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Activity Rhythm (activity + rhythm)

Distribution by Scientific Domains

Life Sciences	51%
Medical Sciences	37%

Kinds of Activity Rhythm

circadian activity rhythm

Selected Abstracts

Developmental Alcohol Exposure Alters Light-Induced Phase Shifts of the Circadian Activity Rhythm in Rats

ALCOHOLISM, Issue 7 2004
Yuhua Z. Farnell
Background: Developmental alcohol (EtOH) exposure produces long-term changes in the photic regulation of rat circadian behavior. Because entrainment of circadian rhythms to 24-hr light/dark cycles is mediated by phase shifting or resetting the clock mechanism, we examined whether developmental EtOH exposure also alters the phase-shifting effects of light pulses on the rat activity rhythm. Methods: Artificially reared Sprague-Dawley rat pups were exposed to EtOH (4.5 g/kg/day) or an isocaloric milk formula (gastrostomy control; GC) on postnatal days 4 to 9. At 2 months of age, rats from the EtOH, GC, and suckle control groups were housed individually, and wheel-running behavior was continuously recorded first in a 12-hr light/12-hr dark photoperiod for 10 to 14 days and thereafter in constant darkness (DD). Once the activity rhythm was observed to stably free-run in DD for at least 14 days, animals were exposed to a 15-min light pulse at either 2 or 10 hr after the onset of activity [i.e., circadian time (CT) 14 or 22, respectively], because light exposure at these times induces maximal phase delays or advances of the rat activity rhythm. Results: EtOH-treated rats were distinguished by robust increases in their phase-shifting responses to light. In the suckle control and GC groups, light pulses shifted the activity rhythm as expected, inducing phase delays of approximately 2 hr at CT 14 and advances of similar amplitude at CT 22. In contrast, the same light stimulus produced phase delays at CT 14 and advances at CT 22 of longer than 3 hr in EtOH-treated rats. The mean phase delay at CT 14 and advance at CT 22 in EtOH rats were significantly greater (p < 0.05) than the light-induced shifts observed in control animals. Conclusions: The data indicate that developmental EtOH exposure alters the phase-shifting responses of the rat activity rhythm to light. This finding, coupled with changes in the circadian period and light/dark entrainment observed in EtOH-treated rats, suggests that developmental EtOH exposure may permanently alter the clock mechanism in the suprachiasmatic nucleus and its regulation of circadian behavior. [source]

Circadian Activity Rhythms and Mortality: The Study of Osteoporotic Fractures

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 2 2010
Gregory J. Tranah PhD
OBJECTIVES: To determine whether circadian activity rhythms are associated with mortality in community-dwelling older women. DESIGN: Prospective study of mortality. SETTING: A cohort study of health and aging. PARTICIPANTS: Three thousand twenty-seven community-dwelling women from the Study of Osteoporotic Fractures cohort (mean age 84). MEASUREMENTS: Activity data were collected using wrist actigraphy for a minimum of three 24-hour periods, and circadian activity rhythms were computed. Parameters of interest included height of activity peak (amplitude), midline estimating statistic of rhythm (mesor), strength of activity rhythm (robustness), and time of peak activity (acrophase). Vital status, with cause of death adjudicated through death certificates, was prospectively ascertained. RESULTS: Over an average of 4.1 years of follow-up, there were 444 (14.7%) deaths. There was an inverse association between peak activity height and all-cause mortality rates, with higher mortality rates observed in the lowest activity quartile (hazard ratio (HR)=2.18, 95% confidence interval (CI)=1.63,2.92) than in the highest quartile after adjusting for age, clinic site, race, body mass index, cognitive function, exercise, instrumental activity of daily living impairments, depression, medications, alcohol, smoking, self-reported health status, married status, and comorbidities. A greater risk of mortality from all causes was observed for those in the lowest quartiles of mesor (HR=1.71, 95% CI=1.29,2.27) and rhythm robustness (HR=1.97, 95% CI=1.50,2.60) than for those in the highest quartiles. Greater mortality from cancer (HR=2.09, 95% CI=1.04,4.22) and stroke (HR=2.64, 95% CI=1.11,6.30) was observed for later peak activity (after 4:33 p.m.; >1.5 SD from mean) than for the mean peak range (2:50,4:33 p.m.). CONCLUSION: Older women with weak circadian activity rhythms have higher mortality risk. If confirmed in other cohorts, studies will be needed to test whether interventions (e.g., physical activity, bright light exposure) that regulate circadian activity rhythms will improve health outcomes in older adults. [source]

The mouse VPAC2 receptor confers suprachiasmatic nuclei cellular rhythmicity and responsiveness to vasoactive intestinal polypeptide in vitro

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2003
David J. Cutler
Abstract Expression of coherent and rhythmic circadian (, 24 h) variation of behaviour, metabolism and other physiological processes in mammals is governed by a dominant biological clock located in the hypothalamic suprachiasmatic nuclei (SCN). Photic entrainment of the SCN circadian clock is mediated, in part, by vasoactive intestinal polypeptide (VIP) acting through the VPAC2 receptor. Here we used mice lacking the VPAC2 receptor (Vipr2,/,) to examine the contribution of this receptor to the electrophysiological actions of VIP on SCN neurons, and to the generation of SCN electrical firing rate rhythms SCN in vitro. Compared with wild-type controls, fewer SCN cells from Vipr2,/, mice responded to VIP and the VPAC2 receptor-selective agonist Ro 25-1553. By contrast, similar proportions of Vipr2,/, and wild-type SCN cells responded to gastrin-releasing peptide, arginine vasopressin or N -methyl- d -aspartate. Moreover, VIP-evoked responses from control SCN neurons were attenuated by the selective VPAC2 receptor antagonist PG 99-465. In firing rate rhythm experiments, the midday peak in activity observed in control SCN cells was lost in Vipr2,/, mice. The loss of electrical activity rhythm in Vipr2,/, mice was mimicked in control SCN slices by chronic treatment with PG 99-465. These results demonstrate that the VPAC2 receptor is necessary for the major part of the electrophysiological actions of VIP on SCN cells in vitro, and is of fundamental importance for the rhythmic and coherent expression of circadian rhythms governed by the SCN clock. These findings suggest a novel role of VPAC2 receptor signalling, and of cell-to-cell communication in general, in the maintenance of core clock function in mammals, impacting on the cellular physiology of SCN neurons. [source]

A ,polarisation sun-dial' dictates the optimal time of day for dispersal by flying aquatic insects

FRESHWATER BIOLOGY, Issue 7 2006
ZOLTÁN CSABAI
Summary 1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood. 2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(,) of reflecting surfaces detectable polarotactically as ,water' is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (,) for dark reflectors while P(,) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(,) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations ,. The , -dependent reflection,polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ,polarisation sun-dial' of dispersing aquatic insects. [source]

Circadian Activity Rhythms and Mortality: The Study of Osteoporotic Fractures

Colour polymorphism in birds: causes and functions

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2003
P. Galeotti
Abstract We studied polymorphism in all species of birds that are presently known to show intraspecific variation in plumage colour. At least three main mechanisms have been put forward to explain the maintenance of polymorphism: apostatic, disruptive and sexual selection. All of them make partly different predictions. Our aims were to investigate evolutionary causes and adaptive functions of colour polymorphism by taking into account a number of ecological and morphological features of polymorphic species. Overall, we found 334 species showing colour polymorphism, which is 3.5% of all bird species. The occurrence of colour polymorphism was very high in Strigiformes, Ciconiiformes, Cuculiformes and Galliformes. Phylogenetically corrected analysis using independent contrasts revealed that colour polymorphism was maximally expressed in species showing a daily activity rhythm extended to day/night, living in both open and closed habitats. All these findings support the hypothesis that colour polymorphism probably evolved under selective pressures linked to bird detectability as affected by variable light conditions during activity period. Thus, we conclude that selective agents may be prey, predators and competitors, and that colour polymorphism in birds may be maintained by disruptive selection. [source]

Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density

JOURNAL OF FISH BIOLOGY, Issue 2004
M.-L. Bégout Anras
Seabass (Dicentrarchus labrax) swimming activity was compared between natural environments and aquaculture facilities. Behaviour under natural conditions was assessed in a saltmarsh pond (250 m2, 18 × 14 × 0·8 m) using acoustic telemetry. From several surveys, we documented the diel activity rhythm and demonstrated group effects on swimming patterns and amplitudes by comparing activity of solitary fish with that of a fish living in a group of 60. Consequences of weather variability were also analysed and revealed a high sensitivity of fish to atmospheric conditions for both swimming and demand-feeding behaviour. Behaviour in fish tanks was also studied using acoustic telemetry, as part of the EUREKA EU1 960 ,Aqua-Maki 2' project investigating aspects of fish culture in re-circulating tanks under high density. A re-circulating hexagonal tank (5·4 × 5·4 m, 1·8 m depth, 48 m3) was equipped with positioning and demand-feeding systems, oxygen and temperature probes. Initial density was 50 kg m3 in March and rose to 90 kg m3 at the end of the experiment in May. During this period, the movements of nine fish were continuously recorded for 24 h each, reaching a total of six 24 h episode at eight days interval. Swimming activity was analysed in terms of activity rhythms and space occupation specially around feeding events. The two data set and main results will be presented and compared to assess seabass behavioural plasticity and sensitivity to husbandry conditions. [source]

Serotonergic potentiation of dark pulse-induced phase-shifting effects at midday in hamsters

JOURNAL OF NEUROCHEMISTRY, Issue 3 2008
Jorge Mendoza
Abstract In mammals, resetting of the suprachiasmatic clock (SCN) by behavioral activation or serotonin (5-HT) agonists is mimicked by dark pulses, presented during subjective day in constant light (LL). Because behavioral resetting may be mediated in part by 5-HT inputs to the SCN, here we determined whether 5-HT system can modulate dark-induced phase-shifts in Syrian hamsters housed in LL. Two hours of darkness at mid-subjective day (circadian time 6; CT-6) resulted in increased concentrations of 5-HT in the SCN tissue and induction of c-FOS expression in the raphe nuclei. Injections of the 5-HT1A/7 agonist (+)8-OH-DPAT or dark pulses at CT-6 induced phase-advances of the wheel-running activity rhythm and down-regulated the expression of the clock genes Per1-2 and c-FOS in the SCN in a similar way. The combination of both treatments [(+)8-OH-DPAT + dark pulses], however, resulted in larger phase-advances, while associated molecular changes were not significantly modified, except for the gene Dbp, in comparison to (+)8-OH-DPAT or dark pulses alone. Dark resetting was blocked by pre-treatment with a 5-HT7 antagonist, but not with a 5-HT1A antagonist. The additive phase-shifts of two different cues to reset the SCN clock open wide the gateway for non-photic shifting, leading to new strategies in chronotherapy. [source]

Chronic Ethanol Disrupts Circadian Photic Entrainment and Daily Locomotor Activity in the Mouse

ALCOHOLISM, Issue 7 2010
Allison J. Brager
Background:, Chronic ethanol abuse is associated with disrupted circadian rhythms and sleep. Ethanol administration impairs circadian clock phase-resetting, suggesting a mode for the disruptive effect of alcohol abuse on circadian timing. Here, we extend previous studies to explore the effects of chronic forced ethanol on photic phase-resetting, photic entrainment, and daily locomotor activity patterns in C57BL/6J mice. Methods:, First, microdialysis was used to characterize the circadian patterns of ethanol uptake in the suprachiasmatic (SCN) circadian clock and correlate this with systemic ethanol levels and episodic drinking of 10 or 15% ethanol. Second, the effects of chronic forced ethanol drinking and withdrawal on photic phase-delays of the circadian activity rhythm were assessed. Third, the effects of chronic ethanol drinking on entrainment to a weak photic zeitgeber (1 minute of 25 lux intensity light per day) were assessed. This method was used to minimize any masking actions of light that could mask ethanol effects on clock entrainment. Results:, Peak ethanol levels in the SCN and periphery occurred during the dark phase and coincided with the time when light normally induces phase-delays in mice. These delays were dose-dependently inhibited by chronic ethanol and its withdrawal. Chronic ethanol did not impede re-entrainment to a shifted light cycle but affected entrainment under the weak photic zeitgeber and disrupted the daily pattern of locomotor activity. Conclusions:, These results confirm that chronic ethanol consumption and withdrawal markedly impair circadian clock photic phase-resetting. Ethanol also disturbs the temporal structure of nighttime locomotor activity and photic entrainment. Collectively, these results suggest a direct action of ethanol on the SCN clock. [source]

Effect of MT1 melatonin receptor deletion on melatonin-mediated phase shift of circadian rhythms in the C57BL/6 mouse

JOURNAL OF PINEAL RESEARCH, Issue 2 2005
M. L. Dubocovich
Abstract:, In the mouse suprachiasmatic nucleus (SCN), melatonin activates MT1 and MT2 G-protein coupled receptors, which are involved primarily in inhibition of neuronal firing and phase shift of circadian rhythms. This study investigated the ability of melatonin to phase shift circadian rhythms in wild type (WT) and MT1 melatonin receptor knockout (KO) C57BL/6 mice. In WT mice, melatonin (90 ,g/mouse, s.c.) administered at circadian time 10 (CT10; CT12 onset of activity) significantly phase advanced the onset of the circadian activity rhythm (0.60 ± 0.09 hr, n = 41) when compared with vehicle treated controls (,0.02 ± 0.07 hr, n = 28) (P < 0.001). In contrast, C57 MT1KO mice treated with melatonin did not phase shift circadian activity rhythms (,0.10 ± 0.12 hr, n = 42) when compared with vehicle treated mice (,0.12 ± 0.07 hr, n = 43). Similarly, in the C57 MT1KO mouse melatonin did not accelerate re-entrainment to a new dark onset after an abrupt advance of the dark cycle. In contrast, melatonin (3 and 10 pm) significantly phase advanced circadian rhythm of neuronal firing in SCN brain slices independent of genotype with an identical maximal shift at 10 pm (C57 WT: 3.61 ± 0.38 hr, n = 3; C57 MT1KO: 3.45 ± 0.11 hr, n = 4). Taken together, these results suggest that melatonin-mediated phase advances of circadian rhythms of neuronal firing in the SCN in vitro may involve activation of the MT2 receptor while in vivo activation of the MT1 and possibly the MT2 receptor may be necessary for the expression of melatonin-mediated phase shifts of overt circadian activity rhythms. [source]

Developmental Alcohol Exposure Alters Light-Induced Phase Shifts of the Circadian Activity Rhythm in Rats

Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia

PSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 4 2004
ARVID SKJERVE psyd
Abstract Ten elderly subjects with severe dementia were given bright light (5000,8000 lux) for 45 min each morning for 4 weeks. Two rating scales of behavioral symptoms in dementia were used as outcome measures: Cohen-Mansfield Agitation Inventory (CMAI) and Behavior Pathology In Alzheimer's Disease Rating Scale (BEHAVE-AD), a scale for sleep,wake disturbances, and actigraphy to monitor activity rhythm. Behavioral symptoms improved with treatment. No changes in sleep,wake measures were found. There was an advance of the activity rhythm acrophase during treatment. These results suggest that short-time bright light improves behavioral symptoms and aspects of activity rhythm disturbances even in severely demented subjects. [source]

Actigraphic assessment of the circadian rest,activity rhythm in elderly patients hospitalized in an acute care unit

PSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 1 2003
Stéphane Vinzio RD
Abstract Hospitalization for acute illness is a major risk factor of rest,activity rhythm disturbance among elderly subjects. The rest,activity rhythm is disturbed by the acute illness, aging and hospital environment. The purpose of this study is to assess the rest,activity rhythm and light exposure (using a wrist worn actigraph) of 10 patients (mean age 81 years, seven females) admitted on an acute care unit, suffering from cardiac, respiratory or renal acute disease. A non-parametric method was used to analyze activity data. With an improvement of the underlying diseases, the mean relative amplitude of rhythm increased from 0.31 ± 0.19 for the first 5-day period after admission to 0.54 ± 0.21 for the second period before discharge (P < 0.05). The amount of time at night spent above a lighting threshold of 50 lux decreased from 31.4 to 12.3 min between the two periods. The rhythm of elderly subjects hospitalized in the acute care unit is severely altered during the initial period and is progressively resynchronized following clinical improvement. Under the acute underlying disease and/or aging, environmental conditions (light, noise) should be considered to maintain regular rest,activity rhythm. [source]

Loss of photic entrainment at low illuminances in rats with acute photoreceptor degeneration

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
Domitille L. Boudard
Abstract In several species, an acute injection of N -methyl- N -nitrosourea (MNU) induces a retinal degeneration characterized principally by a rapid loss of the outer nuclear layer, the other layers remaining structurally intact. It has, however, also been reported that down-regulation of melanopsin gene expression is associated with the degeneration and is detectable soon after injection. Melanopsin is expressed by a small subset of intrinsically photosensitive retinal ganglion cells and plays an important role in circadian behaviour photoentrainment. We injected MNU into Long Evans rats and investigated the ability of animals to entrain to three light/dark cycles of different light intensities (300, 15 and 1 lux). Control animals entrained their locomotor activity rhythms to the three cycles. In contrast, MNU-treated animals could only entrain properly to the 300 lux cycle. For the 15 lux cycle, their phase angle was much altered compared with control animals, and for the 1 lux cycle, MNU-injected animals were unable to photoentrain and exhibited an apparent free-run activity pattern with a period of 24.3 h. Subsequent to behavioural studies the animals were killed and rod, cone, melanopsin expression and melanopsin-expressing cells were quantified. Rod and cone loss was almost complete, melanopsin protein was reduced by 83% and melanopsin-expressing cells were reduced by 37%. Our study provides a comprehensive model of photoreceptor degeneration at the adult stage and a simple and versatile method to investigate the relation between retinal photoreceptors and the circadian system. [source]

Nerve growth factor-induced circadian phase shifts and MAP kinase activation in the hamster suprachiasmatic nuclei

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2005
Gastón A. Pizzio
Abstract Circadian rhythms are entrained by light and by several neurochemical stimuli. In hamsters housed in constant darkness, i.c.v. administration of nerve growth factor (NGF) at various times in their circadian cycle produced phase shifts of locomotor activity rhythms that were similar in direction and circadian timing to those produced by brief pulses of light. Moreover, the effect of NGF and light were not additive, indicating signalling points in common. These points include the immediate-early gene c-fos and ERK1/2, a component of the mitogen-activated protein kinases (MAPK) family. NGF activates c-FOS and ERK1/2-MAPK in the suprachiasmatic nuclei, the site of a circadian clock in mammals, when administered during the subjective night but not during the day. The effect of NGF on ERK1/2 activation was not inhibited by the administration of MK-801, a glutamate/NMDA receptor antagonist. These results suggest that NGF, acting through MAPK activation, plays a role in photic entrainment of the mammalian circadian clock. [source]

A hVIPR transgene as a novel tool for the analysis of circadian function in the mouse suprachiasmatic nucleus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003
V. M. King
Abstract A mouse bearing a novel transgene encoding the human VPAC2 receptor (hVIPR; Shen et al. (2000) PNAS, 97, 11575,11580) was used to investigate circadian function in the hypothalamic suprachiasmatic nuclei (SCN). Neurons expressing hVPAC2R, detected by a beta-galactosidase (,-GAL) tag, have a distinct distribution within the SCN, closely matching that of neurophysin (NP) neurons and extending into the region of peptide histidine isoleucine (PHI) cells. In common with NP and PHI cells, neurons expressing hVPAC2R are circadian in nature, as revealed by synchronous rhythmic expression of mPERIOD (mPER) proteins. A population of SCN cells not expressing PHI, NP or hVPAC2R exhibited circadian PER expression antiphasic with the rest of the SCN. Nocturnal light exposure induced mPER1 in the ventral SCN and mPER2 widely across the nucleus. Induction of nuclear mPER2 in hVPAC2R cells confirmed their photic responsiveness. Having established their circadian properties, we tested the utility of SCN neurons expressing the hVIPR transgene as functionally and anatomically explicit markers for SCN tissue grafts. Prenatal SCN tissue from hVIPR transgenic pups survived transplantation into adult CD1 mice, and expressed ,-GAL, PER and PHI. Over a series of studies, hVIPR transgenic SCN grafts restored circadian activity rhythms to 17 of 72 arrhythmic SCN lesioned recipients (23.6%). By using heterozygous hVIPR transgenic grafts on a heterozygous Clock mutant background we confirmed that restored activity rhythms were conferred by the donor tissue. We conclude that the hVIPR transgene is a powerful and flexible tool for examination of circadian function in the mouse SCN. [source]

Circadian Activity Rhythms and Mortality: The Study of Osteoporotic Fractures

Effects of environmental variables on fish feeding ecology: implications for the performance of baited fishing gear and stock assessment

JOURNAL OF FISH BIOLOGY, Issue 6 2004
A. W. Stoner
The effectiveness of baited fishing gear ultimately depends upon behaviour of the target species , activity rhythms, feeding motivation, and sensory and locomotory abilities. While any environmental parameter that mediates feeding or locomotion can have an important influence on the active space presented by the bait and fish catchability, few biologists have considered how such variation in behaviour might affect catch per unit effort (CPUE) and the resultant stock abundance estimates or population parameters. This review reveals that environment-related variation in feeding behaviour can act through four different mechanisms: metabolic processes, sensory limitations, social interactions and direct impacts. Water temperature, light level, current velocity and ambient prey density are likely to have largest effects on fish catchability, potentially affecting variation in CPUE by a factor of ten. Feeding behaviour is also density-dependent, with both positive and negative effects. Over time and geographic space a target species can occupy wide ranges of environmental conditions, and in certain cases, spatial and temporal variation in feeding biology could have a larger impact on CPUE than patterns of abundance. Temperature, light and current can be measured with relative facility and corrections to stock assessment models are feasible. Making corrections for biological variables such as prey density and bait competitors will be more difficult because the measurements are often not practical and relationships to feeding catchability are more complex and poorly understood. There is a critical need for greater understanding of how environmental variables affect feeding-related performance of baited fishing gear. A combination of field observations and laboratory experiments will be necessary to parameterize stock assessment models that are improved to accommodate variation in fish behaviour. Otherwise, survey data could reveal more about variation in behaviour than abundance trends. [source]

Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density

Effect of MT1 melatonin receptor deletion on melatonin-mediated phase shift of circadian rhythms in the C57BL/6 mouse

Analysis of the activity patterns of two sympatric sandfly siblings of the Lutzomyia longipalpis species complex from Brazil

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2008
G. B. S. RIVAS
AbstractLutzomyia longipalpis s.l. (Lutz & Neiva) (Diptera: Psychodidae) is the main vector of visceral leishmaniasis in Latin America. Differences in copulation songs, pheromones and molecular markers show that L. longipalpis is a species complex in Brazil. The patterns of activity of insect vectors are important in disease transmission. In addition, differences in activity rhythms have a potential role as a temporal reproductive isolation mechanism in closely related species. We compared the activity patterns of males and females of two sympatric species of the Longipalpis complex from Sobral (Ceará State, Brazil) in controlled laboratory conditions. We observed small but significant differences between the two species in the activity phase in both males and females. [source]

Implementation of pigment-dispersing factor-immunoreactive neurons in a standardized atlas of the brain of the cockroach Leucophaea maderae

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 20 2010
Hongying Wei
Abstract The cockroach Leucophaea maderae is an established model in circadian rhythm research. Its circadian clock is located in the accessory medulla of the brain. Pigment-dispersing factor-immunoreactive (PDF-ir) neurons of the accessory medulla act as circadian pacemakers controlling locomotor activity rhythms. To characterize the neuronal network of the circadian system in L. maderae, the PDF-ir neurons were implemented into a standardized three-dimensional atlas of the cockroach brain. Serial confocal images from 20 wholemount brains were used for the construction of the atlas comprising 21 neuropils. Two different standardization protocols were employed: the iterative shape averaging (ISA) procedure using an affine transformation followed by iterative non-rigid registrations, and the virtual insect brain (VIB) protocol employing local non-rigid transformations after global and local rigid transformations. Quantitative analysis of the 20 brains revealed that volumes of the accessory medulla are directly correlated with the volumes of the medulla, the protocerebral bridge, and the upper division of the central body, suggesting functional connections among these neuropils. For a standardized reconstruction of the circadian pacemaker network, the ISA protocol was used to register PDF-ir neurons in the standard cockroach brain. The registration revealed that two PDF-ir arborization areas in the brain are highly interconnected with other PDF-ir projection sites and appear to be contacted both by fibers in the posterior and the anterior optic commissures. The distances between PDF-ir branching areas show specific numerical relationships that might be physiologically relevant for temporal encoding. J. Comp. Neurol. 518:4113,4133, 2010. © 2010 Wiley-Liss, Inc. [source]

Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energetics

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 1 2005
Natalie Vasey
Abstract The activity budgets and daily activity rhythms of Varecia rubra were examined over an annual cycle according to season and reproductive stage. Given the relatively high reproductive costs and patchy food resources of this species, I predicted that V. rubra would 1) travel less and feed more during seasonal resource scarcity in an attempt to maintain energy balance, and 2) show sex differences in activity budgets due to differing reproductive investment. Contrary to the first prediction, V. rubra does not increase feeding time during seasonal food scarcity; rather, females feed for a consistent amount of time in every season, whereas males feed most during the resource-rich, hot dry season. The results are consistent with other predictions: V. rubra travels less in the resource-scarce cold rainy season, and there are some pronounced sex differences, with females feeding more and resting less than males in every season and in every reproductive stage except gestation. However, there are also some provocative similarities between the sexes when activity budgets are examined by reproductive stage. During gestation, female and male activity budgets do not differ and appear geared toward energy accumulation: both sexes feed and rest extensively and travel least during this stage. During lactation, activity budgets are geared toward high energy expenditure: both sexes travel most and in equal measure, and rest least, although it remains the case that females feed more and rest less than males. These similarities between female and male activity budgets appear related to cooperative infant care. The high energetic costs of reproduction in V. rubra females may require that they allot more time to feeding year round, and that their overall activity budget be more directly responsive to seasonal climate change, seasonal food distribution, and reproductive schedules. Am. J. Primatol. 66:23,44, 2005. [source]