bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Kinematics of Prey Capture in Xystreurys Liolepis: Do all Flatfish Feed Asymmetrically?
Authors: Gibb Alice C. 
Published: April 2021

ABSTRACT
Previous research has shown that one species of flatfish displays several functional asymmetries of the head and jaws during prey capture. However, it is not known whether the functional asymmetries observed for this species are common to all flatfishes. In order to determine whether functional asymmetry is present in other flatfish taxa, prey-capture behavior was examined in a species of flatfish with little cephalic morphological asymmetry, Xystreurys liolepis (Pleuronectiformes: Paralichthyidae). In addition, X. liolepis is one of a few species of flatfish in which both typical (sinistral) and reversed (dextral) individuals are commonly found. Five individuals (two dextral and three sinistral) of X. liolepis were video-taped feeding at 250 fields s−1 in order to quantify prey-capture kinematics. These data were used to test two hypotheses: (1) that typical and reversed-symmetry individuals have identical prey-capture kinematics, and (2) that X. liolepis exhibit no functional asymmetry during prey capture because they have little morphological asymmetry. Analysis of prey capture indicates that the kinematic variables measured for sinistral and dextral individuals are statistically indistinguishable. In addition, X. liolepis do not exhibit the same suite of functional asymmetries that has been found in a flatfish species with more extreme cephalic morphological asymmetry (Pleuronichthys verticalis). However, asymmetrical anterior movement of the ventral portion of the maxilla does occur in X. liolepis during mouth opening. Examination of osteological preparations and cleared and stained individuals indicates that the maxilla is asymmetrical in length in this species. A simple model indicates that the differential length of the maxilla is sufficient to explain the observed functional asymmetry during prey capture. These results suggest that certain morphological asymmetries of the jaws of flatfishes are modifications for specialized prey-capture behaviors.
Limits to Flight Energetics of Hummingbirds Hovering in Hypodense and Hypoxic Gas Mixtures
Authors: Chai Peng , Dudley Robert 
Published: April 2021

ABSTRACT
Hovering hummingbirds offer a model locomotor system for which analyses of both metabolism and flight mechanics are experimentally tractable. Because hummingbirds exhibit the highest mass-specific metabolic rates among vertebrates, maximum performance of hovering flight represents the upper limit of aerobic locomotion in vertebrates. This study evaluates the potential constraints of flight mechanics and oxygen availability on maximum flight performance. Hummingbird flight performance was manipulated non-invasively using air and gas mixtures which influenced metabolism via variable oxygen partial pressure and/or altered flight mechanics via variable air densities. Limits to the locomotor capacity of hovering ruby-throated hummingbirds (Archilochus colubris) were unequivocally indicated by aerodynamic failure in either air/helium or air/heliox mixtures. Air/helium mixtures are hypodense and hypoxic; failure to sustain hovering flight occurred at 63 % of the density of sea-level air and at an oxygen concentration of 12 %. Air/heliox mixtures are hypodense but normoxic; failure in hovering occurred at 47 % of sea-level air density. Thus, hummingbirds demonstrated considerable power reserves in hovering flight as well as hypoxic tolerance. In air/helium mixtures, hovering was limited by oxygen supply and not by flight mechanics. Birds hovering in air/helium mixtures increased their mechanical power output but not their rate of oxygen consumption. By contrast, birds hovering in air/heliox mixtures increased both mechanical performance and metabolic expenditure. Under hypoxia, hovering hummingbirds demonstrated non-negligible, but still limited, capacities for anaerobic metabolism and/or oxygen storage. Depending on the physical context, hummingbird flight performance can therefore be limited by oxygen availability or by flight aerodynamics.
Activity of Asynchronous Flight Muscle From two Bee Families During Sonication (Buzzing)
Authors: King Marcus J. , Buchmann Stephen L. , Spangler Hayward 
Published: April 2021

ABSTRACT
The indirect flight muscles of bees are used to produce a variety of actions in addition to flight, including sonication, which has a higher frequency than flight. We observed the dynamic movement of the scutum during sonication and the transition from tethered flight to sonication. During sonication, the scutum oscillated above its rest position, indicating that the conformation of the structural components of the thorax had been altered. Sonication vibrations of the thorax occurred by deformation of the scutum rather than by opening of the scutal fissure and are smaller than vibrations associated with flight. During tethered flight, the ratio of muscle activity (recorded via electromyograms) between the dorsal longitudinal muscles and the dorsoventral muscles approached 1, but during sonication the ratio was significantly higher (up to 4.0). This increase may cause the dorsal longitudinal muscles to contract further than the dorsoventral muscles and close the scutal fissure during sonication, so limiting the displacement of the wings and ‘decoupling’ them from the indirect flight muscles.
Intestinal Base Excretion in the Seawater-Adapted Rainbow Trout: a Role in Acid–Base Balance?
Authors: Wilson Rod W. , Gilmour Kathleen M. , Henry Ray P. , Wood Chris M. 
Published: April 2021

ABSTRACT
A potential role for the intestine of seawater-adapted teleosts in acid–base regulation was investigated following earlier reports of highly alkaline rectal fluids in the gulf toadfish Opsanus beta. Rectal samples taken from starved seawater-adapted rainbow trout had a high fluid pH (8.90±0.03; mean ± S.E.M., N=13) and base (HCO3−+2CO32−) content of 157±26 mequiv kg−1 (N=11). In trout fitted with rectal catheters, rectal fluid was voided at a rate of 0.47±0.11 ml kg−1 h−1 (N=8), giving a net base excretion rate of 114±15 μequiv kg−1 h−1 (N=7). Drinking rates averaged 3.12±0.48 ml kg−1 h−1 (N=8), and accounted for only 6 % of the base excreted via the intestine, indicating substantial net transport of endogenously derived base into the intestine. Rectally excreted base was approximately balanced by an equivalent efflux of net acid from non-rectal sources (possibly as NH4+ excretion via the gills).
Samples taken from four sites along the intestine revealed that the most anterior region (the pyloric intestine) was responsible for the majority of HCO3−+2CO32− accumulation. The pyloric intestine was subsequently perfused in situ to investigate possible mechanisms of base secretion. Net base fluxes were found to be dependent on luminal Cl−, 76 % stimulated by amiloride, 20 % inhibited by 10−4 mol l−1 acetazolamide, but unaffected by either 10−4 mol l− SITS or 2×10−5 mol l− DIDS. This suggests that the mechanism of base secretion within the pyloric intestine may involve a Cl−/HCO3−-ATPase. It is speculated that intestinal base secretion may play a role in facilitating osmoregulation of seawater-adapted teleosts.
Rapid Dispersal of Clustered Postsynaptic Nuclei Following Dissociation of Skeletal Muscle Fibers
Authors: Brösamle Christian , Kuffler Damien P. 
Published: April 2021

ABSTRACT
The vertebrate neuromuscular junction is a highly specialized structure containing many unique proteins and an underlying cluster of nuclei. Part of this specialization results from the expression of the genes for these proteins in nuclei clustered in the postsynaptic region. Contractile activity, as well as molecules located in the synaptic extracellular matrix (ECM), have been implicated in the induction of gene expression in these clustered nuclei. The present experiments were aimed at examining whether the presence of the synaptic ECM and presynaptic cells play a role in maintaining the clustering of the nuclei. We describe the normal distribution of nuclei clustered in the synaptic region of intact adult frog, Rana pipiens, skeletal muscle fibers and show that innervation is not required to maintain the nuclear clusters. Even after long-term (4 week) denervation, the clusters remain unchanged. Dissociation of the muscle fibers with proteases that remove ECM, Schwann cells and other satellite cells from the synaptic sites is followed by a rapid (within approximately 1.5 h) and almost complete dispersal of the clustered nuclei. Attempts to recluster the postsynaptic nuclei by the application of ECM components to muscle fibers in vitro were not successful. We propose that a factor or factors, localized in the synaptic ECM as a result of synapse formation and acting via the transmembrane or cytoplasmic domains of their respective receptors, induces the formation of a specialized cytoskeleton in the postsynaptic region that is capable of pulling in or ‘trapping’ nuclei. The removal of these factors from the ECM by proteases brings about the disorganization of the cytoskeleton and the freeing of the ‘trapped’ nuclei.
Cutaneous Respiration In Octopus Vulgaris
Authors: Madan J. J. , Wells M. J. 
Published: April 2021

ABSTRACT
The skin of Octopus vulgaris consumes considerable quantities of oxygen in vitro, averaging 4.55×10−5±1.80×10−5 ml mm−2 h−1 (mean ± S.D.), if a flow is maintained over the skin sample (N=32). The consumption is higher still in vivo, 11.36×10−5±2.73×10−5 ml mm−2 h−1 (N=8), suggesting an additional net import of oxygen through the skin when the blood system is intact. If a substantial boundary layer is allowed to develop, oxygen uptake in vitro falls to 2.09×10−5±0.56×10−5 ml mm−2 h−1 (N=15). The proportion of the animals’ total oxygen consumption that cutaneous uptake will represent must thus depend on how much of the skin is exposed and how well it is ventilated. Estimates indicate that some 41 % of the total oxygen requirement of an animal at rest might be satisfied in this manner. During exercise, with water flowing over the entire surface of the animal, cutaneous uptake will increase but is nevertheless likely to form a smaller proportion (about 33 %) of the total uptake. In an animal curled up in its den and digesting a substantial meal, cutaneous uptake could shrink to as little as 3 % of the total. Similar results were obtained in a small number of pilot experiments with a range of octopod, sepioid and teuthoid species.
Mechanisms of Tongue Protraction and Narial Closure in the Marine Toad Bufo Marinus
Authors: Nishikawa Kiisa C. , Gans Carl 
Published: April 2021

ABSTRACT
Electromyography, kinematic analysis, muscle stimulation and denervation techniques were used to investigate the muscular mechanisms of narial closure during breathing and of tongue protraction during prey capture in the marine toad Bufo marinus. Toads were video-taped during breathing and feeding under a variety of conditions: before surgery, after unilateral or bilateral denervation of the M. submentalis, and after unilateral or bilateral denervation of the Mm. genioglossus basalis and medialis. Deeply anesthetized toads were video-taped during stimulation of several cranial muscles, and electromyograms were recorded from the M. submentalis during feeding before and after its denervation. Bufo marinus differs from many other anurans in having a relatively long tongue that experiences large accelerations (&gt;31 g) during protraction. Tongue protraction occurs in two phases: an early phase during which the lingual tip moves upward and forward relative to the mandibular tip as the tongue shortens, and a later phase during which the lingual tip moves downward and forward relative to the mandibular tip as the tongue elongates under its own momentum. Relative to an external reference, the lingual tip follows a straight trajectory from mouth to prey, which depends critically upon precise coordination of tongue and jaw movements. The M. submentalis is necessary for narial closure during breathing, but is unnecessary for normal tongue protraction during feeding. In contrast, the Mm. genioglossus basalis and medialis are necessary for forward movement of the tongue pad over the symphysis. In B. marinus, a simple anatomical change (elongation of the tongue) has functional consequences (inertial elongation) that profoundly affect the mechanisms of neuromuscular control. Though seldom studied, it seems likely that morphological evolution has had a profound influence on mechanisms of motor control in animals generally.
Apparent Water Permeability As A Physiological Parameter In Crustaceans
Authors: Rasmussen Allan Dahl , Andersen Ole 
Published: April 2021

ABSTRACT
This article reviews the use of apparent water permeability (AWP) calculated from measurements of isotope-labelled water flux as a physiological estimate of whole-body water permeability in aquatic invertebrates. The rationale and practices of AWP calculations are described in an Appendix.
AWP calculations have provided a wealth of information. However, the validity of the method and therefore also of the information obtained have been questioned. Consequently, the use of AWP data in discussions of osmotic and fluid homeostatic questions in aquatic invertebrates is limited. This article reviews three decades of published experiments in which measurements of isotope-labelled water fluxes were used to estimate water permeability in aquatic invertebrates. Data on 24 species of arthropod, most of them decapod crustaceans, are presented. The combined data indicate that the results obtained by different investigators on the same species show good agreement, even though different tracers and experimental methods have been applied. When available, results from other kinds of studies were used to evaluate the results obtained using the AWP measurements. The various results demonstrate that AWP is influenced not only by natural environmental factors, such as salinity and temperature, and by anthropogenic factors, such as potentially toxic trace metals, but that it is also regulated by intrinsic factors, such as ecdysis and life cycle stage. The results obtained can often be explained as effects of components of the habitat of the animal. Accordingly, studies on variations in AWP contribute to our understanding of the different physiological strategies used by species living in a changing environment.
We conclude that calculations of AWP offer reliable, relevant physiological data in a range of crustacean species, as long as methodological limitations and uncertainties are kept in mind.
In addition, we propose some possible new ways of applying AWP calculations to marine invertebrates other than crustaceans. A major part of this review describes results already obtained for the shore crab Carcinus maenas as this species is probably the animal on which most work has been carried out. We suggest topics for future work on this species and review the possibility of using AWP in C. maenas as a biomarker of metal exposure.
Analysis of Cardiac Shunting in the Turtle Trachemys (Pseudemys) Scripta: Application of the Three Outflow Vessel Model
Authors: Ishimatsu Atsushi , Hicks James W. , Heisler Norbert 
Published: April 2021

ABSTRACT
Blood distribution within the ventricle was analysed in acutely prepared turtles Trachemys scripta by measuring the oxygen concentration and flow rates of blood in the central vessels. Pulmonary (Q̇p) and systemic (Q̇s) blood flow rates were similar when total cardiac output (Q̇tot) was below 40 ml min−1 kg−1. Above this value, increments of Q̇tot were directed to the pulmonary circuit, with Q̇s levelling off at approximately 20 ml min−1 kg−1. When Q̇tot was larger than 40 ml min−1 kg−1, the systemic circuit was almost exclusively perfused by left atrial blood and systemic venous return was almost all directed towards the lungs. Blood oxygen levels and flow rates were consistently higher in the right aorta than in the left aorta. Blood movement within the ventricle, coupled with differences in ejection timing, is probably the decisive factor determining this pattern of blood distribution in the turtle heart.
Contraction Dynamics and Power Production of Pink Muscle of the Scup (Stenotomus Chrysops)
Authors: Coughlin David J. , Zhang Guixin , Rome Lawrence C. 
Published: April 2021

ABSTRACT
Although the contribution of red muscle to sustained swimming in fish has been studied in detail in recent years, the role of pink myotomal muscle has not received attention. Pink myotomal muscle in the scup (Stenotomus chrysops) lies just medial to red muscle, has the same longitudinal fibre orientation and is recruited along with the red muscle during steady sustainable swimming. However, pink muscle has significantly faster rates of relaxation, and the maximum velocity of shortening of pink muscle (7.26±0.18 muscle lengths s−1, N=9, at 20 °C, and 4.46±0.15 muscle lengths s−1, N=6, at 10 °C; mean ± S.E.M.) is significantly faster than that of red muscle. These properties facilitate higher mass-specific maximum oscillatory power production relative to that of red muscle at frequencies similar to the tailbeat frequency at maximum sustained swimming speeds in scup. Additionally, pink muscle is found in anatomical positions in which red muscle produces very little power during swimming: the anterior region of the fish, which undergoes the lowest strain during swimming. Pink muscle produces more oscillatory power than red muscle under low-strain conditions (±2–3 %) and this may allow pink muscle to supplement the relatively low power generated by red muscle in the anterior regions of swimming scup.
The Respiratory Development of Atlantic Salmon: II. Partitioning of Oxygen Uptake Among Gills, Yolk Sac and Body Surfaces
Authors: Wells Patrick R. , Pinder Alan W. 
Published: April 2021

ABSTRACT
During post-hatch development of Atlantic salmon (Salmo salar L.), O2 uptake partitioning changes from primarily cutaneous to primarily branchial. Over 80 % of post-hatch O2 uptake was cutaneous, with the yolk sac responsible for 33 % of total O2 uptake. The well-vascularized yolk sac was a less effective gas exchanger than the unperfused skin of the body, suggesting that oxygen delivery is by direct diffusion to the tissues. Branchial O2 uptake increased quickly as gill lamellae developed, contributing 60 % of total O2 uptake before the completion of yolk resorption (body mass 0.2 g) and increasing to 69–81 % in fish weighing over 0.3 g. The area-specific O2 uptake of the skin decreased through development as skin thickness increased, while that of the gills increased from 0.10 μg h−1 mm−2 to 0.23 μg h−1 mm−2.
Partitioning of O2 uptake of the skin and gills changed in concert with changes in the partitioning of the anatomical diffusion factor (ADF, mass-specific surface area per unit diffusion distance) between skin and gills, which changed from more than 95 % to less than 10 % cutaneous; thus, ADF is a useful rough indicator of oxygen uptake potential. Caution should be used in predicting oxygen uptake potential from ADF, however, because O2 uptake per unit diffusion barrier of the yolk sac was less than half that of the general body surface, and O2 uptake per unit diffusion barrier of the gills changed dramatically over development.
Zebrafish Interphotoreceptor Retinoid-Binding Protein: Differential Circadian Expression Among Cone Subtypes
Authors: Rajendran Ramji R. , Niel Ellen E. Van , Stenkamp Deborah L. , Cunningham Lisa L. , Raymond Pamela A. , Gonzalez-Fernandez Federico 
Published: April 2021

ABSTRACT
Retinoid trafficking between the photoreceptors and pigmented epithelium is probably mediated by interphotoreceptor retinoid-binding protein (IRBP), a 124–145 kDa glycolipoprotein in mammals and amphibians. In these animals, IRBP is composed of four homologous regions (modules) 300 amino acids in length. We have determined the primary structure of zebrafish IRBP and its expression pattern by northern analysis, reverse transcriptase–polymerase chain reaction and in situ hybridization under a variety of lighting conditions. Zebrafish IRBP is half the size (66.3 kDa) of mammalian IRBP because it is composed of only two modules, similar to goldfish IRBP. The first half of the zebrafish protein is most similar to the first module of mammalian IRBP and the second half to the fourth module of mammalian IRBP. This suggests that during the evolution of the ray-finned fish (Actinopterygii), the middle two modules were lost. Each of the modules contains conserved hydrophobic domains which may form the ligand-binding pocket. The expression of zebrafish IRBP mRNA is sevenfold higher in the middle of the light period (at mid-light) than in the middle of the dark period (at mid-dark). This rhythm persists for 2 days under conditions of constant light or constant darkness, then dampens to an intermediate level by 8 days of constant conditions. At mid-light, IRBP mRNA is expressed by all cone types and to a lesser extent by the rods. At mid-dark, the mRNA is restricted to the ultraviolet-sensitive short single cones. These data suggest that IRBP expression is regulated by circadian and light-driven mechanisms that act differentially on the various photoreceptor subtypes in the zebrafish retina.