bluuebunny/crossref_metadata_2025_split huggingface dataset:
The bioenergetics of embryonic diapause in an annual killifish, Austrofundulus limnaeus
Authors: Podrabsky Jason E. , Hand Steven C. 
Published: April 2021

ABSTRACT
The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds that dry out on a seasonal basis, thereby killing the adult and juvenile forms. Populations persist because diapausing embryos become embedded in the pond sediments. The rate of oxygen consumption of diapause II embryos is depressed by up to 90 % compared with that of developing embryos, and a parallel reduction is observed in heart rate. Developmental arrest was identified by cessation of somite proliferation and blockage of the ontogenetic increase in DNA content. Surprisingly, the arrest of metabolism and development is temporally offset as embryos reach diapause II; metabolic rate begins to decline 12 days prior to arrest of development. Release of embryos from diapause II is facilitated by increasing the light phase of the photoperiod. The rate of oxygen consumption of diapause III embryos is 84 % lower than the value preceding diapause III. The total energy flow of diapause II embryos apparently includes a contribution from anaerobic processes on the basis of calorimetric/respirometric ratios that are above the oxycaloric equivalent. Accumulations of lactate and ethanol at the expense of glycogen reserves are small or undetectable and do not account for the excess heat signal. Diapause II embryos maintain high [ATP]/[ADP] ratios and adenylate energy charge during diapause, consistent with a simultaneous depression of energy use and demand. Levels of AMP increase during early development and diapause II despite the highly charged adenylate pool. High values for [AMP]/[ATP] ratios in diapause II embryos are correlated with decreased rates of oxygen consumption and heat dissipation, which suggests a role for AMP in the depression of metabolism during early development and diapause II.
Ovipositing butterflies use a red receptor to see green
Authors: Kelber Almut 
Published: April 2021

ABSTRACT
Swallowtail butterflies of the species Papilio aegeus oviposit on the leaves of Rutaceae plants in Australia. They possess receptor types with sensitivity peaks around 390 nm (violet receptor) and 610 nm (red receptor), in addition to the receptor types common in insects with sensitivity peaks at 360 nm (ultraviolet receptor), 440 nm (blue receptor) and 540 nm (green receptor). Multiple-and dual-choice experiments show that females of P. aegeus prefer to oviposit on substrata that look green to humans. A class of simple models is developed to describe this choice behaviour in terms of linear interactions between the different spectral types of photoreceptors. The green receptor has a positive influence, whereas the blue (and possibly the ultraviolet and violet) receptor and the red receptor have negative influences on the choice behaviour. Colour choice for oviposition is thus guided by a single chromatic mechanism. Caterpillars of P. aegeus grow faster on young leaves which, according to the model, should be preferred by females for oviposition. The importance of the red receptor for the discrimination between different green leaves is discussed in ecological and comparative contexts. Finally, in an evolutionary perspective, the possibility is discussed that colour vision systems like those of honeybees might have evolved as a combination of two or more such chromatic mechanisms.
Measurement of oxygen partial pressure, its control during hypoxia and hyperoxia, and its effect upon light emission in a bioluminescent elaterid larva
Authors: Timmins Graham S. , Penatti Carlos A. A. , Bechara Etelvino J. H. , Swartz Harold M. 
Published: April 2021

ABSTRACT
This study investigates the respiratory physiology of bioluminescent larvae of Pyrearinus termitilluminans in relation to their tolerance to hypoxia and hyperoxia and to the supply of oxygen for bioluminescence. The partial pressure of oxygen was measured within the bioluminescent prothorax by in vivo electron paramagnetic resonance (EPR) oximetry following acclimation of larvae to hypoxic, normoxic and hyperoxic (normobaric) atmospheres and during periods of bioluminescence (during normoxia). The in the prothorax during exposure to an external of 15.2, 160 and 760 mmHg was 10.3±2.6, 134±0.9 and 725±73 mmHg respectively (mean ± S.D., N=5; 1 mmHg=0.1333 kPa). Oxygen supply to the larvae via gas exchange through the spiracles, measured by determining the rate of water loss, was also studied in the above atmospheres and was found not to be dependent upon . The data indicated that there is little to no active control of extracellular tissue within the prothorax of these larvae. The reduction in prothorax observed during either attack-response-provoked bioluminescence or sustained feeding-related bioluminescence in a normoxic atmosphere was variable, but fell within the range 10–25 mmHg. The effect of hypoxic atmospheres on bioluminescence was measured to estimate the intracellular within the photocytes of the prothorax. Above a threshold value of 50–80 mmHg, bioluminescence was unaffected by . Below this threshold, an approximately linear relationship between and bioluminescence was observed. Taken together with the extracellular measurements, this suggests that control of within the photocyte may occur. This work establishes that EPR oximetry is a valuable technique for long-term measurement of tissue in insects and can provide valuable insights into their respiratory physiology. It also raises questions regarding the hypothesis that bioluminescence can have a significant antioxidative effect by reduction of prothorax through oxygen consumption.
Fate of dietary sucrose and neosynthesis of amino acids in the pea aphid, Acyrthosiphon pisum, reared on different diets
Authors: Febvay G. , Rahbé Y. , Rynkiewicz M. , Guillaud J. , Bonnot G. 
Published: April 2021

ABSTRACT
The fate of sucrose, the major nutrient of an aphid’s natural food, was explored by radiolabeling in the pea aphid Acyrthosiphon pisum. To investigate the influence of nitrogen quality of food on amino acid neosynthesis, pea aphids were reared on two artificial diets differing in their amino acid composition. The first (diet A) had an equilibrated amino acid balance, similar to that derived from analysis of aphid carcass, and the other (diet B) had an unbalanced amino acid composition similar to that of legume phloem sap. Aphids grown on either diet expired the same quantity of sucrose carbon as CO2, amounting to 25–30 % of the ingested sucrose catabolized in oxidation pathways. On diet A, the aphids excreted through honeydew about twice as much sucrose carbon as on diet B (amounting to 12.6 % of the ingested sucrose for diet A and 8.4 % for diet B), while amounts of sucrose carbons incorporated into exuviae were almost identical (1.9 % of the ingested sucrose on diet A and 2.7 % on diet B). There was also no difference in the amounts of sucrose carbon incorporated into the aphid tissues, which represented close to 50 % of the ingested sucrose. Sucrose carbons in the aphid tissues were mainly incorporated into lipids and the quantities involved were the same in aphids reared on either diet. On diet B, we observed neosynthesis of all protein amino acids from sucrose carbons and, for the first time in an aphid, we directly demonstrated the synthesis of the essential amino acids leucine, valine and phenylalanine. Amino acid neosynthesis from sucrose was significantly higher on diet B (11.5 % of ingested sucrose carbons) than on diet A (5.4 %). On diet A, neosynthesis of most of the amino acids was significantly diminished, and synthesis of two of them (histidine and arginine) was completely suppressed. The origin of amino acids egested through honeydew was determined from the specific activity of the free amino acid pool in the aphid. Aphids are able to adjust to variation in dietary amino acids by independent egestion of each amino acid. While more than 80 % of excreted nitrogen was from food amino acids, different amino acids were excreted in honeydew of aphids reared on the two diets. The conversion yields of dietary sucrose into aphid amino acids determined in this study were combined with those obtained previously by studying the fate of amino acids in pea aphids reared on diet A. The origin of all the amino acid carbons in aphid tissues was thus computed, and the metabolic abilities of aphid are discussed from an adaptive point of view, with respect to their symbiotic status.
Nitrogen excretion and expression of urea cycle enzymes in the atlantic cod (Gadus morhua L.): a comparison of early life stages with adults
Authors: Chadwick Terry D. , Wright Patricia A. 
Published: April 2021

ABSTRACT
For many years, the urea cycle was considered to be relatively unimportant in the life history of most teleost fishes. In previous studies, we were surprised to find that newly hatched freshwater rainbow trout embryos had relatively high activities of the key urea cycle enzyme, carbamoyl phosphate synthetase III (CPSase III), and other enzymes in the pathway, whereas adult trout had much lower or non-detectable activities. The present study tested the hypothesis that urea cycle enzyme expression is unique to early stages of rainbow trout. In marine Atlantic cod (Gadus morhua) embryos, CPSase III, ornithine transcarbamoylase (OTCase), glutamine synthetase (GSase) and arginase activities were all expressed prior to hatching. Urea excretion was detected shortly after fertilization and rates were high relative to those of ammonia excretion (50–100 % of total nitrogen excreted as urea nitrogen; total=ammonia+urea). Urea concentration was relatively constant in embryos, but ammonia concentration increased by about fourfold during embryogenesis. Two populations of cod embryos were studied (from Newfoundland and New Brunswick), and significant differences in enzyme activities and excretion rates were detected between the two populations. In adult cod, CPSase III was not detectable in liver, white muscle, intestine and kidney tissues, but OTCase, GSase and arginase were present. Adult cod excreted about 17 % of nitrogenous waste as urea. Taken together, these data indicate that early urea cycle enzyme expression is not unique to rainbow trout but is also a feature of Atlantic cod development, and possibly other teleosts. The relatively high urea excretion rates underline the importance of urea as the primary nitrogen excretory product in Atlantic cod during early embryogenesis.
Contractile properties of atrial and ventricular myocardium of the heart of rainbow trout Oncorhynchus mykiss: effects of thermal acclimation
Authors: Aho Eija , Vornanen Matti 
Published: April 2021

ABSTRACT
Atrial and ventricular myocardium perform different tasks in the pumping work of the vertebrate heart, which are reflected in their contractile properties. Although atrial contraction is assumed to have an important role in the function of fish heart, the contractile properties of atrial and ventricular myocardium have not been directly compared in any fish species. The objective of this study was to clarify any contractile differences in the heart of teleost fish and, in particular, to elucidate the contribution of myofibrillar ATPase and intracellular Ca2+ stores to the characteristics of atrial and ventricular contraction. Experiments were conducted on thermally acclimated rainbow trout Oncorhynchus mykiss to determine whether the effects of temperature adaptation are the same in atrial and ventricular tissue. It was shown that the rate of isometric contraction is much faster in atrial than in ventricular tissue of the fish heart and that acclimation to cold increases the rate of contraction in both cardiac compartments. The rapid contraction kinetics of the atrial tissue were associated with higher myofibrillar ATPase activity and faster Ca2+ uptake rate of the sarcoplasmic reticulum (SR) compared with ventricular tissue. Similarly, the faster kinetics of contraction following cold acclimation could be attributed to enhancement of the myofibrillar and/or SR function. The atrio-ventricular and temperature-induced differences were also expressed in the recovery of force from inactivation, i.e. in the mechanical restitution. The refractory period and the rate constant of force restitution were shorter in atrial than in ventricular muscle tissue. Similar differences also existed between the tissues of cold-acclimated (CA, 4 °C) and warm-acclimated (WA, 17 °C) fish. The fast recovery of force from inactivation in the heart of the CA trout was, at least in part, due to more active SR. Furthermore, it was shown that the force of atrial contraction in the CA trout is sensitive to ryanodine (10 μmol l−1), a Ca2+-release channel blocker of SR, at physiological body temperature (4 °C) and at a physiological pacing rate (0.6 Hz). This finding indicates that the Ca2+ stores of SR contribute to activation of cardiac contraction in the fish heart, and that the SR of fish heart is able to retain its Ca2+ load at low body temperatures, i.e. the Ca2+ release channels of SR are not leaky in the cold. The present data show that in the atrial tissue of CA trout, the SR directly contributes to the cytosolic Ca2+ and that in the atrium and ventricle of CA trout, the SR significantly accelerates the recovery of contractility from inactivation. The fast recovery from inactivation allows relatively high heart rates and therefore adequate cardiac outputs at low environmental temperatures for the cold-active rainbow trout.
Effects of exogenous 17β-estradiol on the reproductive physiology and reproductive performance of european starlings (Sturnus vulgaris)
Authors: Christians Julian K. , Williams Tony D. 
Published: April 2021

ABSTRACT
Egg mass shows large intraspecific variation in birds and yet the mechanisms underlying this variation remain unknown. We hypothesized that estradiol would play a central role in determining egg mass, since this hormone stimulates the production of yolk precursors (vitellogenin and very-low density lipoprotein, VLDL) by the liver, and of albumen by the oviduct. We gave European starlings (Sturnus vulgaris) silastic implants containing estradiol prior to egg formation, which we predicted would increase egg mass. As expected, exogenous estradiol stimulated a marked (49 %) increase in plasma vitellogenin levels at the beginning of laying. At clutch completion, plasma VLDL levels and oviduct mass were also elevated in estradiol-treated females compared with controls. However, estradiol had no effect on fresh egg mass or clutch size. Estradiol treatment actually decreased the mass of yolk protein and lipid, perhaps by decreasing the rate of uptake of yolk precursors at the ovary. The failure of estradiol to increase egg mass indicates that this phenotype may be regulated at higher levels of organization (e.g. negative feedback, uptake of yolk precursors) than those studied in this experiment. Despite elevating yolk precursor levels, treatment with estradiol had no effect on the mass of the liver or endogenous stores of protein and lipid at clutch completion.
Development of an acoustic telemetry tag for monitoring electromyograms in free-swimming fish
Authors: Dewar Heidi , Deffenbaugh Max , Thurmond Gary , Lashkari Khosrow , Block Barbara A. 
Published: April 2021

ABSTRACT
We report the development of an acoustic telemetry tag used to monitor electromyograms (EMGs) remotely from free-swimming marine fish. The device described amplifies and filters the EMG and then converts the electrical waveform into a frequency-modulated acoustic signal that is transmitted through water. The signal is then received, demodulated and recorded by the receiving system. The EMG tag described has been tested on a range of species, including toadfish Opsanus tau, spiny dogfish Squalus acanthias, yellowfin tuna Thunnus albacares and eastern Pacific bonito Sarda chiliensis, in different tank environments. In certain tanks the fidelity with which the system replicates the EMG is sufficient to quantify accurately the onset, offset, duration, the integrated area under the absolute value of the signal and the number of signal zero crossings. This EMG tag will expand the scope of questions that can be addressed about the behavior and physiology of free-swimming fish.
Laboratory selection for the comparative physiologist
Authors: Gibbs Allen G. 
Published: April 2021

ABSTRACT
An increasingly popular experimental approach in comparative physiology is to study the evolution of physiological traits in the laboratory, using microbial, invertebrate and vertebrate models. Because selective conditions are well-defined, selected populations can be replicated and unselected control populations are available for direct comparison, strong conclusions regarding the adaptive value of an evolved response can be drawn. These studies have shown that physiological systems evolve rapidly in the laboratory, but not always as one would expect from comparative studies of different species. Laboratory environments are often not as simple as one thinks, so that the evolution of behavioral differences or selection acting on different life stages can lead to unanticipated results. In some cases, unexpected responses to laboratory selection may suggest new insights into physiological mechanisms, which might not be available using other experimental approaches. I outline here recent results (including success stories and caveats for the unwary investigator) and potential directions for selection experiments in comparative physiology.
Mosquito hearing: sound-induced antennal vibrations in male and female Aedes aegypti
Authors: Göpfert Martin C. , Briegel Hans , Robert Daniel 
Published: April 2021

ABSTRACT
Male mosquitoes are attracted by the flight sounds of conspecific females. In males only, the antennal flagellum bears a large number of long hairs and is therefore said to be plumose. As early as 1855, it was proposed that this remarkable antennal anatomy served as a sound-receiving structure. In the present study, the sound-induced vibrations of the antennal flagellum in male and female Aedes aegypti were compared, and the functional significance of the flagellar hairs for audition was examined. In both males and females, the antennae are resonantly tuned mechanical systems that move as simple forced damped harmonic oscillators when acoustically stimulated. The best frequency of the female antenna is around 230 Hz; that of the male is around 380 Hz, which corresponds approximately to the fundamental frequency of female flight sounds. The antennal hairs of males are resonantly tuned to frequencies between approximately 2600 and 3100 Hz and are therefore stiffly coupled to, and move together with, the flagellar shaft when stimulated at biologically relevant frequencies around 380 Hz. Because of this stiff coupling, forces acting on the hairs can be transmitted to the shaft and thus to the auditory sensory organ at the base of the flagellum, a process that is proposed to improve acoustic sensitivity. Indeed, the mechanical sensitivity of the male antenna not only exceeds the sensitivity of the female antenna but also those of all other arthropod movement receivers studied so far.
Locomotion on the water surface: hydrodynamic constraints on rowing velocity require a gait change
Authors: Suter Robert B. , Wildman Horatio 
Published: April 2021

ABSTRACT
Fishing spiders, Dolomedes triton (Araneae, Pisauridae), propel themselves across the water surface using two gaits: they row with four legs at sustained velocities below 0.2 m s−1 and they gallop with six legs at sustained velocities above 0.3m s−1. Because, during rowing, most of the horizontal thrust is provided by the drag of the leg and its associated dimple as both move across the water surface, the integrity of the dimple is crucial. We used a balance, incorporating a biaxial clinometer as the transducer, to measure the horizontal thrust forces on a leg segment subjected to water moving past it in non-turbulent flow. Changes in the horizontal forces reflected changes in the status of the dimple and showed that a stable dimple could exist only under conditions that combined low flow velocity, shallow leg-segment depth and a long perimeter of the interface between the leg segment and the water. Once the dimple disintegrated, leaving the leg segment submerged, less drag was generated. Therefore, the disintegration of the dimple imposes a limit on the efficacy of rowing with four legs. The limited degrees of freedom in the leg joints (the patellar joints move freely in the vertical plane but allow only limited flexion in other planes) impose a further constraint on rowing by restricting the maximum leg-tip velocity (to approximately 33 % of that attained by the same legs during galloping). This confines leg-tip velocities to a range at which maintenance of the dimple is particularly important.
The weight of the spider also imposes constraints on the efficacy of rowing: because the drag encountered by the leg-cum-dimple is proportional to the depth of the dimple and because dimple depth is proportional to the supported weight, only spiders with a mass exceeding 0.48 g can have access to the full range of hydrodynamically possible dimple depths during rowing. Finally, the maximum velocity attainable during rowing is constrained by the substantial drag experienced by the spider during the glide interval between power strokes, drag that is negligible for a galloping spider because, for most of each inter-stroke interval, the spider is airborne.
We conclude that both hydrodynamic and anatomical constraints confine rowing spiders to sustained velocities lower than 0.3 m s−1, and that galloping allows spiders to move considerably faster because galloping is free of these constraints.
Effect of High Altitude and In Vivo Adenosine/β-Adrenergic Receptor Blockade on ATP and 2,3Bpg Concentrations in Red Blood Cells of Avian Embryos
Authors: Dragon Stefanie , Carey Cynthia , Martin Kathy , Baumann Rosemarie 
Published: April 2021

ABSTRACT
In chick embryos, developmental changes of the blood oxygen tension control hemoglobin (Hb) oxygen affinity via modulation of ATP and 2,3BPG concentrations in red blood cells. Hypoxia, which is a normal developmental condition for late chick embryos, causes a decrease of the red cell ATP concentration (and increase of red cell oxygen affinity) as well as activation of 2,3BPG synthesis via cyclic AMP-dependent signaling. Adenosine and catecholamines have been implicated as signaling substances in these red cell responses. To assess the extent to which adenosine and catecholamines are involved in vivo in the control of red cell ATP/2,3BPG concentrations, day 13 chick embryos were treated for 24 h with adenosine A2 and/or β-adrenergic receptor blockers and red cell ATP and 2,3BPG levels were determined. The data suggest that adaptive effects later in development in chick embryos induced by adenosine and catecholamines are vital. We have also tested whether avian embryos of the free-living, high-altitude, native white-tailed ptarmigan (Lagopus leucurus) alter their organic phosphate pattern in red cells in response to incubation at different altitudes. Embryos incubated at 3600–4100 m decrease their red cell ATP concentration much more rapidly than embryos of the same clutch incubated at 1600 m. From these data it can be inferred that the oxygen affinity of high altitude embryos will be adjusted to the altitude at which the eggs are incubated.