bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sexual Signalling in Bladder Grasshoppers: Tactical Design for Maximizing Calling Range
Authors: Van Staaden Moira J. , Römer Heiner 
Published: April 2021

ABSTRACT
Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450 m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50 m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150 m for the male signal in the afternoon increased to 1.5–1.9 km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50 m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter-and intraspecific pressures and by the transmission channel.
The Effect Of Metamorphosis On The Repeatability Of Maximal Locomotor Performance In The Pacific Tree Frog Hyla Regilla
Authors: Watkins Timothy B. 
Published: April 2021

ABSTRACT
Measuring the repeatability of inter-individual differences in locomotor performance is an important first step in elucidating both the functional causes and the ecological consequences of performance variation. Thus, repeatability of whole-animal performance traits provides a crucial link between functional and evolutionary biology. In the present study, repeatability of maximal burst locomotor performance was estimated for a single population of the Pacific tree frog Hyla regilla.
Animals were reared individually from eggs through metamorphosis in the laboratory. Maximum burst swimming speed of tadpoles was measured before metamorphosis (Gosner stage 37) and again at the onset of the metamorphic climax (stage 42). Maximum jump distance was measured on the same individuals as juvenile frogs.
Locomotor performance was repeatable over a 24 h period for both premetamorphic tadpoles and juvenile frogs. Performance was not repeatable across metamorphosis or between any two of the three developmental stages investigated. A high-performance individual at one developmental stage does not necessarily retain that performance advantage at another stage. This lack of repeatability contrasts sharply with several previous studies on non-metamorphosing vertebrates, but concurs with a single previous study on a metamorphosing salamander. Metamorphosis appears to place strict temporal constraints on individual consistency in locomotor ability.
Vascular control in larvalXenopus laevis: the role of endothelial-derived factors
Authors: Schwerte Thorsten , Printz Eva , Fritsche Regina 
Published: April 2021

SUMMARYWe used novel digital contrasting methods to measure the effects of endothelin-1 (ET-1, 10–6 to 10–8 mol l–1), the nitric-oxide-releasing agent sodium nitroprusside (SNP, 10–2 mol l–1) and Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME, 10–4 mol l–1), a non-selective inhibitor of nitric oxide synthase, on the diameter of tiny arteries and veins of the head in anaesthetized Xenopus laevis tadpoles (stage NF 50–53). Perfusion of the main artery and vein supplying the head with ET-1 caused an immediate, significant and dose-dependent vasoconstriction. While preincubation with l-NAME caused no significant change in vessel diameter, the constriction provoked by subsequent endothelin administration was significantly enhanced. Application of SNP caused a vasodilation that was significant only after preconstriction with ET-1 (10–6 mol l–1). Our results provide strong evidence that the vasculature of developing Xenopus laevis tadpoles (NF stage 50–53) is influenced by endogenously released nitric oxide and endothelin. Vasoactive mediators released from vascular endothelial cells could be particularly important in vascular control in early embryos when the autonomic innervation is undifferentiated, poorly developed or even absent.
The archaeogastropod molluscHaliotis iris: tissue and blood metabolites and allosteric regulation of haemocyanin function
Authors: Behrens Jane W. , Elias John P. , Taylor H. Harry , Weber Roy E. 
Published: April 2021

SUMMARYWe investigated divalent cation and anaerobic end-product concentrations and the interactive effects of these substances and pH on haemocyanin oxygen-binding (Hc-O2) in the New Zealand abalone Haliotis iris. During 24 h of environmental hypoxia (emersion), d-lactate and tauropine accumulated in the foot and shell adductor muscles and in the haemolymph of the aorta, the pedal sinus and adductor muscle lacunae, whereas l-lactate was not detected. Intramuscular and haemolymph d-lactate concentrations were similar, but tauropine accumulated to much higher levels in muscle tissues. Repeated disturbance and short-term exposure to air over 3 h induced no accumulation of d- or l-lactate and no change in [Ca2+], [Mg2+], pH and O2-binding properties of the native haemolymph.The haemolymph showed a low Hc-O2 affinity, a large reverse Bohr effect and marked cooperativity. Dialysis increased Hc-O2 affinity, obliterated cooperativity and decreased the pH-sensitivity of O2 binding. Replacing Mg2+ and Ca2+ restored the native O2-binding properties and the reverse Bohr shift. l- and d-lactate exerted minor modulatory effects on O2-affinity. At in vivo concentrations of Mg2+ and Ca2+, the cooperativity is dependent largely on Mg2+, which modulates the O2 association equilibrium constants of both the high-affinity (KR) and the low-affinity (KT) states (increasing and decreasing, respectively). This allosteric mechanism contrasts with that encountered in other haemocyanins and haemoglobins. The functional properties of H. iris haemocyanin suggest that high rates of O2 delivery to the tissues are not a priority but are consistent with the provision of a large O2 reserve for facultatively anaerobic tissues during internal hypoxia associated with clamping to the substratum.
The Co-Ordination of Insect Movements
Authors: Hughes G. M. 
Published: April 2021

ABSTRACT
The effects of limb amputation and the cutting of commissures on the movements of the cockroach Blatta orientalis have been investigated with the aid of cinematography. Detailed analyses of changes in posture and rhythm of leg movements are given. It is shown that quite marked changes occur following the amputation of a single leg or the cutting of a single commissure between the thoracic ganglia. Changes following the amputation of a single leg are immediate and are such that the support normally provided by the missing leg is taken over by the two remaining legs on that side. Compensatory movements are also found in the contralateral legs. When two legs of opposite sides are amputated it has been confirmed that the diagonal sequence tends to be adopted, but this is not invariably true. Besides alterations in the rhythm which this may involve, there are again adaptive modifications in the movements of the limbs with respect to the body. When both commissures between the meso- and metathoracic ganglia are cut, the hind pair of legs fall out of rhythm with the other four legs. The observations on the effects of cutting commissures stress the importance of intersegmental pathways in co-ordination. It is shown that all modifications following the amputation of legs may be related to the altered mechanical conditions. Some of the important factors involved in normal co-ordination are discussed, and it is suggested that the altered movements would be produced by the operation of these factors under the new conditions. It is concluded that the sensory inflow to the central nervous system is of major importance in the co-ordination of normal movement.
A Neuropharmacologically Active Substance from Jellyfish Ganglia
Authors: Barnes W. J. P. , Horridge G. A. 
Published: April 2021

ABSTRACT
A substance which is extractable with acetone from the marginal ganglia of the jellyfish Aurelia causes acceleration of the rhythm of intact ganglia used as test preparations in concentrations of under 50 ganglia/ml., while higher concentrations cause inhibition. As comparable extracts of non-nervous tissue had no effect, the active substance probably originates from nervous tissue. It is distinct from sub-stances extractable from mesogloea. The RF lies near 0·85 in tert.-butanol-methanol-water (40:50:10 by vol.). The chemical nature of the acceleratory substance is unknown though it is certainly none of the known or suspected neurohumours of other organisms. The active substance has no effect on crustacean or clam hearts or upon crustacean hindgut assay preparations but it does accelerate the rhythm of a hydromedusan Phialidium.
Central Blood Pressure and Heart Output in Surfaced and Submerged Frogs
Authors: Shelton G. , Jones D. R. 
Published: April 2021

ABSTRACT
The systemic blood pressure of Rana pipiens and R. temporaria is slightly higher than the pulmocutaneous pressure at systole and much higher at diastole. The pulses differ in shape and a conus component can be seen in the systemic wave. Submersion of the animal causes a fall in systolic pressure in both arches, the diastolic pressure remaining relatively constant. The shape of the pulse wave changes, the conus component being accentuated and visible in recordings from both arches. Heart rate and stroke volume fall during submersion so that after 30 min. under water the minute volume may be 20-50% of the value at the surface. The heart becomes increasingly full of blood. The differences in systemic and pulmocutaneous pressures are explained in terms of resistance, compliance and flow in lung and body circuits. The same general relationships persist during submersion but selective increases in peripheral resistance must occur to maintain the central blood pressure in face of falling heart output.
Water balance across the cuticle of a soil insect
Authors: Galbreath R.A. 
Published: April 2021

ABSTRACT
The water regime in soil commonly approaches equilibrium of water potential with the insects living there. Even under these conditions, non-equilibrium processes have a significant effect on water movement through the cuticle of soil insects. Measurements of water potential on either side of the cuticle of Costelytra zealandica larvae showed that equilibrium is not reached while the insect is alive. There is an active outward flow of water by thermoosmosis associated with the flow of heat from the insect.
The length-tension relationship of the dorsal longitudinal muscle of a leech
Authors: Miller J.B. 
Published: April 2021

ABSTRACT
The length-tension relationship of a preparation of the dorsal body wall of the leech Haemopis sanguisuga was determined.
Passive tension is low except at very long lengths of the preparation, when it rises steeply. It is due mainly to the epidermis present in the preparation.
The active tension curve is very flat, with tension being reduced only at very short and very long lengths. This shape is explained in the context of the myofilament arrangement of the muscle fibres. It may be that thin filaments can form cross-bridges with different thick filaments at different lengths of the preparation.
The uptake of L-glutamate by the central nervous system of the cockroach, Periplaneta americana
Authors: Evans P.D. 
Published: April 2021

ABSTRACT
A concentrative uptake mechanism for L-glutamate with the following characteristics has been identified in the abdominal nerve cord :
The uptake can be divided into Na+-sensitive and Na+-insensitive components. The Na+-sensitive component showed the typical saturation kinetics of a carrier mediate process. It had a V of 15·9 × 10 −6μM/mg wet weight/min and a Km of 0·33 mm. Its magnitude was proportional to the first power of the Na+ concentration of the medium. The uptake was specific for L-di-carboxylic amino acids and was sensitive to the presence of metabolic inhibitors. The Na+-insensitive component was linearly related to the glutamate concentration of the medium.
An isosmotic saline is described for use with the isolated intact abdominal nerve cord of P. americana.
The mechanical properties of the abdominal cuticle of Rhodnius larvae
Authors: Reynolds S.E. 
Published: April 2021

ABSTRACT
The mechanical properties of loops of cuticle cut from the abdomens of 5th instar Rhodnius have been investigated. The cuticle shows pronounced viscoelastic behaviour. Stress-relaxation tests show a continuously falling modulus over a wide range of times after the imposition of a strain. Plasticized samples of cuticle show stress-relaxation curves which are shifted along the time axis towards earlier times by up to ×103. The modulus at any particular time after the imposition of strain is about 10 times lower than that of the unplasticized cuticle. It is concluded that the mechanical properties of this cuticle are determined, at least for maintained stresses, largely by the matrix material. Chitin microfibrils may act as a reinforcing filler for short-term, rapid stresses. The cuticular macromolecules are probably not extensively cross-linked by primary bonds, though secondary interactions between them are probably important in the viscoelastic properties of the cuticle. Plasticization probably involves a change in either the number or the strength of secondary interactions between the cuticle macromolecules, or both.
Studies on Locust Rectum
Authors: Spring J. H. , Phillips J. E. 
Published: April 2021

ABSTRACT
The unidirectional fluxes of 36Cl− and 22Na+ across short-circuited locust recta bathed in a simple NaCl saline were followed with time. Unidirectional fluxes and net flux of 22Na+ to the haemocoel side all remained constant for at least 4 h and were unaffected by either corpora cardiaca homogenate (CC) or cAMP. Both CC and cAMP stimulated influx and net flux of 36Cl− to the haemocoel side. Over the whole time course of the experiment, i.e. both before and after stimulation, net Cl− flux approximately equalled the shortcircuit current (Zgc). Neither CC nor cAMP caused substantial stimulation of or trans-epithelial electropotential difference (PD) if all Cl − in the bathing saline was replaced by either sulphate or nitrate or acetate. Acetate saline sustains Isc, PD and transepithalial resistance (R) at higher levels than does simple Cl-saline. Experiments with Cl-free, SO4-salines suggest that alternate electrogenic transport processes can be slowly turned on when Cl− is absent, provided a complex saline which contains several organic constituents, or simple acetate saline, is present.
The Electrical Constants of the Skeletal Muscle Fibres of the Stick Insect, Carausius Morosus
Authors: Ashcroft Frances M. 
Published: April 2021

ABSTRACT
The electrical constants of the ventral longitudinal muscle fibres of the stick insect Carausius morosus were determined by analysing the low-frequency cable properties of the fibre using short cable theory. At 20 °C in normal Ringer the membrane conductance (Gm) was 0·32 mmho.cm’, the sarcoplasmic conductivity (Gi) was 6·69 mmho/cm and the membrane capacity (Cm) was 12·2 μF/cm2. In this solution the length constant (λ) was 2·13 mm and averaged 130% of the fibre length. Hypertonic ( × 2) Ringers had no significant effect on Gt but increased the membrane conductance by about 35%. The effect of temperature on the electrical constants was also investigated: the temperature coefficient (Q10) of Gm was 1·44 and that of Gi was 1·41. The Q10 of the membrane capacity was1 ·11.
Competition Between Potassium and Rubidium Ions for Penetration of the Midgut of Hyalophora Cecropia Larvae
Authors: Zerahn Karl 
Published: April 2021

ABSTRACT
The midgut of the American silkworm transports potassium actively from blood-side to lumen (Harvey and Nedergaard 1964). The use of radiopotassium to study this process is limited by the short half-life of 42K (12·4 h). 86Rb which has a half-life of 19 days has, therefore, been used in place of potassium on the assumption that Rb and K can substitute for each other. This assumption was tested by Harvey, Haskell & Nedergaard (1968) who showed that the short-circuit current does not change significantly when all K in the bathing solution is substituted by Rb. This experiment does not, in fact, prove that the two ions compete equally. However, Nedergaard and Harvey (1968) measured the net flux of Rb and K by means of absorption spectrophotometry and found that with a K/Rb concentration ratio of 1·1 the mean K/Rb flux ratio was 1·4 (5 determinations). The difference was disregarded and the conclusion made ‘the midgut is unable to distinguish between potassium and rubidium’.
Electrical Characteristics of the Membrane of An Identified Insect Motor Neurone
Authors: Gwilliam G. F. , Burrows M. 
Published: April 2021

ABSTRACT
The electrical properties of the membrane of an identified locust motor neurone, the fast extensor tibiae in the metathoracic ganglion, have been investigated to determine : the distribution of excitable and inexcitable membrane; the impulse initiation zone; and the conduction velocity of the spike in the ganglion and in the axon. The waveform of extracellularly recorded spikes indicates that the transition from inactive to active membrane occurs along the region of the neurite which bears many arborizations within the neuropile. Measurements of the delay between orthodromically or antidromically evoked spikes, recorded at the soma and other points along the neurite, place the impulse initiating zone close to the transition between active and inactive membrane. Within the ganglion, the spike is conducted at different velocities over different parts of the neurite. The average velocity within the ganglion is, however, only about a seventh of that in the axon (0· 54 m.s-1 against 4· 1 m.s-1).
Extracellular Receptor Potentials from the Lateral-Line Organ of Xenopus Laevis
Authors: Kroese Alfons B. A. , Van Den Zalm Johan M. , Van Den Bercken Joep 
Published: April 2021

ABSTRACT
The response of the epidermal lateral-line organ of Xenopus laevis to stimulation was studied by recording extracellular receptor potentials from the hair cells in single neuromasts in isolated preparations. One neuromast was stimulated by local, sinusoidal water movements induced by a glass sphere positioned at a short distance from the neuromast. The amplitudes of the extracellular receptor potentials were proportional to the stimulus amplitude over a range of 20 dB. The phase of the extracellular receptor potentials with respect to water displacement was independent of the stimulus amplitude. With large stimulus amplitude, and stimulus frequencies between 0·5 Hz and 2 Hz, the extracellular receptor potentials, and responses of single afferent nerve fibres, showed a phase lead of 1 ·2 π radians with respect to water displacement, i.e. they were almost in phase with water acceleration. It is concluded that under conditions of stimulation with small-amplitude water movements, the hair cells respond to sensory hair displacement, whereas under conditions of stimulation with large-amplitude water movements they respond to sensory hair velocity.
The Scaling of the Thermal Inertia of Lizards
Authors: Bell C. J. 
Published: April 2021

ABSTRACT
The thermal status of an animal is the result of a combination of physical and physiological factors. In poikilotherms, it may be possible to separate these more easily than in homeotherms, where the presence of control mechanisms can mask the processes occurring. The thermal time constant of a poikilotherm has been shown to be a useful measure of its thermal behaviour, and to vary with the physiological status of the animal. A simple model is developed to show how the thermal time constant is related to the physics of heat exchange. The derived thermal time constant is shown to scale as body mass raised to the power 2/3, and this is compared with results on lizards heating and cooling in water, taken from the literature.
When heat exchange in air is considered, the concept of boundary layer resistance leads to a useful simplification. The thermal time constants in air taken from the literature show that the boundary layer resistance is approximately constant.
Dynamic Effects on the Product Distribution of the Photoreaction of s-cis-1,3-Butadiene: A Nonadiabatic Molecular Dynamics Study
Authors: Matsubara Toshiaki 
Published: April 2021

Abstract
A dynamic factor that determines the product distribution of the photochemical reaction of S2-excited s-cis-1,3-butadiene is examined using the nonadiabatic molecular dynamics method. The excited S2 state of s-cis-1,3-butadiene is relaxed via the S2/S1 and subsequent S1/S0 conical intersections (CIs). After the S1/S0-CI, several products including the trans and cis isomers, cyclobutene, bicyclobutane, and the methylenecyclopropyl diradical, are generated by six identified reaction channels. Channel 6 is another new channel leading to bicyclobutane. The ratio of each product is understood in terms of the allowed range of the ∠C–C–C–C dihedral angle at the S1/S0-CI for each product. When 2,3-dimethyl-1,3-butadiene is used instead of 1,3-butadiene, the product ratio changes because due to the dynamic effects of the Me groups the rotational motion around the central C–C bond slows down and consequently the fluctuation of the ∠C–C–C–C dihedral angle at the S1/S0-CI becomes smaller. Thus, our molecular dynamics simulations show that the fluctuation of the ∠C–C–C–C dihedral angle is an important factor to determine the product distribution.