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Journal of Experimental Biology

Kevin Jagnandan, Timothy E Higham
Animal locomotion is driven by underlying axial and appendicular musculature. In order for locomotion to be effective, these muscles must be able to rapidly respond to changes in environmental and physiological demands. Although virtually unstudied, muscles must also respond to morphological changes, such as those that occur with tail autotomy in lizards. Tail autotomy in leopard geckos ( Eublepharis macularius ) results in a 25% loss of caudal mass and significant kinematic alterations to maintain stability...
July 19, 2018: Journal of Experimental Biology
Qiao Wang, Weiguo Song, Jun Zhang, Siuming Lo
Foraging and nest relocation forming a bi-directional traffic of outbound and inbound individuals in one-lane organization are two main activities in ants' life. In this paper, we conducted an experiment for nest relocation of loaded and unloaded ants, and some of them move back and forth between the old nest and the new one. In the experiment, we observed both uni- and bi-directional traffic flows of ants. The headway-speed relations indicate that the ants show the same sensitivity to the distance headway in both types of flows...
July 19, 2018: Journal of Experimental Biology
Ian R Hays, Mark E Hauber
Very little is known about how morphology affects the motion, spatial stability, and resulting viability of avian eggs. The limited existing research focuses on the uniquely pyriform egg shapes found in the Alcidae bird family. This unusual shell shape was originally thought to suppress displacement and prevent egg loss on the cliffside nesting habitat of the Uria genus. Unfortunately, these early studies never isolated or quantified the specific morphological features (elongation, asymmetry, and conicality) of these pyriform eggs, which limits their applicability to other taxa and has hampered a robust proof of concept...
July 19, 2018: Journal of Experimental Biology
Craig D Perl, Jeremy E Niven
Metabolic rate and its relationship with body size is a fundamental determinant of many life history traits and potentially of organismal fitness. Alongside various environmental and physiological factors, the metabolic rate of insects is linked to distinct ventilation patterns. Despite significant attention, however, the precise role of these ventilation patterns remains uncertain. Here we determine the allometric scaling of metabolic rate and respiratory water loss in the red wood ant, as well as assessing the effect of movement upon metabolic rate and ventilation pattern...
July 19, 2018: Journal of Experimental Biology
Stefan Pentzold, Veit Grabe, Andrei Ogonkov, Lydia Schmidt, Wilhelm Boland, Antje Burse
Optical imaging of gene expression by fluorescence in situ hybridisation (FISH) in insects is often impeded by their pigmented cuticle. Since most chemical bleaching agents are incompatible with FISH, we developed a RNA interference-based method for clearing cuticular pigmentation which enables using whole-mount body appendages for RNA FISH. Silencing laccase2 or tyrosine hydroxylase in two leaf beetles species ( Chrysomela populi, Phaedon cochleariae ) cleared their pigmented cuticle and decreased light absorbance...
July 19, 2018: Journal of Experimental Biology
Agnieszka Jendroszek, Hans Malte, Cathrine B Overgaard, Kristian Beedholm, Chandrasekhar Natarajan, Roy E Weber, Jay F Storz, Angela Fago
The high blood-O2 affinity of the bar-headed goose ( Anser indicus ) is an integral component of the biochemical and physiological adaptations that allow this hypoxia-tolerant species to undertake migratory flights over the Himalayas. The high blood-O2 affinity of this species was originally attributed to a single amino acid substitution of the major hemoglobin (Hb) isoform, HbA, which was thought to destabilize the low-affinity T-state, thereby shifting the T-R allosteric equilibrium towards the high-affinity R-state...
July 19, 2018: Journal of Experimental Biology
Tim Burton, Bettina Zeis, Sigurd Einum
We present a method for automating the measurement of upper thermal limits in small aquatic organisms. Upper thermal limits are frequently defined by the cessation of movement at high temperature, with measurement being performed by manual observation. Consequently, estimates of upper thermal limits may be subject to error and bias, both within- and among-observers. Our method utilises video-based tracking software to record the movement of individuals when exposed to high, lethal temperature. We develop an algorithm in the R computing language that can objectively identify the loss of locomotory function from tracking data...
July 16, 2018: Journal of Experimental Biology
Neha Acharya-Patel, Courtney A Deck, William K Milsom
Elasmobranchs are a group of cartilaginous fish with no direct sympathetic innervation of the heart or gills. Fast cardiorespiratory regulation is controlled solely by the parasympathetic branch of the autonomic nervous system. Cardiovascular changes associated with ventilation are commonly present in the form of respiratory sinus arrhythmia (RSA) and as cardiorespiratory synchrony (CRS in which there is a 1:1 beat to breath ratio). The latter has been hypothesized to maximize oxygen uptake coupling the pulsatile flows of blood and water in the gills...
July 16, 2018: Journal of Experimental Biology
Jacquelyn M Petzold, José A Alves-Gomes, G Troy Smith
Electrosensory systems of weakly electric fish must accommodate competing demands of sensing the environment (electrolocation) and receiving social information (electrocommunication). The jamming avoidance response (JAR) is a behavioral strategy thought to reduce electrosensory interference from conspecific signals close in frequency. We used playback experiments to characterize electric organ discharge frequency (EODf), chirping behavior, and the JAR of Distocyclus conirostris , a gregarious electric fish species...
July 16, 2018: Journal of Experimental Biology
Torfinn Solvang, Andreas Hagemann
Machine vision represent an accurate and easily verifiable method for observing live organisms and this technology is constantly evolving in terms of accessibility and costs. Motivated by the complexity of observing small-sized aquatic organisms in experimental systems, and the difficulties related to real-time observation, sampling, and counting without interfering with the organisms, we here present a new method for observing behaviour and dispersion of non-sessile zooplankton organisms using a custom-made tank with an associated machine vision system...
July 12, 2018: Journal of Experimental Biology
George S Bakken, Hannes A Schraft, Robert W Cattell, Donna B Tiu, Rulon W Clark
The pit organ defining pit vipers (Crotalinae) contains a membrane covered with temperature receptors that detect thermal radiation from environmental surfaces. Temperature is both the environmental parameter being sensed and the mechanism by which the pit membrane detects the signal. As snakes are ectotherms, temperature also has a strong influence on neurological and locomotor responses to the signal. This study of Pacific Rattlesnakes ( Crotalus oreganus ) systematically examined the effect of body, target, and background temperatures on response to a moving target...
July 11, 2018: Journal of Experimental Biology
Mikus Abolins-Abols, Rachel E Hanauer, Kimberly A Rosvall, Mark P Peterson, Ellen D Ketterson
Organisms are expected to invest less in reproduction in response to a stressor, but theory predicts that this effect should depend on the frequency and duration of stressors in the environment. Here we investigated how an acute stressor affected testes function in a songbird, and how chronic stressors influenced the acute stress response. We exposed male Dark-eyed Juncos ( Junco hyemalis ) either to chronic or minimal (control) disturbance during testicular recrudescence, after which we measured baseline testosterone, testosterone after an acute handling stressor, and capacity to produce testosterone after hormonal stimulation...
July 11, 2018: Journal of Experimental Biology
Chao Li, Xiaojie Wang, Jianyong Wu, Xuguang Zhang, Chunxin Fan, Hongyi Guo, Jiakun Song
Fish detect water motions with their mechanosensory lateral line. The basic functional unit of the lateral line is the neuromast. In most fish species neuromasts are located in lateral line canals (canal neuromasts) or on the skin (superficial neuromasts). In this paper we describe the lateral line system of pufferfish, Takifugu obscurus If threatened, this fish inflates its body by sucking water into the esophagus. Pufferfish lack a canal system but have neuromasts located directly on the skin or in open grooves...
July 11, 2018: Journal of Experimental Biology
P Kalyanasundaram, M A Willis
The hawkmoth Manduca sexta, is nocturnally active, beginning its flight activity at sunset, and executing rapid controlled maneuvers to search for food and mates in dim light conditions. This moth's visual system has been shown to trade off spatial and temporal resolution for increased sensitivity in these conditions. The study presented here uses tethered flying moths to characterize the flight performance envelope of M. sexta 's wide-field-motion-triggered steering response in low light conditions by measuring attempted turning in response to wide-field visual motion...
July 11, 2018: Journal of Experimental Biology
Anna V Ivanina, Ballav M Borah, Angela Vogts, Ifra Malik, Jingyao Wu, Adam R Chin, Alejandro J Almarza, Prashant Kumta, Helen Piontkivska, Elia Beniash, Inna M Sokolova
Species of Ostreidae family are key ecosystem engineers and many of them (including Crassostrea gigas and C. virginica ) are commercially important aquaculture species. Despite similarities in their morphology and ecology, these two species differ in their ability to defend against pathogens potentially reflecting species-specific differential specialization of hemocytes on immune defense vs. biomineralization. To test this hypothesis, we investigated the expression levels of immune and biomineralization-related genes as well as mineralogical and mechanical properties of the shells and the calcium sequestration ability of the hemocytes of C...
July 11, 2018: Journal of Experimental Biology
Edward P Snelling, Shane K Maloney, Anthony P Farrell, Leith C R Meyer, Adian Izwan, Andrea Fuller, Duncan Mitchell, Anna Haw, Mary-Ann Costello, Roger S Seymour
The hearts of smaller mammals tend to operate at higher mass-specific mechanical work rates than those of larger mammals. The ultrastructural characteristics of the heart that allow for such variation in work rate still is largely unknown. We have used perfusion-fixation, transmission electron microscopy and stereology to assess the morphology and anatomical aerobic power density of the heart as a function of body mass across six species of wild African antelope differing by approximately 20-fold in body mass...
July 11, 2018: Journal of Experimental Biology
Ninad B Kothari, Melville J Wohlgemuth, Cynthia F Moss
Echolocating bats dynamically adapt the features of their sonar calls as they approach obstacles and track targets. As insectivorous bats forage, they increase sonar call rate with decreasing prey distance, and often embedded in bat insect approach sequences are clusters of sonar sounds, termed sonar sound groups (SSGs). The bat's production of SSGs has been observed in both field and laboratory conditions, and is hypothesized to sharpen spatiotemporal sonar resolution. When insectivorous bats hunt insects, they may encounter erratically moving prey, which increases the demands on the bat's sonar imaging system...
July 11, 2018: Journal of Experimental Biology
Guido van den Thillart, Inger Wilms, Maaike Nieveen, Roy E Weber, Frans Witte
Broods of the Lake Victoria cichlid Haplochromis ishmaeli raised under hypoxic and normoxic conditions, showed striking differences in isohemoglobin (isoHb) pattern not observed in two other cichlids that do not belong to the Lake Victoria species flock (Rutjes et al , 2007). We therefore hypothesized that the adaptive mechanism seen in H. ishmaeli in response to hypoxia constitutes a trait the Lake Victoria species flock inherited from ancestors that lived in hypoxic environments. We tested this hypothesis by designing split-brood experiments with three other representative species from the same species flock: the insectivorous Haplochromis thereuterion , the mollusc shelling Platytaeniodus degeni and the zooplanktivorous Haplochromis piceatus , while keeping H...
July 11, 2018: Journal of Experimental Biology
Alexandra Khrizman, Gal Ribak, Dmitri Churilov, Irena Kolesnikov, Amatzia Genin
A major challenge faced by sessile animals that feed in the flow is to maintain effective feeding postures while enduring hydrodynamic forces. Garden eels exhibit an exceptional lifestyle: feeding on drifting zooplankton while being "anchored" in a burrow they dig in the sand. Using underwater observations, sampling and 3-D video recording, we measured the feeding rates and characterized feeding postures of garden eels under a wide range of current speeds. We show that the eels behaviorally resolve the tradeoff between adverse biomechanical forces and beneficial fluxes of food by modulating their body postures according to current speeds...
July 9, 2018: Journal of Experimental Biology
Sean Copley, Kalyanasundaram Parthasarathy, Mark A Willis
While tracking odor plumes, male hawkmoths use optic flow cues to stabilize their flight movements with respect to their environment. We studied the responses of freely flying moths tracking odor plumes in a laboratory wind tunnel and tethered moths in an optomotor flight simulator to determine the locations on the compound eye on which critical optic flow cues are detected. In these behavioral experiments, we occluded specific regions of the compound eye and systematically examined the moths' behavior for specific deficits in optic flow processing...
July 2, 2018: Journal of Experimental Biology
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