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Journal of Experimental Biology

Jessica L Baylor, Michael W Butler
An effective immune response results in the elimination of pathogens, but this immunological benefit may be accompanied by increased levels of oxidative damage. However, organisms have evolved mechanisms to mitigate the extent of such oxidative damage, including the production and mobilization of antioxidants. One potential mechanism of mitigating immune-challenge-induced changes in oxidative physiology is increasing biliverdin production. Biliverdin is chemically an antioxidant, but within-tissue correlations between biliverdin concentration and oxidative damage have never been directly examined...
February 15, 2019: Journal of Experimental Biology
Kevin T Bilyk, Xuan Zhuang, Katherine R Murphy, C-H Christina Cheng
Evolution of Antarctic notothenioid fishes in the isolated freezing Southern Ocean have led to remarkable trait gains and losses. One of the most extraordinary was the loss of the major oxygen carrier hemoglobin (Hb) in the icefishes (family Channichthyidae). While the mechanisms of this loss and the resulting compensatory changes have been well studied, the impact of Hb loss on the network of genes that once supported its recycling and disposal has remained unexplored. Here we report the functional fate and underlying molecular changes of two such key Hb-supporting proteins across the icefish family - haptoglobin (Hp) and hemopexin (Hx), crucial in removing cytotoxic free Hb and heme respectively...
February 14, 2019: Journal of Experimental Biology
Melanie Williams, Domenico Barranca, Carol Bucking
Trout caeca are vermiform structures projecting from the anterior intestine of the gastrointestinal tract. Despite their simple gross morphology, these appendages are physically distinct along the anterior-posterior axis and ultrastructural evidence suggests zonation of function within the structures. Individual caeca from three sections (anterior, middle, posterior) were removed from the intestine of freshwater rainbow trout and investigated for ion transport and enzyme activity. Ca2+ absorption appeared as a combination of active and passive movement, with Michaelis-Menten kinetics observable under symmetrical conditions, and was inhibited by several pharmacological agents (ouabain, La3+ , and a calmodulin antagonist)...
February 14, 2019: Journal of Experimental Biology
Vinicius Araújo Armelin, Victor Hugo da Silva Braga, Igor Noll Guagnoni, Ariela Maltarolo Crestani, Augusto Shinya Abe, Luiz Henrique Florindo
Orthostatic hypotension is a phenomenon triggered by a change in the position or posture of an animal, from a horizontal to a vertical head-up orientation, characterised by a blood pooling in the lower body and a reduction in central and cranial arterial blood pressure ( P A ). This hypotension elicits systemic vasoconstriction and tachycardia, which generally reduce blood pooling and increase P A Little is known about the mediation and importance of such cardiovascular adjustments that counteracts the haemodynamic effects of orthostasis in ectothermic vertebrates, and some discrepancies exist in the knowledge available on this subject...
February 13, 2019: Journal of Experimental Biology
Riad Akhundov, David J Saxby, Suzi Edwards, Suzanne Snodgrass, Phil Clausen, Laura E Diamond
Determining the signal quality of surface electromyography (sEMG) recordings is time consuming and requires the judgment of trained observers. An automated procedure to evaluate sEMG quality would streamline data processing and reduce time demands. This paper compares the performance of two supervised and three unsupervised artificial neural networks (ANNs) in evaluation of sEMG quality. Manually classified sEMG recordings from various lower-limb muscles during motor tasks were used to train (n=28000), test performance (n=12000), and evaluate accuracy (n=47000) of the five ANNs in classifying signals into four categories...
February 13, 2019: Journal of Experimental Biology
Blanca Arroyo-Correa, Ceit Beattie, Mario Vallejo-Marín
During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here we analysed floral vibrations produced by four closely related bumblebee taxa ( Bombus spp. ) on two buzz-pollinated plants species ( Solanum spp. )...
February 13, 2019: Journal of Experimental Biology
Grant Navid Doering, Stephen C Pratt
Maintenance of a social group requires the ability to reach consensus when faced with divisive choices. Thus, when migrating colonies of the ant Temnothorax rugatulus split among multiple sites, they can later reunify on the basis of queen location or differences in site quality. In this study, we found that colonies can reunify even without obvious cues to break the symmetry between sites. To learn how they do so, we observed both symmetric reunifications (between identical nests) and asymmetric reunifications (between nests of unequal quality) by colonies of individually-marked ants...
February 13, 2019: Journal of Experimental Biology
A Fahlman, M Brodsky, S Miedler, S Dennison, M Ivančić, G Levine, J Rocho-Levine, M Manley, J Rocabert, A Borque Espinosa
We measured respiratory flow ( V̇ ), breathing frequency ( f R ), tidal volume ( V T ), breath durations, and end-expired O2 content in bottlenose dolphins ( Tursiops truncatus ) before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O2 , tidal volume V T , and f R following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering V T , and f R to rapidly restore the O2 stores. For the first breath following a surface breath-hold, the end-expired O2 decreased with dive duration, while V T , and f R increased...
February 13, 2019: Journal of Experimental Biology
Marco Bonato, Paola Bagnoli, Cinzia Centelleghe, Mike Maric, Ginevra Brocca, Sandro Mazzariol, Bruno Cozzi
The retia mirabilia are vascular nets composed by small vessels dispersed among numerous veins, allowing blood storage, regulation of flow, and pressure damping effects. Here we investigated their potential role during the diving phase of the bottlenose dolphin ( Tursiops truncatus ). To this effect, the whole vertebral retia mirabilia of a series of dolphins were removed during post-mortem analysis and examined to assess vessel diameters, estimate vascular volume, and flow rate. Here we formulate a new hemodynamic model to help clarify vascular dynamics throughout the diving phase, based on the total blood volume of a bottlenose dolphin, and using data available about the perfusion of the main organs and body systems...
February 13, 2019: Journal of Experimental Biology
Giuseppe Bianco, Robin Clemens Köhler, Mihaela Ilieva, Susanne Åkesson
Several invertebrate and vertebrate species have been shown to align their body relative to the geomagnetic field. Many hypotheses have been proposed to explain the adaptive significance of magnetic body alignment outside the context of navigation. However, experimental evidence to investigate alternative hypotheses is still limited. We present a new setup to track the preferential body alignment relative to the geomagnetic field in captive animals using computer vision. We tested our method on three species of migratory songbirds and provide evidence that they align their body with the geomagnetic field...
February 6, 2019: Journal of Experimental Biology
Kathrin Kugler, Harald Luksch, Herbert Peremans, Dieter Vanderelst, Lutz Wiegrebe, Uwe Firzlaff
Echolocating bats are known to fly and forage in complete darkness using the echoes of their actively emitted calls to navigate and to detect prey. However, under dim light conditions many bats can also rely on vision. Many flying animals have been shown to navigate by optic flow information, and recently, bats were shown to exploit echo-acoustic flow to navigate through dark habitats. Here we show for the bat Phyllostomus discolor that in lighted habitats where self-motion induced optic flow is strong, optic and echo-acoustic flow interact in their efficiency to guide navigation...
February 6, 2019: Journal of Experimental Biology
Chi-Chih Wu, Axel Klaesson, Julia Buskas, Petter Ranefall, Reza Mirzazadeh, Ola Söderberg, Jochen B W Wolf
Functional validation of candidate genes involved in adaptation and speciation remains challenging. We here exemplify the utility of a method quantifying individual mRNA transcripts in revealing the molecular basis of divergence in feather pigment synthesis during early-stage speciation in crows. Using a padlock probe assay combined with rolling circle amplification, we quantified cell type specific gene expression in the histological context of growing feather follicles. Expression of Tyrosinase Related Protein 1 (TYRP1), Solute Carrier Family 45 member 2 (SLC45A2) and Hematopoietic Prostaglandin D Synthase (HPGDS) was melanocyte-limited and significantly reduced in follicles from hooded crow explaining the substantially lower eumelanin content in grey vs...
February 4, 2019: Journal of Experimental Biology
Yi-Fen Lin, Nicolai Konow, Elizabeth R Dumont
The interplay between morphological specialization and kinematic flexibility is important for organisms that move between habitats within different substrates. Burrowing is energetically expensive and requires substantial interaction with soil to dislodge and transport it. True moles (Talpidae) have extraordinary forelimb morphologies and a unique ability to dig in loose as well as compact soils, yet we know little of how moles coordinate their forelimb joint kinematics when digging in soils of different compactness...
February 4, 2019: Journal of Experimental Biology
Norma Martínez-Lendech, Marcela Osorio-Beristain, Bernardo Franco, Mario Pedraza-Reyes, Armando Obregón, Jorge Contreras-Garduño
In invertebrates, it has been recently reported that secondary sexual characteristics (SSC) reflect the antioxidant defense of their bearers, but it is not known what physiological link maintains the honesty of those signals. Here, we use the damselfly Hetaerina americana to test whether Juvenile Hormone plays such a role. First, we analyzed whether oxidative damage is a real threat in natural damselfly populations by examining the accumulation of oxidized guanines as a function of age in males. Then, we injected paraquat (a pro-oxidant agent) and added the Juvenile Hormone analog Methoprene (JHa) to the experimental group and the JHa vehicle (acetone) to the control group, to determine whether JHa increases the levels of pro-oxidants and antioxidants...
February 4, 2019: Journal of Experimental Biology
Akifumi Matsuo, Mirai Mizutani, Ryu Nagahara, Testuo Fukunaga, Hiroaki Kanehisa
How external mechanical work done during maximal acceleration sprint running changes with increasing running velocity and is associated with running performance remains unknown. This study aimed to elucidate them. In twelve young males, work done at each step over 50 m from the start was calculated from mechanical energy changes in horizontal anterior-posterior and vertical directions and was divided into that in each of braking ( negW kap and negW v , respectively) and propulsive ( posW kap and posW v , respectively) phases...
February 4, 2019: Journal of Experimental Biology
Hannah E Aichelman, Richard C Zimmerman, Daniel J Barshis
Variation in environmental characteristics and divergent selection pressures can drive adaptive differentiation across a species' range. Astrangia poculata is a temperate scleractinian coral that provides unique opportunities to understand the roles of phenotypic plasticity and evolutionary adaptation in coral physiological tolerance limits. A. poculata inhabits hard bottom ecosystems from the northwestern Atlantic to the Gulf of Mexico and withstands an annual temperature range up to 20°C. Additionally, A...
February 4, 2019: Journal of Experimental Biology
Amanda A Lindeman, Jayne E Yack
Many insects vary their song patterns to communicate different messages, but the underlying biomechanisms are often poorly understood. Here we report on the mechanics of sound production and variation in an elytro-tergal stridulator, male Dendroctonus valens bark beetles. Using ablation experiments coupled with high-speed video and audio recordings, we show that: 1. chirps are produced using a stridulatory file on the left elytron (forewing) and a protrusion (plectrum) on the seventh abdominal segment; 2. chirps are produced by 'spring stridulation', a catch-and-release mechanism whereby the plectrum catches on a file tooth, and upon release, springs forward along the file; and 3...
January 28, 2019: Journal of Experimental Biology
Timothy M Healy, Patricia M Schulte
Phenotypic plasticity is an important aspect of an organism's response to environmental change that often requires the modulation of gene expression. These changes in gene expression can be quantitative as a result of increases or decreases in the amounts of specific transcripts, or qualitative as a result of the expression of alternative transcripts from the same gene (e.g., via alternative splicing of pre-mRNAs). Although the role of quantitative changes in gene expression in phenotypic plasticity is well known, relatively few studies have examined the role of qualitative changes...
January 28, 2019: Journal of Experimental Biology
Hiroshi Matsui, Ei-Ichi Izawa
Pecking in birds is analogous to reaching and grasping movements in primates. Earlier studies on visuomotor control in birds, which were conducted mostly in pigeons, suggested that avian pecking is controlled feedforwardly, and is out of the control of visual guidance during movement. However, recent studies using crows suggested a role of vision in pecking control during movement. To unveil what visuomotor mechanisms underlie the flexibility of pecking in crows, the current study examined whether pigeons and crows adjust their pecking to the visual distortion induced by prisms...
January 25, 2019: Journal of Experimental Biology
Aurélien Lowie, Elisa Gillet, Bieke Vanhooydonck, Duncan J Irschick, Jonathan B Losos, Anthony Herrel
The ability of an animal to run fast has important consequences on its survival capacity and overall fitness. Previous studies have documented how variation in the morphology of the limbs is related to variation in locomotor performance. Although these studies have suggested direct relations between sprint speed and hind limb morphology, few quantitative data exist. Consequently, it remains unclear whether selection acts in limb segment lengths, overall muscle mass or muscle architecture (e.g. muscle fiber length and cross-sectional area)...
January 25, 2019: Journal of Experimental Biology
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