bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Aerial Exposure on the Distribution of Body Water and Ions in the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Taylor E. W. , Tyler-Jones R. , Wheatly M. G.
Published: April 2021

Submerged crayfish had a total body water content of 76% body mass. Haemolymph volume was around 30% and was dependent on mass, the relationship being described by the regression equation y (volume) = 3·98+0·177x (mass). The inulin space was greater than the copper space in abdominal muscle, suggesting the existence of an interstitial component of the extracellular fluid into which haemo-cyanin does not penetrate. Crayfish exposed to water-saturated air (100% relative humidity, RH) did not lose mass and haemolymph levels of K+ and Na+ were unchanged from the submerged values. When exposed to air (70-80% RH) crayfish progressively dehydrated at the rate of 0·38 % body massh-1 (0·5 % body water h-1) and died after 72 h when 27 % of initial mass had been lost. After a 10 % reduction in mass, haemolymph volume was significantly reduced to about 75 % of its submerged value in 10-g animals and to 65 % in 60-g animals, the decrease in volume being approximately equivalent to the mass lost. After 48 h in air (19% reduction in mass) haemolymph volume was further reduced to 24% of the submerged volume. The total water content of the abdominal muscles showed a small but significant reduction when animals were dehydrated which could be accounted for by a reduction in the extracellular fluid volume, including the interstitial space. After 48 h dehydration in air the osmolarity of the haemolymph increased by 36%, [K+] by 47 % and [Cl-] by 57 % above the submerged levels whilst [Na+] showed an insignificant decrease of 10%. In the abdominal muscle [K+] increased by 15 %, [Na+] increased by 23 % and [Cl-] decreased by 27 %. [Caz+] levels in the haemolymph doubled after 24 h in air, an increase which was independent of the degree of dehydration. The increase is thus a result of emersion and not dehydration and may be due to a mobilization of CaCO3 from the exoskeleton to buffer a respiratory acidosis, as it corresponds to a doubling in [HCO3- + CO32-]. A substantial loss of ions from the haemolymph during dehydration cannot be fully accounted for by uptake into the tissues or by urinary losses, but a 500 mmol 1-1 increase in the Na+ concentration of the proventricular contents suggests that the foregut may play an important role in ionoregulation.
Intracellular Free Potassium, Sodium and Chloride Measured with Ion-Selective Microelectrodes from Salivary Gland Cells of the Snail Planorbis Corneus
Authors: Barber Andrew
Published: April 2021

Double-barrelled, ion-selective microelectrodes (ISMEs) have been used to measure the intracellular free concentrations of K+ ([K+]1), Na+ ([Na+]1) and Cl- ([Cl-]1), together with membrane potentials (EM), from single salivary gland acinar cells of the pond snail Planorbis corneus. After adjustments had been made for the cross-sensitivities of the ion-exchangers to other intracellular ions, the mean concentrations were estimated to be: [K+]1, 42·9mmol1-1; [Na+]1, 2·4mmol1-1; and [Cl-]1, 10·3 mmol 1-1. The mean Nernstian equilibrium potentials for K+, Na+ and Cl- were calculated to be —88 mV, +74·4mV and —41 mV, respectively. The basolateral membrane of Planorbis salivary cells appears to be permeable to K+ and Na+ under resting conditions, because blocking the electrogenic Na+/K+ pump with K+-free saline or ouabain revealed the presence of a large passive efflux of K+ and an influx of Na+. Salivary gland cells also lose intracellular Cl- rapidly in CD-free saline (extracellular Cl- replaced by sulphate) which, along with other evidence, indicates a substantial resting permeability of the salivary cell membrane to Cl-. Stimulating gland cells with 10−4 mol 1-1 acetylcholine (ACh) led to a depolarization of EM1 a rise in [Na+]1 and a fall in [K+]1. This was followed by a transient hyperpolarization of EM and a recovery of [Na+]1 and [K+]1 to their original levels. There was no evidence that [Cl-]1 changes after stimulation with ACh. The mechanism of action of ACh on Planorbis salivary gland cells and its relevance for secretion are discussed.
Turning flight of bats
Authors: Aldridge H. D.
Published: April 2021

The turning flight of six microchiropteran bat species is described. The bats’ abilities to turn tightly were determined by their abilities to fly slowly and to generate high lateral accelerations. Rhinolophus ferrumequinum developed high lateral accelerations by flapping its banked wings while flying at very low speed. Plecotus auritus turned at relatively low speed and at low lateral acceleration. The other species were all moving fast as they turned and generated lateral accelerations either by developing high bank angles or by flapping their wings with low bank angles. There was a significant correlation between wing loading and turning curvature, indicating that low wing loadings improve manoeuvrability.
Precision and Dynamics of Positioning by Canada Geese Flying in Formation
Authors: Hainsworth F. Reed
Published: April 2021

A method is described for reconstructing perspective-distorted film images of geese flying in V formations to allow measurements of wing tip spacing (WTS, the distance between wing tips of adjacent birds perpendicular to the flight path) and depth (the distance along the flight path between birds). Measurements for eight formations are used to test for savings in induced power from wing placement in a vortex field generated by other wings, using the model of Lissaman & Schollenberger (1970) to estimate savings. The median WTS for 55 geese corresponded to an induced power saving of 36%, about half the maximum possible. There was considerable variation in WTS between and within formations. Some birds maintained WTS close to an optimum for saving energy; others maintained WTS with excessive gap. Birds at the apex and those at large depths achieved low energy savings. Savings were enhanced by periodic changes in flight direction in response to variations in the position of the bird ahead. Individuals in some formations adjusted WTS more rapidly when they were displaced a greater distance from the optimum, and some position adjustments appeared to reflect the distribution of savings predicted from vortex theory.
Role of glycolysis in adenylate depletion and repletion during work and recovery in teleost white muscle
Authors: Dobson G. P. , Hochachka P. W.
Published: April 2021

Measurements of metabolite concentrations before and immediately after swimming of trout to exhaustion indicate that all three potential endogenous fuels of anaerobic metabolism [glycogen, phosphocreatine (PCr) and adenosine triphosphate (ATP)] are utilized during anaerobic white muscle work. Lactate, H+, creatine, Pi, NH4+ and inosine monophosphate (IMP) are formed in the process. Glycolysis is considered to be functionally (if loosely) coupled to adenylate depletion by setting up conditions favouring AMP-deaminase-catalysed formation of IMP and NH3. During recovery under these experimental conditions, glycolysis appears to outcompete oxidative metabolism as an ADP acceptor; therefore, in this kind of white muscle, glycolysis is also linked to IMP reconversion to AMP and thus to adenylate replenishment. The net process generates H+, which is why ATP replenishment must be completed before PCr concentrations can be returned to pre-exercise values.
Glycogen Content and Release of Glucose from Red blood cells of the Sipunculan Worm Themiste Dyscrita
Authors: Ingermann Rolf L. , Virgin Garth L.
Published: April 2021

The coelomic red blood cells, or haemocytes, of the sipunculan worm Themiste dyscrita (Fisher, 1952) were found to contain high concentrations of glycogen: the haemocytes accounted for approximately 56 % of the total glycogen in the organism. Haemocytes, incubated in a glucose-free medium in vitro, released D-glucose into the medium. At 10°C and at a physiological haematocrit, the concentration in the initially glucose-free medium reached physiological plasma levels of D-glucose (0·27 mmol l−1) in about 3 h. The cells continued to release D-glucose and the medium concentration reached about 0·65 mmol l−1 after 24 h. Cells resuspended in plasma also released D-glucose to produce medium concentrations that also appeared to exceed physiological levels. Kinetic analysis of membrane transport of D-glucose suggested that membrane transfer was not the rate-limiting step in this release. Mammalian insulin, epinephrine and glucagon were not effective in influencing D-glucose release. No reduction in the medium concentration of D-glucose could be detected when haemocytes were incubated in 2 mmol l−1 D-glucose in plasma or sea water. The results suggest that the haemocyte is involved in the glucose regulation of the organism, although the regulatory mechanism(s) remains to be elucidated. Furthermore, the results suggest that, in addition to its function in oxygen transport, the red blood cell is the principal storage tissue for glycogen in this organism.
Measurement of Host Curvature by The Parasitoid Wasp Trichogramma Minutum, and Its Effect on Host Examination and Progeny Allocation
Authors: Schmidt J. M. , Smith J. J. B.
Published: April 2021

The parasitoid wasp Trichogramma minutum Riley (Hymenoptera: Chalcidoidea: Trichogrammatidae) adjusts its progeny allocation and host examining behaviour to the exposed volume of its host – an insect egg. The female wasp examines a potential host by walking over its surface while drumming its antennae against it, spending a longer time examining larger hosts. If wasps of different sizes are presented with glass beads of the same diameter, examining time increases significantly the larger the bead is relative to the wasp. Since the wasps’ velocities do not differ with wasp size, the total distance travelled during host examination also increases with relative host diameter.

When large and small wasps are placed on large and small hosts such that the relative curvature is constant, examining time and total path length are the same. Smaller wasps take more steps to travel the same distance, therefore the duration of the examination walk, rather than step number or relative distance, is adjusted to host curvature. This adjustment of examination time may ensure that the surface of hosts of different sizes are examined adequately, despite differences in total area.

Progeny allocation, usually dependent only on exposed host surface area, can be affected by the wasps’ measure of curvature. When hosts are mounted on the tips of thin wires rather than on the substrate, no finite cues dependent on surface area are available to the wasps. Such hosts receive only 25 % more progeny, either in the light or in total darkness, than hosts which are resting on the substrate, demonstrating that an upper limit to clutch size is set by cues dependent on curvature. The structure of the compound eyes suggests that the visual acuity of Trichogramma is insufficient to account for their ability to discriminate between small differences in host curvature. By placing large and small wasps on point-mounted hosts of fixed diameter, we show that the clutch size limit is set according to the relative size of the host.

These observations are discussed in terms of a mechanosensory mechanism of curvature measurement.
Lunar cycles of coho salmon, Oncorhynchus kisutch: I. Growth and feeding
Authors: Farbridge K. J. , Leatherland J. F.
Published: April 2021

Coho salmon (Oncorhynchus kisutch Walbaum) parrs and smolts, maintained in a laboratory under a fixed artificial 12h light: 12h dark photoperiod from the time of hatching, exhibited a pattern of alternating periods of rapid and slow growth in body mass; the peaks and troughs in growth rate were significantly different from one another. The alternating growth rate changes were rhythmic in nature, of approximately 14 to 15 days in length.

Evidence for cyclic patterns of growth in relative length and in food consumption was also found in coho salmon parr. Peak food intake appeared to occur 2–4 days after each peak of growth in relative mass. Although the pattern of growth in relative length was less clear, there was evidence to suggest that growth in length might be out of phase with growth in mass.

There was no pattern of cycling growth rates in coho salmon parr subsampled from a common stock. The significance of this is discussed.

The data suggest that the lunar cycle acts as a Zeitgeber for synchronization of the growth rate rhythms.
Lunar Cycles of Coho Salmon, Oncorhynchus kisutch: II. Scale amino acid uptake, nucleic acids, metabolic reserves and plasma thyroid hormones
Authors: Farbridge K. J. , Leatherland J. F.
Published: April 2021

[14C]glycine uptake by scales in vitro was measured in coho salmon (Onco- rhynchus kisutch Walbaum) smolts at different times during several semi-lunar cycles. There was a clear cyclical pattern of glycine uptake during the semi-lunar period.

Evidence for semi-lunar cycles of liver and muscle RNA:DNA ratios, carcass water content, haematocrit, and plasma triglyceride, glucose and cholesterol levels was also found in coho salmon parrs.

Plasma L-thyroxine (T4) levels exhibited a cyclical pattern during the semi-lunar cycle in parrs sampled in March when plasma T4 levels tended to be low, but no such pattern was seen in parrs sampled in January when the plasma T4 levels were relatively high (l·39–l·88 μg dl−1 in January compared with 0·38–0·83 μg dl−1 in March).

There were no apparent semi-lunar cycles in liver mass:body mass ratios and plasma triiodo-L-thyronine (T3) levels.

Changes in growth parameters (nucleic acid levels and glycine uptake by scales) and the content of nutrient reserves are discussed in relation to the semi-lunar patterns of growth in length, growth in mass, and food intake in this species.
Temperature affects the diffusion of small molecules through cytosol of fish muscle
Authors: Sidell B. D. , Hazel J. R.
Published: April 2021

Undiluted cytosolic extracts were prepared from fast glycolytic muscle tissue of white perch (Morone americanus). Diffusion coefficients (D) through the cytosol preparations were estimated in vitro for a series of selected low molecular weight compounds using an experimental diffusion chamber. Determinations were made at 5° and 25 °C to assess thermal sensitivity of the process. Non-metabolizable analogues of naturally occurring compounds were employed to avoid chemical alteration of solutes by the catalytically competent preparations during diffusion experiments. Kinematic viscosity of cytosolic extracts, which is a major determinant of diffusive resistance, increases from 2·94 ± 0·06 to 5·35 ± 0·02 × l0−2cm2s−1 between temperatures of 25° and 5 °C (Q10 = 1·35 ± 0·01). The diffusion coefficients (D) of D-lactic acid are 2·26 ± 0·84 and 0·79 ± 0·15 × 10−6cm2S−1 at 25° and 5°C, respectively (Q10= 1·84 ± 0·36). The D values of 2-deoxyglucose are 2·87 ± 1·01 and 1·22 ± 0·36× 10−6cm2s−1 at 25° and 5°C (Q10 = 1·75 ± 0·54). The D values of Ca2+ are 2·47 ± 0·28 and 1·09 ± 0·36× 10−6cm2s−1 at 25° and 5°C (Q10 = 2·04 ± 0·36). The D values for the ATP analogue, AMP-PNP, are 0·87 ± 0·33 and 0·81 ± 0·15× 10−6cm2s−1 at 25° and 5°C (Q10 = 0·98 ± 0·12). AMP-PNP is the only compound tested which did not show significant thermal sensitivity of diffusion. Recently reported changes in muscle cell ultrastructure induced by temperature acclimation of fishes may serve to counteract the effect of temperature change on diffusion of key small molecules through the aqueous cytoplasm, thus maintaining flux rates between cellular compartments. These mechanisms may be of considerable import in achieving relative temperature independence of cellular function that is characteristic of many eurythermal aquatic animals.
Neural Control of Heart Beat in the African Giant Snail, Achatina Fulica Férussac: I. Identification of the Heart Regulatory Neurones
Authors: Furukawa Yasuo , Kobayashi Makoto
Published: April 2021

Seven heart regulatory neurones (PON, TAN, TAN-2, TAN-3, d-RCDN, d-LCDN and VG1) were identified in the central nervous system of the African giant snail, Achatina fulica Férussac. Among these neurones, the periodically oscillating neurone (PON) was the most effective heart excitor, producing heart excitation at rather low firing frequencies. The tonically autoactive neurones (TAN, TAN-2 and TAN-3) were tonically firing neurones and their spontaneous activity was found to produce tonic heart excitation which supplemented the myogenic heart activity. There was some evidence that two cerebral ganglion cells (the dorsal right and left cerebral distinct neurones, d-RCDN and d-LCDN) were also likely to be heart excitors although the direct connection to the heart was somewhat doubtful in some specimens. No direct inhibitory neurone was found, but the high firing frequency of the visceral ganglion neurone (VG1) usually produced heart inhibition.
Hearing and Echolocation in the Australian Grey Swiftlet, Collocalia Spodiopygia
Authors: Coles Roger B. , Konishi Masakazu , Pettigrew John D.
Published: April 2021

The frequency sensitivity of hearing in the grey swiftlet, Collocalia spodiopygia, was determined by neuronal recordings from the auditory midbrain (MLD). The most sensitive best frequency response thresholds occurred between 0·8 and 4·7 kHz, with the upper frequency limit near 6 kHz. Spectral analysis of echolocation click pairs revealed energy peaks between 3·0 and 8·0 kHz for the foreclick, compared to 4·0–6·0 kHz for the principal click. The relationship between good hearing sensitivity and click energy peaks in the swiftlet extends about an octave higher than it does in the oilbird (Steatornis caripensis).
Excretion in the House Cricket (Acheta Domesticus): Stimulation of Diuresis by Tissue Homogenates
Authors: Spring Jeffrey H. , Hazelton Shelia R.
Published: April 2021

A new method is described for maintaining cricket Malpighian tubules in vitro. Warmed, oxygenated saline is circulated rapidly past the tubules, while the secreted urine is collected under oil for analysis. This technique allows the cricket tubules to be observed and manipulated for extended periods (6 h), in contrast to their short life (<1 h) using conventional methods. Cricket tubules show extreme sensitivity to oxygen deprivation, such that 15 min of anoxia represents the median lethal dose (LD50) for in vitro preparations. Homogenates of corpus cardiacum (CC) cause the rate of fluid secretion by the tubules to double. The maximum stimulation is dose-dependent over the range 0·01 to 1·0 CC. Homogenates of brain and other ganglia show much smaller stimulatory effects (0·01–0·02 CC-equivalents). Cyclic AMP mimics the increase in secretion rate, but has an inhibitory effect on the smooth muscle of the ureter. Control preparations maintain a urine osmotic pressure (OP) that is hyperosmotic to the bath by 5–10 mosmol l−1. CC homogenate produces a decrease in urine OP to 10–12 mosmol l−1 hypo-osmotic to the bath. This suggests that active solute reabsorption is occurring in the lower tubule or ampulla. Stimulation by CC homogenate increases the urine potassium concentration slightly less than two-fold, whereas the sodium concentration increases by a maximum of five-fold and remains at a higher concentration than potassium throughout the experiment. Tubule secretion rate is drastically inhibited in nominally sodium-free saline.
The Transition to Air Breathing in Fishes: IV. Impact of Branchial Specializations for Air Breathing on the Aquatic Respiratory Mechanisms and Ventilatory Costs of the Swamp Eel Synbranchus Marmoratus
Authors: Graham Jeffrey B. , Baird Troy A. , Stöckmann Wieland
Published: April 2021

The gills, adjacent buccopharyngeal epithelium, and skin of the swamp eel Synbranchus marmoratus (Bloch) function for both aerial and aquatic respiration. Aquatic cutaneous O2 uptake occurs continuously at rates that, while dependent upon aquatic O2 tension , are in direct proportion to body surface area. Branchial aquatic O2 uptake takes place during intermittent ventilation which occurs in proportion to body mass. Because of reductions in the body surface area to volume ratio that occur with growth, cutaneous oxygen uptake comprises a larger percentage of the total oxygen uptake of small fish and, to compensate, large fish ventilate more. The mass exponent for total rate of oxygen uptake (0·894 ± 0·145) is within the range predicted from the contributions of cutaneous (mass exponent 0·651 ± 0·167) and the number of minutes each hour that branchial ventilation occurs (0·378 ± 0·105). Hyperoxia increases cutaneous and reduces branchial ventilation. Total was also reduced in hyperoxia and calculations relating this to the reduction in ventilation time yield ventilatory cost estimates that increase with body size and that are high compared to those of other fish when the large component of cutaneous respiration in this species is considered. Large ventilatory costs reflect gill and branchial apparatus specialization for aerial respiration. Accessory cutaneous respiration and intermittent aquatic ventilation reduce these costs, and intermittent gill use in aquatic breathing, which is the exact analogue of the pattern for branchial respiratory use during air breathing, seems to optimize aquatic O2 uptake with minimal ventilatory cost.
The Growth Stimulation of Blow-Fly Larvae Fed on Fatigued Frog Muscle. II
Authors: Smith G. Pugh
Published: April 2021

It had previously been shown that blow-fly larvae fed on fatigued frog muscle grow to a larger size than controls fed on resting muscle.

I have now demonstrated that the growth-stimulating substance is thermolabile and that it passes from the contracting muscle into the blood stream. It does not accumulate in the liver.

The bacterial flora is equally dense on resting and on fatigued muscle on which fly larvae have fed.
Intracardiac Shunting Revealed by Angiocardiography in the Lizard Tupinambis Teguixin
Authors: Johansen K. , Abe A. S. , Andresen J. H.
Published: April 2021

The central circulation in the lizard Tupinambis teguixin (Linné, 1758) was studied using angiocardiographic techniques. Contrast medium was selectively injected into the vena cava superior, the sinus venosus, the right atrium, and the ventricular subcompartments [the cavum pulmonale (CP) and cavum arteriosum (CA)], following catheterization of the heart from the right jugular vein. Contrast medium injection in the vena cava, sinus venosus, right atrium or CP showed that there was an exclusive and selective passage to the pulmonaryy circulation when injections were made during spontaneous or artificial ventilation. Contrast injection during apnoea showed various degrees of right-left shunting to the left aorta but typically not to the right aorta. There was no observable admixture from the CP to the CA. When contrast medium was injected directly into the cavum arteriosum, there was clear selective filling of the right aorta and the cephalad circulation, as well as a lesser but distinct filling of the left aorta. During systole, there was no admixture from the CA to the CP, but a very slight left-right admixture was discernible during ventricular diastole. The selective passage of contrast medium through the heart of Tupinambis showed a relationship to breathing in the intermittent ventilation pattern of Tupinambis. During apnoea, pulmonaryy flow appears to be impeded: this may reflect right—left shunting to the left aorta. This vessel becomes important in the alternation between a balance of pulmonaryy and systemic flow during breathing and a preference for systemic flow during apnoea.
The Efficiency of Sound Production in Two Cricket Species, Gryllotalpa Australis and Teleogryllus Commodus (Orthoptera: Grylloidea)
Authors: Kavanagh Mark W.
Published: April 2021

Males of Gryllotalpa australis (Erichson) (Gryllotalpidae) and Teleogryllus commodus (Walter) (Gryllidae) produced their calling songs while confined in respirometers. G. australis males used oxygen during calling at a mean rate of 4–637ml O2h−1, equivalent to 27·65 mW of metabolic energy, which was 13 times higher than the resting metabolic rate. T. commodus males used oxygen during calling at a rate of 0·728 ml O2 h−1, equivalent to 4·34mW, which was four times the resting metabolic rate. The sound field during calling by males represents a sound power output of 0·27 mW for G. australis and 1·51×10−3mW for T. commodus. The efficiency of sound production was 1·05% for males of G. australis and 0·05 % for males of T. commodus. Comparison with other insect species suggests that none is more than a few percent efficient in sound production.
Functional design of horse hoof keratin: the modulation of mechanical properties through hydration effects
Authors: Bertram J. E. A. , Gosline J. M.
Published: April 2021

Tensile moduli and J-integral fracture toughness values were determined for horse hoof-wall keratin at four hydration levels. The stiffness of hoof-wall was influenced by water content to a greater degree than is the stiffness of other mammalian hard keratins. Young’s modulus increased from 410 MPa at 100 % relative hydration (RH) to 14·6 GPa at 0% RH. Fracture toughness was maximal (22·8 kJ m−2) at an intermediate hydration (75% RH), which represents a two-fold increase over both fully hydrated and dehydrated material. Maximum fracture toughness occurred at a hydration level which is within the range that has been found in vivo in the hoof wall. These results lead to the hypothesis that the density of secondary bonding sites within the hoof-wall keratin matrix proteins provides the hoof organ with the means to modulate tissue properties, even though this epidermal tissue functions after the cells have died.
Locomotion Energetics of the Ghost Crab: I. Metabolic Cost and Endurance
Authors: Full Robert J.
Published: April 2021

Arthropods possess spectacular diversity in locomotor design. Yet it is not clear what unique constraints, if any, variation in design imposes on mechanics, metabolic energy cost or endurance during terrestrial locomotion. In the present study metabolic energy cost and endurance on a treadmill are measured for an arthropod, the eight-legged sideways travelling ghost crab, Ocypode quadrata (Fabricius). In a second paper the mechanics of locomotion are determined during walking and running over a force plate.

Severe limitations in O2 uptake during exercise are not inherent in the design of a crab’s O2 transport system, which consists of gills and an open circulatory system. The ghost crab’s capacity to elevate oxygen consumption rapidly is correlated with a lesser dependence on anaerobic sources than observed in other crab species. Accelerated glycolysis contributed at the onset of submaximal exercise, before O2 uptake adjustments were completed, but played only a minor role during steady-state exercise. O. quadrata elevated 6·4-to 8-fold above resting rates. The ghost crab’s maximal oxygen consumption was not different from that of an ectothermic vertebrate of the same body mass and temperature, such as a lizard, that uses lungs and a closed circulatory system.

The minimum metabolic energy necessary to move 1 g of crab 1 km (Cmin) decreased as a function of body mass and age. Cmin was comparable to that predicted for vertebrates of a similar body mass and, therefore, appears to be relatively independent of locomotor design. This is consistent with the hypothesis that a similarity in the energetic properties of muscle and elastic structures may result in similar metabolic costs of locomotion.

Endurance capacity did not increase with body mass, as predicted from interspecific comparisons of mammals and lizards. Instead, endurance capacity correlated with the speed at which oxygen consumption was maximal. Mean endurance capacity for ghost crabs was similar to that found for lizards, but was far less than the values predicted for mammals. Ghost crabs could only sustain a slow walk. Running at speeds 20 times faster is possible for short periods, but not without the aid of anaerobic metabolism.
Locomotion Energetics of the Ghost Crab: II. Mechanics of the Centre of Mass During Walking and Running
Authors: Blickhan Reinhard , Full Robert J.
Published: April 2021

Terrestrial locomotion involving appendages has evolved independently in vertebrates and arthropods. Differences in the mechanical design of the locomotor apparatus could impose constraints on the energetics of locomotion. The mechanical energy fluctuations of the centre of mass of an arthropod, the ghost crab Ocvpode quadrata (Fabricius), were examined by integrating the ground reaction forces exerted during sideways locomotion. Crabs used a pendulum-type energy exchange mechanism during walking, analogous to an egg rolling end over end, with the same effectiveness as birds and mammals. Moreover, ghost crabs were found to have two running gaits. A switch from a slow to a fast run occurred at the same speed and stride frequency predicted for the trot-gallop transition of a quadrupedal mammal of the same body mass. In addition, the mass-specific mechanical energy developed over a unit distance was independent of speed and was within the limits measured for birds and mammals. Despite the obvious differences in mechanical design between crabs and mammals, energy-conserving mechanisms and the efficiency of locomotion were remarkably similar. These similarities may result from the fact that the muscles that generate forces during terrestrial locomotion have relatively conservative mechanical and energetic properties.
Na+-Cl−-Glutamate Cotransport by Lobster Hepatopancreatic Brush Border Membrane Vesicles
Authors: Ahearn Gregory A. , Clay Laurel P.
Published: April 2021

l-[3H]glutamate uptake by lobster hepatopancreatic brush border membrane vesicles, formed by a magnesium precipitation technique, was stimulated by a transmembrane NaCl gradient (o>i), but not by identical gradients of KCl, TMA-Cl, NaSCN or NaNO3-, suggesting that the amino acid transfer depends specifically upon both Na+ and Cl−. In the presence of a NaCl gradient (o>i), glutamate uptake was strongly dependent upon bilateral pH and increased markedly as pH was lowered from 7·0 to 4·0. NaCl-dependent l-[3H]glutamate uptake was not trans-stimulated by preloading vesicles with K+. At pH 5·0, NaCl-dependent glutamate uptake occurred by an electroneutral process, whereas Na+-dependent d-[3H]glucose uptake at this pH was electrogenic. l-[3H]glutamate influx exhibited both carrier-mediated and apparent diffusional transport components. Decreasing pH had no significant effect on glutamate influx (Kt), but tripled both maximal carrier-mediated entry rate (JM) and the apparent diffusional permeability (P) of the membrane to this compound. l-[3H]glutamate influx was strongly trans-stimulated by vesicles preloaded with l-and d-glutamate, l-and d-aspartate, l-cysteate, l-tyrosine and l-asparagine, but not by vesicles preloaded with l-leucine, l-glutamine, l-proline, l-alanine or l-lysine. l-[3H]glutamate influx at pH 4·0 was a hyperbolic function of both external Na+ and Cl− concentrations at fixed concentrations of the respective counterions, suggesting cotransport between the amino acid and the two ions with a stoichiometry of 1 Na+ : 1 Cl− : 1 glutamate.
Effects of Raised [K+]o And [Ca2+]o on Conjugation and on Electrophysiological Parameters in the Marine Ciliate Euplotes Vannus
Authors: Lueken W. , Krüppel T. , Gaertner M.
Published: April 2021

Co-stimulation of mixed complementary mating types of Euplotes vannus was blocked if [K+]o was raised to at least 60 mmol l−1. This inhibition could be cancelled by simultaneously raising [Ca2+]o. An electrophysiological investigation showed that elevation of either [K+]o or [Ca2+]o depolarized the cell. The effect of potassium was observed at concentrations above 50 mmol l−1, with a slope of about 38 mV/decade change, and was accompanied by a reduction in membrane resistance. Calcium had an effect at lower concentrations than potassium, but the slope was lower, and was associated with a rise in resistance. When potassium and calcium were applied together in ratios at which the calcium level was just sufficient to annul the K+-induced block of conjugation, the membrane was depolarized only slightly more than in potassium alone, and resting resistance was near the control level. It is therefore proposed that high [K+]o blocks co-stimulation by acting upon membrane resting conductance.
Regulation of Labellar and Tarsal Taste Thresholds in the Black Blowfly, Phormia Regina
Authors: Sudlow Leland C. , Edgecomb Robert S. , Murdock Larry L.
Published: April 2021

Regulation of taste thresholds in the blowfly, Phormia regina Meigen, was investigated by manipulating the nutritional status of the insect and determining the effect on labellar and tarsal taste thresholds. Two feeding paradigms were employed: single meals administered to hungry flies, and ad libitum feeding of aqueous sucrose solutions for 4–5 days.

Flies which had fed on aqueous sucrose for several days exhibited high labellar and tarsal thresholds, with tarsal thresholds always higher than labellar thresholds. Food deprivation caused labellar and tarsal thresholds to decline. There was a positive logarithmic relationship between crop mass and labellar or tarsal thresholds. Consumption of single meals of aqueous sucrose caused increases in labellar thresholds similar to those for tarsal thresholds.

Labellar thresholds in flies fed ad libitum were not affected by transection of the recurrent nerve (RN) or the median abdominal nerve (MAN). Tarsal thresholds, in contrast, were markedly attenuated by RN transection but not by MAN transection. Transection of the RN in hungry flies prior to feeding them a single meal did not prevent the normal post-prandial rise in labellar thresholds. In earlier experiments, RN transection has been shown to attenuate the post-prandial rise in tarsal thresholds.

It appears that labellar and tarsal thresholds in the blowfly are similarly affected by consumption of aqueous sucrose. However, inhibitory feedback from the RN, which is partially responsible for elevation of tarsal thresholds after a meal, does not affect labellar thresholds. Additional, still unidentified, factor(s) may regulate both labellar and tarsal thresholds.
Correlation of Electrical and Mechanical Activity of Holothurian Muscle
Authors: Hill Robert B.
Published: April 2021

Spontaneous contractions of segments of an isolated longitudinal muscle of Holothuria cinerascens are not propagated across a sucrose gap. Asynchronous spiking and spontaneous depolarizations leading to contraction can be recorded independently on each side of the gap. Caffeine-induced contractures are not the result of depolarization. Depolarization with KCl temporarily restores contractility lost in a series of caffeine-induced contractures. Acetylcholine causes a depolarization which induces contraction. Individual muscle units may spike quite independently as depolarization progresses in a spontaneous contraction.
The Influence of Hyperoxia, Hypoxia and Temperature on the Respiratory Physiology of the Intertidal Rockpool Fish Gobius Cobitis Pallas
Authors: Berschick P. , Bridges C. R. , Grieshaber M. K.
Published: April 2021

The influence of hypoxia, hyperoxia and temperature on the oxygen consumption, heart rate and ventilation frequency of the intertidal rockpool fish Gobius cobitis Pallas were investigated to examine the respiratory adaptations of this species to intertidal conditions.

The standard mass-specific oxygen consumption during normoxia, calculated for a 50-g fish, averaged 1·27 mmol O2 kg−1 h−1 at 12·5°C and 3·62mmol O2kg−1 h−1 at 25°C. The Q10 value for oxygen consumption averaged 2·3.

During a stepwise reduction of oxygen partial pressure the oxygen consumption was maintained down to a critical oxygen tension, Pc, of approximately 43 Torr (1 Torr = 133·3 Pa). Ventilatory frequency increased progressively while heart rate remained constant until the was reduced below 16 Torr.

During hyperoxic exposure , oxygen consumption remained constant at 12·5 and at 25°C (Q10 = 2·3). Hyperoxia had no effect on heart rate, although ventilation frequency decreased with increasing (to the same extent at both temperatures), indicating the overriding effect of hyperoxia on ventilatory frequency.

Gobius cobitis appears to be well-adapted to the respiratory stresses which occur on a daily basis within intertidal rockpools.
Short Communication: Allometry of Lung Volume During Voluntary Submergence in the Saltwater Crocodile Crocodylus Porosus
Authors: Wright Jonathan C. , Kirshner David S.
Published: April 2021

During submergence, the volume of gas stored in the lungs of a reptilian diver functions not only as an O2 store and CO2 sink (Lenfant, Johansen, Petersen & Schmidt-Nielsen, 1970; Burggren & Shelton, 1979; Seymour, 1982) but can also be adjusted to achieve the desired buoyant state. Lung volume during voluntary submergence will often be a compromise between these two basic functions and should also increase with body mass. The relationship between submergence lung volume and body mass will depend on how tissue density and specific gravity selected by a submerged animal vary with body mass. Previous studies have determined the relationship between lung volume and body mass in reptiles from maximally inflated lungs of dead specimens and have calculated an interspecific scaling factor of 0·75 (Tenney & Tenney, 1970; Wood & Lenfant, 1976). This suggested that the lung volume of a reptile may scale in accordance with mass-specific aerobic metabolism which also has a scaling factor close to 0·75 (Tenney & Tenney, 1970). Although equations generated from interspecific data from maximally inflated lungs are useful for describing certain morphological characteristics of reptilian lungs (Perry, 1983), they are probably inappropriate for determining the lung volume selected by a conscious, undisturbed reptile while voluntarily submerged.
Intestinal Salt Absorption in the Stenothermic Antarctic Fish, Notothenia Rossii
Authors: Gibson J. S. , Ellory J. C.
Published: April 2021

All Antarctic fish studied so far show two adaptive strategies to life at sub-zero water temperatures; antifreeze glycoproteins, which act non-colligatively to inhibit ice propagation (DeVries, 1983), and elevated plasma electrolyte levels (150–200mosmolI−1 higher than that of temperate marine teleosts: Holmes & Donaldson, 1969; Dobbs & DeVries, 1975; O’Grady, Ellory & DeVries, 1983), equivalent to a freezing point reduction of 0·4°C. However, Prosser, Mackay & Kato (1970) have argued that the elevated plasma Na+ concentration is an energy-saving device, resulting in a smaller concentration gradient between fish plasma and salt water, which allows the composition of the former to be maintained at a lower metabolic cost.
Arterial Haemodynamics in the Cephalopod Mollusc, Octopus Dofleini
Authors: Shadwick Robert E. , Gosline John M. , Milsom William K.
Published: April 2021

Simultaneous measurements of blood pressure and blood flow were made in the dorsal aorta of the cephalopod Octopus dofleini Wülker. In resting animals the heart rate varied from 8 ·5 to 14 beatsmin−1, while aortic pressure typically ranged from about 2·5 kPa at end diastole to 5 ·5 kPa at peak systole. Blood flow rate varied with pressure, averaging 0· 9mls−1, with peak flow rates of l·4–2·8mls−1. A slow asymptotic decline in both pressure and flow during the 2- to 4-s diastolic period indicated that the aorta functions as an elastic reservoir, as previously predicted. Aortic impedance spectra were derived from digitized pressure and flow data. The impedance amplitude decreased continuously with increasing frequency, while the impedance phase was always negative. These results are consistent with a two-element Windkessel model of the arterial system. The apparent pressure wave velocity, determined from transit times of pressure pulses in vivo, was >10ms−1. This was much higher than the intrinsic wave velocity we predicted from in vitro measurements of aortic elasticity. This anomaly occurred because the length of the aorta represented less than 1 % of the wavelength of the fundamental pulse frequency, due to the low heart rate in this species. Consequently, arterial haemodynamics in O. dofleini are dominated by strong wave reflections, but do not exhibit other wave propagation effects which are typical of mammalian circulatory systems. Thus, the simple Windkessel model adequately describes the arterial circulation of this species of cephalopod.
Oxygen Consumption of the Isolated Heart of Octopus: Effects of Power Output and Hypoxia
Authors: Houlihan D. F. , Agnisola C. , Hamilton N. M. , Genoino I. Trara
Published: April 2021

A technique is described which allowed the measurement of the oxygen consumption of the isolated heart of Octopus vulgaris. Contraction of the heart resulted in an aortic output and a flow through the heart muscle into coronary veins (the coronary output). The flow and oxygen content of the aortic output and the coronary output were measured with variable input pressures and constant output back pressure (volume loaded), variable output back pressure and constant aortic output (pressure loaded), and during hypoxia. Volume loading of the heart resulted in an increase in aortic output, power output and total oxygen consumption. Pressure loading increased power output and total oxygen consumption of the heart. Exposure to hypoxia decreased the aortic output, power output and total cardiac oxygen consumption. In the response of the heart to reduced work, brought about either by a reduced input pressure or by hypoxic perfusate, the power output was linearly related to the total oxygen consumption of the heart.

The oxygen extracted from the coronary output accounted for 80–100% of the total oxygen consumption of the heart. Coronary output amounted to 30% of the total cardiac output at maximum power output. In volume-loaded hearts the volume of the coronary output increased as aortic output increased ; in pressure-loaded hearts coronary output increased as power output increased, but aortic output remained constant. In hypoxia, the coronary output increased as the aortic output fell. At a perfusate of around 50Torr (1 Torr = 133 Pa), the aortic output ceased although the heart continued to beat and the coronary output continued, accounting for all of the oxygen consumption of the heart. The coronary output flow in vitro therefore has the capacity to be varied independently of the aortic output flow to maintain the oxygen supply to the perfused cardiac muscle.
Ionic Permeabilities of the Isolated Gill Cuticle of the Shore Crab Carcinus Maenas
Authors: Lignon J. M.
Published: April 2021

Electrical parameters of the cuticle of the posterior gill lamella of the shore crab Carcinus maenas, were measured. When the cuticle was perfused with crab saline (CS) inside and sea water (SW) outside, ionic replacements or dilutions of the bathing solutions produced changes in potential that showed a selective permeability to cations with respect to anions. Similar measurements made with the cuticle bathed in single salt solutions gave the following permeability sequence: NH4+ > Rb+ > Cs+ > K+ > Na+ ≈ Ca2+ > Li+ > Tns+ > Mg2+ > HCO3−> CH3COC− > cl−>so42−.

From conductance measurements, the permeability of the cuticle to Ca2+ and Na+ was about 10−3cms−1. K+ and NH4+ were about five times more permeant, while Mg2+ permeability was 5 × 10−5 cm s−1. The permeability of the cuticle to anions 1 ay between 10−6 and 10−5cms−1. In addition, the cuticle showed an asymmetrical behaviour. These results suggest that the low anionic cuticular permeability can interfere with ionic exchanges across the whole gill.
Blood Flow and Pressure Changes in Exercising Octopuses (Octopus Vulgaris)
Authors: Wells M. J. , Duthie G. G. , Houlihan D. F. , Smith P. J. S. , Wells J.
Published: April 2021

Pressure and flow were recorded from the dorsal aorta of freely moving Octopus vulgaris at rest and in exercise. Mean blood pressure, the amplitude of pressure pulses and flow all double as the animal moves about. Frequency changes little in exercise, indeed the increased pulses may be associated with a small drop in heartbeat frequency. There is little or no scope for expansion of arteriovenous oxygen content difference. So the increase in cardiac output necessitated by exercise must be achieved almost solely by an increase in the stroke volume of the systemic heart.

Jet propulsion is accompanied by cardiac arrest. Measurements of internal mantle pressures during jetting and of the pressure pulses generated by peristalsis of the great veins suggest that the venous system is incapable of returning blood against the gradients produced by the rise in mean mantle pressure. Since the oxygen debt that can be sustained by Octopus is quite small (≈22mlO2kg−1), jet-propelled movement is impossible for distances of more than a few metres.

Problems of the maintenance of a circulation in an animal with a high metabolic rate and the basic body plan of a mollusc are discussed, and the situation in squid is compared with that in octopuses.
The Contractile Properties of a Crab Respiratory Muscle
Authors: Josephson Robert K. , Stokes Darrell R.
Published: April 2021

Contraction of scaphognathite muscle L2B of the green crab Carcinus maenas is strongly dependent on stimulus number and frequency. Single, supramaximal stimuli evoke little or no tension. When stimulated with shocks in either short bursts (10 stimuli in 0·5 s or less) or long bursts (5 s of stimulation), the isometric tension from the muscle increases with increasing stimulus frequency to a maximum at about 150 Hz at 15°C, beyond which tension declines with further increase in stimulus frequency. There can be facilitation of both contraction and relaxation between short bursts of stimuli. Facilitation of contraction is seen as increasing tension on successive bursts of a series, even when the interburst interval is long enough for relaxation to be completed during the interval. Interburst facilitation lasts at least 10 s. Facilitation of relaxation is seen as progressively faster relaxation from burst to burst of a series, and relaxation to lower tension levels when the interburst interval is so short that relaxation is incomplete in the interburst interval. Maximum isometric tension occurs at muscle lengths slightly longer than the longest muscle length reached in vivo. Tension declines rapidly with changes in muscle length away from the optimum length. The maximum isometric tension was about 12 N cm−2. The maximum shortening velocity of a tetanically activated muscle was determined as 1·9 lengths s−1 (Ls−1) by extrapolation of force-velocity curves to zero force and 3·3 Ls−1 by slack test measurements. The scaphognathite muscle would be classified as a slow or tonic muscle on the basis of its requirements for multiple stimulation to reach full activation, and as a moderately fast muscle on the basis of its force-velocity properties.
Salt and Water Regulation in Macrobdella Decora (Hirudinea: Gnathobdelliformes) Under Osmotic Stress*
Authors: Wenning Angela
Published: April 2021

The anatomy, ultrastructure and innervation of the nephridia of the North American leech, Macrobdella decora (Say), are described. The osmotic concentrations of blood, crop fluid and final urine, as well as urine flow under normal conditions, were found to be similar to those of the well-studied European medicinal leech, Hirudo medicinalis L.

The capacity of the excretory system after changes in external salinity, and after salt and water loading with artificial blood meals, was investigated. In contrast to H. medicinalis, M. decora does not tolerate hypertonic environments and is less efficient in rapidly excreting excess salt and water. Three factors make salt and water regulation in M. decora different from that in H. medicinalis; a slower fluid resorption from the crop, a limited transport capacity of the primary urine-forming cells, and a lower rate of salt reabsorption in the central canal.