bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Organisation of the Metathoracic Femoral Chordotonal Organ in the Cricket Acheta Domesticus
Authors: Nowel M. S. , Shelton P. M. J. , Stephen R. O.
Published: April 2021

The metathoracic chordotonal organ of the cricket Acheta domesticus (Gryllidae) consists of two closely associated scoloparia situated proximally within the femur with their distal ends connected by a pair of ligaments to an apodeme arising from the tibia. The smaller scoloparium is associated with the dorsal ligament, which arises from the dorsal surface of the apodeme 150 µm from its proximal end. The larger scoloparium is attached directly to the proximal end of the apodeme by a larger ventral ligament. Both ligaments are composed of bundles of attachment cells containing densely packed microtubules. Longitudinally orientated, Acid-Fuchsin-staining fibrils are found in an extracellular matrix surrounding the individual attachment cells. Similar fibrils occur in the sheath surrounding each ligament. The fibrils are thickest and most densely packed in the sheath surrounding the ventral ligament. They are thinner and more sparsely distributed in the sheath of the dorsal ligament. The finest fibrils are found in the extracellular matrix surrounding individual attachment cells. Staining with phosphotungstic acid provides the first evidence that they are elastic. The ventral ligament also contains a spring-like cuticular core arising as a proximal extension of the apodeme. As femoro-tibial angle changes, the cuticular core changes in length, shortening with tibial extension and lengthening with flexion. Ventral ligament attachment cells terminate at different levels along the cuticular core. This arrangement provides a new possible mechanism for differential sensitivity of the sensory neurones associated with the attachment cells.
Sound Pressure Transformation at the Pinna of Mus Domesticus
Authors: Chen Qi-Cai , Cain David , Jen Philip H.-S.
Published: April 2021

Sound pressure transformation properties at the pinna of laboratory mice Mus domesticus were studied by measuring the sound pressure level of a continuous tone at a series of frequencies at the tympanic membrane as a function of the position of a sound source under free-field stimulation conditions. The spectral transformation, the interaural spectral difference, the isopressure contours and the interaural pressure difference contours were plotted. Sound pressure transformation functions showed some prominent spectral notches throughout the frequency range tested (10–80 kHz). However, the notch frequency did not appear to be systematically related to sound direction. The study of interaural pressure difference demonstrated that, when delivered from some angles within the ipsilateral frontal hemisphere, the sound pressure at the tympanic membrane of certain frequencies may be lower than that determined at the corresponding contralateral angles. For each sound frequency tested, there was an angle (the acoustic axis) within the ipsilateral frontal hemisphere from which the delivered sound reached a maximal pressure level at the tympanic membrane. However, the acoustic axis often changed to a new angle after removal of the ipsilateral pinna. In addition, sound delivered from the acoustic axis did not always generate a maximal pressure transformation. The isopressure contours determined within 2–5 dB of the maximal pressure were circumscribed, and their contained angular areas were found to decrease with increasing sound frequency. The 2 dB maximal pressure area may appear at more than one angular area for some test frequencies. Removal of the ipsilateral pinna or modification of pinna posture expanded isopressure contours irregularly and split the 2 dB maximal pressure area into several parts. The sound pressure difference determined between the angles of maximal and minimal sound pressure (the maximal directionality) increased with sound frequency regardless of pinna posture. Acoustic gain of the pinna at the acoustic axis reached 6–12 dB, depending upon sound frequency. However, the pinna gain was not always maximal at the acoustic axis for a given frequency.
The Knowledge Base of Bee Navigation
Authors: Menzel Randolf , Geiger Karl , Chittka Lars , Joerges Jasdan , Kunze Jan , Müller Uli
Published: April 2021

Navigation in honeybees is discussed against the background of the types of memories employed in the navigational task. Two questions are addressed. Do bees have goal-specific expectations, and when are novel routes travelled? Expectations are deduced from (1) context stimuli as determinants for local cue memories, (2) landmark-dependent path integration, (3) sequential learning of landmarks, and (4) motivation-and context-dependent memory retrieval. Novel routes are travelled under two conditions: (1) goal-cue-based piloting and (2) integration of simultaneously activated vector memories. Our data do not support the conclusion that memory integration in bees is organised by a cognitive map. The assumption of purely separate memories that are only retrieved according to the chain of events during navigational performance also appears to be inadequate. We favour the view that multiple memories are integrated using external and internal sources of information. Such configural memories lead to both specific expectations and novel routes.
Honeybee Navigation En Route to the Goal: Visual Flight Control and Odometry
Authors: Srinivasan M. V. , Zhang S. W. , Lehrer M. , Collett T. S.
Published: April 2021

Recent research has uncovered a number of different ways in which bees use cues derived from optic flow for navigational purposes. The distance flown to a food source is gauged by integrating the apparent motion of the visual world that is experienced en route. In other words, bees possess a visually driven ‘odometer’ that is robust to variations in wind load and energy expenditure. Bees flying through a tunnel maintain equidistance to the flanking walls by balancing the apparent speeds of the images of the walls. This strategy enables them to negotiate narrow passages or to fly between obstacles. The speed of flight in a tunnel is controlled by holding constant the average image velocity as seen by the two eyes. This avoids potential collisions by ensuring that the bee slows down when flying through narrow passages. Bees landing on a horizontal surface hold constant the image velocity of the surface as they approach it. This automatically ensures that flight speed decreases with altitude and is close to zero at touchdown. The movement-sensitive mechanisms underlying these various behaviours seem to be different, qualitatively as well as quantitatively, from those mediating the well-investigated optomotor response.
The flexible migratory orientation system of the savannah sparrow (Passerculus sandwichensis)
Authors: Able K , Able M
Published: April 2021

The orientation system of the Savannah sparrow (Passerculus sandwichensis) is typical of nocturnal migrant passerine birds. It is based on a system of interacting compass senses: magnetic, star, polarized light and, perhaps, sun compasses. The magnetic compass capability develops in birds that have never seen the sky, but the preferred direction of magnetic orientation may be calibrated by celestial rotation (stars at night and polarized skylight patterns during the day). This ability to recalibrate magnetic orientation persists throughout life and enables the bird to compensate for variability in magnetic declination that may be encountered as it migrates. The polarized light compass may be manipulated by exposing young birds to altered patterns of skylight polarization. There is some evidence that the magnetic field may be involved in calibration of the polarized light compass. In short-term orientation decision-making during migration, visual information at sunset overrides both stars and magnetic cues, and polarized skylight is the relevant stimulus in dusk orientation. The star pattern compass seems to be of little importance. This extremely flexible orientation system enables the birds to respond to spatial and temporal variability in the quality and availability of orientation information.
Visualization of Cement Exocytosis in the Cypris Cement Gland of the Barnacle Megabalanus Rosa
Authors: Okano Keiju , Shimizu Katsuhiko , Satuito Cyril Glenn , Fusetani Nobuhiro
Published: April 2021

Cementation to substrata during permanent attachment concludes the planktonic larval phase in many sessile marine invertebrates, including barnacles. However, the neural control and the mechanism of cement secretion from cement organs are poorly understood. In the present study, using isolated cement glands from cyprids of Megabalanus rosa, we have visualized cement secretion and demonstrated the stimulatory effect of dopamine and noradrenaline on such secretion. The abrupt disappearance of secretory granules and subsequent omega-figure formation indicated that exocytosis was the major mode of cement secretion. Exocytosis was localized at the apical surface of cement-secreting cells and lasted for over 30 min. Dopamine and noradrenaline also activated the directional transport of secretory granules to the sites of exocytosis. Glyoxylic acid staining provided histochemical evidence for catecholaminergic innervation to the cement glands. These results suggest that gradual, localized exocytotic secretion of cement triggered by catecholaminergic neurones is a key mechanism during permanent attachment by barnacle cyprids.
Activation of Apical P2U Purine Receptors Permits Inhibition of Adrenaline-Evoked Cyclic Amp Accumulation in Cultured Equine Sweat Gland Epithelial Cells
Authors: Wilson S. M. , Rakhit S. , Murdoch R. , Pediani J. D. , Elder H. Y. , Baines D. L. , Ko W. H. , Wong P. Y. D.
Published: April 2021

Experiments were undertaken using cultured equine sweat gland epithelial cells that express purine receptors belonging to the P2U subclass which allow the selective agonist uridine triphosphate (UTP) to increase the concentration of intracellular free Ca2+ ([Ca2+]i). Experiments using pertussis toxin (Ptx), which inactivates certain guanine-nucleotide-binding proteins (G-proteins), showed that this response consisted of Ptx-sensitive and Ptx-resistant components, and immunochemical analyses of the G-protein α subunits present in the cells showed that both Ptx-sensitive (αi1–3) and Ptx-resistant (αq/11) G-proteins were expressed. P2U receptors may, therefore, normally activate both of these G-protein families. Ptx-sensitive, αi2/3 subunits permit inhibitory control of adenylate cyclase, and UTP was shown to cause Ptx-sensitive inhibition of adrenaline-evoked cyclic AMP accumulation, suggesting that the receptors activate Gi2/3. Experiments using cells grown on permeable supports suggested that P2U receptors became essentially confined to the apical membrane in post-confluent cultures. Polarised epithelia may, therefore, express apical P2U receptors which influence two centrally important signal transduction pathways. It is highly improbable that these receptors could be activated by nucleotides released from purinergic nerves, but they may be involved in the autocrine regulation of epithelial function.
Graviresponses in Paramecium Biaurelia Under Different Accelerations: Studies on the Ground and In Space
Authors: Hemmersbach Ruth , Voormanns Regine , Häder Donat-P.
Published: April 2021

Behavioural responses to different accelerations below 1 g and up to 5 g were investigated in Paramecium biaurelia by using a centrifuge microscope on Earth and in space during a recent space flight. Increased stimulation (hypergravity) enhanced the negative gravitactic and the gravikinetic responses in Paramecium biaurelia within seconds. Cells did not adapt to altered gravitational conditions. Repetitive stimulation did not change the graviresponses. The minimum acceleration found to induce gravitaxis was between 0.16 and 0.3 g.
The Effect of Altering Pulmonary Blood Flow on Pulmonary Gas Exchange in the Turtle Trachemys (Pseudemys) Scripta
Authors: Hopkins Susan R. , Wang Tobias , Hicks James W.
Published: April 2021

In resting reptiles, the of pulmonary venous return (; left atrial blood) may be 20 mmHg (1 mmHg=0.1333 kPa) lower than the of gas in the lung. This level of is considerably higher than that observed in resting mammals and birds and results from ventilation–perfusion heterogeneity, pulmonary diffusion limitation and intrapulmonary shunting. However, the relative contribution of each of these factors is unknown. Many reptiles, particularly chelonians, exhibit an intermittent ventilation pattern where pulmonary blood flow (Q̇l) increases during the ventilatory periods and, therefore, we hypothesized that matching would improve with increasing Q̇l. We applied the multiple inert gas elimination technique in anaesthetized turtles at 22 °C. Turtles were continuously ventilated at a rate of 140 ml kg−1 min−1, equivalent to the rate of ventilation within a ventilatory period. Trace amounts of six inert gases were infused through the jugular vein. Blood samples from the pulmonary artery and the left atrium and mixed expired gases were collected for analysis. Q̇l was reduced by a factor of six (low flow) using a vascular occluder placed around the common pulmonary artery or increased by a factor of two (high flow) through bolus injection of adrenaline. heterogeneity was significantly reduced with increasing pulmonary blood flow (P<0.05). Consistent with these changes, the effective lung–pulmonary artery difference was reduced (P<0.05) from 58±16 mmHg to 29±5 mmHg (means ± S.E.M.) and increased significantly (P<0.05) from 88±17 mmHg (low flow) to 120±14 mmHg (high flow). There was evidence of pulmonary diffusion limitation under all conditions, which was unchanged with increasing blood flow. These findings suggest that increased pulmonary blood flow during a ventilatory period results in both temporal and spatial matching of ventilation and perfusion, without altering pulmonary diffusion limitation.
1H- and 31P-Nuclear Magnetic Resonance Studies of L-Lactate Transport in Isolated Muscle Fibers from the Spiny Lobster Panulirus Argus
Authors: Kinsey Stephen T. , Ellington W. Ross
Published: April 2021

Proton (1H) and phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy were used to investigate the mode of transport of L-lactate across the plasma membranes of the abdominal extensor muscles of the spiny lobster Panulirus argus. Individual fibers or bundles of 2–3 fibers were superfused in a dual-tuned (1H, 31P) microsolenoid NMR probe. 1H-NMR spectra were diffusion-weighted, which eliminated the signal contribution of the fast-flowing extracellular lactate but retained that of intracellular lactate. Well-resolved intracellular lactate signals could be acquired at 15 s intervals, permitting estimation of initial velocities (Vi) of influx and efflux during loading/unloading of muscle fibers. 31P-NMR spectra were acquired to assess cellular energy status and intracellular pH. Transport results showed that Vi values for influx and efflux were a linear function of total lactate concentration, displaying no saturation effects. The rate of lactate influx was enhanced by increasing the concentration of the free acid by altering the superfusate pH. Vi values for influx and efflux of D- and L-lactate were identical. Finally, traditional inhibitors of monocarboxylate and/or anion transport had no effect on influx/efflux of lactate from these cells. The above results strongly suggest that the primary mode of lactate transport is by passive diffusion. These cells appear to lack a monocarboxylate transporter, which may be related to the apparent absence of organ-specific compartmentation of lactate metabolism in crustaceans.
Pectoral Fin Locomotion in the Striped Surfperch: I. Kinematic Effects of Swimming Speed and Body Size
Authors: Drucker Eliot G. , Jensen Jeffrey S.
Published: April 2021

Swimming trials at increasing velocity were used to determine the effects of steady swimming speed on pectoral fin kinematics for an ontogenetic series of striped surfperch Embiotoca lateralis, ranging from 6 to 23 cm in standard length (SL). The fin stroke cycle consisted of a propulsive period, the duration of fin abduction and adduction, and a ‘refractory’ period, during which the fin remained adducted against the body. Pectoral fin-beat frequency (fp) measured as the inverse of the entire stride period, as in past studies, increased curvilinearly with speed. Frequency, calculated as the reciprocal of the propulsive period alone, increased linearly with speed, as shown previously for tail-beat frequency of fishes employing axial undulation. Fin-beat amplitude, measured as the vertical excursion of the pectoral fin tip during abduction, increased over a limited range of low speeds before reaching a plateau at 0.35–0.40 SL. Pectoral fin locomotion was supplemented by intermittent caudal fin undulation as swimming speed increased. At the pectoral–caudal gait transition speed (Up−c), frequency and amplitude attained maxima, suggesting that the fin musculature reached a physiological limit. The effects of body size on swimming kinematics differed according to the method used for expressing speed. At a given absolute speed, small fish used higher stride frequencies and increased frequency at a faster rate than large fish. In contrast, the relationship between fp and length-specific speed (SL s−1) had a greater slope for large fish and crossed that for small fish at high speeds. We recommend that comparisons across size be made using speeds expressed as a percentage of Up−c, at which kinematic variables influencing thrust are size-independent.
The Kinematics of Prey Capture in Xystreurys Liolepis: Do all Flatfish Feed Asymmetrically?
Authors: Gibb Alice C.
Published: April 2021

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

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

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

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

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

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

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 (>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

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

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

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

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

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.
Flight Kinematics of Black-Billed Magpies and Pigeons Over a Wide Range of Speeds
Authors: Tobalske Bret W. , Dial Kenneth P.
Published: April 2021

To investigate how birds that differ in morphology change their wing and body movements while flying at a range of speeds, we analyzed high-speed (60 Hz) video tapes of black-billed magpies (Pica pica) flying at speeds of 4–14 m s-1 and pigeons (Columba livia) flying at 6–20 m s-1 in a wind-tunnel. Pigeons had higher wing loading and higher-aspect-ratio wings compared with magpies. Both species alternated phases of steady-speed flight with phases of acceleration and deceleration, particularly at intermediate flight speeds. The birds modulated their wingbeat kinematics among these phases and frequently exhibited non-flapping phases while decelerating. Such modulation in kinematics during forward flight is typical of magpies but not of pigeons in the wild. The behavior of the pigeons may have been a response to the reduced power costs for flight in the closed wind-tunnel relative to those for free flight at similar speeds. During steady-speed flight, wingbeat frequency did not change appreciably with increasing flight speed. Body angle relative to the horizontal, the stroke-plane angles of the wingtip and wrist relative to the horizontal and the angle describing tail spread at mid-downstroke all decreased with increasing flight speed, thereby illustrating a shift in the dominant function of wing flapping from weight support at slow speeds to positive thrust at fast speeds. Using wingbeat kinematics to infer lift production, it appeared that magpies used a vortex-ring gait during steady-speed flight at all speeds whereas pigeons used a vortex-ring gait at 6 and 8 m s-1, a transitional vortex-ring gait at 10 m s-1, and a continuous-vortex gait at faster speeds. Both species used a vortex-ring gait for acceleration and a continuous-vortex gait or a non-flapping phase for deceleration during flight at intermediate wind-tunnel speeds. Pigeons progressively flexed their wings during glides as flight speed increased but never performed bounds. Wingspan during glides in magpies did not vary with flight speed, but the percentage of bounds among non-flapping intervals increased with speed from 10 to 14 m s-1. The use of non-flapping wing postures seemed to be related to the gaits used during flapping and to the aspect ratio of the wings. We develop an ‘adverse-scaling’ hypothesis in which it is proposed that the ability to reduce metabolic and mechanical power output using flap-bounding flight at fast flight speeds is scaled negatively with body mass. This represents an alternative to the ‘fixed-gear’ hypothesis previously suggested by other authors to explain the use of intermittent flight in birds. Future comparative studies in the field would be worthwhile, especially if instantaneous flight speeds and within-wingbeat kinematics were documented; new studies in the laboratory should involve simultaneous recording of wing kinematics and aerodynamic forces on the wing.
Olfactory Responses Of A Euryhaline Fish, The Rainbow Trout: Adaptation Of Olfactory Receptors To Sea Water And Salt-Dependence Of Their Responses To Amino Acids
Authors: Shoji Takayuki , Fujita Ken-Ichi , Furihata Emiko , Kurihara Kenzo
Published: April 2021

Salmonid fishes are able to survive in both fresh water and sea water. Concentrations of NaCl in fresh water and sea water are 0.5 and 493 mmol l-1, respectively, and, hence, salt concentrations in the medium at the olfactory epithelium are greatly changed when the fish migrate between fresh water and sea water. We used the rainbow trout, which is a salmonid fish, to examine the adaptation mechanisms of the olfactory receptors to high concentrations of salts in sea water. Application of sea water to the olfactory epithelium elicited only a very small response in the olfactory nerve, but 500 mmol l-1 NaCl elicited a large response which did not adapt to a spontaneous level with time. It is considered that the olfactory nerve becomes fatigued when the olfactory epithelium is exposed to 500 mmol l-1 NaCl for long periods. We found that the presence of 10 mmol l-1 Ca2+ in sea water inhibited the response to 500 mmol l-1 NaCl, suggesting that Ca2+ in sea water is essential for adaptation of the olfactory receptors to sea water. In the second part of the study, we examined whether the olfactory nerve responses to amino acids, potent stimulants for fish, were altered between fresh water and sea water. The magnitudes of the responses to the six amino acids examined were similar in artificial pond water and artificial sea water, indicating that a large change in NaCl concentration between fresh and sea water does not affect the olfactory nerve responses to amino acids. We used fish reared in fresh water and fish acclimated to sea water and obtained similar results. It was concluded that the tolerance of the olfactory receptors for large changes in osmotic pressure is not acquired while fish are maintained in fresh or sea water, but that the receptors of these euryhaline fish naturally provide the tolerance.
Membrane Responses Evoked By Organic Buffers In Identified Leech Neurones
Authors: Schmidt Joachim , Mangold Claudia , Deitmer Joachim W.
Published: April 2021

Using single-electrode current-clamp and two-electrode voltage-clamp, different identified neurones of the leech (Hirudo medicinalis L.) were shown to hyperpolarize, or to exhibit outward currents (usually >2 nA), during bath application of the organic buffers Mops, Pipes and Mes (10 mmol l−1). Tris and Hepes had little or no effect on the membrane properties of neurones when they were added to a bathing saline buffered by CO2–HCO3− at a constant pH of 7.4.

Outward currents evoked by buffers obtained from two suppliers, Roth and Sigma, were not significantly different, except in the case of Pipes. Steady-state currents evoked by Pipes supplied by Roth were eightfold larger than steady-state currents evoked by Pipes from Sigma. A transient current peak always present in responses evoked by Pipes from Roth was never present in responses evoked by Pipes from Sigma.

Outward currents evoked by buffers were due to a conductance increase and appeared to be carried by Cl−.

In low-Cl− saline, hyperpolarizations evoked by Mops in Retzius cells were reduced. When Cl− was injected into heart motor neurones, the hyperpolarizations evoked by Mops reversed. Tetraethylammonium (TEA+) injected into heart interneurones did not block Mops-evoked hyperpolarizations.

Mops-evoked outward currents in Retzius cells were partially blocked by d-tubocurarine and bicuculline methiodide, and the latter also partially blocked Mops-evoked hyperpolarizations in HE cells. Since d-tubocurarine partially blocked acetylcholine-evoked Cl− currents in Retzius cells and bicuculline methiodide partially blocked carbachol-evoked hyperpolarizations in HE cells, Mops appears to act on the cholinergic receptors of these neurones by mediating a Cl− conductance.
Is Mammary Output Capacity Limiting to Lactational Performance in Mice?
Authors: Hammond Kimberly A. , Lloyd K. C. Kent , Diamond Jared
Published: April 2021

Using lactation in mice as a model, we sought to determine whether ceilings on sustained energy expenditure reside in the capacities of energy-acquiring and input organs (such as the intestine) or of energy-expending and output organs (such as the mammary glands). To distinguish between these possibilities experimentally, we surgically varied the teat number of lactating mother mice while simultaneously varying their litter size. The energy burden on each teat (i.e. the pup/teat ratio) could thus be varied independently of the energy burden (i.e. litter size) on the mother herself or on her intestine. At each teat number, pup mass proved to be maximal at intermediate litter sizes. At a given pup/teat ratio, mothers with five teats weaned pups no larger than the pups of normal (10-teat) mothers, even though the total energy burden on the former mothers was only half as large. Mothers with only two teats could not wean any pups. Litter size controlled maternal food intake, which in turn controlled intestinal mass and nutrient uptake capacity. Disproportionately high food intake for the smallest litters appears to reflect capital start-up costs of lactation. Pup mass is evidently limited by inadequate suckling stimulation of mammary glands.