bluuebunny/crossref_metadata_2025 huggingface dataset:
Seven Theses on Pigeon Homing Deduced From Empirical Findings
Authors: Wallraff Hans G.
Published: April 2021

Experimental findings obtained in recent years make it possible to recognize and distinguish the most relevant components determining homing flights of displaced pigeons. Conclusions deduced from these experiments, more or less compelling or tentative, are presented in the form of seven theses, supplemented by several subtheses along with reference to empirical data. The principal theses are as follows. (1) Passively displaced pigeons find the way home by using location-dependent signals and not by path integration based on recording of motion. Pigeons are able to home, even from unfamiliar areas, without access to potentially useful information during transport to the release site. (2) Home-related orientation of pigeons in unfamiliar areas requires positional information acquired olfactorily from atmospheric trace gases. Empirically deduced details of olfactory navigation are enumerated (connection with winds and the sun, inaccuracy, spatial range, time course of sampling and memorizing spatial information, etc.). The critical gap in our knowledge, i.e. the nature and spatio-temporal distribution of the substances involved, is provisionally filled by speculation. (3) In familiar areas, known from previous flights, the visual landscape is used additionally to find the way home. (4) Initial orientation of pigeons does not exclusively reflect home-related navigation but includes components independent of the position with respect to home. Observed bearings are co-determined by a general preference for a certain compass direction and by distracting features of the nearby landscape. (5) Proportions among components controlling initial orientation according to theses 2–4 are highly variable depending on local, temporal and experimental conditions and on the life histories of the pigeons. This complexity greatly restricts recognition of the navigationally relevant components of behaviour at a given release site. (6) Sensory inputs, being neither olfactory nor visual, do not substantially contribute to determining the current position with respect to home. This thesis need not be definitive, but at present no contradicting evidence is available. (7) Pigeon homing is a model case of bird homing in general. Experiments with other species support this thesis. So far, there is no reason to assume that wild birds apply mechanisms fundamentally different from those of pigeons to find the way home.
The Debate Over Olfactory Navigation by Homing Pigeons
Authors: Able Kenneth P.
Published: April 2021

In the years since 1971, when Papi and his colleagues first proposed that odors played an important role in the homing navigation of pigeons, the hypothesis has remained controversial. Although the idea seemed intuitively unreasonable to nearly everyone working in the field at that time, empirical support from a wide variety of experiments emanating from Papi’s laboratory in Pisa has stimulated a quarter of a century of experiments, theorizing, advocacy and dissent. The issue is reviewed here in contributions by Hans Wallraff, one of the chief proponents of olfactory navigation, and Roswitha Wiltschko, who remains skeptical about the involvement of odors in pigeon homing. At the Editors’ request, I provide here a personal perspective on the debate from one who has had no involvement in the issue and, indeed, has never released a homing pigeon.
Middle-Scale Navigation: the Vertebrate Case
Authors: Sherry David F.
Published: April 2021

Few ideas have had a greater impact on the study of navigation at the middle scale than the theory of the cognitive map. As papers in this section show, current views of the cognitive map range from complete rejection of the idea (Bennett, 1996) to new proposals for the behavioural and neural bases of the cognitive map (Gallistel and Cramer, 1996; McNaughton et al. 1996). The papers in this section also make it clear that path integration has taken centre stage in theorizing about navigation at the middle scale. Path integration is the use of information generated by locomotion to determine the current distance and direction to the origin of the path. Etienne (1980) provided one of the first experimental demonstrations of path integration by a vertebrate, and in this section Etienne et al. (1996) describe recent research with animals and humans on the interaction between path integration and landmark information. Path integration is also the fundamental means of navigation in the model described by Gallistel and Cramer (1996). McNaughton et al. (1996) suggest that the neural basis of path integration is found in the place cells and head direction cells of the hippocampus and associated brain regions.
Behavioural and Neural Bases of Orientation in Food-Storing Birds
Authors: Sherry David F. , Duff Sarah J.
Published: April 2021

Food-storing birds retrieve hoarded food by remembering the locations of large numbers of spatially dispersed caches. The basic patterns of spatial orientation in these animals have been established in research on two major groups of food-storing birds, chickadees and tits (Paridae), and jays and nutcrackers (Corvidae). Experiments using displacement of landmark arrays show that food-storing birds rely on visual information from nearby landmarks to locate concealed caches. The appearance of the cache sites themselves seems to be relatively unimportant in cache retrieval, perhaps because local features are subject to change during the lifetime of a cache. Under some conditions, food-storing birds use sun-compass information to orient their search for caches, but appear to integrate sun-compass information with landmark information. Lesions of the avian hippocampus disrupt cache retrieval and other spatial tasks in food-storing birds without disrupting the formation of simple associations. Comparative studies show that food-storing birds possess a hippocampus larger than that of non-food-storing birds, probably as an evolutionary consequence of their dependence on spatial orientation for cache retrieval. Experience with cache retrieval plays a role in the development of increased hippocampal size, and there are indications of seasonal variation in hippocampal size in food-storing species.
Homing in Pacific Salmon: Mechanisms and Ecological Basis
Authors: Dittman Andrew H. , Quinn Thomas P.
Published: April 2021

Pacific salmon (Oncorhynchus spp.) are famous for their homing migrations from oceanic feeding grounds to their natal river to spawn. During these migrations, salmon travel through diverse habitats (e.g. oceans, lakes, rivers), each offering distinct orientation clues and, perhaps, requiring distinct sensory capabilities for navigation. Despite these challenges, homing is generally precise and this philopatry has resulted in reproductively isolated spawning populations with specialized adaptations for their natal habitat. This paper reviews the mechanisms underlying all aspects of salmon homing but emphasizes the final, freshwater phase governed by olfactory recognition of homestream water. Prior to their seaward migration, juvenile salmon learn (imprint on) odors associated with their natal site and later, as adults, use these odor memories for homing. Our understanding of this imprinting process is derived primarily from studies using artificial odorants and hatchery-reared salmon. Recent findings suggest, however, that such studies may underestimate the complexity of the imprinting process in nature.
Lophotoxin-Insensitive Nematode Nicotinic Acetylcholine Receptors
Authors: Tornøe Camilla , Holden-Dye Lindy , Garland Catherine , Abramson Stewart N. , Fleming John T. , Sattelle David B.
Published: April 2021

Nematode nicotinic acetylcholine receptors (nAChRs) are molecular targets of several anthelmintic drugs. Studies to date on Caenorhabditis elegans and Ascaris suum have demonstrated atypical pharmacology with respect to nAChR antagonists, including the finding that κ-bungarotoxin is a more effective antagonist than α-bungarotoxin on Ascaris muscle nAChRs. Lophotoxin and its naturally occurring analogue bipinnatin B block all vertebrate and invertebrate nAChRs so far examined. In the present study, the effects on nematode nAChRs of bipinnatin B have been examined. The Ascaris suum muscle cell nAChR was found to be insensitive to 30 μmol l−1 bipinnatin B, a concentration that is highly effective on other nAChRs. To our knowledge, this is the first demonstration of a nAChR that is insensitive to one of the lophotoxins. Xenopus laevis oocytes injected with C. elegans polyadenylated, poly(A)+, mRNA also expressed bipinnatin-B-insensitive levamisole responses, which were, however, blocked by the nAChR antagonist mecamylamine (10 μmol l−1). In contrast to the findings for nematode receptors, bipinnatin B (30 μmol l−1) was effective in blocking mouse muscle nAChRs expressed in Xenopus laevis oocytes and native insect nAChRs. A possible explanation for insensitivity of certain nematode nAChRs to lophotoxins is advanced based on the sequence of an α-like C. elegans nAChR subunit in which tyrosine-190 (numbering based on the Torpedo californica sequence), a residue known to be critical for lophotoxin binding in vertebrate nAChRs, is replaced by a proline residue.
Body Temperatures of Free-Living African Penguins (Spheniscus Demersus) and Bank Cormorants (Phalacrocorax Neglectus)
Authors: Wilson Rory P. , Grémillet David
Published: April 2021

Two free-living seabirds (the African penguin Spheniscus demersus and the bank cormorant Phalacrocorax neglectus) were equipped with stomach temperature-loggers to study body temperature changes during foraging. Body temperature in these endotherms was environmentally and activity-dependent and varied in the case of the cormorant by over 5 °C. Considerations of heat flux show that such flexibility confers considerable energetic advantages: by allowing body temperature to drop when the heat loss to the environment is high, such as in water, birds may save the energy that would normally be necessary to compensate for this drop. It appears that, in cormorants, low body temperature resulting from extended time in water can subsequently be elevated using solar energy when the birds return to land in a manner similar to that of ectotherms. In the better-insulated penguins, muscle-generated heat during swimming is used to re-elevate low body temperature. Continued swimming eventually causes body temperature to rise above normal resting levels so that metabolic rate could theoretically be dramatically reduced immediately post-exercise when the temperature drops to some critical level before any increase in metabolism is necessary to correct it.
Seasonal Dynamics of Dental Sexual Dimorphism in the Atlantic Stingray Dasyatis Sabina
Authors: Kajiura Stephen M. , Tricas Timothy C.
Published: April 2021

Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.
Photoinactivation Of An Identified Motoneurone In The Locust Locusta Migratoria
Authors: Bässler Dagmar , Rathmayer Werner
Published: April 2021

1.The common inhibitory motoneurone 1 (CI1) in the mesothoracic ganglion of the locust was photoinactivated using a helium–cadmium laser or a mercury lamp as light source. Treated animals showed no signs of abnormal locomotory behaviour over periods of up to 40 days.

2.Photoinactivation of part of the neurone in the ganglion, i.e. the soma and the primary neurite, is sufficient to cause irreversible degeneration of all the peripheral extensions of the neurone. Three weeks after photoinactivation, all GABA immunoreactivity had disappeared from the axon branches of the photoinactivated neurone and from their terminals on one of the target muscles investigated, the anterior coxa rotator M92, and inhibitory postsynaptic potentials could no longer be elicited through stimulation. This was taken as proof of functional denervation of the muscle with regard to its inhibitory input. By this time, the axon of CI1 in nerve N3C1, which supplies M92, had also disappeared.

3.Animals treated during the fourth or fifth instars showed a permanent loss of the photoinactivated mesothoracic CI1 neurone after moulting into adulthood.

4.Denervation of M92 in the middle legs of instars and adults by axotomy of N3 always led to rapid functional reinnervation of the muscle. The first sign of reinnervation (excitatory neuromuscular activity upon mechanical stimulation of the tarsi) was detected electrophysiologically as early as 8 days after severing the motor nerve.

5.The eliminination of CI1 by photoinactivation for a period of up to 40 days did not influence parameters of the target muscle, such as size, number of fibres and phenotypes of fibres defined histochemically according to their myofibrillar ATPase isoforms, irrespective of whether the operation was performed in instars or adults. Similarly, the short period of denervation following axotomy before reinnervation took place did not affect the fibre type composition of the muscle.
Short-Range Orientation In Electric Fish: An Experimental Study Of Passive Electrolocation
Authors: Shieh Kwang-Tze , Wilson Willard , Winslow Michael , McBRIDE Don W. , Hopkins Carl D.
Published: April 2021

Gymnotiform electric fish are capable of locating and approaching an electrically discharging conspecific over a range of 1–2 m in a behavior called passive electrolocation. This paper investigates the movements of two species in experiments with approaches to stationary dipoles that are either silenced or jumped to a new direction during an approach.

Gymnotus carapo fail to find an electrode source in trials in which the dipole electrode is switched off in mid-track. They slow their approach, become disoriented and drift away from the target within seconds of the field being switched off. This result suggests that the fish are unable to construct a cognitive map of a dipole source from brief exposure to local electrosensory stimuli.

The second set of trials shows that Brachyhypopomus diazi and Gymnotus carapo bend their body to track electric vectors which are suddenly jumped to a new direction. The latency of the bend response is 0.5 s after the jump. Bending initiates a turn that reduces to zero the error between the fish’s direction and the electric field vector and helps keep the fish aligned with the local electric field vector. Together, these experiments suggest that passive electrolocation is stimulus-bound and that these fish find the electrical sources simply by tracking instantaneous local electric current vectors.
Multiple High-Affinity Binding Sites for [3H]Serotonin in the Brain of a Teleost Fish, the Arctic Charr (Salvelinus Alpinus)
Authors: Winberg Svante , Nilsson Göran E.
Published: April 2021

Binding of [3H]serotonin (5-HT) to membranes prepared from Arctic charr brain homogenates was most consistent with a one-site model for [3H]5-HT binding, with KD and Bmax values of 5.7±0.3 nmol l−1 and 60.7±7.3 fmol mg−1 protein, respectively. Similarly, 5-HT displacement of [3H]5-HT was best explained by a monophasic model with an apparent Ki of 4.3±0.7 nmol l−1. The ability of a number of synthetic 5-HT receptor ligands to displace [3H]5-HT was studied. 8OH-DPAT was found to interact with three [3H]5-HT binding sites, whereas buspirone, TFMPP, spiperone and mianserin all distinguish two sites. In the presence of 300 nmol l−1 buspirone, 8OH-DPAT and mianserin distinguished two [3H]5-HT binding sites, whereas spiperone interacted with only one. Moreover, 8OH-DPAT differentiated three [3H]5-HT binding sites even in the presence of 0.5 mmol l−1 GTP, making it unlikely that these sites represent different affinity states of G-protein-coupled receptors. GTP had no effect on apparent Ki values for 8OH-DPAT, but reduced the Bmax value of the high-affinity site by 60 %. GTP had a similar effect on the saturation binding curve for [3H]5-HT, reducing Bmax by approximately 50 %, whereas KD was unaffected. The results provide evidence for at least three different high-affinity [3H]5-HT binding sites, one of them showing a pharmacological profile strikingly similar to that of the mammalian 5-HT1A receptor.
Regulation of the Asc System and Na+/K+ Pump Activities in Brown Trout (Salmo Trutta) Hepatocytes
Authors: Gallardo M. A. , Pesquero J. , Esteve M. , Canals P. , Sánchez J.
Published: April 2021

The present study investigates the regulation of Na+/K+ pump activity and alanine uptake in trout hepatocytes. Pump activity increased when cells were incubated in an amino-acid-free medium, while it was reduced in cells from fasted animals. Short-term exposure (3 h) to glucagon modified the activity of the pump in a complex seasonally dependent pattern: in experiments carried out in autumn and winter there was some inhibition, while in spring the pump was activated by this hormone.

Pharmacological modification of levels of two intracellular signal transducers, namely cyclic AMP and Ca2+, always led to a reduction in pump activity. These experiments were conducted in May, when activation of the pump by glucagon exposure occurred. There is no apparent explanation for the mechanism by which this hormone modifies the activity of the pump. Glucagon also regulates the activity of system ASC (a Na+-dependent amino acid carrier with short-chain neutral amino acids as preferred substrates). This regulation also showed a seasonally dependent pattern, although the pattern was opposite to that found for the regulation of Na+/K+ pump activity.
Homing Behaviour of Pigeons Subjected to Unilateral Zinc Sulphate Treatment of Their Olfactory Mucosa
Authors: Benvenuti Silvano , Gagliardo Anna
Published: April 2021

Pigeons were made anosmic by unilateral treatment of their olfactory mucosa with a zinc sulphate solution and by plugging the contralateral nostril. In a series of releases at unfamiliar sites, 55–79 km from the home loft, the experimental birds’ homing behaviour was compared with that of two control groups: unmanipulated control birds, and birds subjected to unilateral zinc sulphate treatment and equipped with an ipsilateral nasal plug. The experimental pigeons exhibited homing behaviour – in terms of both homeward initial orientation and homing performance – significantly poorer than that of both unmanipulated and treated control pigeons. In addition, the homing behaviour of the treated controls turned out to be only slightly, and not significantly, poorer than that of the unmanipulated birds. The results show that the impaired homing capabilities of the zinc-sulphate-treated birds are due to the lack of navigational information and not to non-specific brain damage caused by the experimental treatment.
Leucokinin Increases Paracellular Permeability in Insect Malpighian Tubules
Authors: Wang Steven , Rubenfeld Ari B. , Hayes Timothy K. , Beyenbach Klaus W.
Published: April 2021

There are two major transport pathways across epithelia: a transcellular pathway through cells and a paracellular pathway between cells. Previous electrophysiological studies in mosquito Malpighian tubules suggested that the neuropeptide leucokinin-VIII (LK-VIII) increases the chloride permeability of the paracellular pathway. To test the effect of LK-VIII on the paracellular pathway further, we measured transepithelial permeabilities of inulin and sucrose in isolated Malpighian tubules from the mosquito Aedes aegypti. Cell membranes are impermeable to inulin and sucrose, leaving the paracellular pathway as the only route for their transepithelial permeation. LK-VIII (10−6 mol l−1) significantly increased transepithelial permeability to both inulin (by 73.8 %) and sucrose (by 32.4 %) in parallel with a significant increase in rates of transepithelial fluid secretion (by 75–90 %). Cyclic adenosine monophosphate (cyclic AMP, 10−4 mol l−1), which is known to stimulate transcellular transport, also increased rates of transepithelial fluid secretion (by 57–59 %), but it did so without increasing the permeability to sucrose and inulin. Thus, LK-VIII increases the permeability of the paracellular pathway whereas cyclic AMP does not.
Heart and Respiratory Rates and Their Significance for Convective Oxygen Transport Rates in the Smallest Mammal, the Etruscan Shrew Suncus Etruscus
Authors: Jürgens Klaus D. , Fons Roger , Peters Thomas , Sender Susanne
Published: April 2021

Heart and respiratory rates of the smallest mammal (mean adult body mass 2 g), the Etruscan shrew Suncus etruscus, were determined at rest and under stress conditions. Heart rate was obtained from electrocardiograms (ECGs), recorded via foot electrodes. The mean ± S.D. heart rate of resting animals (ambient temperature 22 °C) was 835±107 min−1, the mean maximal rate amounted to 1093±235 min−1. The highest single value recorded was 1511 min−1, which is the highest heart rate reported so far for an endotherm. The respiratory rate was also obtained from ECG recordings, which showed the electrical activity of the breathing muscles during inhalation, and additionally by recording the movements of the thoracic wall with a laser autofocus system. The mean resting respiratory rate was 661±93 min−1, the mean maximal rate was 758±109 min−1 and the highest single value recorded was 894 min−1. At 22 °C, the specific oxygen consumption rate is 67 times higher in resting S. etruscus than in resting humans. Under these conditions, the respiratory rate of the shrew is 47 times higher but the heart rate only 12 times higher than in man. Therefore, to achieve an adequate circulatory oxygen transport rate, the product of relative stroke volume and arterio–venous O2 difference has to be 5.6 times higher in the shrew than in man, whereas for an appropriate ventilatory oxygen transport rate the product of relative tidal volume and oxygen extraction has to be only 1.4 times higher in this small insectivore than in man. The maximal possible oxygen transport rates of the ventilatory and the circulatory system have been estimated and compared with the diffusional transport capacity of the lung. These rates amount to approximately 1000 ml O2 kg−1 min−1. According to our results and data in the literature, an aerobic scope of 7–10 seems to be realistic for the Etruscan shrew.
Transmission Of Vibration Across Honeycombs And Its Detection By Bee Leg Receptors
Authors: Sandeman D. C. , Tautz J. , Lindauer M.
Published: April 2021

Vibration of the rims of open cells in a honeycomb, applied in the plane of the comb face, is transmitted across the comb. Attenuation or amplification of the vibratory signal depends on its frequency and on the type of comb. In general, framed combs, both large and small, strongly attenuate higher frequencies, whereas these are amplified in small open combs. The very poor transmission properties of the large framed combs used in commercial hives may explain the bees’ habit of freeing an area of comb from the frame in those areas used for dancing. Extracellular electrical recordings from the leg of a honeybee detect large action potentials from receptors that monitor extension of the tibia on the femur. Measurements of threshold displacement amplitudes show these receptors to be sensitive to low frequencies. The amplification properties of unframed combs extend the range of these receptor systems to include frequencies that are emitted by the bee during its dance, namely the 15 Hz abdomen waggle and 250 Hz thorax vibration.
Effects Of Ca2+ On Oxidative Phosphorylation In Mitochondria From The Thermogenic Organ Of Marlin
Authors: O’Brien John , Block Barbara A.
Published: April 2021

Mitochondria from the muscle-derived thermogenic (heater) organ and oxidative red muscle of the blue marlin (Makaira nigricans) were studied in order to evaluate aspects of the mechanism of thermogenesis in heater tissue. We investigated whether short-term Ca2+-induced uncoupling of mitochondria contributes to the thermogenic cycle of the heater organ by enhancing the respiration rate. Specific electrodes were used to obtain simultaneous measurements of oxygen consumption and Ca2+ fluxes on isolated mitochondria, and the effects of various concentrations of Ca2+ on respiration rates and the ADP phosphorylated/atomic oxygen consumed (P/O) ratio were examined. Addition of Ca2+ in excess of 10 µmol l−1 to respiring heater organ or red muscle mitochondria partially inhibited state 3 respiration and reduced the P/O ratio, indicating that the mitochondria were partially uncoupled. These effects were blocked by 2 µmol l−1 Ruthenium Red. In heater organ mitochondria, state 3 respiration rate and the P/O ratio were not significantly reduced by 1µmol l−1 free Ca2+, a concentration likely to be near the maximum achieved in a stimulated cell. This indicates that transient increases in cytosolic Ca2+ concentration may not significantly reduce the P/O ratio of heater organ mitochondria. The activity of 2-oxoglutarate dehydrogenase in heater organ mitochondria was stimulated by approximately 15 % by Ca2+ concentrations between 0.2 and 1 µmol l−1. These results suggest that heater organ mitochondria are able to maintain a normal P/O ratio and should maintain ATP output during transient increases in Ca2+ concentration, supporting a model in which an ATP-consuming process drives thermogenesis. Activation of mitochondrial dehydrogenases by low levels of Ca2+ may also enhance respiration and contribute to thermogenesis.
Optomotor Behaviour in Xenopus Laevis Tadpoles as a Measure of the Effect of Gravity on Visual and Vestibular Neural Integration
Authors: Pronych Scott P. , Souza Kenneth A. , Neff Anton W. , Wassersug Richard J.
Published: April 2021

The ability of aquatic vertebrates to maintain their position requires integration of visual and vestibular sensory information. To understand better how aquatic animals integrate such information, we measured the optomotor behaviour of Xenopus laevis tadpoles raised in growth chambers in microgravity (<10−3g), normal gravity (1 g), hypergravity (3 g) and on a slowly rotating clinostat (simulated microgravity). The goal of this research was to determine how development in an altered gravitational force field affects the visual-and vestibular-dependent behaviour of tadpoles. This research represents the first time that the optomotor behaviour of an organism raised from fertilization in microgravity has been tested.

Significant differences were observed in the optomotor behaviour among the four gravity treatments. When first exposed to normal gravity, the microgravity-raised tadpoles exhibited the strongest (or most positive) optomotor behaviour, while the 3 g centrifuge tadpoles showed no optomotor response. Some abnormal behaviours (such as erratic swimming, lying motionless and abnormal swimming posture) were observed in the tadpoles raised in altered gravity on the initial day of testing. One day later, the tadpoles raised in hypergravity did not differ significantly in their optomotor behaviour from control tadpoles raised in normal gravity. However, tadpoles raised in microgravity still displayed an exaggerated optomotor response.

One week after the tadpoles had been introduced to normal gravity, there was no longer a significant difference in optomotor behaviour among the different gravity treatments. This convergence of optomotor behaviour by tadpoles from the different treatments reflects the acclimation of their vestibular systems to normal gravity.
Excretion and Distribution of Ammonia and the Influence of Boundary Layer Acidification in Embryonic Rainbow Trout (Oncorhynchus Mykiss)
Authors: Rahaman-Noronha E. , O’Donnell M. J. , Pilley C. M. , Wright P. A.
Published: April 2021

This study examined ammonia excretion by embryos of the rainbow trout (Oncorhynchus mykiss). The distribution of ammonia in relation to the H+ distribution and electrical potential was determined. The influence of the pH of the unstirred layer (USL) of water next to the external surface of the embryo was also assessed. Eyed-up embryos (35–40 days post-fertilization) were exposed to various external water conditions [pH 6.0, pH 10.0, 1.6 mmol l−1 NaCl, 0.0 mmol l−1 NaCl, 0.2 mmol l−1 NH4Cl, 2.5 mmol l−1 borax buffer (Na2B4O7.10H2O), 2.5 mmol l−1 Hepes, 0.1 mmol l−1 amiloride] for 30 min and ammonia excretion rates, ammonia concentration in the perivitelline fluid (PVF) and yolk, and the pH of the PVF, yolk and USL were measured. The rate of ammonia excretion was dependent, in part, on the partial pressure gradient of NH3 from the PVF to the USL. Exposure to water of pH 6 increased, whereas NH4Cl or pH 10 exposure decreased, ammonia excretion rates. Elevated external Na+ levels also influenced the rate of ammonia excretion, but neither Na+-free water nor amiloride had any effect. The distribution of ammonia between the PVF and USL was dependent on the H+ distribution, but ammonia was distributed according to the electrical potential between the PVF and yolk. The USL was 0.32 pH units more acidic than the bulk water. Addition of buffer to the external water eliminated the acid USL and decreased ammonia excretion rates. We conclude that rainbow trout embryos excrete ammonia primarily as NH3, but when external Na+ levels are elevated, ammonia excretion may be independent of the gradient. The acidic USL next to the chorion probably facilitates NH3 diffusion by maintaining the through the conversion of NH3 to NH4+ upon entry into the USL.
The Respiratory Development of Atlantic Salmon: I. Morphometry of Gills, Yolk Sac and Body Surface
Authors: Wells Patrick R. , Pinder Alan W.
Published: April 2021

During development from larva to juvenile in Atlantic salmon, Salmo salar, there is a change in the anatomical potential for gas exchange among gills, body skin and yolk sac as the larvae resorb yolk, grow and develop gills. Newly hatched Atlantic salmon have poorly developed gills but do have a high skin area to mass ratio and a large well-vascularized yolk sac. Cutaneous surfaces accounted for over 95 % of the total area available for respiration in newly hatched Atlantic salmon (body mass 0.032–0.060 g). The branchial contribution to total area increased rapidly, however, so that by the end of yolk absorption (body mass 0.19–0.23 g) it constituted 22 % of the total area and overtook cutaneous surface area between 5 and 6 g wet body mass. Harmonic mean diffusion distance across the skin increased through development from 20 μm at hatch (14 μm across the yolk sac) to 70 μm in an 11 g fish. Diffusion distances across both the filaments and lamellae of the gills decreased through development, from 3.7 to 2.4 μm for lamellae and from 14.5 to 10.8 μm for filaments.

The total anatomical diffusion factor (ADF, mass-specific surface area per unit diffusion distance) remained constant over early development and appeared to be higher than in adult fish. The distribution of ADF changed over early development from 50 % yolk sac, 42 % body surface and 8 % branchial in newly hatched fish to 68 % branchial and 32 % cutaneous at the end of yolk resorption. Generally, early post-hatch development of gills, ADF and some cutaneous surfaces showed high mass exponents. After yolk resorption (body mass 0.2 g), however, these coefficients were lower and closer to unity. The change in scaling at the end of yolk resorption in this study may reflect the completion of larva to juvenile metamorphosis in Atlantic salmon. Comparison between our data and values in the literature suggests that the timing of gill development is related more to developmental stage than to body size.
Hummingbird Hovering Performance in Hyperoxic Heliox: Effects of Body Mass and Sex
Authors: Chai Peng , Harrykissoon Rajesh , Dudley Robert
Published: April 2021

Owing to their small size and hovering locomotion, hummingbirds are the most aerobically active vertebrate endotherms. Can hyperoxia enhance the flight performance of this highly oxygen-dependent group? Hovering performance of ruby-throated hummingbirds (Archilochus colubris) was manipulated non-invasively using hyperoxic but hypodense gas mixtures of sea-level air combined with heliox containing 35 % O2. This manipulation sheds light on the interplay among metabolic power input, mechanical power output and aerodynamic force production in limiting flight performance. No significant differences in flight mechanics and oxygen consumption were identified between hyperoxic and normoxic conditions. Thus, at least in the present experimental context, hyperoxia did not change the major metabolic and mechanical parameters; O2 diffusive capacities of the respiratory system were probably not limiting to a significant extent. Compared with hummingbirds in our previous studies, the present experimental birds were heavier, had resultant shorter hover-feeding durations and experienced aerodynamic failure at higher air densities. Because hummingbirds have relatively stable wingbeat frequencies, modulation of power output was attained primarily through variation in stroke amplitude up to near 180 °. This result indicates that maximum hovering performance was constrained geometrically and that heavier birds with greater fat loads had less margin for enhancement of power production. Sexual dimorphism in flight adaptation also played a role, with males showing more limited hovering capacities, presumably as a trade-off for increased maneuverability.
Wingbeat Frequency and the Body Drag Anomaly: Wind-Tunnel Observations on a Thrush Nightingale (Luscinia Luscinia) And a Teal (Anas Crecca)
Authors: Pennycuick C. J. , Klaassen Marcel , Kvist Anders , lindström Åke
Published: April 2021

A teal (Anas crecca) and a thrush nightingale (Luscinia luscinia) were trained to fly in the Lund wind tunnel for periods of up to 3 and 16 h respectively. Both birds flew in steady flapping flight, with such regularity that their wingbeat frequencies could be determined by viewing them through a shutter stroboscope. When flying at a constant air speed, the teal’s wingbeat frequency varied with the 0.364 power of the body mass and the thrush nightingale’s varied with the 0.430 power. Both exponents differed from zero, but neither differed from the predicted value (0.5) at the 1 % level of significance. The teal continued to flap steadily as the tunnel tilt angle was varied from —1 ° (climb) to +6 ° (descent), while the wingbeat frequency declined progressively by about 11 %. In both birds, the plot of wingbeat frequency against air speed in level flight was U-shaped, with small but statistically significant curvature. We identified the minima of these curves with the minimum power speed (Vmp) and found that the values predicted for Vmp, using previously published default values for the required variables, were only about two-thirds of the observed minimum-frequency speeds. The discrepancy could be resolved if the body drag coefficients (CDb) of both birds were near 0.08, rather than near 0.40 as previously assumed. The previously published high values for body drag coefficients were derived from wind-tunnel measurements on frozen bird bodies, from which the wings had been removed, and had long been regarded as anomalous, as values below 0.01 are given in the engineering literature for streamlined bodies. We suggest that birds of any size that have well-streamlined bodies can achieve minimum body drag coefficients of around 0.05 if the feet can be fully retracted under the flank feathers. In such birds, field observations of flight speeds may need to be reinterpreted in the light of higher estimates of Vmp. Estimates of the effective lift:drag ratio and range can also be revised upwards. Birds that have large feet or trailing legs may have higher body drag coefficients. The original estimates of around CDb=0.4 could be correct for species, such as pelicans and large herons, that also have prominent heads. We see no evidence for any progressive reduction of body drag coefficient in the Reynolds number range covered by our experiments, that is 21 600–215 000 on the basis of body cross-sectional diameter.
in vivo Length Oscillations of Indirect Flight Muscles in The Fruit Fly Drosophila Virilis
Authors: Chan Wai Pang , Dickinson Michael H.
Published: April 2021

We have used high-speed video microscopy to measure in vivo length oscillations of the indirect flight muscles of the fruit fly Drosophila virilis during tethered flight. The changes in muscle strain were measured by tracking the deformation of the thoracic exoskeleton at the origin and insertion of both the dorsal longitudinal (DLM) and the dorsal ventral (DVM) muscles. The mean peak-to-peak strain amplitudes were found to be 3.5 % for the DLMs and 3.3 % for the DVMs, although the strain amplitude within individual cycles ranged from 2 to 5 %. These values are consistent with the small number of previous measurements of indirect flight muscle strain in other insects, but almost an order of magnitude greater than the strain amplitudes used in most biophysical studies of skinned Drosophila fibers. The results suggest that serial compliance within this sarcomere would need to relieve approximately 70 % of the total strain in order for individual crossbridges to remain attached throughout a complete contraction–extension cycle.
Aerodynamic Characteristics of the Wings and Body of a Dragonfly
Authors: Okamoto Masato , Yasuda Kunio , Azuma Akira
Published: April 2021

The aerodynamic characteristics of the wings and body of a dragonfly and of artificial wing models were studied by conducting two types of wind-tunnel tests and a number of free-flight tests of gliders made using dragonfly wings. The results were consistent between these different tests. The effects of camber, thickness, sharpness of the leading edge and surface roughness on the aerodynamic characteristics of the wings were characterized in the flow field with Reynolds numbers (Re) as low as 103 to 104.
Dynamic Anatomical Study Of Cardiac Shunting In Crocodiles Using High-Resolution Angioscopy
Authors: Axelsson Michael , Franklin Craig E. , Löfman Carl O. , Nilsson Stefan , Grigg Gordon C.
Published: April 2021

Prolonged submergence imposes special demands on the cardiovascular system. Unlike the situation in diving birds and mammals, crocodilians have the ability to shunt blood away from the lungs, despite having an anatomically divided ventricle. This remarkable cardiovascular flexibility is due in part to three anatomical peculiarities: (1) an ‘extra’ aorta (the left aorta) that leaves the right ventricle and allows the blood from the right ventricle to take an alternative route into the systemic circulation instead of going to the lungs; (2) the foramen of Panizza, an aperture that connects the right and left aortas at their base immediately outside the ventricle; and (3) a set of connective tissue outpushings in the pulmonary outflow tract in the right ventricle. Using high-resolution angioscopy, we have studied these structures in the beating crocodile heart and correlated their movements with in vivo pressure and flow recordings. The connective tissue outpushings in the pulmonary outflow tract represent an active mechanism used to restrict blood flow into the lungs, thus creating one of the conditions required for a right-to-left shunt. We observed that the foramen of Panizza was obstructed by the medial cusp of the right aortic valve during most of systole, effectively differentiating the left and right aortic blood pressure. During diastole, however, the foramen remained open, allowing pressure equilibration between the two aortas. Contrary to current theories, we found that the left aortic valves were unable to cover the foramen of Panizza during any part of the cardiac cycle, supporting the reversed foramen flow hypothesis. This would ensure a supply of blood to the coronary and cephalic circulation during a complete shut-down of the left side of the heart, such as might occur during prolonged submergence.
Haemolymph Acid–Base Status, Tracheal gas Levels and the Control of Post-Exercise Ventilation Rate in Grasshoppers
Authors: Krolikowski Katherine , Harrison Jon F.
Published: April 2021

In grasshoppers, ventilation rate increases after jumping, in association with decreases in haemolymph pH and tracheal and increases in haemolymph and tracheal . Are these changes in haemolymph acid–base status or tracheal gas composition causally responsible for the increases in post-locomotion ventilation rate? To answer this question, we manipulated haemolymph acid–base status with injections into the haemocoel and independently manipulated tracheal and with tracheal perfusions. Using a new technique, we continuously monitored ventilation rate and ventilatory pressures on virtually unrestrained insects. Changes in haemolymph acid–base status or tracheal did not affect post-exercise ventilation rate, clearly demonstrating that the ventilatory stimulus associated with locomotion is not dependent on negative feedback from these variables. Post-exercise ventilation rate varied with tracheal , with the lowest ventilation rates observed at the lowest tracheal values, a result opposite to that expected if negative feedback from internal levels were to drive the increase in ventilation rate. Particularly after activity, there was considerable heterogeneity in unperfused animals between tracheal and haemolymph , and between tracheal in the thorax and leg, consistent with unidirectional airflow and a considerable role for diffusion gradients in the gas exchange of grasshoppers.
The Erythrocyte Na+ /H+ Exchangers of Eel (Anguilla Anguilla) and Rainbow Trout (Oncorhynchus Mykiss): a Comparative Study
Authors: Gallardo Romero María , Guizouarn Hélène , Pellissier Bernard , Garcia-Romeu Federico , Motais René
Published: April 2021

Trout and eel red blood cell Na+ /H+ exchangers show widely different regulatory properties. Catecholamines, cyclic AMP and phorbol esters, which activate the trout red cell antiporter, do not affect the eel exchanger. Unlike the trout red cell exchanger, the eel red cell exchanger is strongly activated by cell shrinkage, allowing a remarkable cell volume recovery. These different regulatory properties probably indicate the existence of different isoforms of the exchangers in nucleated erythrocytes, since sensitivity to catecholamines is known to be dependent upon the presence of protein kinase A consensus sites on the cytoplasmic domain of the antiporter.

After shrinkage of eel erythrocytes, the Na+ /H+ exchange rate gradually increases to reach a maximum value after about 10 min. The magnitude of activation is a graded function of cell shrinkage. Deactivation, like activation, is induced by a volume change and occurs after some delay (lag time).

The response of the trout antiporter (βNHE) to cell shrinkage is much reduced compared with that of the eel antiporter. In addition, the antiporter is deactivated prior to restoration of the normal control volume, leaving cell volume regulation notably defective. The trout red cell antiporter, which is desensitized and enters a refractory state following hormonal activation, is only deactivated (it can be reversibly reactivated) after shrinkage-induced activation. This dual control may occur by both phosphorylation-dependent and phosphorylation-independent mechanisms.

In view of the similarities in the regulatory properties of eel and salamander (Amphiuma sp.) Na+ H+ exchangers, the expression of a putative K+ /H+ exchange mediated by the Na+ H+ exchanger was sought in eel erythrocytes. However, neither osmotic swelling nor calyculin-A-dependent phosphorylation revealed such a K+ /H+ exchange.
Respiratory and Cutaneous Evaporative Water Loss at High Environmental Temperatures in a Small Bird
Authors: Wolf Blair O. , Walsberg Glenn E.
Published: April 2021

We measured rates of respiratory and cutaneous evaporative water loss as a function of air temperature in a small desert bird, the verdin Auriparus flaviceps. Birds were placed in a two-compartment metabolic chamber that separately collected water evaporated from the bird’s head and body. Cutaneous and respiratory evaporative water loss, as well as CO2 production, were measured in resting birds at 2 °C intervals between 30 and 50 °C. Metabolic rate was lowest at 38 °C (19 mW g−1 ) and increased to 28 mW g−1 at 50 °C. At the lowest air temperature, 30 °C, resting metabolic rate was 34 mW g−1. As air temperature increased from 30 to 50 °C, cutaneous water loss increased from 3.3 to 10.3 mg g−1 h−1 and respiratory water loss increased from 2.1–64.1 mg g−1 h−1. At moderate air temperatures (30–36 °C), water loss was divided almostevenly between respiratory and cutaneous components. As air temperature increased, however, verdins became heavily dependent on respiratory evaporation for heat dissipation. Evaporative water loss data for other species at high air temperatures suggest that partitioning of water loss may follow two different patterns. Evaporative heat dissipation may depend primarily on either cutaneous or respiratory modes of evaporative heat transfer. The physiological mechanisms and functional significance of these contrasting patterns of evaporative heat loss remain unknown.
Muscle Length Changes During Swimming in Scup: Sonomicrometry Verifies the Anatomical High-Speed Cine Technique
Authors: Coughlin David J. , Valdes Lexia , Rome Lawrence C.
Published: April 2021

Recent attempts to determine how fish muscles are used to power swimming have employed the work loop technique (driving isolated muscles using their in vivo strain and stimulation pattern). These muscle strains have in turn been determined from the anatomical high-speed cine technique. In this study, we used an independent technique, sonomicrometry, to attempt to verify these strain measurements and the conclusions based on them.

We found that the strain records measured from sonomicrometry and the anatomical-cine techniques were very similar. The ratio of the strain measured from sonomicrometry to that from the anatomical-cine technique was remarkably close to unity (1.046±0.013, mean ± S.E.M., N=15, for transducers placed on the muscle surface and corrected for muscle depth, and 0.921±0.028, N=8, in cases where the transducers were inserted to the average depth of the red muscle). These measurements also showed that red muscle shortening occurs simultaneously with local backbone curvature, unlike previous results which suggested that white muscle shortening during the escape response occurs prior to the change in local backbone curvature.