bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomechanics of Flight in Neotropical Butterflies: Aerodynamics and Mechanical Power Requirements
Authors: DUDLEY ROBERT
Published: April 2021

A quasi-steady aerodynamic analysis of forward flight was performed on 15 species of neotropical butterflies for which kinematic and morphological data were available. Mean lift coefficients required for flight typically exceeded maximum values obtained on insect wings under conditions of steady flow, thereby implicating unsteady aerodynamic mechanisms even during fast forward flight of some butterflies. The downstroke produced vertical forces on average 18% in excess of those necessary to support the body weight through the wingbeat, while the upstroke contributed minimal or negative vertical force. Estimated effective angles of incidence (αT of the wings averaged 39° during the downstroke and −22° during the upstroke; spanwise variation in αT was greater than the average difference between half-strokes. Total mechanical power requirements of forward flight averaged 12.5 W kg−1, for the case of perfect elastic storage of whig inertial energy, and 20.2 W kg−1, assuming zero elastic energy storage. Energetic costs of the erratic trajectories during forward flight increased mechanical power requirements by an average of 43%, assuming perfect elastic storage. Fluctuations in horizontal kinetic energy of the center of mass were principally responsible for this dramatic increase. When comparing different species, total mechanical power increased linearly with forward airspeed (assuming perfect elastic energy storage of inertial energy) and scaled with mass0.26 If no elastic energy storage was assumed, mechanical power was independent of airspeed and was proportional to mass0.36. Estimated metabolic rates during flight averaged 22 and 36 ml O2 g−1 h−1, for the cases of perfect and zero elastic storage, respectively.

Note: Mailing address: Smithsonian Tropical Research Institute, APO Miami, FL 34002, USA.
Characterization of an endogenous Na+/H+ antiporter in Xenopus laevis oocytes
Authors: Towle D. W. , Baksinski A. , Richard N. E. , Kordylewski M.
Published: April 2021

The amiloride-sensitive Na+/H+ antiporter in defolliculated oocytes of Xenopus laevis was characterized by measurements of 22Na+ influx and apparent H+ efflux. Uptake of 22Na+ was linear over a 90-min incubation period and was inhibited approximately 80% with 5 × 10(−4) mol l-1 amiloride. Amiloride-sensitive sodium uptake was reduced following collagenase treatment or oocyte aging. K0.5 for amiloride inhibition was 4.13 × 10(−6) +/− 1.33 × 10(−6)mol l-1 and the Km for Na+ was 4.25 × 10(−3) mol l-1. Hill analysis of the kinetic data for Na+ revealed an nH value of 1.14, indicating an absence of interacting binding sites for Na+. Parallel measurements of amiloride-sensitive Na+ uptake and H+ efflux indicated a Na+/H+ exchange ratio of 0.88:1. Our conclusion is that the Na+/H+ antiporter of Xenopus oocytes exhibits a nominal 1:1 Na+/H+ exchange stoichiometry and is similar in its properties to the antiporter of other vertebrate cells.
Acidosis (Measured by Nuclear Magnetic Resonance) and Ethanol Production in Anoxic Goldfish Acclimated to 5 and 20°C
Authors: VAN WAARDE AREN , DE GRAAFF INGRID , VAN DEN THILLART GUIDO , ERKELENS CEES
Published: April 2021

Goldfish acclimated to 20 and 5°C were subjected to anoxia (3 h at 20°C and 18 h at 5°C). The intracellular pH (pHi) and the levels of high-energy phosphate compounds in the epaxial muscle were continuously monitored by in vivo31P-n. m.r. spectroscopy. Free [ADP] was calculated from n.m.r.-measured reactants of the creatine kinase reaction and the creatine kinase equilibrium constant. A rapid initial drop in pHi was followed by a sudden decrease in the rate of development of acidosis. Similar biphasic time courses were observed for the increases in the levels of free ADP and inorganic phosphate and the decrease in phosphocreatine concentration.

In a parallel series of experiments, fish were placed in the flow cell of the n.m.r. probe (outside the magnet) and anesthetized after different anoxic intervals. Metabolites in red muscle, white muscle and blood were then assayed, using classical biochemical techniques. The transition to a less rapid decline in pH appears to be primarily due to a suppression of energy demand and activation of H+ extrusion; ethanol production becomes significant only after longer periods of anoxia. Anoxic exposure has no influence on the kinetic properties of muscle alcohol dehydrogenase, but acclimation of goldfish to low temperature increases alcohol dehydrogenase activity in white muscle.

Note: Present address: PET Center, Academic Hospital, Groningen University, PO Box 30.001, 9700RB Groningen, The Netherlands.
Metabolic Enzyme Activities, Oxygen Consumption and Glucose Utilization in Sea Raven (Hemitripterus Americanus) Erythrocytes
Authors: SEPHTON DAWN H. , LEE MACPHEE WANDA , DRIEDZIC WILLIAM R.
Published: April 2021

The organization of energy metabolism was assessed in erythrocytes of the sea raven (Hemitripterus americanus). Cell suspensions displayed a potential for aerobic glycolysis, shown by the presence of the glycolytic enzymes phosphofructokinase, aldolase and pyruvate kinase and the mitochondrial markers citrate synthase and malate dehydrogenase. Rates of oxygen uptake (Moo2) and glucose uptake Mglucose (as assessed by the disappearance of glucose) are closely matched in whole blood and resuspended erythrocyte preparations. Lactate does not accumulate under aerobic conditions. The enzymatic potential is well in excess of maximal rates of carbon flux in intact cells. Overall, the data reveal that sea raven erythrocytes have an aerobic metabolism that is fuelled by exogenous glucose. Calculated rates of glucose oxidation from [6-14C]glucose were 1000-fold lower than rates measured directly from glucose disappearance, implying that exogenous glucose is highly diluted or mixed into the intracellular pools prior to entry into the citric acid cycle.
Mechanics of Underwater Locomotion in Diving Ducks: Drag, Buoyancy and Acceleration in a Size Gradient of Specffis
Authors: LOWORN J. R. , JONES D. R. , BLAKE R. W.
Published: April 2021

1. The effects of accelerational swimming and body size on mechanical energy costs of diving were examined by comparing canvasback (Aythya valisineria Wilson), redhead (A. americana Eyton) and lesser scaup (A. affinis Eyton) ducks (mean body mass 1.275, 1.013 and 0.817kg, respectively) in steady versus unsteady models of locomotion. Steady models assume constant speed, whereas unsteady models incorporate acceleration and deceleration with each propulsive stroke. 2. The surface areas of the ducks increased linearly with body mass (r2=0.96), with all species falling on the same curve. 3. Body drag D of frozen ducks towed under water increased with body mass M and speed U according to the relationship D = −0.946+0.826M+0.614U+0.825U2, r2=0.95. 4. In kinematic analyses, regression curves of percentage of total stroke distance versus percentage of stroke duration did not vary within individuals, sometimes varied between individuals and always varied between species. In diving ducks, analyses of a single sequence per individual and several individuals per species will usually provide an accurate kinematic description for the species. 5. The degree of acceleration and deceleration during a stroke increased with decreasing body size among species. 6. The power phase lasted for 66–70% of stroke duration, and the ducks accelerated for the first 84% of this phase. During the power phase, work against drag was 10–12%, work against buoyancy was 36–38%, and inertial work in acceleration was 49–54° of the total mechanical work done. 7. Mechanical energy costs of descent, as estimated by the unsteady model, were 47–75% higher than estimates from the steady model. Accelerational stroking had greater effects on descent costs as body size decreased.

Note:

Present address: Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA.
Gill Movements of Nymphal Ephemera Danica (Ephemeroptera) and the Water Currents Caused by them
Authors: Eastham L. E. S.
Published: April 2021

The nymphs of Ephemera danica living in burrows in the sandy mud of flowing waters present a problem of current production in the water, quite different from those so far investigated (Eastham, 1932, 1934, 1936, 1937)-Percival & Whitehead (1926) collected data indicating that this species is found most commonly in water, flowing over a sandy floor, which contains about 65% coarse sand, 2% fine sand and about 1 % each of silt, fine silt and clay. Their observations also showed that from this type of environment there was little or no migration to neighbouring places where the sand was present in smaller amount and the silt and clay predominated. Experiments showed that the animals always displayed a preference for the soft surface into which burrowing could be effected, but no adequate explanation of the relationship between nymphs and sand was forthcoming. Questions regarding the unsuitability of silt or clay, in any but small quantities, remain unanswered.
Studies on the Growth of Tissues in Vitro
Authors: Trowell O. A. , Willmer E. N.
Published: April 2021

Tissue extracts have been made from several organs of growing and adult fowls, and the growth-promoting properties of these extracts have been tested on periosteal fibroblasts growing in vitro. The growth-promoting properties are most pronounced in brain extract and diminish in the sequence : thyroid, thymus, testis, ovary, bone marrow, liver, kidney and muscle extracts. Extracts made from the spleens of adult cocks were found to be far more efficient growth-promoting agents than extracts made from the spleens of young birds. The growth-promoting power of a tissue extract cannot always be correlated with the age of the tissue from which the extract was made, with the rate of growth of that tissue, nor with its nuclear content.
A Quantitative Study of Amphibian Neural Tube Induction with A Water-Soluble Hydrocarbon
Authors: Shen S. C.
Published: April 2021

The water-soluble carcinogenic hydrocarbon, 1 : 2 : 5 : 6-dibenzanthracene-α-β-endo-succinate, has been implanted in carefully graded doses into gastrulae of Triton alpestris. An optimal dose for neural tube formation was found at 0·0125γ per embryo, and for palisade inductions at 0·000125γ per embryo. It is suggested that the action of this hydrocarbon at least is direct, imitating the action of the naturally occurring organizer substance, and not indirect, by injuring the ventral ectoderm so as to liberate the masked organizer substance which it contains. The effective range of dosage resembles that of many biologically active substances. A parallelism exists between the frequency and the size of the neural tube inductions.
The Sodium and Potassium Content of Sea Water
Authors: Webb D. A.
Published: April 2021

The sodium and potassium content of sea water have been re-determined. The following values are suggested: K/Cl = 0·02009 ± 00002 ; Na/Cl = 0·5549 ±0·001.
The Motor Mechanism of the Insect Leg
Authors: Pringle J. W. S.
Published: April 2021

A double motor innervation is described from an insect muscle, the two nerve fibres producing respectively a tonic contraction and a twitch. No evidence has been found for the existence of inhibitory fibres. The nature of the two types of contraction is discussed, and compared with the similar double motor innervation of some Crustacean muscles. The distribution of motor fibres to the muscles of the metathoracic leg of Periplaneta is described in detail. The method of utilization of the leg in normal life is discussed.
Antagonism between Salts of the Heavy and Alkaline-Earth Metals in their Toxic Action on the Tadpole of the Toad,Bufo Bufo Bufo(L.)
Authors: Jones J. R. Erichsen
Published: April 2021

A brief review is given of the various types of living material and of toxic substances employed by different workers in the study of antagonism. Survival curves are described for the heavy metal salts nickel nitrate, copper nitrate and cadmium nitrate, and the alkaline-earth metal salts magnesium, calcium, strontium and barium nitrate, for the tadpole of the toad, Bufo bufo bufo (L.). A description is given of Osterhout’s method for the detection and measure-ment of antagonism by observing the effect of mixing, in varying proportions, equally toxic solutions of the two substances in question. Survival curves for tadpoles in mixtures of equally toxic solutions of nickel nitrate and strontium nitrate indicate marked antagonistic action between these salts, the effect increasing with dilution. The survival curve for mixtures of the equally toxic solutions 0·03 N copper nitrate and 0·40N strontium nitrate apparently indicate antagonism over a part of the concentration range and synergism over the remainder. This is because a 0·03 N solution of copper nitrate increases in toxicity upon dilution, its toxicity reaching a maximum at approximately 0·0015N. If the normality of the copper solution is below this critical value its mixture with an equally toxic strontium solution gives a normal antagonism curve. It is shown that the other alkaline-earth metals, calcium, magnesium and barium also reduce the toxicity of copper solutions. The strontium concentration— copper concentration—survival time relationship is studied in detail and the way in which the survival time locus is represented by a curved surface is described. The survival surfaces for copper and calcium, copper and magnesium and copper and barium are of similar type. Problems for further investigation arising out of the results are briefly discussed.
Calcium And Calmodulin Antagonists Delay Oral Regeneration In The Ciliate Stentor Coeruleus
Authors: Maloney Michael S. , Walsh Patricia R. , Rhoadarmer Kelly B.
Published: April 2021

The regeneration of a new oral apparatus in Stentor coeruleus (oral regeneration) has been shown to be sensitive to events that inhibit calcium uptake and calmodulin function. Removal of extracellular calcium delays oral regeneration significantly. The calcium channel antagonist verapamil also delays oral regeneration, as does lanthanum, which is known to block calcium uptake. Both inhibitors are active in the concentration range 10−7-10−6 mol l−1. Verapamil acts primarily in the earliest stages of regeneration (prior to stage 5) though some minor delays occur in the later stages as well. In addition, verapamil caused an apparent ‘clumping’ of the pigment granules in the interior of the cell similar to the effects of high concentrations of theophylline and caffeine. The effects of verapamil on oral regeneration were not reversible in the presence of excess extracellular calcium but those of lanthanum were. The calmodulin antagonists trifluoperazine and W-7 were also shown to delay oral regeneration, but the dechlorinated analogue of W-7, W-5, had no effect even at concentrations 10 times those of W-7. The effects of W-7 were not reversed by excess extracellular calcium. These results suggest that calcium uptake is necessary for oral regeneration and that calmodulin is involved in the control and/or formation of the oral apparatus.
The Role of Suction in the Adhesion of Limpets
Authors: Smith Andrew M.
Published: April 2021

Experiments were performed to determine the mechanism by which limpets attach to the substratum. Pressure measurements were made under the feet of three species of limpets as they were forcibly detached from the substratum. These measurements show that limpets actively decrease the pressure under their feet, and in almost every case this pressure decrease can account for all of their tenacity. The results are the same whether the pressure transducer is flush with the surface or connected to the surface via a tube. The tenacity of limpets is dependent on ambient pressure, as predicted for a suction mechanism. Leaks disrupt the attachment of limpets. Thus, for at least an hour after they have been moving, suction appears to be the primary attachment mechanism of limpets. Limpets using suction often have tenacities greater than 0.1 MN m−2, which corresponds to pressures under the foot lower than 0MPa.

If limpets have more than a few hours to attach, approximately 30% of them form a different, stronger attachment that appears to be based on glue. These limpets remain stationary for extended periods. It is hypothesized that limpets in the field alternate between the use of suction and glue, depending on their need for mobility.
Acid-Base Regulation in the Atlantic Hagfish Myxine Glutinosa
Authors: Mcdonald D. G. , Cavdek V. , Calvert L. , Milligan C. L.
Published: April 2021

Blood acid-base status and net transfers of acidic equivalents to the external environment were studied in hagfish, Myxine glutinosa, infused with ammonium sulphate (4mequivkg−1 NFL+) or with sulphuric acid (3mequivkg−1 H+). Hagfish extracellular fluids (ECF) play a greater role in acid-base regulation than in teleosts. This is because hagfish have a much larger blood volume relative to teleosts, despite a relatively low blood buffering capacity. Consequently, infusion of ammonium sulphate produced only half of the acidosis produced in marine teleosts in comparable studies, and hagfish readily tolerated a threefold greater direct H+ load. Furthermore, the H+ load was largely retained and buffered in the extracellular space. Despite smaller acid-base disturbances, rates of net H+ excretion to the external environment were, nonetheless, comparable to those of marine teleosts, and net acid excretion persisted until blood acid-base disturbances were corrected. We conclude that the gills of the hagfish are at least as competent for acid-base regulation as those of marine teleosts. The nature of the H+ excretion mechanism is discussed.
A Novel Type of Ciliary Activity in Stylonychia Mytilus: Analysis of Potential-Coupled Motor Responses in the Transverse Cirri
Authors: Mogami Yoshihiro , Machemer Hans
Published: April 2021

The motor responses of the transverse cirri of Stylonychia mytilus were investigated by applying high-speed microcinematography and step voltageclamp. As a response to hyperpolarization, the transverse cirri began to swing posteriorly from an inactive upright posture at rest. The deeply inclined posture was maintained as long as the hyperpolarizing pulse was on. Upon depolarization, the cirri began to swing towards the anterior end of the cell and continued regular cyclic beating, orienting the effective stroke anteriorly. Motor responses of the transverse cirri occurred in quasi-planar motion, allowing analysis of the bend configuration along the full length of the cirri. Beating activity induced during sustained depolarization was virtually stable, with different oscillation profiles at base and tip. Cyclic movement of the distal region was enhanced at large amplitudes of depolarization. Termination of a hyperpolarizing voltage step induced a transient depolarization-type anterior beating, and termination of a depolarizing step induced a transient posteriad inclination of the transverse cirri. In both hyperpolarization- and depolarization-induced motor responses, a shear angle analysis of the initiation of the response indicated that sliding displacement of doublet microtubules was initiated at the base and propagated towards the tip. The discovery in a ciliary organelle of a very distinct response to hyperpolarizing and depolarizing stimulation is highly useful for the analysis of ciliary electromotor coupling. The functions of intraciliary Ca2+ in the regulation of the motor responses are discussed.
Activation Of A Peptidergic Synapse Locally Modulates Postsynaptic Calcium Influx
Authors: Richmond J. E. , Funte L. R. , Smith W. L. , Price D. A. , Haydon P. G.
Published: April 2021

We examined the synaptic connection between Phe-Met-Arg-Phe-NH2 (FMRFamide)-immunoreactive neurone VD4 and its target neurone Pl, both found in the central nervous system of the pond snail Helisoma trivolvis. The major FMRFamide-like peak in neurone VD4 appears to be FMRFamide itself, based on its high performance liquid chromatography (HPLC) elution time and immunoreactivity before and after oxidation, but small peaks are also present at the elution times of Phe-Leu-Arg-Phe-NH2 (FLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide).

The modulatory actions of the neuropeptides found in neurone VD4 were tested on the postsynaptic target cell Pl. Bath application of both the tetrapeptides FMRFamide and FLRFamide at a concentration of 10−5 mol l−1 reduced the macroscopic voltage-sensitive calcium current of neurone Pl in culture; FMRFamide by 45% and FLRFamide by 51%. Bath application of the heptapeptide GDPFLRFamide (10−5 mol l−1) reduced the calcium current by only 8%.

We reconstructed the synaptic connection between VD4 and Pl in culture. Action-potential-evoked calcium transients in neurites growing from Pl cells in culture were monitored using Fura-2. Addition of FMRFamide, FLRFamide or GDPFLRFamide reduced the magnitude of the calcium transient in Pl. Stimulation of VD4 mimicked the effects of peptide application and caused localized reductions in the action-potential-evoked calcium transients in Pl at the points of contact between the neurites of neurones VD4 and Pl. These results suggest that neurone VD4 modulates the calcium influx of neurone Pl through the release of endogenous FMRFamide-related peptides and that this modulatory action is restricted to sites of synaptic interaction.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: VII. The Branchial Chamber and its Role in Urine Reprocessing
Authors: Morris S. , Taylor H. H. , Greenaway P.
Published: April 2021

The branchial chambers of the terrestrial anomuran Birgus latro L. were examined as potential sites for urine reprocessing. The antennal glands opened at the bases of the second antennae within the anterior extension of the branchial chambers. The adjacent mouth parts and scaphognathites and the cuticle lining the ventral folds of the branchiostegite bear hydrophilic hairs. The hairs retained urine in the branchial chamber and conducted it to either the gills or the mouth. Irrigation of the branchial chambers with artificial urine demonstrated the strong net uptakes of Na+ and Cl− to be similar at approximately 4.5 μmolh−1g−1 from full-strength urine, diluting the fluid to a threshold below 20 mmol l−1.

Na+/K+-ATPase and Ca2+-ATPase activities of gill homogenates indicated Vmax values (65–127 and 11 nmol min−1 mg−1 protein, respectively) similar to those of marine species but low Km values (sodium Km=0.2–2.4mmoll−1, potassium Km=0.03–0.2mmoll−1, calcium Km=4–9 μmol l−1), which are more characteristic of freshwater species. The gills are considered to be a site of ion reclamation from the urine and this is achieved by specific morphological, biochemical and behavioural adaptations.
The Olfactory Memory of the Honeybee Apis Mellifera: I. Odorant Modulation of Short- and Intermediate-Term Memory After Single-Trial Conditioning
Authors: Smith Brian H.
Published: April 2021

In the first 15 min after a single learning trial the olfactory memory of the honeybee, Apis mellifera, proceeds through different processing phases during which time the memory is differentially sensitive to a cooling treatment that causes amnesia. During learning about floral odours in a natural situation, several decisions would normally be made about floral choice within that period. In order to study these phenomena in more detail, single-trial proboscis extension conditioning to different odorants was used. Several stimulus-specific effects on memory consolidation in the honeybee are shown. From previous experiments it was predicted that certain odorants would be more salient conditioning stimuli. This result is confirmed. Second, generalization from the conditioned odorant to a different odorant depends on the conditioned odorant and the time postconditioning. In some combinations, responses to a novel odorant are significantly stronger than responses to the conditioning odorant after memory consolidation. These data indicate that memory recall in the honeybee, as it is evidenced by proboscis extension, is sensitive to several aspects of stimulus identity and presentation. The acquisition and recall processes are therefore much more dynamic processes than realized previously.
Electrosensory Frequency and Intensity Discrimination in the Wave-Type Electric Fish Eigenmannia
Authors: Kramer Bernd , Kaunzinger Ivo
Published: April 2021

Eigenmannia’s frequency and intensity discrimination thresholds were determined for a range of seven frequencies (50–1700Hz), centered on a fish’s individual discharge frequency, using a conditioned go/no-go paradigm. The threshold criterion was ‘50% correct choices’ (of the rewarded stimulus, S+, over the unrewarded stimulus, S−); this was validated by testing for statistically significantly shorter response latencies for the S+ compared with the S− stimulus.

The stimuli consisted of sine wave bursts presented for up to 20 s, repeated at 2 s−1 (rise and fall times of an individual burst, 50 ms; holding time, 250 ms; silence, 150ms). When testing for frequency discrimination, the sine wave bursts alternated in frequency (Δf); for intensity discrimination, every other sine wave burst was of increased intensity (ΔI). The reference stimulus intensity was 30 dB with reference to a fish’s individual absolute threshold for a continuous sine wave at that frequency, previously determined using a conditioned go response.

Sensory discrimination was best close to a fish’s individual discharge frequency. At 30 dB sensation level, fish discriminated frequency differences as small as 0.52 Hz (0.60 and 0.79 Hz in two other individuals) and intensity differences as small as 0.56dB (1 dB in two other fish).

At stimulus frequencies different from a fish’s discharge frequency, Eigenmannia’s frequency discrimination declined at lower frequencies at a rate of up to 1 Hz octave−1, and at higher frequencies at a rate of up to 3 Hz octave−1. For Eigenmannia’s intensity discrimination a similar loss was observed: at frequencies lower than a fish’s discharge frequency, intensity discrimination thresholds rose at a rate of less than 1 dB octave−1, while the rate was below 2 dB octave−1 for higher frequencies.

Compared with other acoustico-lateral senses in lower vertebrates, Eigenmannia’s electrosensory frequency and intensity discrimination is unusually high, in the range of that known for audition in the most sensitive higher vertebrates with a cochlea (for example, human). This emphasizes Eigenmannia’s specialized ‘active’ electrosensory system, which detects the presence of a stimulus field as the modulation of a fish’s own ‘carrier’ signal in amplitude and phase (beat analysis), as opposed to ‘passive’ sensory systems, which must deal with unpredictable signals from the environment as they occur.
How Stimulus Direction Determines the Trajectory of the Mauthner-Inthated Escape Response in a Teleost Fish
Authors: Eaton Robert C. , Emberley Deanna S.
Published: April 2021

Fishes use the Mauthner-initiated C-start for short-latency evasion of predators. C-starts consist of a sudden turn (stage 1) and a rapid acceleration (stage 2). We analyzed high-speed ciné films of goldfish C-starts elicited by dropping a ball into the water. It was previously thought that stage 1 angle does not vary concomitantly with the angle of the threatening stimulus relative to the position of the fish. We found, however, a significant inverse relationship between the direction of the impact of the ball and the angle turned by the end of stage 1. When starting near a wall, or when its usual trajectory was blocked by a wall, the fish used an escape route that was not predictable from the stimulus angle. The fish did not appear to correct its trajectory if it began to turn towards the ball. This behavioral evidence supports the previous notion that the underlying neural command is ballistic and does not use sensory information from the stimulus once the movement begins. If this is so, the fish probably utilizes information on obstacle location in the interval leading up to the trigger stimulus.
Vortex Formation in the Tethered Flight of the Peacock Butterfly Inachis IO L. (Lepidoptera, Nymphalidae) and Some Aspects of Insect Flight Evolution
Authors: Brodsky A. K.
Published: April 2021

High-speed filming has been used to investigate the performance of the peacock butterfly Inachis io while flying in a wind-tunnel. The wake of the butterfly in ‘feeding’ flight is a system of discrete pairs of vortex rings: in each pair the vortex rings are coupled at right angles. The flow distribution around the butterfly and the dynamics of the vortex rings suggest that useful force is produced continuously throughout the wingbeat. The butterfly’s flapping flight can be divided into three successive stages: during the downstroke, force generation can be explained by quasi-steady aerofoil action; during the upstroke and supination, by unsteady aerofoil action; and during pronation, by a jet mechanism.

The study of airflow around the peacock butterfly throws light on the evolutionary changes in the pattern of interaction between insect wings and the air. At the first stage of the evolution of insect flight, documented in a subimago of the mayfly Heptagenia sulphurea and some other primitive insects, flapping wings generate a system of coupled vortex rings; the aerodynamic force, being perpendicular to the stroke plane, coincides with the direction of the longitudinal body axis. At the second stage, this force is directed forwards and upwards relative to the body axis; the vortex wake is the same as that at the first stage. From this point, two paths of evolution are possible. The first leads to the vortex pattern recorded in the peacock butterfly. The second is typically found in higher orders, where the narrow and relatively short wings flap with lower amplitude and higher frequency, leaving in their wake two chains of uncoupled small vortex rings.
Behavioral Responses to Chemical Stimulation of the Olfactory Organ in the Squid Loligo Opalescens
Authors: Gilly Wm F. , Lucero Mary T.
Published: April 2021

Behavioral experiments were carried out on restrained, but otherwise fully active, squid to test the chemoreceptive capabilities of the olfactory organ. Specific chemical substances stimulated high-pressure jet escape responses when ejected from a small pipette into the area immediately around the olfactory organ. These included squid ink and L-Dopa (3,4 dihydroxyphenylalanine) as well as agents that block voltage-dependent potassium channels, such as quaternary ammonium ions and 4-aminopyridine. Experiments designed to map chemosensitivity spatially identified the olfactory organ as the receptive site. Unilateral application of a topical local anesthetic to an olfactory organ selectively and reversibly abolished responsiveness on the treated side only. The olfactory organ can thus mediate detection of water-borne chemicals. This detection, in turn, is linked to motor control pathways involved in initiating escape-jetting behavior.
The Ionic Basis of the Receptor Potential of Frog Taste Cells Induced by Sugar Stimuli
Authors: Okada Yukio , Miyamoto Takenori , Sato Toshihide
Published: April 2021

The ionic mechanism underlying the receptor potential in frog taste cells induced by sugar stimuli was studied with conventional microelectrodes by replacing the superficial and interstitial fluids of the tongue with modified solutions. The taste cell generated a depolarizing receptor potential accompanying a remarkable reduction of input resistance in response to stimulation with galactose and sucrose. The magnitude of the receptor potential in response to galactose solution increased linearly with decreasing pH in the pH range 6-8, but remained constant above pH 8. The reversal potential was increased by only 29 mV by a 10-fold increase in the H+ concentration of the stimulus, suggesting that there are pH-dependent and pH-independent components in the mechanism generating the receptor potential. The use of Na+-free, Ca2+-free and K+-free interstitial fluids did not affect the receptor potential, but the elimination of Cl- from the interstitial fluid largely abolished it. Interstitial 0.1 mmol 1-1N,N’-dicyclohexyl-carbodiimide (DCCD) completely inhibited the receptor potential and interstitial 0.1 mmol 1-1 N-ethylmaleimide (NEM) decreased the potential to 40% of the control value. Lowering the pH of interstitial fluid from 7.2 to 6.3 decreased the receptor potential to 30 % of the control value. It is concluded that part of the receptor potential in frog taste cells induced by sugar stimuli may be produced by an inflow of H+ through the taste-receptive membrane. The intracellular pH of the taste cell may be regulated by a Cl--dependent H+ pump in the basolateral membrane.
Dietary Selection Behaviour in Spodoptera Littoralis: The Effects of Conditioning Diet and Conditioning Period on Neural Responsiveness and Selection Behaviour
Authors: Simmonds M. S. J. , Simpson S. J. , Blaney W. M.
Published: April 2021

This paper forms part of our study of the behavioural and neural mechanisms involved in dietary selection behaviour of larvae of the polyphagous noctuid Spodoptera littoralis (Boisduval). Larvae were conditioned on one of four chemically defined artificial diets for 4, 8 or 12 h. Diets differed in their proportions of protein and digestible carbohydrate: the PC diet contained 20% protein and 10% carbohydrate; the P diet contained 20 % protein but the 10 % carbohydrate was replaced by indigestible cellulose; the C diet contained 10% digestible carbohydrate and the protein was replaced by cellulose, and the 0 diet lacked both protein and carbohydrate. After conditioning, the larvae were exposed to either behavioural or electro-physiological experiments. In the behavioural choice experiment, larvae were provided with both P and C diets for 9 h. The conditioning diets P and 0 influenced which of the two choice diets was first contacted; significantly higher proportions of the larvae conditioned on the P diet initially contacted the C choice diet and significantly higher proportions of larvae conditioned on the 0 diet initially contacted the P choice diet. Larvae fed on the diet they first contacted and the probability of stopping the first meal was greater when that diet was P, regardless of the conditioning diet. The duration of the first meal on the C choice diet was significantly longer for larvae conditioned on diets lacking digestible carbohydrate (P and 0) than for those conditioned on either PC or C diets. Larvae were observed to compensate for a deficiency in protein by increasing the frequency of feeding contacts with the P choice diet but not the duration of these contacts. To compensate for a deficiency in digestible carbohydrate, the larvae increased the duration of their feeding contacts with the C choice diet. In the electrophysiological experiment, the maxillary styloconic sensilla were stimulated with an amino acid mixture and sucrose. Neural responses were recorded from two groups of larvae, one after they had been conditioned on one of the four diets for 4, 8 or 12 h and the other after they had subsequently been exposed to the choice diets for 9h. Larvae in the first group that had been conditioned on diets lacking sucrose (P and 0) were more responsive to sucrose than larvae conditioned on diets containing sucrose (PC and C). The reverse occurred with the response to the amino acid mixture, with larvae conditioned on diets containing protein (PC and P) being less responsive to the amino acid mixture than those conditioned on diets lacking protein (C and 0). After the 9h choice period, the responsiveness of sensilla was no longer related to the conditioning diet.
Characterization of Oscillatory Olfactory Interneurones in the Protocerebrum of the Crayfish
Authors: Mellon Deforest , Sandeman David C. , Sandeman Renate E.
Published: April 2021

We obtained intracellular electrophysiological recordings from local interneurones within the hemi-ellipsoid neuropile of the brain in the freshwater crayfish Cherax destructor and Procambarus clarkii. The recordings were made from perfused, isolated head preparations that provided several indications of a healthy physiological condition. The hemi-ellipsoid interneurones are spontaneously active, generating bursts of action potentials at regular intervals. The inter-burst period differs among neurones, varying from about 1.0 s at the shortest periods to around 30 s for the longest periods. Evidence from both electrophysiological recordings and from injection of Lucifer Yellow and Neurobiotin dyes into hemi-ellipsoid interneurones suggests that some of the cells in the populations are electrically coupled to one another. Hemi-ellipsoid interneurones are driven postsynaptically by axons within the lateral protocerebral tract. Experiments with focal electrical stimulation strongly suggest that the pathways responsible include axons of the olfactory–globular tract. These findings support our previous electron microscopical data showing that olfactory–globular tract axons are presynaptic to the hemi-ellipsoid interneurones. These findings support the conclusion that hemi-ellipsoid interneurones are an integral link in the central olfactory pathway of the crayfish.
Allosteric Modulation of Haemocyanin Oxygen-Affinity by L-Lactate and Urate in the Lobster Homarus Vulgaris:II. Characterization of Specific Effector Binding Sites
Authors: Nies A. , Zeis B. , Bridges C. R. , Grieshaber M. K.
Published: April 2021

The haemocyanin of Homarus vulgaris possesses specific binding sites for L-lactate and urate, two allosteric modulators of haemocyanin oxygen-affinity. The affinities for both ligands have been determined. The dissociation constants, KD, are 0.87±0.26mmoll−1 for L-lactate and 0.03±0.01mmoll−1 for urate at 15°C and pH 8.0. The affinity of the haemocyanin is about 40 times larger for urate than for L-lactate. The stoichiometry of the binding is two ligands per dodecamer in both cases.

L-Lactate does not compete with urate for its binding site and vice versa, indicating that the ligand binding sites are independent of each other.

The specificity of urate binding to haemocyanin was investigated in competition experiments with allantoin, caffeine and hypoxanthine. The purine derivatives caffeine and hypoxanthine reduce the binding of urate to haemocyanin, whereas allantoin has no effect. Thus, the purine ring system seems to be essential for the binding of urate to haemocyanin.
Oxygen Radical Production in the Sea Anemone Anthopleura Elegantissima and Its Endosymbiotic Algae
Authors: Dykens James A. , Shick J. Malcolm , Benoit Craig , Buettner Garry R. , Winston Gary W.
Published: April 2021

Host animals in algal-invertebrate endosymbiotic associations are exposed to photosynthetically generated hyperoxia while in sunlight, conditions conducive to photodynamic excitations and production of cytotoxic oxygen-derived radicals such as the superoxide anion and the hydroxyl radical (.OH). All previous evidence of oxyradical production in symbiotic associations has been circumstantial. We here present direct evidence, from electron paramagnetic resonance studies on tissue homogenates of the photosymbiont-containing sea anemone Anthopleura elegantissima (Brandt), of substantial light-dependent .OH and production that is abolished by dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. Shade-adapted A. elegantissima lacking endosymbiotic algae likewise show .OH production upon illumination. The latter flux is not dependent on photosynthesis, and DCMU has no effect. Rather, .OH production in apozooxanthellate anemones is via direct photoexcitations. The selective reaction of dimethyl sulfoxide (DMSO) with .OH to form methane sulfinic acid allows quantification of .OH produced in vivo. Such in vivo measurements confirm the production of .OH in both host and algae in illuminated zooxanthel-late anemones, where the amount of .OH in the zooxanthellae is disproportionately large relative to their fractional contribution to the biomass of the symbiosis. In vivo studies using DMSO also suggest a photochemical production of .OH in apozooxanthellate anemones exposed to simulated sunlight enriched in ultraviolet (UV) wavelengths, and the enhancement by UV light of .OH production in zooxanthellate individuals. Such chronic radical exposure necessitates defenses against photooxidative stress, a cost that is seldom considered in these mutualistic symbioses.
Biochemical Comparison of Fast- and Slow-Contracting Squid Muscle
Authors: Kier William M. , Schachat Frederick H.
Published: April 2021

The myofilament protein compositions of muscle fibres from the transverse muscle mass of the tentacles and the transverse muscle mass of the arms of the loliginid squid Sepioteuthis lessoniana were compared. These two muscle masses are distinct types, differing in their ultrastructural and behavioural properties. The transverse muscle of the tentacles consists of specialized muscle fibres that exhibit cross-striation and unusually short sarcomeres and thick filaments. The transverse muscle of the arms consists of obliquely striated muscle fibres that are typical of cephalopod skeletal muscle in general. The specialization of the tentacle muscle results in a high shortening speed and reflects its role in creating rapid elongation of the tentacles during prey capture. Comparison of samples of myofilament preparations of the two muscle fibre types using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and peptide mapping of myosin heavy chains from the two muscle fibre types, however, showed little evidence of differences in contractile protein isoforms. Thus, specialization for high shortening speed appears to have occurred primarily through changes in the dimensions and arrangement of the myofilament lattice, rather than through changes in biochemistry. The thick filament core protein paramyosin was tentatively identified in the squid muscle fibres. This protein was less abundant in the short thick filament cross-striated tentacle muscle cells than in the obliquely striated arm cells.
Allosteric Modulation of Haemocyanin Oxygen-Affinity By L-Lactate and Urate in the Lobster Homarus Vulgaris: I. Specific and Additive Effects on Haemocyanin Oxygen-Affinity
Authors: Zeis B. , Nies A. , Bridges C. R. , Grieshaber M. K.
Published: April 2021

The specific effects of L-lactate and urate on oxygen binding by the haemo-cyanin of the lobster Homarus vulgaris were investigated. Increasing concentrations of L-lactate were found to increase haemocyanin oxygen-affinity. The relationship between the oxygen affinity (logP50) and [L-lactate] expressed as (AlogP5())(Δlog[L-lactate])−1 was −0.11 at L-lactate concentrations between 0.3 and 11 mmol l−1 and pH7.99±0.03. Urate, likewise, had a potentiating effect on haemocyanin oxygen-affinity: (ΔlogP50)( Δlog[urate])−1 was −0.18 at urate concentrations between 0 and 0.93 mmol l−1 and pH7.99±0.03. Cooperativity, expressed as n50, was reduced by the presence of both modulators.

The influence of the simultaneous presence of both factors on haemocyanin oxygen-affinity was also investigated. The effects of L-lactate and urate on haemocyanin oxygen-affinity were found to be additive. The possible physiological role of these modulators is discussed.
Remote Control of the Swimmeret Central Pattern Generator in Crayfish (Procambarus Clarkii and Pacifastacus Leniusculus): Effect of a Walking Leg Proprioceptor
Authors: Cattaert Daniel , Barthe Jean-Yves , Neil Douglas M. , Clarac Francois
Published: April 2021

An isolated preparation of the crayfish nervous system, comprising both the thoracic and the abdominal ganglia together with their nerve roots, has been used to study the influence of a single leg proprioceptor, the coxo-basal chordotonal organ (CBCO), on the fictive swimmeret beating consistently expressed in this preparation. Both mechanical stimulation of the CBCO and electrical stimulation of its nerve were used. In preparations not displaying rhythmic activity, electrical or mechanical stimulations evoked excitatory postsynaptic potentials (EPSPs) in about 30% of the studied motor neurones with a fairly short and regular delay, suggesting an oligosynaptic pathway. Such stimulation could evoke rhythmic activity in swimmeret motor nerves. The evoked swimmeret rhythm often continued for several seconds after the stimulus period. When the swimmeret rhythm was well established, electrical and mechanical stimuli modified it in a number of ways. Limited mechanical or weak electrical stimuli produced a small increase in swimmeret beat frequency, while more extreme movements of the CBCO or strong electrical stimuli had a disruptive effect on the rhythm. The effect of low-intensity stimulation on existing swimmeret beating was phase-dependent: it shortened the beat cycle when applied during the powerstroke phase and lengthened it when applied during the retumstroke phase. Rhythmic mechanical stimulation of CBCO or electrical stimulation of the CBCO nerve entrained the swimmeret rhythm within a limited range in relative or absolute coordination. Electrical stimuli also produced systematic effects on the whole metachronal pattern of the swimmeret rhythm, perturbing the interganglionic coordination.
Posterior Lymph Heart Pressure and Rate and Lymph Flow in the Toad Bufo Marinus in Response to Hydrated and Dehydrated Conditions
Authors: Jones Judy M. , Wentzell Lee A. , Toews Daniel P.
Published: April 2021

Posterior lymph heart pressure, rate and flow were measured in chronically cannulated Bufo marinus during normal hydrated and dehydrated conditions. A new surgical technique was developed which allowed direct and constant measurement of the functioning of the posterior lymph hearts with minimal disruption to normal lymph drainage. The mean intra-lymph-heart systolic pressure was 2.29±0.12kPa for hydrated animals at rest, decreasing to 1.01±0.10kPa after 24h of dehydration. Similarly, lymph heart rate, which was 48.2±1.7beats min−1 under hydrated conditions, decreased to 31.8±4.6beats min−1 after 18h of dehydration. Lymph flow decreased almost to zero during dehydration from a hydrated rate of 1.11±0.04mlh−1100g−1. This is the first study to measure directly and to correlate these variables in an amphibian and to show specifically that pressure, rate and lymph flow are significantly reduced during periods of dehydration.
The Stopping Response of Xenopus Laevis Embryos: Pharmacology and Intracellular Physiology of Rhythmic Spinal Neurones and Hindbrain Neurones
Authors: Boothby Kate M. , Roberts Alan
Published: April 2021

Xenopus laevis embryos stop swimming in response to pressure on the cement gland. This behaviour and ‘fictive’ stopping are blocked by bicuculline (10μmoll−1), tubocurarine (110μmoll−1) and kynurenic acid (0.5 mmol l−1). Intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (IPSPs). These are blocked by bicuculline, tubocurarine and kynurenic acid, but are unaffected by strychnine (2μmoll−1). When the cement gland is pressed, trigeminal ganglion activity precedes both the IPSPs and the termination of ‘fictive’ swimming activity recorded in rhythmic spinal neurones. The trigeminal discharge is unaffected by the antagonists bicuculline, tubocurarine, kynurenic acid and strychnine. Intracellular recordings from the hindbrain have revealed neurones that are normally silent, but rhythmically inhibited during ‘fictive’ swimming. In these neurones pressure on the cement gland evokes depolarising potentials, often with one or more spikes. We propose that the stopping response depends on the excitation of pressure-sensitive trigeminal receptors which innervate the cement gland. These release an excitatory amino acid to excite brainstem GABAergic reticulospinal neurones, which inhibit spinal neurones to turn off the central pattern generator for swimming. There may also be a less direct pathway.