bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological Properties of Afferents from Tactile Hairs on the Hindlegs of the Locust
Authors: Newland Philip L.
Published: April 2021

The spatial distribution and physiological properties of the tactile hairs and their sensory afferents of the hindlegs of the locust Schistocerca gregaria are described. Hairs occur in a consistent position from animal to animal. Hairs on the dorsal tibia are of a greater mean length, 403.1 ±17.9 μm, than hairs on the ventral tibia, 265.2±10.44μm. Hairs on the dorsal and ventral femur are approximately 310μm long and hairs on the tarsus are shorter, approximately 200 μm. Based on their threshold responses to sinusoidal mechanical stimulation, the tactile hairs are of two basic physiological types. High-threshold hairs occur only on the proximal dorsal tibia and at the proximal base of each tibial spine, whereas low-threshold hairs are found on the femur, tibia and tarsus. High-threshold hair afferents respond phasically to imposed deflections of the hair shaft and have mean velocity thresholds of 21.1±4.2°s−1. They adapt rapidly to repetitive stimulation, after as few as 11 cycles at 5Hz. Low-threshold hairs respond in a more phaso-tonic manner to imposed deflections and have velocity thresholds of less than 3°s−1. They adapt to repetitive stimulation at a similar rate to the high-threshold hairs, but continue to respond to stimulation after 200 cycles at 5 Hz. All the hairs are directionally sensitive, with the preferred direction being oriented proximally and medially (i.e. proximally and towards the body); they are least sensitive to deflections in the opposite direction.
Field Measurements Of Hanging Flight Aerodynamics In The KestrelFalco Tinnunculus
Authors: Videler John , Groenewold Alex
Published: April 2021

Hunting kestrels were observed to hang, almost without wing-flapping, in fixed positions over a sea dike. The height and position with respect to the dike profile, the wind direction and velocity and the percentage of hunting time without wing beating were recorded in 429 cases.

The vertical wind angle, θ, the wind speed and its horizontal direction were measured at 13 heights up to 8.8m above the windward slope, the top and the leeward slope of the dike under various wind conditions in 225 cases. These wind profile measurements were used to estimate θ and wind speed near the hanging birds.

Kestrels hanging more than 90% of the hunting time preferred a position 6.5±1.5m (S.D.) over the windward slope with sea winds blowing at 8.7± 1.5 ms-1 (S.D.) perpendicular (±30°) to the longitudinal dike axis. For these birds angle θ was approximately 6–7°.

These angles are larger than expected from aerodynamic models and windtunnel measurements. The minimum gliding angle for a kestrel under steady conditions is estimated to be 5°.

Hanging kestrels save two-thirds of the energy used during normal windhover-ing but have to spend 1.6 times more time to catch the same number of voles.
The Movement of the Egg Nucleus in Relation to the Sperm Aster in the Echinoderm Egg
Authors: Chambers Edward L.
Published: April 2021

The names of O. Hertwig, H. Fol, E. Selenka, W. Roux, H. E. Ziegler, E. B. Wilson, and E. G. Conklin are associated with the classic observations on the migration of the male and female pronuclei in the inseminated egg. These workers advanced several interpretations to account for the migration. Later R. Chambers (1917) presented evidence that the aster is a gelated body and that the astral centre is the centre of centripetally directed cytoplasmic currents. On the basis of this interpretation of the aster, a reinvestigation was made of the movements of the pronuclei.
The Influence of Anterior-Pituitary and Testicular Hormones on the Sexual Maturation of Lampreys
Authors: Knowles F. G. W.
Published: April 2021

Sexual maturity in lampreys is accompanied by modifications of the cloacal region. Thc cloacal labia become swollen by an infusion of blood and ""ducts"" form, which lead from the coelom to the mesonephric ducts. These ""ducts"" are not present in the immature adults or ammocoete larvae. These changes may be produced in the immature adults and ammocoete larvae, by injections of a mammalian-pituitary preparation. In the ammocoetes the response to even a small dose was very rapid, ducts being formed in many cases twenty-four hours after the injection of I mg. of A.P. 15 B. Testosterone and oestrone also produced these modifications in the adult, but not in the larva. Spermatogenesis of the adult was slightly affected by gonadial hormones and pituitary preparations. The gonads of the larvae were not affected by gonadial hormones or pituitary preparations in the doses used. The rapidity of the cloacal response to the injections of pituitary preparations in ammocoetes suggests that this response is of a direct nature. The absence of changes in the gonads of injected ammocoetes supports this view.
Effects of Environmental Factors on Exercise In Fish
Authors: Randall David , Brauner Colin
Published: April 2021

The critical swimming velocity of fish is affected by environmental conditions and the highest swimming speed is obtained only under specific circumstances. The mechanisms causing a reduction in exercise capacity depend on the type of environmental change. Acid waters exert an effect by reducing oxygen transport capacity, whereas reduced temperatures act largely on muscle contractility. Alkaline conditions and salinity change may affect both gas transport and muscle contractility.

A fish must operate over a wide range of internal and external conditions and must possess both short- and long-term mechanisms to maintain function under a wide variety of conditions. These mechanisms may be part of the immediate reflex arsenal available to the fish (for example, catecholamine release) or they may be mechanisms induced during acclimation. The nature of the acclimation process is an indication of what may be limiting exercise under a particular set of circumstances.

The concept of symmorphosis, especially when applied to ectotherms, needs to be viewed in a broader context. A symmetry of component parts may exist such that structures are designed to satisfy functional requirements for operation over a wide range of conditions, rather than optimally for a given set of conditions. This must involve compromises in design, especially for ectotherms such as fish. Thus, the more variable the conditions under which a system must operate, the less apparent it will be that symmorphosis exists between the component parts.
Conditions for Oxygen and Substrate Transport in Muscles in Exercising Mammals
Authors: Hoppeler Hans , Billeter R.
Published: April 2021

The structural conditions relevant for metabolite exchange in anaerobic and aerobic work conditions in muscle tissue are reviewed. High-intensity non-steadystate exercise is supported by the phosphocreatine pool, which serves as a shuttle for high-energy phosphates produced by glycolysis and by aerobic metabolism. This is achieved through the intermediary of a topologically organized creatine kinase isozyme system. The muscle capillary network supplies substrate and environmental oxygen to the mitochondria. The network is quantitatively matched to the muscle oxidative capacity, determined structurally by mitochondrial volume. Capillary hematocrit, erythrocyte spacing and oxygen saturation of myoglobin are critical variables for oxygen release from microvessels. Myoglobin greatly helps intracellular oxygen transfer as, under aerobic work conditions, it keeps intracellular oxygen tension low and uniform in the muscle fibers. During sustained submaximal work, muscle cells are fueled by both endogenous (triglycerides and glycogen) and circulatory (lactate, glucose and fatty acids) substrates. A lactate shuttle in which lactate may move through the circulation, as well as directly from fiber to fiber, provides many of the carbohydrate-derived carbon skeletons for terminal oxidation. Glucose is taken up from the interstitial space by facilitated diffusion, mostly mediated by a glucose transporter (GLUT4) that is translocated from an intracellular location to the sarcolemma by activity and insulin. Extramyocellular transport of fatty acids is mediated by albumin, while fatty-acid-binding proteins are held responsible for intracellular fatty acid transport.
Gravity-Induced Changes in Propulsion of Paramecium Caudatum: a Possible Role of Gravireception in Protozoan Behaviour
Authors: Ooya Mayumi , Mogami Yoshihiro , Izumi-Kurotani Akemi , Baba Shoji A.
Published: April 2021

The swimming behaviour of Paramecium was analyzed under natural and experimental hypergravity conditions. Paramecium that swam upwards (in the opposite direction to the gravitational force) along a straight path (straight swimmers) swam more slowly than those swimming downwards. This dependence of the swimming velocity on its direction relative to gravity can be partly interpreted as the consequence of sinking due to gravity if the propulsive force does not vary. The effect was different for Paramecium swimming along a circular path (curved swimmers). The difference in velocity between those swimming upwards and those swimming downwards was substantially smaller than would have been expected from sinking effects with invariant propulsion even after correcting for maximal hydrodynamic wall effects, indicating that Paramecium compensate for sinking caused by gravity by controlling their propulsion. The propulsive velocity evaluated by vector calculus increased both as Paramecium swam more sharply upwards and as the experimental gravitational force was increased. The dependence of propulsion on the swimming direction and on gravity was reduced in a high-density medium of nearly neutral buoyancy, suggesting that the site of gravireception is unlikely to be in the interior of the cell. The differences between straight and curved swimmers are discussed in terms of rapid adaptation of gravireceptors in the cell membrane, desensitization of mechanosensory channels and hyperactivation of ciliary activity in straight swimmers.
The Apodeme Complex of the Femoral Chordotonal Organ in the Metathoracic Leg of the Locust Schistocerca Gregaria
Authors: Shelton P. M. J. , Stephen R. O. , Scott J. J. A. , Tindall A. R.
Published: April 2021

The mechanical connections of the metathoracic femoral chordotonal organ (mtFCO) with its insertion at the femoro-tibial joint are described. The apodeme complex is shown to consist of a distal cuticular rod that is replaced proximally by dorsal and ventral ligaments. The dorsal ligament is a direct continuation of the distal rod but proximally it is replaced by ligamentous cells. The ventral ligament has no cuticular core and consists of ligamentous cells throughout its length. The ligaments are composed of bundles of connective tissue cells that are each enclosed in an extracellular matrix containing acid-fuchsin-staining fibrils. Internally the cells are packed with microtubules. During extension and flexion of the joint, the two ligaments move differentially. During passive extension of the tibia, the ventral ligament remains taut but the dorsal one buckles to form a slack loop. Direct observation of living preparations shows that the loop is first detectable during extension of the tibia at joint angles greater than about 51 °. During flexion, the loop gradually tightens and disappears. It has completely disappeared at joint angles of less than about 36°. Changes in loop shape were demonstrable using preparations in which the tibia was moved sinusoidally ±10° about a mean femoro-tibial angle of 90° and photographs were taken using phase-locked illumination. Other details of the apodeme complex are described and the significance of the findings is discussed in relation to mtFCO function.
L-Serine Uptake by Trout (Salmo Trutta) Red Blood Cells: the Effect of Isoproterenol
Authors: Gallardo M. A. , Planas J. , Sánchez J.
Published: April 2021

We studied the uptake of L-serine by trout red blood cells and the effect of a -adrenergic agonist (isoproterenol) on this process. The results obtained indicate that L-serine is taken up by these cells by means of a concentrative process. The uptake seems to be mediated both by a sodium-dependent process and by a sodium-independent process. The sodium-dependent uptake is mediated by a transport system that probably belongs to the ASC system family. Isoproterenol exerts an inhibitory effect on L-serine uptake. This effect is dose-dependent. It is proposed that the inhibitory effect of isoproterenol is mediated by a rise in the intracellular sodium concentration and/or changes in cell volume.
Sensory Inputs Mediating two Opposite Behavioural Responses to Light in the Crayfish Procambarus Clarkii
Authors: Fernández-De-Miguel Francisco , Aréchiga Hugo
Published: April 2021

Crustaceans are attracted out of their burrows by dim light whereas they withdraw in response to light of high intensity. We have studied attraction and withdrawal responses in freely walking crayfish (Procambarus clarkii) and in animals tethered above a treadmill device. Electrophysiological recordings have been made of retinal and extraretinal visual units to determine their possible inputs.

Attraction was induced by light of 0.17– 1.4 lx; the crayfish walked forward with the abdomen extended. Withdrawal was observed at intensities above 5.6lx; the crayfish walked backwards with a cyclic pattern of flexion and extension of the tail. A group of sustaining visual neurones of the optic nerve with low thresholds was found to respond to light in the range of intensities that produced attraction. Two groups of neurones responded in the range of intensities that produced withdrawal: sustaining visual neurones with high thresholds and the caudal photoreceptors. In animals in which the visual fields of the high-threshold fibres had been covered with black paint, the attraction response was not affected, while withdrawal was only observed in response to light stronger than 11 lx. When tested on a treadmill, the latency of the responses to light and the direction of walking of crayfish reflected attraction and withdrawal responses. Moreover, under these conditions, illumination of the eye induced forward walking at intensities that produce attraction and backward walking at intensities that produce withdrawal. In contrast, illumination of the tail induced only backward walking.
Osmolality and Electrolyte Composition of Pleon Fluid in Porcellio Scaber (Crustacea, Isopqda, Oniscidea): Implications for Water Vapour Absorption
Authors: Wright Jonathan C. , O’Donnell Michael J.
Published: April 2021

Active water vapour absorption in Porcellio scaber is associated with the endogenous production of strongly hyperosmotic fluid in the pleoventral chamber (pleoventralraum; PV). Pre-desiccated animals show increased pleon fluid secretion within 1–2 min of transfer to suprathreshold humidities (>87 % relative humidity). The conspicuous increase in fluid volume is accompanied by a rise in osmolality from isosmotic (approximately 750mosmolkg−1) up to as much as 8.2osmol kg−1. Vapour absorption is marked by the onset of metachronal pleopodal ventilation and a subsequent decline in fluid osmolality as uptake fluid approaches equilibrium with ambient water activities. The effects of sealing of the PV by the margins of the depressed pleopods, along with the observation that animals ventilate even when PV fluid activities are somewhat below ambient, suggest that resultant pressure increases may elevate humidity within the PV and thereby augment vapour uptake. Ion-selective microelectrode measurements of Na+, K+, Ca2+ and Cl− concentrations in nanolitre samples of isolated pleon fluid identify Na+ and Cl− as the major osmolytes. Possible preadaptions favouring evolution of vapour absorption in the Oniscidea are discussed.
Ventilation and Gas Exchange During Shallow Hypothermia in Pigeons
Authors: Jensen Chris , Bech Claus
Published: April 2021

Ventilatory control of the composition of the gases in the air sacs was studied during entry into fasting-induced, shallow, nocturnal hypothermia in the domestic pigeon (Columba livia). Respiratory frequency (f), tidal volume (VT) and oxygen uptake were recorded simultaneously in six pigeons; partial pressures of CO2 and O2 in the abdominal and interclavicular air sacs were measured in seven pigeons. Ambient temperature was 25°C (thermoneutral) and the body temperature (Tb) was recorded in all experiments.

A reduction in Tb from 40.5 to 37.5°C paralleled decreases in f and VT from 13.3 min-1 and 15.2 ml BTPS kg-1 to 10.7 min-1 and 12.4ml BTPskg-1, respectively. There was a minor, but non-significant, simultaneous decrease in the ventilatory requirement (total ventilation/O2 uptake) from 0.38 to 0.35 ml BTPS mmol-1. However, in both air sacs the partial pressure of CO2 increased when Tb decreased, indicating an effective parabronchial hypoventilation.

The results support the idea of a gradually developing respiratory acidosis during hypothermia.
An Electrophysiological Characterization of Ciliated Olfactory Receptor Cells of the Coho Salmon Oncorhynchus Kisutch
Authors: Nevitt Gabrielle A. , Moody William J.
Published: April 2021

Electrical properties of ciliated olfactory receptor cells isolated from coho salmon (Oncorhynchus kisutch) were studied using the whole-cell mode of the patch-clamp recording technique.

Voltage-dependent currents could be separated into two inward and three outward conductances, including a Na+ current, Ca2+ current and three K+ currents. The components of the outward current varied with the life stage of the salmon from which cells had been isolated. In cells isolated from juvenile fish (parr), a Ca2+-dependent K+ current dominated the outward current, whereas in cells isolated from older fish (i.e. fish that had undergone smoltification), a transient K+ current became prominent. Differences in response characteristics of outward currents to internal dialysis with cyclic GMP (but not cyclic AMP) were also correlated to the life stage of salmon. Under conditions in which the Ca2+-activated current was blocked, relaxation of the outward current was slowed by dialysis with cyclic GMP only in cells isolated from smolts and sea-run fish, but not in those isolated from mature spawners. From these results, we suggest that hormone modulation of olfactory receptor cell development or differentiation may play a role in establishing these differences.
The Effects of Wing Rotation on Unsteady Aerodynamic Performance At Low Reynolds Numbers
Authors: Dickinson Michael H.
Published: April 2021

The downstroke-to-upstroke transition of many insects is characterized by rapid wing rotation. The aerodynamic consequences of these rapid changes in angle of attack have been investigated using a mechanical model dynamically scaled to the Reynolds number appropriate for the flight of small insects such as Drosophila. Several kinematic parameters of the wing flip were examined, including the speed and axis of rotation, as well as the duration and angle of attack during the wing stroke preceding rotation. Alteration of these kinematic parameters altered force generation during the subsequent stroke in a variety of ways.

When the rotational axis was close to the trailing edge, the model wing could capture vorticity generated during rotation and greatly increase aerodynamic performance. This vortex capture was most clearly manifested by the generation of lift at an angle of attack of 0°. Lift at a 0° angle of attack was also generated following rotation about the leading edge, but only if the downstroke angle was large enough to generate a von Karman street. The lift may be due to an alteration in the effective angle of attack caused by the inter-vortex stream in the downstroke wake. The maximum lift attained (over all angles of attack) was substantially elevated if the wing translated backwards through a wake generated by the previous stroke. Transient lift coefficient values of nearly 4 were obtained when the wing translated back through a von Karman street generated at a 76.5° angle of attack. This effect might also be explained by the influence of the inter-vortex stream, which contributes a small component to fluid velocity in the direction of translation. The growth of lift with angle of attack was significantly elevated following a 7.5 chord stroke with a 76.5° angle of attack, although it was relatively constant under all other kinematic conditions. The results also indicate the discrepancies between transient and time-averaged measures of performance that arise when unsteady mechanisms are responsible for force generation. Although the influence of wing rotation was strong during the first few chords of translation, averaging the performance over as little as 6.5 chords of motion greatly attenuated the effects of rotation. Together, these modeling results suggest that the unsteady mechanisms generated by simple wing flips could provide an important source for the production of aerodynamic forces in insect flight. Furthermore, the extreme sensitivity to small variations in almost all kinematic parameters could provide a foundation for understanding the aerodynamic mechanisms underlying active flight control.
A Locust Octopamine-Immunoreactive Dorsal Unpaired Median Neurone Forming Terminal Networks On Sympathetic Nerves
Authors: Bräunig Peter , Stevenson Paul A. , Evans Peter D.
Published: April 2021

In insects, octopamine is present in neurohaemal regions of the thoracic sympathetic nervous system, but its cellular source is unknown. We describe a dorsal unpaired median neurone (DUM1b) in the locust metathoracic ganglion that forms a meshwork of varicose, presumably neurohaemal, endings on the surfaces of sympathetic nerves. Other targets include several ventral longitudinal muscles, the spiracle closer muscle, tissue remnants of degenerated nymphal muscles and the salivary glands. Using an established antiserum, DUM1b is shown to be octopamine-immunoreactive, and its target muscles to be covered with octopamine-immunoreactive varicosities. Octopamine influences one of these muscles in essentially the same way that another well-described octopaminergic neurone, DUMEti, modulates the extensor tibiae muscle of the hind leg. We propose that DUM1b is an octopaminergic modulator of muscle contractions and may also influence numerous other body functions by releasing octopamine as a hormone from sympathetic neurohaemal areas.
Are Mitochondria Subject to Evolutionary Temperature Adaptation?
Authors: Johnston Ian A. , Guderley Helga , Franklin Craig E. , Crockford Tony , Kamunde Collins
Published: April 2021

Thermal tolerance and the respiratory properties of isolated red muscle mitochondria were investigated in Oreochromis alcalicus grahami from the alkaline hot-springs, Lake Magadi, Kenya. Populations of O. a. grahami were resident in pools at 42.8°C and migrated into water reaching temperatures of 44.8°C for short periods. The maximum respiration rates of mitochondria with pyruvate as substrate were 217 and 284 natom O mg−1 mitochondrial protein min−1 at 37°C and 42°C, respectively (Q10=1.71). Fatty acyl carnitines (chain lengths C8, C12 and C16), malate and glutamate were oxidised at 70–80% of the rate for pyruvate. In order to assess evolutionary temperature adaptation of maximum mitochondrial oxidative capacities, the rates of pyruvate and palmitoyl carnitine utilisation in red muscle mitochondria were measured from species living at other temperatures: Notothenia coriiceps from Antarctica (-1.5 to +1°C); summer-caught Myoxocephalus scorpius from the North Sea (10–15°C); and Oreochromis andersoni from African lakes and rivers (22–30°C). State 3 respiration rates had Q10 values in the range 1.8–2.7. At the lower lethal temperature of O. andersoni (12.5°C), isolated mitochondria utilised pyruvate at a similar rate to mitochondria from N. coriiceps at 2.5°C (30 natom O mg−1 mitochondrial protein min−1). Rates of pyruvate oxidation by mitochondria from M. scorpius and N. coriiceps were similar and were higher at a given temperature than for O. andersoni. At their normal body temperature (-1.2°C), mitochondria from the Antarctic fish oxidised pyruvate at 5.5% and palmitoyl-DL-carnitine at 8.8% of the rates of mitochondria from the hot-spring species at 42°C. The results indicate only modest evolutionary adjustments in the maximal rates of mitochondrial respiration in fish living at different temperatures.
The Lung–Eardrum Pathway in Three Treefrog and Four Dendrobatid Frog Species: Some Properties of Sound Transmission
Authors: Ehret Günter , Keilwerth Elke , Kamada Tsutomu
Published: April 2021

Frequency–response curves of the tympanum and lateral body wall (lung area) were measured by laser Doppler vibrometry in three treefrog (Smilisca baudini, Hyla cinerea, Osteopilus septentrionalis) and four dendrobatid frog (Dendrobates tinctorius, D. histrionicus, Epipedobates tricolor, E. azureiventris) species. The high-frequency cut-off of the body wall response was always lower than that of the tympanum. The best response frequencies of the lateral body wall were lower than those of the tympanum in some species (S. baudini, O. septentrionalis, D. tinctorius), while in the others they were rather similar. Best tympanic frequencies and best body wall response frequencies tended to differ more with increasing body size.

Stimulation of the tympanum by sound transfer through 3.14 mm2 areas of the lateral body wall showed that the lung–eardrum pathway can be in two states, depending on breathing activity within the lungs: 44% (in Smilisca), 39% (in Hyla) and 31% (in Osteopilus) of the eardrum vibrations were 2.5–8 times (8–18 dB) larger when the frogs were breathing with the lungs compared with non-breathing conditions.

The vibration amplitudes of the tympanum and lateral body wall of the treefrogs followed the same dependence on sound intensity, only absolute amplitudes differed between species.

Our results suggest that the lung–eardrum pathway attenuates high-frequency components of species-specific calls and enhances low-frequency components. In addition, an amplitude modulation is imposed on the low frequencies during the rhythm of breathing.
The Olfactory Memory of the Honeybee Apis Mellifera:II. Blocking Between Odorants in Binary Mixtures
Authors: Smith Brian H. , Cobey Susan
Published: April 2021

Proboscis extension conditioning of honeybee workers was used to study the processing of odorants when bees were conditioned to binary mixtures. Responses to a set of pure floral odors and pheromones after conditioning have already been described. When bees are conditioned to certain mixtures of odorants, the response to both components is equal to that when they are tested alone. However, mixtures of an aliphatic aldehyde and an alcohol elicit asymmetric response patterns; that is, the response to the aldehyde is much stronger than that to the alcohol. A bee’s response to the alcohol after it had been trained in an aldehyde background is significantly lower than when the bee is trained to respond to the same alcohol in the background of another odorant. Such response patterns are not necessarily caused by a behavioral decrement resulting from a compound-unique perceptual effect produced by the mixture. Furthermore, studies of blocking show that behavioral acquisition in response to one component can be hindered or blocked by pretraining with the other component. These results suggest that honeybees can perceive the individual components of some binary mixtures. The similarities in neural processing in olfactory systems of vertebrates and invertebrates mean that such studies could elucidate behavioral mechanisms of olfaction in a wide phylogenetic spectrum of animals.
Porters and Neurotransmitter Transporters
Authors: Nelson Nathan , Lill Holger
Published: April 2021

Uptake of neurotransmitters involves multiple transporters acting in different brain locations under different physiological conditions. The vesicular transporters are driven by a proton-motive force generated by a V-ATPase and their substrates are taken up via proton/substrate exchange. The plasma membrane transporters are driven by an electrochemical gradient of sodium generated by a Na+/K+-ATPase. Two distinct families of transporters were identified in this group. One cotransports sodium with glutamate and other amino acids and requires additionally an outwardly directed potassium gradient. The second cotransports sodium, chloride and a variety of neurotransmitters, including γ-aminobutyric acid (GABA), glycine and monoamines. Genes and cDNA encoding several members of the latter family have been cloned and studied in detail. The structure and function as well as the evolutionary relationships among these neurotransmitter transporters are discussed.
Swimming Kinematics of Fast Starts are Altered by Temperature Acclimation in the Marine Fish Myoxocephalus Scorpius
Authors: Beddow Toni A. , Leeuwen Johan L. Van , Johnston Ian A.
Published: April 2021

The swimming kinematics of prey capture was studied in short-horned sculpin (Myoxocephalus scorpius L.) acclimated for 6–8 weeks to either 5 °C or 15 °C (12h:12h light:dark) using 15 °C-acclimated shrimps as prey. Fish acclimated to 5 °C remained interested in feeding following an acute rise in temperature to 15 °C over 12 h. Prey capture was a stereotyped behaviour consisting of stalking and stationary phases, followed by an S-shaped fast-start (stage 1), a propulsive stroke (stage 2) and a glide of variable duration during which the mouth was expanded and protruded to suck in the prey (stage 3). The duration of the preparatory stroke (half tail-beat, stage 1) was significantly shorter at 15 °C (48.8 ms) than at 5 °C (108.3 ms) in the 5 °C-acclimated sculpin (Q10=2.2). For 5 °C-acclimated fish, at 5 °C, the maximum values for acceleration and velocity along the path travelled by the fish were 16.2ms − and 0.8 ms−1 respectively. Both variables were relatively independent of acute temperature change (Q10=1.1-1.2; P>0.1). At 15 °C, the maximum velocity was 33 % higher and the tail-beat duration of the propulsive stroke was 37% shorter in 15 °C-acclimated than in 5 °C-acclimated fish. Both stride length and tail beat amplitude were significantly higher (28 and 23 % respectively) in 15 °C-compared with 5 °C-acclimated sculpin at 15 °C. The results demonstrate plasticity in the major kinematic variables of fast-starts following warm acclimation sufficient to increase the percentage of successful attacks during prey capture from 23.2 to 73.4 %.
Longitudinal Variation in Mechanical Competence of Bone Along the Avian Humerus
Authors: Bonser Richard H. C.
Published: April 2021

Vickers microhardness tests were used to gauge the mechanical ‘competence’ (ability to resist bending and failure) of cortical and trabecular bone along the humeri of three bird species. Hardness was greatest at the mid-length portion of the shaft. The mean hardness of trabeculae, where present, was between 78.7 and 90.9 % of that of the adjacent cortical bone. The possible causes of this are briefly discussed. Microhardness tests offer the opportunity to gauge differences in mechanical properties over small distances and might usefully be applied to test the homogeneity of mechanical properties within specimens for tensile or compressive tests.
Water and Carbon Dioxide Loss From the Cockroach Periplaneta Americana (L.) Measured Using Radioactive Isotopes
Authors: Noble-Nesbitt J. , Appel A. G. , Croghan P. C.
Published: April 2021

Tritiated water (THO) loss from Periplaneta americana is used to measure cuticular permeability (Pd). In dry air, following various periods of predesiccation, the values of Pd lie around 0.5×10−9 m s-1, with the lowest values below 0.3×10−9 m s-1, close to the lowest permeabilities previously reported. There is no obvious relationship between permeability and initial mass of the insect. A significant lowering of Pd was found after 72 h of predesiccation. A marked sudden decrease in permeability occurred when the airstream flowing over an insect was changed from humid air to dry air. Labelling the bicarbonate pool using 14CO32- enabled the output of CO2 to be estimated. An average output of about 390 μl g-1 h-1 was found. Simultaneous measurement of THO and 14CO2 loss showed that tracheal water loss is only a small component of total water loss, with an average value of 3.8 %. The total water loss can therefore be used to make close estimates of cuticular permeability in Periplaneta americana. 2 min sampling periods clearly show the pulsatile nature of 14CO2 release but, even when the effect is most discernible, the periodic release of CO2 has only a small effect on water loss.
Pupil Adjustments in the Eye of the Common Backswimmer
Authors: Ro Alf-Inge , Nilsson Dan-E.
Published: April 2021

The pupil mechanism in the acone apposition eye of the semi-aquatic common backswimmer Notonecta glauca (Hemiptera) was investigated with infrared reflectometry of the pseudopupil. This method allows non-invasive continuous measurements of pupil responses in the living animal. The dynamic range of the pupil sensitivity is about 7 log units during daytime and 6 log units at night. During the day, the sensitivity range of the pupil covers the normal daylight intensities in the animal’s habitat, just under the water surface (I50=1019.2 photons m−2 sr−1 s−1). At night, the sensitivity is 1 log unit lower (I50=1020.2 photons m−2 sr−1 s−1), ensuring that the pupil is maximally open when light intensities are low. During daytime, light adaptation is completed in slightly less than 40 min, and dark adaptation takes approximately 50 min. The pupil response is only slightly slower at night. The speed of the response as well as the pupil sensitivity are dependent on the preceding adaptation history. An endogenous circadian rhythm determines the control range of the pupil aperture. However, the rhythm is easily disturbed, especially within a 3 h period before dusk and dawn. The results are compared with corresponding results from other insects with the same type of pupil mechanism.
Aquatic Surface Respiration, Buoyancy Control and the Evolution of Air-Breathing in Gobies (Gobiidae: Pisces)
Authors: Gee John H. , Gee Phyllis A.
Published: April 2021

The role of a buccal gas bubble, held while performing aquatic surface respiration (ASR; ventilating the gills with surface water during hypoxia), was examined in benthic, intertidal Australian gobies (Favonigobius tamarensis, F. exquisitus, Pseudogobius olorum, Chlamydogobius sp., Mugilogobius paludis, Cryptocentroides cristatus and Arenigobius bifrenatus). Analyses of the forces of lift and weight of the head and body during ASR indicate a hydrostatic role for the bubble. During ASR, lift from the bubble was sufficient to provide neutral or positive buoyancy to the head, anchoring the mouth at the water surface. A buoyancy role was confirmed by experiments demonstrating the ability of some species to alter bubble volume, to compensate either for different body positions or for water densities (salinities). Use of the bubble for aerial respiration by Cryptocentroides, Mugilogobius, Chlamydogobius and Arenigobius was confirmed in hypoxia by the presence of blood-filled capillaries in the buccal subepithelium (mean air-blood barrier less than 30 μm) in areas of the buccal cavity that contacted the bubble. Blood-filled capillaries were rare or absent in normoxia in all species except Mugilogobius. Cutaneous respiration was inferred from the presence of blood-filled capillaries in the dermis and epidermis of emersed portions of the head in Mugilogobius, Chlamydogobius and Arenigobius. The buccal bubble has respiratory and hydrostatic roles and there is support for the hypothesis that ASR and the buoyancy regulation (air-gulping) required to perform it effectively are prerequisite steps in the evolution of air-breathing in these gobies.
Bacillus Thuringiensis δ-Endotoxin And Larval Manduca Sexta Midgut Brush-Border Membrane Vesicles Act Synergistically To Cause Very Large Increases In The Conductance Of Planar Lipid Bilayers
Authors: Martin Francis G. , Wolfersberger Michael G.
Published: April 2021

Brush-border membrane vesicles prepared from midguts of Manduca sexta larvae were incorporated into planar phospholipid bilayers. Addition of Bacillus thuringiensis δ-endotoxin to the buffered salt solutions bathing these bilayers resulted in large irreversible increases in conductance. At pH 9.6, the smallest toxin-dependent increase in bilayer conductance observed was 13 nS. Similar conductance increases were never observed in the absence of δ-endotoxin or in δ-endotoxin-treated bilayers not containing components of insect brush-border membranes.
Magnetic Orientation of Spiny Lobsters in the Ocean: Experiments with Undersea Coil Systems
Authors: Lohmann Kenneth J. , Pentcheff N. Dean , Nevitt Gabrielle A. , Stetten George D. , Zimmer-Faust Richard K. , Jarrard Hugh E. , Boles Larry C.
Published: April 2021

The western Atlantic spiny lobster Panulirus argus undergoes an annual migration and is also capable of homing to specific dens in its coral reef environment. Relatively little is known, however, about the orientation cues that lobsters use to guide their movements. To determine whether lobsters can orient to the earth’s magnetic field, divers monitored the orientation of lobsters tethered inside magnetic coil systems submerged offshore in the Florida Keys, USA. Each coil could be used to reverse either the horizontal or vertical component of the earth’s field.

Tethered lobsters walking inside the coils often established and maintained consistent courses towards specific directions. After a lobster had established a course, it was exposed to one of three conditions: (1) a reversal of the horizontal component of the earth’s field; (2) a reversal of the vertical component of the earth’s field; or (3) no change in the ambient field (controls). Lobsters subjected to the horizontal field reversal deviated significantly from their initial courses. In contrast, control lobsters and those subjected to the reversed vertical field did not.

These results demonstrate that spiny lobsters possess a magnetic compass sense. Because inverting the vertical component of the earth’s field had no effect on orientation, the results suggest that the lobster compass is based on field polarity and thus differs from the inclination compasses of birds and sea turtles. The magnetic compass of lobsters may function in homing behavior, in guiding the autumn migration or in both.
Recovery of Function, Peripheral Sensitization and Sensory Neurone Activation by Novel Pathways Following Axonal Injury in Aplysia Californica
Authors: Dulin Michael F. , Steffensen Isabella , Morris Catherine E. , Walters Edgar T.
Published: April 2021

Recovery of behavioural and sensory function was examined following unilateral pedal nerve crush in Aplysia californica. Nerve crush that transected all axons connecting the tail to the central nervous system (CNS) eliminated the ipsilateral tail-evoked siphon reflex, whose sensory input travels in the crushed tail nerve (p9). The first reliable signs of recovery of this reflex were observed within 1 week, and most animals displayed tail-evoked siphon responses within 2 weeks. Wide-dynamic-range mechanosensory neurones with somata in the ventrocaudal (VC) cluster of the ipsilateral pleural ganglion exhibited a few receptive fields (RFs) on the tail 3 weeks after unilateral pedal nerve crush, indicating that the RFs had either regenerated or been reconnected to the central somata. These RFs were smaller and sensitized compared with corresponding RFs on the contralateral, uncrushed side. Centrally conducted axon responses of VC sensory neurones to electrical stimulation distal to the nerve crush site did not reappear until at least 10 days after the crush. Because the crush site was much closer to the CNS than to the tail, the failure of axon responses to be restored earlier than the behavioural responses indicates that early stages of reflex recovery are not due to regeneration of VC sensory neurone axons into the tail. Following nerve crush, VC sensory neurones often could be activated by stimulating central connectives or peripheral nerves that do not normally contain the sensory neurone’s axons. These results suggest that recovery of behavioural function after nerve injury involves complex mechanisms, including regenerative growth of axotomized VC sensory neurones, sensitization of regenerating RFs and sprouting of VC sensory neurone fibres within the CNS. Furthermore, the rapidity of behavioural recovery indicates that its initial phases are mediated by additional mechanisms, perhaps centripetal regeneration of unidentified sensory neurones having peripheral somata, or transient reconnection of proximal and distal stumps of axotomized VC cells.
Adenylate Compartmentation and Storage in Coelomic Cells of the Polychaete Nereis Virens
Authors: Hoeger U. , Dunn J. F. , Märker C.
Published: April 2021

The concentrations of adenine nucleotides (AMP, ADP, ATP) were determined in coelomic cells (eleocytes) of the polychaete Nereis virens. In cells of immature and male animals, total ADP and AMP contents (each 10–15 μmol ml−1 packed cell volume) greatly exceeded that of ATP (0.8 μmol ml−1 packed cell volume). 31P-nuclear magnetic resonance (NMR) studies of living eleocytes showed that the high concentrations of both AMP and ADP are free in solution. Comparisons of in vivo NMR spectra with those obtained from metabolite extracts of eleocytes suggest that the adenylate pools are compartmentalized, with a large pool being in an environment with a pH<6.0 and a small pool being in a domain where pH>6.7. This indicates that eleocytes are capable of storing high concentrations of ADP and AMP without inhibiting energy metabolism by sequestering these compounds into an acidic compartment. The large acidic vacuole characteristic of eleocytes may function as this compartment.
Large-Scale Changes in Thermal Sensitivity of Flight Performance During Adult Maturation in a Dragonfly
Authors: Marden James H.
Published: April 2021

Newly emerged adult dragonflies are physiologically immature in a number of ways, including the mass, ultrastructure and biochemistry of their flight muscles. In Libellula pulchella dragonflies, adult maturation of flight muscle is accompanied by striking changes in thermal physiology. Vertical force production during fixed flight attempts in newly emerged adults (tenerals) shows a broad plateau of near-peak performance, first attained at cool thoracic temperatures (typically 28–34 °C) and maintained up to thoracic temperatures of 40–45 °C [mean optimal thoracic temperature (OTT)=34.6 °C; mean upper lethal temperature (ULT)=45.3 °C]. In contrast, fully mature adults show narrow thermal sensitivity curves, wherein peak performance is approached only within a few degrees of the thermal optimum, which invariably occurs at hot thoracic temperatures (38–50 °C; mean OTT=43.5 °C; mean ULT=48.6 °C). These changes in the shape and position of thermal performance curves are compared with predictions from hypotheses for the evolution of thermal sensitivity.
Energetic Consequences of Flight Speeds of Foraging Red and Hoary Bats (Lasiurus Borealis and Lasiurus Cinereus; Chiroptera: Vespertilionidae)
Authors: Cueva Salcedo Horacio De La , Fenton M. Brock , Hickey M. Brian C. , Blake Robert W.
Published: April 2021

We used Doppler radar readings of the flight speeds of foraging, lactating female Lasiurus borealis (N=826) and Lasiurus cinereus (N=544) to test morphologically based predictions about their flight performance. Both species flew at speeds (V=6.7 and 7.7 m s−1, respectively) that differed significantly from predicted minimum power speed (Vmp ; 4.0 and 5.08 m s−1, respectively) or predicted maximum range speed (Vmr ; 5.25 and 6.69 m s−1, respectively), perhaps reflecting the active pursuit of moths performing evasive manoeuvres. Estimates of costs of flight and lactation are combined with data on prey size together with encounter and capture rates to illustrate the energetic benefits accruing to these species when they forage in concentrations of insects.
Sensitivity of the Mystacial Vibrissae of Harbour Seals (Phoca Vitulina) For Size Differences of Actively Touched Objects
Authors: Dehnhardt G. , Kaminski A.
Published: April 2021

We studied the capability of one male and one female harbour seal Phoca vitulina to discriminate diameter differences of circular discs by means of active touch with their mystacial vibrissae. To prevent the animals from perceiving visual information, they were blindfolded during trials. In a two-alternative forced-choice procedure, the seals were required to choose the larger of two Perspex discs. Weber fractions c (the ratio of the lowest diameter difference detected by the seals on 75 % of occasions to the starting disc diameter D, ΔD/D=c) were determined for three standard discs (diameters 1.12 cm, 5.04 cm and 8.74 cm) by the psychophysical method of limits. While the seals achieved Weber fractions of 0.29 (male) and 0.26 (female) at the smallest standard disc, their performance improved with increasing disc size, resulting in an approximately constant Weber fraction of 0.13 (male) and 0.08 (female) for the two larger standard discs. The difference in performance between the two seals did not reflect a real difference in sensitivity, but may best be explained by a difference in choice behaviour. As a measure of tactile acuity, the Weber fractions obtained for the larger standard discs indicate that harbour seals can use their mystacial vibrissae as efficiently for active touch as monkeys use their hands.
Simultaneous Control of Head and Thoracic Temperature by the Green Darner Dragonfly Anax Junius (Odonata: Aeshnidae)
Authors: May Michael L.
Published: April 2021

Anax junius is a large dragonfly that regulates thoracic temperature (Tth) during flight. This species, like several other intermittently endothermic insects, achieves control of Tth at least in part by increasing circulation of hemolymph to the abdomen at high air temperature (Ta), thus facilitating heat loss from the thorax. In this paper, I demonstrate that heat transfer to the head is also under active control, very probably owing to temperature-sensitive alteration of hemolymph circulation. As a result, head temperature (Th) is strikingly elevated above Ta during endothermic warm-up and flight. Furthermore, during unrestrained flight in the field, Th is regulated actively by increasing hemolymph circulation from the warm thorax at low Ta. Concurrent measurements of abdominal temperature (Tab) confirm that the abdomen is used as a ‘thermal window’ at Ta>30 ˚C but apparently not at lower Ta; thus, some additional mechanism(s) must exist for regulation of Tth at low Ta.
Haemoglobin function in intact lamprey erythrocytes: interactions with membrane function in the regulation of gas transport and acid–base balance
Authors: Nikinmaa Mikko , Airaksinen Susanna , Virkki Leila V.
Published: April 2021

Haemoglobin function within lamprey erythrocytes offers a unique solution to gas transport among vertebrates. Lamprey haemoglobin within intact erythrocytes is in oligomer/monomer equilibrium and has an oxygen affinity similar to that of haemoglobin in other active fishes. The cooperativity of oxygen binding, which is reduced at low pH values, the effect of protons and the effect of the concentration of haemoglobin on its oxygen affinity are all due to dissociation/association reactions of the haemoglobin molecules. The permeability of the lamprey red cell membrane to acid and base equivalents is very low, and plasma bicarbonate cannot therefore be dehydrated to carbon dioxide to any significant extent during the residence time of blood in the gills. This potential limitation on carbon dioxide excretion is overcome, however, by the high intraerythrocytic pH and the marked oxygenation-linked pH changes in the erythrocyte, which are due to the large Haldane effect of the haemoglobin. Owing to the relative impermeability of the erythrocyte membrane to acid equivalents, intraerythrocytic haemoglobin cannot take part in the acid–base buffering of the extracellular compartment. As a consequence, extracellular acid loads cause marked fluctuations in plasma pH.