bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hormonal Control of Transmitter Plasticity in Insect Peptidergic Neurons: II. Steroid Control of the Up-Regulation of Bursicon Expression
Authors: Tublitz N. J. , Loi P. K. 
Published: April 2021

ABSTRACT
Each abdominal ganglion of the central nervous system of the tobacco hawkmoth, Manduca sexta, contains four individually identified lateral neurosecretory cells (LNCs) that undergo a postembryonic transmitter switch in vivo. In the embryonic and caterpillar stages, the primary LNC transmitter is cardioacceleratory peptide 2 (CAP2), a myoregulatory peptide. During metamorphosis, these cells stop expressing CAP2 and instead produce bursicon, a classic insect peptide hormone responsible for cuticular tanning. We have previously reported that this transmitter plasticity is under the control of the insect steroid hormone 20-hydroxyecdysone (20-HE), which surges twice during the last larval instar. In that report we showed that the CAP2 decline is indirectly regulated by the first 20-HE rise, the commitment pulse (CP). Here we provide evidence that the rise in bursicon levels in the LNCs is directly triggered by the second 20-HE surge, the prepupal peak (PP). We performed several experimental manipulations that exposed LNCs to the PP without the CP; cells treated in this manner exhibited a significant rise in bursicon content. In contrast, bursicon levels remained unchanged in those LNCs exposed only to the CP. Exposure to the PP triggered a precocious increase in bursicon expression in LNCs from the penultimate larval stage. Increased bursicon levels in the LNCs were also induced by direct infusion of 20-HE. Taken together, the results of these experiments suggest that the rise in bursicon in the LNCs during metamorphosis is due to the direct action of the PP on the LNCs. Thus, the two 20-HE surges combine to regulate the CAP2-to-bursicon switch in the LNCs, the first acting indirectly to cause a decline in CAP2 levels and the second triggering a rise in bursicon expression, possibly by a direct action on the LNCs.
Clock-Shift Experiments with Migratory Yellow-Faced Honeyeaters, Lichenostomus Chrysops (Meliphagidae), an Australian Day-Migrating Bird
Authors: Munro Ursula , Wiltschko Roswitha 
Published: April 2021

ABSTRACT
The behaviour of an Australian day migrant, the yellow-faced honeyeater Lichenostomus chrysops, was studied in order to assess the role of the sun in migratory orientation. During autumn migration, all tests took place under a sunny sky; birds were tested while living in the natural photoperiod (control) and with their internal clock shifted 4h fast and 4h slow. In spring, all birds were shifted 3h fast; tests in overcast conditions, with the birds relying on their magnetic compass, served as controls. In control tests in both seasons, the birds preferred directions corresponding to those observed in the wild. When tested under sunny conditions with their internal clock shifted, the birds changed their directional tendencies. However, their preferred directions were different from those expected if a time-compensating sun compass was being used. After about 6 days, the shifted birds’ directions were no longer different from the control direction. This behaviour argues against a major role of the sun compass in the orientation of day migrants. The dramatic changes of the sun’s arc with geographic latitute might cause day-migrating birds to prefer a more constant orientation cue, such as the geomagnetic field. The initial response to the clock-shift might have occurred because the birds were confused by the conflicting information from solar and magnetic cues. This suggests that the sun is usually used as a secondary cue in combination with the magnetic field.
The Effects of Seasonal Variations in Temperature on Extracellular Acid–Base Status in a Wild Population of the Crayfish Austropotamobius Pallipes
Authors: Whiteley N. M. , Taylor E. W. 
Published: April 2021

ABSTRACT
Between February 1990 and February 1991, a wild population of Austropotamobius pallipes (L.) inhabiting a large, shallow, freshwater pool in Staffordshire, central England, experienced environmental fluctuations in water temperature (1–21°C) and pH (8.2–9.5). Moulting was seasonal, with crayfish entering pre- and postmoult between May and August. Haemolymph pHa levels declined in the spring when temperatures increased from 8 to 18°C (ΔpH/Δt=−0.013pHunits°C−1). This decrease was accompanied by a fall in [HCO3− ] (of 4.12mmol l−1) and [lactate] (of 4.71mmol l−1) and a premoult elevation in to 0.59kPa. After ecdysis, when water temperatures and pH were at their maxima, pHa levels increased, they continued to increase as temperature fell in late summer, reaching 7.97 in intermoult crayfish at 13°C during September. This increase was accompanied by a decrease in to 0.22kPa at constant [HCO3−1] (5–6mmol l−1). Between September (13°C) and October (11°C) pHa fell to 7.87 with an elevation in (of 0.18kPa) and [lactate] (of 1.84mmol l−1). As temperature continued to decrease (11–1°C), pHa remained unchanged despite an elevation in [HCO3− ] by 2.4mmol l−1 at constant . A mechanism accounting for the unvarying haemolymph pH values at low temperatures is proposed, stressing the importance of temperature-related seasonal changes in CO2 solubility and measured values for pK1′ in addition to adjustments in [HCO3−] and . These were apparently unaffected by changes in collecting and holding protocols.
The Energetics of Locomotion and Load Carriage in the Desert Harvester ant Pogonomyrmex Rugosus
Authors: Lighton John R. B. , Weier Jonathon A. , Feener Donald H. 
Published: April 2021

ABSTRACT
The locomotion and load carriage energetics of the southwestern American harvester ant, Pogonomyrmex rugosus, were quantified at several temperatures within their normal foraging temperature range using a voluntary locomotion regime (‘running tube respirometer’). In a metabolic rate (MR) versus running speed regression, the intercepts for the individual ants differed significantly, so data were evaluated using analysis of covariance (ANCOVA) rather than the more common pooling of individuals. Unladen cost of transport was 158 J kg−1 m−1. The mean y-axis intercept did not differ significantly from zero after temperature-corrected standard MR (SMR) had been subtracted from MR; i.e. the y-axis intercept was not elevated above SMR. When the data were pooled, standard tests of the cost of load carriage showed that the costs of load and body carriage were statistically equivalent. However, using ANCOVA to regress MR-SMR against the product of running speed and load ratio showed that the cost of load carriage in P. rugosus is approximately 40% lower per unit mass than is the cost of body mass carriage (load ratio range 1.06–2.27). General methods are developed and described for evaluating and predicting locomotion and load carriage costs in small insects using data spanning a variety of temperatures and load ratios.
Crayfish Skeletal Muscle Requires Both Influx of External Ca2+ and Ca2+ Release from Internal Stores for Contraction
Authors: Ushio Hideki , Watabe Shugo , Iino Masamitsu 
Published: April 2021

ABSTRACT
The isometric tension and membrane potential of single skeletal muscle fibres from the flexor muscle of the carpopodite in the meropodite of crayfish Procambarus clarkii (Girard) were studied to determine whether crayfish muscle contraction requires Ca2+ release from the sarcoplasmic reticulum. Contraction elicited by brief extracellular electrical stimulation was reduced by the removal of Ca2+ or by the addition of 25 μmol l−1 nicardipine in crayfish Ringer’s solution. Addition of 30 μmol l−1 ryanodine with 1mmol l−1 caffeine induced a transient contracture, the peak tension of which was 10–30% of that of the high-K+induced contracture and which declined to the pretreatment level in 20–60min. After ryanodine–caffeine treatment, 30mmol l−1 caffeine failed to induce contraction, suggesting that intracellular Ca2+ stores had been exhausted by the treatment. Extracellular electrical stimulation also failed to induce contraction after ryanodine–caffeine treatment, although the resting potential was not changed. These results suggest that Ca2+release from the sarcoplasmic reticulum, together with Ca2+ influx via nicardipine-sensitive Ca2+ channels, is essential to the contraction of crayfish leg muscle fibres after a brief membrane depolarization.
Geomagnetic Orientation of Loggerhead Sea Turtles: Evidence for an Inclination Compass
Authors: Light Phillip , Salmon Michael , Lohmann Kenneth J. 
Published: April 2021

ABSTRACT
Recent experiments have demonstrated that hatchling loggerhead sea turtles can orient using the earth’s magnetic field. To investigate the functional characteristics of the loggerhead magnetic compass, we tested the orientation of hatchlings tethered inside a circular arena surrounded by a coil system that could be used to reverse the vertical and horizontal components of the ambient field. Hatchlings tested in darkness in the earth’s magnetic field were significantly oriented in an eastward direction. Inverting the vertical magnetic field component resulted in an approximate reversal of orientation direction, whereas reversing both the vertical and horizontal components together did not. The hatchlings failed to orient in a horizontal field of earth-strength intensity. These results provide evidence that the magnetic compass of loggerheads is an inclination (axial) compass, functionally similar to that of birds.
The Active Control of Wing Rotation by Drosophila
Authors: Dickinson Michael H. , Lehmann Fritz-Olaf , Götz Karl G. 
Published: April 2021

ABSTRACT
This paper investigates the temporal control of a fast wing rotation in flies, the ventral flip, which occurs during the transition from downstroke to upstroke. Tethered flying Drosophila actively modulate the timing of these rapid supinations during yaw responses evoked by an oscillating visual stimulus. The time difference between the two wings is controlled such that the wing on the outside of a fictive turn rotates in advance of its contralateral partner. This modulation of ventral-flip timing between the two wings is strongly coupled with changes in wing-stroke amplitude. Typically, an increase in the stroke amplitude of one wing is correlated with an advance in the timing of the ventral flip of the same wing. However, flies do display a limited ability to control these two behaviors independently, as shown by flight records in which the correlation between ventral-flip timing and stroke amplitude transiently reverses. The control of ventral-flip timing may be part of an unsteady aerodynamic mechanism that enables the fly to alter the magnitude and direction of flight forces during turning maneuvers.
The Cost of Hovering and Forward Flight in a Nectar-Feeding Bat, Glossophaga Soricina, Estimated From Aerodynamic Theory
Authors: Norberg Ulla M. , Kunz Thomas H. , Steffensen John Fleng , Winter York , Helversen Otto Von 
Published: April 2021

ABSTRACT
Energy expenditure during flight in animals can best be understood and quantified when both theoretical and empirical approaches are used concurrently. This paper examines one of four methods that we have used to estimate the cost of flight in a neotropical nectar-feeding bat Glossophaga soricina (Phyllostomidae), namely the use of kinematic and morphological data and aerodynamic theory to estimate the mechanical power requirements (power output) for hovering and horizontal forward flight. A hot-wire anemometer was used to measure induced velocity (the velocity of air accelerated by the wings) during hovering in order to estimate induced power. Our estimate of aerodynamic power (the sum of induced, profile and parasite powers) required for a 0.0105 kg G. soricina to hover is 0.15W and our estimate of the inertial power (the power required to oscillate the wings) is 0.19W. Thus, the total mechanical power for hovering is 0.34W or 32.4 W kg−1. The mechanical power required for horizontal forward flight, near the minimum power flight speed (4.2ms−1) for a 0.0117kg bat is 0.14W (12.3W kg−1), of which 0.10W is aerodynamic power and 0.042W is inertial power. Comparison with our results on metabolic power requirements estimated from nectar intake gives a mechanical efficiency of 0.15 for hovering flight and of 0.11 for forward flight near the minimum power speed.
The Locust Tegula: Significance for Flight Rhythm Generation, Wing Movement Control and Aerodynamic Force Production
Authors: Wolf Harald 
Published: April 2021

ABSTRACT
The tegula, a complex sense organ associated with the wing base of the locust, plays an important role in the generation of the flight motor pattern. Here its function in the control of wing movement and aerodynamic force production is described.
The vertical component of forewing movement was monitored while recording intracellularly from flight motoneurones during stationary flight. First, in accordance with previous electrophysiological results, stimulation of hindwing tegula afferents was found to reset the wingstroke to the elevation phase in a well-coordinated manner. Second, recordings made before and after removal of fore-and hindwing tegulae were compared. This comparison demonstrated that the delayed onset of elevator motoneurone activity caused by tegula removal is accompanied by a corresponding delay in the upstroke movement of the wings.
The consequences of this delayed upstroke for aerodynamic force production were investigated by monitoring wing movements and lift generation simultaneously. A marked decrease in net lift generation was observed following tegula removal. Recordings of wing pronation indicate that this decrease in lift is primarily due to the delayed upstroke movement – that is, to a delay of the wings near the aerodynamically unfavourable downstroke position.
It is concluded that the tegula of the locust hindwing signals to the nervous system the impending completion of the wing downstroke and allows initiation of the upstroke movement immediately after the wings have reached the lower reversal point of the wingstroke. The functional significance of tegula feedback and central rhythm generation for locust flight control are discussed.
Actions Of Vesamicol On An α-Bungarotoxin-Sensitive Neuronal Nicotinic Acetylcholine Receptor
Authors: Buckingham S. D. , Lummis S. C. R. , Balk M. L. , Schroeder M. , Sattelle D. B. 
Published: April 2021

ABSTRACT
Electrophysiology and binding studies were used to determine the actions of vesamicol [2-(4-phenylpiperidino)cyclohexanol, (AH5183)] on an α-bungarotoxin-sensitive, neuronal nicotinic acetylcholine receptor in the nervous system of the cockroach, Periplaneta americana. Electrophysiological studies on an identified motor neurone revealed a reversible blocking action of (±)-vesamicol on the response to ionophoretically applied acetylcholine with an IC50 value of 8.0×10−6 mol l−1. The block was weakly voltage-dependent over the membrane potential range of −50mV to −90mV, and appeared to be non-competitive. No difference in potency was observed between the resolved stereoisomers. (±)-Vesamicol was found to suppress specific binding of 125I-labelled αbungarotoxin to cockroach nervous tissue with an IC50 value of 5.1×10−3 mol l−1 and an estimated Hill coefficient of 0.73. Differences in the Hill coefficients were found when the resolved stereoisomers were tested separately. These data provide the first demonstration of a blocking action by vesamicol of a neuronal nicotinic acetylcholine receptor.
Glibenclamide Binding in Vertebrate Cardiac Membranes
Authors: Mckean Thomas A. , Rocklage Ann , Schneider Rudy J. 
Published: April 2021

ABSTRACT
ATP-sensitive potassium channels (KATP) were discovered by Noma (1983) in the cardiac myocyte. These channels are modulated by intracellular ATP concentration. They are usually open and leak potassium under conditions when cellular energy demand exceeds energy supply, for example during hypoxia or ischemia. They are also found in the central nervous system, smooth muscle and pancreas (Ashcroft, 1988). Their role in the control of insulin secretion has been well established (Petersen, 1990). Recent studies have shown that KATP channels are important in protecting the heart during ischemia (Grover et al. 1989; Gross and Auchampach, 1992) and during hypoxia (McKean and Branz, 1992). These channels have also been implicated in the phenomenon of preconditioning (Auchampach et al. 1992). The mechanism for cardiac protection has not been well established; however, KATP opening shortens the cardiac action potential and may limit calcium entry and reduce the metabolic demand of the myocyte (Cole et al. 1991). The channel opening is responsible for an initial extracellular accumulation of potassium that may also serve to decrease metabolic demand on the heart (Wilde et al. 1990). The open channels, however, could be detrimental to the heart during reperfusion or reoxygenation as they would facilitate re-entry phenomena and arrhythmias (Wolleben et al. 1989). Studies from this laboratory have shown that the heart of the semi-aquatic diving rodent, the muskrat (Ondatra zibethicus), is able to survive ischemia and hypoxia better than the heart of a similarly sized non-diving rodent, the guinea pig (McKean and Landon, 1982; McKean, 1984). We hypothesized that the KATP channel might be involved in the explanation for this species difference.
Segment-Specific Modulation of the Electrophysiological Activity of Leech Retzius Neurons by Acetylcholine
Authors: Szczupak Lidia , Jordan Sheryl , Kristan William B. 
Published: April 2021

ABSTRACT
The acetylcholine responses of Retzius neurons were electrophysiologically and pharmacologically characterized in situ and in culture. Single-electrode voltage-clamp was used to record currents from leech Retzius neurons from standard segments [Rz(X)] and from reproductive segments [Rz(5,6)]. A 1s pressure pulse of acetylcholine (ACh) produced a fast inward current followed by a slower outward current in Rz(X) neurons, whereas it produced only an outward current in Rz(5,6) neurons. These segment-specific responses were maintained when the two types of Retzius neurons were isolated in culture for up to 12 days. The inward current of Rz(X) reversed at around –25mV and was partially carried by Na+. This cationic current desensitized rapidly. The outward current of Rz(X) and Rz(5,6) neurons reversed at around –65mV and was carried by Cl−. This anionic current desensitized very slowly upon prolonged applications of ACh. The expression of the ACh-induced outward current in Rz(X) was season-dependent and was recorded in a larger proportion of Rz(X) neurons during the summer than during the winter. The expression of the ACh-induced outward current in Rz(5,6) did not show any seasonal pattern. The fast inward current of Rz(X) was also elicited by nicotine; it was blocked by d-tubocurarine, hexamethonium and mecamylamine, but was not affected by α-bungarotoxin. The outward current of Rz(X) and Rz(5,6) was also elicited by nicotine and by 4-[N-(3-chlorophenyl)carbamoxyloxy]2-butynyltrimethylammonium chloride (a muscarinic agonist); it was blocked by d-tubocurarine and by α-bungarotoxin, but it was not affected by hexamethonium or mecamylamine. The results show that the serotonergic Retzius neurons of the leech could be tonically inhibited by ACh. In addition, the Retzius neurons from standard segments could also be phasically excited by ACh. The receptors responsible for the excitation fit into the classification of neuronal nicotinic receptors, whereas the receptors mediating the inhibition are closer in type to the muscular nicotinic receptor.
Performance of a Butterfly in Take-Off Flight
Authors: Sunada Shigeru , Kawachi Keiji , Watanabe Isao , Azuma Akira 
Published: April 2021

ABSTRACT
The flight of a butterfly, Pieris melete, was observed in the take-off phase and was analyzed theoretically from aerodynamic and kinetic viewpoints. A vortex method, which was recently developed by the present authors, was used in this analysis.
During the downstroke, the butterfly generates mainly a vertical force. The acceleration of the butterfly’s body during the first half of the downstroke is especially large, and this acceleration is mainly caused by a large unsteady pressure drag acting on the wings. This large unsteady pressure drag is generated by the vortices shed into the flow from the outer edges of each wing of a pair; it is increased by the interference effect between a pair of wings when the opening angle is small. This force can be estimated by the previous quasi-steady analysis when the force coefficient is changed to 4. In addition to the unsteady pressure drag, an aerodynamic force due to added mass is generated and this is also increased by the interference effect between a pair of wings.
During the upstroke the butterfly generates mainly a horizontal force. The change of direction of the forces during the down- and upstrokes is controlled by variation in the inclination of the stroke plane. The moment, which is created by the aerodynamic force acting on the wings and by abdominal motion, changes the thoracic angle, that is the inclination of the stroke plane.
Collision Avoidance of Flying Locusts: Steering Torques and Behaviour
Authors: Robertson R. Meldrum , Johnson Amanda G. 
Published: April 2021

ABSTRACT
Obstacles approaching in the flight path trigger postural and wing kinematic adjustments in tethered flying locusts. We sought to confirm that these behaviours were steering behaviours by measuring the changes in the flight forces associated with their execution. We also investigated the coordination of these behaviours in the execution of collision avoidance manoeuvres and the effect of speed or size of the obstacle on the timing and magnitude of the response. Locusts were tethered and suspended in a wind tunnel from orthogonally arranged leaf springs mounted with strain gauges. Lift and yaw torque could be monitored unambiguously. We also monitored a forward translation force which combined pitch and thrust. During flight, the locusts were videotaped from behind while targets of different sizes (5cm×5 cm, 7cm×7 cm, 9cm×9cm, 11cm×11cm) were transported towards the head at different speeds (1, 2, 3 or 4 ms−). Angular asymmetry of the forewings during the downstroke with the right forewing high, and abdomen and hindleg movement to the left, were temporally associated with an increase in yaw torque to the left. With the left forewing high, abdomen and hindleg movement to the right were temporally associated with a decrease in yaw torque to the left. Obstacle avoidance behaviours could be associated with either an increase or a decrease in the pitch/thrust component. Leg, abdomen and wingbeat alterations in response to the approach of an obstacle were independent but tightly coordinated. Slower approaches increased the magnitude of the responses. However, the size of the obstacle had no effect on the magnitude of the response. Slower and larger targets generated earlier reactions (i.e. locusts reacted when the targets were further from the head). We conclude that the behaviours we have described were steering behaviours which would have directed the animal around an obstacle in its flight path, and that there were at least two strategies for collision avoidance associated with slowing or speeding flight. Leg, abdomen and wingbeat alterations formed a coherent avoidance response, the magnitude of which was dependent upon the time available for it to develop. We further conclude that the manoeuvre was not initiated at a constant time to collision and we propose that the avoidance strategy was to initiate the manoeuvre when the targets subtended more than 10° in the insect’s field of view.