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Journal of Experimental Biology

Neha Agarwal, Ila Mishra, Ruchi Komal, Sangeeta Rani, Vinod Kumar
We investigated if circannual rhythms underlying annual testis maturation and moult cycles were independent of the duration and frequency of light period and the circadian clock control in non-photoperiodic spotted munia. Birds were subjected to an aberrant light-dark (LD) cycle (3.5L:3.5D; T7, T=period length of LD cycle) and continuous light (LL, 24L:0D), with controls on 12L:12D (T24, 24 h LD cycle). Initial experiment measured the activity pattern and 24 h mRNA oscillations of circadian clock genes (bmal1, clock, per2, cry1, cry2) in the hypothalamus, putative site of the seasonal timing...
September 15, 2017: Journal of Experimental Biology
Allison Cornell, Tony D Williams
In avian species, little is known about the development of physiological traits in the days preceding fledging, a critical life history transition marked by a high mortality rate. Developmental trajectory during this period may be flexible based on ecological context or hardwired, with potential costs for variation in growth in the form of oxidative stress. Patterns in development are likely to relate to variation in life history, for which seabirds and aerial insectivores have been well studied, while our focal species is a grassland ground forager, the European starling (Sturnus vulgaris)...
September 15, 2017: Journal of Experimental Biology
José Guilherme Chaui-Berlinck, Luiz Henrique Alves Monteiro
The Frank-Starling Law of the heart is a filling-force mechanism (FFm), a positive relationship between the distension of a ventricular chamber and its force of ejection, and such a mechanism is found across all the studied vertebrate lineages. The functioning of the cardiovascular system is usually described by means of the cardiac and vascular functions, the former related to the contractility of the heart and the latter related to the after-load imposed to the ventricle. The crossing of these functions is the so-called operation point, and the FFm is supposed to play a stabilizing role for the short-term variations in the working of the system...
September 14, 2017: Journal of Experimental Biology
Moshe Nagari, Yafit Brenner, Guy Bloch
"Nurse" honeybees tend brood around-the-clock with attenuated or no circadian rhythms, but the brood signals inducing this behavior remain elusive. We first tested the hypothesis that worker circadian rhythms are regulated by brood pheromones. We monitored locomotor activity of individually isolated nurse bees that were either exposed to various doses of larval extracts or synthetic brood ester pheromone (BEP). Bees orally treated with larvae extracts showed attenuated circadian rhythms in one of four tested colonies; a similar but statistically non-significant trend was seen in two additional colonies...
September 14, 2017: Journal of Experimental Biology
Mário S Cervoni, Carlos A M Cardoso-Júnior, Giovana Craveiro, Anderson de O Souza, Luciane C Alberici, Klaus Hartfelder
During adult life, honeybee workers undergo a succession of behavioral states. Nurses bees perform tasks inside the nest, and when they are about 2-3 weeks old they initiate foraging. This switch is associated with alterations in diet, and with the levels of juvenile hormone and vitellogenin circulating in hemolymph. Less clear is whether this behavioral maturation involves major changes at the cellular level, such as mitochondrial activity and the redox environment in the head, thorax and abdomen. Using high-resolution respirometry, biochemical assays and RT-qPCR, we evaluated the association of these parameters with this behavioral change...
September 14, 2017: Journal of Experimental Biology
Nicholas B Pollock, Stephanie Feigin, Marko Drazenovic, Henry B John-Alder
Sexual differences in adult body size (sexual size dimorphism; SSD) and color (sexual dichromatism) are widespread, and both male- and female-biased dimorphisms are observed even among closely related species. A growing body of evidence indicates testosterone (T) can regulate growth, thus the development of SSD, and sexual dichromatism. However, the mechanism(s) underlying these effects are conjectural, including possible conversions of T to estradiol (E2) or 5 α-dihydrotestosterone (DHT). In the present study, we hypothesized that effects of T are physiological responses mediated by androgen receptors, and we tested two specific predictions: 1) that DHT would mimic effects of T by inhibiting growth and enhancing coloration, and 2) that removal of endogenous T via surgical castration would stimulate growth...
September 14, 2017: Journal of Experimental Biology
Vanessa K Hilliard Young, Charlotte E Wienands, Brittany P Wilburn, Richard W Blob
During evolutionary reinvasions of water by terrestrial vertebrates, ancestrally tubular limb bones often flatten to form flippers. Differences in skeletal loading between land and water might have facilitated such changes. In turtles, femoral shear strains are significantly lower during swimming than during walking, potentially allowing a release from loads favoring tubular shafts. However, flipper-like morphology in specialized tetrapod swimmers is most accentuated in the forelimbs. To test if the forelimbs of turtles also experience reduced torsional loading in water, we compared strains on the humerus of river cooters (Pseudemys concinna) between swimming and terrestrial walking...
September 7, 2017: Journal of Experimental Biology
Amelie Werkhausen, Kirsten Albracht, Neil J Cronin, Rahel Meier, Jens Bojsen-Møller, Olivier R Seynnes
The compliance of elastic elements allows muscles to dissipate energy safely during eccentric contractions. This buffering function is well documented in animal models but our understanding of its mechanism in humans is confined to non-specific tasks, requiring a subsequent acceleration of the body. The present study aimed to examine the behaviour of the human triceps surae muscle-tendon unit (MTU) during a pure energy dissipation task, under two loading conditions.Thirty-nine subjects performed a single-leg landing task, with- and without added mass...
September 7, 2017: Journal of Experimental Biology
Mark R Saddler, Alessandro Bocconcelli, Leigh S Hickmott, Gustavo Chiang, Rafaela Landea-Briones, Paulina A Bahamonde, Gloria Howes, Paolo S Segre, Laela S Sayigh
Vocal behavior of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile, was analyzed using both audio and accelerometer data from digital acoustic recording tags (DTAGs). Over the course of three austral summers (2014, 2015, 2016), seventeen tags were deployed, yielding 124 hours of data. We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations, and timing consistent with previous recordings made using towed and moored hydrophones. We also describe tonal downswept (D) calls, which have not been previously described for this population...
September 7, 2017: Journal of Experimental Biology
Anabela Maia, George V Lauder, Cheryl D Wilga
A key feature of fish functional design is the presence of multiple fins that allow thrust vectoring and redirection of fluid momentum to contribute to both steady swimming and maneuvering. A number of previous studies have analyzed the function of dorsal fins in teleost fishes in this context, but the hydrodynamic function of dorsal fins in freely-swimming sharks has not been analyzed, despite the potential for differential functional roles between the anterior and posterior dorsal fins. Previous anatomical research has suggested a primarily stabilizing role for shark dorsal fins...
September 7, 2017: Journal of Experimental Biology
Sepand Riyahi, Roser Vilatersana, Aaron W Schrey, Hassan Ghorbani Node, Mansour Aliabadian, Juan Carlos Senar
Epigenetic modifications can respond rapidly to environmental changes and can shape phenotypic variation in accordance with environmental stimuli. One of the most studied epigenetic marks is DNA methylation. In the present study, we used the MSAP technique to investigate the natural variation in DNA methylation within and among subspecies of the house sparrow Passer domesticus. We focused on five subspecies from the Middle East because they show great variation in many ecological traits and because this region is the probable origin for the house sparrow's commensal relationship with humans...
September 6, 2017: Journal of Experimental Biology
Yuta Kawasaki, Hitoshi Nishimura, Sakiko Shiga
Two-day rhythms referred to as circabidian rhythms were reported in humans and mosquitos. However, these rhythms only appear under constant conditions, and functional mechanisms of two-day rhythms have not been known. Here, we report clear circabidian rhythms of large black chafers (Holotrichia parallela, Coleoptera: Scarabaeidae) in both the laboratory and field. Under 12 h light and 12 h dark conditions (LD 12:12) at 25°C, H. parallela appeared on the ground at the beginning of the dark phase every two days...
September 6, 2017: Journal of Experimental Biology
Andrius Pašukonis, Kristina Barbara Beck, Marie-Therese Fischer, Steffen Weinlein, Susanne Stückler, Eva Ringler
Understanding the external stimuli and natural contexts that elicit complex behaviors, such as parental care, is key in linking behavioral mechanisms to their real-life function. Poison frogs provide obligate parental care by shuttling their tadpoles from terrestrial clutches to aquatic nurseries, but little is known about the proximate mechanisms that control these behaviors. In this study, we used Allobates femoralis, a poison frog with predominantly male parental care, to investigate whether tadpole transport can be induced in both sexes by transferring unrelated tadpoles to the backs of adults in the field...
September 1, 2017: Journal of Experimental Biology
David Hazlerigg, Arnoldus Schytte Blix, Karl-Arne Stokkan
At temperate latitudes, the annual cycle of day length synchronizes circannual rhythms, and, in mammals, this is mediated via nocturnal production of the pineal hormone melatonin, proportional to the length of the night. Here, we studied circannual synchronization in an arctic species, the reindeer (Rangifer tarandus tarandus), which ceases to produce a rhythmic melatonin signal when it is exposed to extended periods of continuous midwinter darkness, and continuous midsummer light. Using food intake, antler growth and moult as endpoints, we demonstrate that when animals living at 70°N are transferred from natural photoperiods in late autumn to either continuous light or continuous darkness, they undergo a conspicuous acceleration of the circannual program...
September 1, 2017: Journal of Experimental Biology
Patricia Cavelier, Julien Cau, Nathalie Morin, Claude Delsert
While our knowledge of bivalve gametogenesis recently progressed, more molecular markers are needed in order to develop tissue imaging. Here, we identified stem cell and mitotic markers to further characterize the oyster early gametogenesis, mainly through immunofluorescence microscopy.Intense alkaline phosphatase activity, a nonspecific marker for stem cells, was detected on the outer edge of the gonad ducts at the post-spawning stage, suggesting the abundance of undifferentiated cells very early during the sexual cycle...
August 31, 2017: Journal of Experimental Biology
Fargol Nowghani, Sima Jonusaite, Trudy Watson-Leung, Andrew Donini, Scott P Kelly
This study investigated ionoregulatory strategies used by freshwater (FW) nymphs of the mayfly (Hexagenia rigida). Like other FW organisms, H. rigida nymphs maintain hemolymph ion levels (in mM: Na(+)∼102; Cl(-)∼84; K(+)∼6; pH∼7.35) far in excess of their surroundings. This appears to be accomplished by the combined actions of the alimentary canal, Malpighian tubules (MTs) and tracheal gills. The alimentary canal contributes in a region-specific manner; a view supported by (1) spatial differences in the activity of basolateral Na(+)-K(+)-ATPase (NKA) and apical V-type H(+)-ATPase (VA) and (2) region-specific Na(+) and K(+) flux rates...
August 31, 2017: Journal of Experimental Biology
Robert R Fitak, Sönke Johnsen
In studies of animal orientation, data are often represented as directions that can be analyzed using circular statistical methods. Although several circular statistical tests exist to detect the presence of a mean direction, likelihood-based approaches may offer advantages in hypothesis testing - especially when data are multimodal. Unfortunately, likelihood-based inference in animal orientation remains rare. Here, we discuss some of the assumptions and limitations of common circular tests and report a new R package called CircMLE to implement the maximum likelihood analysis of circular data...
August 31, 2017: Journal of Experimental Biology
Luke P Miller, W Wesley Dowd
In complex habitats, environmental variation over small spatial scales can equal or exceed larger-scale gradients. This small-scale variation may allow motile organisms to mitigate stressful conditions by choosing benign microhabitats, whereas sessile organisms may rely on other behaviors to cope with environmental stresses in these variable environments. We developed a monitoring system to track body temperature, valve gaping behavior, and posture of individual mussels (Mytilus californianus) in field conditions in the rocky intertidal zone...
August 29, 2017: Journal of Experimental Biology
Dmitry N Lapshin, Dmitry D Vorontsov
The Johnston's organs (JO) of mosquitoes are the most complex mechanosensitive organs yet found in insects. Previous findings on behavior of mosquitoes suggest that, together with exceptional sensitivity, their auditory system can discriminate frequencies. Analysis of compound responses of the JO did not provide unambiguous evidence of such discrimination, even less did it help to find its mechanism. Using the feedback stimulation method, we measured the tuning frequencies of the JO sensory neurons. Here we present electrophysiological evidence that male mosquitoes of Culex pipiens possess at least eight groups of auditory neurons which are distinct in their frequency tuning, with individual frequencies ranging from 85 to 470 Hz...
August 29, 2017: Journal of Experimental Biology
Roy E Weber, Jennifer U M Jarvis, Angela Fago, Nigel C Bennett
Inhabiting deep and sealed subterranean burrows, mole rats exhibit a remarkable suite of specializations, including eusociality (living in colonies with single breeding queens), extraordinary longevity, cancer immunity and poikilothermy, and extreme tolerance of hypoxia and hypercapnia.With little information available on adjustments in hemoglobin (Hb) function that may mitigate the impact of exogenous and endogenous constraints on the uptake and internal transport of O2, we measured hematological characteristics, as well as Hb-O2 binding affinities and their sensitivities to pH (Bohr effect), CO2, temperature and 2,3 diphosphoglycerate (DPG, the major allosteric modulator of Hb-O2 affinity in the red cells) in four social and two solitary species of African mole rats (family Bathyergidae) originating from different biomes and soil types across Central and Southern Africa...
August 29, 2017: Journal of Experimental Biology
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