bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respiration and energetics of embryonic development in a large altricial bird, the Australian pelican (Pelecanus conspicillatus)
Authors: Pearson James T. , Seymour Roger S. , Baudinette Russell V. , Runciman Susan 
Published: April 2021

SUMMARYWe examined whether the previously reported low cost of embryonic development in pelicans could be attributed to a more efficient conversion of egg energy to hatchling tissues as a result of high initial egg water content,low embryonic metabolic rate and growth later in incubation than in more precocious species. We therefore determined egg and hatchling composition and the development of embryonic respiration in the Australian pelican Pelecanus conspicillatus, which lays one of the largest eggs (140-210 g) with an altricial developmental mode. The small yolk fraction (21%) is typical of all pelecaniforms; however, we found that intraspecific variability in fresh egg mass was related to water content (principally in the albumen),but independent of yolk mass (mean 13 g dry mass). P. conspicillatuseggs have, on average, 635 kJ of energy, irrespective of egg mass across the whole range of egg mass.The embryonic developmental pattern of O2 consumption and CO2 production showed clear plateaus lasting 2-3 days immediately prior to internal pipping, resembling the typical precocial pattern. However,the rate of pre-internal pipping O2 consumption was low in comparison with that of precocial species of similar egg mass. There is no evidence to support the hypothesis that the observed plateau in rates of O2 uptake is due to a diffusion limitation of the eggshell gas conductance in this species. Embryonic metabolic rate nearly doubled during the pipping period, but the mass-independent metabolic rate of the hatchling was low in comparison with that of the resting adult. The total O2consumed (11 063 ml) is equivalent to 217.3 kJ (or 34% of egg energy) based on indirect calorimetry and the observed respiratory exchange ratio of 0.71. Thus, the cost of development (direct calorimetry) was 0.29 kJ J-1in the egg (mean egg mass 168 g), which is one of lowest reported values. As a result, the production efficiency of pelican embryonic development was 61.6%,higher than the average for birds in general (56.9%) and, in particular, of seabirds that have prolonged incubation periods on the basis of egg mass. High efficiency in embryonic development in this species was attained as a result of rapid embryonic growth later in incubation, low hatchling energy density(23.6 kJ g-1 dry matter) and dry matter content, low embryonic metabolic rate throughout incubation and a shorter than expected incubation period of 33 days (predicted 36 days).
The role of Ca2+ in stimulated bioluminescence of the dinoflagellateLingulodinium polyedrum
Authors: von Dassow Peter , Latz Michael I. 
Published: April 2021

SUMMARYMany marine dinoflagellates emit bright discrete flashes of light nearly instantaneously in response to either laminar or turbulent flows as well as to direct mechanical stimulation. The flash involves a unique pH-dependent luciferase and a proton-mediated action potential across the vacuole membrane. The mechanotransduction process initiating this action potential is unknown. The present study investigated the role of Ca2+ in the mechanotransduction process regulating bioluminescence in the dinoflagellate Lingulodinium polyedrum. Calcium ionophores and digitonin stimulated luminescence in a Ca2+-dependent manner in the absence of mechanical stimulation. Mechanically sensitive luminescence was strongly inhibited by the intracellular Ca2+ chelator BAPTA-AM[1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester]; there was only a partial and irreversible dependence on extracellular Ca2+. Ruthenium Red, a blocker of intracellular Ca2+ release channels, inhibited mechanically sensitive luminescence. Luminescence was also stimulated by increasing K+, even in the absence of extracellular Ca2+; K+ stimulation was inhibited both by BAPTA-AM and Ruthenium Red. These results support the hypothesis that Ca2+mediates stimulated bioluminescence and also indicate the involvement of intracellular Ca2+ stores. Rapid coupling between mechanical stimulation and mobilization of intracellular Ca2+ stores might occur through a mechanism similar to excitation-contraction coupling in skeletal muscle.
The structural basis for water exchange between the female cockroach (Blattella germanica) and her ootheca
Authors: Mullins Donald E. , Mullins K. June , Tignor Keith R. 
Published: April 2021

SUMMARYFemale German cockroaches usually carry their oothecae until they hatch. The success of embryogenesis may be dependent on the water-balance relationship between females and their developing oothecae. Oothecae detached from females early in embryogenesis often fail to develop, especially in low-humidity environments. Experiments reported here using tritiated water have confirmed the transport of a significant amount of water to the ootheca from the female during embryogenesis; 18% of the tritiated water injected into gravid females was recovered in their oothecae after 24 h. We describe a structural basis of water absorption by the oothecae. An area located on the proximal end of the ootheca (adjacent to the `escutcheon-shaped vaginal imprint') contains small pores that penetrate the oothecal covering to access regions of the chorion lying beneath these pores. Experiments using microparabiotic chambers to examine transport of tritiated water and water-soluble materials across the escutcheon region of the oothecal covering, along with dark-field birefringent microscopy of the chorion, support the hypothesis that this chorionic network is capable of conducting water throughout the interior of the ootheca. Furthermore, the structural arrangement and intimate association of the female vestibulum with the oothecal pore field contained in the region of the escutcheon-shaped vaginal imprint appear to provide an efficient conduit to the chorion. The overall structural relationship might be a means for maintaining water balance between females and their oothecae during embryonic development. Evidence presented here supports observations that this species represents an important link in the transition from oviparity to ovoviviparity by internalization of cockroach oothecae.
Fluid dynamics of flapping aquatic flight in the bird wrasse:three-dimensional unsteady computations with fin deformation
Authors: Ramamurti Ravi , Sandberg William C. , Löhner Rainald , Walker Jeffrey A. , Westneat Mark W. 
Published: April 2021

SUMMARYMany fishes that swim with the paired pectoral fins use fin-stroke parameters that produce thrust force from lift in a mechanism of underwater flight. These locomotor mechanisms are of interest to behavioral biologists,biomechanics researchers and engineers. In the present study, we performed the first three-dimensional unsteady computations of fish swimming with oscillating and deforming fins. The objective of these computations was to investigate the fluid dynamics of force production associated with the flapping aquatic flight of the bird wrasse Gomphosus varius. For this computational work, we used the geometry of the wrasse and its pectoral fin,and previously measured fin kinematics, as the starting points for computational investigation of three-dimensional (3-D) unsteady fluid dynamics. We performed a 3-D steady computation and a complete set of 3-D quasisteady computations for a range of pectoral fin positions and surface velocities. An unstructured, grid-based, unsteady Navier—Stokes solver with automatic adaptive remeshing was then used to compute the unsteady flow about the wrasse through several complete cycles of pectoral fin oscillation. The shape deformation of the pectoral fin throughout the oscillation was taken from the experimental kinematics. The pressure distribution on the body of the bird wrasse and its pectoral fins was computed and integrated to give body and fin forces which were decomposed into lift and thrust. The velocity field variation on the surface of the wrasse body, on the pectoral fins and in the near-wake was computed throughout the swimming cycle. We compared our computational results for the steady, quasi-steady and unsteady cases with the experimental data on axial and vertical acceleration obtained from the pectoral fin kinematics experiments. These comparisons show that steady state computations are incapable of describing the fluid dynamics of flapping fins. Quasi-steady state computations, with correct incorporation of the experimental kinematics, are useful when determining trends in force production, but do not provide accurate estimates of the magnitudes of the forces produced. By contrast, unsteady computations about the deforming pectoral fins using experimentally measured fin kinematics were found to give excellent agreement, both in the time history of force production throughout the flapping strokes and in the magnitudes of the generated forces.
Postnatal ecdysis establishes the permeability barrier in snake skin: new insights into barrier lipid structures
Authors: Tu M. C. , Lillywhite H. B. , Menon J. G. , Menon G. K. 
Published: April 2021

SUMMARY
A competent barrier to transepidermal water loss (TEWL) is essential for terrestrial life. In various vertebrates, epidermal water barriers composed of lipids prevent excessive TEWL, which varies inversely with habitat aridity. Little is known, however, about the mechanisms and regulation of permeability relative to natal transition from the `aqueous' environments of gestation to the `aerial' environments of terrestrial neonates. We investigated newly hatched California king snakes Lampropeltis getula to test the hypothesis that the first ecdysis is important for establishing the barrier to TEWL. We found that skin resistance to TEWL increases twofold following the first postnatal ecdysis, corresponding with a roughly twofold increase in thickness and deposition of lamellar lipids in the mesos layer, the site of the skin permeability barrier in snakes. In addition, novel observations on lipid inclusions within the alpha layer of epidermis suggest that this layer has functional similarities with avian epidermis. It appears that emergence of the integument from embryonic fluids, and its subsequent pan-body replacement following contact with air, are essential for completion of barrier competence in the newborn. These conditions provide a potentially useful model for investigations on the mechanism of barrier formation. We also found that hatchling snakes are transiently endothermic, with skin temperatures elevated by approximately 0.6°C above ambient air temperature during the period of barrier formation. Behaviourally, hatchlings showed a higher tendency to seek humid microenvironments before the first ecdysis than after. The degree of water movement across the integument might explain the switch from reclusive to dispersive behaviours associated with postnatal ecdysis in snakes.
Effects of metabolite uptake on proton-equivalent elimination by two species of deep-sea vestimentiferan tubeworm,Riftia pachyptilaandLamellibrachiacfluymesi: proton elimination is a necessary adaptation to sulfide-oxidizing chemoautotrophic symbionts
Authors: Girguis P. R. , Childress J. J. , Freytag J. K. , Klose K. , Stuber R. 
Published: April 2021

SUMMARYIntracellular symbiosis requires that the host satisfy the symbiont's metabolic requirements, including the elimination of waste products. The hydrothermal vent tubeworm Riftia pachyptila and the hydrocarbon seep worm Lamellibrachia cf luymesi are symbiotic with chemolithoautotrophic bacteria that produce sulfate and protons as end-products. In this report, we examine the relationship between symbiont metabolism and host proton equivalent elimination in R. pachyptilaand L. cf luymesi, and the effects of sulfide exposure on proton-equivalent elimination by Urechis caupo, an echiuran worm that lacks intracellular symbionts (for brevity, we will hereafter refer to proton-equivalent elimination as `proton elimination'). Proton elimination by R. pachyptila and L. cf luymesi constitutes the worms' largest mass-specific metabolite flux, and R. pachyptilaproton elimination is, to our knowledge, the most rapid reported for any metazoan. Proton elimination rates by R. pachyptila and L.cf luymesi correlated primarily with the rate of sulfide oxidation. Prolonged exposure to low environmental oxygen concentrations completely inhibited the majority of proton elimination by R. pachyptila,demonstrating that proton elimination does not result primarily from anaerobic metabolism. Large and rapid increases in environmental inorganic carbon concentrations led to short-lived proton elimination by R. pachyptila, as a result of the equilibration between internal and external inorganic carbon pools. U. caupo consistently exhibited proton elimination rates 5-20 times lower than those of L. cf luymesi and R. pachyptila upon exposure to sulfide. Treatment with specific ATPase inhibitors completely inhibited a fraction of proton elimination and sulfide and inorganic carbon uptake by R. pachyptila, suggesting that proton elimination occurs in large part via K+/H+-ATPases and Na+/H+-ATPases. In the light of these results, we suggest that protons are the primary waste product of the symbioses of R. pachyptila and L. cf luymesi, and that proton elimination is driven by symbiont metabolism, and may be the largest energetic cost incurred by the worms.
Response of western diamondback rattlesnakesCrotalus atroxto airborne sounds
Authors: Young Bruce A. , Aguiar Amie 
Published: April 2021

SUMMARYIn order to test the hypothesis that snakes can not only perceive airborne sounds, but also respond to them, an acoustic isolation chamber was designed and constructed to perform best within the 150-450 Hz range in which snakes perceive sound. Suspended within this acoustic chamber was a steel mesh basket designed to minimize the potential for groundborne vibrations. A synthesized tone was created out of 20 different 150 ms sounds, each separated by a 50 ms period of silence; the acoustic energy of each of the 20 sounds was concentrated between 200-400 Hz, and each sound included frequency modulation. The trial stimuli were presented to western diamondback rattlesnakes Crotalus atrox at a level 5-10 dB above their perception threshold. Four significant behavioural responses were observed upon stimulus presentation: cessation of body movements, reduction or cessation of tongue flicking, rapid jerks of the head and rattling. At least one significant behavioural response was observed in 92% of the behavioural trials. This study provides the first experimental evidence that snakes can respond behaviourally to airborne sounds.
Protein turnover, amino acid profile and amino acid flux in juvenile shrimpLitopenaeus vannamei: effects of dietary protein source
Authors: Mente Eleni , Coutteau Peter , Houlihan Dominic , Davidson Ian , Sorgeloos Patrick 
Published: April 2021

SUMMARYThe effect of dietary protein on protein synthesis and growth of juvenile shrimps Litopenaeus vannamei was investigated using three different diets with equivalent protein content. Protein synthesis was investigated by a flooding dose of tritiated phenylalanine. Survival, specific growth and protein synthesis rates were higher, and protein degradation was lower, in shrimps fed a fish/squid/shrimp meal diet, or a 50% laboratory diet/50%soybean meal variant diet, than in those fed a casein-based diet. The efficiency of retention of synthesized protein as growth was 94% for shrimps fed the fish meal diet, suggesting a very low protein turnover rate; by contrast, the retention of synthesized protein was only 80% for shrimps fed the casein diet. The amino acid profile of the casein diet was poorly correlated with that of the shrimps. 4 h after a single meal the protein synthesis rates increased following an increase in RNA activity. A model was developed for amino acid flux, suggesting that high growth rates involve a reduction in the turnover of proteins, while amino acid loss appears to be high.
Effects of age and size in the ears of gekkonomorph lizards: middle-ear sensitivity
Authors: Werner Yehudah L. , Igić Petar G. , Seifan Merav , Saunders James C. 
Published: April 2021

SUMMARY
Previous studies of electrophysiological audiograms in gekkonomorph lizards revealed greater sensitivity in adults than in juveniles. We investigated whether this difference, as far as it is affected by the middle ear, is due to animal age or size. The velocity transfer function of the tympanic membrane(TM) was examined using laser interferometry in nine samples: adults of three large gekkonomorph species, adults of three small species (each related to one of the former), and juveniles of the large species, their sizes matching those of the small-species adults. Each transfer function exhibited an inverted `V'or `U' shape, with the velocity of TM motion peaking in the mid-frequency range and becoming poorer at lower and higher frequencies. Among samples,maximum TM velocity correlated with animal length, perhaps because of a damping change in the larger TM. The frequency at maximum velocity negatively correlated with measurements of TM area. Presumably, with a larger TM area,the best frequency shifted downward because of increased middle-ear mass or decreased stiffness. The bandwidth of the transfer function negatively correlated with animal length, being broader in smaller animals and sharper in larger animals. This effect can be attributed to increased mass, decreased damping, or both. Among the middle-ear morphological measurements, the one most closely correlated with body length was the length of the extracolumellar anchorage at the TM. Among the physiological variables investigated, maximum velocity was negatively correlated with the frequency at which it occurred. The dependence of these transfer function variables on animal and ear size was similar, regardless of whether the comparison was among adults of species of different sizes, or among age classes within a species, so that age differences appear to be largely the result of size differences.
The sun compass of the sandhopperTalitrus saltator: the speed of the chronometric mechanism depends on the hours of light
Authors: Ugolini Alberto , Tiribilli Bruno , Boddi Vieri 
Published: April 2021

SUMMARYExperiments on solar orientation were conducted with adult amphipods(Talitrus saltator) subjected to a reduction and/or phase shift of the hours of light (L) or dark (D) with respect to the natural photoperiod: 15 h:9 h L:D (controls), 15 h:9 h inverted (i.e. phase-shifted by 12 h and tested with the sun during the subjective night), 4 h:20 h, 20 h:4 h inverted. The sandhoppers were released in a confined environment, and individual orientation angles were recorded. The results confirm the continuous operation, through the entire 24-h period, of a chronometric mechanism of compensation for apparent solar motion. They show excellent agreement with a recently proposed model of compensation for the sun at constant (not differential) speed and they demonstrate a dependence of the speed of the chronometric mechanism on the L:D ratio in the 24-h period.
Relationship between the membrane potential of the contractile vacuole complex and its osmoregulatory activity inParamecium multimicronucleatum
Authors: Grønlien Heidi K. , Stock Christian , Aihara Marilynn S. , Allen Richard D. , Naitoh Yutaka 
Published: April 2021

SUMMARYThe electric potential of the contractile vacuole (CV) of Paramecium multimicronucleatum was measured in situ using microelectrodes,one placed in the CV and the other (reference electrode) in the cytosol of a living cell. The CV potential in a mechanically compressed cell increased in a stepwise manner to a maximal value (approximately 80 mV) early in the fluid-filling phase. This stepwise change was caused by the consecutive reattachment to the CV of the radial arms, where the electrogenic sites are located. The current generated by a single arm was approximately 1.3×10-10 A. When cells adapted to a hypotonic solution were exposed to a hypertonic solution, the rate of fluid segregation, RCVC, in the contractile vacuole complex (CVC) diminished at the same time as immunological labelling for V-ATPase disappeared from the radial arms. When the cells were re-exposed to the previous hypotonic solution, the CV potential, which had presumably dropped to near zero after the cell's exposure to the hypertonic solution, gradually returned to its maximum level. This increase in the CV potential occurred in parallel with the recovery of immunological labelling for V-ATPase in the radial arm and the resumption of RCVC or fluid segregation. Concanamycin B, a potent V-ATPase inhibitor, brought about significant decreases in both the CV potential and RCVC. We confirm that (i) the electrogenic site of the radial arm is situated in the decorated spongiome, and (ii) the V-ATPase in the decorated spongiome is electrogenic and is necessary for fluid segregation in the CVC. The CV potential remained at a constant high level(approximately 80 mV), whereas RCVC varied between cells depending on the osmolarity of the adaptation solution. Moreover, the CV potential did not change even though RCVC increased when cells adapted to one osmolarity were exposed to a lower osmolarity, implying that RCVC is not directly correlated with the number of functional V-ATPase complexes present in the CVC.
Predicting three-dimensional target motion: how archer fish determine where to catch their dislodged prey
Authors: Rossel Samuel , Corlija Julia , Schuster Stefan 
Published: April 2021

SUMMARY
On locating an insect prey on a twig above the water surface, a group of archer fish can shoot it down using powerful jets of water. The insect,dislodged by one of the shots, falls on a ballistic path towards the water surface, where it is devoured by the first fish to arrive. We report that the archer fish can predict the point where the dislodged prey will later hit the water surface and move in a straight line towards that point, thus enabling it to arrive as fast as possible. Only about 100 ms after prey is dislodged, the fish initiate a quick turn that aligns their body axis right towards where the prey will later land, and not to the actual position of the prey at that moment. In contrast to other known examples of three-dimensional target interception in man and animals, archer fish can head straight to the predicted point of catch without the need of any further visual feedback. Moreover, archer fish can predict the point of incidence of a target,regardless of the angle at which the prey takes off with respect to the initial orientation of the fish. To perform this remarkable task, archer fish extract a minimum set of independent variables that fix the point of incidence, but do not extrapolate the target's spatial trajectory.