bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurochemical fine tuning of a peripheral tissue: peptidergic and aminergic regulation of fluid secretion by Malpighian tubules in the tobacco hawkmothM. sexta
Authors: Skaer N. J. V. , Nässel D. R. , Maddrell S. H. P. , Tublitz N. J.
Published: April 2021

The actions of various peptides and other compounds on fluid secretion by Malpighian tubules in the tobacco hawkmoth Manduca sexta sexta are investigated in this study. Using a newly developed pharate adult Malpighian tubule bioassay, we show that three tachykinin-related peptides (TRPs),leucokinin I, serotonin (5-HT), octopamine, the cardioacceleratory peptides 1a, 1b and 2c, cGMP and cAMP each cause an increase in the rate of fluid secretion in pharate adult tubules. Whereas the possible hormonal sources of biogenic amines and some of the peptides are known, the distribution of TRPs has not been investigated previously in M. sexta. Thus we performed immunocytochemistry using an anti-TRP antiserum. We show the presence of TRP-like material in a small subset of cells in the M. sexta central nervous system (CNS). The larval brain contains approximately 60 TRP-immunopositive cells and there are approximately 100 such cells in the adult brain including the optic lobes. Every ganglion of the ventral nerve cord also contains TRP-like immunoreactive cells. No TRP-containing neurosecretory cells were seen in the CNS, but endocrine cells of the midgut reacted with the antiserum.

We propose the hypothesis that the control in insects of physiological systems by hormones may not always involve tissue-specific hormones that force stereotypical responses in their target systems. Instead, there may exist in the extracellular fluid a continuous broadcast of information in the form of a chemical language to which some or all parts of the body continuously respond on a moment-to-moment basis, and which ensures a more effective and efficient coordination of function than could be achieved otherwise.
Sperm whale sound production studied with ultrasound time/depth-recording tags
Authors: Madsen P. T. , Payne R. , Kristiansen N. U. , Wahlberg M. , Kerr I. , Møhl B.
Published: April 2021

Delphinoids (Delphinidae, Odontoceti) produce tonal sounds and clicks by forcing pressurized air past phonic lips in the nasal complex. It has been proposed that homologous, hypertrophied nasal structures in the deep-diving sperm whale (Physeter macrocephalus) (Physeteridae, Odontoceti) are dedicated to the production of clicks. However, air volumes in diving mammals are reduced with increasing ambient pressure, which seems likely to influence pneumatic sound production at depth. To study sperm whale sound production at depth, we attached ultrasound time/depth-recording tags to sperm whales by means of a pole and suction cup. We demonstrate that sperm whale click production in terms of output and frequency content is unaffected by hydrostatic reduction in available air volume down to less than 2% of the initial air volume in the nasal complex. We present evidence suggesting that the sound-generating mechanism has a bimodal function, allowing for the production of clicks suited for biosonar and clicks more suited for communication. Shared click features suggest that sound production in sperm whales is based on the same fundamental biomechanics as in smaller odontocetes and that the nasal complexes are therefore not only anatomically but also functionally homologous in generating the initial sound pulse.
Breaking a paradigm: male-produced aggregation pheromone for the Colorado potato beetle
Authors: Dickens Joseph C. , Oliver James E. , Hollister Benedict , Davis John C. , Klun Jerome A.
Published: April 2021

A male-produced aggregation pheromone was identified for the Colorado potato beetle Leptinotarsa decemlineata (Say) (Coleoptera:Chrysomelidae). While male beetles produced only minor amounts of the pheromone, its production could be enhanced by topical application of juvenile hormone III (JH III) (eightfold), by antennectomy (40-fold) or by the combined treatment of JH III and antennectomy (almost 200-fold); this enhancement enabled the identification of the compound as(S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol [(S)-CPB I], a unique structure for an insect pheromone. Antennal receptors of both sexes responded selectively to the (S)-enantiomer. Both male and female Colorado potato beetles were attracted to serial source loads of(S)-CPB I in laboratory bioassays; (R)-CPB I was inactive or inhibitory, as demonstrated by the inactivity of the racemate. This is the first identification of a pheromone for the Colorado potato beetle and differs from the paradigm of a female-produced pheromone for this insect. The attractant is also the first male-produced pheromone identified for the Chrysomelidae. The discovery that both JH III and antennectomy increase levels of the pheromone (S)-CPB I indicates the existence of a feedback system involving antennal input, and this system may be under hormonal control.
Radula-centric and odontophore-centric kinematic models of swallowing inAplysia californica
Authors: Drushel Richard F. , Sutton Greg P. , Neustadter David M. , Mangan Elizabeth V. , Adams Benjamin W. , Crago Patrick E. , Chiel Hillel J.
Published: April 2021

Two kinematic models of the radula/odontophore of the marine mollusc Aplysia californica were created to characterize the movement of structures inside the buccal mass during the feeding cycle in vivo. Both models produce a continuous range of three-dimensional shape changes in the radula/odontophore, but they are fundamentally different in construction. The radulacentric model treats the radular halves as rigid bodies that can pitch, yaw and roll relative to a fixed radular stalk, thus creating a three-dimensional shape. The odontophore-centric model creates a globally convex solid representation of the radula/odontophore directly, which then constrains the positions and shapes of internal structures. Both radula/odontophore models are placed into a pre-existing kinematic model of the I1/I3 and I2 muscles to generate three-dimensional representations of the entire buccal mass. High-temporal-resolution, mid-sagittal magnetic resonance(MR) images of swallowing adults in vivo are used to provide non-invasive, artifact-free shape and position parameter inputs for the models. These images allow structures inside the buccal mass to be visualized directly, including the radula, radular stalk and lumen of the I1/I3 cavity. Both radula-centric and odontophore-centric models were able to reproduce two-dimensional, mid-sagittal radula/odontophore and buccal mass kinematics,but the odontophore-centric model's predictions of I1/I3, I2 and I7 muscle dimensions more accurately matched data from MR-imaged adults and transilluminated juveniles.
Substrate utilization during graded aerobic exercise in rainbow trout
Authors: Richards Jeff G. , Mercado Ashley J. , Clayton Cheryl A. , Heigenhauser George J. F. , Wood Chris M.
Published: April 2021

A biochemical approach was employed to examine the oxidative utilization of carbohydrate and lipid in red muscle of rainbow trout (Oncorhynchus mykiss) during sustained swimming at 30 and 60% of their critical swimming speed (Ucrit; for 2, 15 and 240 min) and during non-sustainable swimming at 90% Ucrit (for 2, 15 and 45 min). Measurements included pyruvate dehydrogenase (PDH) activity, creatine phosphate, ATP, glycogen, glycolytic intermediates, acetyl-CoA, acetyl-,total-, free-, short-chain fatty acyl- and long-chain fatty acyl- carnitine,intramuscular triacylglycerol and malonyl-CoA concentrations, and whole body oxygen consumption(ṀO2). During the first 2 min at 30 and 60% Ucrit, oxidation of endogenous glycogen by PDH activation increased 4- and 8-fold, respectively, yielding 1.5- to 2.5-fold increases in acetyl-CoA and 2- to 6-fold increases in acetyl-carnitine concentrations. Within 15 min, PDH activity returned to control values (153.9±30.1 nmol g-1 wet tissue min-1); after 240 min there were small 1.7- to 2.6-fold increases in long-chain fatty acyl-carnitine and approx. 50% decreases in malonyl-CoA concentrations, indicating an overall enhancement of lipid oxidation. Sustainable swimming at 30 and 60% Ucrit was further characterized by 1.5- and 2.2-fold increases in ṀO2,respectively. Non-sustainable swimming at 90% Ucrit was characterized by a sustained tenfold (approx.) elevation of red muscle PDH activity (approx. 1600 nmol g-1 wet tissue min-1). Significant 67% decreases in white muscle creatine phosphate and 73% decreases in glycogen levels, without matching increases in lactate levels, point to significant recruitment of white muscle during high-speed swimming for power production, and the potential export of white muscle lactate to red muscle for oxidation. Overall, sustainable exercise at 30 and 60%Ucrit is supported by approximately equal contributions of carbohydrate (approx. 45%) and lipid (approx. 35%) oxidation, whereas non-sustainable swimming is supported primarily by carbohydrate oxidation with only moderate contributions from lipid oxidation.
Scaling of rotational inertia in murine rodents and two species of lizard
Authors: Walter Rebecca M. , Carrier David R.
Published: April 2021

Because the force required to rotate a body about an axis is directly proportional to its rotational inertia about the axis, it is likely that animals with high rotational inertia would be constrained in their turning abilities. Given that rotational inertia scales with mass1.67 in geometrically similar animals, whereas the ability to apply torque scales with mass1.00, larger animals would be expected to have more difficulty turning than smaller animals of similar shape. To determine how rotational inertia scales with body mass, we used the fact that the period of a physical pendulum is proportional to its rotational inertia0.50, and measured rotational inertia in two groups of vertebrates with greatly different body shapes: murine rodents (Mus domesticus and Rattus norvegicus) and lizards (Iguana iguana and Varanus exanthematicus). Rotational inertia did not deviate significantly from isometric scaling in the murine rodents as a group or in the varanid lizards,scaling with mass1.63 and mass1.59, respectively. Although rotational inertia did scale with negative allometry in iguanas and rats alone, with mass1.56 and mass1.42, respectively, it still increased much more quickly with increasing mass than the predicted ability to apply torque. This suggests either that these animals are not constrained by rotational inertia because of their relatively small size or that larger rodents and lizards are poorer turners than smaller ones. The murine rodents had a 3.0- to 4.9-fold lower rotational inertia than similarly sized lizards of either species. Given that the basal synapsids had body proportions and limb configurations similar to those of modern lizards, we suggest that the loss of the large muscular tail and elongated body form during the evolution of cynodonts and mammals reduced rotational inertia and probably improved turning ability.
`Superfast' or masticatory myosin and the evolution of jaw-closing muscles of vertebrates
Authors: Hoh Joseph F. Y.
Published: April 2021

There are four fibre types in mammalian limb muscles, each expressing a different myosin isoform that finely tunes fibre mechanics and energetics for locomotion. Functional demands on jaw-closer muscles are complex and varied,and jaw muscles show considerable phylogenetic plasticity, with a repertoire for myosin expression that includes limb, developmental, α-cardiac and masticatory myosins. Masticatory myosin is a phylogenetically ancient motor with distinct light chains and heavy chains. It confers high maximal muscle force and power. It is highly jaw-specific in expression and is found in several orders of eutherian and marsupial mammals including carnivores,chiropterans, primates, dasyurids and diprotodonts. In exceptional species among these orders, masticatory myosin is replaced by some other isoform. Masticatory myosin is also found in reptiles and fish. It is postulated that masticatory myosin diverged early during gnathostome evolution and is expressed in primitive mammals. During mammalian evolution, mastication of food became important, and in some taxa jaw closers replaced masticatory myosin with α-cardiac, developmental, slow or fast limb myosins to adapt to the variety of diets and eating habits. This occurred early in some taxa(rodents, ungulates) and later in others (macropods, lesser panda, humans). The cellular basis for the uniqueness of jaw-closing muscles lies in their developmental origin.
Temperature plasticity of contractile proteins in fish muscle
Authors: Watabe Shugo
Published: April 2021

Three myosin heavy chain isoforms with different actin-activated Mg2+-ATPase activities were found in the fast skeletal muscle from carp (Cyprinus carpio) acclimated to 10 and 30°C. The composition of three types of myosin heavy chain was dependent on acclimation temperature,demonstrating the presence of temperature-specific myosin isoforms in carp. Subsequently, the temperature-dependence of the sliding velocity of fluorescent F-actin in myosins isolated from 10°C- and 30°C-acclimated carp was measured. At 8°C, the filament velocity was three times higher for myosin from 10°C- than from 30°C-acclimated fish. Activation energies (Ea) for the sliding velocity of F-actin were 63 and 111 kJ mol-1 for myosins from 10°C- and 30°C-acclimated fish, respectively. Activation energy for actin-activated Mg2+-ATPase activity was 0.46 kJ mol-1 in myosin from 10°C-acclimated fish and 0.54 kJ mol-1 in myosin from 30°C-acclimated fish. The inactivation rate constant(KD) of Ca2+-ATPase was 7.5×10-4s-1 at 30°C for myosin from 10°C-acclimated fish, which was approximately twice that for myosin from 30°C-acclimated fish. It is suggested that these differences in thermostability reflect a more flexible structure of the myosin molecule in cold-acclimated carp, which results in a reduced activation enthalpy for contraction and, hence, a higher sliding velocity at low temperatures. Structural analysis of cDNAs encoding the carp myosin heavy chain demonstrated striking differences in two surface loops of myosin subfragment-1 (S1), loops 1 and 2, between the 10°C and 30°C types, which were predominantly expressed in carp acclimated to 10°C and 30°C, respectively. Chimeric myosins composed of Dictyostelium discoideum myosin backbones with loop sequences of carp S1 heavy chain isoforms demonstrated that the diversity of the loop 2 sequence of carp S1 affected the Vmax of actin-activated Mg2+-ATPase activity.
Adaptive plasticity of skeletal muscle energetics in hibernating frogs:mitochondrial proton leak during metabolic depression
Authors: Boutilier Robert G. , St-Pierre Julie
Published: April 2021

The common frog (Rana temporaria) spends the coldest months of each year overwintering in ice-covered ponds where temperatures can vary from 0.5 to 4.0°C. Over the course of a winter season, the animals enter progressively into a state of metabolic depression that relies almost exclusively on aerobic production of ATP. However, if aerobic metabolism is threatened, for example by increasingly hypoxic conditions, decreases in the animal's metabolic rate can reach upwards of 75% compared with the 50%decrease seen during normoxia. Under these conditions, the major proportion of the overall reduction in whole-animal metabolic rate can be accounted for by metabolic suppression of the skeletal muscle (which makes up approximately 40%of body mass). Little is known about the properties of mitochondria during prolonged periods of metabolic depression, so we have examined several aspects of mitochondrial metabolism in the skeletal muscle of frogs over periods of hibernation of up to 4 months. Mitochondria isolated from the skeletal muscle of frogs hibernating in hypoxic water show a considerable reorganisation of function compared with those isolated from normoxic submerged animals at the same temperature (3°C). Both the active (state 3) and resting (state 4)respiration rates of mitochondria decrease during hypoxic, but not normoxic,hibernation. In addition, the affinity of mitochondria for oxygen increases during periods of acute hypoxic stress during normoxic hibernation as well as during long-term hibernation in hypoxic water. The decrease in mitochondrial state 4 respiration rates during hypoxic hibernation evidently occurs through a reduction in electron-transport chain activity, not through a lowered proton conductance of the mitochondrial inner membrane. The reduced aerobic capacity of frog skeletal muscle during hypoxic hibernation is accompanied by lowered activities of key enzymes of mitochondrial metabolism caused by changes in the intrinsic properties of the mitochondria. In the absence of oxygen, the mitochondrial F1Fo-ATPase (the ATP synthase) begins to run backwards as it actively pumps protons from the matrix in an attempt to maintain the mitochondrial membrane potential. At this time, the ATP synthase functions as an ATPase to preserve a certain proton-motive force. Frogs limit ATP wastage during anoxia by a profound inhibition of the ATP synthase. Taken together, our studies show that protonmotive force is lowered aerobically by restricting electron supply and during anoxia by restricting mitochondrial ATPase activity.
Maintaining muscle mass during extended disuse: aestivating frogs as a model species
Authors: Hudson Nicholas J. , Franklin Craig E.
Published: April 2021

Prolonged muscle disuse in vertebrates can lead to a pathological change resulting in muscle wasting and a loss of muscle strength. In this paper, we review muscle disuse atrophy in the vertebrates and examine the factors that influence the magnitude of the atrophic response during extended periods of inactivity, both artificially imposed (e.g. limb immobilisation) and naturally occurring, such as the quiescence associated with dormancy (e.g. hibernation and aestivation). The severity of muscle atrophy is positively correlated with mass-specific metabolic rate, and the metabolic depression that occurs during dormancy would appear to have a protective role, reducing or preventing muscle atrophy despite periods of inactivity lasting 6-9 months. In the light of these findings, the role of reactive oxygen species and antioxidants during muscle disuse is emphasised.
The ecological and evolutionary interface of hummingbird flight physiology
Authors: Altshuler Douglas L. , Dudley Robert
Published: April 2021

The hovering ability, rapidity of maneuvers and upregulated aerobic capacity of hummingbirds have long attracted the interest of flight biologists. The range of intra- and interspecific variation in flight performance among hummingbirds, however, is equally impressive. A dominant theme in hummingbird evolution is progressive invasion of higher-elevation habitats. Hypobaric challenge is met behaviorally through compensatory changes in wingbeat kinematics, particularly in stroke amplitude. Over evolutionary time scales, montane colonization is associated with increases in body mass and relative wing area. Hovering ability has been well-studied in several North American hummingbird taxa, yet the broad range of interspecific variation in hummingbird axial and appendicular anatomy remains to be assessed mechanistically. Such varied features as tail length, molt condition and substantial weight change due to lipid-loading can dramatically alter various features of the flight envelope. Compared with our present knowledge of hovering performance in hummingbirds, the mechanics of forward flight and maneuvers is not well understood.

Relationships among flight-related morphology, competitive ability and foraging behavior have been the focus of numerous studies on tropical and temperate hummingbirds. Ecologists have hypothesized that the primary selective agents on hummingbird flight-related morphology are the behaviors involved in floral nectar consumption. However, flight behaviors involved in foraging for insects may also influence the evolution of wing size and shape. Several comparisons of hummingbird communities across elevational gradients suggest that foraging strategies and competitive interactions within and among species vary systematically across elevations as the costs of flight change with body size and wing shape.
Roughness-dependent friction force of the tarsal claw system in the beetlePachnoda marginata(Coleoptera, Scarabaeidae)
Authors: Dai Zhendong , Gorb Stanislav N. , Schwarz Uli
Published: April 2021

This paper studies slide-resisting forces generated by claws in the free-walking beetle Pachnoda marginata (Coleoptera, Scarabaeoidea)with emphasis on the relationship between the dimension of the claw tip and the substrate texture. To evaluate the force range by which the claw can interact with a substrate, forces generated by the freely moving legs were measured using a load cell force transducer. To obtain information about material properties of the claw, its mechanical strength was tested in a fracture experiment, and the internal structure of the fractured claw material was studied by scanning electron microscopy. The bending stress of the claw was evaluated as 143.4-684.2 MPa, depending on the cross-section model selected. Data from these different approaches led us to propose a model explaining the saturation of friction force with increased texture roughness. The forces are determined by the relative size of the surface roughness Ra (or an average particle diameter) and the diameter of the claw tip. When surface roughness is much bigger than the claw tip diameter, the beetle can grasp surface irregularities and generate a high degree of attachment due to mechanical interlocking with substrate texture. When Ra is lower than or comparable to the claw tip diameter, the frictional properties of the contact between claw and substrate particles play a key role in the generation of the friction force.
Behavioural and neuroendocrine effects of environmental background colour and social interaction in Arctic charr (Salvelinus alpinus)
Authors: Höglund Erik , Balm Paul H. M. , Winberg Svante
Published: April 2021

In salmonid fish, a darker skin colour has been suggested to signal social subordination. Substratum colour is another factor affecting skin pigmentation in fish; in the present experiment, juvenile Arctic charr (Salvelinus alpinus) were acclimated and allowed to interact in pairs for 5 days on a pale or dark background colour. Skin darkness was quantified prior to and following social interaction. Furthermore, agonistic behaviour and skin darkness were quantified, together with plasma levels of cortisol,adrenocorticotropin (ACTH) and α-melanocyte-stimulating hormone(α-MSH), and brain levels of monoamines and monoamine metabolites. The results show that fish interacting on a white background were more aggressive than those interacting on a black background. Social subordination resulted in skin darkening in fish kept on a white background, but not in fish kept on a black background. Furthermore, subordinate fish on a white background showed an elevation of brain norepinephric activity, an effect not seen in subordinate fish on a black background. Subordinate fish on both white and black backgrounds showed a similar activation of the brain serotonergic system and the hypothalamic—pituitary—interrenal axis. These results support the suggestion that skin darkening in subordinates acts as a social signal announcing social submission.
The C-start escape response ofPolypterus senegalus: bilateral muscle activity and variation during stage 1 and 2
Authors: Tytell Eric D. , Lauder George V.
Published: April 2021

The fast-start escape response is the primary reflexive escape mechanism in a wide phylogenetic range of fishes. To add detail to previously reported novel muscle activity patterns during the escape response of the bichir, Polypterus, we analyzed escape kinematics and muscle activity patterns in Polypterus senegalus using high-speed video and electromyography (EMG). Five fish were filmed at 250 Hz while synchronously recording white muscle activity at five sites on both sides of the body simultaneously (10 sites in total). Body wave speed and center of mass velocity, acceleration and curvature were calculated from digitized outlines. Six EMG variables per channel were also measured to characterize the motor pattern. P. senegalus shows a wide range of activity patterns, from very strong responses, in which the head often touched the tail, to very weak responses. This variation in strength is significantly correlated with the stimulus and is mechanically driven by changes in stage 1 muscle activity duration. Besides these changes in duration, the stage 1 muscle activity is unusual because it has strong bilateral activity, although the observed contralateral activity is significantly weaker and shorter in duration than ipsilateral activity. Bilateral activity may stiffen the body, but it does so by a constant amount over the variation we observed; therefore, P. senegalus does not modulate fast-start wave speed by changing body stiffness. Escape responses almost always have stage 2 contralateral muscle activity, often only in the anterior third of the body. The magnitude of the stage 2 activity is the primary predictor of final escape velocity.
Honeybee nestmate recognition: the thermal behaviour of guards and their examinees
Authors: Stabentheiner Anton , Kovac Helmut , Schmaranzer Sigurd
Published: April 2021

In honeybee colonies, guards protect their nest from various robbers including bees from other colonies. Infrared thermography showed that the guards and the bees examined by them (examinees) differ considerably in their thermal behaviour according to their particular role in the nestmate recognition process. The thorax surface temperature was on average higher and more variable in the examinees (36.1 °C, S.D.=4.14, N=1545, 303 bees) than in the guards (34.0 °C, S.D.=2.00, N=1681, 772 bees). During thorough examinations lasting longer than 30 s, more than 60 % of the examinees showed phases of intense thoracic heating of more than 2 °C(maximum temperature 48.5 °C), whereas most guards cooled down. Our data suggest that these examinees heat up their surface to enhance chemical signalling during examinations.
Cloning and characterization of the heart muscle isoform of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) from crayfish
Authors: Chen Dongdong , Zhang Zhiping , Wheatly Michele G. , Gao Yongping
Published: April 2021

This paper describes the cloning and functional characterization of the heart muscle isoform of Sarco/endoplasmic reticulum Ca2+-ATPase(SERCA) from crayfish Procambarus clarkii. The complete crayfish heart SERCA, identified by reverse transcription-polymerase chain reaction(RT-PCR) and rapid amplification of cDNA ends (RACE), consists of 4495 bp with a 3060 bp open reading frame, coding for 1020 amino acids. This isoform differs from the previously identified axial abdominal (tail) muscle SERCA solely in its C-terminal amino acids. The last nine amino acids of the tail muscle isoform are replaced by 27 hydrophobic amino acids in the heart isoform that have the potential to form an additional transmembrane domain. Consistent with other invertebrate studies, Southern blot analysis suggested that the heart and tail muscle isoforms are encoded from the same gene that is equally related to SERCA-1, -2 and -3 of vertebrates. The tissue distributions of these two isoforms have been assessed using isoform-specific probes and northern analysis. A cardiac-specific probe bound only to a 5.8 kb species in heart and had minimal cross-hybridization with 7.6 and 5.8 kb species in eggs and no hybridization with tail muscle. A tail-isoform-specific probe hybridized with a 4.5 kb species in tail muscle and cross-hybridized with a 4.5 kb species in eggs and 8.8 kb in heart muscle. Both isoforms are expressed in eggs suggesting that transcripts are formed early in development and are subsequently broadly expressed in all tissue types. Expression of the cardiac muscle SERCA isoform varied with the stage of moulting. Expression was high in intermoult and decreased in premoult. However, expression was restored rapidly in postmoult (within 2 days) unlike expression of tail muscle SERCA,which remained downregulated for weeks. Differences in contractility between the two muscle types in the postmoult period may explain these expression patterns.
Intracardiac flow separation in anin situperfused heart from Burmese pythonPython molurus
Authors: Wang Tobias , Altimiras Jordi , Axelsson Michael
Published: April 2021

The heart of non-crocodilian reptiles has two separate atria that receive blood from the systemic and pulmonary circulations. The ventricle is not fully divided, but is compartmentalised into two chambers (cavum dorsale and cavum pulmonale) by a muscular ridge that runs from the apex to the base of the ventricle. The muscular ridge is small in turtles, but is well developed in varanid lizards and many species of snakes. These anatomical differences correlate with an effective blood flow separation in varanid lizards, whereas turtles can exhibit very large cardiac shunts. Very little is known about the cardiac shunt patterns in other groups of reptiles.

Here we characterise cardiac performance and flow dynamics in the Burmese python (Python molurus) using an in situ perfused heart preparation. The pericardium remained intact and the two atria were perfused separately (Ringer solution), and the two systemic and the pulmonary outflows were independently cannulated. Right and left atrial filling pressures and ventricular outflow pressures of the pulmonary and systemic vessels could be manipulated independently, permitting the establishment of large experimental intraventricular pressure gradients across the muscular ridge. The maximal power output generated by the systemic side of the ventricle exceeded the maximal power output that was generated by the cavum pulmonale that perfuse the pulmonary circulation. Furthermore, systemic flow could be generated against a higher outflow pressure than pulmonary flow. Perfusate entering the right atrium was preferentially distributed into the pulmonary circulation,whereas perfusate into the left atrium was distributed to the systemic circulation.

Our study indicates that the well-developed muscular ridge can separate the cavum systemic and pulmonary sides of the heart to prevent mixing of systemic and pulmonary flows. Therefore, the heart of Python appears to exhibit a large degree of ventricular flow separation as previously described for varanid lizards. We speculate that the ventricular separation has evolved in response to the need of maintaining high oxygen delivery while protecting the pulmonary circulation from oedema as result of high vascular pressures.
Glycerol and NEFA kinetics in long-term fasting king penguins: phase IIversusphase III
Authors: Bernard S. F. , Fayolle C. , Robin J.-P. , Groscolas R.
Published: April 2021

In spontaneously fasting birds such as penguins, below a body mass threshold corresponding to the phase II—phase III transition, a metabolic and hormonal shift occurs and feeding behaviour is stimulated(`refeeding signal'). The major aim of this study was to determine whether a decrease in non-esterified fatty acid (NEFA) release from adipose tissue could be a component of this signal. Lipolytic fluxes and primary triacylglycerol:fatty acid (TAG:FA) cycling were determined in vivoin breeding, fasting king penguins (Aptenodytes patagonicus) using continuous infusions of 2-[3H]glycerol and 1-[14C]palmitate under field conditions. In phase II (after approximately 8 days of fasting, large fat stores, body protein spared, N=8), the rate of appearance (Ra) of glycerol and of NEFA were 5.7±0.8 and 10.5±0.4 μmol kg-1min-1, respectively, and the percentage of primary TAG:FA cycling was 41±7%. In phase III (after approximately 25 days of fasting, fat stores reduced by fourfold, increased body protein catabolism, N=9), Ra glycerol kg-1 body mass remained unchanged,whereas Ra glycerol kg-1 fat mass and Ra NEFA kg-1 body mass were increased by 2.8-fold and 1.5-fold, respectively. Increased Ra glycerol kg-1 fat mass was possibly the result of a 3.5-fold increase in circulating glucagon, the increased Ra NEFA kg-1 body mass being attributable to decreased primary TAG:FA cycling. Thus, triggering of the refeeding signal that redirects the behavior of fasting, incubating penguins from incubation towards the search for food after entrance into phase III cannot be ascribed to a reduction in lipolytic fluxes and NEFA availability.
Active ammonia excretion across the gills of the green shore crabCarcinus maenas: participation of Na+/K+-ATPase, V-type H+-ATPase and functional microtubules
Authors: Weihrauch Dirk , Ziegler Andreas , Siebers Dietrich , Towle David W.
Published: April 2021

Although aquatic animals are generally believed to export nitrogenous waste by diffusion of NH3 or NH4+ across external epithelia, evidence for active ammonia excretion has been found in a number of species. In the euryhaline green shore crab Carcinus maenas, active excretion of ammonia across isolated gills is reduced by inhibitors of the Na+/K+-ATPase and vacuolar-type H+-ATPase. In addition, a functional dynamic microtubule network is necessary, since application of colchicine, taxol or thiabendazole leads to almost complete blockage of active and gradient-driven ammonia excretion. Actin filaments seem not to play a role in the excretory process. The NH4+-dependent short-circuit current and the conductance of the isolated cuticle were reduced in a dose-dependent manner by amiloride,a non-specific inhibitor of the Na+/H+ exchanger and Na+ channels. Combined with an analysis of gill morphology, the strong intracellular but weak apical abundance of V-type H+-ATPase and the fact that ammonia flux rates are equal under buffered and unbuffered experimental conditions, our observations suggest a hypothetical model of transepithelial ammonia movement that features active uptake across the basolateral membrane, sequestration in acidified vesicles, vesicle transport via microtubules and exocytosis at the apical membrane.
Collision-avoidance and landing responses are mediated by separate pathways in the fruit fly,Drosophila melanogaster
Authors: Tammero Lance F. , Dickinson Michael H.
Published: April 2021

Flies rely heavily on visual feedback for several aspects of flight control. As a fly approaches an object, the image projected across its retina expands, providing the fly with visual feedback that can be used either to trigger a collision-avoidance maneuver or a landing response. To determine how a fly makes the decision to land on or avoid a looming object, we measured the behaviors generated in response to an expanding image during tethered flight in a visual closed-loop flight arena. During these experiments, each fly varied its wing-stroke kinematics to actively control the azimuth position of a 15°×15° square within its visual field. Periodically, the square symmetrically expanded in both the horizontal and vertical directions. We measured changes in the fly's wing-stroke amplitude and frequency in response to the expanding square while optically tracking the position of its legs to monitor stereotyped landing responses. Although this stimulus could elicit both the landing responses and collision-avoidance reactions, separate pathways appear to mediate the two behaviors. For example, if the square is in the lateral portion of the fly's field of view at the onset of expansion, the fly increases stroke amplitude in one wing while decreasing amplitude in the other, indicative of a collision-avoidance maneuver. In contrast, frontal expansion elicits an increase in wing-beat frequency and leg extension,indicative of a landing response. To further characterize the sensitivity of these responses to expansion rate, we tested a range of expansion velocities from 100 to 10 000° s-1. Differences in the latency of both the collision-avoidance reactions and the landing responses with expansion rate supported the hypothesis that the two behaviors are mediated by separate pathways. To examine the effects of visual feedback on the magnitude and time course of the two behaviors, we presented the stimulus under open-loop conditions, such that the fly's response did not alter the position of the expanding square. From our results we suggest a model that takes into account the spatial sensitivities and temporal latencies of the collision-avoidance and landing responses, and is sufficient to schematically represent how the fly uses integration of motion information in deciding whether to turn or land when confronted with an expanding object.
Exploring the sialome of the tick Ixodes scapularis
Authors: Valenzuela Jesus G. , Francischetti Ivo M. B. , Pham Van My , Garfield Mark K. , Mather Thomas N. , Ribeiro José M. C.
Published: April 2021

To attempt description of the set of mRNA and protein (sialome) expressed in the salivary glands of the tick Ixodes scapularis, we randomly sequenced 735 clones of a full-length salivary gland cDNA library of this arthropod and performed Edman degradation of protein bands from salivary gland homogenates (SGH) and saliva separated by SDS-PAGE. The sequences were grouped into 410 clusters, of which 383 are not associated with known I. scapularis sequences. 15- and 17-protein bands from PAGE yielded amino-terminal information on the saliva and salivary gland gels,respectively. We attributed 19 of these sequences to translation products of the cDNA library. Full-length sequences were obtained for 87 clones. Among these protein sequences are several protease inhibitors of distinct classes,metalloproteases, novel proteins with histamine-binding domains, and several peptide families of unknown function displaying different conserved cysteine residues, many of which contain single Kunitz domains. This work provides information into the diversity of messages expressed in the salivary glands of I. scapularis, describes novel sequences that may be responsible for known biological activites, indicates further biological activities that may be present in I. scapularis saliva and identifies novel vaccine targets that may be used in Lyme disease prevention.
Carbon dioxide and pH affect sperm motility of white sturgeon(Acipenser transmontanus)
Authors: Ingermann R. L. , Holcomb M. , Robinson M. L. , Cloud J. G.
Published: April 2021

Maintenance of sperm at pH values less than approximately 7.5 inhibited the onset of motility when sperm were subsequently diluted with water; maintenance at pH values above approximately 8.2 was associated with maximal motility upon dilution with water. Within 5∼min of exposure to low pH buffer (pH 6.9),there was a 50% decline in sperm motility upon dilution with water suggesting that exposure to low pH interferes with motility within a time frame that may affect fertilization. In most instances, maintenance of sperm under CO2 at a pressure of 4-5 kPa almost completely blocked their capacity for motility. Furthermore, exposing semen to increasing partial pressures of CO2 up to about 1 kPa resulted in a marked decrease in semen pH. These observations are consistent with the findings that the buffering capacity of semen is particularly low at physiological pH, and that this low buffering capacity corresponds to the highest pH sensitivity of the capacity for sperm motility. The low seminal buffering capacity may represent a physiological adaptation in the control of sperm function. It may also represent a vulnerability to environmental hypercapnia or metabolic acidosis.
Hearing asymmetry and auditory acuity in the Australian bushcricketRequena verticalis(Listroscelidinae; Tettigoniidae;Orthoptera)
Authors: Bailey Winston J. , Yang Suanne
Published: April 2021

Fluctuating asymmetry in bilaterally placed sensory structures of insects may be considered maladaptive; natural selection should favour a symmetrical system. Among bushcrickets or katydids, threshold hearing sensitivity is, in part, dependent on the size of the auditory spiracle in the prothorax. We tested the degree of natural asymmetry in the hearing system of the ensiferan orthopteran Requena verticalis by measuring the size of the auditory spiracle of females. Naturally occurring asymmetry approached 8%, which translates to a hearing bias at a threshold of only 0.8 dB. Auditory asymmetry of females was experimentally exaggerated by packing cotton wool into either the right or left auditory spiracle. We made neurophysiological recordings from the ascending auditory T-fibre in the neck connective and found that the left—right bias created by this operation approximated 5 dB; this is greater than that found in nature. For these experiments, sound was delivered to the operated side of the insect from a speaker placed at either 90° or 30° to the long-body axis. To test the influence of this induced auditory bias, free-moving females were allowed to orient towards a speaker emitting male calls at near-natural call intensities of 51 and 82 dB (SPL), 80 cm from the speaker on a flat arena. There was no variation in angle or vector between experimental and control insects, and there was no difference in acuity between intensity. We discuss the relevance of threshold measurements of bushcricket hearing systems in regard to sound localisation and, from these experiments question any role of asymmetry.
Mechanisms of acid secretion in pseudobranch cells of rainbow trout(Oncorhynchus mykiss)
Authors: Kern G. , Bösch S. T. , Unterhuber E. , Pelster B.
Published: April 2021

Cell suspensions of rainbow trout Oncorhynchus mykisspseudobranch, prepared by Ca2+ depletion and mechanical maceration,contained a distinct population of cells that always kept their relatively cuboidal shape and did not round up in suspension or proliferate after adhering to the surface of cell culture dishes. Phasecontrast microscopy revealed an extensive system of basal membrane invaginations, and Na+-K+-ATPase- and anionexchanger-like immunoreactivity could be localized in cell membranes. The cells were characterized by a high mitochondrial density. Using specific antibodies, V-ATPase subunit B was localized in the plasma membrane. Using a cytosensor microphysiometer, the rate of acid secretion of these cells was measured and compared with the activity of a gill cell preparation. Incubation of pseudobranch cells with bafilomycin A1 (10-6 moll-1), a specific inhibitor of V-ATPase, reduced the rate of acid secretion by about 10% under control conditions, while no effect of bafilomycin on the rate of acid secretion of gill cells was observed. Application of amiloride (5×10-5moll-1) reduced the rate of acid secretion in cells of both organs,pseudobranch and gills. Incubation of pseudobranch cells with DIDS(10-3 moll-1) resulted in a minor increase in the rate of proton secretion, but in cells prepared from the gills of rainbow trout acid secretion was reduced by about 30-40%. It is concluded that pseudobranch cells are equipped with various pathways to secrete protons, and that the anion exchange activity especially of pseudobranch cells appears to be different from that in gills.
Amino acid composition and nutritional quality of potato leaf phloem sap for aphids
Authors: Karley A. J. , Douglas A. E. , Parker W. E.
Published: April 2021

To define plant `nutritional quality' for aphids, the causal basis of the variation in aphid performance between host plants of different developmental ages was explored using the aphids Myzus persicae and Macrosiphum euphorbiae on potato plants (Solanum tuberosum). Both aphid species performed better on developmentally young (`pre-tuber-filling') plants than on mature (`tuber-filling') plants. Aphid performance did not vary with leaf phloem sucrose:amino acid ratio but could be related to changes in the amino acid composition of the phloem, which included a developmental shift from high glutamine levels in pre-tuber-filling plants to low glutamine levels in tuber-filling plants. Aphid performance on chemically defined `young' and`old' diets, with amino acid composition corresponding to that of phloem amino acid composition in pre-tuber-filling and tuber-filling plants, respectively,confirmed that phloem amino acid composition contributed to low aphid performance on tuber-filling plants. The relatively poor performance on `old'diets could be accounted for, at least in part, by depressed feeding rates. These data suggest that amino acid composition of the phloem is one factor shaping the nutritional quality of plants for aphids.
Osmoregulation in the terrestrial Christmas Island red crabGecarcoidea natalis(Brachyura: Gecarcinidae): modulation of branchial chloride uptake from the urine
Authors: Taylor H. H. , Greenaway P.
Published: April 2021

Crabs generally produce urine iso-osmotic to their haemolymph, but terrestrial crabs are able to vary the composition of their final excretory fluid (termed P) postrenally, in the branchial chambers. Regulatory aspects of branchial urine processing were investigated in the Christmas Island red crab Gecarcoidea natalis acclimated to drinking either freshwater (FW crabs) or 70% seawater (SW crabs). FW crabs released dilute P (mean[Cl-] 8.8 mmol l-1). Drinking 70% seawater caused the mean [Cl-] of the P to rise to 376 mmol l-1 over 5 days,approaching the haemolymph [Cl-]. FW crabs with saline-perfused branchial chambers absorbed chloride at a high rate (10 mmol kg-1h-1), and haemolymph [Cl-] increased at approximately 20 mmol l-1 h-1. SW crabs exhibited elevated haemolymph osmolalities and ion concentrations and zero branchial chloride uptake. FW crabs that were salt-loaded by branchial chamber perfusion over several hours downregulated, and eventually ceased, chloride uptake. The rate of downregulation, but not the initial chloride flux, was dependent on initial haemolymph [Cl-]. Intravascular infusion of NaCl caused immediate reduction in branchial [Cl-] of 80%. Crabs ingested and regurgitated the perfusion saline, supporting suggestions that reingestion of urine could conserve water and ions. Dopamine upregulated branchial chloride transport in G. natalis. This is consistent with the ion-regulatory effects of dopamine in euryhaline marine brachyurans but contrasts with its inhibitory effects in the terrestrial anomuran Birgus latro. Dopamine increased the rate of urine release in FW crabs. Urine composition appears to be unimportant in ionic regulation, except in the case of magnesium, levels of which were elevated in the urine of SW crabs.