipose tissue importance to puberty added to pubertal insulin resistance described in humans lead us to investigate how the adipose tissue responds to insulin at this period since it is essential at this time. We assessed two distinct fat pads: the subcutaneous fat pad and the epididymal one. At the puberty, despite the temporary glucose intolerance and the constraint for glucose utilization by insulin-dependent tissues, the adipose tissue had normal insulin responsiveness plus an improved capacity to synthesize lipids from glucose which led us to hypothesize that glucose could have been deviated towards the adipose tissue.

A glândula pineal de mamíferos não é uma estrutura oscilatória autônoma, exigindo a liberação de noradrenalina (Nor) na fase escura para que a melatonina seja circadianamente produzida. Na cultura padrão de glândula pineal, o órgão não expressa ritmicidade funcional e para mimetizar o padrão fisiológico de liberação de Nor, desenvolvemos a cultura temporizada com Nor. Logo, o objetivo desse trabalho foi investigar a manutenção do ritmo de expressão dos genes relógio pela cultura temporizada, e qual a via noradrenérgica envolvida. Para os estudos in vitro, realizaram-se culturas dos grupos: controle (sem Nor), agudo (cultura padrão) e temporizado (12h com Nor/12h sem Nor). Além disso, à cultura temporizada se adicionou Prasozin e/ou Propranolol. Analisou-se expressão dos genes relógio, atividade da enzima AANAT e conteúdo de melatonina no meio de cultura. No grupo temporizado, observou-se a manutenção da ritmicidade dos genes analisados, diferente do observado nos grupos controle, agudo e temporizado tratado com bloqueadores, além do aumento da atividade enzimática da AANAT e aumento do conteúdo de melatonina. Em suma, a cultura temporizada com Nor se mostra importante para evitar a arritmicidade encontrada na cultura padrão de glândula pineal. / The mammals pineal gland is not an autonomous oscillator, the circadian melatonin synthesis requires the release of norepinephrine (NE) on the dark phase. In standard pineal gland culture, the glands do not express any functional rhythmicity. To mimic the physiological pattern of NE release in the pineal gland culture, we developed a synchronized culture with NE. We aimed to investigate the maintenance of circadian clock genes expression within rat pineal gland under acute and synchronized culture and the noradrenergic pathway involved. In in vitro experiments, culture glands were under: control (without NE), acute (standard culture) and synchronized (12h with NE/12h without NE) conditions. Furthermore, in the synchronized group were added Prasozin and/or Propranolol. We investigated clock genes expression, AANAT activity and melatonin content. The synchronized culture was able to maintain the rhythmic clock genes expression, which didn´t occur in control, acute and synchronized treated with blockers groups, and was able to improve AANAT activity and melatonin synthesis. In conclusion, synchronized culture method showed as a useful approach to avoid disruption of rhythmic variations found in the standard culture.

Tanto as evidências experimentais que demonstraram a geração endógena de ritmos com períodos circadianos, quanto as investigações sobre os diferentes mecanismos de sincronização dos ritmos circadianos aos marcadores temporais externos de períodos fixos de 24h forneceram material para a elaboração de proposições importantes sobre as características do sistema de temporização biológica circadiana. Dentro desse cenário, foi de muita ajuda a aplicação da modelagem matemática. O desenvolvimento desses modelos permitiu a investigação de conjecturas que tentam explicar as características subjacentes aos mecanismos que coordenam esse sistema. Nosso objetivo, neste trabalho, foi de explorar a hipótese de que o mecanismo de controle da ritmicidade circadiana é exercido pela ação de laços de retroalimentação negativa acionados após tempos de retardo característicos do sistema. Para alcançarmos esse objetivo, elaboramos um modelo no qual o controle e a manutenção da expressão rítmica circadiana fossem conseqüentes da ação de dois laços de retroalimentação negativa com tempos de retardo distintos. Adicionalmente, avaliamos a resposta do modelo à ação de oscilações externas. Por meio da dinâmica não-linear resultante do modelo, nós observamos sugestiva similaridade entre as respostas obtidas nas simulações e as descrições experimentais da expressão do sistema de temporização circadiana citadas na literatura. Esses resultados deram suporte a hipótese inicial como explicação do funcionamento do sistema. / Both the experimental evidences of generation of biological circadian rhythms and the results of investigation about the mechanisms of synchronization between the circadian rhythms with the external cycles of 24-hour period provided material for the development of important assumptions about the characteristics of the circadian timing system. Inside this scenery, it was helpful the application of mathematical models. The development of these models permited the inquiry of some hypotheses which try to explain the underlying characteristics of this system. Our aim, in this work, was to investigate the hypothesis that explain the controlling mechanism of the circadian system as a result of the action of negative feedback loops triggered after charateristic time delays. For reaching this goal, our porpouse was to build a mathematical model which simulated circadian rhythmic expressions controlled by two feedback loops with different time delays. Additionaly, we also simulated the response of the model under external oscillations. Through the non-linear dynamic resulting from the model we observed suggestive similarity between the simulations and the experimental descriptions of the circadian system expressions present in many works. These results gave support to the validation of the initial hypothesis.

A Cronobiologia estuda a origem e a manifestação de ritmos biológicos nos mais diversos táxons. A análise dos dados obtidos experimentalmente, contudo, é bastante complexa, haja vista a restrita gama de métodos disponíveis para tal. Os osciladores que determinam a existência dos ritmos biológicos são exemplos de sistemas dinâmicos não-lineares, os quais estão amplamente distribuídos nos seres vivos. Esses sistemas, por suas peculiaridades, são melhor analisados por métodos não-lineares. O objetivo deste trabalho é testar diferentes métodos de análise séries temporais, tanto alguns classicamente empregados na Cronobiologia quanto métodos não-lineares, verificando sua empregabilidade e funcionalidade para dados cronobiológicos, bem como as propriedades que permitem ou não seu uso. Para tanto, foram utilizados dados de ritmos de consumo de O2 obtidos para diferentes grupos etários de operárias de Melipona quadrifasciata (Hymenoptera, Meliponini). Tais dados foram submetidos às seguintes análises: Transformada Rápida de Fourier (TRF), Análise de Potência Espectral (PSA), Estatística Circular (teste de Rayleigh), Teste de Estacionariedade (Teste da Raiz Unitária de Dickey-Fuller Aumentado - ADF), Plot de Poincaré, Entropia Aproximada (ApEn) e Entropia Aproximada Volumétrica (vApEn). Os resultados obtidos demonstram que os métodos não-lineares de análise detectam a existência de ritmo metabólico, assim como os métodos lineares utilizados por Teixeira (2006) e Camargo (em andamento) indicam sua presença. Ressalta-se, contudo, que há certa dificuldade em distinguir se a variabilidade existente nas séries deve-se, possivelmente, a seu comportamento determinístico ou a ruídos externos a elas, cuja detecção não é possível. Outro importante fator limitante da aplicabilidade das análises não-lineares é o número de pontos das séries temporais em questão, que era bastante reduzido nesse estudo. Dessa maneira, conclui-se que alguns métodos não-lineares, e.g. TRF, também são eficazes na detecção de ritmos biológicos, devendo ser observada a restrição devido ao tamanho da série temporal. / Chronobiology is the study of the origin and manifestation of rhythmical phenomena in all sorts of taxons. The analysis of the experimental obtained data is, however, still very complex due to the lack of availability of methods and techniques. The oscillators that determine the existence of rhythmical biological phenomena are examples of non-linear dynamic systems, which are widely spread among organisms. This research intends to present the result of a sort of temporal series analysis methods, some already used for Chronobiology research, as non-linear methods, testing their use and functionality for chronobiological data as well as determining their gaps and limitations for this purpose. For this research, data regarding to rhythm of O2 consumption were obtained from different age groups of Melipona quadrifasciata (Hymenoptera, Meliponini) workers. Such data were submitted to the following analysis: Fast Fourier Transform (FFT), Power Spectrum Analysis (PSA), Circular Statistics (Rayleigh\'s test), Stationarity Test (Unit Root Augmented Dickey-Fuller Test - ADF), Poincaré Plot, Approximate Entropy (ApEn) e Volumetric Approximate Entropy (vApEn). The results indicate that nonlinear methods detect the presence of metabolic rhythm, such as previous researches where linear methods used by Teixeira (2006) and Camargo (ongoing research) indicate its presence. However, there is some difficulty in determining if the variability present in the series is possibly due to its deterministic behavior or to the external noise, from which the determination is still not possible. Another limiting factor is the number of points of analyzed temporal series, which was very small. We conclude that some nonlinear methods, e.g. FFT, are effective to detect biological rhythms, but the constraint to time series length must be observed.

Les efflorescences de la micro-algue toxique Alexandrium minutum sont en constante augmentation au niveau mondial, accentuées par les apports anthropiques et le réchauffement global, et posent des problèmes écologiques, économiques et sanitaires. Lors d’une exposition à A. minutum, l’accumulation des phycotoxines paralysantes (PSP) dans les tissus semble être différente entre les huîtres diploïdes et triploïdes. Par ailleurs, de nombreuses fonctions physiologiques de l’huître C. gigas sont impactées. L’ensemble des fonctions physiologiques d’un organisme est régulé par des rythmes biologiques. Propriété fondamentale de la vie, les rythmes biologiques permettent aux organismes de se synchroniser et d’anticiper les variations cycliques de l’environnement. Dans mes travaux, je me suis intéressée aux rythmes biologiques des huîtres diploïdes et triploïdes C. gigas et à leurs interactions avec la contamination par les PSP. Une analyse in situ sur un an a mis en évidence une relation jusque-là inconnue entre le comportement valvaire de C. gigas et le cycle d’éclairement de la lune, ainsi qu’une relation fine et subtile des cycles comportementaux nycthéméraux et tidaux avec l’évolution annuelle de la photopériode. Cette relation est modulée par la ploïdie. Par ailleurs, la mise au point d’une approche non-invasive d’interférence par ARN a permis de mettre en évidence l’implication de l’horloge circadienne dans les processus de bioaccumulation des PSP chez C. gigas. Enfin, l’analyse du transcriptome cyclique dans les branchies de C. gigas a mis en évidence qu’au moins 42 % du transcriptome peut être exprimé de façon oscillante. Contre intuitivement, en condition d’alternance jour / nuit, une majorité de transcrits sont ultradiens, trois fois plus nombreux que les transcrits circadiens. Exposées à A. minutum, les huîtres ont montré un remodelage profond de leur transcriptome cyclique, pouvant entraîner la perte de synchronisation de l’huître avec son environnement. / Harmful algal blooms of Alexandrium minutum are constantly increasing at the global level, accentuated by anthropogenic contributions and global warming, causing ecological, economical and sanitary problems. During exposition to A. minutum, paralytic phycotoxins (PSP) accumulation differs between diploid and triploid oysters. Moreover, many physiological functions of the oyster C. gigas are impacted. All physiological functions of an organism are regulated by biological rhythms. As a fundamental property of life, biological rhythms allow organisms to synchronize and anticipate cyclic variations of the environment. In my work, I was interested in the biological rhythms of diploid and triploid oysters C. gigas, and their interactions with PSP contamination. A one-year in situ analysis revealed a previously unknown relationship between valve behavior of C. gigas and the lunar illumination cycle, as well as a fine and subtle relationship of the nycthemeral and tidal behavioral cycles with the annual evolution of the photoperiod. This relationship was modulated by the ploidy. Moreover, the development of a non-invasive approach of RNA interference revealed the involvement of the circadian clock in bioaccumulation processes of PSPs in C. gigas. Finally, analysis of the cyclic transcriptome in the gills of C. gigas showed that at least 42 % of the transcriptome can oscillate. Surprisingly, in day / night entrainment, most of transcripts were ultradians, three times more abundant than circadian transcripts. Exposed to A. minutum, results showed a profound remodeling of the cyclic transcriptome of C. gigas, which could lead to loss of synchronization of the oyster with its environment.

Orientador: Cristiano de Mello Gallep / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-22T03:28:54Z (GMT). No. of bitstreams: 1 Moraes_ThiagoAlexandre_M.pdf: 12211625 bytes, checksum: 5e27e2aac5dfc12de0ee782b7b6a33bc (MD5) Previous issue date: 2013 / Resumo: A emissão fotônica ultrafraca proveniente de plântulas de trigo foi mensurada em várias séries de testes sob condições constantes, no interior de câmara escura. Grãos brasileiros também foram transportados e testados na Alemanha, em séries simultâneas realizadas paralelamente a séries conduzidas tanto no Brasil quanto na Alemanha. As plântulas em ambos os países apresentaram ritmos semicircadianos, coincidentes e em sincronia com os ritmos da variação da aceleração gravimétrica local, produzidos pelos movimentos lunissolares. São apresentadas análises matemáticas a respeito destas sincronias e coincidências. Em mais de 80% do período de testes considerados o coeficiente local de correlação de Pearson entre os dois parâmetros revelou relação significante (P>0,7). Com o uso da transformada rápida de Fourier foram evidenciadas as similaridades entre as componentes temporais de oscilação do parâmetro fotônico e as encontradas no parâmetro gravimétrico. As fases da lua e a época do ano possivelmente produzem influências relevantes no desenvolvimento das plântulas. Os resultados encontrados sustentam a hipótese de que os processos envolvidos com a emissão fotônica em plântulas de trigo sejam regulados pelos ritmos de variação gravimétrica, produzidos pelos movimentos lunissolares. A técnica de detecção de emissão fotônica espontânea se mostrou uma ferramenta inovadora e útil para estudos biofísicos e cronobiológicos / Abstract: The ultra-weak photon emission from wheat seedling was measured in several series of tests under constant conditions inside a dark chamber. Brazilian seeds were also transported and tested in Germany, with simultaneous series conducted both in Brazil and in Germany. The seedlings showed, in both countries, semi-circadian rhythms coincident and in synchrony with the rhythms of local gravimetric variations of acceleration produced by lunisolar movements. Mathematical analysis of these synchronies and coincidences are presented. The local Pearson correlation coefficient between the two parameters showed a significant relationship (P> 0.7) in more than 80% of the considered testing period. The rhythmic similarities between the biophotonic oscillation and the gravimetric parameter were done by fast Fourier transform. The phases of the moon and the time of year possibly produce relevant influences on development of seedlings. The results support the hypothesis that processes involved with biophoton emission in wheat seedlings may be regulated by variations on the gravimetric rhythms in accordance to lunisolar movements. Further studies are desirable in order to look for the physiological origin of this phenomenon. The spontaneous ultra-weak photon emission detection technique proved to be a new and useful tool for chrono-biological and biophysical studies / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

Objetivo: Identificar, através de revisão sistemática, o efeito de perturbações da ritmicidade circadiana sobre a saúde humana e, através de experimento animal, o efeito sobre a vulnerabilidade a eventos estressantes. Métodos: Estudo 1: Foi conduzida uma revisão sistemática da literatura nas bases de dados eletrônicas PubMed, Scopus, Embase e LILACS utilizando os termos “social AND (jet lag OR jetlag)”. A busca foi finalizada em 22 de agosto de 2016, resultando em 26 artigos incluídos na revisão. Estudo 2: Camundongos Balb/c foram submetidos a um protocolo de estresse crônico moderado (CMS), sozinho ou precedido de 4 ciclos claro-escuro de período encurtado (10h claro, 10h escuro), e foram comparados a animais submetidos apenas ao encurtamento do ciclo claro-escuro ou a nenhuma intervenção. Em um primeiro experimento, os animais dos grupos estressados foram submetidos a 3 semanas de CMS e foram avaliados parâmetros dos ritmos de atividade-repouso e temperatura central e o ganho de peso corporal. Em um segundo experimento, o período de CMS foi reduzido para 2 semanas e foram analisados parâmetros metabólicos séricos, teste de preferência por solução de sacarose (para aferir comportamento tipo-depressivo) e teste claro-escuro (para aferir comportamento tipo-ansioso). Resultados: Estudo 1: Os desfechos de saúde e comportamento associados ao jetlag social são diversos (epilepsia, sintomas psiquiátricos menores, agressão e problemas de conduta, transtornos de humor, prejuízo cognitivo, uso de substâncias, risco cardiometabólico e perfil endócrino adverso), mas há grande variabilidade de metodologias e populações e grande risco de viés dos estudos analisados. Estudo 2: A exposição ao CMS precedida de ciclos claro-escuro encurtados resultou em aumento na amplitude do ritmo de temperatura, mantido mesmo após o término do protocolo de estresse, e redução do peso corporal no período do CMS, havendo uma clara associação entre estes desfechos. Não foram observadas alterações significativas no comportamento, possivelmente devido a problemas metodológicos, nem nos parâmetros metabólicos avaliados. Conclusões: Este trabalho contribui para o conhecimento sobre o papel da cronorruptura na vulnerabilidade ao desenvolvimento de patologias através de revisão das evidências associadas a um modelo de cronorruptura em humanos (jetlag social) e de demonstração de evidências em um modelo animal (encurtamento do ciclo claro-escuro). As evidências relacionadas ao jetlag social devem ser avaliadas com cautela devido à heterogeneidade metodológica e alto risco de viés, sendo necessários estudos longitudinais e com metodologia padronizada para estabelecer associações mais confiáveis. Em animais, a vulnerabilidade ao estresse parece ser aumentada pelo encurtamento do ciclo claro-escuro no que se refere a ritmos circadianos e metabolismo, mas resta determinar o efeito sobre comportamentos tipo-depressivo e tipo-ansioso. Apoio: FIPE/HCPA, CNPq e CAPES. / Objective: Identify through a systematic review the effect of circadian disturbances on human health and, through animal experimentation, the effect on vulnerability to stress. Methods: Study 1: A systematic review of the literature was conducted on PubMed, Scopus, Embase and LILACS electronic databases using the terms "social AND (jet lag OR jetlag)". The search was finalized on August 22, 2016, resulting in 26 research articles included in the review. Study 2: Balb/c mice were exposed to a chronic mild stress (CMS) protocol alone or preceded by 4 shortened light-dark cycles (10h light, 10h dark) and compared to animals exposed only to the shortened light-dark cycles or to no intervention. In one experiment, animals of stressed groups were exposed to 3 weeks of CMS for evaluation of rest-activity and core body temperature rhythms and body weight gain. In a second experiment, CMS was shortened to 2 weeks and serum metabolic parameters, sucrose preference test (to assess depressive-like behavior) and black and white test (to assess anxiety-like behavior) were evaluated. Results: Study 1: The health and behavioral outcomes associated to social jetlag are diverse (epilepsy, minor psychiatric symptoms, aggression and conduct problems, mood disorders, cognitive impairment, substance use, cardiometabolic risk and adverse endocrine profile), but there is great variation of methodologies and populations as well as high risk of bias in analyzed studies. Study 2: Exposure to CMS preceded by shortened light-dark cycles resulted in increased amplitude of core body temperature rhythm, sustained even after the end of CMS, and reduced body weight during CMS, with a clear association between these two outcomes. No significant alterations were observed either in behavior, likely due to methodological issues, or metabolic parameters assessed. Conclusions: This work contributes to the knowledge on the role of chronodisruption on the vulnerability to development of pathologies through a review of evidences associated with a model of chronodisruption in humans (social jetlag) and demonstration of evidences from an animal model of chonodisruption (shortened light-dark cycles). The evidence regarding social jetlag must be analyzed with caution due to methodological heterogeneity and high risk of bias of articles reviewed and longitudinal studies with standardized methodology are needed to establish reliable associations. In animals, it seems that vulnerability to stress is increased by the light-dark cycle shortening in what refers to circadian rhythms and metabolism, but the effect on depressive-like and anxiety-like behaviors remains to be determined. Financial support: FIPE/HCPA, CNPq and CAPES.

An organism’s circadian clock exists as a self-regulating oscillator that can synchronize with its surroundings. This manifests as physiological and behavioral output which can anticipate changes in environment. These rhythms may even persist internally and are known to oscillate at a period (tau) of around 24 hours even in the absence of external cues. In the laboratory, such rhythmic output is known as a free-running period (FRP). Given that circadian rhythms are distributed in a number of taxa as well as their tendency to oscillate along with the solar day, it has been suggested that they result from natural selection. The argument that tone’s clock is adaptive is based on how it is advantageous: the clock instills temporal order among physiological processes as well as enabling one to anticipate external cues. Losing that order in one’s clock has also been associated with a number of metabolic and neurological pathologies. Along with adaptive significance, it has been surmised that an internal clock which synchronizes with one’s surrounding environment is beneficial to an individual. An organism whose free-running period closest matches the rhythmic output of its external environment will exhibit a higher relative fitness as compared to those whose periods deviate from 24 hours. This forms the basis of the ‘circadian resonance hypothesis’. Circadian resonance has been examined in a number of species, from Cyanobacteria to mammals. Collectively, experimental results have supported the rationale that an individual does best when its internal clock resonates with the 24 hour day. The bowl and doily spider, Frontinella communis, not only has its own endogenous rhythm (free-running period), it exhibits an average free-running period of 28.26 hours, deviating from a usual period of ~24 hours. Keeping in mind the circadian resonance hypothesis, an internal clock with such an extreme deviation from the 24 hour day should prove detrimental to one’s overall health. Despite this, Frontinella communis not only has a long clock; among the species, their clocks also appear to be highly variable, FRPs ranging from ~24 to ~33 hours. This study monitored locomotor activity of Frontinella communis to examine whether its free-running period, on average, remained the same throughout its active season (May-September). It was found that average free-running period in F. communis varied significantly over a five-month period. Average FRP appears to peak in June followed by a steady, linear decline as the season continues. A variety of organisms have been shown to exhibit seasonal responses that allow them to cope with environmental change. It is not known whether the change in Frontinella’s FRP is such an advantage or is merely coincidental. Any free running period detected under the alpha level of 0.05 was not ruled significant. Along with the rise and fall of average FRPs, the presence of FRP deemed significant was found to decline as the season ended- 42% of individuals (n= 19) reported as arrhythmic. While age has been found to correlate with circadian desynchrony in other taxa (rats, humans), an association in Frontinella remains to be tested.

Circadian rhythms are ubiquitous among eukaryotic organisms and have evolved several times independently which strongly suggests that the presence of a biological clock is adaptive. A prevailing, though relatively untested, hypothesis is that having an internal clock allows organisms to anticipate daily changes in the environment and physiologically and/or behaviorally prepare for them. Locomotor activity is commonly interpreted as an indicator of neurological arousal, and, thus, is a useful indicator in studies of circadian rhythm. We have observed that some species of spiders exhibit a tight and predictable band of activity at a particular time of day, while in other species activity is more spread out through the day. Such patterns tend to continue, or are exaggerated, under conditions of constant darkness. We hypothesize that these predators with tight activity bands are ‘circadian specialists’ using their internal clocks to focus their attention in the narrow temporal window when prey are available to them. On the other hand, the species with broader activity bands are employing a ‘circadian generalist’ strategy, and are able to be more opportunistic with temporally unpredictable prey. Some support of this hypothesis comes from the observation that species that forage only at night tend to have tighter bands of locomotor activity than those species which forage continuously day and night. In this study we present a simulation model that supports this idea that a tight distribution of neurological alertness is advantageous when prey is predictable, but an evenly clumped distribution of alertness is favored when prey are unpredictable. We also tested the abilities of four nocturnal spider species to opportunistically respond to an unexpected period of darkness. Consistent with our hypothesis, we found that in the predicted circadian specialist species activity could not be elicited with unexpected darkness at any time of day, while the predicted circadian generalist showed activity in mid and late day. In two species intermediate on the specialist-generalist scale we only elicited activity in late day. This work represents a test of a novel hypothesis regarding the adaptiveness of circadian rhythms.

Circadian clocks enable coordination of essential biological and metabolic processes in relation to the 24-hour light cycle. However, there are many habitats that are not subject to this light cycle, such as the deep sea, arctic regions, and cave systems. This study analyzes the circadian pattern of isolated populations of a subterranean spider, Meta ovalis from two Tennessee caves and five Indiana caves. Locomotor activity was recorded with TriKinetics LAM50 Locomotor Activity Monitor under a 12-hour light (L), 12-hour dark (D) (LD 12:12) cycle preceding total darkness (DD). Significant differences were found within and among populations found in Tennessee cave systems in average free running period and onset of locomotor activity. Selection, drift, and genetic fixation are explored as the causes of variation in the present study, using M. ovalis as the model organism. All five caves in Indiana show little variation, whereas both Tennessee caves show large interindividual variation.