bluuebunny/crossref_metadata_2025 huggingface dataset:
Respiratory Mechanics of Sound Production in Chickens and Geese
Authors: Brackenbury J. H.
Published: April 2021

Air flow, air sac pressure and tracheal pressure were measured in chickens and geese during a variety of different vocal and non-vocal activities. Air flow and air sac pressure may rise to 500 ml s−1 and 60 cmH2O (6 × 10s N/m3) respectively during a crow in the chicken. During a sequence of honks in the goose the corresponding values are 650 ml s−1 and 25 cmH2O (2· 5 × 103 N/m2) respectively. The volume of air delivered through the respiratory system during a single crow is more than 400 ml, almost equivalent to the total volume of the lung air sac system. The efficiency of the chicken syrinx as a sound producing instrument, estimated by comparing the sound energy radiated with the energy consumed in the expulsion of air during a crow, appears to be less than 2 %. Cutting the paired sternotrachealis muscles had no effect on vocalization. The measured rates of clucking, cheeping and honking in adult chickens, young chicks and adult geese respectively are comparable to the characteristic rates of panting in these animals. This points to a similarity in the nature of the respiratory movements involved in each case. Simultaneous measurement of tracheal flow and pressure indicate that the glottis is capable of controlling air flow over a wide range of values in the presence of high pressures. During defaecation the valve is closed whilst during coughing it is wide open.
Electron Microprobe and Ion-Selective Microelectrode Studies of Fluid Secretion in the Salivary Glands of Calliphora
Authors: Gupta Brij L. , Berridge M. J. , Hall T. A. , Moreton R. B.
Published: April 2021

The concentrations of sodium, potassium, chloride and water in the cells, secretory canaliculi and the lumen of Calliphora salivary glands have been measured by microprobe analysis of frozen-hydrated sections. Free concentrations of K+ and Cl- in all three compartments were measured with ion-selective microelectrodes. Most of the quantitative data from the two techniques are in close agreement. Microprobe values for the cytoplasm are (mm kg−1 wet weight):Na 20, K 115, Cl 33 in unstimulated glands and Na 15, K 125, Cl 23 after stimulation with 10−8 M 5-hydroxytryptamine (5-HT). The water content is 85% and 77·5% respectively. The highest concentrations are found in the canaliculi. The results indicate that the fluid in the canaliculi is 60–80 m-osmol more concentrated, thus supporting the hypothesis that canaliculi are the sites of solute-water coupling by some form of local osmosis. Both the microprobe and microelectrode measurements show that 5-HT stimulation causes a rise in the level of intracellular potassium and a fall in that of chloride. On 5-HT stimulation there is a rise in the luminal concentrations of K and Cl and little change in sodium level. In K-free medium the potassium in all tissue compartments is replaced with sodium; nearly normal rates of fluid secretion are maintained. The possible routes for the entry of K, Cl and H2O into the canaliculi are discussed.
Acoustics of Sound Production and of Hearing in the Bladder Cicada Cystosoma Saundersii (Westwood)
Authors: Fletcher N. H. , Hill K. G.
Published: April 2021

The male cicada of the species Cystosoma saundersii has a grossly enlarged, hollow abdomen and emits a loud calling song with a fundamental frequency of about 800 Hz. At the song frequency, its hearing is non-directional. The female of C. saundersii lacks sound producing organs, has no enlargement of the abdomen, but possesses an abdominal air sac and has well developed directional hearing at the frequency of the species’ song.

Physical mechanisms are proposed that explain these observations in semi-quantitative detail using the standard method of electrical network analogues. The abdomen in the male, with its enclosed air, is found to act as a system resonant at the song frequency, thus contributing a large gain in radiated sound intensity. Coupling between this resonator and the auditory tympana accounts for the observed hearing sensitivity in the male, but destroys directionality. In the female, the abdominal cavity acts in association with the two auditory tympana as part of a phase shift network which results in appreciable directionality of hearing at the unusually low frequency of the male song.
Aspects of the Physiology of Terrestrial Life in Amphibious Fishes
Authors: Gordon Malcolm S. , Ng Wilson W.-s. , Yip Alice Y.-w.
Published: April 2021

Aspects of the physiological adaptations for terrestrial life possessed by the Chinese mudskipper fish, Periophthalmus cantonensis have been studied. The basic amphibious features were comparable to those found earlier in the East African mudskipper species, Periophthalmus sobrinus. The fish can survive for up to days out of water, under moderate environmental conditions, and did not drown in aerated water. Durations of voluntary periods out of contact with water, in nature, were short. Evaporative water loss rates while out of water were relatively low, substantially below those of frogs of much larger size. The ‘diving syndrome’ was absent, metabolic rates, heart rates, and blood lactic acid levels all being unaffected by shifts of fish between water and air. During slow desiccation of intact fish, water was lost from the internal organs in the following sequence (from greatest to least proportional water losses): heart, blood, white muscle, brain, liver. Rapid desiccations withdrew water from the blood and heart, leaving hydration levels of other organs unaffected. Metabolic rates were only moderately sensitive to temperature in the range 10° – 20 °C (Q10 ≅ 1·5), but were highly temperature sensitive in the range 20° – 30 °C (Q10 ≅ 2·6). Measurements of routine metabolic rates of fish in water indicate that active metabolism at 20 °C can reach at least 5 times the standard rate. Measurements of blood levels of ammonia and urea, and of ammonia and urea excretion rates, showed that starvation for 9·5 days did not affect blood levels of these compounds, but did reduce urea excretion rates by 40% below rates for recently fed fish. Ammonia excretion was unaffected. Similar measurements on fish starved for 9·5 days, then kept out of water for 16·5 h, then returned to water, indicated that waste nitrogen produced by fish out of water was retained in their bodies until they returned to water. Fish out of water produced waste nitrogen 40% less rapidly than fish in water, and strongly shifted toward ureotelism. These experiments, however, did not permit fish to retain and renew water in their mouths, as they would have done in nature. The water in mudskipper burrows was found to be anoxic or nearly so. Mudskipper tolerance for hypoxia was, however, limited. Fish became inert at dissolved oxygen levels of about 20% saturation.
Unusual Step Patterns in the Free Walking Grasshopper Neoconocephalus Robustus
Authors: Graham D.
Published: April 2021

The free walking step patterns of the tettigonid Neoconocephalus robustus are described and compared with the predictions of a model for walking co-ordination developed for the stick insect. Regular absences of rear leg protractions are found when the animal has walked for some minutes. The relative phasing of leg protractions before and after isolated absences suggests that an absence is created by a failure to meet all the conditions required for a protraction and that a ‘central oscillator’ maintains its intrinsic rhythm during such an absence.
Carbonic Anhydrase (Acetazolamide-Sensitive Esterase) Activity in the Blood, Gill and Kidney of the Thermally Acclimated Rainbow Trout, Salmo Gairdneri*
Authors: Houston A. H. , McCARTY L. S.
Published: April 2021

Gill, kidney and blood levels of acetazolamide-sensitive esterase (carbonic anhydrase) activity were estimated at acclimation temperature and at a common temperature (25°C) in rainbow trout acclimated to 2, 10 and 18 °C. Plasma levels of sodium, potassium and chloride were also examined for possible acclimatory variations. Plasma sodium and chloride levels, and the sodium: chloride ratio were unaffected by thermal acclimation; potassium concentrations were significantly elevated at 18°C. Significant, but modest changes in renal and branchial carbonic anhydrase activity were observed under physiologically realistic incubation temperature conditions. Blood carbonic anhydrase activity was sharply elevated at higher acclimation temperatures. The data are discussed in relation to the hypothesis that carbonic anhydrase in this relatively stenothermal freshwater salmonid, through its intimate association with the coupled and exchange systems may provide for relatively thermostable basal rates of sodium and chloride uptake from the medium and recovery from urine. The renal, and more notably the branchial (Na+/K+)-stimulated ATPase systems, and erythrocytic carbonic anhydrase may then serve primarily as high-temperature amplifiers of sodium and chloride recruitment respectively.
Intrinsic Rhythm and Basic Tonus in Insect Skeletal Muscle
Authors: Hoyle Graham
Published: April 2021

The jumping muscle of orthopterous insects contains fibres that possess an intrinsic rhythm (IR) of slow contraction. The contributing fibres are generally synchronized, but as many as three or four pacemakers are present. The frequency, amplitude and duration of IR contractions fluctuate erratically over a 24 h period. Metathoracic DUM neurone bursts suppress IR for a few minutes. Other, unidentified dorsal neurones enhance its amplitude. In addition to IR, the extensor tibiae shows intrinsic basic tonus (BT). BT is relaxed for several s by low-frequency burst output from unidentified metathoracic dorsal neurones. DUM neurone bursts may enhance extensor BT, relax it, or leave it unaffected.

The effects on IR of various regimes of activity in the slow extensor tibiae (SETi) and the common inhibitor (CI) axons were examined.

CI affects IR when stimulated at frequencies above 2 Hz. It causes amplitude depression and reduced duration of individual IR contractions as well as increased frequency. At 30 Hz and above, CI completely suppresses IR. An enhanced IR contraction starts within a few milliseconds of the termination of a CI train.

At low frequencies (below 10 Hz) SETi causes increased frequency and decreased amplitude of IR, with a depressed IR contraction following cessation of the SETi burst. At frequencies above 15 Hz the SETi-evoked contraction dominates tension development, though IR summates with it during the rising phase. In quiescent preparations not showing IR, SETi stimulation at 10 Hz often started up IR.

Single SETi or FETi impulses can initiate an IR contraction, and cause altered phasing, with up to a quintupling of frequency.

After a critical period has elapsed following the onset of an IR contraction, a single impulse in any one of the three axons will terminate it abruptly. The early termination is followed by a reduced interval which is proportional to the reduced IR contraction time. The rhythm of accumulated readiness to go into an IR contraction is independent of the pacemaker rhythm that initiates the contraction.
The Identification of An Octopaminergic Neurone and the Modulation of A Myogenic Rhythm in the Locust
Authors: Evans Peter D. , O’shea Michael
Published: April 2021

An octopaminergic neurone in an insect is demonstrated. This cell (DUMETi) is the dorsal unpaired median neurone which projects to the extensor tibiae muscle of the locust metathoracic leg. Its soma was physiologically identified, isolated and shown to contain about 0·1 pmol of octopamine. Octopamine is about four times more concentrated in the axon than in the soma. The concentration in the soma is at least 800 times more than that in the soma of an identified motoneurone (which controls the fast extensor of the tibia). The effects of DUMETi on a myogenic rhythm in the extensor muscle of the locust metathoracic leg can be mimicked by superfusion with low concentrations of octopamine. The myogenic bundle possesses at least two types of aminergic receptor: one which slows the rhythm (and has a high-affinity for octopamine) and a second which accelerates the rhythm (and has a low-affinity for octopamine but a high-affinity for the indolalkylamine, 5-hydroxytryptamine). The roles of the two receptor types in modulating the rhythm are discussed in relation to the function of the rhythm.
Endothermy in African Dung Beetles During Flight, Ball Making, and Ball Rolling
Authors: Bartholomew George A. , Heinrich Bernd
Published: April 2021

Body temperatures of diurnal and nocturnal ball-rolling and non ball-rolling dung beetles (in particular the genera Scarabaeus, Kheper, Gymno-pleurus and Heliocopris) were studied in the field in Kenya. The beetles were conspicuously endothermic during flight, ball making, and ball rolling. When at rest, their body temperatures did not differ significantly from that of their surroundings. They did not always generate high body temperatures while walking. However, they sometimes warmed up prior to walking and subsequently maintained a large difference between body and ambient temperatures. The nocturnal species, 5. laevistriatus, was conspicuously endothermic during ball making and ball rolling, often maintaining thoracic temperatures of 40°C or more in an ambient temperature of 25−26°C. In this species, the velocity of ball rolling increased linearly with body temperature from 5 cm/sec at 28°C to 18 cm/sec at 40°C. The take-off temperatures of dung beetles increased with body mass up to 2·5 g. In beetles larger than 2·5 g metathoracic temperatures at take-off ranged from 40 to 44°C and were independent of mass. Flight temperatures showed essentially the same pattern as take-off temperatures, increasing with mass up to about 42°C at 2·5 g and being independent of mass thereafter. Both flight and take-off temperatures increased with wing-loading up to about 35 N/m2, but were independent of wing loading from 35 to 65 N/m2. In each of the species for which we had an adequate sample, wing loading increased linearly with body mass. Partial correlation analysis suggests that metathoracic temperature is more dependent on body mass than on wing-loading. During periods of endothermy, metathoracic temperature exceeded prothoracic temperature, and abdominal temperature was lower than that of either the prothorax or metathorax. Cooling rate was inversely related to body mass. The removal of elytra and wings caused the cooling rate to increase by about one-quarter. Elevated body temperatures in dung beetles during terrestrial activity is probably selectively advantageous in competition for food. A high metathoracic temperature is a necessary condition for take-off and flight in the larger species. Mechanisms of heat production and the evidence for thermoregulation are discussed.
Pharmacological Study of the Reciprocal Dual Innervation of the Lateral Ciliated Gill Epithelium by the Cns of Mytilus Edulis (Bivalvia)
Authors: Catapane Edward J. , Stefano George B. , Aiello Edward
Published: April 2021

The function of the CNS of Mytilus edulis was investigated for its role in the control of lateral ciliary activity. Ciliary beating rates were directly measured by stroboscopic microscopy of gill preparations which had the ipsilateral visceral ganglion (VG) attached. Low frequency electrical stimulation of the cerebrovisceral connective (CVC) or superfusion of the VG with serotonin increased lateral ciliary activity. This response could be antagonized by pretreating the gill with BOL or methysergide (MS), or by pretreating the VG with BOL, MS or ergonovine (ERG). High frequency stimulation of the CVC or superfusion of the VG with dopamine or epinephrine decreased lateral ciliary activity. This response could be antagonized by pretreating the gill with ERG or by pretreating the VG with ERG or MS. Acetylcholine and its mimetic acetylmethylcholine were found to be non-effective in altering ciliary activity in this study. The study demonstrates a reciprocal serotonergic-dopaminergic innervation of lateral gill ciliated cells originating in the CNS.
The Effect of Training on the Swimming Muscles of the Goldfish (Carassius Auratus)
Authors: Davison William , Goldspink Geoffrey
Published: April 2021

Goldfish (Carassius auratus) were exercised continuously for periods of 28 days at swimming speeds of 1·5, 3·0 and 4·5 body lengths per second and their rates of growth were determined. Changes in muscle fibre size were examined, as were changes which occurred in the concentrations of the major chemical constituents of these cells.

These fish, typical of the carp family in that they are found only in still or slowly moving water, did not adapt well to the flowing water environment at any swimming speed. They often grew less than the controls, although consuming much more food. Changes in the composition of the muscle fibres indicated that excess food was not being stored, and also indicated that the major fuel for swimming at all speeds was glycogen. The fish survived well at high speeds and it was suggested that this was due to the ability of the species to metabolize glycogen anaerobically without the production of lactic acid.
Internal Volume and Pressure Regulation in Carcinus Maenas
Authors: Norfolk J. R. W.
Published: April 2021

In Carcinus, in dilute media, internal volume and pressure were found to be regulated by the intermittent release of urine which maintained internal pressure at a mean value of 15 cm water, compared to a mean value of 10 cm for crabs in sea water. Following transfer of crabs from 100 % to 50% sea water, urine production (measured by a continuous collection method) was observed to increase within 5 min of dilution of the medium, by which time the estimated increase in internal pressure would have been only 1·3 cm water. Such a pressure increase is considered inadequate to stimulate a rise in urine production, since artificially raising internal pressure of crabs in sea water did not result in an increase in urine flow, until the pressure was in excess of 20 cm water.

The results support the hypothesis that the stimulus to increase urine production by crabs in dilute media is not raised internal pressure due to osmotic influx of water. An alternative hypothesis, namely that of changes in urine production being in response to direct monitoring of the external environment, is suggested.
The Optokinetic Basis of Head-Bobbing in the Pigeon
Authors: Frost B. J.
Published: April 2021

Head-bobbing of pigeons during walking and landing was studied using high-speed motion photography. The analysis of film records indicated that head-bobbing whilst walking consists of two phases: one where the head is ‘locked’ in space but moves backward relative to its forward moving body; and another where it is thrust rapidly forward to a new position. The fact that head-bobbing is abolished when pigeons walk on a treadmill suggests it is primarily a visual response rather than an equi-libratory response. Data are presented which show that stabilization during the ‘lock’ phase allows a small degree of slippage which is the probable source of error signals for compensatory head movements. The head-bobbing that appears to occur during landing is shown to be illusory.
The Effect of Hypertonic Solutions on The Rate of Relaxation of Contracture Tension in Mytilus Smooth Muscle
Authors: Tameyasu T.
Published: April 2021

The effect of the bathing solution tonicity on the mechanical properties of the anterior byssal retractor muscle (ABRM) of Mytilus edulis was examined. The rate of relaxation of contracture tension produced by acetylcholine (ACh) was greatly reduced when the bathing solution tonicity was increased by adding NaCl, KC1 or LiCl after the removal of ACh, whereas a decreased tonicity increased the rate of relaxation. The contracted ABRM in hypertonic solutions showed no active shortening after an isotonic release and barely redeveloped active tension after a quick release. The resistance to stretch increased with increasing tonicity of the bathing solution. The wet weight of the ABRM decreased much more markedly in sucrose-hypertonic solution than in Na-, K- or Li-hypertonic solutions, but the decrease in the rate of relaxation was less marked in the former, indicating that there may be little relation between the rate of relaxation and the degree of osmotic deformation of the ABRM fibres. It is suggested that the elevated ionic strength in the myoplasm may be related to a reduction in the rate of detachment of the cross-linkages between the thick and thin filaments.
Respiratory and hydrostatic functions of the intestine of the catfishes Hoplosternum Thoracatum and Brochis Splendens (Callichthyidae)
Authors: Gee John H. , Graham Jeffrey B.
Published: April 2021

The air-breathing behaviour of Hoplosternum thoracatum and Brochis splendens has been studied and their strategy of coordinating the respiratory and hydrostatic functions of the accessory respiratory organ has been examined. H. thoracatum and B. splendens are continuous but not obligate air-breathers and individuals of the former breathe air in synchrony with each other. Frequency of air-breathing increased with increased activity in H. thoracatum. Aquatic respiration (Vo2) in H. thoracatum decreased in hypoxic water but aerial Vo2 maintained a fairly constant total Vo2 independent of aquatic O2. Total Vo2 is higher when fish breathe both air and water but aerial Vo2 did not exceed 75% of total Vo2. The accessory respiratory organ provides about 75% of the lift required to attain neutral buoyancy whereas the swimbladder provides less than 5%. The mean decreases in volume of the accessory respiratory organ in the period between breaths of B. splendens and H. thoracatum were 13.2 and 7.8% respectively. With a gas phase of O2, B. splendens maintained a similar frequency of air breathing and showed a slightly greater reduction in buoyancy between air breaths when compared to breathing air. With a gas phase of N2, air breathing was less frequent and decreases in buoyancy between air breaths were much less than when breathing air. The respiratory and hydrostatic functions of the accessory respiratory organ are compatible. Buoyancy is maintained by frequent air breaths taken in part in response to a decrease in volume of the accessory respiratory organ. This reservoir of O2 could increase metabolic scope during bursts of activity.
Kinetics of Sodium and Lithium Movements Across the Blood-Brain Barrier of An Insect
Authors: Schofield P. K. , Treherne J. E.
Published: April 2021

The electrical responses of axons were used to monitor the time-course of a change in the concentration of an ion species in the fluid bathing the axons in connectives of isolated cockroach nerve cords. Initial exposure of the connectives to sodium-deficient Ringer resulted in a depletion of extra-axonal sodium which was much slower than the restoration observed on return of the sodium Ringer. It is suggested that this asymmetry could result from a sodium reservoir which delays the initial decline. Subsequent net inward and outward movements of sodium ions were rapid and symmetrical. Unlike sodium ions, lithium ions were apparently unable to reach the axon surfaces following sodium depletion. In view of the similar properties of sodium and lithium ions in many biological systems it is therefore unlikely the the sodium movements were passive. Instead, the results support the idea of net sodium transport by the perineurial and/or glial elements.
The Role of the Thermal Hysteresis Factor in Tenebrio Molitor Larvae
Authors: Patterson Jean L. , Duman John G.
Published: April 2021

The haemolymph of larvae of Tenebrio molitor contains a factor which produces a thermal hysteresis (a difference between the freezing and melting points) of approximately 0·75 °C. When larvae were acclimated to low temperatures or short photoperiod the thermal hysteresis increased more than twofold. Coincident with the increase in thermal hysteresis the supercooling points and lower lethal temperatures of the larvae were depressed. Therefore, the thermal-hysteresis-producing factor seems to function as an antifreeze.

The factor may also act as an adaptation to prevent desiccation. Thermal hysteresis increased almost three-fold in larvae acclimated to low relative humidity. Also, larvae with high levels of the thermal hysteresis factor survived low relative humidities much better than did larvae with lower levels.
Mating Call Recognition in the Green Treefrog (Hyla Cinerea): The Significance of Some Fine-Temporal Properties
Authors: Gerhardt H. Carl
Published: April 2021

Two hundred and eighty-eight female green treefrogs responded in two-choice experiments using synthetic calls. The spectral properties of the sounds were similar ; the fine-temporal properties were systematically varied. Females preferred sounds in which the waveform periodicity was about 300/s, a rate typical of natural mating calls. They discriminated strongly against calls with periodicities of 100/s, 60/s and 50/s. Aperiodic calls and calls with periodicities of 225/s and 900/s were intermediate in attractiveness. The results of four experiments indicated that periodicity preferences depended on corresponding changes in the amplitude-time envelopes of the signals. Neurophysiological correlations and the implications of the behavioural results are discussed. The biological significance in species recognition and in the differentiation of the mating call from other signals in the repertoire of the green treefrog is discussed.
The Effect of Calcium and Magnesium on the Spontaneous Release of Transmitter At Insect Motor Nerve Terminals
Authors: Washio H. M. , Inouye S. T.
Published: April 2021

The effect of the extracellular calcium and magnesium concentrations and calcium ionophore, X-537A, on the frequency of miniature excitatory post-synaptic potentials (MEPSPs) was studied in cockroach leg muscle fibres. The frequency of MEPSPs increased as the calcium concentration was increased from 0·1to 10 mM In the presence of 10 mm magnesium, how-ever, raising the calcium concentration from 0·1to 1 mM slightly depressed the frequency. In saline containing elevated potassium (20·8 mm), increasing the calcium concentration produced a much higher frequency than that in the normal potassium saline (10·8 mm) in the absence of magnesium. Raising the extracellular potassium concentration was without effect unless the bathing solution contained calcium. The frequency of the miniature potentials was reduced as the magnesium concentration was raised from o to 10 mM, depending on the presence of calcium ions. On the contrary, a slightly increased frequency was observed in the low calcium saline as the magnesium concentration was raised from 1 to 10 mM. The reciprocal relationship between calcium and magnesium and the time course of the effect suggest that both ions act at the same surface sites in the presynaptic membrane. X-537A elicited a transient increase in frequency followed by a fall of the frequency to a very low rate. Further application of the ionophore was without effect. The effect of X-537A on the spontaneous release of transmitter at the insect neuromuscular junction was comparable with that on the spontaneous acetylcholine release in vertebrate neuromuscular junctions.
Effects of the Non-Protein Amino Acids L-Canavanine and L-Canaline on the Nervous System of the Moth Manduca Sexta (L.)
Authors: Kammer Ann E. , Dahlman D. L. , Rosenthal Gerald A.
Published: April 2021

Injection of L-canavanine, a naturally occurring arginine analogue, and of its metabolic derivative, L-canaline, induced almost continuous motor activity in adult tobacco hornworms, Manduca sexta (L.). Initially the moths flew normally, but after a time interval that depended both on the amino acid and on the dose (1−45 μmol/g fresh weight) the moths became disorientated and muscle activity was less patterned. Canaline produced its initial effects 12−30 min after injection, whereas activity in response to canavanine began after a delay of 1−2 h. Canaline (derived from canavanine by an arginase-mediated hydrolytic cleavage) is probably the biologically active factor.

Canaline did not affect axonal conduction of action potentials nor the activity of mechanoreceptors on the forewing. Canaline (22μmol/g fresh weight) prolonged the postsynaptic potential of flight muscle fibres, but after 20−40 min. the electrical activity of muscle fibres was normal. The results show that canaline alters the activity of the central nervous system of adult M. sexta, but its mode of action is unknown.
Control of Salivation in the Blowfly Calliphora
Authors: Bay Christina M. Hansen
Published: April 2021

A technique has been developed for collecting saliva from the salivary duct of flies during feeding. In newly emerged flies salivation is evoked by stimulation of the labellar taste papillae by crystalline sugar, by sugar in solution and by water. Only sugars which excite the sugar receptors are effective. In flies which have previously fed, solid sucrose or meat induce regurgitation of the crop contents, or salivation if the crop is empty. Sucrose in solution provokes neither reaction. Saliva always contains digestive enzymes, even if the ingested food requires no digestion. Blood taken from salivating flies stimulates fluid secretion from isolated glands, whereas blood taken from non-salivating flies is ineffective. Section of the cephalo-thoracic nerve cord abolishes salivation in response to feeding. Section of the ventral nerve cord posterior to the thoracic ganglion, or removal of the abdomen, severely reduces but does not abolish the salivatory response. Saliva secreted by mature flies contains 75 mm-Cl− whereas saliva secreted during the first meal after emergence has a higher Cl− concentration (about 165 mm-Cl−) which gradually declines during the first meal.
Neuronal Control of Swimming in the Medicinal Leech
Authors: Poon Margaret , Friesen W. Otto , Stent Gunther S.
Published: April 2021

A network of intra- and intersegmental synaptic connexions has been identified in the ventral nerve cord of the leech that links the set of oscillatory interneurones of the central swim oscillator to the motor neurones commanding the swimming rhythm. Excitatory connexions lead from oscillatory interneurones to both excitatory and inhibitory motor neurones, whereas inhibitory connexions lead from oscillatory interneurones to only the inhibitory motor neurones. Connexions leading from a motor neurone back to the oscillatory interneurones were found in only one exceptional case, an inhibitory motor neurone previously known to have access to the central swim oscillator. This network of identified connexions can account reasonably well for the mechanism by which the oscillatory interneurones drive their follower motor neurones into the phasic activity pattern characteristic of the swimming movement.
Regulation of Arterial Blood Pressure in Australian Tiger Snakes
Authors: Lillywhite Harvey B. , Seymour Roger S.
Published: April 2021

Blood pressure was measured in the dorsal aorta of restrained, un-anaesthetized tiger snakes (Notechis scutatus) at different body temperatures during graded, passive tilt. Aortic blood pressure in horizontal snakes showed no significant change over a range of body temperatures between 18 and 33 °C (mean of measurements on 16 snakes = 42·2 ± 1·98 mmHg), while heart rate increased logarithmically (Q10 approximately 2·5). Blood pressure was stable during heating and cooling between body temperatures of 15 and 30 °C, but the pressure was 10–50% higher during heating than during cooling. Head-up tilt usually caused a brief fall in pressure at heart level followed by partial or complete recovery and tachycardia. At the cessation of tilt, there was a characteristic overshoot of the blood pressure followed by readjustment to control (pretilt) levels. Head-down tilt typically increased pressure which then either stabilized or returned toward pretilt levels. Heart rate changes during head-down tilt were not consistent in direction or magnitude. Stabilized pressures at mid-body usually increased following head-up tilt and decreased following head-down tilt, indicating physiological adjustment to posture change. Blood pressure control was evident at body temperatures ranging from 10 to 38 °C, but was most effective at the higher and behaviourally preferred temperatures. Propranolol lowered heart rate but did not influence pressure in horizontal snakes. During head-up tilt propranolol eliminated or reduced tachycardia and sometimes reduced the efficacy of pressure compensation for tilt. Phentolamine increased heart rate, lowered blood pressure, and eliminated pressure regulation during tilt. The results suggest that sympathetically mediated reflexes assist central blood pressure regulation in the tiger snake, with vasomotor adjustments having greater importance than changes in heart rate.
How The Locust Dries Itself
Authors: Pflüger Hans-Joachim , Burrows Malcolm
Published: April 2021

All wet locusts perform a series of specific behavioural acts to rid their body of water. These acts included fluttering the wings, kicking with the hind legs and grooming the eyes and antennae. Any one act can follow another, although wing fluttering, walking and hind leg kicking are closely associated. Some locusts may omit a particular movement in some sequences of drying behaviour. All the movements remove water from the body presumably to allow the correct functioning of the sense organs, or to prevent evaporative cooling.
Static Pressure-Volume Curves for the Lung of the Frog (Rana Pipiens)
Authors: Hughes G. M. , Vergara G. A.
Published: April 2021

Static pressure/volume curves have been determined for isolated frog lungs inflated with either air or saline. In both cases a hysteresis was present: the pressure required to produce unit change of volume being greater during inflation than deflation. The pressure necessary for a given volume change was less for the saline-filled than the air-filled lungs. The difference between these curves is due to the surface tension at the air/lung interface. Pressure/volume curves for air-filled lungs in situ were similar to curves for isolated lungs. However, a greater pressure was required for the same volume change during both inflation and deflation. Compliance was calculated from different parts of air pressure/volume curves and gave values greater than those obtained using similar calculations for higher vertebrates. These observations support other evidence for the presence of a surfactant in the lung lining of frogs in spite of the relatively large diameter of their ‘alveoli.’ The precise role of such a lining is uncertain and it is concluded that similar forces may be involved during the inflation and deflation of lungs of frogs and higher vertebrates in spite of differences in gross morphology.
Axonal Adaptations to Osmotic and Ionic Stress in An Invertebrate Osmoconformer (Mercierella Enigmatica Fauvel)
Authors: Skaer H. Le B. , Treherne J. E. , Benson J. A. , Moreton R. B.
Published: April 2021

The giant axons in Mercierella are overlaid by narrow glial processes which provide an incomplete covering of the axonal surface. Where more complete covering occurs the intercellular clefts are not sealed by tight junctional complexes. Ionic lanthanum penetrates to the surfaces of axons from sea-water-adapted animals (in normal saline and during initial exposure to hyposmotic saline) and, also, to the surface of hyposmotically adapted axons. A relatively free intercellular access to the axon surfaces is also indicated by the rapid electrical responses of sea-water-adapted axons to hyposmotic dilution and of hyposmotically adapted axons to sodium-deficient saline. The giant axon possesses an unusual ultrastructural specialization: hemidesmosome-like structures (associated with the axon membrane) which are connected to a network of neurofilaments within the axon. Theoretical considerations suggest that these structures could enable the axons to withstand appreciable excesses in intracellular hydrostatic pressure resulting from osmotic imbalance during hyposmotic stress.
Short Communication
Authors: Collett T. S.
Published: April 2021

Motion parallax is probably the most important method available to insects for judging the distance of objects, yet with one exception very little is known about the ways in which insects exploit this cue. Almost twenty years ago Wallace (1959) proposed that the side-to-side peering movements of juvenile locusts are performed specifically to obtain parallax information. Leg movements cause the whole body to pivot about the abdomen, shifting the head laterally about 0·5 cm and displacing the retinal image of an object in front of the insect. Provided that the locust knows how far (or fast) it moves its head and that it can measure image displacement (or velocity) it can compute the distance of the object (Fig. 1 a). The following suggests locusts do indeed do something of this kind. When an object on to which a locust is about to jump is moved horizontally in a frontal plane, in synchrony with peering, locusts are fooled into misjudging the object’s distance. For instance, if the object is moved in the opposite direction to that in which the locust peers, so enhancing image movement, the locust jumps short (Wallace, 1959).
The Tymbal Mechanism and Song Patterns of the Bladder Cicada, Cystosoma Saundersii
Authors: Simmons Peter , Young David
Published: April 2021

In Cystosoma saundersii sound is generated by collapse of a pair of tymbals and radiated by a large, resonant, air-filled abdomen. Each tymbal comprises a flexible, biconvex membrane bearing seven long ribs. Tymbal collapse is caused by contraction of a large tymbal muscle, which acts on the tymbal plate. Each tymbal muscle is innervated by one motor neurone. A single collapse of a tymbal produces two distinct pulses of sound, one when rib 1 buckles and one when ribs 2–4 buckle. A quieter sound is produced when the ribs click outwards. A slowly contracting tensor muscle increases the convexity and stiffness of the tymbal, resulting in a reduction in the delay between the first and second sound pulse and in louder pulses. Protest songs contain features of other songs. There is a delay between the spike in one tymbal motor neurone and its partner, and hence between sound produced by one tymbal and the other, of one-quarter of the interval between spikes in one motor neurone alone. Calling songs are produced by males at dusk. Sound pulses have a smooth envelope and are very loud as a result of contraction of the tensor muscles and extension of the abdomen. Courtship songs are triggered in a calling male by the presence of a female. Song is quite quiet, and broken into short chirps.
A Quantitative Analysis of Flagellar Movement in Echinoderm Spermatozoa
Authors: Hiramoto Yukio , Baba Shoji A.
Published: April 2021

Computerized analyses were performed on the movement of spermatozoa recorded with a high-speed camera. These provide evidence for active bending waves over the entire length of the flagellum and a single equation for waves in all cases examined. In the equation, the angular direction of the flagellum at any distance from the base is expressed by a sine function of time plus a constant, and thus flagellar waves are ‘sine-generated’. To explain the waves a model was proposed in which the active force required to generate sliding between peripheral microtubules is propagated along and around the flagellar axoneme.
Volume Regulation and Solute Balance in the Nervous Tissue of An Osmoconforming Bivalve (Mytilus Edulis)
Authors: Willmer P. G.
Published: April 2021

Mytilus edulis could be adapted to salinities between 25% and 125% under laboratory conditions, with complete ionic and osmotic conformity of the body fluids. Extracellular space, intracellular cation concentrations and water content were determined for the cerebro-visceral connectives of Mytilus adapted to either 100% or 25% salinity. These measurements suggested only a moderate degree of volume regulation (as indicated by relative cell hydration) and net losses of both potassium and sodium from the cells during acclimation to dilute sea water, although neither cation was reduced in proportion to the external concentrations. Measurement of actual volume changes during acute hyposmotic stress indicated a greater capacity for volume control in the 25 %-adapted connectives. However, these tissues also showed an increment of 11% in initial diameter, suggesting significant chronic swelling of the cells. Fine-structural studies of Mytilus nerve indicated that the apparent swelling of the dilute-adapted tissues resulted from a roughly threefold thickening of the ensheathing neural lamella due to the deposition of extra collagen-like fibrils, with the axons in fact showing negligible volume increase. The connectives thus appear to exhibit almost perfect volume regulation. To account for the conflicting estimates of volume regulating capacity, it is proposed that the cells are hyperosmotic to their environment at 25 % salinity, the hydrostatic gradient thus created being countered by the restraint imposed by the thickened neural lamella. Physical stresses on the excitable membranes of the nerve would thus be minimized, and electrophysiological functioning in dilute media would be facilitated.
Measurements of the Osmotic Concentrations of Stylet Sap, Haemolymph and Honeydew from An Aphid Under Osmotic Stress
Authors: Downing N.
Published: April 2021

The osmoregulatory physiology of aphids is poorly understood, yet it is such small terrestrial insects that face the severest osmotic problems. The lack of progress in this field reflects not only the difficulty of working with insects of such a small size but also the difficulty of obtaining samples of the sap on which they feed.
Initiation, Maintenance and Modulation of Swimming in the Medicinal Leech by the Activity of A Single Neurone
Authors: Weeks Janis C. , Kristan William B.
Published: April 2021

A neurone (designated cell 204) has been identified in the segmental ganglia of the leech which, when stimulated intracellularly in isolated nerve cords, reliably initiates and maintains the neuronal activity pattern characteristic of swimming. In a minimally dissected leech, cell 204 activity results in normal swimming movements. Cell 204 is an unpaired, intersegmental interneurone which is present in most, if not all, of the segmental ganglia. Horseradish peroxidase injections indicate that cell 204 has extensive arborizations in its own ganglion and sends an axon both anteriorly and posteriorly via Faivre’s Nerve. Cell 204 is normally quiescent, but during swimming activity becomes depolarized and produces impulse bursts in the ventral contraction phase of its own segment. Such activity is observed in every cell 204 in the nerve cord and is independent of the stimulus used to evoke the swimming episode. Activity in any cell 204 is sufficient for initiation and maintenance of swimming activity, whereas activity in any two of them is not necessary for swimming. During swimming activity, imposed increases in the impulse frequency of any cell 204 cause a decrease in the swim cycle period of the entire nerve cord. Tactile stimulation of the skin, which is an effective method of eliciting swimming episodes, excites cell 204. Our findings indicate that cell 204 may activate swimming in the intact leech.
Directional Sensitivity in A Crayfish Mechanoreceptive Interneurone: Analysis by Root Ablation
Authors: Flood Patricia M. , Wilkens Lon A.
Published: April 2021

Within the hierarchy of sensory interneurones in the crayfish, individual cells exist which code specifically for directional components of waterborne stimuli. The caudal photoreceptor interneurone (CPR) exhibits this mechanoreceptive response pattern, in addition to its primary light response. However, despite some variability the CPR is bidirectional, responding to water currents in both rostral and caudal directions. The peripheral mechanoreceptive fields providing input to the CPR have been examined, using selective root ablation procedures. Receptors from the exopodite and from the distal portion of the telson are the primary sources of input, this being carried by the 2nd and 5th roots respectively of the caudal ganglion. Input from the ipsilateral roots is normally excitatory; input arising contralaterally has an inhibitory influence. Populations of mechanoreceptors presynaptic to the CPR appear to be segregated in terms of the directional information encoded by the CPR. Specifically, ablation of the 2nd ipsilateral root decreases caudal sensitivity predominantly, whereas ablation of the 5th ipsilateral root primarily decreases rostral sensitivity. Therefore, only primary sensory cells which originate from the exo-podite, and respond to caudal deflexions of the hair shaft, effectively excite the CPR. Similarly, only the sensory cells originating from the telson which are responsive to anterior deflexions appear to effectively excite the CPR.
Intracellular Oxidation-Reduction Studies
Authors: Chambers Robert , Cohen Barnett , Pollack Herbert
Published: April 2021

In a number of studies on the reduction potentials of living tissues and cells, the method of immersing the material under investigation in solutions of oxidation-reduction indicators has found considerable employment. Under controlled conditions and with sufficient knowledge concerning the physico-chemical characteristics of the indicator systems, this method is of value for determining the magnitude of extracellular reduction potentials. Its use, however, for the determination of intracellular reduction potentials has been hampered by the lack, among other things, of knowledge concerning the penetrating power of the indicators into living cells. Results obtained from immersion experiments alone have proved to be inconsistent. An example of this is given by J. and D. Needham (1) who examined a series of indicators and showed that cells become coloured when immersed in solutions of indicators which should be reduced intracellularly, while they give no sign of coloration in solutions of other indicators which should remain oxidised. These authors recognised the discrepancy but did not examine it more thoroughly.
The Adaptation of Gunda Ulvae to Salinity
Authors: Weil E. , Pantin C. F. A.
Published: April 2021

Gunda ulvae is a small triclad which lives in estuaries between tide marks. It is surrounded by a medium which normally varies from completely fresh water to undiluted sea water: to either of these extremes the worm may be exposed for several hours at each tide. An account of its environment has been given in the previous paper (Pantin, 1931). The worms survive many months in sea water in an aquarium, but will not survive indefinitely in fresh water.
A Sensitive Recording (Transpiration) Balance With A New Form of Electrically Operated Recorder
Authors: Jones W. Neilson
Published: April 2021

A number of instruments for automatically registering the loss of weight of a plant during transpiration have been devised, the best known, perhaps, being those described by Ganong (1905) and by Blackman and Paine (1914). In both these instruments the experimental plant is placed on one pan of a special balance, equivalent weights are added to the other pan, and the balance is kept in equilibrium by the addition of known weights at intervals as required to compensate for the loss of water during transpiration, each addition being recorded by an electrical device.
The Senescence of Spermatozoa, II
Authors: Gray J.
Published: April 2021

In a recent paper (Gray, 1928 a) the progressive loss of activity of a suspension of Echinus sperm was considered from two points of view; firstly, as a process of spontaneous and irreversible depletion of available energy and secondly, as a process of auto-intoxication whereby the products of activity inhibit the essential reactions of life. Both of these hypotheses led to a quantitative relationship between the total oxygen absorbed by a suspension and the period of time which had elapsed since the beginning of active life. This relationship was, in both cases, in harmony with that recorded by experiment, so that it is only possible to judge the relative merits of the two hypotheses by the intrinsic probability of the underlying assumptions, or by the provision of more specific data. An attempt to provide such data has proved detrimental to both theories.