bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for the Involvement of Cyclic Amp in the Pheromonal Modulation of Barnacle Settlement
Authors: Clare Anthony S. , Thomas Ronald F. , Rittschof Daniel
Published: April 2021

The involvement of cyclic AMP in the settlement of the cypris larva of Balanus amphitrite amphitrite Darwin has been examined through the use of compounds that affect intracellular cyclic AMP levels. The activation of adenylate cyclase with forskolin, and the inhibition of phosphodiesterase with 3-isobutyl-1-methylxanthine, caffeine and theophylline, significantly increased the settlement of cyprids. Although the analogue dibutyryl cyclic AMP appeared to increase settlement, the effect was not significant. No marked increase in settlement resulted from the incubation of cyprids with dibutyryl cyclic GMP, 8-(4-chlorophenylthio) (CPT) cyclic AMP or papaverine (a phosphodiesterase inhibitor). Miconazole nitrate, an adenylate cyclase inhibitor, prevented settlement, but this effect appeared to be physico-chemical rather than pharmacological. Radioimmunoassay did not clearly show whether cyclic AMP levels changed following exposure of cyprids to a pulse of crude barnacle extract. However, exposure to forskolin significantly increased the cyclic AMP titre of cyprids. We conclude that compounds that alter intracellular cyclic AMP levels alter normal patterns of cyprid settlement. Whether this is because of an alteration in signal transduction is unclear.
Spatial Orientation in the Lamprey : I. Control of Pitch and Roll
Authors: Ullén F. , Deliagina T. G. , Orlovsky G. N. , Grillner S.
Published: April 2021

Two major tasks must be fulfilled during locomotion: propulsion and spatial orientation. In the lamprey, the propulsive force is generated by laterally directed body undulations propagated from the rostral to the caudal end of the body. The neuronal networks underlying this basic locomotor pattern have been described in considerable detail. The present study was undertaken to provide the necessary behavioural background for parallel studies of the vestibular neuronal networks responsible for spatial orientation during locomotion. The following results were obtained.

The lamprey actively stabilized its pitch angle during swimming and usually kept a linear trajectory in the sagittal plane, despite large changes in the speed of swimming. During repeated tests, a certain preferred pitch angle could be maintained over a period of several minutes, even if the initial starting angle of the animal was changed considerably. Two different strategies were observed for active turning in the downward direction: a smooth turn accomplished by weak ventral flexion of the whole body, and a sharp turn accomplished by localized ventral flexion of a region of the body just posterior to the gills. The lampreys were oriented with the dorsal side up while swimming at any pitch angle. The control systems for pitch and roll can thus operate independently. When swimming, lampreys kept the tail region flexed somewhat ventrally. This body configuration will cause lateral movements of the tail to generate a torque that rotates the body around its longitudinal axis. This mechanism is presumably used to correct deviations from the dorsal-side-up orientation. After amputation of the dorsal and tail fins, lampreys maintained a proper spatial orientation during swimming. After a unilateral labyrinthectomy, swimming lampreys continuously rolled towards the lesioned side. Unilaterally labyrinthectomized animals displayed a tonic twisting of the body into a helical shape. This presumably represents an additional strategy for performing roll turns. Bilaterally labyrinthectomized animals never maintained a linear trajectory in any plane, but turned continuously in all directions.
Spatial Orientation in the Lamprey : II. Visual Influence on Orientation During Locomotion and In The Attached State
Authors: Ullén F. , Deliagina T. G. , Orlovsky G. N. , Grillner S.
Published: April 2021

The responses of attached lampreys to homogeneous visual stimulation and the role of visual stimuli in orientation during locomotion were investigated. Experiments were performed by video recording the responses of intact and lesioned animals to illumination. The following results were obtained.

In lampreys attached with their sucker mouth to the bottom of the aquarium, illumination of one eye evoked several possible motor responses (ordered after mean latency): (a) movement of the illuminated eye downwards, and the contralateral eye upwards; (b) rotation of the body around the longitudinal axis, with the illuminated side tilting downwards; (c) deviation of the caudal part of the anterior dorsal fin in the contralateral direction (away from the light); and (d) flexion of the neck and body towards the side of illumination. Illumination of one eye in attached lampreys often resulted in detachment and subsequent movement in a direction away from the light source (negative phototaxis). This response was not related to the degree of roll tilt before detachment, so the negative phototaxis does not appear to be a consequence of the vestibular stimulation. Negative phototaxis was also seen during locomotion: lampreys turned through 180 ˚ when they approached a brightly illuminated area. Photostimulation also affected their orientation in the transverse plane during swimming. Illumination of one eye from the side induced a roll movement, so that the illuminated side tilted downwards and the dorsum of the lamprey became turned towards the light. This is similar to the ‘dorsal light response’ of fish and shows that vision also plays a role in postural control in lampreys. The behaviour of blinded animals differed strikingly from that of intact ones. Whereas intact animals preferentially swam close to the bottom, along horizontal trajectories, blinded animals showed episodes of continuous swimming upwards, near the water surface. During horizontal swimming, their orientation in the transverse plane remained normal, with the dorsal side up.
Locomotor Patterns in Freely Moving Crayfish (Procambarus Clarkii)
Authors: Jamon Marc , Clarac François
Published: April 2021

Freely walking crayfish, Procambarus clarkii, were studied using a video analysis procedure adapted especially for use with crayfish. The animals were placed in a tank and their homing behaviour was filmed as they returned in a straight line to their shelter. Various sequences were studied at the two following levels. First, the trajectory of each pair of legs (from leg 2 to leg 5) during the step cycle (power stroke and return stroke) was studied to measure stride length and to analyse in detail changes in acceleration. Each leg was found to contribute in a specific manner to locomotion. Second, ipsi-and contralateral leg coordination was investigated. Ipsilateral coordination was found to involve a metachronal organization from front to back in all the walking sequences recorded, whereas contralateral coordination involved, in addition to the weak alternate coupling commonly observed in treadmill walking, another coordination pattern where the legs on each side (legs 3 and 4) are in phase. The results obtained in these free-walking sequences are discussed and compared with those obtained previously, in particular in treadmill situations.
Electrosensory Thresholds in Larvae of the Weakly Electric Fish Pollimyrus Isidori (Mormyridae, Teleostei) During Ontogeny
Authors: Postner Martin , Kramer Bernd
Published: April 2021

Electrosensory thresholds and tuning were determined from behavioural studies in larvae of Pollimyrus isidori using the stop response of their electric organ discharge to weak electrical stimuli. Two age groups were studied: (1) 10-to 15-day-old larvae in which the electric organ discharge (EOD), produced by a distinct larval electric organ, had just stabilized; (2) 54-to 60-day-old larvae, just before the advent of the adult EOD (an adult electric organ functionally replaces that of the larva between about 60 and 80 days). Three stimulus pulse waveforms were used: (1) single-cycle, bipolar sine-wave pulses; (2) single-cycle, monopolar sine-wave pulses and (3) monopolar square-wave pulses.

The younger larvae were exceedingly sensitive to weak electrical stimuli, down to the 10 µVp–p cm−1 range. Stimulus pulse duration had a significant effect on threshold for all three pulse waveforms, but the shapes of the tuning curves were quite different. Thresholds at the ‘best’ pulse duration were lower and the tuning sharper (with a V-shaped curve) with monopolar sine-wave pulses than with bipolar sine-wave pulses. The ‘best’ pulse duration was 1 ms for both sine-wave pulses, corresponding well to the spectral peak amplitude of larval EODs (964±22 Hz). The threshold curve for monopolar sine-wave pulses appeared to be perfectly adapted for sensing larval rather than adult EODs. With square-pulse stimuli, thresholds increased monotonically with duration and there was no evidence of tuning for this kind of stimulus. These results suggest that both conventional spectral tuning and ‘tuning’ to a particular pulse waveform (with a monopolar sine-wave pulse best approximating the waveform of a larval discharge) are found in young larvae. In the older age group, larvae were more sensitive to all three kinds of stimuli than those of the younger age group. The sensitivity increase varied from 10 dB to 29 dB; at stimuli of 2.4 µVp–p cm−1, larvae just 18 mm long displayed adult sensitivity. No tuning was seen for square-wave pulses and, as in younger larvae, their effectiveness increased monotonically with duration, so that for neither age group are square-wave pulses a good model for larval EODs. The threshold curves for both types of sine-wave pulse were similar and resembled the broadband tuning curves of Knollenorgan electroreceptors. Tuning was present but weak, with sensitivity for the high-frequency range much greater than for younger larvae. This change is adaptive for sensing both larval and adult EODs and occurred before the larvae developed an adult EOD.

The mechanism for a change in tuning that has been established for electroreceptors in adult mormyrids and gymnotiforms, where the spectral properties of the EOD of a fish entrain its electroreceptors, is not found in the larvae of Pollimyrus isidori, which ‘anticipate’ the tuning necessary for the reception of their own, future adult EOD.
Effects of Anoxia on Energy Metabolism in Crucian Carp Brain Slices Studied With Microcalorimetry
Authors: Johansson Dan , Nilsson Göran E. , Törnblom Erik
Published: April 2021

Crucian carp (Carassius carassius L.) is an exceptionally anoxia-tolerant vertebrate. To determine whether isolated crucian carp brain tissue survives anoxia and whether it displays anoxic metabolic depression, heat production (using microcalorimetry), lactate production, ethanol production and the maintenance of ATP, ADP and AMP levels and energy charge were measured in telencephalic brain slices during anoxia. In response to anoxia, heat output decreased by 37 %, corresponding to a 31 % fall in ATP turnover rate. Adenylate phosphates and energy charge were well maintained and no ethanol was produced during anoxia. It is concluded that crucian carp brain tissue has an intrinsic capacity to tolerate anoxia and that it responds to anoxia by depressing metabolic rate and elevating the glycolytic rate, thereby maintaining ATP levels.
Ingestive Sensory Inputs Excite Serotonin Effector Neurones and Promote Serotonin Depletion From the Leech Central Nervous System and Periphery
Authors: Groome James R. , Vaughan Dana K. , Lent Charles M.
Published: April 2021

Thermal and chemical stimuli known to promote ingestive behaviours in the medicinal leech Hirudo medicinalis were tested for their physiological effects on Retzius neurones and for their biochemical effects on serotonin levels in the central nervous system, pharynx and body wall. Retzius neurones throughout the leech nerve cord receive excitatory synaptic input during thermal or chemical stimulation of the prostomial lip. These neurones respond to the rate of change of temperature as well as to absolute temperature at the lip. Exposure of the lip to sodium chloride excites Retzius neurones, whereas exposure to arginine has little effect. Thermal stimulation of the lip elicits a more rapid but less prolonged excitation of Retzius neurones than does chemical stimulation.

Stimulation of the prostomial lip is associated with afferent activities in the cephalic nerves D1, D2 and V1–2. Thermal stimulation of the prostomial lip results in depletion of serotonin from midbody ganglia, whereas chemical stimulation has no effect. Conversely, chemical stimulation of the lip results in depletion of serotonin from the body wall, whereas thermal stimulation does not. Pharyngeal serotonin content is decreased with either modality. These data distinguish two important feeding-related sensory input pathways to central serotonergic effector neurones in Hirudo medicinalis.
A Neurotransmitter Role for Red-Pigment-Concentrating Hormone in Ovarian Maturation in the Red Swamp Crayfish Procambarus Clarkii
Authors: Sarojini Rachakonda , Nagabhushanam Rachakonda , Fingerman Milton
Published: April 2021

The influence of red-pigment-concentrating hormone (RPCH) on ovarian maturation in the red swamp crayfish Procambarus clarkii was studied using both in vivo and in vitro techniques. In vivo, RPCH stimulated ovarian maturation. However, RPCH did not affect the ovary in vitro when only RPCH, muscle and ovarian explants were used. But when RPCH, thoracic ganglia, which are known to contain gonad-stimulating hormone-like (GSH-like) activity, and ovarian explants were incubated together, significant ovarian maturation ensued. The calcium ionophore A23187 mimicked RPCH both in vivo and in vitro. These results provide evidence to support the hypothesis that RPCH has a role as a neurotransmitter in Procambarus clarkii to stimulate GSH release, with calcium acting as a second messenger for RPCH.
The Motor Program for Defensive Kicking in Crickets: Performance and Neural Control
Authors: Hustert Reinhold , Gnatzy Werner
Published: April 2021

Crickets can repulse sources of mechanical touch to their wings, legs or to the posterior body by kicking backwards ipsilaterally with one hindleg. The main component of a kick is the rapid extension of the femoro-tibial (knee) joint. A kick as a defence against predators must occur instantly after the moment of touch. The cricket kick is completed within 60–100 ms, whereas in locusts 500–2000 ms elapses between the stimulus and the end of the kick. The rapid movement of the cricket hindleg was recorded with a high-resolution video technique. Cricket kicking is based on a dynamic co-contraction of the extensor and flexor tibiae muscles during the pre-kick knee flexion period, thus differing from the static co-contraction period seen in locusts. Biomechanically, the knee joint is specialized for kicking and jumping by the specific leverage of tendons inserting at the knee, by a femoral ridge that modifies the angle of attack for flexor muscular forces and by a cushion-like swelling on the flexor tibiae tendon. Because of these structural specialisations for rapid kicking, the neural control of the motor pattern of the muscles participating in the tibial movement can vary considerably, but still produce efficient kicks. Kicking is also an element of other complex behaviours.
Adaptive Responses to Feeding in Burmese Pythons: Pay Before Pumping
Authors: Secor Stephen M. , Diamond Jared
Published: April 2021

Burmese pythons normally consume large meals after long intervals. We measured gut contents, O2 consumption rates, small intestinal brush-border uptake rates of amino acids and glucose, organ masses and blood chemistry in pythons during the 30 days following ingestion of meals equivalent to 25 % of their body mass. Within 1–3 days after ingestion, O2 consumption rates, intestinal nutrient uptake rates and uptake capacities peaked at 17, 6–26 and 11–24 times fasting levels, respectively. Small intestinal mass doubled, and other organs also increased in mass. Changes in blood chemistry included a 78 % decline in and a large ‘alkaline tide’ associated with gastric acid section (i.e. a rise in blood pH and HCO3-concentrations and a fall in Cl-concentration). All of these values returned to fasting levels by the time of defecation at 8–14 days. The response of O2 consumption (referred to as specific dynamic action, SDA) is the largest, and the up-regulation of intestinal nutrient transporters the second largest, response reported for any vertebrate upon feeding. The SDA is as large as the factorial rise in O2 consumption measured in mammalian sprinters and is sustained for much longer. The extra energy expended for digestion is equivalent to 32 % of the meal’s energy yield, with much of it being measured before the prey energy was absorbed.
Calcium Pump Activities in the Kidneys of Oreochromis Mossambicus
Authors: Bijvelds Marcel J. C. , Heijden Angelique J. H. Van Der , Flik Gert , Verbost Pieter M. , Kolar Zvonimir I. , Bonga Sjoerd E. Wendelaar
Published: April 2021

The mechanism that underlies transcellular Ca2+ reabsorption in the kidney of the euryhaline teleost Oreochromis mossambicus was studied. Preparations of membrane vesicles made from the kidneys of freshwater-and seawater-adapted fish were more than sevenfold enriched in the basolateral plasma membrane marker Na+/K+-ATPase. Significant recovery of NADH– cytochrome c reductase enzyme activity and of oxalate-stimulated Ca2+ pump activities in the membrane preparations indicated that the membrane fraction was of endoplasmic reticular origin. Indeed, thapsigargin specifically inhibited Ca2+ pump activity that could be attributed to oxalate-permeable endoplasmic reticular fragments. Kinetic analysis of thapsigargin-insensitive

Ca2+ pump activity indicated the existence of a homogeneous, high-affinity, ATP-driven Ca2+ pump. No Na+-driven Ca2+ transport mechanism could be demonstrated. Plasma membrane Ca2+ pump activity was 56 % lower in preparations from seawater-adapted fish than in preparations from freshwater-adapted fish, suggesting a physiological role for this Ca2+ pump activity in renal Ca2+ handling by euryhaline species, with an involvement in the regulation of Ca2+ reabsorption.
Ventilatory Responses to Carboxyhaemoglobinaemia and Hypoxic Hypoxia in Bufo Paracnemis
Authors: Branco Luiz G. S. , Glass Mogens L.
Published: April 2021

The modality of the O2 drive to breathe was evaluated in unanaesthetized Bufo paracnemis. Carbon monoxide (CO) hypoxia was applied to reduce (arterial O2 content). Arterial was reduced through inspiration of hypoxic gas mixtures (hypoxic hypoxia). Measurements included pulmonary ventilation, , , pHa, blood pressure and heart rate. Application of fractional concentrations of CO equivalent to 0.001 reduced from 11.6±1.2 to 8.6±0.7 vol% (mean ± S.E.M., N=6) without any effect on heart rate, blood pressure or ventilation. Inspiration of fractionl concentrations of CO equivalent to 0.01 reduced to 5.1±0.7 vol%, which was accompanied by increased ventilation. This response, however, correlated with a decreased arterial pH. The effect of a fractional concentration of CO of 0.01 on ventilation was abolished by compensation of pH through bicarbonate infusion. Consequently, carboxyhaemoglobinaemia per se failed to increase ventilation. By contrast, reductions of clearly stimulated ventilation, which indicates that O2 partial pressure provides the principal O2 stimulus to breathe in Bufo paracnemis.
Modulation Of Crayfish Retinal Function By Red Pigment Concentrating Hormone
Authors: Garfias Alfonso , Rodríguez-Sosa Leonardo , Aréchiga Hugo
Published: April 2021

The role of the crustacean octapeptide red pigment concentrating hormone (RPCH) in the control of crayfish retinal activity was explored. RPCH injection into intact animals resulted, after a latency of 10–30 min, in a dose-dependent enhancement of electroretinogram (ERG) amplitude lasting 60–120 min.

RPCH was able to potentiate ERG amplitude in both light-adapted and dark-adapted animals. Following light-adaptation, responsiveness to RPCH was five times higher than following dark-adaptation.

In conjunction with ERG enhancement, in light-adapted animals, RPCH injection elicited a dose-dependent retraction of distal retinal pigment, but did not affect proximal retinal pigment position.

The effects of RPCH were blocked by a polyclonal antibody raised against a tyrosinated form of RPCH (A-tyr-RPCH). The antibody was also capable of partially blocking the nocturnal phase of the circadian rhythm of ERG amplitude and the darkness-induced retraction of distal retinal pigment.

These results suggest that RPCH acts both on the retinal photoreceptors and on the distal pigment cells, playing a physiological role as a mediator of the effects induced by darkness and by the nocturnal phase of the circadian rhythm.
The Transition To Air Breathing In Fishes : V. Comparative Aspects Of Cardiorespiratory Regulation In Synbranchus Marmoratus And Monopterus Albus (Synbranchidae)
Authors: Graham Jeffrey B. , Lai N. C. , Chiller David , Roberts John L.
Published: April 2021

Extreme heart-rate lability accompanies the air-breathing cycles of Synbranchus marmoratus and Monopterus albus. When air is taken into the buccopharyngeal air-breathing organ of these fishes, heart rate increases sharply above pre-inspiration rates of 3–25 beats min-1 to as high as 40–45 beats min−1. With time, and as O2 is depleted from the air-breathing organ, heart rate gradually declines and drops to its lowest level with, or following, exhalation. Relationships between air breathing and sinus arrhythmia in M. albus were investigated by injecting variable gas volumes and O2 mixtures into the cannulated air-breathing organ. Tests were also carried out on undisturbed fish breathing volitionally in atmospheres containing different O2 levels. Both the volume and O2 content of the inspired gas affect the level and duration of inspiration tachycardia. Additional factors affecting tachycardia are the heart rate prior to inspiration and the time since air was last held. S. marmoratus is a non-obligatory air breather and uses rhythmic branchial aquatic respiration to a greater extent than M. albus, an obligate air breather. While the heart rates of both species are increased during aquatic ventilation, the higher heart rate to ventilation ratio in S. marmoratus (2–3 versus approximately 1 in M. albus) seems attributable to its more proficient aquatic respiratory system. The available cardiorespiratory data for air-breathing fishes indicate that the scope of air-inspiration tachycardia is smaller in lungfishes and other primitive species than in most teleosts. This difference is mainly attributable to the greater chronotropic effect of sympathetic cardiac innervation in teleosts.
Ionic Currents in Identified Swimmeret Motor Neurones of the Crayfish Pacifastacus Leniusculus
Authors: Chrachri Abdesslam
Published: April 2021

Ionic currents from freshly isolated and identified swimmeret motor neurones were characterized using a whole-cell patch-clamp technique. Two outward currents could be distinguished. A transient outward current was elicited by delivering depolarizing voltage steps from a holding potential of -80 mV. This current was inactivated by holding the cells at a potential of -40 mV and was also blocked completely by 4-aminopyridine. A second current had a sustained time course and continued to be activated at a holding potential of -40 mV. This current was partially blocked by tetraethylammonium. These outward currents resembled two previously described potassium currents: the K+ A-current and the delayed K+ rectifier current respectively.

Two inward currents were also detected. A fast transient current was blocked by tetrodotoxin and inactivated at holding potential of -40 mV, suggesting that this is an inward Na+ current. A second inward current had a sustained time course and was affected neither by tetrodotoxin nor by holding the cell at a potential of -40 mV. This current was substantially enhanced by the addition of Ba2+ to the bath or when equimolar Ba2+ replaced Ca2+ as the charge carrier. Furthermore, this current was significantly suppressed by nifedipine. All these points suggest that this is an L-type Ca2+ current.

Bath application of nifedipine into an isolated swimmeret preparation affected both the frequency of the swimmeret rhythm and the duration of power-stroke activity, suggesting an important role for the inward Ca2+ current in maintaining a regular swimmeret rhythmic activity in crayfish.
Role of Adenosine In Nmda Receptor Modulation in the Cerebral Cortex of an Anoxia-Tolerant Turtle (Chrysemys Picta Belli)
Authors: Buck L. T. , Bickler P. E.
Published: April 2021

Accumulation of the neuromodulator adenosine in the anoxia-tolerant turtle brain may play a key role in a protective decrease in excitatory neurotransmission during anoxia. Since excitatory neurotransmission is mediated largely by Ca2+ entry through N-methyl-D-aspartate (NMDA) receptors, we measured the effect of adenosine on NMDA-mediated Ca2+ transients in normoxic and anoxic turtle cerebrocortical sheets. Intracellular [Ca2+] was measured fluorometrically with the Ca2+-sensitive dye Fura-2. Baseline intracellular [Ca2+] and [ATP] were also measured to assess cortical sheet viability and potential toxic effects of NMDA. Baseline [Ca2+] did not change significantly under any condition, ranging from 109±22 to 187±26 nmol l-1. Throughout normoxic and 2 h anoxic protocols, and after single and multiple NMDA exposures, [ATP] did not change significantly, ranging from 16.0±1.9 to 25.3±4.9 nmol ATP mg-1 protein. Adenosine caused a reduction in the normoxic NMDA-mediated increase in [Ca2+] from a control level of 287±35 to 103±22 nmol l-1 (64 %). This effect is mediated by the A1 receptor since 8-phenyltheophylline (a specific A1 antagonist) effectively blocked the adenosine effect and N6-cyclopentyladenosine (a specific A1 agonist) elicited a similar decrease in the NMDA-mediated response. Cortical sheets exposed to anoxia alone exhibited a 52 % decrease in the NMDA-mediated [Ca2+] rise, from 232±30 to 111±9 nmol l-1. The addition of adenosine had no further effect and 8-phenyltheophylline did not antagonize the observed decrease. Therefore, the observed down-regulation of NMDA receptor activity during anoxia must involve additional, as yet unknown, mechanisms.
Application of Putative Neurotransmitters Elicits and Modulates Stridulation in two Species of Acridid Grasshoppers
Authors: Ocker W.-G. , Hedwig B. , Elsner N.
Published: April 2021

The influence of neurotransmitters and neuroactive substances on stridulatory behaviour was analysed in two species of acridid grasshoppers (Omocestus viridulus and Chorthippus mollis). Acetylcholine, octopamine, γ-aminobutyric acid and glutamate were applied by pressure injection (0.5–1.0 nl, 10−3 mol l-1) into the protocerebrum. All except octopamine were also applied to the metathoracic ganglion by pressure injection or superfusion (1 ml).

Injection of acetylcholine into the medial dorsal neuropile of the protocerebrum elicited continuous long-lasting species-specific stridulation in both acridid species. All other substances tested had no effect when injected into the brain. Injection of acetylcholine into the medial dorsal neuropile of the metathoracic ganglion enhanced the amplitude of the stridulatory leg movements elicited by electrical brain stimulation. It did not alter the repetition rate or coordination of the movements in O. viridulus; but it decreased the length of stridulatory cycles in C. mollis.

Injection of γ-aminobutyric acid into the medial dorsal metathoracic neuropile in both species suppressed the stridulatory leg movements ipsilateral to the injection site but did not alter those on the contralateral side. Superfusion of the metathoracic ganglion with -γaminobutyric acid suppressed the movements of both hindlegs.

Pressure injection of glutamate into the metathoracic ganglion had no effect on the stridulatory leg movements, but superfusion enhanced the stridulatory movements.
Chemosensitivity of the Osphradium of the Pond Snail Lymnaea Stagnalis
Authors: Wedemeyer Heiner , Schild Detlev
Published: April 2021

The osphradium of the pond snail Lymnaea stagnalis was studied to determine the stimuli to which this organ responds. The following stimuli were tested: hypoxia, hypercapnia, a mixture of amino acids, a mixture of citralva and amyl acetate and a mixture of lyral, lilial and ethylvanillin.

The mean nerve activity consistently increased with elevated whereas hypoxia produced variable effects. The nerve activity became rhythmic upon application of citralva and amyl acetate, but it increased in a non-rhythmic way upon application of the other two odorant mixtures tested.

Whole-cell patch-clamp recordings were made from a group of 15 neurones that lay next to the issuing osphradial nerve, to determine whether ganglion cells were involved in olfactory signal processing. All neurones tested responded to at least one of the three mixtures of odorants. Both excitatory and inhibitory responses occurred.

Our results indicate that the osphradium of the pond snail Lymnaea stagnalis is sensitive to elevated as well as to three different classes of odorants. In addition, at least some neurones within the osphradium are involved in the processing of olfactory information.
Acid–Base Status and Spiracular Control During Discontinuous Ventilation in Grasshoppers
Authors: Harrison Jon F. , Hadley Neil F. , Quinlan Michael C.
Published: April 2021

Many insects ventilate discontinuously when quiescent, exhibiting prolonged periods during which little or no gas exchange occurs. We investigated the consequences of discontinuous ventilation (DV) on haemolymph acid–base status and tested whether spiracular opening during DV is due to changes in internal gas tensions in the western lubber grasshopper Taeniopoda eques. At 15 °C, resting T. eques exhibited interburst periods of about 40 min. During the interburst period, haemolymph rose from 1.8 to 2.26 kPa, with minimal acidification of haemolymph. Animals in atmospheres in which was 2 kPa or below continued to exhibit DV, while atmospheres in which was 2.9 kPa or above caused cessation of DV. These data indicate that accumulation of internal CO2 to threshold levels between 2 and 2.9 kPa induces spiracular opening in grasshoppers. In contrast to the situation in lepidopteran pupae, variation in atmospheric had no effect on interburst duration. Relative to lepidopteran pupae, the internal of grasshoppers during DV is threefold lower, the required for triggering spiracular opening is also threefold lower, and the open phase spiracular conductance is at least tenfold higher, demonstrating that considerable diversity exists in these aspects of insect respiratory physiology.
Adjustment of K′ to Varying pH and pMg for the Creatine Kinase, Adenylate Kinase and Atp Hydrolysis Equilibria Permitting Quantitative Bioenergetic Assessment
Authors: Golding Elke M. , Teague Walter E. , Dobson Geoffrey P.
Published: April 2021

Physiologists and biochemists frequently ignore the importance of adjusting equilibrium constants to the ionic conditions of the cell prior to calculating a number of bioenergetic and kinetic parameters. The present study examines the effect of pH and free magnesium levels (free [Mg2+]) on the apparent equilibrium constants (K′) of creatine kinase (ATP: creatine N-phosphotransferase; EC 2.7.3.2), adenylate kinase (ATP:AMP phosphotransferase; EC 2.7.4.3) and adenosinetriphosphatase (ATP phosphohydrolase; EC 3.6.1.3) reactions. We show how K′ can be calculated using the equilibrium constant of a specified chemical reaction (Kref) and the appropriate acid-dissociation and Mg2+-binding constants at an ionic strength (I) of 0.25 mol l−1and 38 °C. Substituting the experimentally determined intracellular pH and free [Mg2+] into the equation containing a known Kref and two variables, pH and free [Mg2+], enables K′ to be calculated at the experimental ionic conditions. Knowledge of K′ permits calculation of cytosolic phosphorylation ratio ([ATP]/[ADP][Pi]), cytosolic free [ADP], free [AMP], standard transformed Gibbs energy of formation (ΔfG′ °ATP) and the transformed Gibbs energy of the system (ΔfG′ATP) for the biological system. Such information is vital for the quantification of organ and tissue bioenergetics under physiological and pathophysiological conditions.
Do Fish Acclimated To Low Temperature Improve Microcirculatory Perfusion By Adapting Red Cell Rheology?
Authors: Lecklin Tiina , Nash Gerard B. , Egginton Stuart
Published: April 2021

We have measured the rheological properties of individual red blood cells from fishes inhabiting different thermal environments and have also investigated the effects on red cells of acute in vitro temperature changes. The membrane shear elastic modulus (rigidity) increased markedly with decreasing temperature, and the dependence was similar if temperature was varied acutely in vitro or if cells were measured at normal body temperatures. Red cells from trout and Notothenia coriiceps had almost equal membrane rigidity at comparable temperatures and showed similar temperature-sensitivity in acute experiments. Entry times of trout cells into narrow (approximately 4 μm diameter) micropipettes also increased during in vitro reduction of temperature, and this could be explained largely by the temperature-dependence expected of aqueous solutions. Perhaps surprisingly, entry times did not vary when trout living at different temperatures were tested at these temperatures. Transit times of individual cells through somewhat larger pores (5 μm) in oligopore filters again increased with decreasing temperature in vitro (partly due to increasing fluid viscosity), but such transit times did show a similar temperature-dependence for cells from trout living at different temperatures. Thus, the temperature-dependence of cellular flow resistance appears to arise from variations in membrane rigidity and in the viscosity of fluid components, along with unquantified variations in components such as microtubular structures (which we found did not influence membrane rigidity but did affect pore entry time) and the cell nucleus. Thermal acclimation did not involve adaptation to compensate for increased membrane rigidity or a large pore transit time, with, at most, minor compensation in entry times into smaller pores. We conclude that impaired cellular rheology is not a major factor influencing circulation in fish at low temperature.
In Vivo Muscle Force and Elastic Energy Storage During Steady-Speed Hopping of Tammar Wallabies (Macropus Eugenii)
Authors: Biewener Andrew A. , Baudinette Russell V.
Published: April 2021

In order to evaluate the role of elastic energy recovery in the hopping of macropodids, in vivo measurements of muscle–tendon forces using buckle force transducers attached to the tendons of the gastrocnemius (G), plantaris (PL) and flexor digitorum longus (FDL) of tammar wallabies were made as the animals hopped on a treadmill at speeds ranging from 2.1 to 6.3 m s−1. These muscles and tendons constitute the main structures that are most important in energy storage and recovery. Electromyographic recordings from the lateral gastrocnemius and plantaris muscles, together with high-speed films (200 frames s−1) and video (60 fields s−1), were also used to correlate muscle activation and kinematic patterns of limb movement with force development. On the basis of in situ calibrations of the buckle transducers, we found that muscle forces and elastic energy storage increased with increased hopping speed in all three muscle–tendon units. Elastic energy recovery reached a maximum of 25 % of metabolic energy expenditure at 6.3 m s−1 and is probably greater than this at higher speeds. Force sharing among the three muscles was consistently maintained over this range of speeds in terms of recruitment. Although forces and stresses were generally comparable within the gastrocnemius and plantaris muscles, maximal tendon stresses were considerably greater in the gastrocnemius, because of its smaller cross-sectional area (peak muscle stress: 227 versus 262 kPa; peak tendon stress: 36 versus 32 MPa, G versus PL). As a result, energy storage was greatest in the gastrocnemius tendon despite its much shorter length, which limits its volume and, hence, energy storage capacity, compared with PL and FDL tendons. Forces and stresses (17 MPa maximum) developed within the FDL tendon were consistently much lower than those for the other two tendons. Peak stresses in these three tendons indicated safety factors of 3.0 for G, 3.3 for PL and 6.0 for FDL. The lower stresses developed within the tendons of the plantaris and, especially, the flexor digitorum longus may indicate the need to maintain sufficient stiffness for phalangeal control of foot placement, at the expense of reduced strain energy recovery.
Natriuretic Peptide Receptors in the Kidney and the Ventral and Dorsal Aortae of the Atlantic Hagfish Myxine Glutinosa (Agnatha)
Authors: Toop Tes , Donald John A. , Evans David H.
Published: April 2021

The character of natriuretic peptide receptors (NPRs) in the kidney and aortae of the Atlantic hagfish Myxine glutinosa was determined and compared with that of NPRs in hagfish gills. The relationship of hagfish kidney and aortic NPRs with NPRs from higher vertebrates was also examined. Iodinated atrial and C-type natriuretic peptides (NPs) (125I-ANP, 125I-CNP) were used in tissue section autoradiography, competition studies and guanylate cyclase (GC) assays. Rat atrial and porcine C-type NPs (rANP, pCNP) and rat des[Gln18, Ser19, Gly20, Leu21 Gly22]ANP-(4-23)-NH2 (C-ANF, which binds to the mammalian and teleost ‘clearance’ receptor, NPR-C), were used as competing ligands. 125I-ANP binding sites were observed on both aortae and on the glomeruli, neck segments and archinephric ducts of the kidney. 4.0 nmol l−1 rANP competed for 50 % of 125I-ANP glomerular sites. 125I-CNP did not visibly bind to any of the tissues, but 300 nmol l−1 pCNP competed for 50 % of 125I-ANP glomerular sites. C-ANF failed to compete for 125I-ANP sites. rANP and pCNP stimulated cyclic GMP production in kidney membrane preparations, but C-ANF did not, demonstrating that the hagfish kidney NPR is GC-linked. This study suggests that a predominant population of ANP-like receptors, similar to the mammalian NPR-A, exists in the myxinoid aortae and kidney tissue. However, no detectable population of a receptor that binds all NPs, such as is present in the hagfish gill, nor an NPR similar to the NPR-C of higher vertebrates was discovered.
The Kinematics and Mechanism of Prey Capture in the African Pig-Nosed Frog (Hemisus Marmoratum): Description of a Radically Divergent Anuran Tongue
Authors: Ritter Dale , Nishikawa Kiisa
Published: April 2021

High-speed videography and muscle denervation experiments were used to quantify the feeding kinematics of Hemisus marmoratum and to test hypotheses of muscle function. The feeding behavior of H. marmoratum, which feeds on ants and termites, differs radically from that of other frogs that have been studied. During feeding in H. marmoratum, the tongue ‘telescopes’ straight out of the mouth, as opposed to the ‘flipping’ tongue trajectory observed in most other frogs. At the time of prey contact, two lateral lobes of tissue at the tongue tip envelop the prey. These lateral lobes are capable of applying significant pulling forces to the prey and the tongue is, therefore, described as prehensile. The trajectory of the tongue can be adjusted throughout protraction so that the frog can ‘aim’ its tongue in all three dimensions; distance, azimuth and elevation. Bilateral denervation of the genioglossus muscles results in a complete lack of tongue protraction, indicating that the genioglossus muscle is the main tongue protractor in H. marmoratum, as in other frogs. Thus, H. marmoratum provides strong evidence of functional conservatism of the genioglossus muscle within anurans. Bilateral denervation of the hyoglossus muscle indicates that although the hyoglossus is involved in several aspects of normal tongue retraction, including the prehensile capability of the tongue tip, it is not necessary for tongue retraction. Unilateral denervation of the genioglossus muscle causes significant deviation of the tongue towards the denervated side, providing evidence for a mechanism of lateral tongue aiming. On the basis of the kinematics of prey capture, the anatomy of the tongue and the results of the denervation experiments, we propose that H. marmoratum uses a hydraulic mechanism to protract its tongue.
The Function of Olfactory Input in Pigeon Orientation: Does it Provide Navigational Information or Play Another Role?
Authors: Wiltschko Roswitha
Published: April 2021

In 1972, Papi and his colleagues reported that anosmic pigeons were severely impaired in orientation and homing performance. This observation was followed up in a series of experiments involving numerous elaborate experimental manipulations. On the basis of their results, the hypothesis of olfactory navigation was proposed. Attempts to replicate these findings at other lofts produced widely differing effects, which suggested a highly variable role of olfaction. However, meteorological data, as well as certain other aspects of the findings, throw doubt on the role of odours as navigational cues. (1) Odours of the required characteristics and distribution do not seem to exist. (2) Some effects of ‘olfactory’ manipulations do not seem to depend on the availability of odours. (3) Olfactory treatments proved mostly effective, but often the effect was not as predicted. In view of these findings, explanations other than olfactory orientation cannot be excluded; accepting olfactory input as navigational information seems premature. Some of the findings are in agreement with the assumption that olfactory manipulations impair the birds’ general processing and integration of information in some unknown way.
Middle-Scale Navigation: The Insect Case
Authors: Wehner Rüdiger
Published: April 2021

What is the large-scale spatial representation that insect foragers such as bees and ants form of their wider nest environs? This is the principal question which the following contributions aim to answer.
Spatial Memory and Navigation by Honeybees on the Scale of the Foraging Range
Authors: Dyer Fred C.
Published: April 2021

Honeybees and other nesting animals face the problem of finding their way between their nest and distant feeding sites. Many studies have shown that insects can learn foraging routes in reference to both landmarks and celestial cues, but it is a major puzzle how spatial information obtained from these environmental features is encoded in memory. This paper reviews recent progress by my colleagues and me towards understanding three specific aspects of this problem in honeybees: (1) how bees learn the spatial relationships among widely separated locations in a familiar terrain; (2) how bees learn the pattern of movement of the sun over the day; and (3) whether, and if so how, bees learn the relationships between celestial cues and landmarks.
Path Integration in Mammals and its Interaction With Visual Landmarks
Authors: Etienne Ariane S. , Maurer Roland , Séguinot Valérie
Published: April 2021

During locomotion, mammals update their position with respect to a fixed point of reference, such as their point of departure, by processing inertial cues, proprioceptive feedback and stored motor commands generated during locomotion. This so-called path integration system (dead reckoning) allows the animal to return to its home, or to a familiar feeding place, even when external cues are absent or novel. However, without the use of external cues, the path integration process leads to rapid accumulation of errors involving both the direction and distance of the goal.

Therefore, even nocturnal species such as hamsters and mice rely more on previously learned visual references than on the path integration system when the two types of information are in conflict. Recent studies investigate the extent to which path integration and familiar visual cues cooperate to optimize the navigational performance.
Structure and Function of Learning Flights in Bees and Wasps
Authors: Zeil Jochen , Kelber Almut , Voss Rüdiger
Published: April 2021

Bees and wasps perform systematic flight manoevres when they leave their nest or a foodplace, during which they acquire or update their visual memory of the goal location. In a typical learning flight, the insect backs away from the goal in a series of arcs that are roughly centred on the goal. The mean rate of turning is rather constant and tends to balance the angular speed at which the arc is described. As a result, the insect views the goal at relatively fixed retinal positions in its left and right visual field, depending on flight direction. The general direction in which the insect backs away from the goal and the transition from one arc segment to the next are influenced by the local scene and by compass cues. Insects returning to the goal repeat some of the flight manoeuvres of their preceding learning flights. Their orientation in space and the retinal positions at which they view nearby landmarks are similar. One important function of learning flights appears to be the acquisition of visual depth information. We review the consequences of the structure of learning flights for visual information processing and discuss how they may relate to the acquisition of a visual representation and the task of pinpointing the goal.
Small-Scale Navigation in the Honeybee: Active Acquisition of Visual Information About the Goal
Authors: Lehrer Miriam
Published: April 2021

In a series of behavioural studies we found that bees use depth information extracted from self-induced image motion in several visual tasks involving pin-pointing the goal. Some of the results are reviewed here in an attempt to emphasise the active nature of this performance. They show that bees acquire depth information during free flight by employing two different strategies. One is to adapt flight behaviour, upon arrival at the food source, to the requirements of the task, a performance that is based on a learning process. The other is based on a stereotyped, innate flight pattern performed upon departure from the food source. The latter has probably evolved specifically for the acquisition of depth information.
Pectoral Fin Locomotion in the Striped Surfperch: II. Scaling Swimming Kinematics and Performance at a Gait Transition
Authors: Drucker Eliot G. , Jensen Jeffrey S.
Published: April 2021

In this study, we report the first allometric equations relating gait parameters and swimming speed to body size for fish employing pectoral fin locomotion. Comparisons of locomotor kinematics and performance among striped surfperch (Teleostei: Embiotocidae) are made at the pectoral–caudal gait transition speed (Up−c). Up−c is considered to elicit physiologically equivalent levels of exercise in animals varying over 100-fold in body mass (Mb) by virtue of dynamically similar pectoral fin movements (constant duty factor, length-specific stride length and fin-beat amplitude) and size-independent propulsive efficiency. At Up−c, pectoral fin-beat frequency scales in proportion to Mb−0.12±0.03, a size-dependence consistent with that observed for stride frequency in fishes swimming by axial undulatory propulsion and in many running tetrapods. It is proposed that the similarity in the scaling of frequency in these vertebrate groups reflects an underlying similarity in the allometry of the maximal velocity of muscle shortening. Absolute Up−c (m s−1) generally increases with body size, but the fastest speeds are not exhibited by the largest animals. A pattern of declining performance in fish 23 cm in standard length and longer may be related to their disproportionately small fin areas and aspect ratios. The pronounced negative allometry of Up−c expressed as standard body lengths per second indicates that a given length-specific speed does not induce comparable levels of activity in large and small fish. Thus, normalization of swimming speed to body length may not be a sufficient correction for kinematic comparisons across size.