bluuebunny/crossref_metadata_2025 huggingface dataset:
A Hydrodynamic Analysis of Fish Swimming Speed: Wake Structure and Locomotor Force in Slow and Fast Labriform Swimmers
Authors: Drucker Eliot G. , Lauder George V.
Published: April 2021

Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement of fluid velocity and estimation of wake momentum and mechanical forces for locomotion. We investigate the structure and strength of the wake in three dimensions to determine how hydrodynamic force varies in two species that differ markedly in maximum swimming speed. Black surfperch (Embiotoca jacksoni) and bluegill sunfish (Lepomis macrochirus) swim at low speeds using their pectoral fins exclusively, and at higher speeds switch to combined pectoral and caudal fin locomotion. E. jacksoni can swim twice as fast as similarly sized L. macrochirus using the pectoral fins alone. The pectoral fin wake of black surfperch at all speeds consists of two distinct vortex rings linked ventrally. As speed increases from 1.0 to 3.0 L s−1, where L is total body length, the vortex ring formed on the fin downstroke reorients to direct force increasingly downstream, parallel to the direction of locomotion. The ratio of laterally to downstream-directed force declines from 0.93 to 0.07 as speed increases. In contrast, the sunfish pectoral fin generates a single vortex ring per fin beat at low swimming speeds and a pair of linked vortex rings (with one ring only partially complete and attached to the body) at maximal labriform speeds. Across a biologically relevant range of swimming speeds, bluegill sunfish generate relatively large lateral forces with the paired fins: the ratio of lateral to downstream force remains at or above 1.0 at all speeds. By increasing wake momentum and by orienting this momentum in a direction more favorable for thrust than for lateral force, black surfperch are able to swim at twice the speed of bluegill sunfish using the pectoral fins. In sunfish, without a reorientation of shed vortices, increases in power output of pectoral fin muscle would have little effect on maximum locomotor speed. We present two hypotheses relating locomotor stability, maneuverability and the structure of the vortex wake. First, at low speeds, the large lateral forces exhibited by both species may be necessary for stability. Second, we propose a potential hydrodynamic trade-off between speed and maneuverability that arises as a geometric consequence of the orientation of vortex rings shed by the pectoral fins. Bluegill sunfish may be more maneuverable because of their ability to generate large mediolateral force asymmetries between the left- and right-side fins.
Patterns of Cardiovascular and Ventilatory Response to Elevated Metabolic States in the Lizard Varanus Exanthematicus
Authors: Hicks James W. , Wang Tobias , Bennett Albert F.
Published: April 2021

The principal function of the cardiopulmonary systemis the precise matching of O2 and CO2 transport to the metabolic requirements of different tissues. In som e ecothermic vertebrates (amphibians and reptiles), increases dramatically following feeding. Factorial increments in range from 1.7 to 44 times above resting rates, and in some cases approaches or even exceeds values measured during physical activity. There is virtually no information on the cardiopulmonary response during the postprandial period in these animals or how the pattern of cardiopulmonary support compares with that during activity. In our experiments, pulmonary ventilation , heart rate (fH), systemic blood flow (Q̇sys), rate of oxygen consu mption and rate of carbon dioxide production were measured at 35 °C in the lizard Varanus exanthematicus for 24 h prior to the ingestion of meals of various sizes and measured continuously for up to 72 h during the postprandial period. The results of this study were compared with previously published values for treadmill exercise in the same experimental animals. The change in fH and stroke volume (VS) for a given increment in did not differ during exercise and digestion. In contrast, the ventilatory response was very dependent on the nature of the elevated metabolic state. During digestion, an increase in resulted in a relative hypoventilation in comparison with resting values, whereas hyperventilation characterized the response during activity. During exercise, breathing frequency (f) increased 10-to 40-fold above resting values accompanied by large reductions in tidalvolume (VT). In contrast, postprandial increases in resulted in relatively minor changes in f and VT almost doubled. These results indicate that, in these lizards, the cardiac response to elevated is stereotyped, the response being predictable irrespective of the source of the metabolic increment. In contrast, the ventilatory response is flexible and state-dependent, not only in pattern but also in its frequency and volume components.
Broad Oxygen Tolerance in the Nematode Caenorhabditis Elegans
Authors: Voorhies Wayne A. Van , Ward Samuel
Published: April 2021

This study examined the effects of oxygen tensions ranging from 0 to 90 kPa on the metabolic rate (rate of carbon dioxide production), movement and survivorship of the free-living soil nematode Caenorhabditis elegans. C. elegans requires oxygen to develop and survive. However, it can maintain a normal metabolic rate at oxygen levels of 3.6 kPa and has near-normal metabolic rates at oxygen levels as low as 2 kPa. The ability to withstand low ambient oxygen levels appears to be a consequence of the small body size of C. elegans, which allows diffusion to supply oxygen readily to the cells without requiring any specialized respiratory or metabolic adaptations. Thus, the small size of this organism pre-adapts C. elegans to living in soil environments that commonly become hypoxic. Movement in C. elegans appears to have a relatively minor metabolic cost. Several developmental stages of C. elegans were able to withstand up to 24 h of anoxia without major mortality. Longer periods of anoxia significantly increased mortality, particularly for eggs. Remarkably, long-term exposure to 100 % oxygen had no effect on the metabolic rate of C. elegans, and populations were able to survive for a least 50 generations in 100 % (90 kPa) oxygen. Such hyperoxic conditions are fatal to most organisms within a short period.
Direct Determination of the Kinetics of Oxygen Diffusion to the Photocytes of a Bioluminescent Elaterid Larva, Measurement of Gas- and Aqueous-Phase Diffusional Barriers and Modelling of Oxygen Supply
Authors: Timmins Graham S. , Bechara Etelvino J. H. , Swartz Harold M.
Published: April 2021

We describe the development and use of a direct kinetic technique to determine the time taken for oxygen to diffuse from the external environment into the light-producing cells (photocytes) in the prothorax of bioluminescent larvae of Pyrearinus termitilluminans. This was achieved by measuring the time course of the pseudoflash induced through sequential anoxia followed by normoxia. We have also determined the separate times taken for this oxygen diffusion in gaseous and tissue (predominantly aqueous) phases by using helium and nitrogen as the carrier gas. Of the total time taken for diffusion, that in the gas phase required 613±136 ms (mean ± S.E.M., N=5) whilst that in the aqueous phase required 1313±187 ms. These values imply pathlengths of diffusion in the gaseous and aqueous phases of 4.80×10−3±0.53×10−3 and 8.89×10−5±0.61×10−5 m, respectively. In addition, the pathlength of gas-phase diffusion was used to derive a parameter relating to the tortuosity of the tracheal system. These values, together with those obtained upon bioluminescent oxygen consumption, have been used to model oxygen supply to the photocyte. From these studies, it would also appear that the modulation of tracheolar fluid levels might be a significant mechanism of control of tissue oxygen levels in at least some insects.
Responses of Anterior Lateral Line Afferent Neurones to Water Flow
Authors: Voigt Rainer , Carton Alexander G. , Montgomery John C.
Published: April 2021

The mechanoreceptive lateral line system detects hydrodynamic stimuli and plays an important role in a number of types of fish behaviour, including orientation to water currents. The lateral line is composed of hair cell receptor organs called neuromasts that occur as superficial neuromasts on the surface of the skin or canal neuromasts located in subepidermal canals. Both are innervated by primary afferents of the lateral line nerves. Although there have been extensive studies of the response properties of lateral line afferents to vibrating sources, their response to water flow has not been reported. In this study, we recorded extracellularly from anterior lateral line afferents in the New Zealand long-fin eel Anguilla dieffenbachii while stimulating the eel with unidirectional water flows at 0.5–4 cm s−1. Of the afferents, 80 % were flow-sensitive to varying degrees, the response magnitude increasing with flow rate. Flow-sensitive fibres gave non-adapting tonic responses, indicating that these fibres detect absolute flow velocity. Further studies are needed to confirm whether flow-sensitive and flow-insensitive fibres correlate with superficial and canal neuromasts, respectively.
Geographic and Altitudinal Variation in Water Balance And Metabolic Rate in a California Grasshopper, Melanoplus Sanguinipes
Authors: Rourke Bryan C.
Published: April 2021

The importance of respiratory patterns and the physical properties of cuticular lipids to insect water balance were investigated in natural populations of the grasshopper Melanoplus sanguinipes. I specifically test the hypotheses that patterns of discontinuous ventilation affect water loss and that increased amounts and melting points of cuticular lipid reduce water loss. Using flow-through respirometry, rates of water loss and carbon dioxide release from grasshoppers were quantified at 25, 35 and 42 °C. Populations displayed substantial variation, with high-elevation populations exhibiting the greatest water loss and metabolic rates. Behavior leading to discontinuous gas exchange was observed in several populations, but its occurrence decreased dramatically at high temperatures and was not correlated with a reduction in the rate of water loss. The amount and melting point of cuticular lipids were determined for each individual using gas chromatography and Fourier-transform infrared spectroscopy. Increased amounts and higher melting points of cuticular lipids were strongly correlated with lower rates of water loss in populations. I show that discontinuous gas exchange is unlikely to be a mechanism for reducing water loss in these insects and that the lipid properties are primarily responsible for variation in overall water loss rates.
Asynchronous Muscle: A Primer
Authors: Josephson Robert K. , Malamud Jean G. , Stokes Darrell R.
Published: April 2021

The asynchronous muscles of insects are characterized by asynchrony between muscle electrical and mechanical activity, a fibrillar organization with poorly developed sarcoplasmic reticulum, a slow time course of isometric contraction, low isometric force, high passive stiffness and delayed stretch activation and shortening deactivation. These properties are illustrated by comparing an asynchronous muscle, the basalar flight muscle of the beetle Cotinus mutabilis, with synchronous wing muscles from the locust, Schistocerca americana. Because of delayed stretch activation and shortening deactivation, a tetanically stimulated beetle muscle can do work when subjected to repetitive lengthening and shortening. The synchronous locust muscle, subjected to similar stimulation and length change, absorbs rather than produces work.
Relationships Between Body Mass, Motor Output and Flight Variables During Free Flight of Juvenile and Mature Adult Locusts, Schistocerca Gregaria
Authors: Fischer Hanno , Kutsch Wolfram
Published: April 2021

Little information is available about how the adult locust flight system manages to match the aerodynamic demands that result from an increase in body mass during postmoult maturation. In Schistocerca gregaria of both sexes, flight variables, including flight speed, ascent angle and body angle, were investigated under closed-loop conditions (i.e. during free flight) as a function of adult maturation. Motor patterns were examined by telemetric electromyography in juvenile and adult mature animals of both sexes. Functional relationships between particular flight variables were investigated by additional loading of the animals and by reductions in wing area. The results indicate that an increase in flight speed as the flight system matures enables it to match the aerodynamic demands resulting from increases in body mass. Furthermore, the data suggest that this postmoult increase in flight speed is not simply a consequence of the increase in wingbeat frequency observed during maturation. The instantaneous body angle during flight is controlled mainly by aerodynamic output from the wings. In addition, the mean body angle decreases during maturation in both sexes, and this may play an important part in the directional control of the resultant flight force vector.
In Vivo Demonstration of Load-Induced Fluid Flow in the Rat Tibia and Its Potential Implications For Processes Associated With Functional Adaptation
Authors: Tate M.L. Knothe , Steck R. , Forwood M. R. , Niederer P.
Published: April 2021

Load-induced extravascular fluid flow has been postulated to play a role in mechanotransduction of physiological loads at the cellular level. Furthermore, the displaced fluid serves as a carrier for metabolites, nutrients, mineral precursors and osteotropic agents important for cellular activity. We hypothesise that load-induced fluid flow enhances the transport of these key substances, thus helping to regulate cellular activity associated with processes of functional adaptation and remodelling. To test this hypothesis, molecular tracer methods developed previously by our group were applied in vivo to observe and quantify the effects of load-induced fluid flow under four-point-bending loads. Preterminal tracer transport studies were carried out on 24 skeletally mature Sprague Dawley rats. Mechanical loading enhanced the transport of both small-and larger-molecular-mass tracers within the bony tissue of the tibial mid-diaphysis. Mechanical loading showed a highly significant effect on the number of periosteocytic spaces exhibiting tracer within the cross section of each bone. For all loading rates studied, the concentration of Procion Red tracer was consistently higher in the tibia subjected to pure bending loads than in the unloaded, contralateral tibia. Furthermore, the enhancement of transport was highly site-specific. In bones subjected to pure bending loads, a greater number of periosteocytic spaces exhibited the presence of tracer in the tension band of the cross section than in the compression band; this may reflect the higher strains induced in the tension band compared with the compression band within the mid-diaphysis of the rat tibia. Regardless of loading mode, the mean difference between the loaded side and the unloaded contralateral control side decreased with increasing loading frequency. Whether this reflects the length of exposure to the tracer or specific frequency effects cannot be determined by this set of experiments. These in vivo experimental results corroborate those of previous ex vivo and in vitro studies. Strain-related differences in tracer distribution provide support for the hypothesis that load-induced fluid flow plays a regulatory role in processes associated with functional adaptation.
Ontogenetic Scaling of Burrowing Forces in the Earthworm Lumbricus Terrestris
Authors: Quillin Kim J.
Published: April 2021

In hydrostatic skeletons, it is the internal fluid under pressure surrounded by a body wall in tension (rather than a rigid lever) that enables the stiffening of the organism, the antagonism of muscles and the transmission of force from the muscles to the environment. This study examined the ontogenetic effects of body size on force production by an organism supported with a hydrostatic skeleton. The earthworm Lumbricus terrestris burrows by forcefully enlarging crevices in the soil. I built a force-measuring apparatus that measured the radial forces as earthworms of different sizes crawled through and enlarged pre-formed soil burrows. I also built an apparatus that measured the radial and axial forces as earthworms of different sizes attempted to elongate a dead-end burrow. Earthworms ranging in body mass mb from hatchlings (0.012 g) to adults (8.9 g) exerted maximum forces (F, in N) during active radial expansion of their burrows (F=0.32mb0.43) and comparable forces during axial elongation of the burrow (F=0.26mb0.47). Both these forces were almost an order of magnitude greater than the radial anchoring forces during normal peristalsis within burrows (F=0.04mb0.45). All radial and axial forces scaled as body mass raised to the 2/5 power rather than to the 2/3 power expected by geometric similarity, indicating that large worms exert greater forces than small worms on an absolute scale, but the difference was less than predicted by scaling considerations. When forces were normalized by body weight, hatchlings could push 500 times their own body weight, while large adults could push only 10 times their own body weight.
Durophagy in Sharks: Feeding Mechanics of the Hammerhead Sphyrna Tiburo
Authors: Wilga Cheryl D. , Motta Philip J.
Published: April 2021

This study investigates the motor pattern and head movements during feeding of a durophagus shark, the bonnethead Sphyrna tiburo, using electromyography and simultaneous high-speed video. Sphyrna tiburo feeds almost exclusively on hard-shelled crabs, with shrimp and fish taken occasionally. It captures crabs by ram feeding, then processes or reduces the prey by crushing it between molariform teeth, finally transporting the prey by suction for swallowing. The prey-crushing mechanism is distinct from that of ram or bite capture and suction transport. This crushing mechanism is accomplished by altering the duration of jaw adductor muscle activity and modifying jaw kinematics by the addition of a second jaw-closing phase. In crushing events, motor activity of the jaw adductor muscles continues (biting of the prey occurs as the jaws close and continues after the jaws have closed) throughout a second jaw-closing phase, unlike capture and transport events during which motor activity (biting) ceases at jaw closure. Sphyrna tiburo is able to take advantage of a resource (hard prey) that is not readily available to most sharks by utilizing a suite of durophagous characteristics: molariform teeth, a modified jaw protrusor muscle, altered jaw adductor activity and modified jaw kinematics. Sphyrna tiburo is a specialist feeder on crab prey as demonstrated by the lack of differences in kinematic or motor patterns when offered prey of differing hardness and its apparent lack of ability to modulate its behavior when feeding on other prey. Functional patterns are altered and coupled with modifications in dental and jaw morphology to produce diverse crushing behaviors in elasmobranchs.
Two orcokinins and the novel octapeptide orcomyotropin in the hindgut of the crayfish Orconectes Limosus: Identified myostimulatory neuropeptides originating together in neurones of the terminal abdominal ganglion
Authors: Dircksen Heinrich , Burdzik Siegward , Sauter Arnold , Keller Rainer
Published: April 2021

The tridecapeptides Asn13-orcokinin and Val13- orcokinin, two known members of the orcokinin neuropeptide family native to crustaceans, and a novel octapeptide, orcomyotropin, FDAFTTGFamide, have been identified from extracts of hindguts of the crayfish Orconectes limosus using an isolated hindgut contractility bioassay, high-performance liquid chromatography, microsequencing and mass spectrometry. All three peptides display strong inotropic actions on crayfish hindguts. Orcomyotropin showed higher potency than the two orcokinins. Threshold concentration was approximately 5×10−12 moll−1versus 10−10 moll−1 for the two orcokinins. An approximately fivefold increase in contraction amplitude was observed with 10−9 moll−1 orcomyotropin and 10−7 moll−1 of the orcokinins. Asn13- and Val13-orcokinin did not differ significantly with regard to their biological effects. Semi-isolated crayfish hearts and locust oviducts did not respond to the three peptides. Immunocytochemistry using antisera against Asn13- orcokinin and orcomyotropin showed that these neuropeptides are co-localized in approximately 80–90 neurones of the terminal abdominal ganglion that have been shown to innervate the entire hindgut muscularis via the intestinal nerve. The neurones form elaborate terminal branches preferentially on longitudinal hindgut muscles. Orcomyotropin is a novel crustacean member of the GF-amide family of myotropic and/or allatotropic neuropeptides from annelids, molluscs and insects.
Inspiratory aerodynamic valving in the avian lung: Functional morphology of the extrapulmonary primary bronchus
Authors: Maina John N. , Africa Miranda
Published: April 2021

The form, geometry and epithelial morphology of the extrapulmonary primary bronchi (EPPB) of the domestic fowl (Gallus gallus var. domesticus) and the rock dove (Columba livia) were studied microscopically and by three­dimensional computer reconstruction to determine the structural features that may be involved in the rectification of the inspired air past the openings of the medioventral secondary bronchi (MVSB), i.e. the inspiratory aerodynamic valving (IAV). In both species, the EPPB were intercalated between the clavicular and the cranial thoracic air-sacs. A notable difference between the morphology of the EPPB in G. g. domesticus and C. livia was that, in the former, the EPPB were constricted at the origin of the MVSB, while a dilatation occurred at the same site in the latter. In both species, a highly vascularized, dorsally located hemispherical epithelial swelling was observed cranial to the origin of the MVSB. The MVSB were narrow at their origin and variably angled relative to the longitudinal axis of the EPPB. Conspicuous epithelial tracts and folds were observed on the luminal aspect of the EPPB in both C. livia and G. g. domesticus. From their marked development and their orientation relative to the angled MVSB, these properties may influence the flow of the air in the EPPB. It was concluded that features such as syringeal constriction, an intimate topographic relationship between the EPPB and the cranial air-sacs, prominent epithelial tracts and folds, an epithelial swelling ahead of the origin of the first MVSB (corresponding to the ‘segmentun accelerans’), and narrowing and angulation of the MVSB at their origin, may together contribute to IAV to a variable extent. In as much as the mechanism of pulmonary ventilation and mode of airflow in the parabronchial lung are basically similar in all birds, the morphological differences observed between G. g. domesticus and C. livia suggest that either the mechanism of production of IAV or its functional efficiency may be different, at least in these two species of birds.
Integumentary L-Histidine Transport in a Euryhaline Polychaete Worm: Regulatory Roles of Calcium and Cadmium in the Transport Event
Authors: Hammers Ahearn Heather Rae , Ahearn Gregory A. , Gomme Jørgen
Published: April 2021

Integumentary uptake of L-[3H]histidine by polychaete worms (Nereis succinea) from estuarine waters of Oahu, Hawaii was measured in the presence and absence of calcium and cadmium using a physiological saline that approximated the ion composition of 60 % sea water. In this medium 1 µmol l−1cadmium significantly increased (P<0.01) the uptake of 10 µmol l−1 L-[3H]histidine, while 1 µmol l−1 cadmium plus 25 µmol l−1 L-leucine significantly decreased (P<0.01) amino acid uptake. L-[3H]histidine influx was a sigmoidal function (n=2.21±0.16, mean ± S.E.M.) of [L-histidine] (1–50 µmol l−1) in the absence of cadmium, but became a hyperbolic function with the addition of 1 µmol l−1cadmium. A decrease of calcium concentration from 6 to 0 mmol l−1(lithium substitution) significantly increased (P<0.01) amino acid influx in the presence and absence of cadmium. Calcium significantly reduced (P<0.01), and cadmium significantly increased (P<0.01), L-[3H]histidine influx Jmax, without either divalent cation affecting amino acid influx Kt. Variation in external sodium concentration (0–250 mmol l−1) had no effect on 10 µmol l−1 L-[3H]histidine influx, but amino acid entry was a sigmoidal function of both [cadmium] (n=2.34±0.44) and [lithium] (n=1.91±0.39) in the absence of calcium. A model is proposed for transapical L-[3H]histidine influx by a transporter that resembles the classical sodium-independent L-system carrier protein that is regulated by the external divalent cations calcium and cadmium.
Image Analysis of Olfactory Responses in the Procerebrum of the Terrestrial Slug Limax Marginatus
Authors: Toda Sho’ichi , Kawahara Shigenori , Kirino Yutaka
Published: April 2021

Neural oscillations have been found to occur in the olfactory centers of some vertebrates and invertebrates, including the procerebrum of the terrestrial slug Limax marginatus. Using optical recording with the potential-sensitive dye di-4-ANEPPS, we analyzed the spatiotemporal pattern of procerebral neural activities in response to odorants applied to an in vitro brain-superior tentacle preparation. The odor of rat chow, on which the slugs were normally fed, increased the frequency of the oscillation. Garlic odor, which induced aversive behavior in the slug, caused a transient increase in oscillation frequency during stimulation, followed by a second increase in oscillation frequency when the stimulus was terminated. Wave propagation from the distal to the proximal region of the procerebrum was accelerated in parallel with modulation of the frequency. The cycle-by-cycle average of the optical signals showed that a large area of the cerebral ganglia, including the procerebrum, was depolarized during the initial increase in frequency. During the second increase, however, the net depolarization was most prominent in the terminal mass of the procerebrum. These results suggest that the level of depolarization generated by interactions among the neurites projecting to the terminal mass, such as the neurites of the nonbursting neurons, may control neural oscillations in the procerebrum.
Nitrogen Metabolites and Related Enzymatic Activities in the Body Fluids and Tissues of the Hydrothermal Vent Tubeworm Riftia Pachyptila
Authors: De Cian Marie-Cécile , Regnault Michèle , Lallier François H.
Published: April 2021

The distribution of nitrogen metabolism end-products and the associated enzyme activities, free amino acids and purine base catabolites were investigated in all the body compartments (circulating fluids and tissues) of the hydrothermal vent tubeworm Riftia pachyptila to acquire a general overview of nitrogen metabolism in this symbiotic organism. There were striking differences between the symbiont-containing trophosome tissue and other host tissues. High concentrations of ammonia, creatinine and, in particular, urate were found in all tissues, but they were present at consistently higher concentrations in the trophosome, which also contained large amounts of urea. Uric acid crystals were present at the periphery of trophosome lobules. The urea cycle appears to be fully functional in this tissue, which also uses creatine phosphate for phosphagen storage, while arginine phosphate or a combination of both phosphagens occurs in other tissues. The amino acid patterns are dominated by sulphated compounds in all tissues except the trophosome, which has high levels of aspartate and glutamate. Although no definitive conclusions could be drawn regarding the nitrogen regime of Riftia pachyptila, this in vitro study gives several indications for future research in this area.
The Hind Wing of the Desert Locust (Schistocerca Gregaria Forskål): I. Functional Morphology and Mode of Operation
Authors: Wootton R. J. , Evans K. E. , Herbert R. , Smith C. W.
Published: April 2021

Detailed morphological investigation, mechanical testing and high-speed cinematography and stroboscopic examination of desert locusts, Schistocerca gregaria, in flight show that their hind wings are adapted to deform cyclically and automatically through the wing stroke and that the deformations are subtly dependent on the wings’ structure: their shape, venation and vein design and the local properties of the membrane. The insects predominantly fly fast forwards, generating most force on the downstroke, and the hind wings generate extra lift by peeling apart at the beginning of the downstroke and by developing a cambered section during the stroke’s translation phase through the ‘umbrella effect’ – an automatic consequence of the active extension of the wings’ expanded posterior fan. Bending experiments indicate that most of the hind wing is more rigid to forces from below than from above and demonstrate that the membrane acts as a stressed skin to stiffen the structure.
Effects of Environmental Salinity on Na+/K+-ATPase in the Gills and Rectal Gland of a Euryhaline Elasmobranch (Dasyatis Sabina)
Authors: Piermarini Peter M. , Evans David H.
Published: April 2021

Changes in Na+/K+-ATPase activity and abundance associated with environmental salinity were investigated in the gills and rectal gland of the Atlantic stingray Dasyatis sabina. Using a ouabain-specific ATPase assay and western blotting, we found that stingrays from fresh water had the highest activity and highest relative abundance of Na+/K+-ATPase in the gills. Using immunohistochemistry, we also found that gills from freshwater stingrays had the greatest number of Na+/K+-ATPase-rich cells. When freshwater stingrays were acclimated to sea water for 1 week, the activity and abundance of Na+/K+-ATPase and the number of Na+/K+-ATPase-rich cells decreased in the gills. In seawater stingrays, the branchial activity and abundance of Na+/K+-ATPase and the number of Na+/K+-ATPase-rich cells were further reduced. In rectal glands, the activity and abundance of Na+/K+-ATPase were lower in freshwater animals than in seawater-acclimated and seawater stingrays, both of which had equivalent levels. These findings suggest that salinity-associated changes in gill and rectal gland Na+/K+-ATPase activity are due to changes in the abundance of Na+/K+-ATPase. We conclude that the gills may be important for active ion uptake in fresh water, while the rectal gland is important for active NaCl excretion in sea water. The results from this study are the first to demonstrate an effect of environmental salinity on Na+/K+-ATPase expression in the gills and rectal gland of an elasmobranch.
Maintenance of Neutral Buoyancy by Depth Selection in the Loggerhead Turtle Caretta Caretta
Authors: Minamikawa Shingo , Naito Yasuhiko , Sato Katsufumi , Matsuzawa Yoshimasa , Bando Takeharu , Sakamoto Wataru
Published: April 2021

Time-series data of swimming speed and dive depth were recorded in six female loggerhead turtles Caretta caretta during the internesting period. The dive profiles of all animals indicated that they stayed at particular depths without swimming and that these depths were correlated with dive duration. These results support the hypothesis that lung air is used to achieve neutral buoyancy in the loggerhead turtle.

To test this hypothesis, female turtles were equipped with lead weights and time/depth recorders. The residence depth of the turtles increased when their specific gravity was artificially decreased. This indicates that they control depth rather than lung volume, suggesting that the residence depth of loggerhead turtles during the internesting period is not determined actively. They presumably remain at a particular depth exclusively to save energy for egg maturation during the internesting period.

Lung volume was estimated from the change in depth of weighted animals to be 50–150 ml kg−1. The resulting residence depth of all turtles was within the range at which they maintained the neutral buoyancy.
Sniffing by a Silkworm Moth: Wing Fanning Enhances air Penetration Through and Pheromone Interception by Antennae
Authors: Loudon C. , Koehl M. A. R.
Published: April 2021

Many organisms increase the air or water flow adjacent to olfactory surfaces when exposed to appropriate chemical stimuli; such ‘sniffing’ samples fluid from a specific region and can increase the rate of interception of odorant molecules. We used hot-wire anemometry, high-speed videography and flow visualization to study air flow near the feathery olfactory antennae of male silkworm moths (Bombyx mori L.). When exposed to conspecific female sex pheromone, male B. mori flap their wings through a stroke angle of 90–110 ° at approximately 40 Hz without flying. This behavior generates an unsteady flow of air (mean speed 0.3–0.4 m s−1) towards the antennae from the front of the male. A pulse of peak air speed occurs at each wing upstroke. The Womersley number (characterizing the damping of pulsatile flow through the gaps between the sensory hairs on the antennae) is less than 1; hence, pulses of faster air (at 40 Hz) should move between sensory hairs. Calculation of flow through arrays of cylinders suggest that this wing fanning can increase the rate of interception of pheromone by the sensory hairs on the antennae by at least an order of magnitude beyond that in still air. Although wing fanning produces air flow relative to the antennae that is approximately 15 times faster than that generated by walking at top speed (0.023 m s−1), air flow through the gaps between the sensory hairs is approximately 560 times faster because a dramatic increase in the leakiness of the feathery antennae to air flow occurs at the air velocities produced by fanning.
Properties of a Carbonic Anhydrase Inhibitor Protein in Flounder Serum
Authors: Peters Thomas , Papadopoulos Frauke , Kubis Hans-Peter , Gros Gerolf
Published: April 2021

The blood serum of the European flounder Platichthys flesus strongly inhibits soluble erythrocytic carbonic anhydrase from the same species. The inhibition is of the uncompetitive type. Hence, the mechanism of the carbonic anhydrase inhibition is different from that of all other known carbonic anhydrase inhibitors. The serum showed no inhibitory effect on carbonic anhydrase from human and bovine red blood cells. By applying the 18O exchange reaction, it could be demonstrated that the presence of the carbonic anhydrase inhibitor in the extracellular fluid has no effect on carbonic anhydrase in intact red blood cells. Thus, this carbonic anhydrase inhibitor seems to act only within the plasma space of the circulatory system.

However, the carbonic anhydrase inhibitor does appear to reduce the bicarbonate permeability of flounder red cells to approximately one-quarter of normal levels as measured by the 18O exchange reaction. The 28 kDa carbonic anhydrase inhibitor was isolated from the serum by gel filtration. The isolated inhibitor was detected in acrylamide gels as a single band representing a 7 kDa protein. The denaturing conditions used in electrophoresis presumably led to a dissociation of the native protein into subunits.
Ecdysteroids Regulate Secretory Competence in Inka Cells
Authors: Kingan Timothy G. , Adams Michael E.
Published: April 2021

Ecdysis, or molting behavior, in insects requires the sequential action of high levels of ecdysteroids, which induce accumulation of ecdysis-triggering hormone (ETH) in Inka cells, followed by low levels of ecdysteroids, permissive for the onset of the behavior. Here, we show that high ecdysteroid levels suppress the onset of the behavioral sequence by inhibiting the development of competence to secrete ETH. In pharate pupae of Manduca sexta, Inka cells in the epitracheal glands normally develop competence to secrete ETH in response to eclosion hormone (EH) 8 h before pupation. Injection of 20-hydroxyecdysone (20E) into precompetent insects prevents this acquisition of competence, but does not affect EH-evoked accumulation of the second messenger cyclic GMP. Precompetent glands acquire competence in vitro after overnight culture, and this can be prevented by the inclusion of 20E at concentrations greater than 0.1 μg ml−1 in the culture medium. Actinomycin D completely inhibits the acquisition of competence, demonstrating that it is dependent on transcriptional events. Cultured epitracheal glands become refractory to the inhibitory effects of 20E in the acquisition of competence at least 3 h earlier than for Actinomycin D, indicating that 20E acts on an early step in a sequence of nuclear events leading to transcription of a structural gene. Our findings suggest that declining ecdysteroid levels permit a late event in transcription, the product of which is downstream of EH receptor activation and cyclic GMP accumulation in the cascade leading to ETH secretion.
Intraspecific Scaling of Feeding Mechanics in an Ontogenetic Series of Zebrafish, Danio Rerio
Authors: Hernández Luz Patricia
Published: April 2021

While a vast literature and long tradition of examining the scaling of locomotory function exists, scaling studies on feeding mechanics are relatively rare. A recent increase in research activity examining the scaling of feeding kinematics has led to conflicting results. These divergent findings may be due to the inherent differences in the biophysical systems being examined. The present study examines the role of growth in the scaling of feeding kinematics in an ontogenetic series of zebrafish, Danio rerio. Although many other studies have investigated aquatic feeding, this study represents the first to quantify detailed feeding kinematics in first-feeding larvae. This study examines both the effects of violating assumptions of geometric similarity when examining scaling relationships and the role water viscosity plays in molding scaling coefficients derived from feeding kinematics. The effects of Reynolds number, generally not relevant in vertebrate feeding studies, play a crucial role in determining scaling relationships in this species. Many scaling coefficients reflect the functional challenges of feeding at low Reynolds numbers. Moreover, scaling patterns in feeding mechanics often reflect allometric growth during early ontogeny. The advent of high-speed video recording (1000 frames s−1) now allows the kinematics of feeding at these small sizes to be rigorously examined.
Effects of Nonylphenol and 17β-Estradiol on Vitellogenin Synthesis and Testis Morphology in Male Platyfish Xiphophorus Maculatus
Authors: Kinnberg Karin , Korsgaard Bodil , Bjerregaard Poul , Jespersen Åse
Published: April 2021

Nonylphenol has been found to exert estrogenic effects in fish and may influence the fertility of male fish. In the present study, the effects of nonylphenol and 17β-estradiol on vitellogenin synthesis and testis morphology in platyfish Xiphophorus maculatus were investigated. Vitellogenin was observed in the plasma of all fish exposed to nonylphenol or 17β-estradiol. Exposure to 17β-estradiol resulted in a significant reduction in the gonadosomatic index. A tendency for a dose-dependent reduction in the gonadosomatic index in the nonylphenol exposed groups was observed. Histological examination revealed dose-dependent effects of nonylphenol on the testis structure. The testes of control fish contained numerous cysts with spermatogenetic cells. The testes of fish exposed to nonylphenol or 17β-estradiol showed a decrease in the number of cysts concomitant with an increase in the amount of hypertrophied Sertoli cells present. Formation of spermatozeugmata is compulsory for this species, but free spermatozoa were observed in the efferent ducts of the treated fish. The study indicates that nonylphenol has estrogenic potency, and that both nonylphenol and 17β-estradiol have marked effects on the testis morphology of X. maculatus. The ambient concentration of nonylphenol was measured by high pressure liquid chromatography during the experiment. The measurements revealed that the actual concentrations of nonylphenol in the water were about 30–40 % of the nominal concentrations.
Escape Behaviour in the Stomatopod Crustacean Squilla Mantis, and the Evolution of the Caridoid Escape Reaction
Authors: Heitler W. J. , Fraser K. , Ferrero E. A.
Published: April 2021

The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards ‘lurch’ or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll.

A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably.

The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.
Tracking Clock-Shifted Homing Pigeons From Familiar Release Sites
Authors: Bonadona Fransisco , Holland Richard , Dall’Antonia Luigi , Guilford Tim , Benvenuti Silvano
Published: April 2021

Clock-shifted homing pigeons were tracked from familiar sites 17.1 km and 23.5 km from the home loft in Pisa, Italy, using an on-board route recorder. At the first release site, north of home, the majority of clock-shifted birds had relatively straight tracks comparable with those of control birds. At the second release site, south of home, the clock-shifted birds deflected in the direction predicted for the degree of clock shift, with many birds travelling some distance in the wrong direction before correcting their course. The possible role of large-scale terrain features in homing pigeon navigation is discussed.
The Independent Effects of Gravity and Inertia on Running Mechanics
Authors: Chang Young-Hui , Huang Hsuan-Wen Cathy , Hamerski Chris M. , Kram Rodger
Published: April 2021

It is difficult to distinguish the independent effects of gravity from those of inertia on a running animal. Simply adding mass proportionally changes both the weight (gravitational force) and mass (inertial force) of the animal. We measured ground reaction forces for eight male humans running normally at 3 m s−1 and under three experimental treatments: added gravitational and inertial forces, added inertial forces and reduced gravitational forces. Subjects ran at 110, 120 and 130 % of normal weight and mass, at 110, 120 and 130 % of normal mass while maintaining 100 % normal weight, and at 25, 50 and 75 % of normal weight while maintaining 100 % normal mass. The peak active vertical forces generated changed with weight, but did not change with mass. Surprisingly, horizontal impulses changed substantially more with weight than with mass. Gravity exerted a greater influence than inertia on both vertical and horizontal forces generated against the ground during running. Subjects changed vertical and horizontal forces proportionately at corresponding times in the step cycle to maintain the orientation of the resultant vector despite a nearly threefold change in magnitude across treatments. Maintaining the orientation of the resultant vector during periods of high force generation aligns the vector with the leg to minimize muscle forces.
Periodic Tension Development in the Membrane of the in Vitro Contractile Vacuole of Paramecium Multimicronucleatum: Modification by Bisection, Fusion and Suction
Authors: Tani Tomomi , Allen Richard D. , Naitoh Yutaka
Published: April 2021

The contractile vacuole of the freshwater protozoan Paramecium multimicronucleatum is a membrane-bound exocytotic vesicle that expels excess cytosolic water. The in vitro contractile vacuole isolated from P. multimicronucleatum along with a small amount of cytosol and confined under mineral oil showed periodic rounding and slackening at fairly regular intervals. Activity lasted for over 30 min at room temperature (24–27 °C). The rounding of the in vitro contractile vacuole corresponded to the increased membrane tension of the in vivo contractile vacuole that occurs immediately before fluid expulsion. Unlike the in vivo contractile vacuole, the in vitro contractile vacuole did not expel fluid, since it lacked a mechanism to form a pore. The subsequent slackening of the in vitro contractile vacuole corresponded to the fluid-filling phase of the in vivo contractile vacuole that occurs at decreased membrane tension. Fluid filling occurred in the in vitro contractile vacuole only when it was isolated together with its radial arms. In vitro membrane-bound vesicles obtained by ‘bisecting’ (although the two parts were not always identical in size) an in vitro contractile vacuole established their own independent rounding– slackening cycles. In vitro contractile vacuole vesicles could fuse again when the vesicles slackened. The fused vesicle then showed a rounding–slackening cycle with a period closer to that of the vesicle that exhibited the shorter cycle period. An additional rounding phase of the in vitro contractile vacuole could be induced by applying suction to a portion of its membrane with a micropipette when the contractile vacuole was in its slackened phase. This suggests that maximum tension development in the contractile vacuole membrane can be triggered when tension is increased in any part of the contractile vacuole membrane. The time from the start of an extra rounding phase to the next spontaneous rounding and for subsequent rounding–slackening cycles was nearly the same as that before the extra rounding phase. This implies that there is no master pacemaker to control the rounding–slackening cycle in the contractile vacuole membrane. Severed radial arms also became vesiculated and, like contractile vacuole membranes, these in vitro vesicles showed independent rounding–slackening cycles and vesicle–vesicle fusions. Thus, membrane derived from the radial arm seems to be identical in its tension-developing properties with the contractile vacuole membrane. ATP was found to be required for contractile vacuole rounding but inhibitors of actin or tubulin polymerization, such as cytochalasin B and Nocodazole, had no effect on the in vitro contractile vacuole’s rounding–slackening cycle.