Circadian clocks are endogenous time keeping mechanisms that are ubiquitous among animals. They enable coordination of many essential biological and metabolic processes in relation to the 24 hour light cycle on earth. However, there are many habitats on earth that are not subject to this light cycle. This study aims to look at the potential genetic drift of the circadian rhythm of a subterranean spider, Meta ovalis, as well as gathering general natural history information on this under-studied spider. This study will fill general gaps in knowledge of this spider and its habitat, highlight the importance of studying organisms within a subterranean environment, and place importance on cave conservation and acquiring knowledge of these specialized, and sensitive species. This study integrates circadian and foraging theory to evaluate species as circadian specialists and generalists based on how narrowly or widely their activity is spread over the 24 h cycle. We suggest that M. ovalis benefits from a generalist strategy, showing small bursts of focused activity widely dispersed across the 24 h cycle, allowing it to capture prey opportunistically whenever it is available. Live spiders were collected from area caves, monitored in an environment controlled for light and temperature, and returned to their cave of origin. The activity of each spider was analyzed for differences in circadian activity among and between populations to determine if there is a significant drift of the circadian strategy between isolated populations of Meta ovalis. We expect to see a different circadian strategy implemented between populations due to drift from the spiders being isolated from other populations.

Circadian systems drive daily oscillations in physiology in organisms from bacteria to humans. These oscillations are coordinated by specific changes in environmental cues, the most important of which is light. In animals, circadian regulation of brain function creates rhythmic patterns in behaviors like sleep. Circadian dysregulation is a common feature of many human diseases and environmental causes of circadian disruption increase susceptibility to many diseases including cancer. Importantly, circadian disruption is also commonly seen in hospitalized patients, which could have negative effects on health outcomes. Understanding the basic biology of circadian-regulatory systems and their physiological functions is essential for identifying the impact of circadian rhythms on human health. This dissertation describes a body of work using the fruit fly Drosophila melanogaster to better understand circadian regulation and its impact on behavior and physiology.

A central question in neuroscience is to identify the roles of genes in behavior. A deeper understanding of genetic influences on behavior would provide insight into the relative impact of innate vs. environmental influences on behavior, as well as improve treatments for neurological diseases. To elucidate the role of genes in behavior, we must not only identify specific genes involved, but also determine the cell types in which they act and the mechanisms by which they exert their influence. In Chapter 2 of this thesis, I found that circadian genes comprising the circadian clock were not necessary in “master clock neurons”, or Pdf+ neurons, for circadian locomotor rhythms. I also identified a small subset of neurons in which disruption of these circadian genes completely abolishes Drosophila circadian behavior. In Chapter 3, I describe the role of a glial gene, ebony, in the regulation of Drosophila courtship and sleep behavior. In addition to identifying the cell types in which ebony acts to regulate these behaviors, I also provide insight into the underlying mechanism of neurotransmitter modulation. The results in this chapter highlight the consideration of non-neuronal cells in the brain when examining the roles of genes in behavior. Together, the results in Chapter 2 and 3 further our understanding of how genes in small populations of cells influence a myriad of conserved Drosophila behaviors.

Most eukaryotic organisms have an internal circadian clock which allows them to maintain their physiological and behavioral cycles in phase with the 24-hour day. The ability to synchronize with (entrain to) the 24-hour day prevents mismatch between the internal circadian clock and the daily cycle which could lead to serious health risks. Some spider species, including Parasteatoda tepidariorum, appear to be exempt from the negative consequences of being out of phase with the 24-hour day. Parasteatoda tepidariorum, the common house spider, is a nocturnal species that consistently demonstrates a short-period circadian clock averaging 21.6 hours when left in constant darkness, yet they are able to entrain to the 24-hour light cycle. Here we test if these spiders are able to use cues (Zeitgebers) other than light to entrain to the 24-hour day. These non-photic Zeitgebers included food, disturbance, and temperature changes. The spiders were assigned into groups which received the given external cues at 24-hour intervals for 7 days followed by 7 days without any external cues. Food, disturbance, and temperature were not found to be effective Zeitgebers for the spiders’ entrainment. There were significant results between random feedings with consistent scheduled feedings which suggests that these spiders were able to manipulate the duration of activity based on the consistency and regularity of a food source. Adjusting the span of activity based on availability of food sources would be advantageous for spiders considering that prey availability in natural environments may not be rhythmic. Given that these spiders tend to build webs in dark secluded spaces, it would be a particular advantage for them to be able to use an environmental cue in addition to light to entrain their internal clocks. However, our data to date suggest otherwise.

Adipose tissue secretes many important biologically active proteins called adipokines. A subset of adipokines, called C1q tumor necrosis factor (TNF) related proteins (CTRPs), play a key role in metabolism, inflammation, and cell signaling. C1q TNF Related Protein 3 (CTRP3) increases hepatic fatty acid oxidation, decreases inflammation, and aids in cardiovascular recovery following a myocardial infarction. However, the mechanisms behind CTRP3’s protective effects on organ systems are unknown. This exploratory study aims to analyze the circulating oligomeric state of CTRP3 and the circadian regulation of CTRP3 to help understand the role of CTRP3 in preventing disease. METHODS: For analysis of the oligomeric state of CTRP3 non-fasting mouse serum was collected from high fat fed hyper-glycemic mice or low fat fed normoglycemic mice and was separated by size exclusion filtration. For analysis of the circadian regulation of CTRP3 serum samples were collected from mice at 4 different time points (2 dark cycle and 2 light cycle) throughout the day and circulating CTRP3 levels were analyzed by immunoblot analysis. RESULTS: In both high fat and low fat fed mice CTRP3 was found to circulate in both >300 kDa oligomers and >100kDa oligomers, with no detectable amount of CTRP3 less 100 kDa. Interestingly, although there was no difference in the total amount of CTRP3 between the high fat and low fat fed mice there was a higher abundance of CTRP3 >300 kDa in the high fat fed and a greater abundance of CTRP3 found 100-300 kDa. Additionally, we found that serum CTRP3 levels vary greatly throughout a 24-hour time-period within each mouse, but no consensus circadian pattern was observed. CONCLUSION: In vitro mammalian produced recombinant CTRP3 protein was found to exist as trimer, hexamer, and high molecule weight. This is the first study to indicate that CTRP3 circulates in different oligomeric states in vivo, and this is also the first study to observe a difference in the oligomeric state of CTRP3 related to metabolic state. Combined these findings indicate that oligomeric state of CTRP3 may be more metabolically relevant than total amount of circulating CTRP3. In addition, our finding of a high variability of CTRP3 within the same mouse at different times throughout the day indicates that is not regulated by circadian rhythms but is susceptible to variability due to some unknown regulatory factor. These findings have identified novel unknown aspects of CTRP3, which require further research to understand the role of CTRP3 in human health and disease.

No description available.

In the field of insect circadian rhythms, the honey bee is best known for its foraging time-sense, or Zeitgedächtnis, which permits the forager bee to make precise associations between the presence of food and the time of day. A number of studies, now considered classics, established that bees could be trained to collect food at virtually any time of the circadian cycle and that this timekeeping ability was controlled by an endogenous circadian clock. Recently, behavioral rhythms in bees have been examined using a variety of approaches, in both laboratory and field studies. The following areas of new research are reviewed: (a) the ontogeny of behavioral rhythmicity in newly emerged worker bees; (b) the integration of behavioral rhythmicity with the colony's division of labor; (c) the evidence for social entrainment of behavioral rhythms and for a 'clock of the colony'; (d) the potential linkage between circadian rhythms of general locomotor activity and the foraging time-sense; (e) learning and entrainment hypotheses proposed to explain the mechanism underlying the time-sense; (f) the interplay between extinction and persistence of the time-memory as revealed from the differential behavior of individuals within the foraging group; and (g) comparisons of the Zeitgedächtnis with food-anticipatory rhythms in other animals.

Circadian clocks are endogenous timekeeping mechanisms, which give the sense of time-of-day to most organisms. To help the organisms to adapt to daily fluctuations in the environment, circadian clocks are reset by various environmental cues. Light is one of the cardinal environmental cues that synchronize circadian clocks. In a standard 12:12 light-dark condition, Drosophila exhibits bimodal activity pattern in the anticipation of lights-on and -off. The morning peak of activity is generated by Pigment Dispersing Factor (PDF) positive small ventro-lateral neurons (sLNvs) called the M-oscillators, while the evening peak of activity is generated by the dorsolateral neurons (LNds) and the 5th sLNv together referred to as the E-oscillators. Since the Drosophila circadian clock is extremely sensitive to light, a brief light exposure can robustly shift the phase of circadian behavior. The model for this resetting posits that circadian photoreception is cell-autonomous: the photoreceptor CRYPTOCHROME (CRY) senses light, binds to TIMELESS (TIM) and promotes its degradation via JETLAG (JET). However, it was more recently proposed that interactions between circadian neurons are also required for phase resetting. The goal of my thesis was to map the neuronal circuitry controlling circadian photoreception in Drosophila. In the first half of my dissertation (Chapter II), using a novel severe jetset mutant and JET RNAi, we identified M- and E-oscillators as critical light sensing neurons. We also found that JET functions cell-autonomously to promote TIM degradation in M- and E-oscillators, and non-autonomously in E-oscillators when expressed in M-oscillators. However, JET expression was required in both groups of neurons to phase-shift locomotor rhythms in response to light input. Thus M- and E-oscillators cooperate to shift circadian behavior in response to photic cues. In chapter III, unexpectedly, we found that light can delay or advance circadian behavior even when the M- or E-oscillators are genetically ablated or incapacitated suggesting that behavioral phase shifts in response to light are largely a consequence of cell autonomous light detection by CRY and governed by the molecular properties of the pacemaker. Nevertheless, neural interactions are integral in modulating light responses. The M-oscillator neurotransmitter, PDF was important in coordinating M- and E-oscillators for circadian behavioral response to light input. Moreover, we uncover a potential role for a subset of Dorsal neurons in control of phase advances specifically. Hence, neural modulation of cell autonomous light detection contributes to plasticity of circadian behavior and facilitates its adaptation to environmental inputs.

The present study examined whether and to what extent physiological rhythms of long-term . night workers become adapted to their unconventionally scheduled hours of work and sleep and how the degree of adaptation would be reflected in ratings of sleep quality, mood, anxiety, energy and satisfaction.

No description available.