bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Effects of Cold Exposure and Sub-Lethal Intestinal Parasites on Host Morphology and Physiology
Authors: Kristan Deborah M. , Hammond Kimberly A.
Published: April 2021

Multiple, simultaneous demands elicit physiological and morphological responses that may jeopardize an animal’s ability to respond to future challenges, especially when resources are limited. Laboratory mice (Mus musculus) experimentally infected with an intestinal nematode (Heligmosomoides polygyrus) and then exposed to cold showed phenotypic plasticity of morphological and physiological responses. The parasitized mice maintained a similar body mass to the unparasitized mice but had less body fat and showed changes in some organ masses, a greater resting metabolic rate (RMR) and a diminished glucose uptake capacity both at the site of infection and in regions of the small intestine not occupied by parasites. Cold-exposed mice had a greater RMR, less body fat, a greater glucose transport capacity and showed changes in organ masses compared with mice maintained at room temperature. The responses to cold exposure were not affected by parasitism for any dependent variable. The costs of having parasites during simultaneous cold exposure included decreased energy reserves and greater maintenance requirements, which may then decrease the energy available for future expenditures, such as reproduction.
Foraging Energetics and Diving Behavior of Lactating New Zealand Sea Lions,Phocarctos Hookeri
Authors: Costa Daniel P. , Gales Nicholas J.
Published: April 2021

The New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50°30′S, 166°17′E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO2 production) and water turnover were measured using the 18O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0±1.1 % (mean ± S.D.) and mean rate of CO2 production was 0.835±0.114 ml g−1 h−1, which provides an estimated mass-specific field metabolic rate (FMR) of 5.47±0.75 W kg−1. After correction for time on shore, the at-sea FMR was estimated to be 6.65±1.09 W kg−1, a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size.

The mean maximum dive depth was 353±164 m, with a mean diving depth of 124±36 m. The mean maximum dive duration was 8.3±1.7 min, with an average duration of 3.4±0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg).

Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O2 storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.
Reduced Enzymatic Antioxidative Defense in Deep-Sea Fish
Authors: Janssens Bernadette J. , Childress James J. , Baguet Fernand , Rees Jean-Francois
Published: April 2021

Oxygen, while being an obligate fuel for aerobic life, has been shown to be toxic through its deleterious reactive species, which can cause oxidative stress and lead ultimately to cell and organism death. In marine organisms, reactive oxygen species (ROS), such as the superoxide anion and hydrogen peroxide, are generated within respiring cells and tissues and also by photochemical processes in sea water. Considering both the reduced metabolic rate of nektonic organisms thriving in the deep sea and the physico-chemical conditions of this dark, poorly oxygenated environment, the meso- and bathypelagic waters of the oceans might be considered as refuges against oxidative dangers. This hypothesis prompted us to investigate the activities of the three essential enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX) constitutive of the antioxidative arsenal of cells in the tissues of 16 species of meso- and bathypelagic fishes occurring between the surface and a depth of 1300 m. While enzymatic activities were detected in all tissues from all species, the levels of SOD and GPX decreased in parallel with the exponential reduction in the metabolic activity as estimated by citrate synthase activity. In contrast, CAT was affected neither by the metabolic activity nor by the depth of occurrence of the fishes. High levels of metabolic and antioxidative enzymes were detected in the light organs of bioluminescent species. The adjustment of the activity of SOD and GPX to the decreased metabolic activity associated with deep-sea living suggests that these antioxidative defense mechanisms are used primarily against metabolically produced ROS, whereas the maintenance of CAT activity throughout all depths could be indicative of another role. The possible reasons for the occurrence of such a reduced antioxidative arsenal in deep-sea species are discussed.
Gliding Flight: Drag and Torque of a Hawk and a Falcon With Straight and Turned Heads, and a Lower Value For The Parasite Drag Coefficient
Authors: Tucker Vance A.
Published: April 2021

Raptors – falcons, hawks and eagles in this study – such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 ° to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s−1. With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct.

The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor’s higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals.

In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (CD,par) of 0.18 previously used for calculating the gliding performance of a peregrine.

The accuracy with which drag coefficients measured on wingless bird bodies in a wind tunnel represent the CD,par of a living bird is unknown. Another method for determining CD,par selects values that improve the fit between speeds predicted by mathematical models and those observed in living birds. This method yields lower values for CD,par (0.05–0.07) than wind tunnel measurements, and the present study suggests a value of 0.1 for raptors as a compromise.
The Deep Fovea, Sideways Vision and Spiral Flight Paths in Raptors
Authors: Tucker Vance A.
Published: April 2021

Raptors – falcons, hawks and eagles in this study – have two regions of the retina in each eye that are specialized for acute vision: the deep fovea and the shallow fovea. The line of sight of the deep fovea points forwards and approximately 45 ° to the right or left of the head axis, while that of the shallow fovea also points forwards but approximately 15 ° to the right or left of the head axis. The anatomy of the foveae suggests that the deep fovea has the higher acuity.

Several species of raptors in this study repeatedly moved their heads among three positions while looking at an object: straight, with the head axis pointing towards the object; or sideways to the right or left, with the head axis pointing approximately 40 ° to the side of the object. Since raptors do not rotate their eyes noticeably in the sockets, these movements presumably cause the image of the object to fall on the shallow and deep foveae. The movements occurred approximately every 2 s on average in hawks and falcons, and approximately every 5 s in bald eagles.

The proportion of time that the raptors spent looking straight or sideways at an object depended on how far away the object was. At a distances closer than 8 m, they spent more time looking at the object straight, but as the distance increased to 21 m, they spent more time looking at it sideways. At distances of 40 m or more, raptors looked sideways at the object 80 % or more of the time. This dependence of head position on distance suggests that raptors use their more acute sideways vision to look at distant objects and sacrifice acuity for stereoscopic binocular vision to look at close objects.

Having their most acute vision towards the side causes a conflict in raptors such as falcons, which dive at prey from great distances at high speeds: at a speed of 70 m s−1, turning their head sideways to view the prey straight ahead with high visual acuity may increase aerodynamic drag by a factor of 2 or more and slow the raptor down. Raptors could resolve this conflict by diving along a logarithmic spiral path with their head straight and one eye looking sideways at the prey, rather than following the straight path to the prey with their head turned sideways. Although the spiral path is longer than the straight path, a mathematical model for an ‘ideal falcon’ shows that the falcon could reach the prey more quickly along the spiral path because the speed advantage of a straight head more than compensates for the longer path.
Mass, Temperature and Metabolic Effects on Discontinuous Gas Exchange Cycles in Eucalyptus-Boring Beetles (Coleoptera: Cerambycidae)
Authors: Chappell Mark A. , Rogowitz Gordon L.
Published: April 2021

Ventilatory accommodation of changing metabolic rates is a relatively little-studied aspect of the discontinuous gas exchange cycles (DGCs) that occur in a wide variety of terrestrial arthropods. We used correlation analysis of resting metabolic rate (RMR, measured as the rate of CO2 emission; ) and several components of the DGC to examine accommodation to both temperature-induced changes and individual variation in RMR in two wood-boring beetles (Phorocantha recurva and P. semipunctata; Coleoptera: Cerambycidae).

At low to moderate ambient temperatures (Ta; 10–20 °C), Phorocantha spp. displayed a characteristic DGC with relatively brief but pronounced open (O) phase bursts of CO2 emission separated by longer periods of low , the flutter (F) phase. However, the never fell to zero, and we could not reliably differentiate a typical closed (C) phase from the F phase. Accordingly, we pooled the C and F phases for analysis as the C+F phase. At higher Ta (30 °C), the duration of the combined C+F phase was greatly reduced. There were no differences between the two species or between males and females in either RMR or characteristics of the DGC. We found large variation in the major DGC components (cycle frequency, durations and emission volumes of the O and C+F phases); much of this variation was significantly repeatable. Accommodation of temperature-induced RMR changes was almost entirely due to changes in frequency (primarily in the C+F phase), as has been found in several other discontinuously ventilating arthropods. Frequency changes also contributed to accommodation at constant Ta, but modulation of emission volumes (during both O and C+F phases) played a larger role in this case.

The DGC is often viewed as a water conservation mechanism, on the basis that respiratory evaporation is minimal during the C and F phases. This hypothesis assumes that the F phase is primarily convective (because of a reduction in tracheal and total intratracheal pressure during the C phase). To test this, we measured the DGC in beetles subjected to varying degrees of hypoxia in addition to normoxia. As predicted for a largely diffusive F phase, we found an increase in the volume of CO2 emitted during the C+F phase in hypoxic conditions (10.4 % oxygen). This finding, together with a reduced tendency to utilize a DGC at high Ta (when water stress is greatest) and a natural history in which water availability is probably not limiting for any life stage, suggests that a reduction of respiratory evaporation may not have been critical in the evolution of the DGC of Phorocantha spp. Instead, selection may have favored discontinuous ventilation because it facilitates gas exchange in the hypercapnic and hypoxic environments commonly encountered by animals (such as Phorocantha spp.) that live in confined spaces.
Olfactory Sensitivity to Changes In Environmental [Ca2+] in The Marine Teleost Sparus Aurata
Authors: Hubbard P. C. , Barata E. N. , Canario A. V. M.
Published: April 2021

Estuarine and/or migratory teleosts may experience large and rapid changes in external [Ca2+]. Previous studies have largely centred on the physiological mechanisms that maintain a constant plasma [Ca2+] in the face of such external fluctuations, but little work has been directed to examining how these changes may originally be detected. We present evidence that the olfactory system of the gilthead seabream (Sparus aurata) is highly sensitive to reductions in environmental [Ca2+] and suggest a possible mechanism by which this may be mediated. Multi-unit extracellular recordings were made from the olfactory nerve of Sparus aurata while the [Ca2+] of artificial sea water flowing over the olfactory epithelium was varied from 10 to 0 mmol l−1. Reductions in [Ca2+] caused a large, non-accommodating increase in the firing rate of the olfactory nerve (apparent IC50=1.67±0.26 mmol l−1, apparent Hill coefficient=−1.22±0.14; means ± S.E.M., N=6). This response was not due to the concomitant reduction in osmolality and was specific for Ca2+. During continuous exposure of the olfactory epithelium to Ca2+-free sea water, the apparent IC50 and Hill coefficient in response to increases in [Ca2+] were 0.48±0.14 mmol l−1 and −0.76±0.16 (means ± S.E.M., N=6), respectively, suggesting an adaptation of the Ca2+-sensing system to low-[Ca2+] environments. Ca2+ is intimately involved in signal transduction in the olfactory receptor neurones, but our data support a true olfactory response, rather than a non-specific effect to lowering of external [Ca2+]. The absence of Ca2+ from sea water only partially and temporarily blunted the olfactory response to the odorant L-serine; the response amplitude recovered to control levels within 20 min. This suggests that the olfactory system in general is able to adapt to low-[Ca2+] environments. We suggest that the Ca2+ sensitivity is mediated by an extracellular Ca2+-sensing receptor similar to the recently characterized mammalian Ca2+-sensing receptor.
Interruption of Cardiac Output Does Not Affect Short-Term Growth and Metabolic Rate in day 3 And 4 Chick Embryos
Authors: Burggren Warren W. , Warburton Stephen J. , Slivkoff Mark D.
Published: April 2021

The heart beat of vertebrate embryos has been assumed to begin when convective bulk transport by blood takes over from transport by simple diffusion. To test this hypothesis, we measured eye grow.th, cervical flexure and rates of oxygen consumption in day 3–4 chick embryos denied cardiac output by ligation of the outflow tract and compared them with those of embryos with an intact cardiovascular system.

Eye diameter, used as the index for embryonic growth, increased at a rate of approximately 4.5–5 % h−1 during the observation period. There was no significant difference (P>0.1) in the rate of increase in eye diameter between control (egg opened), sham-ligated (ligature present but not tied) and ligated embryos. Similarly, the normal progression of cervical flexure was not significantly altered by ligation (P>0.1).

(ml O2 g−1 h−1) at 38 °C, measured by closed respirometry, was not significantly different (P>0.1) on day 3 in sham-ligated (14.5±1.9 ml O2 g−1 h−1) and ligated 17.6±1.8 ml O2 g−1 h−1) embryos. Similarly, on day 4, in sham-ligated and ligated embryos was statistically the same (sham-ligated 10.5±2.9 ml O2 g−1 h−1; ligated 9.7±2.9 ml O2 g−1 h−1). Expressed as a linear function of body mass (M), in sham-ligated embryos was described by the equat.ion , while in ligated embryos was described by the equation . The regression line describing the relationship between body mass and for pooled sham-ligated and ligated embryos (the two populations being statistically identical) was . The slope of this regression line, which was significantly different from zero (r2=0.30, N=34, P<0.01), was similar to slopes calculated from previous studies over the same range of body mass.

Collectively, these data indicate that growth and are not dependent upon cardiac output and the convective blood flow it generates. Thus, early chick embryos join those of the zebrafish, clawed frog and axolotl in developing a heart beat and blood flow hours or days before required for convective oxygen and nutrient transport. We speculate that angiogenesis is the most likely role for the early development of a heart beat in vertebrate embryos.
Octopamine Reverses the Isolation-Induced Increase in Trophallaxis in the Carpenter ant Camponotus Fellah
Authors: Boulay R. , Soroker V. , Godzinska E. J. , Hefetz A. , Lenoir A.
Published: April 2021

Social deprivation is an unusual situation for ants that normally maintain continuous contact with their nestmates. When a worker was experimentally isolated for 5 days and then reunited with a nestmate, she engaged in prolonged trophallaxis. It is suggested that trophallaxis allows her to restore a social bond with her nestmates and to re-integrate into the colony, particularly via the exchange of colony-specific hydrocarbons. Octopamine reduced trophallaxis in these workers as well as hydrocarbon transfer between nestmates, but not hydrocarbon biosynthesis. Administration of serotonin to such 5-day-isolated ants had no effect on the percentage of trophallaxis. Administration of phentolamine alone, an octopamine antagonist, had no effect, but when co-administrated with octopamine it reduced the effect of octopamine alone and restored trophallaxis to control levels. Moreover, the observed effect of octopamine was not due to a non-specific effect on locomotor activity. Therefore, we hypothesise that octopamine mediates behaviour patterns linked to social bonding, such as trophallaxis. On the basis of an analogy with the role of norepinephrine in vertebrates, we suggest that the levels of octopamine in the brain of socially deprived ants may decrease, together with a concomitant increase in their urge to perform trophallaxis and to experience social contacts. Octopamine administration may reduce this social deprivation effect, and octopamine could therefore be regarded as being partly responsible for the social cohesion between nestmates in ant colonies.
Temperature-Induced Pupil Movements in Insect Superposition Eyes
Authors: Nordström Peter , Warrant Eric J.
Published: April 2021

In this paper, we describe the hitherto largely overlooked effect of temperature on the pupil of insect compound eyes. In the turnip moth Agrotis segetum and in two other nocturnal insects with superposition eyes, the lacewing Euroleon nostras and the codling moth Cydia pomonella, the pupil not only opens and closes with changes in the ambient light level, as expected, but also with changes in temperature in the absence of light. In complete darkness, the pupil of A. segetum responds over a wide range of temperatures, with the pupillary pigments migrating to a light-adapted position when the animal is exposed to either low or high temperatures. At temperatures between 21.0 and 22.7 °C, the pigments migrate to the fully dark-adapted position, resulting in an open pupil and maximal eye glow. Pupil closure at high temperatures shows two distinct thresholds: the first at 23.8±0.7 °C and a second some degrees higher at 25.7±1.2 °C (means ± S.D., N=10).

Temperatures exceeding the first threshold (the activation temperature, Ta) initiate a closure of the pupil that is completed when the temperature exceeds the second threshold (the closure temperature, Tc), which causes rapid and complete migration of pigment to the light-adapted position. All temperatures above Ta affect the pupil, but only temperatures exceeding Tc result in complete closure. Temperatures between Ta and Tc cause a slow, partial and rather unpredictable closure. The lacewing and the codling moth both show very similar responses to those of A. segetum, suggesting that this response to temperature is widespread in superposition eyes. The possibility that the ambient temperature could be used to pre-adapt the eye to different light intensities is discussed.
Transcriptional control of Ca2+-activated K+ channel expression: identification of a second, evolutionarily conserved, neuronal promoter
Authors: Bohm Rudolf A. , Wang Bin , Brenner Robert , Atkinson Nigel S.
Published: April 2021

Neuronal signaling properties are largely determined by the quantity and combination of ion channels expressed. The Drosophila slowpoke gene encodes a Ca2+-activated K+ channel used throughout the nervous system. The slowpoke transcriptional control region is large and complex. To simplify the search for sequences responsible for tissue-specific expression, we relied on evolutionary conservation of functionally important sequences. A number of conserved segments were found between two Drosophila species. One led us to a new 5′ exon and a new transcriptional promoter: Promoter C0. In larvae and adults, Promoter C0 was demonstrated to be neural-specific using flies transformed with reporter genes that either contain or lack the promoter. The transcription start site of Promoter C0 was mapped, and the exon it appends to the 5′ end of the mRNA was sequenced. This is the second neural-specific slowpoke promoter to be identified, the first being Promoter C1. Promoter choice does not alter the encoded polypeptide sequence. RNAase protection assays indicate that Promoter C0 transcripts are approximately 12 times more abundant that Promoter C1 transcripts. Taken together, these facts suggest that promoter choice may be a means for cells to control channel density.
The Molecular Biology of Invertebrate Voltage-Gated Ca2+ Channels
Authors: Jeziorski Michael C. , Greenberg Robert M. , Anderson Peter A. V.
Published: April 2021

The importance of voltage-gated Ca2+ channels in cellular function is illustrated by the many distinct types of Ca2+ currents found in vertebrate tissues, a variety that is generated in part by numerous genes encoding Ca2+ channel subunits. The degree to which this genetic diversity is shared by invertebrates has only recently become apparent. Cloning of Ca2+ channel subunits from various invertebrate species, combined with the wealth of information from the Caenorhabditis elegans genome, has clarified the organization and evolution of metazoan Ca2+ channel genes. Functional studies have employed novel structural information gained from invertebrate Ca2+ channels to complement ongoing research on mammalian Ca2+ currents, while demonstrating that the strict correspondence between pharmacological and molecular classes of vertebrate Ca2+ channels does not fully extend to invertebrate tissues. Molecular structures can now be combined with physiological data to develop a more cogent system of categorizing invertebrate channel subtypes. In this review, we examine recent progress in the characterization of invertebrate Ca2+ channel genes and its relevance to the diversity of invertebrate Ca2+ currents.
Responsiveness of Olfactory Neurons to Distinct Aliphatic Aldehydes
Authors: Kaluza Jan F. , Breer Heinz
Published: April 2021

The responsiveness of isolated olfactory sensory neurons to stimulation with aliphatic aldehydes of varying chain length (5–10 hydrogenated carbon atoms) was investigated by means of Ca2+ imaging. More than half the cells examined were responsive to aliphatic aldehydes. Individual cells did not react or reacted to one or multiple aldehydes; in the latter case, cells only reacted to aldehydes of consecutive carbon chain lengths. The largest proportion of cells responded to octanal. It was also demonstrated that a structural difference as small as one hydrogenated carbon atom was detectable by the olfactory neurons.

Neurons were increasingly able to discriminate between two aldehydes as the difference in chain length between the two increased. Discrimination between aldehydes with longer carbon chains was reduced. Although the odorants examined belong to a distinct chemical class and differ only slightly in structure, individual olfactory sensory neurons showed quite different receptive properties.
Heat Shock-Induced Thermoprotection of Hindleg Motor Control in the Locust
Authors: Barclay J. W. , Robertson R. M.
Published: April 2021

Functional neuromuscular connections are critical for appropriate behavioural responses, but can be negatively affected by increases in temperature. We investigated the effects of heat shock on the thermosensitivity of a neuromuscular pathway to the hindleg tibial extensor muscle of Locusta migratoria. We found that exposure to heat shock induced thermoprotection of both neuromuscular transmission and extensor muscle contraction by (i) increasing the upper temperature limit for failure, (ii) improving recovery following heat-induced failure and (iii) stabilizing excitatory junction potential amplitude and duration and extensor muscle contraction force at high temperatures. Furthermore, the heat-shock-induced thermoprotection of extensor muscle contraction was not attributable to a protective effect on intrinsic components of muscle contraction. Finally, the use of jumping as a locomotor strategy to avoid capture, a behavioural response dependent upon functionally competent neuromuscular connections at the hindleg tibial extensor muscle, became less sensitive to temperature following heat shock. We conclude that the natural stress response of the locust stabilizes neuromuscular signalling during temperature stress, and that this can underlie a thermoprotection of muscle contraction force and thus alter the thermosensitivity of an escape behaviour critical for survival.
Thermotolerant Desert Lizards Characteristically Differ in Terms of Heat-Shock System Regulation
Authors: Zatsepina O. G. , Ulmasov KH. A. , Beresten S. F. , Molodtsov V. B. , Rybtsov S. A. , Evgen’EV M. B.
Published: April 2021

We compare the properties and activation of heat-shock transcription factor (HSF1) and the synthesis of a major family of heat-shock proteins (HSP70) in lizard species inhabiting ecological niches with strikingly different thermal parameters. Under normal non-heat-shock conditions, all desert-dwelling lizard species studied so far differ from a northern, non-desert species (Lacerta vivipara) in the electrophoretic mobility and content of proteins constitutively bound to the regulatory heat-shock elements in the heat-shock gene promoter. Under these conditions, levels of activated HSF1 and of both HSP70 mRNA and protein are higher in the desert species than in the non-desert species. Upon heat shock, HSF1 aggregates in all species studied, although in desert species HSF1 subsequently disaggregates more rapidly. Cells of the northern species have a lower thermal threshold for HSP expression than those of the desert species, which correlates with the relatively low constitutive level of HSPs and high basal content of HSF1 in their cells.
The Effects of Cell Ageing on Metabolism in Rainbow Trout (Oncorhynchus Mykiss) Red Blood Cells
Authors: Phillips M. C. L. , Moyes C. D. , Tufts B. L.
Published: April 2021

The effects of cell age on metabolism in the nucleated red blood cells of rainbow trout (Oncorhynchus mykiss) were examined. Red blood cells were separated according to age using fixed-angle centrifugation. The mean erythrocyte haemoglobin concentration in old red blood cells was found to be 120 % of that in young red blood cells. In young red blood cells, the activities of the mitochondrial enzymes citrate synthase and cytochrome oxidase were 135–200 %, respectively, of those measured in old red blood cells. The activity of the glycolytic enzyme lactate dehydrogenase in young red blood cells was 170 % of that in old red blood cells, whereas the activity of the glycolytic enzyme pyruvate kinase was not significantly affected by cell age. In addition, young red blood cells consumed over twice as much O2 and devoted 50 % more O2 to protein synthesis and the activity of Na+/K+-ATPase than old red blood cells. Red blood cell age did not significantly affect the rate of lactate production. This study shows that ageing in rainbow trout nucleated red blood cells is accompanied by a significant decline in aerobic energy production and the processes it supports, as well as a corresponding increase in the glycolytic contribution to metabolism.
Analysis of the Three-Dimensional Trajectories of Organisms: Estimates of Velocity, Curvature and Torsion From Positional Information
Authors: Crenshaw Hugh C. , Ciampaglio Charles N. , Mchenry Matthew
Published: April 2021

Most biological motions are three-dimensional. This includes the trajectories of whole organisms and of their appendages. While recordings of three-dimensional trajectories are sometimes published, quantitative analysis of these trajectories is uncommon, primarily because there are no standard techniques or conventions in biology for the analysis of three-dimensional trajectories. This paper describes a new technique, finite helix fit (FHF), based on the geometry of three-dimensional curves, whereby a three-dimensional trajectory is completely described by its velocity, curvature and torsion. FHF estimates these parameters from discretely sampled points on a trajectory (i.e. from positional data such as x,y,z coordinates). Other measures of motion can be derived from these parameters, such as the translational and rotational (or angular) velocities of an organism. The performance of the algorithms is demonstrated using simulated trajectories and trajectories of freely swimming organisms (a flagellate, Chlamydomonas reinhardtii; a ciliate, Paramecium tetraurelia; spermatozoa of a sea urchin, Arbacia punctulata; larvae of an ascidian, Botrylloides sp.).
Lack of Effect of Ageing on Acetate Oxidation in Rat Skeletal Muscle During Starvation: A 13C NMR Study
Authors: Mezzarobba V. , Bielicki G. , Jeffrey F. M. H. , Mignon M. , Renou J. P. , Grizard J. , Meynial-Denis D.
Published: April 2021

Acetate oxidation was examined by 13C nuclear magnetic resonance in skeletal muscle from adult and old rats. Rats fasted for 5 days were perfused with [2-13C]acetate over 2 h, and muscle extracts were analyzed for [13C]glutamate isotopomers. This study shows that approximately 80 % of acetyl-coenzyme A entering the tricarboxylic cycle was derived from substrate infusion in both adult and old rats, and that the flux through anaplerotic pathways was approximately 21 % of the flux through citrate synthase. These data demonstrate that skeletal muscle from adult and old rats oxidizes the same proportion of exogenous acetate.
Lateral Optic Flow Does Not Influence Distance Estimation in the Desert Ant Cataglyphis Fortis
Authors: Ronacher B. , Gallizzi K. , Wohlgemuth S. , Wehner R.
Published: April 2021

The present account answers the question of whether desert ants (Cataglyphis fortis) gauge the distance they have travelled by using self-induced lateral optic-flow parameters, as has been described for bees. The ants were trained to run to a distant food source within a channel whose walls were covered with black-and-white gratings. From the food source, they were transferred to test channels of double or half the training width, and the distance they travelled before searching for home and their walking speeds were recorded. Since the animals experience different motion parallax cues when walking in the broader or narrower channels, the optic-flow hypothesis predicted that the ants would walk faster and further in the broader channels, but more slowly and less far in the narrower channels. In contrast to this expectation, neither the walking speeds nor the searching distances depended on the width or height of the channels or on the pattern wavelengths. Even when ventral-field visual cues were excluded by covering the eyes with light-tight paint, the ants were not influenced by lateral optic flow-field cues. Hence, walking desert ants do not depend on self-induced visual flow-field cues in gauging the distance they have travelled, as do flying honeybees, but can measure locomotor distance exclusively by idiothetic means.
Active Osmoregulatory Ion Uptake Across the Pleopods of the Isopod Idotea Baltica (Pallas): Electrophysiological Measurements on Isolated Split Endo- and Exopodites Mounted in a Micro-Ussing Chamber
Authors: Postel Ute , Becker Wilhelm , Brandt Angelika , Luck-Kopp Susanne , Riestenpatt Sven , Weihrauch Dirk , Siebers Dietrich
Published: April 2021

The mechanism of active, osmoregulatory ion uptake was investigated in the pleopods of the marine isopod Idotea baltica (Pallas). Using isolated split half-podites of isopods acclimated to brackish water (20 ‰ salinity) mounted in a micro-Ussing chamber and symmetrically superfused with identical haemolymph-like salines, a mean short-circuit current Isc of −445 µA cm−2 was measured in endopodites 3–5, corresponding to an inwardly directed transcellular movement of negative charge. Application of ouabain (5 mmol l−1) to the basolateral superfusate resulted in the almost total abolition of the Isc (reduced from −531 to −47 µA cm−2), suggesting that the Na+/K+-ATPase is the driving force for active, electrogenic uptake of NaCl. In contrast, mean Isc values close to zero were found in preparations of all exopodites and in endopodites 1 and 2. The specific activities of Na+/K+-ATPase corresponded with these results. Specific activities were highest in posterior endopodites 3–5 and depended on ambient salinity. In all other rami, the activities were much lower and independent of ambient salinity. Activities in posterior endopodites 3–5 were lowest in isopods acclimated to 30 ‰ salinity (2–4 µmol Pi mg−1 protein h−1), increased in individuals kept in 20 ‰ salinity (8.4 µmol Pi mg−1 protein h−1) and were highest in isopods acclimated to 15 ‰ salinity (18.2 µmol Pi mg−1 protein h−1). When specimens were transferred from 30 to 40 ‰ salinity, Na+/K+-ATPase activity increased in the posterior endopodites. The electrophysiological and Na+/K+-ATPase activity measurements show that active electrogenic ion transport in this species occurs almost exclusively in posterior endopodites 3–5. The endopodite of the fifth pleopod of I. baltica exhibited a microscopic structure remarkably similar to that described for the lamellae of the phyllobranchiae of brachyurans. It is composed of two opposed epithelial monolayers of ionocytes, each covered by cuticle. Bundles of pillar cells are located within the ionocyte layers, which are separated by a fenestrated lamellar septum of connective tissue. The results obtained in this study indicate that endopodites 3–5 play the main role in osmoregulatory ion uptake of the isopod I. baltica. Moreover, the Na+/K+-ATPase is the only driving force behind active electrogenic ion uptake across the epithelial cells.
Insulin and Igf-I Receptors in Trout Adipose Tissue are Physiologically Regulated by Circulating Hormone Levels
Authors: Planas Josep V. , Méndez Eva , Baños Núria , Capilla Encarnación , Navarro Isabel , Gutiérrez Joaquim
Published: April 2021

In fish, insulin is believed to act on adipose tissue to promote lipid accumulation, but a direct role for insulin in fish adipose tissue lipogenesis has yet to be demonstrated. To investigate the role of insulin and insulin-like growth factor I (IGF-I) in fish adipose tissue function, we have investigated the presence and the regulation of insulin and IGF-I receptors in adipose tissue of brown trout (Salmo trutta). Receptors for insulin and IGF-I were detected in trout adipose tissue, with IGF-I receptors being more abundant (two- to tenfold) and having a higher affinity (twofold) than insulin receptors. In contrast to the situation in mammals, arginine treatment, which elevates the levels of insulin and IGF-I in plasma, increased the number of insulin receptors 1.7-fold and the number of IGF-I receptors 2.3-fold. When plasma levels of insulin and IGF-I were decreased by fasting, insulin receptor numbers fell 3.6-fold and IGF-I receptor numbers fell 2.2-fold. These results demonstrate for the first time the presence of specific insulin and IGF-I receptors in adipose tissue of ectothermic vertebrates and suggest that adipose tissue may be a target for the actions of insulin and IGF-I in fish.
Heat Production and Oxygen Consumption During Metabolic Recovery of White Muscle Fibres from the Dogfish Scyliorhinus Canicula
Authors: Lou F. , Laarse W. J. Van Der , Curtin N. A. , Woledge R. C.
Published: April 2021

Oxygen consumption and heat production were measured during contraction and recovery of isolated, white muscle fibres from dogfish (Scyliorhinus canicula) at 19 °C. The contraction period consisted of 20 isometric twitches at 3 Hz; this was followed by a recovery period of 2 h without stimulation.

We tested the hypothesis that recovery is wholly oxidative (not glycolytic) in these fibres. The following features support this hypothesis. (i) The ratio of total heat produced to oxygen consumed, 451±34 kJ mol−1 (mean ± S.E.M., N=29), was close to that expected for either the oxidation of carbohydrate, 473 kJ mol−1, or the oxidation of fat, 439 kJ mol−1. Even assuming the maximum value (95 % confidence limit) of the observed heat production, glycolysis could account for resynthesis of at most 18 % of the ATP used during the contractions. (ii) When the difference in rates of diffusion of oxygen and heat within the muscle are taken into account, the time courses of oxygen consumption and heat production match each other well during the entire recovery period.

The efficiency of recovery (=energy used for ATP synthesis/energy available for ATP synthesis) was estimated from the results. This value, 84.0±20.1 % (mean ± S.E.M., N=29), is relatively high and represents the first such measurement in functioning muscle.
Branchial Receptors and Cardiorespiratory Reflexes in A Neotropical Fish, The Tambaqui (Colossoma Macropomum)
Authors: Sundin Lena , Reid Stephen G. , Rantin F. Tadeu , Milsom William K.
Published: April 2021

This study examined the location and physiological roles of branchial chemoreceptors involved in the cardiorespiratory responses to hypoxia and hypercarbia in a neotropical fish that exhibits aquatic surface respiration, the tambaqui (Colossoma macropomum). Fish were exposed to abrupt progressive environmental hypoxia (18.6–1.3 kPa water ) and hypercarbia (water equilibrated with 5 % CO2 in air, which lowered the water pH from 7.0 to 5.0). They were also subjected to injections of NaCN into the ventral aorta (to stimulate receptors monitoring the blood) and buccal cavity (to stimulate receptors monitoring the respiratory water). All tests were performed before and after selective denervation of branchial branches of cranial nerves IX and X to the gill arches. The data suggest that the O2 receptors eliciting reflex bradycardia and increases in breathing frequency are situated on all gill arches and sense changes in both the blood and respiratory water and that the O2 receptors triggering the elevation in systemic vascular resistance, breathing amplitude, swelling of the inferior lip and that induce aquatic surface respiration during hypoxia are extrabranchial, although branchial receptors also contribute to the latter two responses. Hypercarbia also produced bradycardia and increases in breathing frequency, as well as hypertension, and, while the data suggest that there may be receptors uniquely sensitive to changes in CO2/pH involved in cardiorespiratory control, this is based on quantitative rather than qualitative differences in receptor responses. These data reveal yet another novel combination for the distribution of cardiorespiratory chemoreceptors in fish from which teleologically satisfying trends have yet to emerge.
The Effects of Temperature on the Burial Performance and Axial Motor Pattern of the Sand-Swimming of the Mojave Fringe-Toed Lizard Uma Scoparia
Authors: Jayne Bruce C. , Daggy Matthew W.
Published: April 2021

Although lateral axial bending is widespread for the locomotion of ectothermic vertebrates, the axial motor patterns of terrestrial taxa are known only for a limited number of species and behaviors. Furthermore, the extent to which the trunk and tail of ectothermic tetrapods have similar motor patterns is poorly documented. We therefore recorded the activity of the epaxial muscles in the trunk and tail of sand-swimming Mojave fringe-toed lizards (Uma scoparia) to determine whether this specialized behavior has features of the motor pattern that differ from those of diverse ectothermic vertebrates. Muscle activity during initial sand-swimming was a standing-wave pattern in the trunk and tail. Next, the hind limbs moved alternately and the caudofemoralis muscles and nearby axial muscle in the trunk and tail had similar long-duration electromyographic bursts, whereas the anterior trunk had shorter, more frequent electromyographic bursts. The final tail burial involved a traveling wave of posteriorly propagated axial muscle activity within localized regions of the tail. With increased temperature (from 22 to 40 °C), the mean frequencies of axial oscillations increased from approximately 7 to 21 Hz, and the greatest value (33 Hz) was nearly twice the maximal limb cycling frequency during running. The mean burial time at the lowest temperature (3.8 s) was nearly twice that for a 10 °C higher temperature. For the axial electromyograms, a decrease in temperature of 18 °C more than doubled the electromyographic and cycle durations, whereas the duty factors and intersegmental phase lags changed only slightly with temperature.
Oxygen-Sensitive Membrane Transporters in Vertebrate Red Cells
Authors: Gibson J. S. , Cossins A. R. , Ellory J. C.
Published: April 2021

Oxygen is essential for all higher forms of animal life. It is required for oxidative phosphorylation, which forms the bulk of the energy supply of most animals. In many vertebrates, transport of O2 from respiratory to other tissues, and of CO2in the opposite direction, involves red cells. These are highly specialised, adapted for their respiratory function. Intracellular haemoglobin, carbonic anhydrase and the membrane anion exchanger (AE1) increase the effective O2- and CO2-carrying capacity of red cells by approximately 100-fold. O2 also has a pathological role. It is a very reactive species chemically, and oxidation, free radical generation and peroxide formation can be major hazards. Cells that come into contact with potentially damaging levels of O2have a variety of systems to protect them against oxidative damage. Those in red cells include catalase, superoxide dismutase and glutathione. In this review, we focus on a third role of O2, as a regulator of membrane transport systems, a role with important consequences for the homeostasis of the red cell and also the organism as a whole. We show that regulation of red cell transporters by O2is widespread throughout the vertebrate kingdom. The effect of O2 is selective but involves a wide range of transporters, including inorganic and organic systems, and both electroneutral and conductive pathways. Finally, we discuss what is known about the mechanism of the O2 effect and comment on its physiological and pathological roles.
Cranial Kinesis in Geckoes: Functional Implications
Authors: Herrel Anthony , Aerts Peter , Vree Frits De
Published: April 2021

Although it is generally assumed that cranial kinesis is a plesiomorphic characteristic in squamates, experimental data tend to contradict this hypothesis. In particular, coupled kinesis (i.e. streptostyly and mesokinesis) presumably arose independently in only a limited number of highly specialised groups. In this study, we investigated cranial kinesis in one of the most specialised of these groups: geckoes. On the basis of cineradiographic and electromyographic data, the fast opening and the slow closing/power stroke phases were modelled to elucidate possible functions of the observed kinesis. The results of these analyses show that the retraction of the muzzle unit during crushing is a self-reinforcing system that increases bite force and reduces the joint forces; the active protraction of the kinetic system during jaw opening, in contrast, enhances opening speed through the coupling of the intracranial units. It can be argued that cranial kinesis in geckoes is probably not an adaptive trait as such but, instead, a consequence of the ‘Bauplan’ of the cranial system in these animals. Presumably as a result of constructional constraints on the size of the jaw musculature and eyes, the supratemporal and postorbital bars were lost, which resulted in enormous mobility in the skull. To counteract the potential negative factors associated with this (decrease in bite force, skull damage), the kinetic system may have become coupled, and thus functional.
Changes in the Electric Organ Discharge After Pausing the Electromotor System Of Gymnotus Carapo
Authors: Schuster Stefan
Published: April 2021

During their entire lives, weakly electric fish produce an uninterrupted train of discharges to electrolocate objects and to communicate. In an attempt to learn about activity-dependent processes that might be involved in this ability, the continuous train of discharges of intact Gymnotus carapo was experimentally interrupted to investigate how this pausing affects post-pause electric organ discharges. In particular, an analysis was conducted of how the amplitude and relative timing of the three major deflections of the complex discharge change over the course of the first 1000 post-pause discharges. The dependence of these variables on the duration of the preceding pause and on water temperature is analysed. In addition, pause-induced small reverberations at the end of the discharge are described. Common to all amplitude changes is a fast initial decrease in amplitude with a slow recovery phase; amplitude changes scale with the duration of the preceding pause and are independent of the interdischarge interval. The absence of changes in the postsynaptic-potential-derived first phase of the discharge together with changes in the amplitude ratio of the third and fourth deflections suggest that the amplitude changes are mainly due to pause-induced changes in the inner resistance of the electric organ. A model is formulated that approximates the pattern of amplitude changes. The post-pause changes described here may provide a new way to test current models of complex discharge generation in Gymnotus carapo and illustrate the speed at which changes of an electric organ discharge can take place.