bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematics of Labriform and Subcarangiform Swimming in the Antarctic Fish Notothenia Neglecta
Authors: Archer Stephen D. , Johnston Ian A. 
Published: April 2021

ABSTRACT
The kinematics of labriform and subcarangiform swimming have been investigated for juvenile (7–8 cm) and adult (27–30 cm) stages of the antarctic teleost Notothenia neglecta Nybelin at 1–2 °C. Upper threshold speeds using the pectoral fins alone (labriform swimming) were 0·8Ls−1 in adult fish and l·4Ls−1 in juveniles, where L is body length. In adult fish, steady subcarangiform swimming is only used at speeds of 3·6–5·4Ls−1 (tail-beat frequencies of 5·0–8·3Hz). Intermediate speeds involve unsteady swimming. In contrast, juvenile fish employ subcarangiform swimming at a range of intermediate velocities between the maximum labriform and burst speeds (2·3–8·4Ls−1 at tail-beat frequencies of 4·0–12·5 Hz). These differences in swimming behaviour are discussed in relation to changes in life-style and muscle fibre type composition between juvenile and adult fish. Burst swimming speeds in N. neglecta have been compared with equivalent data from temperate species. It seems likely that low temperature limits swimming performance in antarctic fish. This is more noticeable in juvenile stages, which normally have much higher tail-beat frequencies than adult fish.
Adaptations to A Terrestrial Existence by the Robber Crab, Birgus Latro L. III. Nitrogenous Excretion
Authors: Greenaway P. , Morris S. 
Published: April 2021

ABSTRACT
Nitrogenous excretion by the terrestrial anomuran crab Birgus latro L. was examined. The main excretory product was uric acid, representing 79·5 % of total excretory nitrogen. It was eliminated as white faeces separate from undigested food material and made up 82·6% of excretory faecal nitrogen. The faeces were the principal route of nitrogenous excretion, accounting for 96·2 % of total excretion. Loss of nitrogen in the urine and as gaseous ammonia was negligible. The midgut gland had substantial activity of xanthine oxidase and was considered to be the site of production of uric acid and its point of entry into the gut.
Metabolic Control of Luminescence in the Luminous Organs of the Teleost Porichthys: Effects of the Metabolic Inhibitors Iodoacetic Acid and Potassium Cyanide
Authors: Rees J. F. , Baguet F. 
Published: April 2021

ABSTRACT
The treatment of isolated photophores of the epipelagic luminescent fish Porichthys notatus Girard with the glycolytic inhibitor iodoacetic acid (IAA) induces light production. This luminescence is not significantly affected by the adrenergic antagonists phentolamine and propranolol. The addition of pyruvate, phosphoenolpyruvate or glyceraldehyde 3-phos-phate in saline suppresses the light response to IAA. D-Glucose, D-glyceraldehyde, and 2-and 3-phosphoglycerate have no inhibitory effects. The luminescence of the photophores induced by KCN is inhibited by D-glucose, D-glyceraldehyde 3-phosphate and 3-phosphoglycerate. In contrast, 2-deoxy-D-glucose, pyruvate, phosphoenolpyruvate, D-glyceraldehyde and 2-phosphoglycerate do not affect this light production. These results confirm the view that glycolysis and oxidative phosphorylation are essential metabolic pathways in the photogenic cells. They further indicate that common products of these tightly associated metabolic pathways may regulate the activity of the luminous system in these cells.
Extraglandular Innervation of the Salivary Cells of the Leech Haementeria Ghilianii: Neuronal Stimulation Elicits Gland-Cell Action Potentials and Secretion
Authors: Wuttke Werner A. , Sawyer Roy T. , Berry Michael S. 
Published: April 2021

ABSTRACT
Each salivary gland cell of Haementeria extends a single process, or ductule, anteriorly into the proboscis; secretory products are released at the ductule ending. Some ductules secrete into the lumen of the proboscis and others at the outer surface of its tip, more than 5 cm from the gland in large leeches. Depolarization of a gland-cell body elicits action potentials which appear to be conducted along the ductule to its ending. Electrical stimulation of the proboscis tip elicits action potentials in those ductules which end there, and the impulses are propagated to the cell body (approx. 5cms−1). Bathing the salivary glands in calcium-free saline causes spontaneous repetitive firing in the cell bodies and also elicits secretion at the proboscis tip (bathed in normal saline); the action potential thus appears to be a stimulus for secretion. A paired stomatogastric nerve, from the brain, enters the proboscis near its base. Cobalt-filling of the nerve shows numerous cell bodies in the brain and first body ganglion, and an intricate network of fibres and a cluster of stained cell bodies near its entry point in the proboscis. Repetitive stimulation of the stomatogastric nerve produces action potentials in certain gland cells, after a delay of at least 15 s, and also elicits secretion. The action potentials are initiated near the ductule tip, and are conducted to the cell body. The salivary glands themselves do not appear to be innervated. Application of acetylcholine (ACh), dopamine or octopamine (10−4mol 1−1) does not initiate secretion. Neither dopamine nor octopamine excites the gland cells but ACh produces a transient suprathreshold depolarization of the cell body and occasionally elicits 1–3 ductule spikes when applied to the proboscis tip. 5-Hydroxytryptamine (5-HT) produces secretion when applied to the proboscis but not when applied to the glands alone; it does not excite the cells, indicating that the action potential is not the only stimulus for secretion. 5-HT produces a depolarization, and increase in membrane resistance, in the cell body, and prevents the rapid adaptation of action potentials which occurs during maintained depolarization.
7.Electrophoretic analysis shows that the protein compositions of secretions at the proboscis tip and in the lumen are completely different, with the tip apparently secreting only two major proteins. These same two protein bands occur in the cytoplasm of certain gland-cell bodies which can be distinguished in living glands on the basis of size and degree of staining with Methylene Blue.
8.Following stimulation of the stomatogastric nerve, secretory products at the proboscis tip can be seen to emerge from discrete points which appear to be single ductule endings. This presents the possibility of studying excitation-secretion coupling in single cells.
Pressure Adaptation of Na+/K+-ATPase in Gills of Marine Teleosts
Authors: Gibbs Allen , Somero George N. 
Published: April 2021

ABSTRACT
The effects of pressure and temperature on an integral membrane protein, Na+/K+-adenosine triphosphatase (Na+/K+-ATPase), were studied in fish gill membrane preparations from shallow- and deep-living marine teleosts. The inhibition by pressure of maximal velocity of the enzyme is nonlinear, increasing at higher pressures. Na+/K+-ATPases from deep-sea fish were less inhibited by pressure than those of shallow-living species. Habitat temperature also affected the pressure response of the enzyme. As a function of physiological pressure and temperature, the order of increasing pressure-sensitivity was cold, deep-sea &lt; warm, deep-sea (hydrothermal vents) &lt; polar = shallow and mid-depth, cold&lt; shallow, warm. Activation volumes in all species were conserved at 30–60ml mol−1 at physiological pressures, which may reflect a similar membrane physical state at the actual pressure the animal experiences. Arrhenius plots [in(Na+/K+-ATPase activity) vs 1/T] were steeper for warm-water and shallow living species than for deep-sea species. The depth at which adaptation was first observed was about 2000m (≈200atm; 1 atm = 101·3kPa). The data are consistent with a model of increased membrane fluidity resulting in reduced pressure sensitivity of Na+/K+-ATPase from deep-sea species.
Physiological Responses of the Crayfish Pacifastacus Leniusculus to Environmental Hyperoxia : II. Role of the Antennal Gland in Acid–Base and Ion Regulation
Authors: Wheatly Michèle G. , Toop Tes 
Published: April 2021

ABSTRACT
Handling of electrolytes and acidic equivalents by the antennal gland was monitored in freshwater crayfish (Pacifastacus leniusculus) during control normoxia (; 1 mmHg = 133·3 Pa), 72h of hyperoxia () and 24 h of recovery. A preparation was developed for direct collection of urinary flow (UFR) which was confirmed using inulin clearance (ĊIN)-Renal effluxes of Na+, Cl−, Mg2+, K+, Ca2+, sulphate, phosphate, titratable and nontitratable acidity and CO2 were monitored. These were used in conjunction with filtration rates to calculate net rates of reabsorption.
UFR was elevated by around 50 % during hyperoxia. Contributing to this were an increase in ĊIN and a reduction in [IN]u: [IN]e. Excretion of Na+ (ĖNa) tended to increase initially whereas ĖCl tended to decrease after 36h. ĖK and ĖMg showed a similar profile to that of ĖNa with increases averaging 60 %. The increases in excretion of Ca2+, phosphate and sulphate were more pronounced (threefold). In control crayfish, 65–95 % of filtered electrolytes were reabsorbed at the antennal gland except for ammonia which was secreted. Electrolyte reabsorption increased during hyperoxia; percentage increases varied from 70% (Na+, Cl−) to 150% (sulphate, phosphate) with HCO3− showing a fourfold increase above control values. Ammonia secretion correspondingly increased. Control urine was acid with respect to the haemolymph and became increasingly acidified during initial hyperoxic exposure. Net renal proton excretion largely reflected (90%) ammonia excretion; both were approximately doubled during hyperoxia. Unlike the situation in mammals, ammonia appears to be more important than phosphate in buffering urine pH. Urinary parameters generally required 24 h for complete recovery when normoxia was reinstated.
Renal net efflux and reabsorption rates were compared with branchial net and unidirectional influx rates from an earlier part of this study. Branchial and renal net effluxes of Na+ and Cl− had similar vectors and magnitudes during the control period but tended to counter each other during hyperoxia. Renal reabsorption rates of these ions were threefold greater than branchial influx rates, confirming increased transporting capability. Both epithelia exhibited a net H+ efflux during hyperoxia; the kidney contributed only 10% of the whole-animal response. Possible mechanisms of renal postfiltrational electrolyte and acidic equivalent processing are discussed.
Kinematic Analysis of Symmetrical Flight Manoeuvres of Odonata
Authors: Rüppell G. 
Published: April 2021

ABSTRACT
By analysis of slow-motion films of dragonflies and damselflies in free flight, released in front of a backdrop or startled during flight, the following flight parameters have been quantified for symmetrical manoeuvres: wingbeat frequency, relative durations of up-and downstroke, phase relationships of the beats of fore-and hindwings, stroke amplitude, mean stroke velocity, flight velocity, nondimensional flight velocity, advance ratio, acceleration, angle of attack and stroke plane.
The wingbeat frequencies are higher in the smaller species and in those with relatively large wing loading. As a rule, Zygoptera have a wingbeat frequency only half that of Anisoptera. The stroke amplitude is almost always much larger in Zygoptera than in Anisoptera, which have a greater range of variation in this respect. Stroke velocity is higher in Anisoptera than in Zygoptera; it is also higher in the more elaborate flight manoeuvres than in others. The calculated stroke velocities resemble those actually measured.
Anisoptera fly more rapidly than Zygoptera. With respect to the nondimensional flight velocities, it is notable that although the values for Anisoptera are higher than those for Zygoptera, they are exceeded by the Calopterygidae; the latter can fold their wings back during rapid forward flight and shoot away, as in the ‘ballistic’ flight of small songbirds. However, the advance ratio is higher in Anisoptera than in Calopterygidae.
Anisoptera also perform better than Zygoptera with respect to acceleration. Three categories of phase relationships between the beats of the fore-and hindwings are established: counterstroking, phase-shifted stroking and parallel stroking. Counterstroking produces uniform flight, whereas the flight produced by phase-shifted and, in particular, parallel stroking is irregular. The angles of attack of the wings are shown to be associated with particular flight manoeuvres, as are the stroke planes. Flight manoeuvres are discussed without drawing detailed aerodynamic conclusions. The flight of Anisoptera is compared with that of Zygoptera.
More Than One Type of Conductance is Activated During Responses of Blowfly Monopolar Neurones
Authors: Weckström M. , Kouvalainen E. , Djupsund K. , Järvilehto M. 
Published: April 2021

ABSTRACT
The principal second-order neurones in the blowfly compound eye, the large monopolar neurones (LMCs), were studied using intracellular recording and discontinuous current-clamp techniques, in combination with measurement of dynamic input resistance. The LMCs had resting potentials of –35 to –45 mV and showed a linear current-voltage relationship in the lamina in the physiological voltage range. The hyperpolarizing light-on transient was associated with a drop in input resistance from 17 ± 5 to 3 ± 1MΩ, and had a reversal potential between –60 and –90 mV. The dynamic input resistance of saturated responses and the properties of reversed responses suggested that more than one conductance was activated during the response of the LMCs. In lamina recordings, the input resistance increased beyond the resting level during repolarization, which can be interpreted in terms of a continuous release of transmitter by the photoreceptor terminals, even in darkness. The input resistance of LMCs in axon recordings in darkness and during the light-on response was generally higher than in the lamina recordings. The responses to light in axons also differed from those recorded in lamina by showing regenerative properties.
Salt Gland Function in the Green Sea Turtle Chelonia Mydas
Authors: Nicolson Sarah W. , Lutz Peter L. 
Published: April 2021

ABSTRACT
When salt-gland-cannulated green sea turtles were stimulated by the intravenous injection of various salt loads the secretion osmolality rose quickly from a basal value of 300–400 mosmol kg-1 to a plateau of 1680–2000. The height of the plateau and the duration of the response were dependent on the amount of salt given. An increase in flow rate accompanied the initial rise in concentration, but the flow rate thereafter declined while the plateau concentration was held. The fluid was protein-free, and was mainly composed of Na+ and Cl-, in similar relative concentrations to those in sea water, but had substantial amounts of K+, Mg2+ and HCO3- and negligible amounts of glucose. Urea concentrations did not change with osmolarity, and were similar to that of plasma, suggesting that the walls of the salt gland ducts are permeable to urea. The composition of the tears was uninfluenced by the concentration of the injected solutions, and its ionic content did not directly depend upon the identity of the added salts. The two eyes of individual turtles frequently did not function in synchrony. The average amount of the salt load remaining in a turtle at the end of salt gland activity, 4·5 mmol ion kg body mass-1, was very similar to the median load required to stimulate the salt gland (4·0mmolion kg body mass-1). This suggests that there is a threshold salt load level of around 4·5 mmol ion kg body mass-1 that determines salt gland on/off activity.
The flow/concentration relationships of the salt gland fluid are consistent with water reabsorption from a primary isosmotic secretion being the major mechanism for concentrating the tears. A high maximal secretory rate is indicated for the primary fluid, 0·32 ml g salt gland-1 min-1, equivalent to that of the mammalian kidney. Calculations suggest that 83% of the initial fluid is recovered, Na+ is passively concentrated, Cl- and Mg2+ concentrations are enhanced, and that the duct walls are either impermeable to glucose or that glucose is actively taken up.
Are the Hindwing Chordotonal Organs Elements of the Locust Flight Pattern Generator?
Authors: Pearson K. G. , Hedwig B. , Wolf H. 
Published: April 2021

ABSTRACT
Anatomical and electrophysiological techniques were used to examine the structure, central nervous connections and discharge patterns of afferents arising from the hindwing chordotonal organs in the locust, Locusta migratoria. The hindwing chordotonal organ afferents were found to be sensitive to low-frequency sounds (approx. 3 kHz) and to vibrations of the supporting surface. During flight in tethered animals these afferents were strongly activated. This flight-related activity was weakly modulated and the maximum occurred between depressor bursts. Low-frequency sound pulses were used to activate selectively the hindwing chordotonal organ afferents during rhythmic flight activity in deefferented preparations (all motor nerves cut). Phasic stimulation of the chordotonal organs, time-locked to every cycle, had no effect on the frequency of the centrally generated rhythm as recorded from proximal nerve stumps. Staining of single afferents from the hindwing chordotonal organ showed that they bifurcate in the metathoracic ganglion, with one branch terminating in the ring tract and the other branch projecting to the mesothoracic ganglion via the ipsilateral connective. None of the terminal processes of chordotonal afferents was observed to be located in dorsal neuropile regions containing the processes of flight neurones. Consistent with this finding, the chordotonal afferents were not observed to make synaptic connections to flight interneurones or motoneurones. The main conclusion of this investigation is that the hindwing chordotonal organs do not contribute to the patterning of motor activity for flight. The hindwing chordotonal organs probably function as detectors of vibration and perhaps low-frequency sound.
Sensory Systems in the Swimmerets of the Crayfish Cherax Destructor and their Effectiveness in Entraining the Swimmeret Rhythm
Authors: Macmillan David L. , Deller Simon R. T. 
Published: April 2021

ABSTRACT
The branching patterns and profiles of the main sensory nerves of the swimmerets of Cher ax destructor are described. The innervation is generally similar to that in Pacifastacus but there are important differences that may be due to species variation or that may explain apparent differences in the physiology of the two species. The two large axons from the long strand of the stretch-receptor complex in Cherax give rise to non-spiking signals whereas those from the short strand are not active during passive protraction and retraction of the swimmeret.
The rhythmic movements of one swimmeret are sufficient to entrain the fictive swimmeret rhythm of an otherwise deafferented ventral nerve cord. The parameters of this entrainment match those of the known reflexes associated with swimmeret movement. Ablation experiments show that the stretch-receptor complex is necessary and sufficient for this entrainment and that input from the pleural plate hairs and swimmeret hairs is not required. Sinusoidal current injection into the non-spiking stretch receptors can also entrain the fictive rhythm of the deafferented cord.
From these results it is argued that the non-spiking stretch receptors play an important part in stabilizing and adjusting the frequency of the swimmeret rhythm. The swimmeret system is therefore another example of patterned motor output generated by a distributed, multicomponent network and this may be a general feature of cyclically rhythmic systems.
Response Features of Visual Units in the Lower Midbrain of the Rainbow Trout
Authors: Schellart Nico A. M. , Rikkert Walther E. I. 
Published: April 2021

ABSTRACT
In the mesencephalic torus semicircularis of fish, visual processing is carried out in addition to acousticolateral processing, and takes place in unimodal and bimodal units. To study the encoding of visual stimuli in the torus of the rainbow trout, unit recordings made in the torus were compared with recordings made in the tectum.
The receptive fields (RFs) of the torus units in the rainbow trout (Salmo gairdneri) mostly measured more than 80°, generally had no well-defined borders and showed non-X type behavior. As in the tectum, the majority of the units showed On-responses and the RFs of On units were smaller than those of On/Off and Off units. From single unit and evoked potential data, obtained up to an eccentricity of 45°, it appears that the rostral visual field projects to the rostral and central part of the torus. In contrast to the features of tectal units, the RFs lacked spatial antagonism, wavelength coding was practically absent and directional selectivity rare. The responses, generally with latencies between 40 and 160ms, were often erratic. The most striking neurophysiological feature of the torus units was habituation to repetition of the stimulus, e.g. to an on-off flashing spot. The visuo-auditory interaction of most bimodal units showed algebraic summation, but for about 20% the visual modality enhanced the sensitivity to auditory stimulation.
The data from the trout confirm that the tectum plays an important role in visual functions such as acuity, pattern vision and vision of movement. The common feature of habituation in the torus suggests that the torus may be involved in the signalling of sudden changes in the visual scenery.
Lactate and Glycogen Metabolism in the Lizard Dipsosaurus Dorsalis following Exhaustive Exercise
Authors: Gleeson Todd T. , Dalessio Paula M. 
Published: April 2021

ABSTRACT
We evaluated the metabolic mechanisms by which the iguanid lizard Dipsosaurus dorsalis deals with the lactate which accumulates during vigorous exercise. Fasted, cannulated lizards were run for 5 min on a treadmill at 40°C, which elevated whole-body lactate to 24 mmol l-1 and depleted hindlimb glycogen to 70% of resting levels. Oxygen consumption increased fivefold and respiratory exchange ratios approached 2·0. Exhausted animals were then injected intravenously with either [U-14C]lactate or [U-14C]glucose, and allowed to recover quietly on the treadmill at 40°C. After 2h, 79% of the accumulated lactate had been removed and hindlimb muscle glycogen stores had returned to pre-exercise levels. Although blood glucose remained unchanged at 8·6 ± 0·27 mmol l-1 throughout the recovery period, whole-body glucose increased significantly from 1·6 ±0·23 to 5·5 ± 0·38mmoll-1 (P&lt;0·05). Based on isotope distribution, 50% of the lactate removed was used to synthesize glucose and glycogen, but only 16 % of the lactate was oxidized. Lactate oxidation accounted for about 40% of the post-exercise oxygen consumption. Lactate rather than glucose appeared to be the prevalent substrate for muscle glycogen synthesis under these conditions. These animals appear to employ a strategy of lactate removal which is different from that in mammals; favoring lactate-supported gluco-and glyconeogenesis and rapid muscle glycogen replenishment instead of rapid lactate removal via oxidative pathways.