bluuebunny/crossref_metadata_2025 huggingface dataset:
Locomotor Performance and Energetic Cost of Sidewinding by the Snake Crotalus Cerastes
Authors: Secor Stephen M. , Jayne Bruce C. , Bennett Albert F.
Published: April 2021

We measured the performance (burst speed and endurance) and the energetic cost of sidewinding locomotion for the viperid snake Crotalus cerastes. The linear scaling regressions relating log mass to log burst speed and log endurance have slopes of 0.29 and 1.01, respectively. Maximal burst speed observed for an individual snake (SVL=41.9cm, SVL is snout-vent length) was 3.7 km h1. Adult snakes were able to match a tread speed of 0.5 km h−1 for times ranging from 33 to more than 180 min, and at 0.7 km h−1 endurance times ranged from 9 to 52 min. Rates of oxygen consumption increased linearly over a range of aerobically sustainable speeds (0.28−0.50 km h−1), with a resulting net cost of transport (NCT) of 0.408 ml O2g−1 km−1 for eight snakes with a mean mass of 110g. Sidewinding of C. cerastes involves periodic movements with a frequency that increases linearly with mean forward speed. At 0.50 km h-1, the mean (N=8) mass-specific energetic cost per cycle of movement was 0.28μl O2g−1cycle−1 for sidewinding. The NCT and the cost per cycle of movement of C. cerastes sidewinding are significantly less than those of similar mass snakes (Coluber constrictor) performing either terrestrial lateral undulation or concertina locomotion. The NCT of C. cerastes sidewinding is also significantly less than that predicted for the terrestrial limbed locomotion of lizards of similar mass. Mean C. cerastes (0.405 ml O2g−1h−1) is only about half that reported for C. constrictor; however, the mean endurance at 0.60 km h−1 (73 min) for sidewinding C. cerastes does not differ significantly from that reported for C. constrictor laterally undulating.
The Effects of Temperature on the Oxygen Consumption, Heart Rate and Deep Body Temperature During Diving in the Tufted Duck Aythya Fuligula
Authors: Bevan R. M. , Butler P. J.
Published: April 2021

Six tufted ducks were trained to dive for food at summer temperatures (air, 26°C, water, 23°C) and at winter temperatures (air, 5.8°C, water 7.4°C). The mean resting oxygen consumption at winter temperatures (Twin) was 90% higher than that at summer temperatures (Tsum), but deep body temperatures (Tb) were not significantly different.

Diving behaviour and mean oxygen consumption for dives of mean duration were similar at Twin and at Tsum, although the mean oxygen consumption for surface intervals of mean duration was 50% greater at Twin and Tb was significantly lower (1°C) at the end of a series of dives in winter than it was in summer.

There appears to be an energy saving of 67 J per dive during winter conditions and this may, at least partially, be the result of the metabolic heat produced by the active muscles being used to maintain body temperature. While at rest under winter conditions, this would be achieved by shivering thermogenesis. Thus, the energetic costs of foraging in tufted ducks in winter are not as great as might be expected from the almost doubling of metabolic rate in resting birds.
Proprioceptive Input From two Basal Joint Stretch Receptors to Leg Motoneurones in the Isolated Thoracic Ganglion of the Shore Crab
Authors: Head Stewart I. , Bush Brian M. H.
Published: April 2021

The reflex effects and interactions of two proprioceptors upon motoneurones supplying the four basal leg muscles of the shore crab Carcinus maenas have been studied in a new in vitro preparation consisting of the thoracic-coxal muscle receptor organ (TCMRO) and the coxo-basal chordotonal organ (CBCO) isolated together with the whole thoracic ganglion complex to which they were still connected by their afferent nerves. Each receptor strand was stimulated mechanically, while recording intracellularly from motoneurones in the ganglion, and extracellularly from the cut motor nerves innervating the promotor and remotor muscles of the thoracic-coxal (T–C) joint and the levator and depressor muscles of the coxo-basal (C–B) joint.

Stretch of the TCMRO evoked reflex firing in several units in the promotor motor nerve, confirming previous studies. In addition to this ‘intrajoint’ reflex, however, TCMRO stretch also elicited ‘interjoint’ reflex responses in moto-neurones of both the levator and depressor muscles. Similarly, stretch and release of the CBCO produced intrajoint resistance reflexes in levator and depressor motoneurones, respectively, as well as interjoint reflexes in promotor and remotor motoneurones. In general, the CBCO produced stronger reflex effects in all four motor nerves than did the TCMRO.

Intracellular recordings from individual motoneurones of all four muscles revealed that the majority of them received convergent input from both proprio-ceptors. The importance of such convergent input in vivo is discussed.
Humoral Induction of Pyloric Rhythmic Output in Lobster Stomatogastric Ganglion: In Vivo and In Vitro Studies
Authors: Rezer Elizabeth , Moulins Maurice
Published: April 2021

In the lobster Jasus lalandii, 14 neurones of the stomatogastric ganglion (STG) are organized in a network that produces rhythmic pyloric outputs. In vitro experiments have shown that the STG neurones receive, via the stomatogastric nerve (stn), neuromodulatory inputs that influence the expression of the bursting properties of the neurones and the ability of the network to produce its rhythmic output.

In contrast to these in vitro observations, in vivo transection of the stn does not abolish the pyloric rhythm. Rhythmic output can be recorded by electromyogra-phy immediately after stn transection and for up to 2 years afterwards. We have shown that, under these experimental conditions, the STG appears to be isolated from any neuronal input that might account for the maintenance of the rhythmic output. Experiments carried out in the 2 days after stn transection showed that an in vitro preparation of the isolated STG was unable to produce any rhythmic output, but blood serum added to the system could restore the pyloric output.

These results suggest strongly that the pyloric network receives neural and humoral modulatory influences in parallel and that each type of influence alone is able to maintain the bursting capability of the pyloric neurones.
The Influence of Temperature on Muscle Function in The Fast Swimming Scup: II. The Mechanics of Red Muscle
Authors: Rome Lawrence C. , Sosnicki Andrzej , Choi In-Ho
Published: April 2021

To understand better how scup can swim twice as fast as carp with its red muscle, we measured the mechanical properties of red muscle bundles in scup. The values of the mean maximum velocity of shortening (Vmax) at 10°C (3.32musclelengthss−1) and at 20°C (5.55 muscle lengths s−1 ; Q10=1.69) were nearly the same as those in carp. Isometric force, however, was approximately 50% greater (183 kN m− 2; Q10 =1.08). The maximal power generation was correspondingly about 50% greater in scup than in carp (71 Wkg−1 at 10 °C and 134Wkg−1 at 20°C; Q1O=1.88). The larger power output of its muscle may be important in the faster swimming of the scup. In addition, the fact that scup use a less undulatory style of swimming means that, when they are swimming twice as fast, their red muscle shortens at the same velocity (V) and with the same V/Vmax (0.37, i.e. where maximum power is generated) as that of carp.

The importance of V/Vmax is further shown by the comparison of scup swimming at different temperatures. The 1.69-fold higher Vmax at 20°C than at 10°C enables scup to swim with a 1.67-fold faster V at 20°C. Thus, at both 10°C and 20°C, red muscle is used only over the same narrow range of V/Vmax (0.17-0.37), where experiments on isolated muscle suggest that power and efficiency are maximal. Therefore, V/Vmax appears to be an important design constraint that limits the range of velocities over which muscle is used in vivo, both at different temperatures and in fast-and slow-locomoting species.
Patch-Clamp Analysis of the Effects of the Insecticide Deltamethrin on Insect Neurones
Authors: Amar M. , Pichon Y. , Inoue I.
Published: April 2021

The mode of action of the pyrethroid insecticide deltamethrin on inexcitable embryonic cultured cockroach neurones has been investigated using the patchclamp technique. Whole-cell recordings of the current induced by step depolarizations of the cell membrane showed that concentrations of deltamethrin ranging from 10−8 to 5x10−6moll-− induced a small tetrodotoxin (TTX)-sensitive inward current that peaked at around + 10 mV and reversed at around +60 mV. The activation and inactivation kinetics of this current were much slower than those of the axonal sodium current in this same species and were relatively insensitive to membrane potential. Steady-state inactivation was almost absent. Single-channel activity associated with the action of the insecticide was analyzed using the cell-attached configuration. Three distinct patterns of activity were found: (1) discrete single-channel events of relatively short duration, (2) long events of comparatively small amplitude and (3) complex bursts made up of a succession of openings and closings to several levels. These three patterns were analyzed quantitatively using specially designed programs. The first pattern of activity could be seen in most patches. It consisted of short (1-lOms) rectangular events of comparatively small amplitude (1.5pA at rest) and very low open time probability (around 0.001). The current-voltage relationship of these small events was linear over the voltage range studied and the (extrapolated) reversal potential approximated ENa. The second pattern of activity was observed less frequently. The channels could stay open for very long periods (up to several seconds) and occasionally flickered between two or more levels. The third pattern of activity was observed in many patches. During the burst, which could last from a few milliseconds to a few hundred milliseconds, the singlechannel current jumped almost continuously between several levels (up to 7 or 8). The size of the different (single-channel) current levels was the same for the three patterns of activity. Furthermore, these levels corresponded to multiples of the same minimum level (around 1 pA at the resting potential). These results suggest that deltamethrin activates several states of one or several populations of sodium channels.
Physiological Response of the Atlantic Cod (Gadus Morhua) to Hypoxia at Various Environmental Salinities
Authors: Claireaux Guy , Dutil Jean-Denis
Published: April 2021

Atlantic cod (Gadus morhua L.) acclimated to water salinities ranging from 28 ‰ to 7 ‰ were exposed to mild (8.0 kPa) or severe (4.0 kPa) hypoxic conditions for 6h. In each experiment, respiratory, acid–base, ionic, haematological and metabolic disturbances were analyzed. During mild hypoxia, a strong hyperventi-latory response was observed, resulting in a respiratory alkalosis that persisted throughout the 6-h trial. Plasma Cl− and pyruvate levels were the only other variables to display significant changes: they both increased. In more severe hypoxic conditions, although the ventilatory response was the same, a weak metabolic acidosis was superimposed. The haematological response (increased haematocrit and decreased mean cellular haemoglobin content) suggested that catecholamines were released into the blood. Both Na+ and Cl− concentrations increased significantly. Metabolic perturbations occurred: plasma lactate, pyruvate and glucose concentrations increased markedly. Though lactate concen-trations in liver, heart and white muscle increased, the concentrations of pyruvate, glucose and glycogen did not change significantly. Water salinity affected the amplitude of the ionic responses during hypoxia: the amplitude decreased with decreasing salinity. Irrespective of water salinity, 23 of 29 fish survived the severe hypoxic conditions. This relatively good tolerance of low water oxygenation, as compared with other marine bottom-feeders, suggests that this species may face poorly oxygenated waters in the wild. Together with temperature and salinity, water oxygen content may thus be an important variable to take into account in the study of the distribution and migration patterns of Atlantic cod.
Fish Skin: An Effective Barrier to Ice Crystal Propagation
Authors: Valerio Paul F. , Kao Ming H. , Fletcher Garth L.
Published: April 2021

It has been well established that antifreeze peptides are responsible for the ability of many marine teleosts to survive in icy sea water at temperatures below the colligative freezing points of their blood. However, the in vivo site of antifreeze action has yet to be determined. One current hypothesis, the ‘iceexclusion hypothesis’, suggests that antifreeze proteins act within epithelial membranes (skin, gills, gut) and block the entry of external ice crystals. This hypothesis was examined by measuring ice propagation temperatures across isolated skin samples from the winter flounder (Pseudopleuronectes americanus). The results obtained were consistent with the hypothesis, indicating that fish skin is an effective barrier to ice propagation and that the effectiveness of this barrier improves with the addition of antifreeze proteins. The results also demonstrated that the skin ice propagation temperatures were substantially lower than the lethal freezing temperatures of the fish. Therefore, some other epithelial tissue (possible gill) must be less effective than the skin in blocking ice crystal penetration into the fish.>
The Quality of Vision in the Ctenid Spider Cupiennius Salei
Authors: Land M. F. , Barth F. G.
Published: April 2021

Much is known about the mechanosensory behaviour of the spider Cupiennius salei Keyserling, but much less about its visual capabilities. In this study the quality of the optical image, the retinal resolution and the fields of view were assessed for each of the four pairs of eyes. The image is of good quality in all eyes. The principal (antero-median) eyes lack a tapetum and have an inter-receptor angle of 2.9°. The three secondary eyes (antero-lateral, postero-median and posterolateral) all have ‘gridiron’ tapeta with receptors arranged in rows. The angular separations (along rows × between rows) are 3.6° × 9.3°, 0.9° × 2.3° and 1.0° × 3.0°, respectively. Although the disposition of eyes on the head is similar to that of pisaurid spiders, all other features of the eyes, including the sizes and shapes of the fields of view, resemble those of lycosid spiders. The peripheral visual system of Cupiennius can thus, in principle, support a similar range of visual behaviour to that of lycosids, which includes prey capture, predator avoidance and courtship.
Some Properties of the Mammalian Locomotory and Respiratory Systems in Relation to Body Mass
Authors: Young Iain S. , Warren Ruth D. , Altringham John D.
Published: April 2021

Video and ciné films of mammals running at the trot-gallop transition were analysed to measure breathing frequencies. Breathing frequency at the trotgallop transition (fb, in Hz) was shown to decrease with increasing body mass (M, in kg) and was described by the equation fb=5.08M-0 14. The stiffness of the thorax and diaphragm of mice, rats, rabbits and wallabies was calculated and this, together with the mass of the viscera, was used to calculate the natural frequency of the system (nft, in Hz). The relationship between nft and body mass can be described by the equation nft=5.02Mf-0.18. The significance of these results is discussed in relation to models of mechanical linkage between respiratory and locomotory movements.
Pitching Equilibrium, Wing Span and Tail Span in a Gliding Harris’ Hawk, Parabuteo Unicinctus
Authors: Tucker Vance A.
Published: April 2021

The centre of area of the wings of a Harris’ hawk gliding freely in a wind tunnel moved forward 0.09 wing chord lengths when the hawk increased its wing span from 0.68 to 1.07 m. The movement of the centre of area probably produces a positive pitching moment that, if unopposed, would cause the bird’s head to rise. The tail remained folded until wing span reached 87 % of maximum and then began to spread. This behaviour is also typical of gliding birds in nature, which spread their tails when the wings are near maximum span. Tail spreading probably produces a negative pitching moment that compensates for the forward movement of the wings at maximum span. As the tail spread, its centre of area moved backwards. This movement, together with the increase in tail area, can keep the centre of area of the combined wings and tail from moving forward, even at maximum wing span. The tail can generate an estimated 10% of the hawk’s total lift at maximum wing span and 5 % or less at shorter wing spans. I moved the centre of area of the hawk’s wings forward experimentally by clipping 76 mm from primary feathers 6–10 and 38 mm from primary feather 5. The effect of this operation on the hawk’s behaviour indicated that the forward movement of the centre of area of the wings caused a positive pitching moment. The hawk pitched up more in flight. It held its wings at shorter than normal spans, which partially compensated for the effects of clipping by moving the centre of area of the wings backwards. It also spread its tail at shorter than normal spans, which would compensate for an increase in the pitching moment of the wings.
The Effect of Stress and Starvation on Brain Serotonin Utilization in Arctic Charr (Salvelinus Alpinus)
Authors: Winberg Svante , Nilsson Göran E. , Olsén K. Håkan
Published: April 2021

The effects of stress and starvation on brain levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were studied in Arctic charr (Salvelinus alpinus). Three experimental protocols were used to elucidate (1) the effect of stress in fish given food, (2) the effect of starvation, and (3) the effect of stress in fish deprived of food. In the stress experiments, fish were stressed three times a day over a four-week period, and in the starvation experiment the fish were starved for a four-week period. Stressed fish, whether given food or not, showed significantly higher concentrations of 5-HIAA, the main 5-HT metabolite, in both the telencephalon and the brain stem. The 5-HIAA/5-HT ratio (an index of serotonergic activity) was also significantly increased in the brain of stressed fish. In the telencephalon of starved fish, the 5-HT concentration was significantly decreased. However, starvation had no effect on 5-HIAA concentrations or 5-HIAA/5-HT ratios in either the telencephalon or the brain stem. These results suggest that stress increases brain serotonergic activity in Arctic charr, while starvation has no effect on the utilization of this transmitter system. It is suggested that stress could be a mediator of the increased 5-HIAA levels and 5-HIAA/5-HT ratios recently observed in low-ranking Arctic charr in a dominance hierarchy.
Recovery From Acute Haemolymph Acidosis in Unfed Locusts II. Role of Ammonium and Titratable Acid Excretion
Authors: Harrison Jon F. , Phillips John E.
Published: April 2021

In this study we characterized acid, ammonium and total urate excretion in the faecal pellets of unfed locusts (Schistocerca gregaria) and examined the effect of haemolymph acidosis (HCl injections into the haemocoel) on net acid and nitrogen excretion. In unfed, uninjected locusts, the pH of the urinary pellets was less than 5, and ammonium was excreted at three times the rate of total urate. Ammonium was present primarily as a precipitate, indicating that ammonium excretion is compatible with water conservation in this desert locust. Ammonium excretion was increased by HO injections, theoretically accounting for 15 % of the acid equivalents removed from the haemolymph during recovery from acute acid loads. Luminal pH in the hindgut was affected by feeding state but not by haemolymph acidosis. HC1 injections did not affect faecal pellet pH or the excretion rates of bicarbonate, titratable acid, pellet buffer compounds (urate, inorganic phosphate), Na+, K+, Ca2+, Mg2+ or Cl-. In unfed locusts, the low rate of excretion and low pH of faecal pellets may limit the capacity to increase titratable acid excretion after acid-loading.
Brain Neurones Involved in the Control of Walking in the Cricket Gryllus Bimaculatus
Authors: Böhm Hartmut , Schildberger Klaus
Published: April 2021

The responses of single brain neurones to artificial calling song, to moving striped patterns and to air puffs were recorded while tethered crickets were walking on a sphere in such a way that their intended orientation to the stimuli could be measured.

Local and descending brain neurones responsive to only one of the stimuli tested often encoded the directional information contained in the stimulus (e.g. the direction of the sound source or the direction of stripe movement). Brain neurones with little directional sensitivity responded with marked habituation to all stimuli, so that their responses primarily signalled changes in the overall stimulus situation.

The responses of some neurones were stronger during walking than when the cricket was standing still. In the case of one descending neurone, which increased its level of activity shortly before and during the walking phases, the mean spike rate was correlated with the forward velocity. By altering the discharge rate of another descending neurone, it was possible to elicit walking in the manner typical of crickets. Maintenance and control of walking by such ‘command neurones’ is discussed.
Surface Strain on the Equine Hoof Wall in vivo: Implications for the Material Design and Functional Morphology of the Wall
Authors: Thomason J. J. , Biewener A. A. , Bertram J. E. A.
Published: April 2021

Surface strains were recorded from four rosette gauges at different sites on the right forehooves of three ponies running on a treadmill at seven constant speeds and using three gaits. Principal strains determined from the rosette signals indicate that the hoof material is loaded predominantly in compression and that the wall is distorted in a regular, repeatable manner at all speeds and gaits. Peak principal strains reach –5000 μϵ, compared with –2800 μϵ reported for the equine radius under similar locomotory conditions. Orientations of peak compressive strains do not correlate strongly with microstructural axes in the material. Comparison of our in vivo strain records with previous in vitro studies of the material properties of the wall shows that hoof keratin behaves as a multidirectional composite, capable of tolerating its usual operating strains in any direction. This mechanical behaviour also allows the material to withstand many unpredictable loading situations when the hoof contacts irregular substrata. An important property of the hoof wall is its ability to resist or redirect cracks. We found that the anterior aspect of the wall is loaded in biaxial compression, which assists in preventing the formation or propagation of cracks and reduces peak strain magnitudes. The strain patterns correlate well with current models of hoof distortion during weight bearing. In these models, transmission of force between the ground and the skeleton is seen as the primary cause of compression in the material. The third phalanx, which transmits the weight, is effectively suspended from the inner surface of the hoof wall. Spreading of the posterior borders (heels) of the hoof also occurs. The combination of weight-bearing, suspension of the third phalanx and heel spreading is probably responsible for the uncommon loading condition of biaxial compression on the anterior wall.
Adaptation of Feeding Sequences in Aplysia Oculifera to Changes in the Load and Width of Food
Authors: Hurwitz Itay , Susswein Abraham J.
Published: April 2021

In Aplysia oculifera, we examined how feedback from foods of differing physical characteristics produces feeding sequences that are appropriate to the food. Animals were fed strips of food systematically modified by attaching weights to the end of the strip or by changing the width of the strip. Both changes led to an increase in inter-swallow interval and a decrease in the amount of food that entered the mouth per swallow. These data indicate that the oscillator setting swallowing frequency is affected by feedback, but that the amplitude of swallowing movements may not be regulated by feedback. Some swallows led to partial or complete cutting of the food. In some cases, cutting led to loss of contact and release of the food. When cutting releases food, its function is apparently to prevent food that has already been swallowed from being pulled out of the mouth. Cutting food may also serve additional functions.
Fura-2 Measurement of Cytosolic Free Ca2+ Concentration in Corpus Allatum Cells of Larval Manduca Sexta
Authors: Allen C. U. , Herman B. , Granger N. A.
Published: April 2021

Cytosolic free Ca2+ has been implicated in the regulation of the larval corpus allatum (CA) of the tobacco hornworm Manduca sexta since agents presumed to cause changes in intracellular Ca2+ concentrations affect both basal and neuropeptide-modulated synthesis/release of the juvenile hormones. To determine whether differences in cytosolic free [Ca2+] in CA cells were associated with different levels of gland activity, methods were developed for dissociating CA cells with the retention of biosynthetic activity and for uptake by the dissociated cells of the fluorescent Ca2+ indicator Fura-2. Digitized fluorescence microscopy of the Fura-2-loaded cells enabled measurement of intracellular Ca2+ levels in individual cells. Intracellular free Ca2+ levels were measured in CA cells from selected days during the fifth larval stadium and were found to be highest when the CA were biosynthetically active. Treatment of CA cells from day 6 with the Ca2+ ionophore ionomycin elevated the intracellular Ca2+ level, corroborating the involvement of elevated intracellular [Ca2+] in ionophore effects on juvenile hormone (JH) and JH acid synthesis. The results of the study are considered in relation to our knowledge of the role of Ca2+ in the function of endocrine gland cells.
Direct Measurement of Swimming Speeds and Depth of Blue Marlin
Authors: Block Barbara A. , Booth David , Carey Francis G.
Published: April 2021

Acoustic telemetry was used to monitor the swimming speed, depth and water temperature of three blue marlin (60 kg, 70 kg, 125 kg) and 165 h of continuous swimming speed data containing both sustained and burst swimming events were collected. Measurements of swimming speed show that, while blue marlin are capable of high speeds, they spend most of their time swimming slowly. The fastest sustained swimming speeds (80–120 cm s−1) occurred during a 4–6h recovery period immediately after tagging when marlin consistently swim at depths greater than 50 m. Short bursts of speeds up to 225 cm s−1 were usually associated with changes in depth. Slower swimming (15–25 cms−1) occurred when fish were within 10 m of the surface. These velocities are similar to direct measurements of swimming speeds of free-swimming sharks, seals and sea lions, indicating that many large aquatic vertebrates swim slowly to minimize energetic costs of transport.
Calcium Transport By Isolated Skin Of Rainbow Trout
Authors: Marshall William S. , Bryson Sharon E. , Wood Chris M.
Published: April 2021

The skin overlying the cleithrum bone of freshwater-acclimated rainbow trout contains numerous mitochondria-rich (MR) cells, as detected by DASPEI fluorescence. This tissue was mounted in vitro in an Ussing-style chamber with fresh water on the mucosal surface and saline supplemented with bovine serum albumin on the serosal surface. The preparation developed a high transepithelial resistance and a small transepithelial potential (Vt), positive on the serosal side. Radioisotopic flux measurements indicated that the preparation actively transported Ca2+ from the mucosal to the serosal surface, as assessed by the Ussing flux ratio criterion. Ca2+ transport was positively correlated with MR cell density. Cortisol pretreatment in vivo reduced MR cell density and increased Vt but did not significantly alter Ca2+ fluxes. Ca2+ transport was unaffected by adrenergic agonists (10−5moll−1 adrenaline, clonidine, isoprenaline) or cyclic AMP stimulants (10−3molll dibutyryl cyclic adenosine monophosphate, db-cAMP, plus 10−4moll−1 isobutylmethylxanthine, IBMX) applied to the serosal surface. The Ca2+ ionophore ionomycin (1×10−6–3.2× 10−6moll−1 on the mucosal surface) increased both unidirectional Ca2+ fluxes and caused Ca2+ to accumulate within the epithelium. Lanthanum (10−4 mol I−1) did not inhibit unidirectional Ca2+ fluxes, but apparently displaced Ca2+ from binding sites on the mucosal surface. Unlike Ca2+, movements of Na+ and Cl− across the epithelium were passive, as assessed by the flux ratio criterion, and neither adrenaline nor db-cAMP plus IBMX had any effect on Na+ or Cl− fluxes or electrical properties. These results indicate that ion transport across the skin mediated by MR cells (‘chloride cells’) contributes to Ca2+ but not to NaCl balance in freshwater trout.
Transbranchial Ammonia Gradients and Acid-Base Responses to High External Ammonia Concentration in Rainbow Trout (Oncorhynchus Mykiss) Acclimated to Different Salinities
Authors: Wilson R. W. , Taylor E. W.
Published: April 2021

Transbranchial ammonia gradients and blood acid-base status have been examined in rainbow trout acclimated to fresh water (FW), 33% sea water (33 %SW) and sea water (SW) and exposed to 1.0 mmol I−1 total ammonia (TAmm) at pH7.9 for 24 h. At all three salinities trout maintained large negative (inwardly directed) NH3 and NH4+ gradients throughout the exposure, presumably by active excretion of NH4+ to counteract the passive inward diffusion of ammonia. Analysis of blood non-respiratory acid-base status revealed an acid load in FW trout and a base load in SW trout following 24 h of exposure. This indicates that active NH4+/H+ exchange predominates in FW whereas NH4+/Na+ is the principal exchange utilised in SW under these experimental conditions.

The plasma TAmm load incurred during ammonia exposure increased with salinity. Compared to FW trout, plasma TAmm values were 34 and 73 % higher in the 33 %SW and SW trout, respectively, after 24 h. This cannot be explained by differences in the prevailing transbranchial gradient because ambient was substantially lower at the higher salinities (due to higher pK’ and solubility values). We interpret the difference between FW and SW trout as an increased permeability to NH4+ in fish acclimated to the higher-salinity environments. Transbranchial diffusion of NH4+ is, therefore, probably more important as a route for ammonia excretion in SW than in FW trout, especially considering the favourable transepithelial potentials normally found in SW teleosts. In addition, increased NH4+ permeability implies that the toxicity of ammonia will be greater in seawater than in freshwater teleosts and should not simply be measured as a function of the unionised ammonia concentration when considering seawater-adapted species.
A Nerve-Muscle Preparation From the Snail
Authors: Ramsay J. A.
Published: April 2021

A nerve-muscle preparation from the snail and its method of removal from the animal are described. Further description is given of the apparatus used for obtaining records of its activity. The nerve appears to contain fibres which fall into two groups according to their diameters. It is suggested that the thin fibres are derived from the thick ones. No physiological evidence of double innervation has been found. There is clear evidence of neuro-muscular facilitation. The muscle contracts in response to low concentrations of acetylcholine.
Ambulatory Reflexes in Spinal Amphibians
Authors: Gray J. , Lissmann H. W.
Published: April 2021

The profound effect of spinal deafferentation upon the locomotory activity of amphibians (Gray & Lissmann, 1940) suggests that peripheral sense organs play an essential role in the maintenance of normal ambulatory activity. In order to test this conclusion, a preliminary study has been made of those reflex responses which can be elicited from the limbs of spinal newts, frogs and toads, by the application of peripheral stimuli similar in kind and intensity to those which arise automatically during normal progression. Unless otherwise stated, all observations were made on preparations in which the nerve cord had been severed at or about the level of the first vertebra. All operations were performed under ether, and the preparations were allowed to recover from shock. The animals employed were Triton cristatus, Rana temporaria and Bufo bufo.
Catecholamine-Activated Sodium/Proton Exchange in the Red Blood Cells of the Marine Teleost Gadus Morhua
Authors: Berenbrink M. , Bridges C. R.
Published: April 2021

The effects of catecholamines on the pH and the cellular ion and water content were investigated in red blood cells from the Atlantic cod (Gadus morhua). Noradrenaline induced a rapid decrease in the extracellular pH (pHe) of red blood cells suspended in a CO2/bicarbonate or in a CO2/bicarbonate-free buffer system. The noradrenaline-induced changes in pHe were a saturable function of the external sodium ion concentration and were inhibited by amiloride but not by DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid, final concentration of both 10×4 mol l−1). The catecholamine-induced extracellular acidification was accompanied by an intracellular alkalization and protons were moved from their electrochemical equilibrium. Proton extrusion was associated with an increase in the red blood cell sodium and chloride concentrations. In the presence of DIDS, the chloride movements were blocked and the net proton efflux under these conditions matched the net sodium influx. The results strongly suggested the activation of a sodium/proton exchanger by catecholamines in the red blood cells of the Atlantic cod. The red blood cell receptor affinity for adrenaline was three times higher than that for noradrenaline. Comparison with data in the literature for in vivo catecholamine concentrations indicated that adrenaline was more effective than noradrenaline in activating the red blood cell sodium/proton exchanger in the Atlantic cod in vivo.
Reconstitution of Metachronal Waves in Ciliated Cortical Sheets of Paramecium: II. Asymmetry of the Ciliary Movements
Authors: Okamoto Ken-Ichi , Nakaoka Yasuo
Published: April 2021

In conditions in which ciliated cortical sheets prepared from detergent-extracted Paramecium multimicronucleatum cells adhered to glass coverslips on a microscope stage, perfusion of a reactivation medium containing ATP plus cyclic AMP or cyclic GMP generated metachronal waves. An analysis of the ciliary movements that generate these metachronal waves yielded the following results. During the generation of metachronal waves, there were phase differences in the ciliary orientation of adjacent cilia in the direction of wave propagation. Addition of cyclic AMP or cyclic GMP increased the rotational angular velocities during the effective stroke of ciliary beating, but did not increase the rotational angular velocity of the recovery stroke. When the ATP concentration in the cyclic GMP reactivation medium was increased, the rotational angular velocity during the effective stroke rose steeply and saturated at 0.8 mmol l-1 ATP, whereas that during the recovery stroke rose gradually. Addition of cyclic nucleotides caused a single cilium isolated from neighbouring cilia on the cortical sheet to incline almost parallel to the cortical surface during the recovery stroke. Addition of cyclic GMP increased the amplitude of bending of cilia detached from the cortical sheet. From these results, it was concluded that increases in the asymmetrical movement of individual cilia, caused by the addition of cyclic nucleotides, create the ciliary interaction that generates the metachronal waves.
Transduction Diversity in Olfaction
Authors: Dionne Vincent E. , Dubin Adrienne E.
Published: April 2021

Odors are powerful stimuli that can focus the attention, elicit behaviors (or misbehaviors) and even resurrect forgotten memories. These actions are directed by the central nervous system, but they depend upon the initial transduction of chemical signals by olfactory receptor neurons. Electrophysiological recordings suggest that the responses of olfactory receptor neurons to odors are more diverse than was initially believed, being mediated by effects on several different conductances. Both excitatory and inhibitory responses are produced by these effects and some, if not all, odors can affect more than one component of the membrane conductance. The extent of this diversity is reviewed here, and its impact on our understanding of odor discrimination is discussed.
Intracellular ion Concentrations in Branchial Epithelial Cells of Brown Trout (Salmo Trutta L.) Determined by X-Ray Microanalysis
Authors: Morgan I. J. , Potts W. T. W. , Oates K.
Published: April 2021

The intracellular concentrations of sodium, chloride, phosphorus and potassium under normal conditions in pavement epithelial (PE) cells of brown trout (Salmo trutta) gill were 66, 51, 87 and 88 mmol l−1 respectively. The concentrations of these elements under identical conditions in mitochondria-rich (MR) cells were not significantly different, except for that of chlorine, which was lower in MR cells (40 mmol l−1). The concentration of sodium in the PE cells decreased slightly after exposure of the fish to low external [Na+] (25 μmol l−1) for 7 days but increased greatly within 5 min of subsequent exposure to 1 mmol l−1 external Na+. These changes in external [Na+] had no significant effect on MR cells. Exposure of fish to low [Cl−] (25 μmol l−1) had no effect on PE or MR cells, but on exposure to 1 mmol l−1 Cl− the concentrations of chlorine, phosphorus and potassium in both types of cells increased, whilst the intracellular sodium concentration decreased only in MR cells. The PE cells were little affected by exposure of the fish to the carbonic anhydrase inhibitor acetazolamide. In contrast, 0.5 mmol l−1 external acetazolamide caused a significant decrease in intracellular phosphorus, chlorine and potassium concentrations in MR cells. This suggests that the PE cells are the sites of sodium uptake in the gills of the brown trout and that chloride uptake occurs via the MR cells. These results are discussed with respect to the sites and possible mechanisms of ionic exchange in freshwater vertebrates.
Allatostatin Peptides in the Crab Stomatogastric Nervous System: Inhibition of the Pyloric Motor Pattern and Distribution of Allatostatin-Like Immunoreactivity
Authors: Skiebe Petra , Schneider Henning
Published: April 2021

The effects of four Diploptera punctata allatostatin peptides on the stomatogastric nervous system of the crab Cancer borealis were studied. All of the peptides had similar actions on the activity of neurons involved in rhythmic movements of the pyloric region of the stomach, decreasing the frequency of the pyloric rhythm in a dose-dependent manner. Diploptera allatostatin 3 (D-AST-3) was slightly more effective than the others. The absolute change in the frequency of the pyloric rhythm depended on the starting frequency, demonstrating that the effect of D-AST-3 depends on the preceding physiological state of the preparation. The largest decreases were observed when the starting frequency was slower than 0.8 Hz.

Whole-mount immunocytochemistry with anti-Diploptera allatostatin 1 antibodies demonstrated the presence of allatostatin-like peptides in the paired commissural ganglia, the unpaired oesophageal ganglion and the stomatogastric ganglion, and in their connecting and motor nerves. Dense processes were labeled in the stomatogastric ganglion, 12–19 cell bodies and neuropil staining were found in each commissural ganglion, two cell bodies were stained in the oesophageal ganglion and two pairs of cell bodies, the gastropyloric receptor neurons, were stained in peripheral nerves.
Jamming Bat Echolocation: the Dogbane Tiger Moth Cycnia Tenera Times Its Clicks to the Terminal Attack Calls of the Big Brown Bat Eptesicus Fuscus
Authors: Fullard James H. , Simmons James A. , Saillant Prestor A.
Published: April 2021

Certain tiger moths emit high-frequency clicks to an attacking bat, causing it to break off its pursuit. The sounds may either orient the bat by providing it with information that it uses to make an attack decision (aposematism) or they may disorient the bat by interrupting the normal flow of echo information required to complete a successful capture (startle, jamming). At what point during a bat’s attack does an arctiid emit its clicks? If the sounds are aposematic, the moth should emit them early in the attack echolocation sequence in order to allow the bat time to understand their meaning. If, however, the sounds disrupt the bat’s echo-processing behaviour, one would expect them to be emitted later in the attack to maximize their confusion effects. To test this, we exposed dogbane tiger moths (Cycnia tenera) to a recording of the echolocation sequence emitted by a big brown bat (Eptesicus fuscus) as it attacked a stationary target. Our results demonstrate that, at normal echolocation intensities, C. tenera does not respond to approach calls but waits until the terminal phase of the attack before emitting its clicks. This timing is evident whether the moth is stationary or flying and is largely independent of the intensity of the echolocation calls. These results support the hypothesis of a jamming effect (e.g. ‘phantom echoes’) and suggest that, to determine experimentally the effects of arctiid clicks on bats, it is important that the bats be tested under conditions that simulate the natural context in which this defence operates.
The Metabolic Characteristics of the Locomotory Muscles of Grey Seals (Halichoerus Grypus), Harbour Seals (Phoca Vitulina) and Antarctic Fur Seals (Arctocephalus Gazella)
Authors: Reed J. Z. , Butler P. J. , Fedak M. A.
Published: April 2021

It is not known precisely how marine mammals are able to maintain muscle function during active swimming in breath-hold dives, when ventilation stops and heart rate falls. Examination of muscle biochemistry and histochemistry can provide information on the relative importance of different metabolic pathways, the contractile potential of the muscle fibres, the oxygen storage capacity of the muscle and the capillary distribution in these animals. In this study, samples of locomotory muscle were taken from wild grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella); Wistar rat muscle was analysed for comparative purposes.

Activities of citrate synthase and β-hydroxyacyl CoA dehydrogenase were higher in the harbour seal muscle than in the grey seal muscle, suggesting that harbour seals have a greater aerobic capacity. Both phocid muscles had a greater reliance on fatty acid oxidation than the fur seal or rat muscles. The myoglobin data demonstrate that the grey seals have the highest oxygen storage capacity of the three pinniped species, which correlates with their greater diving ability. Myoglobin levels were higher in all three pinniped species than in the Wistar rat. The fibre type compositions suggest that the muscles from the fur seals have higher glycolytic capacities than those of the phocid seals [fur seal pectoralis, 7% slow-twitch oxidative fibres (SO), 25% fast-twitch oxidative glycolytic fibres (FOG), 68% fast-twitch glycolytic fibres (FG); grey seal 57% SO, 5% FOG, 38% FG; area per cents]. However, the pectoralis muscle of the fur seal, although the most glycolytic of the pinniped muscles studied, has the highest capillary density, which indicates a high capacity for fuel distribution.

These results show that, while pinniped muscle has an increased oxygen storage potential compared with the muscle of a typical terrestrial mammal, there are no distinct adaptations for diving in the enzyme pathways or fibre type distributions of the pinniped muscle. However, the muscle characteristics of each species can be related to its diving behaviour and foraging strategy.
Stimulus–Secretion Coupling in the Neurohypophysis of the Jerboa Jaculus Orientalis
Authors: Raji Aicha , Nordmann Jean J.
Published: April 2021

In many mammals, severe dehydration is known to cause exhaustion of the vasopressin content of the neural lobe. Here, we have examined the physiological state of the neurohypophysis of the jerboa Jaculus orientalis, a rodent inhabitant of a semi-desert climate. Isolated neurohypophyses and neurosecretory nerve endings were perfused in vitro and vasopressin and oxytocin release were determined by radioimmunoassay. Electrical stimulation of the neurohypophysis with bursts of pulses mimicking the activity of hypersecreting neuroendocrine neurones induced similar increases of secretion in both control animals and animals dehydrated for up to 2 months. Neurohormone release was greatly potentiated when the bursts of pulses were separated by silent intervals. Prolonged stimulation of neurohypophyses from both control and dehydrated animals induced a sustained increase of vasopressin release; in contrast, oxytocin release under similar conditions showed a biphasic secretory pattern consisting of a transient increase that subsequently decreased to a steady level whose amplitude was similar to that for vasopressin. K+-induced secretion was largely inhibited by the Ca2+ channel blockers nicardipine and ω -conotoxin, suggesting that in this neurosecretory system both L-and N-type calcium channels play a major role in stimulus–secretion coupling. Depolarization of isolated nerve endings using a fast-flow perifusion system showed that there was no difference in the amplitude and the time course of the secretory response in dehydrated and hydrated animals. The results demonstrate that, despite the climatic conditions in which the jerboas live, their neural lobes retain the capacity to release, upon depolarization of the plasma membrane of the nerve endings, large amounts of neurohormone. It is concluded that the neurohypophyseal peptidergic release system in the dehydrated jerboa functions adequately even under extreme environmental stress.
Emperor Penguin Oxygen Consumption, Heart Rate and Plasma Lactate Levels During Graded Swimming Exercise
Authors: Kooyman G. L. , Ponganis P. J.
Published: April 2021

Oxygen consumption , heart rate and blood chemistry were measured in four emperor penguins, Aptenodytes forsteri (Gray), during graded swimming exercise. The maximum obtained, 52 ml O2 kg−1 min−1, was 7.8 times the measured resting of 6.7 ml O2 kg−1 min−1 and 9.1 times the predicted resting . As the swimming effort rose, a linear increase in surface and submerged heart rates (fH) occurred. The highest average maximum surface and submersion heart rates of any bird were 213 and 210 beats min−1, respectively. No increase in plasma lactate concentrations occurred until was greater than 25 ml O2 kg−1 min−1. At the highest values measured, plasma lactate concentration reached 9.4 mmol l−1. In comparison with other animals of approximately the same mass, the aerobic capacity of the emperor penguin is less than those of the emu and dog but about the same as those of the seal, sea lion and domestic goat. For aquatic animals, a low aerobic capacity seems to be consistent with the needs of parsimonious oxygen utilization while breath-holding.