bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Feeding Behavior in Adult Drosophila Melanogaster Varies With Feeding Regime and Nutritional State
Authors: Edgecomb Robert S. , Harth Cara E. , Schneiderman Anne M. 
Published: April 2021

ABSTRACT
The regulation of feeding behavior in adult Drosophila melanogaster includes such elements as ingestion responsiveness, volume ingested in a single meal, food storage in the crop and rate of defecation. Our results suggest that feeding behavior varies in a manner dependent on feeding regime (food-deprived or ad-libitum-fed) and nutritional state. Fed flies that are subsequently food-deprived become increasingly more responsive to food stimuli over time and, when offered 1% agar diets containing different concentrations of sucrose, ingest greater amounts of diets that have higher sucrose concentrations. When fed ad libitum for 72 h on these same diets, D. melanogaster maintained much smaller crops on average than food-deprived flies fed a single meal. Additionally, ad-libitum-fed flies are grouped into two categories depending on the concentration of sucrose in the diet. Flies fed for 72 h on 1% agar diets having 50 mmol l−1 sucrose or more are not affected by the concentration of sucrose in the diet, while flies fed on diets of 15 or 25 mmol l−1 sucrose increase ingestion responsiveness, crop size and the rate of defecation with decreasing concentrations of sucrose in the diet. Flies fed on even lower sucrose concentrations (5 or 10 mmol l−1 sucrose) for 27–72 h exhibit both a shift over time to larger crop sizes and increased mortality over those of flies fed 15 mmol l−1 sucrose. These data suggest that flies fed ad libitum are capable of modulating their feeding behavior in response to their nutritional state.
Dynamic and Static Stability in Hexapedal Runners
Authors: Ting L. H. , Blickhan R. , Full R. J. 
Published: April 2021

ABSTRACT
Stability is fundamental to the performance of terrestrial locomotion. Running cockroaches met the criteria for static stability over a wide range of speeds, yet several locomotor variables changed in a way that revealed an increase in the importance of dynamic stability as speed increased. Duty factors (the fraction of time that a leg spends on the ground relative to the stride period) decreased to 0.5 and below with an increase in speed. The duration of double support (i.e. when both tripods, or all six legs, were on the ground) decreased significantly with an increase in speed. All legs had similar touch-down phases in the tripod, but the shortest leg, the front one, lifted off before the middle and the rear leg, so that only two legs of the tripod were in contact with the ground at the highest speeds. Per cent stability margin (the shortest distance from the center of gravity to the boundaries of support, normalized to the maximum possible stability margin) decreased with increasing speed from 60% at 10 cm s−1 to values less than zero at speeds faster than 50 cm s−1, indicating instances of static instability at fast speeds. The center of mass moved rearward or posteriorly with respect to the base of support as speed increased. Moments about the center of mass, as shown by the center of pressure (the equivalent of a single ‘effective’ leg), were variable, but were balanced by opposing moments over a stride. Thus, hexapods can exploit the advantages of both static and dynamic stability. Static or quasi-static assumptions alone were insufficient to explain straight-ahead, constant-speed locomotion and may hinder discovery of behaviors that are dynamic, where kinetic energy and momentum can act as a bridge from one step to the next.
Calcium Channel Currents in Cultured Pars Intercerebralis Neurosecretory Cells of Adult Locusta Migratoria
Authors: Bickmeyer Ulf , Rössler Wolfgang , Wiegand Herbert 
Published: April 2021

ABSTRACT
The medial neurosecretory cells (MNSCs) of the pars intercerebralis in the brain of insects release various hormonal factors that control essential physiological and developmental functions such as moulting, reproduction and metabolism (Wigglesworth, 1940; Girardie, 1966; Goldsworthy, 1969), and these cells are therefore of considerable biological significance. A culture system for locust embryonic pars intercerebralis neurosecretory cells has recently been developed (Vanhems et al. 1993), and Rössler and Bickmeyer (1993) have established an in vitro system for growing larval and adult medial neurosecretory cells. Calcium plays an important role in neural physiology: neurosecretion depends on calcium influx into the cells and calcium currents carry the rising phase of action potentials in different types of insect neurones (Orchard, 1976; Pitman, 1979); calcium also mediates other ionic currents (Thomas, 1984). It is therefore of considerable interest to characterize the types of calcium channel currents found in locust neurosecretory neurones.
Underwater Swimming At Low Energetic Cost By Pygoscelid Penguins
Authors: Culik Boris M. , Wilson Rory P. , Bannasch Rudolf 
Published: April 2021

ABSTRACT
Energetic requirements of under-water swimming in pygoscelid penguins were studied in Antarctica, using respirometry together with a 21 m long swim canal and externally attached devices recording the swimming speed and dive duration of unrestrained animals. Field measurements were compared with measurements of the hydrodynamic properties of an Adélie penguin model in a circulating water tank. Minimium transport costs during underwater swimming in Adélie (Pygoscelis adeliae), chinstrap (P. antarctica) and gentoo (P. papua) penguins averaged 4.9, 3.7 and 7.6 J kg−1 m−1, respectively, at their preferred swimming speeds of 2.2, 2.4 and 1.8 m s−1, allowing the birds to dive aerobically for 110, 130 and 93 s, respectively. From the swim canal measurements, we calculated a drag coefficient (CD) of 0.0368 for a typical Adélie penguin at 2.2 m s−1. This value is significantly lower than the CDof 0.04 of an ideal spindle and the CD of 0.0496 measured on the model in the laboratory. The reasons for this difference are discussed.
The role of anion channels in osmotically activated taurine release from embryonic skate (Raja eglanteria) heart
Authors: Goldstein Leon , Davis-Amaral Erin M. , Blum Patricia C. , Luer Carl A. 
Published: April 2021

ABSTRACT
Taurine, a major osmolyte of vertebrate hearts, is released from the skate heart at increased rates during hypotonic stress. We tested the hypothesis that this taurine release is mediated by chloride channels activated by swelling. Two inhibitors of the channels, NPPB and DIDS, inhibited the volume-activated release of taurine from embryonic skate hearts. These results support the hypothesis that swelling-activated chloride channels mediate the release of cardiac taurine.
Nitrogen Excretion: Three End Products, Many Physiological Roles
Authors: Wright Patricia A. 
Published: April 2021

ABSTRACT
There are diverse physiological functions of nitrogen end products in different animal groups, including excretion, acid–base regulation, osmoregulation and buoyancy. Animals excrete a variety of nitrogen waste products, but ammonia, urea and uric acid predominate. A major factor in determining the mode of nitrogen excretion is the availability of water in the environment. Generally, aquatic animals excrete mostly ammonia, whereas terrestrial animals excrete either urea or uric acid. Ammonia, urea and uric acid are transported across cell membranes by different mechanisms corresponding to their different chemical properties in solution. Ammonia metabolism and excretion are linked to acid–base regulation in the kidney, but the role of urea and uric acid is less clear. Both invertebrates and vertebrates use nitrogen-containing organic compounds as intracellular osmolytes. In some marine invertebrates, NH4+ is sequestered in specific compartments to increase buoyancy.
Ca2+Versus Zn2+ Transport in the Gills of Freshwater Rainbow Trout and the Cost of Adaptation to Waterborne Zn2+
Authors: Hogstrand Christer , Reid Scott D. , Wood Chris M. 
Published: April 2021

ABSTRACT
Previous work suggested that Ca2+ and Zn2+ share a common uptake pathway in rainbow trout gills. We here report on relationships between the kinetic variables for unidirectional Ca2+ influx and unidirectional Zn2+ influx during a 1 month exposure of freshwater rainbow trout to Zn2+ (150 μg l-1=2.3 μmol l-1 as total zinc, Zn). Initial exposure to Zn2+ caused a large competitive inhibition of Ca2+ influx, as indicated by a threefold increase in apparent Km for Ca2+ (measured in the presence of Zn2+). There was also a smaller non-competitive inhibition (50 % decrease in Jmax) of the Ca2+ transport system, which was abolished after 1–2 weeks of exposure. The Km, measured in the absence of Zn2+, decreased dramatically (i.e. elevated affinity) on days 1–4 but increased thereafter; both true and apparent Km finally stabilized significantly above control levels. However, the Km values for Ca2+ (&lt;200 μmol l-1) were low relative to the Ca2+ level in the water (1000 μmol l-1), and therefore the changes did not influence the actual Ca2+ influx of the fish, which tracked Jmax. In contrast, water [Zn2+] (2.3 μmol l-1 as total Zn) was close to the reported apparent Km (3.7 μmol l-1) for Zn2+ influx in the presence of 1000 μmol l-1 Ca2+. Unidirectional Zn2+ influx increased during the first week of exposure to waterborne Zn2+, followed by a persistent reduction to about 50 % of control levels, effects that may be largely explained by the observed changes in true Km for Ca2+. We speculate that the initial response of the fish to elevated [Zn2+] is to compensate for a reduced availability of Ca2+ by markedly increasing the affinity of a dual Ca2+/Zn2+ transporter. Once the Ca2+ influx is ‘corrected’ by restoration of functional transport sites (Jmax), the system is tuned to limit the influx of Zn2+ by a persistent reduction in the affinities for both ions.
The changes in influx characteristics for Ca2+ and Zn2+ were correlated with internal physiological alterations indicative of adaptation to Zn2+ and increased metabolic cost. Depressed plasma [Ca] was corrected within 1 week, and there were no effects on whole-body [Ca] or [Zn]. A slight accumulation of Zn in the gills was associated with increased branchial metallothionein levels. Rates of protein synthesis and degradation in the gills were initially increased and whole-body growth was transiently impaired, effects which were reversed after 18 days of exposure. Sublethal challenge with Zn2+ (at 450 μg l-1=6.9 μmol l-1 as total Zn) always depressed plasma [Ca] in control fish, but by 1 month of exposure to Zn2+ at 150 μg l-1 (as total Zn), experimental fish were resistant to challenge. However, the fish did not acquire increased survival tolerance (LT50) to a lethal concentration of Zn2+ (4 mg l-1=61 μmol l-1 as total Zn).
Effects of Extreme pH on the Physiology of the Australian ‘Yabby’ Cherax Destructor: Acute and Chronic Changes in Haemolymph Carbon Dioxide, Acid–Base and Ionic Status
Authors: Ellis Bronwyn A. , Morris Stephen 
Published: April 2021

ABSTRACT
Freshwater habitats throughout the world are becoming increasingly threatened by the likelihood of acidification, but little consideration has been given to the importance of severe alkalization. Acute and chronic fluctuations in haemolymph acid–base status , [Na+] and [Ca2+] were monitored for up to 504 h (21 days) in the Australian freshwater crayfish Cherax destructor exposed to low- and high-pH water. The importance of carapace [Ca2+] during acid exposure was assessed. Crayfish were exposed to pH 7.1, pH 4.5 and pH 8.0 water containing calcium at 500 μmol l−1while the effect of a lower calcium concentration (50 μmol l−1) was assessed in pH 4.5 water.
Cherax in acid water containing 50 μmol l−1Ca2+exhibited a significant decrease in CO2 content after 2 h (mean decrease 1.13 mmoll−1, venous; 1.57 mmoll−1, arterial) and large ranges in throughout the treatment (2.4–7.3 mmHg). The overall acid–base response was a metabolic acidosis compensated by a respiratory alkalosis. The haemolymph Na+concentration in both control (pH 7.1, 50 μmol l−1) and acid-exposed animals in lower-Ca2+water was up to 50 % reduced compared with that in animals in pH 7.1, 500 μmol l−1Ca2+water. Ion regulatory mechanisms, causing a subsequent increase in haemolymph [Na+] after 288 h, were implicated as an important component in acid–base homeostasis. Crayfish in acid, low-Ca2+water also exhibited a 3.2 mmoll−1increase in haemolymph [Ca2+] and showed a haemolymph alkalosis compared with animals in acid water with higher [Ca2+].
At higher water [Ca2+] in pH 4.5 water (500 μmol l−1 Ca2+), the haemolymph pH of Cherax was only 0.1 unit lower than that of animals in 50 μmol l−1 Ca2+ acid water after 96 h, and both and were unchanged compared with the initial condition. As with low-Ca2+ acid-exposure, the potential haemolymph acidosis appeared largely to be compensated by respiratory alkalosis. There was a transient 31 % reduction in haemolymph [Na+], although osmolality was unchanged (control 411±7.29 mosmol kg−1). Acid–base equilibrium recovered rapidly, probably in association with changes in ion flux and the re-establishment of normal haemolymph Na+ concentration.
Alkaline-exposed Cherax destructor exhibited a mixed respiratory alkalosis and metabolic acidosis. Whereas haemolymph [Ca2+] increased by 1.8 mmol l−1 after only 1 h, haemolymph Na+ levels increased by 36 % after 2 h, possibly as part of a net H+ loss from the haemolymph. Increased HCO3−/Cl− exchange could contribute to the 4.3 mmol l−1 decrease in haemolymph CO2 level after 0.5 h of alkaline exposure. The responses of Cherax to extreme pH are different from those of the European and North American crayfish species studied to date.
The Effect of Tendon Compliance on In Vitro/In Vivo Estimations of Sarcomere Length
Authors: James Rob S. , Young Iain S. , Altringham John D. 
Published: April 2021

ABSTRACT
The errors likely to result from using excised rigor muscles to determine in vivo sarcomere length ranges were calculated for mouse extensor digitorum longus muscle (EDL). This muscle was chosen because its very long tendon makes it particularly susceptible to errors arising from tendon compliance. By placing dissected limbs into different locomotory stances, and allowing them to go into rigor, the range of sarcomere lengths over which muscles operate in vivo can be determined, but it is subject to errors due to tendon compliance. A tendon compliance of 0.24 GPa and a muscle rigor stress of 35 kPa were determined, and these were used to correct the estimates of in vivo sarcomere length, under worst case conditions. The error introduced was very small: a reduction in sarcomere length of less than 0.5 %.
Questioning Paradigms: Caste-Specific Ventilation in Harvester Ants, Messor Pergandei and M. Julianus (Hymenoptera: Formicidae)
Authors: Lighton John R. B. , Berrigan David 
Published: April 2021

ABSTRACT
Do developmental constraints in ant colonies limit gas exchange strategies to those displayed by female alates (presumptive queens)? In the xeric harvester ant genus Messor, we found that M. pergandei and M. julianus female alates ventilated highly discontinuously, as predicted, but M. julianus workers ventilated less discontinuously and M. pergandei workers (which occur in more xeric habitats) ventilated continuously. We present the salient characteristics of the discontinuous ventilation cycles of the species and the manner in which they are modulated by CO2 emission rates at a single temperature (24 °C). We demonstrate that, in M. julianus workers, open-spiracle phase CO2 emission rate only slightly exceeds overall CO2 emission rate, making discontinuous ventilation marginal, a state extrapolated in M. pergandei to continuous ventilation. However, workers are plainly capable of fargreater rates of CO2 emission than when inactive at 24 °C, so the lack of discontinuous ventilation in M. pergandei under normoxic conditions is not likely to be imposed by physiological constraints and may, in fact, be a response to its xeric environment. We hypothesize – aside from phylogenetic effects – that discontinuous ventilation occurs primarily in insects that may experience hypoxic and hypercapnic conditions, such as ant queens during claustral colony foundation and perhaps workers within the nest environment; that discontinuous ventilation is not necessarily essential to reduce respiratory water loss; and that it will not necessarily occur in castes or species routinely exposed to xeric but normoxic conditions.
Serotonin Immunoreactivity in the Ventral Nerve Cord of the Primitive Crustacean Anaspides Tasmaniae Closely Resembles that of Crayfish
Authors: Harrison Paul J. , Macmillan David L. , Young Heather M. 
Published: April 2021

ABSTRACT
Syncarid crustaceans, of which only a few living species remain, have articulated segments with well-developed appendages along the length of the body, an arrangement thought to resemble that of the earliest malacostracan crustaceans. Decapod malacostracans have fused thoracic segments and reduced abdominal appendages. Modern representatives of the two groups are separated by at least 300 million years of evolutionary history. The serotonin immunoreactivity of ganglia and connectives from the ventral nerve cord of the syncarid Anaspides tasmaniae was compared with that of serially homologous ganglia of the crayfish Cherax destructor. Both species show the serotonin-immunoreactive longitudinal fibre bundles described from other decapods and thought to be part of a neuromodulatory network. They also have in common a number of the cell bodies associated with this system. Each species has some serotonergic cells in the region examined that are not present, or that do not stain, in the other species.
The Transfer of Signals From Photoreceptor Cells to Large Second-Order Neurones in the Ocellar Visual System of the Locust Locusta Migratoria
Authors: Simmons Peter J. 
Published: April 2021

ABSTRACT
The operation of the first synapse in the ocellar pathway of the locust Locusta migratoria has been studied by making simultaneous intracellular recordings from photoreceptors and large, second-order L-neurones.
The transfer curve for the synapse, obtained by plotting the amplitudes of the initial peak responses by the two cells to pulses of light against each other, shows that L-neurones are extremely sensitive to changes in photoreceptor potential and that the connection is tonically active in darkness. Postsynaptic current in han L-neurone, produced when pulses of light are delivered from a dark background, saturates at a slightly brighter light intensity than does the postsynaptic potential. The signal-to-noise ratio improves with increases in light intensity in both cells, but the reduction in noise as signals are transmitted from photoreceptors to L-neurones is less than would be expected from the number of photoreceptors that probably converge on each L-neurone. In both cells, in the presence of different intensities of background illumination, the slope of the intensity–response curve is maintained as the curve moves along the light intensity axis. Adaptation is relatively slow so that, at least for several minutes after an increase in background illumination, both cells maintain a sustained response and the responses to stimuli of increased illumination are reduced in amplitude. During sustained background illumination, the transfer curve for the synapse between a photoreceptor and an L-neurone shifts along both axes without a change in its maximum slope. The slope of the synaptic transfer curve depends on the speed as well as the amplitude of changes in light. In response to injection of depolarising pulses of current into a photoreceptor, an L-neurone generates brief, hyperpolarising responses. The amplitude of the responses depends on the strength and speed of the depolarising stimuli. After an initial response by an L-neurone, subsequent responses are reduced in amplitude for 200 ms. 7.The amplitude of L-neurone responses to electrical stimulation of a photoreceptor increases when the hyperpolarising constant current is injected into the photoreceptor.
Speed Effects on Midline Kinematics During Steady Undulatory Swimming of Largemouth Bass, Micropterus Salmoides
Authors: Jayne Bruce C. , Lauder George V. 
Published: April 2021

ABSTRACT
We used frame-by-frame analysis of high-speed videotapes to quantify midline kinematics during steady swimming in largemouth bass at five standardized speeds (0.7, 1.2, 1.6, 2.0 and 2.4 L s−1, where L is total length). By combining morphological data from X-ray photographs with mathematical reconstructions of the midline of each fish, we determined the amplitude and timing of lateral displacement (zmax), lateral flexion (βmax) and the angle between the midline and the axis of forward travel (θmax) for each vertebral joint, the hypural bones and four equally spaced segments of the caudal fin rays. Analysis of variance revealed pervasive significant effects of both swimming speed and longitudinal location on variables describing amplitude, phase and wavelength. The amplitudes of zmax, βmax and θmax generally increased in a non-linear fashion from approximately 25%L to the tip of the caudal fin, and the greatest speed-related increases occurred between 0.7 and 1.6 L s−1. For the snout, the first caudal vertebra and the trailing edge of the caudal fin, mean values of zmax increased with speed from 0.004 to 0.012 L, from 0.005 to 0.012 L and from 0.053 to 0.066 L, respectively. For joints between the skull and the first vertebra, between the trunk and the tail vertebrae, and among the most posterior caudal vertebrae, mean values of βmax increased with speed from 1.2 to 1.7 °, from 0.6 to 0.9 ° and from 1.4 to 2.2 °, respectively. Within each swimming speed, values of βmax of the distal caudal fin commonly exceeded twice those of the proximal caudal fin. Surprisingly, at a given longitudinal location, the times of maximum lateral displacement and bending did not occur simultaneously. Instead, the phase of zmax relative to βmax was commonly shifted by more than one-sixth of a cycle. Furthermore, the phase shift between zmax and βmax changed significantly with increased swimming speed. Angles of attack of the tail structures changed periodically from negative to positive values. Maximum angles of attack of the distal caudal fin ranged from 5 to 17 °, changed significantly with swimming speed and were less than those of the hypural bones of the tail. Mean tail-beat frequency increased significantly from 2.0 to 4.2 Hz with increased swimming speed. Estimated speeds of wave propagation showed considerable longitudinal variation, and the ratio of swimming speed to posterior wave speed increased from 0.59 to 0.83 with increased swimming speed.