bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of softwater acclimation on respiratory gas transfer in the rainbow trout Oncorhynchus mykiss
Authors: Greco Anna Maria , Gilmour Kathleen M. , Fenwick James C. , Perry Steve F.
Published: April 2021

Gill O2 uptake, CO2 excretion, ventilation and blood respiratory/acid–base variables were evaluated in control and softwater-acclimated trout (Oncorhynchus mykiss) to test the hypothesis that gill chloride cell (CC) proliferation, elicited by 2 weeks of softwater exposure, impairs the diffusion of respiratory gases across the gill. The proliferation of CCs in softwater fish was verified using light microscopy, and its impact on respiratory gas transfer was assessed in vivo by continuous monitoring of arterial blood and pH (pHa) using an extracorporeal blood circulation under conditions of normoxia and graded hypoxia [water was lowered from 20.0 kPa to 5.3 kPa within 20 min].

During normoxia, ventilation frequency was significantly higher in the softwater trout (78±4 versus 57±4 breaths min-1; mean ± S.E.M.), while ventilation amplitude was similar in both groups (1.0–1.1 cm opercular displacement). and plasma HCO3- concentration were significantly lower in the softwater fish and the blood acid–base status was characterized by a mixed respiratory alkalosis and metabolic acidosis such that blood pH was not statistically different between the two groups. CO2 excretion (2.5–2.8 mmol kg-1 h-1) and O2 uptake rates (2.3–5.1 mmol kg-1 h-1), as measured during normoxia, were unaffected by acclimation to soft water.

During hypoxia, ventilation frequency and amplitude increased in the control trout, whereas only ventilation amplitude increased in the softwater-acclimated fish. The rate of reduction during hypoxia was significantly greater in the softwater fish (0.84±0.06 versus 0.65±0.06 kPa kPa-1 ) and, at the most severe level of hypoxia , was significantly lower in the softwater fish. The rate of reduction (caused by hyperventilation) was significantly lower in the softwater-acclimated fish (0.002±0.001 versus 0.005±0.001 kPa kPa-1 ; mean ± S.E.M.; P<0.06) and, indeed, was not statistically different from zero. Blood pH did not change significantly during hypoxia in either group but, through much of the hypoxic period (7–15 kPa ), pHa was statistically lower in the softwater-acclimated fish.

These results demonstrate that exposure of trout to soft water for 2 weeks is associated with proliferation of lamellar CCs and impaired branchial gas transfer. Hyperventilation was identified as a compensatory physiological adjustment.
Parasympathetic Influence on Heart Rate in Euthermic and Hibernating Ground Squirrels
Authors: Harris Michael B. , Milsom William K.
Published: April 2021

The relative role of the parasympathetic nervous system during deep hibernation is enigmatic. Conflicting hypotheses exist, and both sides draw support from investigations of vagal influence on the heart. Recent studies have shown cardiac chronotropic and inotropic effects of parasympathetic stimulation and inhibition in isolated hearts and anesthetized animals at hibernating body temperatures. No studies, however, have demonstrated such occurrences in undisturbed deeply hibernating animals. The present study documents respiratory-related alterations in heart rate during euthermia and hibernation at ambient temperatures of 15, 10 and 5°C mediated by parasympathetic influence.

During quiet wakefulness, euthermic squirrels breathed continuously and exhibited a 29% acceleration in heart rate during inspiration. During deep undisturbed hibernation, at 15, 10 and 5°C ambient temperature, animals exhibited an episodic breathing pattern and body temperatures were slightly above ambient temperature. At each temperature, heart rate during the respiratory episode was greater than that during the apnea. The magnitude of this ventilatory tachycardia decreased with ambient temperature, being 108% at 15°C, 32% at 10°C and 11.5% at 5°C. Animals exposed to 3% CO2 at 5°C, which significantly increased ventilation, still exhibited an 11.7% increase in heart rate during breathing. Thus, the magnitude of the ventilation tachycardia was independent of the level of ventilation, at least over the range studied. Inhibition of vagus nerve conduction at 5°C was achieved using localized nerve block. This led to an increase in apneic heart rate and abolished the ventilatory tachycardia. The results of this study indicate that vagal projections are involved in cardiorespiratory control during deep hibernation, i.e. that parasympathetic tone is still present and is involved in homeostatic regulation during hibernation.
Active Calcium Transport in the Skin of the Frog Rana Pipiens: Kinetics and Seasonal Rhythms
Authors: Stiffler Daniel F.
Published: April 2021

The frog Rana pipiens takes up Ca2+ against an electrochemical gradient from dilute external solutions that are similar to natural freshwater environments. The influx is dependent upon external [Ca2+] and is saturable. Kinetic analysis yielded a Km of 0.625 mmol l−1 and a Jmax of 38 nmol cm−2 h−1. These kinetic variables suggest that both the affinity and capacity are smaller than those for Na+ and Cl− transport in the skin of the same species. They are also smaller than those for Ca2+ transport in fish gill. A significant portion (20–25%) of the Ca2+ entering a frog remains in Ca2+-rich layers of the skin, with ventral skin containing about three times as much Ca2+ as dorsal skin. There are seasonal rhythms in Ca2+ exchange: although Ca2+ influx does not vary significantly over the year, efflux is minimal in July, while net flux, which is negative most of the year, appears to be positive in July. Since these fluxes do not include dietary calcium, one cannot conclude that feeding frogs are in negative Ca2+ balance.
Regulation of Na+/H+ Antiporter in Trout Red Blood Cells
Authors: Malapert Murielle , Guizouarn Helene , Fievet Bruno , Jahns Roland , Garcia-Romeu Federico , Motais Rene , Borgese Franck
Published: April 2021

The trout red blood cell Na+/H+ antiporter (βNHE) displays two interesting properties: it is the only NHE known to be activated by cyclic AMP, and the activation process is followed by a desensitisation of the transport system itself.

Cloning and expression of βNHE have provided significant information about Na+/H+ activation, in particular that activation by cyclic AMP is directly dependent upon the presence of two protein kinase A consensus sites in the cytoplasmic tail of the antiporter. Expression of βNHE in fibroblasts demonstrates that the protein kinase A (PKA) and protein kinase C (PKC) activation pathways are independent and do not converge on a common kinase. Moreover, the hydrophilic C-terminal fragment is essential to the mediation of the various hormonal responses. NHE1 (the human ubiquitous isoform) is not activated by cyclic AMP, but a ‘NHE1 transmembrane domain/βNHE cytoplasmic domain’ chimera is fully activated by cyclic AMP.

In red cells, activation of βNHE is the result of phosphorylation by PKA of at least two independent sites. Desensitisation, inhibited by the phosphatase inhibitor okadaic acid, may consist of the dephosphorylation of one of these two sites. Furthermore, Calyculin A (ClA), another specific protein phosphatase inhibitor, induces in unstimulated cells a Na+/H+ exchange activity whose exchange properties are very different from those of the adrenergically stimulated antiporter. It is suggested that ClA may be able to revive ‘sequestered’ antiporters.

We propose that the molecular events underlying βNHE desensitisation could be similar to those involved in rhodopsin desensitisation. Antibodies were generated against trout red cell arrestin in order to analyse the binding of arrestin to the activated exchanger. Recombinant trout arrestin was produced in a protease-deficient strain of Escherichia coli and its functionality tested in a reconstituted rhodopsin assay.
The Role of Glutamate Transporters in Glutamate Homeostasis in the Brain
Authors: Takahashi Michiko , Billups Brian , Rossi David , Sarantis Monique , Hamann Martine , Attwell David
Published: April 2021

Glutamate transporters in neurones and glia, four of which have been cloned from mammals, play a crucial role in controlling the extracellular glutamate concentration in the brain. In normal conditions, they remove glutamate from the extracellular space and thereby help to terminate glutamatergic synaptic transmission and to prevent the extracellular glutamate concentration from rising to neurotoxic values. Glutamate transport on these carriers is thought to be driven by the cotransport of Na+, the counter-transport of K+, and either the cotransport of H+ or the counter-transport of OH−. Activating the transporters also activates an anion conductance in their structure, the anion flux through which is not coupled to glutamate movement and varies widely for the different transporters. During hypoxia or ischaemia, glutamate transporters can run backwards, releasing glutamate into the extracellular space, triggering the death of neurones and thus causing mental and physical handicap. The rate of glutamate release by this process is slowed by the acid pH occurring in hypoxia/ischaemia, which may help protect the brain during transient, but not sustained, ischaemia.
The Role of Antennal Sensory Cues in Female Responses to Courting Males in the Cricket Teleogryllus Oceanicus
Authors: Balakrishnan Rohini , Pollack Gerald S.
Published: April 2021

Courtship communication in the field cricket Teleogryllus oceanicus is multimodal, involving a minimum of both acoustic and chemical cues. The acoustic signal, or courtship song, is necessary to elicit normal levels of female mounting of the male during courtship. Antennal input is also crucial since antennectomized females show highly reduced levels of mounting. Immobilization of the scape–pedicel and pedicel–flagellum joints of female antennae had no effect on mounting probability, suggesting that mechanosensory input from chordotonal organs at the base of the antenna is not necessary. The antennal flagellum is a multimodal sensory organ, which contains both mechanoreceptors and chemoreceptors. In order to dissect the roles of different flagellar modalities, we treated antennae with zinc sulphate. This suppressed a well-characterized contact-chemosensory behaviour, initiation of courtship by males, and eliminated responsiveness of most chemosensory hairs as assayed electrophysiologically. Zinc sulphate treatment had no effect on a tactile antennal reflex, indicating that it selectively silenced chemoreceptors. Treatment of antennae with zinc sulphate reduced mounting levels nearly as much as antennectomy, suggesting that the main antennal cue required for the mounting responses is chemosensory, rather than mechanosensory, in nature.
Dragonfly Flight : II. Velocities, Accelerations and Kinematics of Flapping Flight
Authors: Wakeling J. M. , Ellington C. P.
Published: April 2021

The free flapping flight of the dragonfly Sympetrum sanguineum and the damselfly Calopteryx splendens was filmed in a large flight enclosure at 3000 frames s−1. The wingtip kinematics are described for these flights. Despite the two species being similar in size, the damselfly flew with wingbeat frequencies half those of the dragonfly. The damselfly could perform a clap and fling, and the proximity to which the wings approached each other during this manoeuvre correlated with the total force produced during the wingstroke. The dragonfly beat its wings with a set inclination of the stroke planes with respect to the londitudinal body axis; the damselfly, in contrast, showed a greater variation in this angle. Both species aligned their stroke planes to be nearly normal to the direction of the resultant force, the thrust. In order to achieve this, the dragonfly body alignment correlated with the direction of thrust. However, the damselfly body alignment was independent of the thrust direction. Velocities and accelerations were greater for the dragonfly than for the damselfly. However, non-dimensional velocities and accelerations normalised by the wingbeat periods were greater for the damselfly.
Ca2+ Signaling in Fowl Aortic Smooth Muscle Increases During Maturation But is Impaired in Neointimal Plaques
Authors: Qin Ze-Lian , Nishimura Hiroko
Published: April 2021

Many bird species show the spontaneous development of high arterial pressure and vascular lesions in the aorta and other large arteries. In chickens, arterial pressure tends to increase with age/maturation (particularly in males), and subendothelial hyperplasia (neointima) in the abdominal aorta is often seen prior to sexual maturation. The mechanisms involved, however, are not known. Our aim, therefore, was to determine (1) whether cytosolic Ca2+ signaling (CCS) responses to vasoactive substances in fowl aortic smooth muscle differ among chickens at different maturation stages and (2) whether CCS responses to Ca2+ channel agonists in neointimal plaques differ from those in normal aortic smooth muscle.

K+ increased CCS in a dose-dependent manner in isolated and superfused abdominal aortic smooth muscle tissue from chicks (5–9 weeks old), pullets (11–18 weeks old) and adult hens (20 weeks and older); CCS responses increased as chickens matured. The addition of Bay K 8644 (10−6 mol l−1) to Ringer’s solution containing 50 mmol l−1 K+ further increased CCS, and this response was reduced to half by nifedipine (10−6 mol l−1). Norepinephrine did not alter CCS in chicks, whereas marked dose-dependent increases in CCS were noted in pullets. In contrast to the CCS responses to K+, the norepinephrine-induced CCS responses became smaller in adult hens. Isolated neointimal plaques showed only slight increases in CCS in response to 50 mmol l−1 K+ plus Bay K 8644, whereas clear responses were noted in aortic smooth muscle tissue underlying the plaques. These results suggest (1) that CCS responses to Ca2+ channel agonists increased with sexual maturation in fowl, but (2) that CCS responses to norepinephrine were low in mature hens and to K+ plus Bay K 8644 were low in spontaneously developed neointima, suggesting that phenotypic modulation of Ca2+ channel/norepinephrine receptors may have occurred during maturation/aging and in neointima.
Scavenger-Receptor-Mediated Endocytosis in Endocardial Endothelial Cells of Atlantic Cod Gadus Morhua
Authors: Sørensen Karen K. , Melkko Jukka , Smedsrød Bård
Published: April 2021

Scavenger receptors are multifunctional integral membrane proteins that mediate the endocytosis of many different macromolecular polyanions and also participate in host defence reactions and cell adherance. In Atlantic cod (Gadus morhua L.), two intravenously injected scavenger receptor ligands, [125I]tyramine-cellobiose-labelled formaldehyde-treated serum albumin (125I-TC-FSA) and 125I-labelled N-terminal propeptide of type I procollagen (125I-PINP), distributed mainly to the heart. Cellular uptake was visualized by injections of fluorescently labelled FSA (FITC-FSA), which was recovered in discrete vesicles in endocardial endothelial cells of both heart chambers. Studies in vitro showed that radioiodinated FSA and PINP were endocytosed and degraded very efficiently by cultured atrial endocardial endothelial cells. Moreover, uptake of 125I-FSA was Ca2+-independent. Out of a range of unlabelled ligands, only the scavenger receptor ligands FITC-FSA, polyinosinic acid and, to a varying extent, FSA, acetylated low-density lipoprotein (AcLDL) and PINP, were able to compete with radioiodinated FSA, PINP or AcLDL for uptake in isolated endocardial cells. From our findings, we conclude that the endocardial endothelial cells are major carriers of scavenger receptors in cod. In addition, our results strengthen the hypothesis that these cells in cod play the same important function as that established for the scavenger endothelial cells of the mammalian liver.
The Role of the Frontal Ganglion in the Feeding and Eclosion Behavior of the Moth Manduca Sexta
Authors: Miles Carol I. , Booker Ronald
Published: April 2021

We have examined the musculature and motor patterns of the foregut and the role of the frontal ganglion in the adult moth Manduca sexta. During adult development, the structure of the foregut changes from a simple straight tube to a pump consisting of a flexible-roofed chamber or cibarium, with dilator muscles that raise the roof to draw in fluids and a compressor to push it down and force the fluid down the thin-walled esophagus. The frontal ganglion drives the activity of this cibarial pump during feeding, which is triggered by the application of sucrose solution or water to the proboscis. The feeding motor pattern consists of coupled bursts of the pump dilators and shorter-duration, high-frequency bursts of spikes from the pump compressor.

The pump is also activated at the adult molt. At this time, it is used both before the moth emerges from the pupal case for swallowing molting fluid and again after emergence for swallowing air. These behaviors are important for eclosion and are necessary for the expansion of the wings after eclosion. Their motor patterns are similar to the feeding program. Up to 24 h before adult ecdysis, this motor pattern can be triggered by the peptide eclosion hormone. The other eclosion-related peptide, Manduca sexta eclosion-triggering hormone, does not appear to trigger activity of the cibarial pump.
The Energetic Cost of Copulation in a Polygynandrous Millipede
Authors: Telford Steven R. , Webb Peter I.
Published: April 2021

We determined the energetic cost of copulation in both sexes of Alloporus uncinatus, a polygynandrous millipede in which copulation can last for several hours and involves physical restraint of the female by the male. We found an elevation in the rate of oxygen consumption by males and a depression in the rate of oxygen consumption by females during copulation. The rate of oxygen consumption of females, but not of males, was elevated immediately after copulation, indicating that females had built up and were repaying an oxygen debt. On this basis, we estimated energy expenditure during copulation to be 30 % above resting levels in males and 14 % above resting levels in females. As matings are frequent in this species in the wild throughout the 4 month breeding season, we suggest that the energetic demands of copulation are a previously overlooked potentially significant cost of reproduction in this species and in other invertebrate species with similar mating patterns.
A Role of 5-HT2 Receptors in the Gill Vasculature of the Antarctic Fish Pagothenia Borchgrevinki
Authors: Sundin Lena , Davison William , Forster Malcolm , Axelsson Michael
Published: April 2021

This study was conducted to describe the cardiovascular responses to intra-arterial injections of serotonin in the Antarctic fish Pagothenia borchgrevinki and to elucidate the underlying mechanisms. Immunohistochemistry was used to localise serotonin-containing cells within the gills. Simultaneous and continuous recordings of ventral and dorsal aortic blood pressure, heart rate and ventral aortic blood flow (cardiac output) were made using standard cannulation procedures in combination with Doppler flow measurement. An extracorporeal loop with an in-line oxygen electrode allowed continuous measurements of arterial oxygen pressure Pre-branchial injection of serotonin (5-hydroxytryptamine, 5-HT) or the 5-HT2 receptor agonist α-methylserotonin increased the branchial vascular resistance and ventral aortic pressure, while the 5-HT1 receptor agonist piperazine was without effect. The branchial vasoconstriction produced by serotonin injection was completely blocked by the 5-HT1/5-HT2 receptor antagonist methysergide and the branchial vasoconstriction produced by α-methylserotonin injection was completely blocked by the specific 5-HT2 receptor antagonist LY53857. The results suggest that the 5-HT2 receptor alone mediates the branchial vasoconstriction. Serotonin also mediated a methysergide-sensitive reduction in , the reduction being greatest when the pre-injection value was high. 5-HT-immunoreactive cells and nerve fibres were present within the gill tissues. All the 5-HT-immunoreactive cells were located on the efferent side of the filaments, but 5-HT-immunoreactive nerve fibres were found lining both of the branchial arteries. Our findings demonstrate a potential serotonergic control system for the gills in Pagothenia borchgrevinki. In contrast to its effects on the branchial vasculature, serotonin produced a methysergide-insensitive decrease in the systemic vascular resistance. However, neither the specific 5-HT1 nor 5-HT2 receptor agonists produced a decrease in the resistance of the systemic vasculature. The nature of the serotonergic receptor(s) inducing vasodilation in teleost fish is uncertain.
Prolonged Swimming, Recovery and Repeat Swimming Performance of Mature Sockeye Salmon Oncorhynchus Nerka Exposed to Moderate Hypoxia and Pentachlorophenol
Authors: Farrell A. P. , Gamperl A. K. , Birtwell I. K.
Published: April 2021

Mature, wild sockeye salmon (Oncorhynchus nerka) demonstrated their remarkable stamina and recovery abilities by performing three consecutive critical swimming speed tests with only a 45 min interval for recovery between subsequent tests. Although the repeated swimming challenges were performed without a full recovery, normoxic fish swam just as well on the second swim, and the majority of fish swam only marginally more poorly on the third swim. In addition, metabolic loading in these fish, as measured by the rate of oxygen consumption, ventilation rate and plasma lactate levels during recovery, did not appear to be cumulative with successive swims. Fish, however, did not recover as well after a similar level of initial swimming performance under moderately hypoxic conditions (water mmHg; 1 mmHg=0.1333 kPa). Four out of the five fish did not swim again and their high plasma lactate levels indicated a greater anaerobic effort.

In another group of fish, metabolic loading (elevated control rates of oxygen consumption) was induced with an overnight sublethal exposure to pentachlorophenol, but these fish swam as well as normoxic fish on the first swim, and five of the six fish swam for a third time at a marginally lower critical swimming speed. In contrast to expectations, pentachlorophenol pretreatment and moderate hypoxia were not additive in their effects. Instead, the effects resembled those of pentachlorophenol pretreatment alone. The results are discussed in terms of what aspects of fatigue might impair the repeat swimming performance of sockeye salmon.
Visual Modulation of Olfactory Learning in Honeybees
Authors: Gerber Bertram , Smith Brian H.
Published: April 2021

We use classical conditioning of the honeybee (Apis mellifera) proboscis extension reflex with a visual (A) and an olfactory (X) conditioned stimulus in a blocking paradigm. Typically, learning about one element (X) of a compound (AX) is decreased (blocked) if the other component (A) has previously been rewarded alone. Our results show that visual pretraining did not produce blocking in honeybees: instead, forward pairings of A with a reward increased subsequent learning about X relative to a backward pairing control. This finding violates the independence assumption, which holds that elements of inter-modal compound stimuli change associative strength independently of each other. Furthermore, it is at odds with common theories of conditioning that predict blocking and assume that the elements of a compound stimulus rely on one common internal reinforcing signal. Taking the functional anatomy of the honeybee brain into account, we suggest that vision and olfaction may not rely on the same internal reinforcing signal; compound interactions might thus reflect the wiring of the honeybee nervous system and the biological significance of different sensory modalities during natural behaviour.
Why Do Mayflies Lay Their Eggs En Masse on Dry Asphalt Roads? Water-Imitating Polarized Light Reflected From Asphalt Attracts Ephemeroptera
Authors: Kriska György , Horváth Gábor , Andrikovics Sándor
Published: April 2021

We report on dry asphalt roads acting as ‘mayfly traps’; that is, they lure swarming, mating and egg-laying mayflies in large numbers. To explain this surprising behaviour, we performed multiple-choice experiments with Ephemeroptera in the field, and measured and compared the reflection–polarization characteristics of an asphalt road and a mountain creek from which mayflies emerge. We show here that Ephemeroptera can be deceived by and attracted to dry asphalt roads because of the strongly horizontally polarized light reflected from the surface. Asphalt surfaces can mimic a highly polarized water surface to Ephemeroptera. The darker and smoother the asphalt surface, the higher is the degree of polarization of reflected light and the more attractive is the road to mayflies. We show that mayflies detect water by means of polarotaxis; that is, on the basis of the partially and horizontally polarized reflected light. Asphalt roads are excellent markers for swarming Ephemeroptera because of their conspicuous elongated form; the sky above them is usually open, which is the prerequisite of mayfly mating, and the higher temperature of the asphalt prolongs the reproductive activity of mayflies. These additional factors enhance the attractiveness of asphalt roads to swarming mayflies. Thus, asphalt roads near ephemeropteran emergence sites (lakes, rivers and creeks) are a great danger for mayflies, because eggs laid on the asphalt inevitably perish. Asphalt roads can deceive and attract mayflies en masse like the ancient tar pits and asphalt seeps or the recent crude or waste oil lakes deceive, lure and trap polarization-sensitive water-seeking insects in large numbers.
Adhesion and Reattachment of Compound Ascidians to Various Substrata: Weak Glue can Prevent Tissue Damage
Authors: Edlund Anna F. , Koehl M. A. R.
Published: April 2021

Sessile, soft-bodied, compound ascidians are successful competitors for substrata in crowded benthic and epibiotic marine communities and can be effective colonists of new sites, through adult rafting and reattachment. Adhesion to the substratum is essential for these ecologically important functions; we therefore studied the material properties of colony attachment to various substrata in the rafting ascidians Botrylloides sp. We found that, compared with the strength of the colony tissues, the glue attaching Botrylloides sp. to the substratum is very weak. This relative weakness may protect the soft-bodied colonies from damage if they are ripped from their host. For sessile animals, such a weak-glue ‘strategy’ is only effective if the animals can later reattach to a substratum. By detaching Botrylloides sp. colonies from host eelgrass blades and allowing them to reattach, before measuring peel strengths, we learned that the initial reattachment of a colony depends upon rapid new growth of the colony rather than on fresh secretion of glue beneath old zooids. We also found that the propagation peel force necessary to remove Botrylloides sp. from different substrata (e.g. mussel shells, barnacle basal plates or eelgrass blades) depends upon the surface texture of the host. Thus, the overall tenacity of a colony is affected by the types of substrata that it overgrows.
Flight of the Vampire: Ontogenetic Gait-Transition in Vampyroteuthis Infernalis (Cephalopoda: Vampyromorpha)
Authors: Seibel Brad A. , Thuesen Erik V. , Childress James J.
Published: April 2021

Vampyroteuthis infernalis is a cosmopolitan cephalopod that lives in the oxygen minimum layer between 600 and 800 m depth. Morphometric and physiological studies have indicated that V. infernalis has little capacity for jet propulsion and has the lowest metabolic rate ever measured for a cephalopod. Because fin swimming is inherently more efficient than jet propulsion, some of the reduction in energy usage relative to other cephalopods may result from the use of fins as the primary means of propulsion. V. infernalis undergoes a rapid metamorphosis which consists of changes in the position, size and shape of the fins. This suggests that there are changes in the selective factors affecting locomotion through ontogeny. The present study describes these changes in relation to models for underwater ‘flight’. Citrate synthase (CS) and octopine dehydrogenase (ODH) activities, indicative of aerobic and anaerobic metabolism, respectively, were measured in fin, mantle and arm tissue across a range of body size of four orders of magnitude. The low enzymatic activities in both posterior and anterior fin tissue and the relatively high activity in mantle muscle prior to metamorphosis indicate that jet propulsion using mantle contraction is the primary means of propulsion in juvenile V. infernalis. The increase in CS activity with size after metamorphosis suggests an increased use of the fins for lift-based propulsion. Fin swimming appears to be the primary means of propulsion at all adult sizes. The negative allometry of CS activity in mantle and arm muscle is consistent with the scaling of oxygen consumption previously measured for V. infernalis and with the scaling of aerobic metabolism observed in most animals. The unusual positive allometry of fin muscle CS activity suggests that the use of fins is either relatively more important or more costly in larger animals. Positive scaling of ODH activity in all tissues suggests that fin propulsion, jet propulsion and medusoid ‘bell-swimming’ are all important for burst escape responses. Enzyme activities in Cirrothauma murrayi are consistent with fin-swimming observed from submersibles, while those in Opisthoteuthis californiana suggest a strong reliance on medusoid swimming using the arms. The transition from jet propulsion to paired-fin ‘flight’ with increasing body size in Vampyroteuthis infernalis appears functionally to be an ontogenetic ‘gait-transition’.
Hydrodynamic effect of a satellite transmitter on a juvenile green turtle (Chelonia mydas)
Authors: Watson Kennard P. , Granger Robert A.
Published: April 2021

Wind tunnel tests were performed to measure the effect of a satellite transmitter on a juvenile green turtle (Chelonia mydas). A full-scale turtle model was constructed from an 11.5 kg specimen with a 48 cm carapace length, and a transmitter model was constructed from a Telonics ST-6. The turtle model was tested in a wind tunnel with and without the transmitter, which was mounted on the forward, topmost part of the carapace. Drag, lift and pitch moment were measured for several speeds and flow angles, and the data were scaled for application to the marine environment. At small flow angles representative of straight-line swimming, the transmitter increased drag by 27–30 %, reduced lift by less than 10 % and increased the pitch moment by 11–42 %. On the basis of the drag data at zero angle of attack, it is estimated that the backpack will reduce swimming speed by 11 %, assuming that the turtle produces the same thrust with the unit attached. The drag data are also used to estimate the effect of a transmitter on the swimming energetics of an adult green turtle. Design guidelines are included to minimize the adverse forces and moments caused by the transmitter.
Voltage-activated currents in identified giant interneurons isolated from adult crickets Gryllus bimaculatus
Authors: Kloppenburg Peter , Hörner Michael
Published: April 2021

The electrophysiological properties of cultured giant interneurons isolated from the terminal ganglion of adult crickets (Gryllus bimaculatus) were investigated using whole-cell patch-clamp techniques. To allow for unequivocal identification of these interneurons in cell culture, a protocol for fast and selective labeling of their cell bodies was established. Prior to cell dissociation, the giant interneurons were backfilled through their axons in situ with a fluorescent dye (dextran tetramethylrhodamine). In primary cell cultures, the cell bodies of giant interneurons were identified among a population of co-cultured neurons by their red fluorescence.

Action potentials were recorded from the cell bodies of the cultured interneurons suggesting that several types of voltage-activated ion channels exist in these cells. Using voltage-clamp recording techniques, four voltage-activated currents were isolated and characterized.

The giant interneurons express at least two distinct K+ currents: a transient current that is blocked by 4-aminopyridine (4×10−3 mol l−1) and a sustained current that is partially blocked by tetraethylammonium (3×10−2 mol l−1) and quinidine (2×10−4 mol l−1). In addition, a transient Na+ current sensitive to 10−7 mol l−1 tetrodotoxin and a Ca2+ current blocked by 5×10−4 mol l−1 CdCl2 have been characterized. This study represents the first step in an attempt to analyze the cellular and ionic mechanisms underlying plasticity in the well-characterized and behaviorally important giant interneuron pathway in insects.
Effects of heat shock and hypoxia on protein synthesis in rainbow trout (Oncorhynchus mykiss) cells
Authors: Airaksinen Susanna , Råbergh Christina M. I. , Sistonen Lea , Nikinmaa Mikko
Published: April 2021

We examined the effects of heat stress (from 18 °C to 26 °C) and low oxygen tension (1 % O2=1 kPa) on protein synthesis in primary cultures of hepatocytes, gill epithelial cells and fibroblast-like RTG-2 cells of rainbow trout Oncorhynchus mykiss. All these cell types displayed elevated levels of 67, 69 and 92 kDa proteins, whereas a 104 kDa protein was induced only in RTG-2 cells. Hypoxia induced a cell-type-specific response, increasing the synthesis of 36, 39 and 51 kDa proteins in the gill epithelial cells. The regulation of the heat-shock response in fish hepatocytes showed that an HSF1-like factor is involved in the transcriptional induction of the hsp70 gene. Consequently, there was a pronounced accumulation of hsp70 mRNA. Furthermore, the kinetics of activation of DNA binding and the increase in hsp70 gene expression showed a remarkable correlation, indicating that hsp70 expression is regulated at the transcriptional level in these trout cells.
Purification and cloning of the salivary nitrophorin from the hemipteran Cimex lectularius
Authors: Valenzuela Jesus G. , Ribeiro José M. C.
Published: April 2021

Cimex lectularius and Rhodnius prolixus contain salivary nitric oxide (NO) that may help them to feed on their vertebrate hosts by promoting vasodilation and inhibiting platelet aggregation. Salivary NO is associated with heme proteins (nitrophorins) that store and transport NO from the insect salivary glands to the skin of the host. In this study, the salivary nitrophorin of Cimex lectularius was purified by DEAE chromatography and reverse-phase high-performance liquid chromatography. The purified nitrophorin had a molecular mass of 32.9 kDa. The DEAE-purified hemoprotein was able to bind NO, and this binding shifted the absorption maximum from 388 nm to 438 nm. The ratio of heme to apoprotein was estimated to be of 1:1. A cDNA clone of 1079 base pairs was sequenced and was found to code for a protein with a molecular mass of 31.7 kDa. The clone sequence was in agreement with the internal peptide sequences obtained from the purified protein. Sequencing of the isolated clone indicates high similarity to several inositol phosphatases; however, no significant similarities emerged when the sequence of C. lectularius nitrophorin was compared with that of R. prolixus nitrophorin, the only other nitrophorin known in insect saliva. Because C. lectularius and R. prolixus belong to two different families of Hemiptera that evolved independently to blood feeding, a case is made for the convergent evolution of these two insect nitrophorins.
Kinematics, Muscular Activity and Propulsion in Gopher Snakes
Authors: Moon Brad R. , Gans Carl
Published: April 2021

Previous studies have addressed the physical principles and muscular activity patterns underlying terrestrial lateral undulation in snakes, but not the mechanism by which muscular activity produces curvature and propulsion. In this study, we used synchronized electromyography and videography to examine the muscular basis and propulsive mechanism of terrestrial lateral undulation in gopher snakes Pituophis melanoleucus affinis. Specifically, we used patch electrodes to record from the semispinalis, longissimus dorsi and iliocostalis muscles in snakes pushing against one or more pegs. Axial bends propagate posteriorly along the body and contact the pegs at or immediately posterior to an inflection of curvature, which then reverses anterior to the peg. The vertebral column bends broadly around a peg, whereas the body wall bends sharply and asymmetrically around the anterior surface of the peg. The epaxial muscles are always active contralateral to the point of contact with a peg; they are activated slightly before or at the point of maximal convexity and deactivated variably between the inflection point and the point of maximal concavity. This pattern is consistent with muscular shortening and the production of axial bends, although variability in the pattern indicates that other muscles may affect the mechanics of the epaxial muscles. The kinematic and motor patterns in snakes crawling against experimentally increased drag indicated that forces are produced largely by muscles that are active in the axial bend around each peg, rather than by distant muscles from which the forces might be transmitted by connective tissues. At each point of force exertion, the propulsive mechanism of terrestrial lateral undulation may be modeled as a type of cam-follower, in which continuous bending of the trunk around the peg produces translation of the snake.
Mechanical Properties of the Tadpole Tail Fin
Authors: Doherty Penny A. , Wassersug Richard J. , Lee J. Michael
Published: April 2021

The tadpole tail fin is a simple double layer of skin overlying loose connective tissue. Collagen fibres in the fin are oriented at approximately ±45 ° from the long axis of the tail.

Three tests were conducted on samples of the dorsal tail fin from 6–10 Rana catesbeiana tadpoles to establish the fin’s viscoelastic properties under (1) large-deformation cyclic loading at 1 and 3 Hz, (2) small-deformation forced vibration at 1 and 3 Hz, and (3) stress relaxation under a 0.1 s loading time. The fin was very fragile, failing easily under tensile loads less than 7 g. It was also strikingly viscoelastic, as demonstrated by 72±1 % hysteresis loss (at 3 Hz), 16±3 % stress remaining after 100 s of stress relaxation and a phase angle of 18±1 ° in forced vibration. As a consequence of its viscoelastic properties, the fin was three times stiffer in small than in large deformation. This may account for the ability of the fin to stay upright during normal undulatory swimming, despite the absence of any skeletal support.

Tadpoles in nature are often found with damaged tails. We suggest that the unusually viscoelastic and fragile nature of the fin helps tadpoles escape the grasp of predators. Because the fin deforms viscoelastically and tears easily, tadpoles can escape predators and survive otherwise lethal attacks with only minor lacerations to the fin. Recent studies have shown that certain tadpoles develop taller fins in the presence of predators. This developmental plasticity is consistent with the tail fin acting as a protective but expendable ‘wrap’ around the core muscle tissue.
Resistance Reflex That Maintains Upright Head Posture in the Flesh Fly Neobellieria Bullata (Sarcophagidae)
Authors: Gilbert Cole , Bauer Eric
Published: April 2021

In flesh flies Neobellieria bullata, we investigated a resistance reflex that maintains upright head posture around the roll axis relative to the thorax. The gain of the reflex depends upon the fly’s behavioral state: moving flies immediately correct 90 % of the amplitude of experimentally imposed roll perturbations, returning the head almost to the fully upright position; motionless flies allow perturbations to persist for minutes before correcting only 70 % of perturbation amplitude.

To investigate the role of various neural pathways, we examined the control of head posture after sectioning relevant propriosensory or motor nerves. Excision of the prosternal chordotonal organ causes no decrements in the control of head posture. Unilateral deafferentation of a cervical propriosensory organ, the prosternal organ, induces roll towards the cut side. Unilateral section of the frontal nerve, a mixed motor nerve that supplies the neck depressors and levators, leads to unilateral deficits in correcting perturbations towards the contralateral side. After bilateral propriosensory or frontal motor nerve section, approximately 40 % of perturbation amplitude is still corrected. To determine the contributions of the passive elastic properties of the neck skeleto-muscular system, flies were tested under reversible nitrogen anesthesia. They immediately corrected 40 % of perturbation amplitude. Taken together, the results demonstrate that passive elasticity plus active prosternal nerve afference to contralateral depressors innervated by the frontal nerve in combination constitute a sufficient and necessary reflex loop to control head roll posture.
Specific Behavioural Responses Triggered by Identified Mechanosensory Receptor Cells in the Apical Field of the Giant Rotifer Asplanchna Sieboldi
Authors: Joanidopoulos Konstantin D. , Marwan Wolfgang
Published: April 2021

The giant rotifer Asplanchna sieboldi swims by the propulsive effect of thousands of cilia arrayed in clusters around the apical field, which has several mechanosensory structures (sensilla) located at defined positions. Males and females differ in both their patterns of behaviour and their sensory receptor equipment. Unstimulated males swim straight with occasional spontaneous changes in direction until they hit an obstacle with their apical field. Depending on the direction and the strength of the mechanical interference, the animals show different behavioural responses. To analyse the effect of excitation of the apical mechanosensitive sensilla on these responses, males were held on microcapillaries, and the sensitivity of individual sensilla was assayed using micromanipulator-mediated mechanical stimulation. Stimulation of each of the four different types of sensillum triggered a specific and well-defined initial behavioural response. Individual animals behaved identically with respect to the receptor specificity of the responses. The behaviour of free-swimming males upon contact with obstacles or females is discussed on the basis of these results.
Comparative Kinematics and Hydrodynamics of Odontocete Cetaceans: Morphological and Ecological Correlates With Swimming Performance
Authors: Fish Frank E.
Published: April 2021

Propulsive morphology and swimming performance were compared for the odontocete cetaceans Delphinapterus leucas, Orcinus orca, Pseudorca crassidens and Tursiops truncatus. Morphological differences were apparent among the whales. The general body contour and low-aspect-ratio caudal flukes of D. leucas indicated that this species was a low-performance swimmer compared with the other species. Propulsive motions were video-taped as animals swam steadily in large pools. Video tapes were analyzed digitally using a computerized motion-analysis system. Animals swam at relative velocities ranging from 0.4 to 2.4 body lengths s−1. The stroke amplitude of the flukes decreased linearly with velocity for D. leucas, but amplitude remained constant for the other species. Tail-beat frequencies were directly related to relative swimming velocity, whereas the pitch angle of the flukes was inversely related to relative swimming velocity. Unsteady lifting-wing theory was used with regression equations based on kinematics to calculate thrust power output, drag coefficients and propulsive efficiency. Compared with other species, O. orca generated the largest thrust power (36.3 kW) and had the lowest drag coefficient (0.0026), whereas T. truncatus displayed the largest mass-specific thrust power (23.7 W kg−1) and P. crassidens had the highest efficiency (0.9). D. leucas did not swim as rapidly as the other species and had a comparatively higher minimum drag coefficient (0.01), lower mass-specific thrust power (5.2 W kg−1) and lower maximum efficiency (0.84). Minimum drag coefficients were associated with high swimming speeds, and maximum efficiencies corresponded with velocities in the range of typical cruising speeds. The results indicate that the kinematics of the propulsive flukes and hydrodynamics are associated with the swimming behaviors and morphological designs exhibited by the whales in this study, although additional factors will influence morphology.
Vasoactivity of Adenosine in the Trout (Oncorhynchus Mykiss) Coronary System: Involvement of Nitric Oxide and Interaction with Noradrenaline
Authors: Mustafa Tariq , Agnisola Claudio
Published: April 2021

A vasoconstrictory response to adenosine has been reported in coronary rings from fish. Since the reactivity of the large coronary arteries and the microcirculation may differ, the present study was undertaken to determine the role of adenosine in the intact coronary system of trout under constant pressure or flow using an isolated and non-working heart preparation. The involvement of nitric oxide (NO) and the interaction with noradrenaline were also studied. At 10−9 to 10−8 mol l−1, adenosine caused a vasoconstrictory response, whereas between 10−7 and 10−5 mol l−1 the response was predominantly vasodilative. Theophylline abolished both these responses to adenosine. The vasodilation induced by adenosine (at 10−5 mol l−1) was significantly reduced when the preparation was perfused under constant-flow than rather under constant-pressure conditions. The nitric oxide synthase inhibitor Nω-nitro-L-arginine (L-NA, 10−4 mol l−1) partially reduced the vasodilation induced by adenosine (at 10−5 mol l−1) under constant-pressure but not under constant-flow conditions. Perfusion of the intact coronary system with L-arginine or with adenosine significantly increased the rate of nitrite (NO2−) release, while perfusion with L-NA or theophylline reduced NO2− release. Chemical denudation of the coronary endothelium by CHAPS resulted in the loss of both the L-arginine- and adenosine-mediated vasodilation and the L-arginine-induced increase in the rate of NO2− release. Adenosine (10−5 mol l−1) offset and overrode the vasoconstriction induced by 10−7 mol l−1 noradrenaline. L-NA inhibited only the adenosine-induced vasodilation but not the ability to offset noradrenaline vasoconstriction, excluding the involvement of NO in the interaction between adenosine and noradrenaline.