bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pectoral Fin Locomotion in Batoid Fishes: Undulation Versus Oscillation
Authors: Rosenberger Lisa J. 
Published: April 2021

ABSTRACT
This study explores the dichotomy between undulatory (passing multiple waves down the fin or body) and oscillatory (flapping) locomotion by comparing the kinematics of pectoral fin locomotion in eight species of batoids (Dasyatis americana, D. sabina, D. say, D. violacea, Gymnura micrura, Raja eglanteria, Rhinobatos lentiginosus and Rhinoptera bonasus) that differ in their swimming behavior, phylogenetic position and lifestyle. The goals of this study are to describe and compare the pectoral fin locomotor behavior of the eight batoid species, to clarify how fin movements change with swimming speed for each species and to analyze critically the undulation/oscillation continuum proposed by Breder using batoids as an example. Kinematic data were recorded for each species over a range of swimming velocities (1–3 disc lengths s−1). The eight species in this study vary greatly in their swimming modes. Rhinobatos lentiginosus uses a combination of axial-based and pectoral-fin-based undulation to move forward through the water, with primary thrust generated by the tail. The pectoral fins are activated in short undulatory bursts for increasing swimming speed and for maneuvering. Raja eglanteria uses a combination of pectoral and pelvic locomotion, although only pectoral locomotion is analyzed here. The other six species use pectoral locomotion exclusively to propel themselves through the water. Dasyatis sabina and D. say have the most undulatory fins with an average of 1.3 waves per fin length, whereas Rhinoptera bonasus has the most oscillatory fin behavior with 0.4 waves per fin length. The remaining species range between these two extremes in the degree of undulation present on their fins. There is an apparent trade-off between fin-beat frequency and amplitude. Rhinoptera bonasus has the lowest frequency and the highest fin amplitude, whereas Rhinobatos lentiginosus has the highest frequency and the lowest amplitude among the eight species examined. The kinematic variables that batoids modify to change swimming velocity vary among different species. Rhinobatos lentiginosus increases its tail-beat frequency to increase swimming speed. In contrast, the four Dasyatis species increase swimming speed by increasing frequency and wavespeed, although D. americana also changes wave number. Raja eglanteria modifies its swimming velocity by changing wavespeed and wave number. Rhinoptera bonasus increases wavespeed, Gymnura micrura decreases wave number, and both Rhinoptera bonasus and Gymnura micrura increase fin-tip velocity to increase swimming velocity. Batoid species fall onto a continuum between undulation and oscillation on the basis of the number of waves present on the fins.
Choreography of song, dance and beak movements in the zebra finch (Taeniopygia guttata)
Authors: Williams Heather 
Published: April 2021

SUMMARYAs do many songbirds, zebra finches sing their learned songs while performing a courtship display that includes movements of the body, head and beak. The coordination of these display components was assessed by analyzing video recordings of courting males. All birds changed beak aperture frequently within a single song, and each individual’s pattern of beak movements was consistent from song to song. Birds that copied their father’s songs reproduced many of the changes in beak aperture associated with particular syllables. The acoustic consequences of opening the beak were increases in amplitude and peak frequency, but not in fundamental frequency, of song syllables. The change in peak frequency is consistent with the hypothesis that an open beak results in a shortened vocal tract and thus a higher resonance frequency. Dance movements (hops and changes in body or head position) were less frequent, and the distribution of dance movements within the song was not as strongly patterned as were changes in beak aperture, nor were the peaks in the distribution as strongly marked. However, the correlation between the positioning of dance movements within fathers’ and sons’ songs was striking, suggesting that the choreography of dance patterns is transmitted from tutor to pupil together with the song.A QuickTime movie of a courtship display used in this study can be found at: http://www.williams.edu/Biology/ZFinch/zfdance.html.
The effects of speed on thein vivoactivity and length of a limb muscle during the locomotion of the iguanian lizardDipsosaurus dorsalis
Authors: Nelson Frank E. , Jayne Bruce C. 
Published: April 2021

SUMMARYThe caudofemoralis muscle is the largest muscle that inserts onto the hindlimb of most ectothermic tetrapods, and previous studies hypothesize that it causes several movements that characterize the locomotion of vertebrates with a sprawling limb posture. Predicting caudofemoralis function is complicated because the muscle spans multiple joints with movements that vary with speed. Furthermore, depending on when any muscle is active relative to its change in length, its function can change from actively generating mechanical work to absorbing externally applied forces. We used synchronized electromyography, sonomicrometry and three-dimensional kinematics to determine in vivo caudofemoralis function in the desert iguana Dipsosaurus dorsalis for a wide range of speeds of locomotion from a walk to nearly maximal sprinting (50–350 cm s–1). Strain of the caudofemoralis increased with increasing tail elevation and long-axis rotation and protraction of the femur. However, knee extension only increased caudofemoralis strain when the femur was protracted. The maximum and minimum length of the caudofemoralis muscle and its average shortening velocity increased from the slowest speed up to the walk–run transition, but changed little with further increases in speed. The times of muscle shortening and lengthening were often not equal at higher locomotor speeds. Some (20–25 ms) activity occurred during lengthening of the caudofemoralis muscle before footfall. However, most caudofemoralis activity was consistent with performing positive mechanical work to flex the knee shortly after foot contact and to retract and rotate the femur throughout the propulsive phase.
Two myostatin genes are differentially expressed in myotomal muscles of the trout (Oncorhynchus mykiss)
Authors: Rescan Pierre-Yves , Jutel Ingrid , Rallière Cecile 
Published: April 2021

SUMMARY
Myostatin (GDF8) has been shown to be a major genetic determinant of skeletal muscle growth in mammals. In this study, we report the cloning of two trout cDNAs that encode two distinct myostatin-related proteins. The presence in this fish species of two myostatin genes (Tmyostatin 1 and Tmyostatin 2) probably results from the recent tetraploïdisation of the salmonid genome. A comparative reverse-transcriptase-linked polymerase chain reaction assay revealed that Tmyostatin 1 mRNA was present ubiquitously in trout tissues, while Tmyostatin 2 mRNA expression was restricted to muscle and brain. In developing muscle, Tmyostatin 1 expression was observed in eyed-stage embryos well before hatching, whereas Tmyostatin 2 was expressed only in free-swimming larvae. In myotomal muscle from adult animals, Tmyostatin 1 mRNA accumulation was similar in both slow- and fast-twitch fibres, and its concentration did not change during the muscle wasting associated with sexual maturation. In contrast, Tmyostatin 2 mRNA accumulated predominantly in slow-twitch fibres, and its concentration decreased dramatically in wasting muscles from maturing animals. This work shows that two distinct myostatin genes are present in the trout genome. Furthermore, it indicates that these two trout myostatin genes (i) exhibit a distinct expression pattern in muscle and non-muscle tissues and (ii) are not upregulated during the muscle wasting that accompanies sexual maturation.
Autonomic control of heart rate during forced activity and digestion in the snakeBoa constrictor
Authors: Wang Tobias , Taylor E. W. , Andrade Denis , Abe Augusto S. 
Published: April 2021

SUMMARYReptiles, particularly snakes, exhibit large and quantitatively similar increments in metabolic rate during muscular exercise and following a meal, when they are apparently inactive. The cardiovascular responses are similar during these two states, but the underlying autonomic control of the heart remains unknown. We describe both adrenergic and cholinergic tonus on the heart during rest, during enforced activity and during digestion (24–36 h after ingestion of 30 % of their body mass) in the snake Boa constrictor. The snakes were equipped with an arterial catheter for measurements of blood pressure and heart rate, and autonomic tonus was determined following infusion of the β-adrenergic antagonist propranolol (3 mg kg–1) and the muscarinic cholinoceptor antagonist atropine (3 mg kg–1).The mean heart rate of fasting animals at rest was 26.4±1.4 min–1, and this increased to 36.1±1.4 min–1 (means ± s.e.m.; N=8) following double autonomic block (atropine and propranolol). The calculated cholinergic and adrenergic tones were 60.1±9.3 % and 19.8±2.2 %, respectively. Heart rate increased to 61.4±1.5 min–1 during enforced activity, and this response was significantly reduced by propranolol (maximum values of 35.8±1.6 min–1), but unaffected by atropine. The cholinergic and adrenergic tones were 2.6±2.2 and 41.3±1.9 % during activity, respectively. Double autonomic block virtually abolished tachycardia associated with enforced activity (heart rate increased significantly from 36.1±1.4 to 37.6±1.3 min–1), indicating that non-adrenergic, non-cholinergic effectors are not involved in regulating heart rate during activity. Blood pressure also increased during activity.Digestion was accompanied by an increase in heart rate from 25.6±1.3 to 47.7±2.2 min–1 (N=8). In these animals, heart rate decreased to 44.2±2.7 min–1 following propranolol infusion and increased to 53.9±1.8 min–1 after infusion of atropine, resulting in small cholinergic and adrenergic tones (6.0±3.5 and 11.1±1.1 %, respectively). The heart rate of digesting snakes was 47.0±1.0 min–1 after double autonomic blockade, which is significantly higher than the value of 36.1±1.4 min–1 in double-blocked fasting animals at rest. Therefore, it appears that some other factor exerts a positive chronotropic effect during digestion, and we propose that this factor may be a circulating regulatory peptide, possibly liberated from the gastrointestinal system in response to the presence of food.
Adjusting the thermostat: the threshold induction temperature for the heat-shock response in intertidal mussels (genus Mytilus) changes as a function of thermal history
Authors: Buckley Bradley A. , Owen Marie-Eve , Hofmann Gretchen E. 
Published: April 2021

SUMMARY
Spatio-temporal variation in heat-shock gene expression gives organisms the ability to respond to changing thermal environments. The temperature at which heat-shock genes are induced, the threshold induction temperature, varies as a function of the recent thermal history of an organism. To elucidate the mechanism by which this plasticity in gene expression is achieved, we determined heat-shock protein (Hsp) induction threshold temperatures in the intertidal mussel Mytilus trossulus collected from the field in February and again in August. In a separate experiment, threshold induction temperatures, endogenous levels of both the constitutive and inducible isoforms of Hsps from the 70 kDa family and the quantity of ubiquitinated proteins (a measure of cellular protein denaturation) were measured in M. trossulus after either 6 weeks of cold acclimation in the laboratory or acclimatization to warm, summer temperatures in the field over the same period. In addition, we quantified levels of activated heat-shock transcription factor 1 (HSF1) in both groups of mussels (HSF1 inducibly transactivates all classes of Hsp genes). Lastly, we compared the temperature of HSF1 activation with the induction threshold temperature in the congeneric M. californianus. It was found that the threshold induction temperature in M. trossulus was 23°C in February and 28°C in August. This agreed with the acclimation/acclimatization experiment, in which mussels acclimated in seawater tables to a constant temperature of 10–11°C for 6 weeks displayed a threshold induction temperature of 20–23°C compared with 26–29°C for individuals that were experiencing considerably warmer body temperatures in the intertidal zone over the same period. This coincided with a significant increase in the inducible isoform of Hsp70 in warm-acclimatized individuals but no increase in the constitutive isoform or in HSF1. Levels of ubiquitin-conjugated protein were significantly higher in the field mussels than in the laboratory-acclimated individuals. Finally, the temperature of HSF1 activation in M. californianus was found to be approximately 9°C lower than the induction threshold for this species.
Swimming mechanics and behavior of the shallow-water brief squidLolliguncula brevis
Authors: Bartol Ian K. , Patterson Mark R. , Mann Roger 
Published: April 2021

SUMMARYAlthough squid are among the most versatile swimmers and rely on a unique locomotor system, little is known about the swimming mechanics and behavior of most squid, especially those that swim at low speeds in inshore waters. Shallow-water brief squid Lolliguncula brevis, ranging in size from 1.8 to 8.9 cm in dorsal mantle length (DML), were placed in flumes and videotaped, and the data were analyzed using motion-analysis equipment. Flow visualization and force measurement experiments were also performed in water tunnels. Mean critical swimming speeds (Ucrit) ranged from 15.3 to 22.8 cm s–1, and mean transition speeds (Ut; the speed above which squid swim exclusively in a tail-first orientation) varied from 9.0 to 15.3 cm s–1. At low speeds, negatively buoyant brief squid generated lift and/or improved stability by positioning the mantle and arms at high angles of attack, directing high-speed jets downwards (angles &gt;50°) and using fin activity. To reduce drag at high speeds, the squid decreased angles of attack and swam tail-first. Fin motion, which could not be characterized exclusively as drag- or lift-based propulsion, was used over 50–95 % of the sustained speed range and provided as much as 83.8 % of the vertical and 55.1 % of the horizontal thrust. Small squid (&lt;3.0 cm DML) used different swimming strategies from those of larger squid, possibly to maximize thrust benefits from vortex ring formation. Furthermore, brief squid employed various unsteady behaviors, such as manipulating funnel diameter during jetting, altering arm position and swimming in different orientations, to boost swimming performance. These results demonstrate that locomotion in slow-swimming squid is complex, involving intricate spatial and temporal interactions between the mantle, fins, arms and funnel.
Calcium currents from jellyfish striated muscle cells: preservation of phenotype, characterisation of currents and channel localisation
Authors: Lin Y.-C. James , Spencer Andrew N. 
Published: April 2021

SUMMARYWhen striated muscle cells of the jellyfish Polyorchis penicillatus were dissociated at 30°C they retained their in vivo morphology and the integrity of ionic currents. This contrasted with cells dissociated at room temperature that rarely expressed any inward currents. Whole-cell, patch-clamp recordings from dissociated muscle cells revealed that the inward component of the total ionic current consisted of only one calcium current. This calcium current activated at –70 mV, peaked at –30 mV, and inactivated within 5 ms. In comparison with barium and strontium ions, calcium ions were the preferred current carriers. Calcium channels can be blocked by dihydropyridines and nickel ions at micromolar levels. Several properties of this current are reminiscent of T-type calcium currents. Localisation of this channel using the fluorescent channel blocker fDHP and the fluorescent dye RH414 indicated that myofibres had a higher density of these channels than the somata.
Localisation of intracellular calcium stores in the striated muscles of the jellyfishPolyorchis penicillatus: possible involvement in excitation–contraction coupling
Authors: Lin Y.-C. James , Spencer Andrew N. 
Published: April 2021

SUMMARYWhen jellyfish striated muscles were stimulated directly, the amplitude of contractile tension increased as the stimulation frequency increased. Application of 10 mmol l–1 caffeine reduced the amplitude of contractile tension and abolished this facilitatory relationship, indicating that calcium stores participate in excitation–contraction coupling. Calcium stores were identified ultrastructurally using enzymatic histochemistry to localize CaATPases, and potassium dichromate to precipitate calcium. Electron energy-loss spectroscopy was used to verify the presence of calcium in precipitates. Both CaATPase and calcium were localised in membrane-bound vesicles beneath the sarcolemma. We concluded that sub-sarcolemmal vesicles could act as calcium stores and participate in excitation–contraction coupling.
Phase reversal of vibratory signals in honeycomb may assist dancing honeybees to attract their audience
Authors: Tautz J. , Casas J. , Sandeman D. 
Published: April 2021

SUMMARYForager honeybees dancing on the comb are able to attract dance-followers from distances across the comb that are too remote for tactile or visual signals to play a role. An alternative signal could be the vibrations of the comb at 200–300 Hz generated by dancing bees but which, without amplification, may not be large enough to alert remote dance-followers. We describe here, however, an unexpected property of honeycomb when it is subjected to vibration at around 200 Hz that would represent an effective amplification of the vibratory signals for remote dance-followers. We find that, at a specific distance from the origin of an imposed vibration, the walls across a single comb cell abruptly reverse the phase of their displacement and move in opposite directions to one another. Behavioural measurements show that the distance from which the majority of remote dance-followers are recruited coincides with the location of this phase-reversal phenomenon relative to the signal source. We propose that effective signal amplification by the phase-reversal phenomenon occurs when bees straddle a cell across which the phase reversal is expressed. Such a bee would be subjected to a situation in which the legs were moving towards and away from one another instead of in the same direction. In this manner, remote dance-followers could be alerted to a dancer performing in their vicinity.
The energetics of rat papillary muscles undergoing realistic strain patterns
Authors: Mellors L. J. , Barclay C. J. 
Published: April 2021

SUMMARYStudies of cardiac muscle energetics have traditionally used contraction protocols with strain patterns that bear little resemblance to those observed in vivo. This study aimed to develop a realistic strain protocol, based on published in situ measurements of contracting papillary muscles, for use with isolated preparations. The protocol included the three phases observed in intact papillary muscles: an initial isometric phase followed by isovelocity shortening and re-lengthening phases. Realistic papillary muscle dynamics were simulated in vitro (27°C) using preparations isolated from the left ventricle of adult male rats. The standard contraction protocol consisted of 40 twitches at a contraction rate of 2 Hz. Force, changes in muscle length and changes in muscle temperature were measured simultaneously. To quantify the energetic costs of contraction, work output and enthalpy output were determined, from which the maximum net mechanical efficiency could be calculated. The most notable result from these experiments was the constancy of enthalpy output per twitch, or energy cost, despite the various alterations made to the protocol. Changes in mechanical efficiency, therefore, generally reflected changes in work output per twitch. The variable that affected work output per twitch to the greatest extent was the amplitude of shortening, while changes in the duration of the initial isometric phase had little effect. Decreasing the duration of the shortening phase increased work output per twitch without altering enthalpy output per twitch. Increasing the contraction frequency from 2 to 3 Hz resulted in slight decreases in the work output per twitch and in efficiency. Using this realistic strain protocol, the maximum net mechanical efficiency of rat papillary muscles was approximately 15 %. The protocol was modified to incorporate an isometric relaxation period, thus allowing the model to simulate the main mechanical features of ventricular function.
The acoustic advantage of hunting at low heights above water: behavioural experiments on the European ‘trawling’ bats Myotis capaccinii, M. dasycneme and M. daubentonii
Authors: Siemers Björn M. , Stilz Peter , Schnitzler Hans-Ulrich 
Published: April 2021

SUMMARY
We have demonstrated in behavioural experiments that success in capturing prey from surfaces in ‘trawling Myotis’ (Leuconoë-type) depends on the acoustic properties of the surface on which the prey is presented. Two types of surface structure were ensonified with artificial bat signals to probe their acoustic characteristics. We have shown that perception of prey by echolocation is easier if the prey is presented on a smooth surface (such as calm water) than if it is presented on a structured surface (such as vegetation or the ground). This is because the smooth surface reflects a much lower level of clutter echoes than the structured one if ensonified at an angle typical for bats foraging low over water. The ensonification experiments revealed that the sound pressure level of the echo was even higher for mealworms on a smooth surface than for mealworms suspended in air. This might be because waves travelling via the surface also contribute to the echo (e.g. reflection from the surface to the mealworm, back to the surface and then to the receiver). From the behavioural experiments, we conclude that ‘trawling Myotis’ take isolated objects on smooth (water) surfaces for prey. Those objects reflect isolated, stationary acoustic glints back to the echolocating bats. Conversely, ‘trawling Myotis’ will not recognise prey if prey echoes are embedded in numerous clutter echoes. We have demonstrated marked similarities between the three European ‘trawling Myotis’ species M. dasycneme, M. daubentonii and M. capaccinii in echolocation behaviour, search image, foraging strategy and prey perception. We propose that a combination of prey abundance and acoustic advantages could have led to repeated and convergent evolution of ‘trawling’ bats in different parts of the world.
Migrating songbirds tested in computer-controlled Emlen funnels use stellar cues for a time-independent compass
Authors: Mouritsen Henrik , Larsen Ole Næsbye 
Published: April 2021

SUMMARYThis paper investigates how young pied flycatchers, Ficedula hypoleuca, and blackcaps, Sylvia atricapilla, interpret and use celestial cues. In order to record these data, we developed a computer-controlled version of the Emlen funnel, which enabled us to make detailed temporal analyses. First, we showed that the birds use a star compass. Then, we tested the birds under a stationary planetarium sky, which simulated the star pattern of the local sky at 02:35 h for 11 consecutive hours of the night, and compared the birds’ directional choices as a function of time with the predictions from five alternative stellar orientation hypotheses. The results supported the hypothesis suggesting that birds use a time-independent star compass based on learned geometrical star configurations to pinpoint the rotational point of the starry sky (north). In contrast, neither hypotheses suggesting that birds use the stars for establishing their global position and then perform true star navigation nor those suggesting the use of a time-compensated star compass were supported.