bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Channel Activity From The Midgut Brush-Border Membrane Of Gypsy Moth (Lymantria Dispar) Larvae
Authors: Peyronnet Olivier , Vachon Vincent , Schwartz Jean-Louis , Laprade Raynald
Published: April 2021

Ion channels from the midgut apical membrane of gypsy moth (Lymantria dispar) larvae were studied following mechanical fusion of brush-border membrane vesicles with planar phospholipid bilayer membranes. In symmetrical 300 mmol l−1 KCl (pH 9.0), nine different channels with conductances ranging from 27 to 795 pS and linear current/voltage relationships were resolved. In the presence of a KCl gradient across the bilayer (450 mmol l−1cis/150 mmol l−1trans), 11 different conductance levels ranging from 16 to 850 pS were detected. The channels were slightly cationic: the zero-current reversal potential was shifted by −5 mV to −21 mV compared with symmetrical KCl conditions, corresponding to pK/pCl permeability ratios of 1.5–8.0. Most channels were neither voltage-dependent nor Ca2+-sensitive and displayed complex gating kinetics. Addition of Ba2+ or Cs+ to both sides of the bilayer had little effect on channel activity, but fewer distinct channels were observed when KCl was replaced by potassium gluconate, suggesting an effect of Cl− on channel activity. A reduced number of channels was also detected when KCl was replaced by N-methyl-D-glucamine-HCl. Under asymmetrical N-methyl-D-glucamine-HCl conditions, only anionic channels were observed. They exhibited current rectification (35 pS at negative voltages and 81 pS at positive voltages) and were strongly voltage-dependent.
Adhesion Measured on the Attachment Pads of Tettigonia Viridissima (Orthoptera, Insecta)
Authors: Jiao Yuekan , Gorb Stanislav , Scherge Matthias
Published: April 2021

The tarsi of the cricket Tettigonia viridissima bear flexible attachment pads that are able to deform, replicating the profile of a surface to which they are apposed. This attachment system is supplemented by a secretion produced by epidermal cells and transported onto the surface of the pad through the pore canals of the pad cuticle. This study shows that the secretion alone is necessary, but not sufficient, for adhesion. To account for the full adhesive force, the deformation of the pad and the resulting changes in contact area were considered. In two series of experiments, the adhesive properties of the secretion and the adhesion of the whole pad were measured using a force tester, the sensitivity of which ranged from micronewtons to centinewtons.

The adhesive forces of the secretion measured between a smooth sapphire ball with a diameter of 1.47 mm and a flat silicon surface ranged from 0.1 to 0.6 mN. In a control experiment on the silicon surface without secretion, no adhesive force was measured. There was no dependence of the adhesive force on the applied compressive force.

When an intact pad was pulled off a flat silicon surface, the adhesive force increased with increasing applied compressive force, but it did not increase further once the applied force exceeded a certain value. The saturated adhesive force, ranging from 0.7 to 1.2 mN, was obtained at applied forces of 0.7–1.5 mN. The hemispherical surface of the pad had a larger contact area and demonstrated greater adhesion under a larger applied force. Adhesion became saturated when a pad was deformed such that contact area was maximal. The tenacity (the adhesive force per unit area) was 1.7–2.2 mN mm−2.
Control Of Epithelial Cl− Secretion By Basolateral Osmolality In The Euryhaline Teleost Fundulus Heteroclitus
Authors: Marshall W. S. , Bryson S. E. , Luby T.
Published: April 2021

Euryhaline teleost fish adapt rapidly to salinity change and reduce their rate of ion secretion on entry to fresh water. Killifish (Fundulus heteroclitus) transferred from full-strength sea water to fresh water showed large reductions in plasma [Na+] and osmolality at 6 h which were corrected by 24 h. To mimic this in vitro, a hypotonic shock of 20–70 mosmol kg−1 was applied on the basolateral side of opercular epithelia. This hypotonic shock reversibly reduced the short-circuit current (Isc, equivalent to the rate of secretion of Cl−) in a dose-dependent fashion, with a 40 mosmol kg−1 hypotonic shock reducing Isc by 58±4.6 % in 40 min. Similar reductions in [NaCl], but with added mannitol to maintain osmolality, were without effect, indicating that the effect was purely osmotic. Hypotonic inhibition of Isc was accompanied by reductions in epithelial conductance (Gt) but no significant change in transepithelial potential (Vt). The hypotonic inhibition was apparently not Ca2+-mediated because Ca2+-depleted salines, thapsigargin and ionomycin all failed to block the reduction in Isc produced by hypotonic shock. The inhibition was not mediated via a reduction in intracellular cyclic AMP level because cyclic AMP levels, measured by radioimmunoassay, were unchanged by hypotonic shock and by 1.0 μmol l−1 clonidine (which inhibits Isc by changing intracellular [Ca2+]) but were increased markedly by 1.0 μmol l−1 isoproterenol, a positive control. The protein tyrosine kinase inhibitor genistein (100 μmol l−1), but not its inactive analogue daidzein, inhibited Isc in normal osmolality but produced a stimulation of Isc after hypotonic shock (and after clonidine treatment). The inhibitory effects of genistein and hypotonicity were not additive, suggesting that the same portion of the Isc was inhibited by both treatments. These data are consistent with a model for Cl− transport regulation involving tyrosine phosphorylation in cell-swelling-induced inhibition of Cl− secretion when euryhaline teleosts adapt to fresh water.
Associative olfactory learning in the moth Manduca sexta
Authors: Daly K.C. , Smith B.H.
Published: April 2021

The proboscis extension response conditioning protocol has been used to explore olfactory-based associative learning in an array of insects. We have monitored a different feeding reflex, which involves activation of the cibarial pump, to demonstrate olfactory learning in the moth Manduca sexta. In the first experiment, four different treatment conditions were used to assess associative (Pavlovian) learning. The results indicate that an excitatory cibarial pump response develops and is retained for at least 24 h only when odor is forward-paired with the presentation of sucrose. Three control treatments, backward pairing, air (no odor) pairing and random pairing, failed to increase the cibarial pump response. However, an excitatory cibarial pump response developed when the backward- and air-paired groups received forward pairing of odor and sucrose on the following day. In contrast, moths experiencing random pairing on day 1 displayed a slower rate of acquisition during forward pairing on day 2, which may indicate inhibition. The second experiment investigated discrimination learning. Two odors were randomly presented, one odor being forward-paired with sucrose (+), the other presented alone (−) in a counterbalanced design. Again, only when odor was forward-paired with sucrose did learning occur. We discuss the implication of these findings for a broader comparative analysis of learning in insects.
Chloride Conductance Across Toad Skin: Effects of Ionic Acclimations and Cyclic Amp and Relationship to Mitochondria-Rich Cell Density
Authors: Rozman A. , Gabbay S. , Katz U.
Published: April 2021

The anionic conductance across toad (Bufo viridis) skin was studied using the voltage-clamp technique following long-term (more than 10 days) acclimation to NaCl and KCl solutions. The non-specific baseline conductance was approximately 0.6 mS cm−2 and was similar in skins from all acclimation conditions. The voltage-activated Cl− conductance (GCl) was maximal in skins from distilled-water- and KCl-acclimated toads (>3 mS cm−2) and was greatly reduced following acclimation to NaCl solutions. Cyclic AMP (EC50=13 μmol l−1) and isobutylmethyl xanthine (IBMX) (EC50=69 μmol l−1) exerted different effects on the activated conductance. IBMX only sensitized the activated conductance, whereas cyclic AMP (CPTcAMP) at high concentrations induced an increase in anionic conductance that was insensitive to electrical potential. Furthermore, external Cl− was not required for the stimulatory effect of cyclic AMP, and the conductive pathway had low selectivity. The effects of the two agonists were reversible and depended on the acclimation conditions. Following electrical measurements, the skin of the toads was removed and stained with silver to measure mitochondria-rich cell density (Dmrc). There was no correlation between Dmrc and Cl− conductance in the present study.
Selective Heating of Vibrissal Follicles In Seals (Phoca Vitulina) and Dolphins (Sotalia Fluviatilis Guianensis)
Authors: Mauck Björn , Eysel Ulf , Dehnhardt Guido
Published: April 2021

The thermal characteristics of the mystacial vibrissae of harbour seals (Phoca vitulina) and of the follicle crypts on the rostrum of the dolphin Sotalia fluviatilis guianensis were measured using an infrared imaging system. Thermograms demonstrate that, in both species, single vibrissal follicles are clearly defined units of high thermal radiation, indicating a separate blood supply to these cutaneous structures. It is suggested that the high surface temperatures measured in the area of the mouth of the follicles is a function of the sinus system. In seals and dolphins, surface temperature gradually decreased with increasing distance from the centre of a follicle, indicating heat conduction from the sinus system via the follicle capsule to adjacent tissues. It is suggested that the follicular sinus system is a thermoregulatory structure responsible for the maintenance of high tactile sensitivity at the extremely low ambient temperatures demonstrated for the vibrissal system of seals. The vibrissal follicles of odontocetes have been described as vestigial structures, but the thermograms obtained in the present study provide the first evidence that, in Sotalia fluviatilis, the follicles possess a well-developed sinus system, suggesting that they are part of a functional mechanosensory system.
Size Matters: Ontogenetic Variation in the Three-Dimensional Kinematics of Steady-Speed Locomotion in the Lizard Dipsosaurus Dorsalis
Authors: Irschick Duncan J. , Jayne Bruce C.
Published: April 2021

Although many studies have investigated how locomotor capacities change with size, few studies have examined whether different-sized individuals within a species have similar kinematics during locomotion. We quantified the skeletal limb morphology and the three-dimensional kinematics of the hindlimb of four sizes (4–66 g) of the lizard Dipsosaurus dorsalis moving steadily at both the walk–run transition (50 % duty factor) and at a moderately fast speed of 250 cm s−1. We used analyses of variance to test whether limb movements changed with size and to determine whether size and speed had interactive effects on kinematics. The disproportionately long hindlimbs of smaller lizards partly contributed to their relatively greater (i.e. adjusted by snout–vent length) values of linear kinematic variables. Both relative linear and angular kinematics changed significantly with both size and speed, both of which had widespread interactive effects. By having more extension of the knee and ankle joints, and thus a relatively higher hip height during stance, the slow-speed movements of small lizards displayed some of the characteristics of the fast-speed movements in larger lizards. Further, approximately one-fifth and two-fifths of the strides of the two smallest size classes were digitigrade at the lower and higher speeds, respectively, whereas the two largest size classes always had a plantigrade foot posture. Some of the most striking effects of size on kinematics were most evident at the lower of the two speeds. Unlike interspecific studies, which show that the limbs often become more crouched with decreased size, the more extended limbs of smaller lizards in this study suggest that variation in size alone cannot be the causal reason for differences in limb posture.
Terrestrial Locomotion in the Black-Billed Magpie: Kinematic Analysis of Walking, Running and Out-of-Phase Hopping
Authors: Verstappen Myriam , Aerts Peter , Damme Raoul Van
Published: April 2021

The inter-limb kinematic patterns of walking, running and out-of-phase hopping in black-billed magpies (Pica pica) were studied using high-speed video recordings. The flexion/extension patterns of the joints were similar between the gait types, suggesting that the within-leg control of the angular excursions is similar. This result is further supported by the fact that running and hopping are alternative gaits at speeds higher than walking; however, magpies show a preference for hopping. Moreover, only small differences occur between the kinematic patterns of the two limbs during out-of-phase hopping, during which the legs are believed to have different functions. The hindlimb kinematic patterns of magpies are like those of other flying and more terrestrial bird species; however, striking differences are found in comparison with humans at the level of the internal angles. This is probably due to the differences in the morphology and configuration of their legs.
Preferred Speed and Cost of Transport: The Effect of Incline
Authors: Wickler Steven J. , Hoyt Donald F. , Cogger Edward A. , Hirschbein Misty H.
Published: April 2021

Preferred speed is the behavioral tendency of animals to utilize a relatively narrow set of speeds near the middle of a much broader range that they are capable of using within a particular gait. Possible explanations for this behavior include minimizing musculoskeletal stresses and maximizing energetic economy. If preferred speed is determined by energetic economy (cost of transport, CT), then shifts in preferred speed should produce shifts in CT. To test this hypothesis, preferred speeds were measured in trotting horses on the level and on an incline. The preferred trotting speed decreased from 3.29±0.24 m s−1 on the level to 3.05±0.30 m s−1 (means ± S.D., N=6) on an 11.8 % incline. The rate of oxygen consumption was measured as a function of trotting speed on a treadmill and was a curvilinear function of speed in all horses under both conditions (level and 10 % incline). This curvilinear relationship resulted in a CT that was a U-shaped function of speed. The speed at which CT was minimal (i.e. at which trotting was most energetically economical) was very near the preferred speed on the level and decreased on the incline, again to a speed near the preferred speed on the incline.
Hair Cells, Hearing and Hopping: A Field Guide to Hair Cell Physiology in the Frog
Authors: Smotherman Michael S. , Narins Peter M.
Published: April 2021

For more than four decades, hearing in frogs has been an important source of information for those interested in auditory neuroscience, neuroethology and the evolution of hearing. Individual features of the frog auditory system can be found represented in one or many of the other vertebrate classes, but collectively the frog inner ear represents a cornucopia of evolutionary experiments in acoustic signal processing. The mechano-sensitive hair cell, as the focal point of transduction, figures critically in the encoding of acoustic information in the afferent auditory nerve. In this review, we provide a short description of how auditory signals are encoded by the specialized anatomy and physiology of the frog inner ear and examine the role of hair cell physiology and its influence on the encoding of sound in the frog auditory nerve. We hope to demonstrate that acoustic signal processing in frogs may offer insights into the evolution and biology of hearing not only in amphibians but also in reptiles, birds and mammals, including man.
Three-Dimensional Kinematics and Wake Structure of the Pectoral Fins During Locomotion in Leopard Sharks Triakis Semifasciata
Authors: Wilga C. D. , Lauder G. V.
Published: April 2021

The classical theory of locomotion in sharks proposes that shark pectoral fins are oriented to generate lift forces that balance the moment produced by the oscillating heterocercal tail. Accordingly, previous studies of shark locomotion have used fixed-wing aircraft as a model assuming that sharks have similar stability and control mechanisms. However, unlike airplanes, sharks are propelled by undulations of the body and tail and have considerable control of pectoral fin motion. In this paper, we use a new approach to examine the function of the pectoral fins of leopard sharks, Triakis semifasciata, during steady horizontal swimming at speeds of 0.5–2.0 l s−1, where l is total body length, and during vertical maneuvering (rising and sinking) in the water column. The planar orientation of the pectoral fin was measured using three-dimensional kinematics, while fluid flow in the wake of the pectoral fin and forces exerted on the water by the fin were quantified using digital particle image velocimetry (DPIV). Steady horizontal swimming in leopard sharks is characterized by continuous undulations of the body with a positive body tilt to the flow that decreases from a mean of 11 ° to 0.6 ° with increasing flow speeds from 0.5 to 2.0 l s−1. Three-dimensional analysis showed that, during steady horizontal locomotion, the pectoral fins are cambered, concave downwards, at a negative angle of attack that we predict to generate no significant lift.

Leopard shark pectoral fins are also oriented at a substantial negative dihedral angle that amplifies roll moments and hence promotes rapid changes in body position. Vortices shed from the trailing edge of the pectoral fin were detected only during vertical maneuvering. Starting vortices are produced when the posterior plane of the pectoral fin is actively flipped upwards or downwards to initiate rising or sinking, respectively, in the water column. The starting vortex produced by the pectoral fin induces a pitching moment that reorients the body relative to the flow. Body and pectoral fin surface angle are altered significantly when leopard sharks change vertical position in the water column. Thus, locomotion in leopard sharks is not analogous to flight in fixed-wing aircraft. Instead, a new force balance for swimming leopard sharks is proposed for steady swimming and maneuvering. Total force balance on the body is adjusted by altering the body angle during steady swimming as well as during vertical maneuvering, while the pectoral fins appear to be critical for initiating maneuvering behaviors, but not for lift production during steady horizontal locomotion.
Seasonal Changes in Buoyancy and Diving Behaviour of Adult Grey Seals
Authors: Beck Carrie A. , Bowen W. Don , Iverson Sara J.
Published: April 2021

Phocid seals go through dramatic seasonal changes in body mass and composition as a result of the spatial and temporal separation of foraging, reproduction and moulting. These changes in body fat content and body mass result in seasonal changes in buoyancy, which in turn may influence diving behaviour. We examined the longitudinal changes in buoyancy and diving behaviour of 14 adult grey seals (Halichoerus grypus) during two periods that represent maximal contrast in body mass and composition. During both the post-moulting (PM) and pre-breeding (PB) periods, grey seals were negatively buoyant. However, buoyancy increased by 47.9 % between the PM and PB periods. Descent rate was significantly faster during the PM period (1.0±0.07 m s−1) than during the PB period (0.7±0.06 m s−1), suggesting that seals were aided by negative buoyancy during the downward portion of dives.

Ascent rate was also significantly faster during the PM period (0.8±0.06 m s−1) than during the PB period (0.6±0.05 m s−1), contradicting the prediction that more buoyant animals should ascend faster. The effects of drag could not account for this discrepancy. Dive depth and surface interval between dives did not differ significantly between the two periods. Similarly, the distribution of dive shapes used by individuals did not differ between the two periods. However, dive duration was significantly longer during the PB period than during the PM period (5.5±0.25 min compared with 4.4±0.24 min, respectively) as was time spent at the bottom of the dive (3.1±0.22 min compared with 2.5±0.15 min, respectively).
Partial Experience with the Arc of the Sun is Sufficient for all-Day Sun Compass Orientation in Homing Pigeons, Columba Livia
Authors: Budzynski Cheri A. , Dyer Fred C. , Bingman Verner P.
Published: April 2021

The ability of animals to learn to use the sun for orientation has been explored in numerous species. In birds, there is conflicting evidence about the experience needed for sun compass orientation to develop. The prevailing hypothesis is that birds need entire daytime exposure to the arc of the sun to use the sun as an orientation cue. However, there is also some evidence indicating that, even with limited exposure to the arc of the sun, birds, like insects, can use the sun to orient at any time of day. We re-examine this issue in a study of compass orientation in a cue-controlled arena. Two groups of young homing pigeons received different exposure to the sun. The control group experienced the sun throughout the day; the experimental group experienced only the apparent descent of the sun. After 8 weeks of sun exposure, we trained both groups in the afternoon to find food in a specific compass direction in an outdoor arena that provided a view of the sun but not landmarks. We then tested the pigeons in the morning for their ability to use the morning sun as an orientation cue. The control group and the experimental group, which was exposed to the morning sun for the first time, succeeded in orienting in the training direction during test 1. The orientation of the experimental group was no different from that of the control group, although the experimental first trial directional response latencies were greater than the control latencies. Subsequently, we continued training both groups in the afternoon and then tested the pigeons during the morning under complete cloud cover. Both groups displayed random directional responses under cloud cover, indicating that the observed orientation was based on the visibility of the sun. The data indicate that pigeons with limited exposure to the arc of the sun can, like insects, use the sun for orientation at any time of day.
Exploring Dynamic Similarity in Human Running Using Simulated Reduced Gravity
Authors: Donelan J. Maxwell , Kram Rodger
Published: April 2021

The Froude number (a ratio of inertial to gravitational forces) predicts the occurrence of dynamic similarity in legged animals over a wide range of sizes and velocities for both walking and running gaits at Earth gravity. This is puzzling because the Froude number ignores elastic forces that are crucial for understanding running gaits. We used simulated reduced gravity as a tool for exploring dynamic similarity in human running. We simulated reduced gravity by applying a nearly constant upward force to the torsos of our subjects while they ran on a treadmill. We found that at equal Froude numbers, achieved through different combinations of velocity and levels of gravity, our subjects did not run in a dynamically similar manner. Thus, the inertial and gravitational forces that comprise the Froude number were not sufficient to characterize running in reduced gravity. Further, two dimensionless numbers that incorporate elastic forces, the Groucho number and the vertical Strouhal number, also failed to predict dynamic similarity in reduced-gravity running. To better understand the separate effects of velocity and gravity, we also studied running mechanics at fixed absolute velocities under different levels of gravity. The effects of velocity and gravity on the requirements of dynamic similarity differed in both magnitude and direction, indicating that there are no two velocity and gravity combinations at which humans will prefer to run in a dynamically similar manner. A comparison of walking and running results demonstrated that reduced gravity had different effects on the mechanics of each gait. This suggests that a single unifying hypothesis for the effects of size, velocity and gravity on both walking and running gaits will not be successful.
Wolbachia Infection and Cytoplasmic Incompatibility in the Cricket Teleogryllus Taiwanemma
Authors: Kamoda Satoru , Masui Shinji , Ishikawa Hajime , Sasaki Tetsuhiko
Published: April 2021

Wolbachia are cytoplasmically inherited bacteria found in many arthropods. They induce various reproductive alterations in their hosts, including cytoplasmic incompatibility, thelytokous parthenogenesis, feminization and male-killing. In this study, we examined Wolbachia infection and its effects on the host cricket Teleogryllus taiwanemma. In a phylogenetic study based on the wsp gene coding for a Wolbachia surface protein, the Wolbachia strain harboured by T. taiwanemma was clustered together with those harboured by Laodelphax striatellus, Tribolium confusum, Acraea encedon, Trichogramma deion and Adalia bipunctata. Crossing experiments using the Wolbachia-infected and uninfected strains of cricket showed that the infection is associated with the expression of unidirectional cytoplasmic incompatibility: the egg hatch rate in the incompatible cross between the infected males and uninfected females was 20.3 %. We also examined the distribution of Wolbachia within the host using polymerase chain reaction assays; they were detected in the antennae, heads, forewings, hindwings, testes, ovaries, Malpighian tubules, foot muscles and fat bodies. Quantitative polymerase chain reaction assays showed that the bacterial density was highest in the fat bodies, followed by the ovaries and testes. Wolbachia were not detected in the haemolymph or in mature spermatozoa. The spermatozoa of the infected male may be modified by the presence of Wolbachia during its development. To examine this possibility, we compared the profiles of sperm proteins between the infected and uninfected males using two-dimensional gel electrophoresis. However, no differences in the protein profiles were observed.
Estimation of Thermal Constants: The Importance of using Equilibrium Temperature Rather than Ambient Temperature Demonstrated with Hoverflies (Diptera, Syrphidae, Genus Eristalis)
Authors: Bressin S. , Willmer P. G.
Published: April 2021

Water evaporation has a marked effect on the passive rates of body temperature change of eristaline hoverflies. It results in the equilibrium temperature of these flies being significantly lower than ambient temperature. Different values for the cooling and warming constants are therefore obtained depending on whether equilibrium or ambient temperature is used as the baseline. Hence, care must be taken when estimating these constants with all animals, especially those of moderate to high permeability. It is recommended that equilibrium temperature be used in such situations. Evaporative cooling is probably also responsible for cooling constants being higher than warming constants in this and other studies.
Locomotor Repertoire of The Larval Zebrafish: Swimming, Turning and Prey Capture
Authors: Budick Seth A. , O’Malley Donald M.
Published: April 2021

Larval zebrafish (Brachydanio rerio) are a popular model system because of their genetic attributes, transparency and relative simplicity. They have approximately 200 neurons that project from the brainstem into the spinal cord. Many of these neurons can be individually identified and laser-ablated in intact larvae. This should facilitate cellular-level characterization of the descending control of larval behavior patterns. Towards this end, we attempt to describe the range of locomotor behavior patterns exhibited by zebrafish larvae. Using high-speed digital imaging, a variety of swimming and turning behaviors were analyzed in 6-to 9-day-old larval fish. Swimming episodes appeared to fall into two categories, with the point of maximal bending of the larva’s body occurring either near the mid-body (burst swims) or closer to the tail (slow swims). Burst swims also involved larger-amplitude bending, faster speeds and greater yaw than slow swims. Turning behaviors clearly fell into two distinct categories: fast, large-angle escape turns characteristic of escape responses, and much slower routine turns lacking the large counterbend that often accompanies escape turns. Prey-capture behaviors were also recorded. They were made up of simpler locomotor components that appeared to be similar to routine turns and slow swims. The different behaviors observed were analyzed with regard to possible underlying neural control systems. Our analysis suggests the existence of discrete sets of controlling neurons and helps to explain the need for the roughly 200 spinal-projecting nerve cells in the brainstem of the larval zebrafish.
Olfactory Learning in the Cricket Gryllus Bimaculatus
Authors: Matsumoto Yukihisa , Mizunami Makoto
Published: April 2021

The olfactory learning capability of the cricket Gryllus bimaculatus was studied. Crickets were deprived of drinking water for 4 days and were individually trained to associate peppermint with water and vanilla with NaCl solution. Their odour preference was tested before and after training by allowing them to choose between peppermint or vanilla sources. The time spent visiting each source served as a measure of odour preference. Crickets exhibited an initial preference for vanilla over peppermint, but preference for the latter increased after only one training session. The olfactory memory formed by a single training session decayed with time but remained for at least 24 h. Memory formed by three training sessions was extremely robust, and did not decay significantly between 1 and 7 days after training. The preference formed was easily altered by reversal training in which vanilla was associated with water and peppermint with saline solution. This study shows that crickets have a highly developed olfactory learning capability characterized by fast acquisition, long retention and easy rewriting of memory.
Acoustic Identification of Twelve Species of Echolocating Bat By Discriminant Function Analysis and Artificial Neural Networks
Authors: Parsons Stuart , Jones Gareth
Published: April 2021

We recorded echolocation calls from 14 sympatric species of bat in Britain. Once digitised, one temporal and four spectral features were measured from each call. The frequency–time course of each call was approximated by fitting eight mathematical functions, and the goodness of fit, represented by the mean-squared error, was calculated. Measurements were taken using an automated process that extracted a single call from background noise and measured all variables without intervention. Two species of Rhinolophus were easily identified from call duration and spectral measurements. For the remaining 12 species, discriminant function analysis and multilayer back-propagation perceptrons were used to classify calls to species level. Analyses were carried out with and without the inclusion of curve-fitting data to evaluate its usefulness in distinguishing among species. Discriminant function analysis achieved an overall correct classification rate of 79 % with curve-fitting data included, while an artificial neural network achieved 87 %. The removal of curve-fitting data improved the performance of the discriminant function analysis by 2 %, while the performance of a perceptron decreased by 2 %. However, an increase in correct identification rates when curve-fitting information was included was not found for all species. The use of a hierarchical classification system, whereby calls were first classified to genus level and then to species level, had little effect on correct classification rates by discriminant function analysis but did improve rates achieved by perceptrons. This is the first published study to use artificial neural networks to classify the echolocation calls of bats to species level. Our findings are discussed in terms of recent advances in recording and analysis technologies, and are related to factors causing convergence and divergence of echolocation call design in bats.
Action of Adenosine on Energetics, Protein Synthesis And K+ Homeostasis in Teleost Hepatocytes
Authors: Krumschnabel Gerhard , Biasi Christina , Wieser Wolfgang
Published: April 2021

In a comparative study, we analysed the effects of adenosine on the energetics, protein synthesis and K+ homeostasis of hepatocytes from the anoxia-tolerant goldfish Carassius auratus and the anoxia-intolerant trout Oncorhynchus mykiss. The rate of oxygen consumption did not respond immediately to the addition of adenosine to the cells from either species, but showed a significant decrease in trout hepatocytes after 30 min. The anaerobic rate of lactate formation was not significantly affected by adenosine in goldfish hepatocytes, but was increased in trout cells. We also studied the effects of adenosine on the two most prominent ATP consumers in these cells, protein synthesis and Na+ /K+ -ATPase activity. Under aerobic conditions, adenosine inhibited protein synthesis of hepatocytes from goldfish by 51 % and of hepatocytes from trout by 32 %. During anoxia, the rate of protein synthesis decreased by approximately 50 % in goldfish hepatocytes and by 90 % in trout hepatocytes, and this decrease was not altered by the presence of adenosine. Adenosine inhibited normoxic Na+ /K+ -ATPase activity and K+ efflux by 20–35 % in the cells of both species. An investigation into the mechanism underlying the inhibition of protein synthesis by adenosine indicated that, in the goldfish cells, adenosine acts via a membrane receptor-mediated pathway, i.e. the effect of adenosine was abolished by applying the A1 receptor antagonist 8-phenyltheophylline. In the trout, however, the uptake of adenosine into hepatocytes seems to be required for an effect on protein synthesis. [Ca2+ ]i does not seem to be involved in the inhibition of protein synthesis by adenosine.
Circulatory Impairment Induced by Exercise in the Lizard Iguana Iguana
Authors: Farmer Colleen G. , Hicks James W.
Published: April 2021

Mechanical integration of the cardiac, muscular and ventilatory pumps enables mammals to vary cardiac output over a wide range to match metabolic demands. We have found this integration lacking in a lizard (Iguana iguana) that differs from mammals because blood flow from the caudal body and ventilation are maximal after, rather than during, exercise. Because Iguana iguana are constrained from ventilation during intense locomotion, they appear to be unable to recruit the abdomen and thorax as a pump for venous return. This constraint on simultaneous running and costal breathing arises from their musculoskeletal design, which is similar to that of basal tetrapods, and so a constraint on venous return during exercise may be ancestral for tetrapods. We suggest that mechanical coupling of the pulmonary and cardiac pumps may have been important for the evolution of high-speed locomotor stamina in terrestrial vertebrates.
Temporal and Spatial Expression of the Cell-Cycle Regulator Cul-1 in Drosophila and Its Stimulation by Radiation-Induced Apoptosis
Authors: Filippov Valery , Filippova Maria , Sehnal Frantisek , Gill Sarjeet S.
Published: April 2021

Cul-1 protein is part of the ubiquitin ligase complex that is conserved from yeast to humans. This complex specifically marks cell-cycle regulators for their subsequent destruction. Two null mutations of the cul-1 gene are known, in budding yeast and in nematodes. Although in both these organisms the cul-1 gene executes essentially the same function, the manifestation of its lack-of-function mutations differs considerably. In yeast the mutation causes arrest at the G1/S-phase transition, whereas in nematodes excessive cell divisions occur because mutant cells are unable to exit the mitotic cycle. We isolated cul-1 orthologues from two model organisms, Drosophila melanogaster and mouse. We show that the Drosophila full-length cul-1 gene restores the yeast mutant’s inability to pass through the G1/S-phase transition. We also characterize expression of this gene at the transcript and protein levels during Drosophila development and show that cul-1 gene is maternally supplied as a protein, but not as an RNA transcript. Zygotic transcription of the gene, however, resumes at early stages of embryogenesis. We also found an increase in cul-1 transcription in cultured cells treated with a lethal dose of γ-irradiation.
Temperature-Dependence of L-Type Ca2+ Channel Current in Atrial Myocytes From Rainbow Trout
Authors: Shiels H. A. , Vornanen M. , Farrell A. P.
Published: April 2021

Rainbow trout, Oncorhynchus mykiss, inhabit eurythermal environments and must therefore be able to cope with changes in environmental temperature. As ectotherms, their heart is required to maintain cardiac function over a range of ambient water temperatures. This raises important questions concerning the temperature-dependence of cardiac ion channel function in fish hearts, in particular, the channels involved in Ca2+ transport. Thus, we studied the effects of acute, physiologically relevant temperature changes on the density and kinetics of the L-type Ca2+ channel current (ICa) in rainbow trout atrial myocytes using the whole-cell patch-clamp technique. Myocytes from fish acclimated to 14 °C were first tested at 14 °C, then at 21 °C and finally at 7 °C. Using a square-pulse voltage-clamp in the first series of experiments, the peak density of ICa increased (Q10=1.9) as temperature was increased from 14 to 21 °C and decreased (Q10=2.1) as temperature was decreased from 14 to 7 °C. In contrast to current density, the charge carried by ICa was inversely related to temperature as a result of changes in the kinetic properties of the channel; both the fast (τf) and slow (τs) components of inactivation were slower at 7 °C than at 14 and 21 °C. Action potentials were recorded at the three test temperatures and then used as voltage-clamp stimulus waveforms to reassess ICa in a second series of experiments. While the temperature-dependency of ICa was similar to that found with the square-pulse voltage-clamp, the charge carried by ICa was temperature-independent. These results show that the temperature-dependency of ICa in rainbow trout is in the lower range of that reported in mammals and, although this could have profound effects on Ca2+ delivery to the myofilaments, the temperature-induced modifications in the action potential may help to maintain a fairly constant Ca2+ delivery during an acute temperature change in rainbow trout.
Ultraviolet and Violet Receptors Express Identical mRNA Encoding an Ultraviolet-Absorbing Opsin: Identification and Histological Localization of two Mrnas Encoding Short-Wavelength-Absorbing Opsins in the Retina of the Butterfly Papilio Xuthus
Authors: Kitamoto Junko , Ozaki Koichi , Arikawa Kentaro
Published: April 2021

This paper describes the primary structures of two opsins of short-wavelength-absorbing visual pigments deduced from the mRNA sequences in the retina of the Japanese yellow swallowtail butterfly Papilio xuthus. A phylogenetic analysis of the amino acid sequences indicates that one of these visual pigments is of the ultraviolet-absorbing type and that the other is of the blue-absorbing type. We identified the photoreceptor cells that express these mRNAs by histological in situ hybridization. The mRNA of the ultraviolet type is expressed in two distinct photoreceptor types previously identified as ultraviolet and violet receptors, providing the first molecular biological evidence that different types of spectral receptor probably express a visual pigment with an identical amino acid sequence. The mRNA of the blue type is expressed exclusively in cells classified as blue receptors.
The Adrenergic Volume Changes of Immature and Mature Rainbow Trout (Oncorhynchus Mykiss) Erythrocytes
Authors: Lecklin Tiina , Tuominen Antti , Nikinmaa Mikko
Published: April 2021

In this study, we examined whether the adrenergic volume response of teleost erythrocytes is related to cell maturity. Rainbow trout (Oncorhynchus mykiss) were made anaemic by reducing their haematocrit to approximately 50 % of the original value. After 3–4 weeks, small, young erythrocytes were seen in the circulation. By measuring the volume distribution of blood samples from anaemic fish before and after noradrenaline stimulation (10 min, 10−5 mol l−1 final concentration), we were able to show that the volume response of young, immature erythrocytes to catecholamine stimulation was greater than that of mature erythrocytes. In addition, the membrane fluidity, measured using the steady-state fluorescence polarisation method, was greater in anaemic fish after 24 days of recovery from bleeding than in control fish. Since blood from anaemic fish contained a large fraction of immature erythrocytes, this result indicates that the fluidity of the membrane of immature erythrocytes is greater than that of mature erythrocytes.
Ventilatory Mechanics and the Effects of Water Depth on Breathing Pattern in the Aquatic Caecilian Typhlonectes Natans
Authors: Prabha KC , Bernard David G. , Gardner Manuela , Smatresk Neal J.
Published: April 2021

The breathing pattern in the aquatic caecilian Typhlonectes natans was investigated by recording airflow via a pneumotachograph under unrestrained normal physiological conditions. Ventilatory mechanics were assessed using airflow and pressure measurements from the buccal cavity and trachea. The breathing pattern consisted of an expiratory phase followed by a series of 10–15 small buccal pumps to inflate the lung, succeeded by a long non-ventilatory period. T. natans separate the expiratory and inspiratory gases in the buccal cavity and take several inspiratory pumps, distinguishing their breathing pattern from that of sarcopterygians. Hydrostatic pressure assisted exhalation. The tracheal pressure was greater than the water pressure at that depth, suggesting that pleuroperitoneal pressure as well as axial or pulmonary smooth muscles may have contributed to the process of exhalation. The frequency of lung ventilation was 6.33±0.84 breaths h−1, and ventilation occurred via the nares. Compared with other amphibians, this low ventilatory frequency suggests that T. natans may have acquired very efficient pulmonary respiration as an adaptation for survival in their seasonally fluctuating natural habitat. Their respiratory pathway is quite unique, with the trachea separated into anterior, central and posterior regions. The anterior region serves as an air channel, the central region is attached to the tracheal lung, and the posterior region consists of a bifurcated air channel leading to the left and right posterior lungs. The lungs are narrow, elongated, profusely vascularized and compartmentalized. The posterior lungs extend to approximately two-thirds of the body length. On the basis of their breathing pattern, it appears that caecilians are phylogenetically derived from two-stroke breathers.
The Influence of Temperature on Power Production During Swimming: II. Mechanics of Red Muscle Fibres In Vivo
Authors: Rome Lawrence C. , Swank Douglas M. , Coughlin David J.
Published: April 2021

We found previously that scup (Stenotomus chrysops) reduce neither their stimulation duration nor their tail-beat frequency to compensate for the slow relaxation rates of their muscles at low swimming temperatures. To assess the impact of this ‘lack of compensation’ on power generation during swimming, we drove red muscle bundles under their in vivo conditions and measured the resulting power output. Although these in vivo conditions were near the optimal conditions for much of the muscle at 20 °C, they were far from optimal at 10 °C. Accordingly, in vivo power output was extremely low at 10 °C. Although at 30 cm s−1, muscles from all regions of the fish generated positive work, at 40 and 50 cm s−1, only the POST region (70 % total length) generated positive work, and that level was low. This led to a Q10 of 4–14 in the POST region (depending on swimming speed), and extremely high or indeterminate Q10 values (if power at 10 °C is zero or negative, Q10 is indeterminate) for the other regions while swimming at 40 or 50 cm s−1.

To assess whether errors in measurement of the in vivo conditions could cause artificially reduced power measurements at 10 °C, we drove muscle bundles through a series of conditions in which the stimulation duration was shortened and other parameters were made closer to optimal. This sensitivity analysis revealed that the low power output could not be explained by realistic levels of systematic or random error. By integrating the muscle power output over the fish’s mass and comparing it with power requirements for swimming, we conclude that, although the fish could swim at 30 cm s−1 with the red muscle alone, it is very unlikely that it could do so at 40 and 50 cm s−1, thus raising the question of how the fish powers swimming at these speeds. By integrating in vivo pink muscle power output along the length of the fish, we obtained the surprising finding that, at 50 cm s−1, the pink muscle (despite having one-third the mass) contributes six times more power to swimming than does the red muscle. Thus, in scup, pink muscle is crucial for powering swimming at low temperatures.

This overall analysis shows that Q10 values determined in experiments on isolated tissue under arbitrarily selected conditions can be very different from Q10 values in vivo, and therefore that predicting whole-animal performance from these isolated tissue experiments may lead to qualitatively incorrect conclusions. To make a meaningful assessment of the effects of temperature on muscle and locomotory performance, muscle performance must be studied under the conditions at which the muscle operates in vivo.
Discontinuous Gas Exchange Cycles in Aphodius Fossor (Scarabaeidae): A Test of Hypotheses Concerning Origins and Mechanisms
Authors: Chown Steven L. , Holter Peter
Published: April 2021

It has been suggested that discontinuous gas exchange cycles (DGCs) in insects evolved in response to hypoxic and/or hypercapnic environments, and that the flutter phase of the DGC is predominantly diffusive. We tested these hypotheses by examining the rate of CO2 release at a declining series of oxygen partial pressures in adults of Aphodius fossor, an inhabitant of moist to wet dung pats that can have low oxygen and high carbon dioxide concentrations. This mesic species showed a pronounced DGC, but progressively abandoned it when exposed to declining oxygen concentrations. That is, in response to a reduction in oxygen concentration, the closed phase declined in length and eventually disappeared, the flutter phase declined in length, while the flutter phase rate of CO2 release increased, the open phase peak rate of CO2 release declined and DGC frequency increased. Nonetheless, overall CO2 release rate remained virtually unchanged. Thus, it appears that the flutter phase in A. fossor has a significant convective component. In addition, in response to declining oxygen concentrations, the spiracles are opened for prolonged periods to increase gas exchange. This behaviour is unlikely to incur a significant water loss penalty in the moist habitats in which A. fossor lives. Given the switch to continuous ventilation by A. fossor under hypoxic conditions, we conclude that current adaptive explanations for the DGC are inadequate. Rather, the DGC may be the default state of a system regulated by two interacting feedback loops when demands are absent.