bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flight Kinematics of Black-Billed Magpies and Pigeons Over a Wide Range of Speeds
Authors: Tobalske Bret W. , Dial Kenneth P. 
Published: April 2021

ABSTRACT
To investigate how birds that differ in morphology change their wing and body movements while flying at a range of speeds, we analyzed high-speed (60 Hz) video tapes of black-billed magpies (Pica pica) flying at speeds of 4–14 m s-1 and pigeons (Columba livia) flying at 6–20 m s-1 in a wind-tunnel. Pigeons had higher wing loading and higher-aspect-ratio wings compared with magpies. Both species alternated phases of steady-speed flight with phases of acceleration and deceleration, particularly at intermediate flight speeds. The birds modulated their wingbeat kinematics among these phases and frequently exhibited non-flapping phases while decelerating. Such modulation in kinematics during forward flight is typical of magpies but not of pigeons in the wild. The behavior of the pigeons may have been a response to the reduced power costs for flight in the closed wind-tunnel relative to those for free flight at similar speeds. During steady-speed flight, wingbeat frequency did not change appreciably with increasing flight speed. Body angle relative to the horizontal, the stroke-plane angles of the wingtip and wrist relative to the horizontal and the angle describing tail spread at mid-downstroke all decreased with increasing flight speed, thereby illustrating a shift in the dominant function of wing flapping from weight support at slow speeds to positive thrust at fast speeds. Using wingbeat kinematics to infer lift production, it appeared that magpies used a vortex-ring gait during steady-speed flight at all speeds whereas pigeons used a vortex-ring gait at 6 and 8 m s-1, a transitional vortex-ring gait at 10 m s-1, and a continuous-vortex gait at faster speeds. Both species used a vortex-ring gait for acceleration and a continuous-vortex gait or a non-flapping phase for deceleration during flight at intermediate wind-tunnel speeds. Pigeons progressively flexed their wings during glides as flight speed increased but never performed bounds. Wingspan during glides in magpies did not vary with flight speed, but the percentage of bounds among non-flapping intervals increased with speed from 10 to 14 m s-1. The use of non-flapping wing postures seemed to be related to the gaits used during flapping and to the aspect ratio of the wings. We develop an ‘adverse-scaling’ hypothesis in which it is proposed that the ability to reduce metabolic and mechanical power output using flap-bounding flight at fast flight speeds is scaled negatively with body mass. This represents an alternative to the ‘fixed-gear’ hypothesis previously suggested by other authors to explain the use of intermittent flight in birds. Future comparative studies in the field would be worthwhile, especially if instantaneous flight speeds and within-wingbeat kinematics were documented; new studies in the laboratory should involve simultaneous recording of wing kinematics and aerodynamic forces on the wing.
Olfactory Responses Of A Euryhaline Fish, The Rainbow Trout: Adaptation Of Olfactory Receptors To Sea Water And Salt-Dependence Of Their Responses To Amino Acids
Authors: Shoji Takayuki , Fujita Ken-Ichi , Furihata Emiko , Kurihara Kenzo 
Published: April 2021

ABSTRACT
Salmonid fishes are able to survive in both fresh water and sea water. Concentrations of NaCl in fresh water and sea water are 0.5 and 493 mmol l-1, respectively, and, hence, salt concentrations in the medium at the olfactory epithelium are greatly changed when the fish migrate between fresh water and sea water. We used the rainbow trout, which is a salmonid fish, to examine the adaptation mechanisms of the olfactory receptors to high concentrations of salts in sea water. Application of sea water to the olfactory epithelium elicited only a very small response in the olfactory nerve, but 500 mmol l-1 NaCl elicited a large response which did not adapt to a spontaneous level with time. It is considered that the olfactory nerve becomes fatigued when the olfactory epithelium is exposed to 500 mmol l-1 NaCl for long periods. We found that the presence of 10 mmol l-1 Ca2+ in sea water inhibited the response to 500 mmol l-1 NaCl, suggesting that Ca2+ in sea water is essential for adaptation of the olfactory receptors to sea water. In the second part of the study, we examined whether the olfactory nerve responses to amino acids, potent stimulants for fish, were altered between fresh water and sea water. The magnitudes of the responses to the six amino acids examined were similar in artificial pond water and artificial sea water, indicating that a large change in NaCl concentration between fresh and sea water does not affect the olfactory nerve responses to amino acids. We used fish reared in fresh water and fish acclimated to sea water and obtained similar results. It was concluded that the tolerance of the olfactory receptors for large changes in osmotic pressure is not acquired while fish are maintained in fresh or sea water, but that the receptors of these euryhaline fish naturally provide the tolerance.
Membrane Responses Evoked By Organic Buffers In Identified Leech Neurones
Authors: Schmidt Joachim , Mangold Claudia , Deitmer Joachim W. 
Published: April 2021

ABSTRACT
Using single-electrode current-clamp and two-electrode voltage-clamp, different identified neurones of the leech (Hirudo medicinalis L.) were shown to hyperpolarize, or to exhibit outward currents (usually &gt;2 nA), during bath application of the organic buffers Mops, Pipes and Mes (10 mmol l−1). Tris and Hepes had little or no effect on the membrane properties of neurones when they were added to a bathing saline buffered by CO2–HCO3− at a constant pH of 7.4.
Outward currents evoked by buffers obtained from two suppliers, Roth and Sigma, were not significantly different, except in the case of Pipes. Steady-state currents evoked by Pipes supplied by Roth were eightfold larger than steady-state currents evoked by Pipes from Sigma. A transient current peak always present in responses evoked by Pipes from Roth was never present in responses evoked by Pipes from Sigma.
Outward currents evoked by buffers were due to a conductance increase and appeared to be carried by Cl−.
In low-Cl− saline, hyperpolarizations evoked by Mops in Retzius cells were reduced. When Cl− was injected into heart motor neurones, the hyperpolarizations evoked by Mops reversed. Tetraethylammonium (TEA+) injected into heart interneurones did not block Mops-evoked hyperpolarizations.
Mops-evoked outward currents in Retzius cells were partially blocked by d-tubocurarine and bicuculline methiodide, and the latter also partially blocked Mops-evoked hyperpolarizations in HE cells. Since d-tubocurarine partially blocked acetylcholine-evoked Cl− currents in Retzius cells and bicuculline methiodide partially blocked carbachol-evoked hyperpolarizations in HE cells, Mops appears to act on the cholinergic receptors of these neurones by mediating a Cl− conductance.
Is Mammary Output Capacity Limiting to Lactational Performance in Mice?
Authors: Hammond Kimberly A. , Lloyd K. C. Kent , Diamond Jared 
Published: April 2021

ABSTRACT
Using lactation in mice as a model, we sought to determine whether ceilings on sustained energy expenditure reside in the capacities of energy-acquiring and input organs (such as the intestine) or of energy-expending and output organs (such as the mammary glands). To distinguish between these possibilities experimentally, we surgically varied the teat number of lactating mother mice while simultaneously varying their litter size. The energy burden on each teat (i.e. the pup/teat ratio) could thus be varied independently of the energy burden (i.e. litter size) on the mother herself or on her intestine. At each teat number, pup mass proved to be maximal at intermediate litter sizes. At a given pup/teat ratio, mothers with five teats weaned pups no larger than the pups of normal (10-teat) mothers, even though the total energy burden on the former mothers was only half as large. Mothers with only two teats could not wean any pups. Litter size controlled maternal food intake, which in turn controlled intestinal mass and nutrient uptake capacity. Disproportionately high food intake for the smallest litters appears to reflect capital start-up costs of lactation. Pup mass is evidently limited by inadequate suckling stimulation of mammary glands.
Effects of Preload and Afterload on the Performance of the In Situ Perfused Portal Heart of the New Zealand Hagfish Eptatretus Cirrhatus
Authors: Johnsson Marianne , Axelsson Michael , Davison William , Forster Malcolm E. , Nilsson Stefan 
Published: April 2021

ABSTRACT
The portal heart of the New Zealand hagfish (Eptatretus cirrhatus) was perfused in situ. Stroke volume, cardiac output and power output increased in response to increased preload, in accordance with Starling’s law of the heart. A positive chronotropic effect was found when the input pressure increased from 0.05 to 0.1 kPa. Increased afterload decreased stroke volume and cardiac output. Power output peaked at an output pressure of 0.22 kPa, after which it decreased. There was no change in heart rate in response to increased afterload. In unanaesthetized resting animals, the pressure in the supraintestinal vein, which supplies the portal heart, ranged from 0.025 to 0.07 kPa (mean 0.040±0.005 kPa).
The β-adrenoceptor antagonist sotalol did not affect the response to different input and output pressures. Sotalol produced a significant decrease in heart rate and abolished the pressure-sensitive increase in heart rate. Bolus injections of adrenaline produced a transient increase in portal heart rate. The negative chronotropic response to sotalol and the response to adrenaline indicate the presence of an endogenous β-adrenergic tonus on the portal heart.
The Contribution of Nitrate Respiration to the Energy Budget of the Symbiont-Containing Clam Lucinoma Aequizonata:A Calorimetric Study
Authors: Hentschel U. , Hand S. C. , Felbeck H. 
Published: April 2021

ABSTRACT
Heat production and nitrate respiration rates were measured simultaneously in the gill tissue of Lucinoma aequizonata. This marine bivalve contains chemoautotrophic, intracellular, bacterial symbionts in its gill tissue. The symbionts show constitutive anaerobic respiration, using nitrate instead of oxygen as a terminal electron acceptor. An immediate increase in heat production was observed after the addition of nitrate to the perfusion medium of the calorimeter and this was accompanied by the appearance of nitrite in the effluent sea water. The nitrate-stimulated heat output was similar under aerobic and anaerobic conditions, which is consistent with the constitutive nature of nitrate respiration. The amount of heat released was dependent on the concentration of nitrate in the perfusion medium. At nitrate concentrations between 0.5 and 5 mmol l-1, the total heat production was increased over twofold relative to unstimulated baseline values. A mean (±S.E.M.) experimental enthalpy of -130±22.6 kJ mol−1 nitrite (N=13) was measured for this concentration range.
Two Opsins From the Compound Eye of the Crab Hemigrapsus Sanguineus
Authors: Sakamoto Katsuhiko , Hisatomi Osamu , Tokunaga Fumio , Eguchi Eisuke 
Published: April 2021

ABSTRACT
The primary structures of two opsins from the brachyuran crab Hemigrapsus sanguineus were deduced from the cDNA nucleotide sequences. Both deduced proteins were composed of 377 amino acid residues and included residues highly conserved in visual pigments of other species, and the proteins were 75 % identical to each other. The distribution of opsin transcripts in the compound eye, determined by in situ hybridization, suggested that the mRNAs of the two opsins were expressed simultaneously in all of the seven retinular cells (R1–R7) forming the main rhabdom in each ommatidium. Two different visual pigments may be present in one
photoreceptor cell in this brachyuran crab. The spectral sensitivity of the compound eye was also determined by recording the electroretinogram. The compound eye was maximally sensitive at about 480 nm. These and previous findings suggest that both opsins of this brachyuran crab produce visual pigments with maximal absorption in the blue-green region of the spectrum. Evidence is presented that crustaceans possess multiple pigment systems for vision.
Response of Cell Volume in Mytilus Gill to Acute Salinity Change
Authors: Neufeld Douglas S. , Wright Stephen H. 
Published: April 2021

ABSTRACT
The response of gill cell volume in Mytilus californianus and Mytilus trossolus (=edulis) to acute changes in salinity was assessed using three independent indicators: optical measurement of lateral cell height, measurement of intracellular water content using radiolabeled tracers and measurement of the contents of the major osmolytes of the gills. Optical measurements indicated significant variation in the response of individual lateral cells of M. californianus to acute low-salinity shock. Lateral cell height increased by approximately 20 % shortly after abrupt exposure to 60 % artificial sea water (ASW). Following this initial swelling, we estimate that a substantial regulatory volume decrease (RVD) was present in 25 % of the trials. More commonly, however, an RVD was either absent or minimal: cell height remained elevated for at least 1 h, then returned to the control height when gills were re-exposed to 100 % ASW. Changes in the combined water space of all cells in the gill, measured as the difference between total water space and extracellular space ([14 C]polyethylene glycol space), indicated that cell volume regulation in the gill as an organ was also absent or minimal. Cell water space was 2.16 ml g−1 dry mass in isolated gills of M. californianus acclimated to 100 % sea water in the laboratory and increased to 2.83 ml g−1 dry mass after a 6 min exposure to 60 % ASW. Cell water space was still 2.81 ml g−1 dry mass after 1 h in 60 % ASW and returned to 2.06 ml g−1 dry mass upon re-exposure to 100 % ASW. Consistent with these observations, the gill contents of the principal cytoplasmic osmolytes (taurine, betaine and K+ ) were unchanged (approximately 450, 250 and 230 μmol g−1 dry mass, respectively) following exposure of gills from 100 % ASW-acclimated mussels to 60 % ASW. A decrease in cell water space to 2.66 ml g−1 dry mass after 4 weeks of acclimation to 60 % ASW corresponded with a 37 % decrease in betaine content; taurine and K+ contents were unchanged. The changes in water space and solute content of gills from freshly collected M. californianus and M. trossolus were also consistent with the absence of volume regulation; cell water space remained elevated for at least 1 h after low-salinity exposure, and solute contents were unchanged after this period. We calculated the potential energetic cost of cell volume regulation for mussels exposed to 12 h of sinusoidal fluctuations between 100 % and 50 % sea water; solute uptake for full volume regulation in all tissues would cost a minimum of approximately 30 % of the standard metabolic rate during the period of salinity increase. The routine absence of substantial cell volume regulation in Mytilus gill may reflect the potentially high energetic cost of volume regulation in the face of the large and frequent salinity fluctuations that are regularly encountered by estuarine bivalves.
Adenosine Receptor Blockade and Hypoxia-Tolerance in Rainbow Trout and Pacific Hagfish: I. Effects on Anaerobic Metabolism
Authors: Bernier Nicholas J. , Harris Joelle , Lessard Joanne , Randall David J. 
Published: April 2021

ABSTRACT
The physiological properties of adenosine may be essential in the control of energy metabolism for the survival of animals exposed to oxygen shortages. Accordingly, we tested the hypothesis that adenosine modulates metabolic regulation in rainbow trout and Pacific hagfish exposed to acute hypoxia. Treatment of hypoxic rainbow trout (=3.33 or 4.00 kPa) with the adenosine receptor (AR) blocker theophylline was associated with greater increases in plasma [lactate], more rapid and pronounced metabolic acidosis, higher tissue [lactate], and lower heart creatine charge and glycogen content than in the hypoxic controls. The recruitment of anaerobic metabolism in hypoxic trout treated with enprofylline, an AR blocker with very weak affinity, was intermediate to that of the hypoxic theophylline-injected and control groups. In hagfish, plasma [lactate] increased following exposure to a of 1.33 kPa but did not increase following exposure to 3.33 kPa and, like plasma acidosis, it was greatest in the animals treated with theophylline. These findings indicate that AR blockade results in a more rapid and pronounced recruitment of anaerobic metabolism following acute hypoxic exposure, and while rainbow trout and Pacific hagfish show marked differences in their responses to hypoxia, adenosine appears to play an important protective role in both species.
Producing Directed Behaviour: Muscle Activity Patterns of the Cockroach Escape Response
Authors: Levi Rafael , Camhi Jeffrey M. 
Published: April 2021

ABSTRACT
The cockroach responds to wind from the front left by making an escape turn to the right, and vice versa. So far, no interneurones in the escape system are known that respond only to wind from the left or only to wind from the right. In this study, we used electromyographic recordings to determine whether motor neurones respond in this direction-selective manner during escape behaviour.
In the mesothoracic coxal–femoral joint, whose movement direction is diagnostic for escape direction, the fast motor neurones of one muscle respond selectively to one wind direction, and those of the antagonistic muscle respond selectively to wind from the other direction, resulting in an appropriate turning response. This rules out an alternative hypothesis, a co-activation mechanism of specifying turn direction. These results suggest that it would be fruitful to search among the interneurones of the escape system for additional cells and circuit properties that could give rise to this sharp directional discrimination.
Brain and Body Oxygen Requirements of Gnathonemus Petersii, a Fish with an Exceptionally Large Brain
Authors: Nilsson Göran E. 
Published: April 2021

ABSTRACT
Vertebrates have repeatedly been noted for having remarkably constant ratios of brain to body O2 consumption, the brain using 2–8 % of resting body O2 consumption, suggesting that evolution has put strict limits on the energetic cost of brain function. Only man, with a value of 20 %, is an exception to this rule. However, the results presented here suggest that, in the electric fish Gnathonemus petersii, the brain is responsible for approximately 60 % of body O2 consumption, a figure three times higher than that for any other vertebrate studied, including man. The exceptionally high energetic cost of the G. petersii brain appears to be a consequence both of the brain being very large and of the fish being ectothermic.
It was also found that G. petersii has a high ability to utilise O2 at low levels. Thus, during falling [O2], this species was found to maintain both its O2 uptake and its electric discharge rate down to an ambient O2 level of 0.8 mg l-1 (at 26 °C), although it was unable to tolerate an [O2] below 0.3 mg l-1. During severe hypoxia (&lt;0.8 mg l-1), G. petersii attempted to gulp air from the water surface. These results establish a new record for the energetic cost of a vertebrate brain and they show that the species possessing such a brain has a high capacity for utilising O2 at very low ambient concentrations.
Inexpensive Load Carrying by Rhinoceros Beetles
Authors: Kram Rodger 
Published: April 2021

ABSTRACT
These experiments determined the magnitude of loads that rhinoceros beetles (Scarabaeidae) can carry and also the metabolic energy required for carrying loads. I hypothesized that, like many other animals, these beetles would have metabolic rates in direct proportion to the total load (body mass plus added mass). Eight beetles (Xylorctes thestalus) walked at 1 cm s-1 on a motorized treadmill enclosed in a respirometer. The beetles could sustain this speed with loads of more than 30 times their body mass. In addition to being strong, these beetles carry loads with remarkable economy. The metabolic cost of moving a gram of additional load was more than five times cheaper than that of moving a gram of body mass. This phenomenon cannot be explained by conventional models that link the biomechanics and metabolic energy cost of locomotion.
Haemolymph Flow Distribution, Cardiac Performance and Ventilation During Moderate Walking Activity in Cancer Magister (Dana) (Decapoda, Crustacea)
Authors: Wachter Bart De , McMahon Brian R. 
Published: April 2021

ABSTRACT
Adult male Cancer magister (Dana) were equipped with pulsed-Doppler flowmeters and pressure transducers for simultaneous measurement of heart and ventilation frequencies, haemolymph flow through each of the major arterial systems and cardiac output and for calculation of stroke volume. Each variable was measured at rest and during two consecutive periods of moderate treadmill walking activity and recovery. During activity, haemolymph flow through the sternal and anterolateral arteries increased, while flow through the hepatic arterial system decreased. This resulted in a redistribution of haemolymph flow in which a proportion of cardiac output was shifted from the anterior, posterior and hepatic arterial systems to the sternal arterial system. The relative proportion of the cardiac output flowing through the anterolateral artery remained constant. This indicated that oxygen supply was shifted away from the digestive system to the muscles of the walking legs and the respiratory system. Cardiac output, heart rate and stroke volume all increased in response to activity. The increase in cardiac output is the result of a large increase in stroke volume and a small increase in heart rate. A doubling of ventilation rate also occurred during activity. Both the circulatory and ventilatory systems were restored to pre-activity values by 60 min of recovery.
Motor Corollary Discharge Activity and Sensory Responses Related to Ventilation in the Skate Vestibulolateral Cerebellum: Implications for Electrosensory Processing
Authors: Hjelmstad Gregory O. , Parks Geoffrey , Bodznick David 
Published: April 2021

ABSTRACT
The dorsal granular ridge (DGR) of the elasmobranch vestibulolateral cerebellum is the source of a parallel fiber projection to the electrosensory dorsal nucleus. We report that the DGR in Raja erinacea contains a large percentage of units with activity modulated by the animal’s own ventilation. These include propriosensory and electrosensory units, responding to either ventilatory movements or the resulting electroreceptive reafference, and an additional population of units in which activity is phase-locked to the ventilatory motor commands even in animals paralyzed to block all ventilatory movements. A principal function of processing in the dorsal nucleus is the elimination of ventilatory noise in second-order electrosensory neurons. The existence of these ventilatory motor corollary discharge units, along with other DGR units responsive to ventilatory movements, suggests that the parallel fiber projection is involved in the noise cancellation mechanisms.