bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenotypic Plasticity of Early Myogenesis and Satellite Cell Numbers in Atlantic Salmon Spawning in Upland and Lowland Tributaries of a River System
Authors: Johnston Ian A. , Mclay H. Anne , Abercromby Marguerite , Robins Duncan
Published: April 2021

Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a lowland (Sheeoch) and an upland (Baddoch) tributary of the River Dee System, Aberdeenshire, Scotland. Eggs from each population were incubated at the simulated natural thermal regimes of each stream, which was on average 2.8 °C cooler for the Baddoch than for the Sheeoch. Relationships between muscle cellularity variables, the density of myonuclei and responses to temperature were investigated using multivariate statistical techniques. These revealed highly significant temperature effects (P<0.001) at hatch (H) and first feeding (FF) and significant interactions between population and temperature (P<0.001), indicating that Baddoch and Sheeoch salmon responded differently to the two temperature regimes. The total cross-sectional area of white muscle (WF.ta) at the adipose fin was relatively independent of temperature at hatch and first feeding in the Sheeoch population. In contrast, for alevins of Baddoch origin, WF.ta was 18.9 % (H) and 30.5 % (FF) higher in fish incubated at Baddoch than at Sheeoch temperatures. At hatch, there were 15.6 % more white muscle fibres (WF.no) at the cooler incubation temperature in fish of Sheeoch origin and 6.0 % more in fish of Baddoch origin. However, by first feeding, the difference in WF.no between temperatures had narrowed to 7.2 % in the Sheeoch fish and increased to 17.4 % in the Baddoch population. In contrast, at hatch, the density of myonuclei was 59.8 % higher at the warmer incubation temperature in the Sheeoch population and 23.5 % higher in the Baddoch population, but differences were less evident at first feeding. In Baddoch fish, 22.5 % of the total muscle nuclei were actively dividing at first feeding, as assessed by staining for proliferating cell nuclear antigen (PCNA). Of the PCNA-positive nuclei, 78 % were present in cells that stained for the c-met tyrosine kinase receptor, a marker of satellite cells and their division products. The proportion of c-met-positive cells staining for individual myogenic regulatory factors was 72.4 % for the myogenic transcription factor MyoD, 76.3 % for the myogenic transcription factor Myf-5, 62.1 % for myogenin and 48.7 % for the myogenic transcription factor Myf-6. For the Sheeoch population, there were 26.5 % more c-met-expressing (P<0.01) and 23.2 % more myogenic-regulatory-factor-expressing (P<0.05) cells at Sheeoch than at Baddoch temperatures. In contrast, incubation temperature had no significant effects on satellite cell density in the Baddoch population.
Sanderlings (Calidris alba) have a magnetic compass: orientation experiments during spring migration in Iceland
Authors: Gudmundsson G.A. , Sandberg R.
Published: April 2021

The migratory orientation of sanderlings (Calidris alba) was investigated with cage experiments during the spring migration in southwest Iceland. Sanderlings were exposed to 90 degrees counterclockwise-shifted magnetic fields under both clear skies and natural overcast. Clear sky control tests resulted in a northerly mean direction, in agreement with predictions based on ringing recovery data and earlier visual observations of departing flocks. Sanderlings closely followed experimental deflections of magnetic fields when tested under clear skies. Control experiments under natural overcast resulted in a bimodal distribution approximately coinciding with the magnetic north-south axis. Overcast tests did not reveal any predictable response to the experimental treatment, but instead resulted in a non-significant circular distribution. The time of orientation experiments in relation to the tidal cycle affects the motivation of the birds to depart, as shown by the lower directional scatter of headings of individuals tested within the appropriate tidal window under clear skies. Sanderlings were significantly more likely to become inactive under overcast conditions than under clear sky conditions. The results demonstrate, for the first time, that a wader species such as the sanderling possesses a magnetic compass and suggest that magnetic cues are of primary directional importance. However, overcast experiments indicate that both celestial and geomagnetic information are needed for sanderlings to realize a seasonally appropriate migratory orientation.
Colour Constancy of the Swallowtail Butterfly Papilio Xuthus
Authors: Kinoshita Michiyo , Arikawa Kentaro
Published: April 2021

We have recently shown that the Japanese yellow swallowtail butterfly Papilio xuthus uses colour vision when searching for food. In the field, these butterflies feed on nectar provided by flowers of various colours not only in direct sunlight but also in shaded places and on cloudy days, suggesting that they have colour constancy. Here, we tested this hypothesis. We trained newly emerged Papilio xuthus to feed on sucrose solution on a paper patch of a certain colour under white illumination. The butterflies were then tested under both white and coloured illumination. Under white illumination, yellow- and red-trained butterflies selected the correctly coloured patch from a four-colour pattern and from a colour Mondrian collage. Under four different colours of illumination, we obtained results that were fundamentally similar to those under white illumination. Moreover, we performed critical tests using sets of two similar colours, which were also correctly discriminated by trained butterflies under coloured illumination. Taken together, we conclude that the butterfly Papilio xuthus exhibits some degree of colour constancy when searching for food.
Mass Spectrometric Survey of Peptides in Cephalopods With an Emphasis on the Fmrfamide-Related Peptides
Authors: Sweedler Jonathan V. , Li Lingjun , Floyd Philip , Gilly William
Published: April 2021

A matrix-assisted laser desorption/ionization (MALDI) mass spectrometric (MS) survey of the major peptides in the stellar, fin and pallial nerves and the posterior chromatophore lobe of the cephalopods Sepia officinalis, Loligo opalescens and Dosidicus gigas has been performed. Although a large number of putative peptides are distinct among the three species, several molecular masses are conserved. In addition to peptides, characterization of the lipid content of the nerves is reported, and these lipid peaks account for many of the lower molecular masses observed. One conserved set of peaks corresponds to the FMRFamide-related peptides (FRPs). The Loligo opalescens FMRFa gene has been sequenced. It encodes a 331 amino acid residue prohormone that is processed into 14 FRPs, which are both predicted by the nucleotide sequence and confirmed by MALDI MS. The FRPs predicted by this gene (FMRFa, FLRFa/FIRFa and ALSGDAFLRFa) are observed in all three species, indicating that members of this peptide family are highly conserved across cephalopods.
Processes Contributing To Metabolic Depression In Hepatopancreas Cells From The SnailHelix Aspersa
Authors: Bishop T. , Brand M. D.
Published: April 2021

Cells isolated from the hepatopancreas of the land snail Helix aspersa strongly depress respiration both immediately in response to lowered (oxygen conformation) and, in the longer term, during aestivation. These phenomena were analysed by dividing cellular respiration into non-mitochondrial and mitochondrial respiration using the mitochondrial poisons myxothiazol, antimycin and azide. Non-mitochondrial respiration accounted for a surprisingly large proportion, 65±5 %, of cellular respiration in control cells at 70 % air saturation. Non-mitochondrial respiration decreased substantially as oxygen tension was lowered, but mitochondrial respiration did not, and the oxygen-conforming behaviour of the cells was due entirely to the oxygen-dependence of non-mitochondrial oxygen consumption. Non-mitochondrial respiration was still responsible for 45±2 % of cellular respiration at physiological oxygen tension. Mitochondrial respiration was further subdivided into respiration used to drive ATP turnover and respiration used to drive futile proton cycling across the mitochondrial inner membrane using the ATP synthase inhibitor oligomycin. At physiological oxygen tensions, 34±5 % of cellular respiration was used to drive ATP turnover and 22±4 % was used to drive proton cycling, echoing the metabolic inefficiency previously observed in liver cells from mammals, reptiles and amphibians. The respiration rate of hepatopancreas cells from aestivating snails was only 37 % of the control value. This was caused by proportional decreases in non-mitochondrial and mitochondrial respiration and in respiration to drive ATP turnover and to drive proton cycling. Thus, the fraction of cellular respiration devoted to different processes remained constant and the cellular energy balance was preserved in the hypometabolic state.
Sexual Dimorphism in Forelimb Muscles of the Bullfrog,Rana Catesbeiana: A Functional Analysis of Isometric Contractile Properties
Authors: Peters Susan E. , Aulner Dwane A.
Published: April 2021

In many species of frog, the forelimb muscles important in amplexus are known to be much larger in males than in females. We studied this dimorphism in three forelimb muscles in the bullfrog [abductor indicus longus (AIL), flexor carpi radialis (FCR) and extensor carpi radialis (ECR)] by testing their isometric contractile properties. One muscle that is not dimorphic, the extensor carpi ulnaris (ECU), was also studied as a control. In addition to being greater in wet mass and in cross-sectional area in the males, our data show that the dimorphic muscles also produce significantly larger isometric forces in males than in females. The tetanic force per cm2 of muscle cross-sectional area did not differ between the sexes, so that force within a muscle varies directly with muscle size. However, a number of the contractile variables we measured show that male muscles differ functionally from those of females. The male twitch contraction times were significantly longer in the AIL, and the male half-relaxation times were longer in both the AIL and FCR. These two dimorphic muscles were also significantly less fatiguable in males than were the corresponding female muscles. Their higher endurance resulted from the maintenance of high levels of unrelaxed force sustained between trains of stimuli during the fatigue test. This sustained force is much less pronounced in the female muscles, suggesting that high levels of sustained force may be a key functional feature that enables males to maintain amplexus economically for prolonged periods.
Relative Metabolic Utilization ofin situRabbit Soleus Muscle: Thermistor-Based Measurements And Model
Authors: Gustafson Kenneth J. , Egrie Glenn D. , Reichenbach Steven H.
Published: April 2021

Electrically conditioned skeletal muscle can provide the continuous power source for cardiac assistance devices. Optimization of the available sustained power from in vivo skeletal muscle requires knowledge of its metabolic utilization and constraints. A thermistor-based technique has been developed to measure temperature changes and to provide a relative estimate for metabolic utilization of in situ rabbit soleus muscle. The relative thermistor response, active tension and muscle displacement were measured during cyclic isometric and isotonic contractions across a range of muscle tensions and contraction durations. The thermistor response demonstrated linear relationships versus both contraction duration at a fixed muscle length and active tension at a fixed contraction duration (r2=0.90±0.14 and 0.70±0.21, respectively; means ± S.D.). A multiple linear regression model was developed to predict normalized thermistor response, ΔT, across a range of conditions. Significant model variables were identified using a backward stepwise regression procedure. The relationships for the in situ muscles were qualitatively similar to those reported for mammalian in vitro muscle fiber preparations. The model had the form ΔT=C+atcF+bW, where the constant C, and coefficients for the contraction duration tc (ms), normalized active tension F and normalized net work W were C=−1.00 (P<0.001), a=5.97 (P<0.001) and b=2.12 (P<0.001).
Local Movements Evoked by Chemical Stimulation of the Hind leg in the Locust Schistocerca Gregaria
Authors: Rogers Stephen M. , Newland Philip L.
Published: April 2021

The behavioural responses of desert locusts, Schistocerca gregaria, to solutions of four behaviourally relevant chemicals (sodium chloride, sucrose, nicotine hydrogen tartrate and lysine glutamate) applied as droplets to the hind tarsus were analysed. All responses following within 1 s of chemical stimulation were local leg avoidance reflexes, and the probability of eliciting such a response increased in a dose-dependent manner with increasing concentration for all the chemicals tested. Chemical identity, however, critically determined the concentration threshold at which the different chemicals became an effective stimulus. For example, a 2.5 mmol l−1 concentration of the secondary plant metabolite nicotine hydrogen tartrate (NHT), a potent feeding deterrent to locusts, was sufficient to evoke avoidance responses in 50 % of cases, whilst for the nutrients, sucrose and lysine glutamate, 250–500 mmol l−1 of the chemical was needed to induce avoidance behaviour in 50 % of the locusts. NaCl was of intermediate effectiveness, with a 50 % response rate occurring at a concentration of approximately 50 mmol l−1. The latency to the start of the response following stimulation was negatively correlated with the concentration of NaCl, but for the other chemicals concentration had no effect on latency. The duration of the avoidance behaviour decreased with increasing concentration for NaCl and more weakly for NHT, but not for the other chemicals. Adding a subthreshold concentration of sucrose to 50 mmol l−1 NaCl decreased the incidence of response compared with 50 mmol l−1 NaCl on its own. Experiments with other mixtures combining NaCl, sucrose and NHT indicate that the frequency and dynamics of the responses to chemical mixtures cannot be simply predicted from the responses to their individual constituents.
Effects of Temperature on Escape Jetting in the Squid Loligo Opalescens
Authors: Neumeister H. , Ripley B. , Preuss T. , Gilly W. F.
Published: April 2021

In Loligo opalescens, a sudden visual stimulus (flash) elicits a stereotyped, short-latency escape response that is controlled primarily by the giant axon system at 15 °C. We used this startle response as an assay to examine the effects of acute temperature changes down to 6 °C on behavioral and physiological aspects of escape jetting. In free-swimming squid, latency, distance traveled and peak velocity for single escape jets all increased as temperature decreased. In restrained squid, intra-mantle pressure transients during escape jets increased in latency, duration and amplitude at low temperature. Recordings of stellar nerve activity revealed repetitive firing of the giant motor axon accompanied by increased activity in the non-giant motor axons that run in parallel. Selective stimulation of giant and non-giant motor axons in isolated nerve–muscle preparations failed to show the effects seen in vivo, i.e. increased peak force and increased neural activity at low temperature. Taken together, these results suggest that L. opalescens is able to compensate escape jetting performance for the effects of acute temperature reduction. A major portion of this compensation appears to occur in the central nervous system and involves alterations in the recruitment pattern of both the giant and non-giant axon systems.
Comparison of a Ca2+-Gated Conductance and a Second-Messenger-Gated Conductance in Rat Olfactory Neurons
Authors: Okada Yukio , Fujiyama Rie , Miyamoto Takenori , Sato Toshihide
Published: April 2021

The effect of a rise in intracellular Ca2+ concentration was analyzed in isolated rat olfactory neurons using a whole-cell patch-clamp technique. Intracellular dialysis of 1 mmol l−1 Ca−1 in a standard-K+, low-Cl− internal solution (ECl=−69 mV) from the patch pipette into the olfactory neurons induced a sustained outward current of 49±5 pA (N=13) at −50 mV in all the cells examined. The outward currents were inhibited by external application of 100 μmol l−1 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB). External application of a Ca2+ ionophore, 3 μmol l−1 ionomycin, induced an inward current in three of eight cells whose voltages were clamped using the gramicidin-perforated technique, but ionomycin elicited an outward current in the other five cells, suggesting that natural intracellular Cl− concentration in the olfactory neurons was heterogeneous. While intracellular dialysis of 50 μmol l−1 inositol 1,4,5-trisphosphate (1,4,5-InsP3) in the standard-K+, low-Cl− internal solution induced the NPPB-sensitive outward current in 31 % of cells, and 500 μmol l−1 cAMP induced it in 21 % of cells, a large proportion of the cells displayed an inward current in response to 1,4,5-InsP3 and cAMP. The results suggest that 1,4,5-InsP3 and cAMP can elicit Ca2+-dependent Cl− conductance and Ca2+-independent cation conductance in rat olfactory neurons.
Pacap and Nitric Oxide Inhibit Contractions in the Proximal Intestine of the Atlantic Cod, Gadus Morhua
Authors: Olsson Catharina , Holmgren Susanne
Published: April 2021

The possible inhibitory roles of pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP) and nitric oxide in the control of intestinal motility were investigated in the Atlantic cod, Gadus morhua. Circular and longitudinal smooth muscle preparations developed spontaneous contractions that were inhibited by atropine (10−5 mol l−1). PACAP 27 and PACAP 38 (10−7 mol l−1) reduced the amplitude of the contractions but did not usually affect the resting tension. In the circular preparations, the mean active force developed (above resting level; ± S.E.M.) was reduced from 0.62±0.18 mN to 0.03±0.03 mN (N=10) by PACAP 27 and from 0.53±0.20 mN to 0.31±0.13 mN (N=7) by PACAP 38, while neither cod nor mammalian VIP (10−10–10−6 mol l−1) had any effect. In the longitudinal preparations, PACAP 27 reduced the force developed from 1.58±0.22 mN to 0.44±0.25 mN (N=8) and PACAP 38 reduced it from 1.61±0.47 mN to 0.75±0.28 mN (N=5). The nitric oxide donor sodium nitroprusside (NaNP) almost abolished the contractions in the circular preparations, reducing the mean force developed from 0.47±0.05 mN to 0.02±0.06 mN (10−6 mol l−1; N=9) and 0±0.07 mN (10−5 mol l−1; N=8). In the longitudinal preparations, NaNP reduced the force developed from 2.03±0.36 mN to 0.33±0.22 mN (10−6 mol l−1; N=8) and 0.19±0.30 mN (10−5 mol l−1; N=8). The L-arginine analogue NG-nitro-L-arginine methyl ester (L-NAME; 3×10−4 mol l−1) enhanced the contractions in both circular and longitudinal preparations, increasing the mean force developed from 0.51±0.12 mN to 0.94±0.21 mN (N=8) and from 1.49±0.36 mN to 3.34±0.67 mN (N=7), respectively. However, preincubation with L-NAME before a second addition of PACAP 27 (10−7 mol l−1) did not affect the response to PACAP, neither did preincubation with the guanylate cyclase inhibitor 6-anilinoquinoline-5,8-quinone (LY83583; 10−5 mol l−1), while the inhibitory response to NaNP (3×10−7 mol l−1) was abolished by LY83583. The PACAP analogue PACAP 6-27 (3×10−7 mol l−1) had no effect on the response to either NaNP (3×10−7 mol l−1) or PACAP 27 (10−8 mol l−1) in the circular preparations. These findings indicate the presence of both a cholinergic and a nitrergic tonus in the smooth muscle preparations of the cod. Although PACAP and NaNP both inhibit contractions, there is no evidence of any interactions between the two substances. In addition, NaNP, but not PACAP, probably acts via stimulating the production of cyclic GMP. In conclusion, both PACAP and nitric oxide may act as inhibitory transmitters, using distinct signalling pathways, in the control of intestinal motility in the Atlantic cod.
Song Recognition in Female Bushcrickets Phaneroptera Nana
Authors: Tauber E. , Pener M. P.
Published: April 2021

Unlike most acoustic systems evolved for pair formation, in which only males signal, in many species of phaneropterine bushcrickets both sexes sing, producing a duet. We used the duetting species Phaneroptera nana as a model to explore the cues in the male’s song that elicit the female’s phonoresponse. Different synthetic male songs (chirps containing 2–6 pulses) were presented to Ph. nana females, and their acoustic responses were recorded. The threshold of the female response is lowest at 16 kHz (best frequency), coinciding with the dominant frequency of the male song. The specific amplitude pattern of consecutive pulses in the song of the male is not a critical factor in his signal. That is, songs with both a normal and a reversed order of pulses equally elicit a female response. By systematically deleting pulses from the synthetic male chirp, we found that at least two pulses are needed to elicit a female reply. Under no-choice conditions, increasing the number of pulses did not result in a higher probability of response and did not change the latency of the response; i.e. two pulses are necessary and sufficient to elicit a female response. The range of pulse duration that elicits a female response is 0.2–25 ms, and the inter-pulse silent interval ranges from 5 to 30 ms.
Antidiuretic Effects of a Factor in Brain/Corpora Cardiaca/Corpora Allata Extract on Fluid Reabsorption Across the Cryptonephric Complex of Manduca Sexta
Authors: Liao Sha , Audsley Neil , Schooley David A.
Published: April 2021

Extracts of the brain/corpora cardiaca/corpora allata (Br/CC/CA) complex of Manduca sexta larvae elicit an antidiuretic effect, measured by an increase in fluid reabsorption across the cryptonephric complex of larval M. sexta. Separation of the extract by reversed-phase liquid chromatography gave two fractions with antidiuretic effects. The more potent of these two factors was further characterized for its effects on the cryptonephric complex. Its antidiuretic effect is not inhibited by bumetanide, a drug that inhibits M. sexta diuretic hormone (Mas-DH)-stimulated fluid reabsorption. These data indicate that the mechanism of the antidiuretic effect of the factor is different from that of Mas-DH on the cryptonephric complex. The basal reabsorption of the cryptonephric complex is blocked when treated on the lumen side with bafilomycin A1, an inhibitor of the H+-ATPase, or with amiloride, an inhibitor of the H+/K+ antiporter. However, the antidiuretic-factor-stimulated fluid reabsorption is not affected by either bafilomycin A1 or amiloride. The increase in reabsorption triggered by the semi-purified factor can be inhibited by Cl− channel blockers or by removing Cl− from the lumen side of the cryptonephric complex. It appears that this factor activates a Cl− pump associated with the cryptonephric complex. Forskolin mimics the effect of this factor on fluid reabsorption, and the effect of forskolin is not inhibited by bumetanide. A selective and potent inhibitor of protein kinase A, H-89, also inhibits antidiuretic-factor-stimulated fluid reabsorption. Addition of the factor to cryptonephric complexes maintained in vitro caused a significant increase in cyclic AMP levels extracted from these tissues compared with values for controls. These data suggest that the antidiuretic effect of the factor in Br/CC/CA extract is mediated by cyclic AMP.
Molecular Systematics of the African Electric Fishes (Mormyroidea: Teleostei) and A Model for the Evolution of Their Electric Organs
Authors: Sullivan John P. , Lavoué Sébastien , Hopkins Carl D.
Published: April 2021

We present a new molecular phylogeny for 41 species of African mormyroid electric fishes derived from the 12S, 16S and cytochrome b genes and the nuclear RAG2 gene. From this, we reconstruct the evolution of the complex electric organs of these fishes. Phylogenetic results are generally concordant with earlier preliminary molecular studies of a smaller group of species and with the osteology-based classification of Taverne, which divides the group into the Gymnarchidae and the Mormyridae, with the latter including the subfamilies Petrocephalinae (Petrocephalus) and Mormyrinae (all remaining taxa). However, we find that several genera previously recognized by Taverne are non-monophyletic. Within the Mormyrinae, the genus Myomyrus is the sister group to all the remaining taxa. Other well-supported clades within this group are recovered. A reconstruction of electrocyte evolution on the basis of our best-supported topology suggests that electrocytes with penetrating stalks evolved once early in the history of the mormyrids followed by multiple paedomorphic reversals to electrocytes with non-penetrating stalks.
Serotonin Activates A Ca2+-Dependent K+ Current in Identified Peptidergic Neurons from the Crayfish
Authors: Alvarado-Álvarez Ramón , Aréchiga Hugo , García Ubaldo
Published: April 2021

The effects of 5-hydroxytryptamine (5-HT) were investigated in red pigment concentrating hormone (RPCH)-containing neurons isolated from the X-organ of the crayfish (Procambarus clarkii). Under current-clamp conditions and using the gramicidin-perforated-patch configuration, 5-HT elicited a prolonged hyperpolarization that suppressed neuronal firing concomitant with an increase in membrane conductance. Under voltage-clamp conditions, 5-HT evoked an outward current at a holding potential of −50 mV. This current reversed at an EK of −90 mV, which shifted by 30 mV when the extracellular K+ concentration was increased from 5.4 to 19 mmol l−1. The effect of 5-HT was dose-dependent within the range 1–100 μmol l−1 and followed simple

Michaelis–Menten kinetics, with a half-maximal response being elicited at 10 μmol l−1. Preincubation with charybdotoxin (100 nmol l−1), tetraethylammonium (500 μmol l−1) or methysergide (100 μmol l−1) was effective in blocking the response to 5-HT. These results suggest that 5-HT is an inhibitory mediator of the release of red pigment concentrating hormone by acting on a Ca2+-dependent K+ current.
Effect of Wind and Solar Radiation on Metabolic Heat Production in a Small Desert Rodent, Spermophilus Tereticaudus
Authors: Wooden K. Mark , Walsberg Glenn E.
Published: April 2021

To understand better how complex interactions between environmental variables affect the energy balance of small diurnal animals, we studied the effects of the absence and presence of 950 W m−2 simulated solar radiation combined with wind speeds ranging from 0.25 to 1.00 m s−1 on the metabolic rate and body temperature of the round-tailed ground squirrel Spermophilus tereticaudus. As wind speed increased from 0.25 to 1.00 m s−1, metabolic heat production increased by 0.94 W in the absence of solar radiation and by 0.98 W in the presence of 950 W m−2 simulated solar radiation. Exposure to simulated solar radiation reduced metabolic heat production by 0.68 W at a wind speed of 0.25 m s−1, by 0.64 W at 0.50 m s−1 and by 0.64 W at 1.00 m s−1. Body temperature was significantly affected by environmental conditions, ranging from 32.5 °C at a wind speed of 1.0 m s−1 and no irradiance to 35.6 °C at a wind speed of 0.50 m s−1 with 950 W m−2 short-wave irradiance.

In addition, several unusual findings resulted from this study. The coat of S. tereticaudus is very sparse, and the observed heat transfer of 5.68±0.37 W m−2 °C−1 (mean ± S.E.M., N=11) is much higher than expected from either allometric equations or comparative studies with other rodents of similar mass. Solar heat gain was remarkably low, equalling only 10 % of intercepted radiation and suggesting a remarkably high regional thermal resistance at the tissue level. Animals remained normally active and alert at body temperatures as low as 32.5 °C. These findings suggest a unique combination of adaptations that allow S. tereticaudus to exploit a harsh desert environment.
Sun-Compass Orientation in Homing Pigeons: Compensation for Different Rates of Change in Azimuth?
Authors: Wiltschko Roswitha , Walker Michael , Wiltschko Wolfgang
Published: April 2021

Birds using their sun compass must compensate for the apparent movement of the sun with the help of their internal clock. The movement of the sun is not uniform, being much faster around noon than near sunrise and sunset. If the sun-compass mechanisms are not adjusted to these variations, considerable errors might arise. To learn whether birds are able to take the different rates of sun azimuth change into account, we subjected homing pigeons to a 4 h fast clock-shift. The experiments were performed near Auckland, New Zealand, at a latitude of 37°S, where the expected deflections for a 4 h shift in summer vary from less than 40 ° to more than 120 °, depending on time of day. One group of birds was released just after sunrise or during the corresponding period in the afternoon when the expected deflections were minimal, the other group during late morning when they were maximal. The different sizes of the observed deflections – between 26 ° and 51 ° in the first group, and between 107 ° and 153 ° in the second group – clearly show that the birds’ compensation mechanisms are closely tuned to the varying rates of change in sun azimuth. The results suggest that pigeons have a rather precise internal representation of the sun curve, which makes the avian sun compass a highly accurate mechanism of direction finding.
Avian Pectoral Muscle Size Rapidly Tracks Body Mass Changes During Flight, Fasting and Fuelling
Authors: Lindström Åke , Kvist Anders , Piersma Theunis , Dekinga Anne , Dietz Maurine W.
Published: April 2021

We used ultrasonic imaging to monitor short-term changes in the pectoral muscle size of captive red knots Calidris canutus. Pectoral muscle thickness changed rapidly and consistently in parallel with body mass changes caused by flight, fasting and fuelling. Four knots flew repeatedly for 10 h periods in a wind tunnel. Over this period, pectoral muscle thickness decreased in parallel with the decrease in body mass. The change in pectoral muscle thickness during flight was indistinguishable from that during periods of natural and experimental fasting and fuelling. The body-mass-related variation in pectoral muscle thickness between and within individuals was not related to the amount of flight, indicating that changes in avian muscle do not require power-training as in mammals. Our study suggests that it is possible for birds to consume and replace their flight muscles on a time scale short enough to allow these muscles to be used as part of the energy supply for migratory flight. The adaptive significance of the changes in pectoral muscle mass cannot be explained by reproductive needs since our knots were in the early winter phase of their annual cycle. Instead, pectoral muscle mass changes may reflect (i) the breakdown of protein during heavy exercise and its subsequent restoration, (ii) the regulation of flight capacity to maintain optimal flight performance when body mass varies, or (iii) the need for a particular protein:fat ratio in winter survival stores.
A Conserved Location For the Central Nervous System Control of Mating Behaviour in Gastropod Molluscs: Evidence From a Terrestrial Snail
Authors: Koene Joris M. , René Jansen F. , Maat Andries Ter , Chase Ronald
Published: April 2021

We have investigated the role of the right mesocerebrum in the expression of mating behaviour in the garden snail Helix aspersa. Using an in vivo stimulation and recording technique, we provide evidence for both sensory and motor functions in the mesocerebral neuronal population. Some neurones were specifically sensitive to tactile stimuli delivered to the skin on the superior tentacles and around the genital pore. Electrical stimulation of the right mesocerebrum evoked genital eversion and, in combination with tactile stimulation, dart-shooting and penial eversion. Genital eversions were also elicited by injections of APGWamide. During courtship, one recorded unit increased its activity only in correlation with penial eversion, while six other units increased their activity only during dart-shooting. Three additional units increased their activity during both types of behaviour. In addition, most of the recorded units showed increased neuronal activity during times of contact with a partner. Comparison of our results with available data from other molluscs leads us to conclude that the right anteromedial region of the cerebral ganglion is an evolutionarily conserved region of the gastropod brain specialised for the control of male mating behaviour. It is striking to find such functional conservation in the central nervous system of phylogenetically distant gastropods given the large differences in behaviour during mating.
Infrasound and the Avian Navigational Map
Authors: Hagstrum Jonathan T.
Published: April 2021

Birds can navigate accurately over hundreds to thousands of kilometres, and this ability of homing pigeons is the basis for a worldwide sport. Compass senses orient avian flight, but how birds determine their location in order to select the correct homeward bearing (map sense) remains a mystery. Also mysterious are rare disruptions of pigeon races in which most birds are substantially delayed and large numbers are lost. Here, it is shown that in four recent pigeon races in Europe and the northeastern USA the birds encountered infrasonic (low-frequency acoustic) shock waves from the Concorde supersonic transport. An acoustic avian map is proposed that consists of infrasonic cues radiated from steep-sided topographic features; the source of these signals is microseisms continuously generated by interfering oceanic waves. Atmospheric processes affecting these infrasonic map cues can explain perplexing experimental results from pigeon releases.
Genetic approaches to understanding human adaptation to altitude in the Andes
Authors: Rupert J. L. , Hochachka P. W.
Published: April 2021

Despite the initial discomfort often experienced by visitors to high altitude, humans have occupied the Andean altiplano for more than 10000 years, and millions of people, indigenous and otherwise, currently live on these plains, high in the mountains of South America, at altitudes exceeding 3000m. While, to some extent, acclimatisation can accommodate the one-third decrease in oxygen availability, having been born and raised at altitude appears to confer a substantial advantage in high-altitude performance compared with having been born and raised at sea level. A number of characteristics have been postulated to contribute to a high-altitude Andean phenotype; however, the relative contributions of developmental adaptation (within the individual) and genetic adaptation (within the population of which the individual is part) to the acquisition of this phenotype have yet to be resolved.

A complex trait is influenced by multiple genetic and environmental factors and, in humans, it is inherently very difficult to determine what proportion of the trait is dictated by an individual’s genetic heritage and what proportion develops in response to the environment in which the person is born and raised. Looking for changes in putative adaptations in vertically migrant populations, determining the heritability of putative adaptive traits and genetic association analyses have all been used to evaluate the relative contributions of nurture and nature to the Andean phenotype. As the evidence for a genetic contribution to high-altitude adaptation in humans has been the subject of several recent reviews, this article instead focuses on the methodology that has been employed to isolate the effects of ‘nature’ from those of ‘nurture’ on the acquisition of the high-altitude phenotype in Andean natives (Quechua and Aymara). The principles and assumptions underlying the various approaches, as well as some of the inherent strengths and weaknesses of each, are briefly discussed.
Dual ecdysteroid action on the epitracheal glands and central nervous system preceding ecdysis ofManduca sexta
Authors: Žitňanová Inka , Adams Michael E. , Žitňan Dušan
Published: April 2021

Initiation of the ecdysis behavioural sequence in insects requires activation of the central nervous system (CNS) by pre-ecdysis-triggering hormone (PETH) and ecdysis-triggering hormone (ETH), which are released from the Inka cells of the epitracheal glands. Here, we show that the developmental events preceding larval and pupal ecdysis of Manduca sexta involve a dual action of ecdysteroids on the epitracheal glands and CNS. The low steroid levels in freshly ecdysed and feeding larvae are associated with small-sized epitracheal glands, reduced peptide production in Inka cells and insensitivity of the CNS to ETH. The elevated ecdysteroid levels before each ecdysis lead to a dramatic enlargement of Inka cells and increased production of peptide hormones and their precursors. As blood ecdysteroids reach peak levels, the CNS becomes responsive to Inka cell peptides. These effects of natural ecdysteroid pulses can be experimentally induced by injection of 20-hydroxyecdysone or the ecdysteroid agonist tebufenozide (RH-5992) into ecdysed larvae, thus stimulating peptide production in Inka cells and inducing CNS sensitivity to ETH. A direct steroid action on the CNS is demonstrated by subsequent treatment of isolated nerve cords from ecdysed larvae with 20-hydroxyecdysone and ETH, which results in pre-ecdysis or ecdysis bursts. Our data show that ecdysteroid-induced transcriptional activity in both the epitracheal glands and the CNS are necessary events for the initiation of the ecdysis behavioural sequence.
Caudal differential pressure as a predictor of swimming speed of cod (Gadus morhua)
Authors: Webber D. M. , Boutilier R. G. , Kerr S. R. , Smale M. J.
Published: April 2021

We report the results of an experiment designed to investigate the feasibility of using differential pressure to estimate the swimming speed and metabolic rate of Atlantic cod (Gadus morhua). Seven cod were fitted with a miniature differential pressure sensor mounted on one side of the caudal peduncle immediately anterior to the base of the caudal fin rays. Relationships between differential pressure, tailbeat frequency, tailbeat amplitude, swimming speed and rate of oxygen consumption (ṀO2) were determined as a function of the swimming speed of cod swimming at 5°C in a recirculating ‘Brett-style’ respirometer. Tailbeat differential pressure, tailbeat amplitude and tailbeat frequency were highly correlated with swimming speed. The average or integrated pressure ranged from 0 to 150 Pa for speeds up to 0.8 m s–1 (1.1 L s–1, where L is total body length), while the ‘pressure difference’ (maximum minus minimum pressure) ranged from 0 to 900 Pa. Small changes in swimming speed of less than 0.05 m s–1 were readily detected as differences in tailbeat pressure. Burst swimming in the respirometer resulted in huge pressure ‘bursts’ of up to 5000 Pa ‘pressure difference’.

The rate of oxygen consumption increased exponentially and was highly correlated with swimming speed (r2=0.77). The rate of oxygen consumption was also correlated with tailbeat integrated pressure (r2=0.68) and with differential pressure (r2=0.43); regression correlations were always greater for individuals than for combined data from all cod.

The results detailed in this study indicate that an ultrasonic differential pressure transmitter would enable accurate estimates of the swimming speed, rates of oxygen consumption and activity patterns of free-ranging fish in nature.
Embryonic temperature and the relative timing of muscle-specific genes during development in herring (Clupea harengusL.)
Authors: Temple Genevieve K. , Cole Nicholas J. , Johnston Ian A.
Published: April 2021

Temperature influences many aspects of muscle development in herring (Clupea harengus). In Clyde herring, myofibril synthesis occurred later with respect to somite stage in embryos reared at 5°C compared with 12°C. The aim of the present study was to test the hypothesis that the relative timing of expression of myogenic regulatory factors (MRFs) and myosin heavy chain (MyHC) transcripts changes with developmental temperature. Reverse transcriptase/polymerase chain reaction (RT-PCR) was used to clone partial coding regions of MyoD, myogenin and MyHC from juvenile Clyde herring. Embryos were reared at 5, 8 and 12°C, and the spatial and temporal expression patterns of transcripts were investigated using cRNA probes and in situ hybridisation. Antisense probes revealed a rostral–caudal progression of all three transcripts. MyoD transcription initially took place in the adaxial cells of the unsegmented, presomitic mesoderm, whereas myogenin transcription first occurred in newly formed somites. The MyHC gene transcript was not detected until approximately nine somites had formed. Since the somite stage at which the MRFs and MyHC were first expressed was independent of temperature, the hypothesis was rejected. We suggest that the effects of temperature on myofibril synthesis must occur downstream from MyHC transcription either at the level of translation or at the assembly stage.
Effects of stretch receptor ablation on the optomotor control of lift in the hawkmothManduca sexta
Authors: Frye Mark A.
Published: April 2021

In insects, fast sensory feedback from specialized mechanoreceptors is integrated with guidance cues descending from the visual system to control flight behavior. A proprioceptive sensory organ found in both locusts and moths, the wing hinge stretch receptor, has been extensively studied in locusts for its powerful influence on the activity of flight muscle motoneurons and interneurons. The stretch receptor fires a high-frequency burst of action potentials near the top of each wingstroke and encodes kinematic variables such as amplitude and timing. Here, I describe the effects of stretch receptor ablation on the visual control of lift during flight in the hawkmoth Manduca sexta. Using a combination of extracellular muscle recordings, force and position measurements and high-speed video recording, I tracked power muscle activity, net vertical flight force (lift), abdomen deflection and wing kinematics in response to image motions of varying velocity during tethered flight in a wind tunnel. As a result of bilateral ablation of the wing hinge stretch receptors, visually evoked lift decreased to nearly one-third of that exhibited by intact animals. The phase and frequency of indirect power muscle action potentials and the patterns of abdominal deflection were unaffected; however, wingstroke amplitude was clearly reduced after ablation. Collectively, these results suggest that stretch receptor feedback is integrated with descending visual cues to control wing kinematics and the resultant aerodynamic force production during flight.
Encoding properties of the wing hinge stretch receptor in the hawkmothManduca sexta
Authors: Frye Mark A.
Published: April 2021

To characterize the in vivo responses of the wing hinge stretch receptor of Manduca sexta, I recorded its activity and simultaneously tracked the up-and-down motion of the wing while the hawkmoth flew tethered in a wind tunnel. The stretch receptor fires a high-frequency burst of spikes near each dorsal stroke reversal. The onset of the burst is tightly tuned to a set-point in wing elevation, and the number of spikes contained within the burst encodes the maximal degree of wing elevation during the stroke. In an effort to characterize its mechanical encoding properties, I constructed an actuator that delivered deformations to the wing hinge and simultaneously recorded the resultant stretch and tension and the activity of the stretch receptor. Stimuli included stepwise changes in length as well as more natural dynamic deformation that was measured in vivo. Step changes in length reveal that the stretch receptor encodes the static amplitude of stretch with both phasic and tonic firing dynamics. In vivo sinusoidal deformation revealed (i) that the timing of stretch receptor activity is tightly phase-locked within the oscillation cycle, (ii) that the number of spikes per burst is inversely related to oscillation frequency and (iii) that the instantaneous frequency of the burst increases with oscillation rate. At all oscillation rates tested, the instantaneous frequency of the burst increases with amplitude.
The femur–tibia control system in a proscopiid (Caelifera, Orthoptera): a test for assumptions on the functional basis and evolution of twig mimesis in stick insects
Authors: Wolf Harald , Bässler Ulrich , Spieß Roland , Kittmann Rolf
Published: April 2021

The extremely slow return movements observed in stick insects (phasmids) after imposed changes in posture are termed catalepsy. In the literature, catalepsy is treated as a behavioural component of the twig mimesis observed in walking stick insects. It is produced by the high gain of the velocity-sensitive component of the relevant joint control systems and by the non-linear dependency of its time constant on movement velocity. The high gain, in turn, causes the system to work close to instability, and this may have driven the evolution of gain control mechanisms. Although these statements represent plausible assumptions, based on correlated occurrence, they remain largely hypothetical like many ideas concerning evolutionary tendencies. To test these hypotheses, we studied catalepsy and the relevant properties of the femur–tibia control system in the middle and hind legs of Prosarthria teretrirostris.cf. Prosarthria teretrirostris is a proscopiid closely related to grasshoppers and locusts. With its slender, green-to-brown body and legs, it shows clear morphological twig mimesis, which has evolved independently of the well-known twig mimesis in stick insects. The animals show clear catalepsy. The main properties of femur–tibia joint control are remarkably similar between proscopiids and stick insects (e.g. the marked sensitivity to movement velocity rather than to joint position and the non-linear dependency of the time constants of response decay on movement velocity), but there are also important differences (habituation and activity-related mechanisms of gain control are absent). Together, these results validate the main concepts that have been developed concerning the neural basis and evolution of catalepsy in stick insects and its relationship to twig mimesis, while demonstrating that ideas on the role of habituation and gain control should be refined.
Hearing and whistling in the deep sea: depth influences whistle spectra but does not attenuate hearing by white whales (Delphinapterus leucas) (Odontoceti, Cetacea)
Authors: Ridgway Sam H. , Carder Donald A. , Kamolnick Tricia , Smith Robert R. , Schlundt Carolyn E. , Elsberry Wesley R.
Published: April 2021

Hearing is attenuated in the aerial ear of humans and other land mammals tested in pressure chambers as a result of middle ear impedance changes that result from increased air density. We tested the hypothesis, based on recent middle ear models, that increasing the density of middle ear air at depth might attenuate whale hearing. Two white whales Delphinapterus leucas made dives to a platform at a depth of 5, 100, 200 or 300 m in the Pacific Ocean. During dives to station on the platform for up to 12 min, the whales whistled in response to 500 ms tones projected at random intervals to assess their hearing threshold at each depth. Analysis of response whistle spectra, whistle latency in response to tones and hearing thresholds showed that the increased hydrostatic pressure at depth changed each whale’s whistle response at depth, but did not attenuate hearing overall. The finding that whale hearing is not attenuated at depth suggests that sound is conducted through the head tissues of the whale to the ear without requiring the usual ear drum/ossicular chain amplification of the aerial middle ear. These first ever hearing tests in the open ocean demonstrate that zones of audibility for human-made sounds are just as great throughout the depths to which these whales dive, or at least down to 300 m.