bluuebunny/crossref_metadata_2025 huggingface dataset:
Crushing Motor Patterns in Drum (Teleostei: Sciaenidae): Functional Novelties Associated with Molluscivory
Authors: Grubich Justin R.
Published: April 2021

This study explores the evolution of molluscivory in the marine teleost family Sciaenidae by comparing the motor activity patterns of the pharyngeal muscles of two closely related taxa, the molluscivorous black drum (Pogonias cromis) and the generalist red drum (Sciaenops ocellatus). Muscle activity patterns were recorded simultaneously from eight pharyngeal muscles. Electromyographic (EMG) activity was recorded during feeding on three prey types that varied in shell hardness. Canonical variate and discriminant function analyses were used to describe the distinctness of drum pharyngeal processing behaviors. Discriminant functions built of EMG timing variables were more accurate than muscle activity intensity at identifying cycles by prey type and species. Both drum species demonstrated the ability to modulate pharyngeal motor patterns in response to prey hardness. The mean motor patterns and the canonical variate space of crushing behavior indicated that black drum employed a novel motor pattern during molluscivory. The mollusc-crushing motor pattern of black drum is different from other neoteleost pharyngeal behaviors in lacking upper jaw retraction by the retractor dorsalis muscle. This functional modification suggests that crushing hard-shelled marine bivalves requires a ‘vice-like’ compression bite in contrast to the shearing forces that are applied to weaker-shelled fiddler crabs by red drum and to freshwater snails by redear sunfish.
K + Currents in Cultured Neurones From a Polyclad Flatworm
Authors: Buckingham Steven D. , Spencer Andrew N.
Published: April 2021

Cells from the brain of the polyclad flatworm Notoplana atomata were dispersed and maintained in primary culture for up to 3 weeks. Whole-cell patch-clamp of presumed neurones revealed outwardly directed K+ currents that comprised, in varying proportions, a rapidly activating (time constant τ=0.94±0.79 ms; N=15) and inactivating (τ=26.1±1.9 ms; N=22) current and a second current that also activated rapidly (τ=1.1±0.2 ms; N=9) (means ± S.E.M.) but did not inactivate within 100 ms. Both current types activated over similar voltage ranges. Activation and steady-state inactivation overlap and are markedly rightward-shifted compared with most Shaker-like currents (half-activation of 16.9±1.9 mV, N=7, half-inactivation of −35.4±3.0 mV, N=5). Recovery from inactivation was rapid (50±2.5 ms at −90 mV). Both currents were unaffected by tetraethylammonium (25 mmol l−1), whereas 4-aminopyridine (10 mmol l−1) selectively blocked the inactivating current. The rapidly inactivating current, like cloned K+ channels from cnidarians and certain cloned K+ channels from molluscs and the Kv3 family of vertebrate channels, differed from most A-type K+ currents reported to date. These findings suggest that K+ currents in Notoplana atomata play novel roles in shaping excitability properties.
Auditory Symmetry Analysis
Authors: Faure Paul A. , Hoy Ronald R.
Published: April 2021

The study of biological symmetry continues to be an important and active area of research, yet in the hearing sciences there are no established quantitative methods for measuring auditory asymmetries and dissimilarities in threshold tuning curves (i.e. audiograms). Using a paired design and adopting methods from the analysis of fluctuating asymmetry, we describe methods for auditory researchers interested in delineating auditory asymmetries and comparing tuning curves, behavioral or neural. We illustrate the methods using audiograms of the prothoracic T-cell interneuron in a nocturnal katydid (Neoconocephalus ensiger). The results show that 87–92 % of T-cells had right-minus-left threshold asymmetries no larger than expected from measurement error alone. Thus, apart from small random fluctuating asymmetries, T-cell pairs in N. ensiger showed no sensory bias and were bilaterally symmetrical from 5 to 100 kHz. The sensitivity of the methods for detecting tuning curve dissimilarities was confirmed in a sound lateralization paradigm by comparing the ‘symmetry’ (i.e. similarity) of T-cell tuning curves measured at 0 ° stimulation with tuning curves measured at 90 ° stimulation for the same T-cell. The results show that T-cell thresholds measured frontally (0 °) were significantly higher than those measured laterally (90 °), particularly for ultrasonic frequencies. Statistically, the directional shift (increase) in auditory thresholds was detected as a directional asymmetry in T-cell tuning, whose origin and functional significance to an insect behaving normally are discussed. The paper discusses practical considerations for detecting auditory asymmetries and tuning curve dissimilarities in general, and closes by questioning the relevance of auditory symmetry for sound localization in both vertebrates and insects.
Neuroethology of the Katydid T-Cell: II. Responses to Acoustic Playback of Conspecific and Predatory Signals
Authors: Faure Paul A. , Hoy Ronald R.
Published: April 2021

Although early work on the tettigoniid T large fiber suggested that it might mediate early-warning and escape behavior in katydids, the majority of research thereafter has focused on the ability of the T-cell to detect, localize and/or discriminate mate-calling song. Interestingly, T-cell responses to conspecific song are rarely examined for more than a few seconds, despite the fact that many katydids sing for minutes or hours at a time. In this paper, the second of a pair examining the physiology of the T-cell in Neoconocephalus ensiger, we recorded T-cell responses using longer-duration playbacks (3 min) of conspecific song (Katydid signal 30 ms syllables, 9–25 kHz bandwidth, 12–15 kHz peak frequency) and two types of bat-like ultrasound, a 10 ms, 80→30 kHz frequency-modulated sweep (Bat 10 signal) and a 30 ms, 80→30 kHz frequency-modulated sweep (Bat 30 signal). Spiking responses were distinctly biased towards the short-duration ultrasonic signal, with more spikes per pulse, at a shorter spike latency and at a higher instantaneous firing frequency to the Bat 10 signal than to the Katydid signal or, surprisingly, to the Bat 30 signal. The ability of the T-cell to encode the temporal pattern of the stimulus was particularly striking. Only for the predatory bat signals did T-cell spiking faithfully copy the stimulus; playbacks of conspecific song resulted in significantly weaker spiking responses, particularly in male katydids. The results demonstrate that responses from the T-cell alone may be sufficient for katydids to discriminate biologically relevant signals pertinent to the phonotactic behavior patterns involved in mate attraction and predator avoidance.
ELectroreception In Gymnotus Carapo: Pre-Receptor Processing And The Distribution Of Electroreceptor Types
Authors: Castelló María E. , Aguilera Pedro A. , Trujillo-Cenóz Omar , Caputi Angel A.
Published: April 2021

This paper describes the peripheral mechanisms involved in signal processing of self- and conspecific-generated electric fields by the electric fish Gymnotus carapo. The distribution of the different types of tuberous electroreceptor and the occurrence of particular electric field patterns close to the body of the fish were studied. The density of tuberous electroreceptors was found to be maximal on the jaw (foveal region) and very high on the dorsal region of the snout (parafoveal region), decaying caudally. Tuberous type II electroreceptors were much more abundant than type I electroreceptors. Type I electroreceptors occurred exclusively on the head and rostral trunk regions, while type II electroreceptors were found along as much as 90 % of the fish. Electrophysiological data indicated that conspecific- and self-generated electric currents are ‘funnelled’ by the high conductivity and geometry of the body of the fish. These currents are concentrated at the peri-oral zone, where most electroreceptors are located. Moreover, within this region, field vector directions were collimated, constituting the most efficient stimulus for electroreceptors. It can be concluded that the passive properties of the fish tissue represent a pre-receptor device that enhances exafferent and reafferent electrical signals at the fovea–parafoveal region.
The Behavioral Detection Of Binary Mixtures Of Amino Acids And Their Individual Components By Catfish
Authors: Valentinčič T. , Kralj J. , Stenovec M. , Koce A. , Caprio J.
Published: April 2021

The question of whether a binary mixture of amino acids is detected by fish as a unique odor or whether the qualities of the individual components are retained within the mixture was investigated in channel (Ictalurus punctatus) and brown bullhead (Ameiurus nebulosus) catfish, species that are highly similar in their olfactory receptor and behavioral responses to amino acid odorants. Catfish respond with greater appetitive food-searching (swimming) behavior to amino-acid-conditioned olfactory stimuli than to non-conditioned amino acids. In the present study, appetitive food-searching behavior was measured by counting the number of turns of the fish greater than 90 ° within 90 s of stimulus onset and, in some tests, by video tracking. The two methods yielded highly correlated results. Channel catfish conditioned to a binary mixture composed of equimolar amino acids responded with searching behavior to the amino acid that produced the larger-amplitude electro-olfactogram (EOG) response as they did to the conditioned stimulus. In further studies, bullhead catfish were conditioned either to a binary mixture or to a single amino acid and tested to determine whether a binary mixture was detected as the component evoking the larger EOG response. In all initial tests (trials 1–3), the more stimulatory component of a binary mixture was not discriminated from the binary mixture; however, the less stimulatory component and all other amino acids tested were discriminated from the mixture. By increasing the concentration of the originally less potent component in a binary mixture, making it the more stimulatory compound, it was now detected as not significantly different from the binary mixture; however, the original more potent component (i.e. now the less potent stimulus) was detected as significantly different from the mixture. However, with 5–10 additional discrimination training trials, the less stimulatory component in a binary mixture influenced the perception of the binary mixture because the binary mixture was no longer detected only as its more stimulatory component. The data suggest that a two-step learning process occurs within the olfactory bulb and possibly higher-order telencephalic nuclei.
Mitochondrial Oxyconformity and Cold Adaptation in the Polychaete Nereis Pelagica and the Bivalve Arctica Islandica From The Baltic And White Seas
Authors: Tschischka Katja , Abele Doris , Pörtner Hans O.
Published: April 2021

The rates of oxygen uptake of the marine polychaete Nereis pelagica and the bivalve Arctica islandica depend on the availability of ambient oxygen. This is manifest both at the tissue level and in isolated mitochondria studied between oxygen tensions of 6.3 and 47.6 kPa (47–357 mmHg). Oxyconformity was found in both Baltic Sea (Kiel Bight) and cold-adapted White Sea populations of the two species. However, mitochondria isolated from White Sea specimens of N. pelagica and A. islandica showed a two-to threefold higher aerobic capacity than mitochondria prepared from Baltic Sea specimens. We tested whether mitochondrial oxyconformity can be explained by an additional electron pathway that is directly controlled by . Mitochondrial respiration of both invertebrate species was inhibited by cyanide (KCN) and by salicylhydroxamic acid (SHAM). The overall rate of mitochondrial oxygen consumption increased at high . Phosphorylation efficiency (ADP/O ratio) decreased at elevated (27.5–47.6 kPa, 206–357 mmHg), regardless of whether malate or succinate was used as a substrate. In contrast to the invertebrate mitochondria studied, mitochondria isolated from bovine heart, as an oxyregulating control species, did not show an elevated rate of oxygen uptake at high in any respiratory state, with the exception of state 2 malate respiration. In addition, rates of ATP formation, respiratory control ratios (RCR) and ADP/O ratios remained virtually unchanged or even tended to decreased. In conclusion, the comparison between mitochondria from oxyregulating and oxyconforming organisms supports the existence of an alternative oxidase in addition to the classical cytochrome c oxidase. In accordance with models discussed previously, oxidative phosphorylation does not explain the rate of mitochondrial oxygen consumption during progressive activation of the alternative electron transport system. We discuss the alternative system, thought to be adaptive in confined, usually hypoxic environments, where excess oxygen can be eliminated and oxygen levels can be kept low by an increase in the rate of oxygen consumption, thereby minimizing the risk of oxidative stress.
Cloning and Characterization of Sarco/Endoplasmic Reticulum Ca2+ -ATPase (Serca) From Crayfish Axial Muscle
Authors: Zhang Zhiping , Chen Dongdong , Wheatly Michele G.
Published: April 2021

The discontinuous pattern of muscle growth during the moulting cycle of a freshwater crustacean (the crayfish Procambarus clarkii) was used as a model system to examine the regulation of the expression of Sarco/Endoplasmic Reticulum Ca2+ -ATPase (SERCA). We describe the cloning, sequencing and characterization of a novel SERCA cDNA (3856 bp) obtained from crayfish axial abdominal muscle by reverse transcription/polymerase chain reaction (RT-PCR) followed by rapid amplification of cDNA ends (RACE). This complete sequence contains a 145 base pair (bp) noncoding region at the 5′ end, a 3006 bp open reading frame coding for 1002 amino acid residues with a molecular mass of 110 kDa and 705 bp of untranslated region at the 3′ end. This enzyme contains all the conserved domains found in ‘P’-type ATPases, and the hydropathy profile suggests a transmembrane organization typical of other SERCAs. It exhibits 80 % amino acid identity with Drosophila melanogaster SERCA, 79 % identity with Artemia franciscana SERCA, 72 % identity with rabbit fast-twitch muscle neonatal isoform SERCA1b, 71 % identity with slow-twitch muscle isoform SERCA2 and 67 % identity with SERCA3. Sequence alignment revealed that regions anchoring the cytoplasmic domain in the membrane were highly conserved and that most differences were in the NH2 terminus, the central loop region and the COOH terminus. Northern analysis of total RNA from crayfish tissues probed with the 460 bp fragment initially isolated showed four bands (7.6, 7.0, 5.8 and 4.5 kilobases) displaying tissue-specific expression. SERCA was most abundant in muscle (axial abdominal, cardiac and stomach), where it is involved in Ca2+ resequestration during relaxation, and in eggs, where it may be implicated in early embryogenesis. The level of SERCA mRNA expression in axial abdominal muscle varied during the moulting cycle as determined by slot–blot analysis. SERCA expression was greatest during intermoult and decreased to approximately 50 % of this level during pre- and postmoult. Patterns of gene expression for SERCA and other sarcomeric proteins during the crustacean moulting cycle may be regulated by ecdysteroids and/or mechanical stimulation.
Sources and Mechanisms of Inorganic Carbon Transport for Coral Calcification and Photosynthesis
Authors: Furla Paola , Galgani Isabelle , Durand Isabelle , Allemand Denis
Published: April 2021

The sources and mechanisms of inorganic carbon transport for scleractinian coral calcification and photosynthesis were studied using a double labelling technique with H14 CO3 and 45 Ca. Clones of Stylophora pistillata that had developed into microcolonies were examined. Compartmental and pharmacological analyses of the distribution of 45 Ca and H14 CO3 in the coelenteron, tissues and skeleton were performed in dark or light conditions or in the presence of various seawater HCO3− concentrations.

For calcification, irrespective of the lighting conditions, the major source of dissolved inorganic carbon (DIC) is metabolic CO2 (70–75 % of total CaCO3 deposition), while only 25–30 % originates from the external medium (seawater carbon pool). These results are in agreement with the observation that metabolic CO2 production in the light is at least six times greater than is required for calcification. This source is dependent on carbonic anhydrase activity because it is sensitive to ethoxyzolamide. Seawater DIC is transferred from the external medium to the coral skeleton by two different pathways: from sea water to the coelenteron, the passive paracellular pathway is largely sufficient, while a DIDS-sensitive transcellular pathway appears to mediate the flux across calicoblastic cells. Irrespective of the source, an anion exchanger performs the secretion of DIC at the site of calcification. Furthermore, a fourfold light-enhanced calcification of Stylophora pistillata microcolonies was measured. This stimulation was only effective after a lag of 10 min. These results are discussed in the context of light-enhanced calcification.

Characterisation of the DIC supply for symbiotic dinoflagellate photosynthesis demonstrated the presence of a DIC pool within the tissues. The size of this pool was dependent on the lighting conditions, since it increased 39-fold after 3 h of illumination. Passive DIC equilibration through oral tissues between sea water and the coelenteric cavity is insufficient to supply this DIC pool, suggesting that there is an active transepithelial absorption of inorganic carbon sensitive to DIDS, ethoxyzolamide and iodide. These results confirm the presence of CO2-concentrating mechanisms in coral cells. The tissue pool is not, however, used as a source for calcification since no significant lag phase in the incorporation of external seawater DIC was measured.
Evolution of Air-Breathing and Central CO2/H+ Respiratory Chemosensitivity: New Insights From an Old Fish?
Authors: Wilson R. J. A. , Harris M. B. , Remmers J. E. , Perry S. F.
Published: April 2021

While little is known of the origin of air-breathing in vertebrates, primitive air breathers can be found among extant lobe-finned (Sarcopterygii) and ray-finned (Actinopterygii) fish. The descendents of Sarcopterygii, the tetrapods, generate lung ventilation using a central pattern generator, the activity of which is modulated by central and peripheral CO2/H+ chemoreception. Air-breathing in Actinopterygii, in contrast, has been considered a ‘reflexive’ behaviour with little evidence for central CO2/H+ respiratory chemoreceptors. Here, we describe experiments using an in vitro brainstem preparation of a primitive air-breathing actinopterygian, the longnose gar Lepisosteus osseus. Our data suggest (i) that gill and air-breathing motor patterns can be produced autonomously by the isolated brainstem, and (ii) that the frequency of the air-breathing motor pattern is increased by hypercarbia. These results are the first evidence consistent with the presence of an air-breathing central pattern generator with central CO2/H+ respiratory chemosensitivity in any primitive actinopterygian fish. We speculate that the origin of the central neuronal controller for air-breathing preceded the divergence of the sarcopterygian and actinopterygian lineages and dates back to a common air-breathing ancestor.
Catalytic Activity and Heat Production by the Ca2+-ATPase from Sea Cucumber (Ludwigothurea Grisea) LONGITUDINAL SMOOTH MUSCLE: MODULATION BY MONOVALENT CATIONS
Authors: Landeira-Fernandez Ana Maria , Galina Antonio , De Meis Leopoldo
Published: April 2021

In muscle cells, excitation–contraction coupling involves the translocation of Ca2+ between intracellular compartments and the cytosol. Heat derived from the hydrolysis of ATP by the sarcoplasmic reticulum Ca2+-ATPase of skeletal muscle plays an important role in the thermoregulation and energy balance of the cell. Although several Ca2+-ATPase isoforms have been described in vertebrates, little is known about Ca2+ transport in invertebrates. In this report, a Ca2+-ATPase is identified in the microsomal fraction obtained from sea cucumber (Ludwigothurea grisea) smooth muscle. The activity of this enzyme is enhanced three-to fivefold by K+ and Na+. During Ca2+ transport, the ATPase can synthesise ATP from ADP and inorganic phosphate (Pi) using the energy derived from the Ca2+ gradient formed across the microsomal membrane (ATP↔Pi exchange). The apparent affinity of the enzyme for Pi is increased by more than one order of magnitude by K+. In the presence of K+, the fraction of ATP synthesised during the exchange reaction by sea cucumber microsomes was found to be larger than that measured in microsomes derived from either rabbit or trout muscle. Like the isoforms found in skeletal muscle, the sea cucumber Ca2+-ATPase can convert osmotic energy into heat. The amount of heat produced after the hydrolysis of each ATP molecule increases two-to threefold when a Ca2+ gradient is formed across the microsomal membrane.
The cardiovascular responses of the red-eared slider (Trachemys scripta) acclimated to either 22 or 5 °C: I. Effects of anoxic exposure on in vivo cardiac performance
Authors: Hicks J. M. T. , Farrell A. P.
Published: April 2021

The extreme anoxia-tolerance of freshwater turtles under cold conditions is well documented, but little is known about their cardiac performance in such situations. Using chronic catheterization techniques, we measured systemic cardiac power output (POsys), systemic cardiac output (Q̇sys), heart rate (fH), systemic stroke volume (Vs,sys), systemic resistance (Rsys) and mean arterial pressure (Psys) in red-eared sliders (Trachemys scripta). The effects of cold acclimation and anoxic exposure were studied. Turtles were acclimated to either 22 °C or 5 °C, and the anoxic exposure was either acute (6 h) at 22 °C or chronic (3 weeks) at 5 °C. Cold acclimation alone decreased POsys by 15-fold, representing a Q10 of 8.8. In addition, fH and Vs,sys decreased significantly, while Rsys increased and moderated the arterial hypotension. Acute and chronic anoxic exposures significantly decreased POsys, Vs,sys, fH and Psys and increased Rsys. But the changes were qualitatively much larger with chronic anoxia. For example, acute anoxia in 22 °C-acclimated turtles decreased POsys by 6.6-fold, whereas chronic anoxia in 5 °C-acclimated turtles decreased POsys by 20-fold. The remarkable cardiovascular down-regulation that accompanies long periods of cold anoxia in these turtles was characterized by comparing cardiovascular status during chronic anoxia at 5 °C with that during normoxia at 22 °C. Car.diac POsys was reduced 330-fold, through decreases in Qsys (120-fold), fH (24.2-fold), Vs,sys (5.7-fold) and Psys (2.2-fold), while Rsys was increased 64.6-fold. We also compared cardiac glycolytic rates by assuming that POsys was proportional to ATP supply and that glycolysis yielded 18 times less ATP per mole of glucose than oxidative metabolism. At 22 °C, the 6.6-fold decrease in POsys with anoxia suggests that a Pasteur effect was needed in cardiac tissues during acute anoxia. However, this would not be so with chronic anoxia at 5 °C because of the 22-fold decrease in POsys. We propose that the suppression of the Pasteur effect and the large Q10 values for cold acclimation would conserve glucose stores and enable turtles to withstand anoxia much longer under cold than under warm conditions.
Connections Between Thoraco-Coxal Proprioceptive Afferents and Motor Neurons in the Locust
Authors: Wildman Mark
Published: April 2021

The position of the coxal segment of the locust hind leg relative to the thorax is monitored by a variety of proprioceptors, including three chordotonal organs and a myochordotonal organ. The sensory neurons of two of these proprioceptors, the posterior joint chordotonal organ (pjCO) and the myochordotonal organ (MCO), have axons in the purely sensory metathoracic nerve 2C (N2C). The connections made by these afferents with metathoracic motor neurons innervating thoraco-coxal and wing muscles were investigated by electrical stimulation of N2C and by matching postsynaptic potentials in motor neurons with afferent spikes in N2C. Stretch applied to the anterior rotator muscle of the coxa (M121), with which the MCO is associated, evoked sensory spikes in N2C. Some of the MCO afferent neurons make direct excitatory chemical synaptic connections with motor neurons innervating the thoraco-coxal muscles M121, M126 and M125. Parallel polysynaptic pathways via unidentified interneurons also exist between MCO afferents and these motor neurons. Connections with the common inhibitor 1 neuron and motor neurons innervating the thoraco-coxal muscles M123/4 and wing muscles M113 and M127 are polysynaptic. Afferents of the pjCO also make polysynaptic connections with motor neurons innervating thoraco-coxal and wing muscles, but no evidence for monosynaptic pathways was found.
Identification of a Ubiquitous Family of Membrane Proteins and Their Expression in Mouse Brain
Authors: Grossman Tamar R. , Luque Juan M. , Nelson Nathan
Published: April 2021

A family of genes encoding membrane proteins with a unique structure has been identified in DNA and cDNA clones of various eukaryotes ranging from yeast to human. The nucleotide sequences of three novel cDNAs from Drosophila melanogaster and mouse were determined. The amino acid sequences of the two mouse proteins have human homologs. The gene (TMS1) encoding the yeast member of this family was disrupted, and the resulting mutant showed no significant phenotype under several stress conditions. The expression of the mouse genes TMS-1 and TMS-2 was examined by in situ hybridization of sections from brain, liver, kidney, heart and testis of an adult mouse as well as in a 1-day-old whole mouse. While the expression of TMS-2 was found to be restricted to the central nervous system, TMS-1 was also expressed in kidney and testis. The expression of TMS-1 and TMS-2 in the brain overlapped and was localized to areas associated with glutamatergic excitatory neurons, such as the hippocampus and cerebral cortex. High-magnification analysis indicated that both mRNAs are expressed in neurons. Semiquantitative analysis of mRNA expression was performed in various parts of the brain. The conservation, unique structure and localization in the mammalian brain of this novel protein family suggest an important biological role.
Cloning and Molecular Characterisation of the Trout (Oncorhynchus Mykiss) Vacuolar H+-Atpase B Subunit
Authors: Perry Steve F. , Beyers Matthew L. , Johnson Douglas A.
Published: April 2021

The current model of transepithelial ion movements in the gill of freshwater fish incorporates an apically oriented vacuolar H+-ATPase (H+V-ATPase; proton pump) that is believed to facilitate both acid excretion and Na+ uptake. To substantiate this model, we have cloned and sequenced a cDNA encoding the B subunit of the rainbow trout (Oncorhynchus mykiss) H+V-ATPase. The cloning of the B subunit enabled an examination by northern analysis of its tissue distribution and expression during external hypercapnia.

Degenerate oligonucleotide primers to the B subunit of the H+V-ATPase were designed and used in a semi-nested polymerase chain reaction (PCR) to amplify an 810 base pair (bp) product from a trout gill/kidney cDNA library. This PCR product was cloned and sequenced and then used to screen the same cDNA library. The assembled 2262 bp cDNA included an open reading frame coding for a deduced protein of 502 amino acid residues. A BLAST search of the GenBank nucleotide database revealed numerous matches to other vertebrate and invertebrate H+V-ATPase B subunits. Protein alignment demonstrated that the trout H+V-ATPase B subunit is more than 85 % identical and more than 90 % similar to those in other vertebrate species.

An initial analysis of H+V-ATPase mRNA tissue distribution revealed significant expression in blood. Although a comparison of perfused tissues (blood removed) with non-perfused tissues demonstrated no obvious contribution of the blood to total tissue H+-ATPase mRNA levels, all subsequent experiments were performed using perfused tissues. Levels of H+V-ATPase mRNA expression were high in the gill, kidney (anterior or posterior), intestine, heart and spleen, but lower in liver and white muscle. Exposure of the fish to 12 h of external hypercapnia (water ; 1 kPa) was associated with a transient increase (at 2 h) in the levels of H+V-ATPase B subunit mRNA in gill and kidney; liver mRNA levels were unaffected.

These results are consistent with the hypothesis of an apically localised plasma membrane H+V-ATPase in the freshwater trout gill and that the expression of this proton pump is increased during periods of acidosis, at least in part because of an increased steady-state level of H+V-ATPase mRNA.
Patterns of White Muscle Activity During Terrestrial Locomotion in the American Eel (Anguilla Rostrata)
Authors: Gillis Gary B.
Published: April 2021

Eels (Anguilla rostrata) are known to make occasional transitory excursions into the terrestrial environment. While on land, their locomotor kinematics deviate drastically from that observed during swimming. In this study, electromyographic (EMG) recordings were made from white muscle at various longitudinal positions in eels performing undulatory locomotion on land to determine the muscle activity patterns underlying these terrestrial movements. As during swimming, eels propagate a wave of muscle activity from anterior to posterior during terrestrial locomotion. However, the intensity of EMG bursts is much greater on land (on average approximately five times greater than in water). In addition, anteriorly located musculature has higher-intensity EMG bursts than posteriorly located muscle during locomotion on land. EMG duty cycle (burst duration relative to undulatory cycle time) is significantly affected by longitudinal position during terrestrial locomotion, and duty cycles are significantly greater on land (0.4–0.5 cycles) than in water (0.2–0.3 cycles). Finally, as in swimming, a phase shift in the timing of muscle activity exists such that posteriorly located muscle fibers become activated earlier in their strain cycle than do more anteriorly located fibers. However, fibers become activated much later in their muscle strain cycle on land than in water. Therefore, it is clear that, while eels propagate a wave of muscle activity posteriorly to generate backward-traveling waves that generate propulsive thrust both in water and on land, the specific patterns of timing and the intensity of muscle activity are substantially altered depending upon the environment. This suggests that physical differences in an animal’s external environment can play a substantial role in affecting the motor control of locomotion, even when similar structures are used to generate the propulsive forces.
Ecdysis of Decapod Crustaceans is Associated With a Dramatic Release of Crustacean Cardioactive Peptide into the Haemolymph
Authors: Phlippen Markus K. , Webster Simon G. , Chung J. Sook , Dircksen Heinrich
Published: April 2021

On the basis of detailed analyses of morphological characteristics and behavioural events associated with ecdysis in a crab (Carcinus maenas) and a crayfish (Orconectes limosus), a comprehensive substaging system has been introduced for the ecdysis stage of the moult cycle of these decapod crustaceans. In a remarkably similar stereotyped ecdysis sequence in both species, a passive phase of water uptake starting with bulging and rupture of thoracoabdominal exoskeletal junctions is followed by an active phase showing distinct behavioural changes involved in the shedding of the head appendages, abdomen and pereiopods. Together with an enzyme immunoassay for crustacean cardioactive peptide (CCAP), the substaging has been used to demonstrate a large, rapid and reproducible peak in haemolymph CCAP levels (increases of approximately 30-fold in the crab and more than 100-fold in the crayfish compared with intermoult titres) during the later stages of active ecdysis. We suggest that the release of CCAP (accumulated in late premoult) from the crab pericardial organs or the crayfish ventral nerve cord accounts for many of the changes in behaviour and physiology seen during ecdysis and that this neurohormone is likely to be of critical importance in crustaceans and other arthropods.
Agonistic Behaviour and Biogenic Amines in Shore Crabs Carcinus Maenas
Authors: Sneddon Lynne U. , Taylor Alan C. , Huntingford Felicity A. , Watson David G.
Published: April 2021

To investigate the role of certain neurohormones in agonistic behaviour, fights were staged between pairs of size-matched male shore crabs Carcinus maenas, and blood samples were taken immediately after the contests had been resolved. Samples were also taken from these crabs at rest (before and after fighting) and after walking on a treadmill. A control group of crabs also had samples taken on each experimental day. Concentrations of tyramine, dopamine, octopamine, serotonin (5-HT) and norepinephrine were determined in each blood sample using a gas chromatography/mass spectrometry (GC-MS) system. Norepinephrine was not detectable in any of the samples, but the standards were recovered. Tyramine values were not significantly different between the control group and the fought group, so tyramine does not appear to be important in agonistic behaviour. A comparison between the control and fought groups shows that fighting had an effect on the concentrations of octopamine, dopamine and 5-HT, but exercise only had an effect on octopamine levels, which showed a reduction from resting values in both winners and losers. Resting and post-fight concentrations of octopamine, dopamine and 5-HT were higher in winners than in losers. 5-HT concentration increased in the blood of fought crabs from resting values, whereas dopamine concentration decreased. In winners, octopamine concentrations decreased from resting values, but in losers octopamine levels increased from resting concentrations. The escalatory behaviour or intensity of fighting performed by winners and losers was related to dopamine levels but not to those of octopamine or 5-HT. Therefore, there appears to be a link between relative concentrations of these three amines (dopamine, octopamine and 5-HT) and fighting ability; the effects are not simply a result of activity. The better competitors have higher concentrations of these three amines at rest and after fighting.
Power Production During Steady Swimming in Largemouth Bass and Rainbow Trout
Authors: Coughlin David J.
Published: April 2021

Steady swimming in fishes is powered by the aerobic or red muscle, but there are conflicting theories on the relative roles of the anterior and posterior red muscle in powering steady swimming. To examine how red muscle is used to power steady swimming in rainbow trout (Oncorhynchus mykiss), electromyographic (EMG) and sonomicrometry recordings were made of muscle activity in vivo. These data were used in in vitro work-loop studies of muscle power production. Data on in vitro power production were also collected for largemouth bass (Micropterus salmoides) red muscle from previously published data on in vivo muscle activity. The in vivo data collected from swimming trout were similar to those for other species. The anterior red muscle of these fish has the longest duty cycle, the smallest phase shift between the onset of EMG activity and maximum muscle length during each tailbeat and undergoes the smallest strain or length change. For both trout and largemouth bass, work-loop experiments indicate that the majority of power for steady swimming is generated by the posterior muscle, as has been observed in other species.
Pinpointing Food Sources: Olfactory and Anemotactic Orientation in Desert Ants, Cataglyphis Fortis
Authors: Wolf Harald , Wehner Rüdiger
Published: April 2021

Desert ants, Cataglyphis fortis, search for a repeatedly visited food source by employing a combined olfactory and anemotactic orientation strategy (in addition to their visually based path-integration scheme). This behaviour was investigated by video-tracking consecutive foraging trips of individually marked ants under a variety of experimental conditions, including manipulations of the olfactory and wind-detecting systems of the ants. If the wind blows from a constant direction, ants familiar with the feeding site follow outbound paths that lead them into an area 0.5–2.5 m downwind of the feeding station. Here, the ants apparently pick up odour plumes emanating from the food source and follow these by steering an upwind course until they reach the feeder. If the food is removed, foragers usually concentrate their search movements within the area downwind of the feeding site. Only when the wind happens to subside or when tail-wind conditions prevail do the ants steer direct courses towards the food.

Elimination of olfactory input by clipping the antennal flagella, or of wind perception by immobilising the bases of the antennae, altered the foraging behaviour of the ants in ways that supported these interpretations. Ants with clipped flagella were never observed to collect food items.
Energy Storage by Passive Elastic Structures in the Mantle of Sepia Officinalis
Authors: Curtin N. A. , Woledge R. C. , Bone Q.
Published: April 2021

The passive elastic properties of the mantle of the cuttlefish Sepia officinalis have been characterized in experiments on intact mantle and on pieces cut from the mantle. The mantle was found to be very compliant over a wide range of circumferential strains, corresponding to a change in mantle circumferential strain of 0.45. Beyond this range of strain, the mantle was much stiffer, in both the circumferential direction, 0.542±0.025 MPa (mean ± S.E.M., N=51) and through the thickness of the mantle wall, 0.152±0.041 MPa (N=11). Almost 80 % of the work done on the tissue during compression in the circumferential direction was recovered during elastic recoil of the tissue; this elastic work could contribute to refilling the mantle after a jet. Our estimates of the work done during a cycle of jetting and refilling show that such elastic work is small (approximately 1 %) compared with the contractile work done by the circular muscle fibres. However, although the elastic work is almost negligible in the overall energy budget, it is probably sufficient to power refilling of the mantle.
Continuous Measurements of Instantaneous Heart Rate and its Fluctuations Before and After Hatching in Chickens
Authors: Moriya K. , Pearson J. T. , Burggren W. W. , Ar A. , Tazawa H.
Published: April 2021

There has been considerable interest in heart rate (fH) fluctuations in relation to cardiovascular control systems and foetal conditions during pregnancy in mammals. Prominent fluctuations in fH also occur in avian embryos, which are an important experimental model for studying developmental physiology. The present study determined the instantaneous fH of seven chick embryos continuously from the last stage of prenatal development (day 18), throughout the pipping (perinatal) period (days 19–21) until hatching and, subsequently, of newly hatched chicks (up to day 2).

The distinctive patterns of instantaneous fH fluctuations took the form of specific changes within a broad mean fH baseline. Cyclic oscillations (ultradian rhythm) occurred until an early stage of the perinatal period, when the fH baseline started rising. Subsequently, the baseline dropped and respiratory arrhythmia began to appear concomitant with external pipping. During the final stage of external pipping, when the fH baseline rose again prior to hatching, three unique patterns of instantaneous fH fluctuations were evident: relatively long-lasting cyclic small accelerations, irregular intermittent large accelerations and short-term repeated large accelerations. Furthermore, repeated alternate occurrences of the latter two types of acceleration formed an additional oscillating pattern with a period of 10–15 min.

During the early period after hatching, when the fH baseline reached its maximum, instantaneous fH changed relatively slowly accompanied by transient rapid decelerations, probably due to augmented vagal tone. Subsequently, the mean fH baseline dropped to its minimum, and a circadian rhythm and three types of previously reported fH fluctuations (types I–III) appeared.

Developmental patterns of mean fH and the appearance of distinctive patterns of instantaneous fluctuations in fH and circadian rhythms were not influenced by an ultimate failure of hatching after a normal development.

The demonstration of complex, repeatable patterns of fH fluctuation that change during development suggests that the avian embryo model should be useful in studying the phenomenon of fH fluctuation and its underlying causes.
Mitochondrial Function in Flying Honeybees (Apis Mellifera): Respiratory Chain Enzymes and Electron Flow from Complex III to Oxygen
Authors: Suarez R. K. , Staples J. F. , Lighton J. R. B. , Mathieu-Costello O.
Published: April 2021

The biochemical bases for the high mass-specific metabolic rates of flying insects remain poorly understood. To gain insights into mitochondrial function during flight, metabolic rates of individual flying honeybees were measured using respirometry, and their thoracic muscles were fixed for electron microscopy. Mitochondrial volume densities and cristae surface densities, combined with biochemical data concerning cytochrome content per unit mass, were used to estimate respiratory chain enzyme densities per unit cristae surface area. Despite the high content of respiratory enzymes per unit muscle mass, these are accommodated by abundant mitochondria and high cristae surface densities such that enzyme densities per unit cristae surface area are similar to those found in mammalian muscle and liver. These results support the idea that a unit area of mitochondrial inner membrane constitutes an invariant structural unit. Rates of O2 consumption per unit cristae surface area are much higher than those estimated in mammals as a consequence of higher enzyme turnover rates (electron transfer rates per enzyme molecule) during flight. Cytochrome c oxidase, in particular, operates close to its maximum catalytic capacity (kcat). Thus, high flux rates are achieved via (i) high respiratory enzyme content per unit muscle mass and (ii) the operation of these enzymes at high fractional velocities.
Sustained Swimming at Low Velocity Following a Bout of Exhaustive Exercise Enhances Metabolic Recovery in Rainbow Trout
Authors: Milligan C. Louise , Hooke G. Brian , Johnson Crystal
Published: April 2021

Sustained swimming at 0.9 BL s−1, where BL is fork body length, following a bout of exhaustive exercise enhanced recovery of metabolite and acid–base status in rainbow trout compared with fish held in still water. The most striking effect of an active recovery was a total absence of the elevation cortisol concentration typically associated with exhaustive exercise. In fish swimming at 0.9 BL s−1, plasma cortisol levels averaged 20–25 ng ml−1 throughout the 6 h recovery period. In contrast, plasma cortisol increased to a peak level of 128.4±11.2 ng ml−1 (mean ± S.E.M., N=6) in fish recovering in still water. Muscle glycogen was completely resynthesized and lactate cleared within 2 h of exercise in swimming fish compared with more than 6 h required in the fish held in still water. Similarly, blood lactate level and acid–base status were restored more quickly in the swimming fish. These observations suggest that the prolonged recovery usually associated with exhaustive exercise in rainbow trout is due to elevations in plasma cortisol concentration and that the stimulus for cortisol release is not exercise per se, but rather post-exercise inactivity.
Oxygen-Dependent Energetics of Anoxia-Tolerant and Anoxia-Intolerant Hepatocytes
Authors: Krumschnabel Gerhard , Schwarzbaum Pablo J. , Lisch Johannes , Biasi Christina , Wieser Wolfgang
Published: April 2021

The oxygen-dependence of cellular energetics was investigated in hepatocytes from goldfish Carassius auratus (anoxia-tolerant) and rainbow trout Oncorhynchus mykiss (anoxia-intolerant). In goldfish hepatocytes, an approximately 50 % reduction in the rate of oxygen consumption was observed in response to both acute and prolonged hypoxia, the latter treatment shifting the threshold for this reduction to a higher oxygen level. A concomitant increase in the rate of lactate production did not compensate for the decreased aerobic ATP supply, resulting in an overall metabolic depression of 26 % during acute hypoxia and of 42 % during prolonged hypoxia. Trout hepatocytes showed a similar suppression of cellular respiration after prolonged hypoxia but were unresponsive to acute hypoxia. Similarly, the rate of lactate production was unaltered during acute hypoxia but was increased during prolonged hypoxia, metabolic depression amounting to 7 % during acute hypoxia and 30 % during prolonged hypoxia. In both species, the affinity of hepatocytes for oxygen decreased during hypoxia, but this alteration was not sufficient in absolute terms to account for the observed decrease in aerobic ATP supply. Protein synthesis was suppressed in both cell types under hypoxia, whereas Na+/K+-ATPase activity decreased in trout but not in goldfish hepatocytes, emphasising the importance of membrane function in these cells during conditions of limited energy supply.
The Ontogeny of Metabolic Rate and Thermoregulatory Capabilities of Northern Fur Seal, Callorhinus Ursinus, Pups in Air and Water
Authors: Donohue M. J. , Costa D. P. , Goebel M. E. , Baker J. D.
Published: April 2021

Young pinnipeds, born on land, must eventually enter the water to feed independently. The aim of this study was to examine developmental factors that might influence this transition. The ontogeny of metabolic rate and thermoregulation in northern fur seal, Callorhinus ursinus, pups was investigated at two developmental stages in air and water using open-circuit respirometry. Mean in-air resting metabolic rate (RMR) increased significantly from 113±5 ml O2 min−1 (N=18) pre-molt to 160±4 ml O2 min−1 (N=16; means ± S.E.M.) post-molt. In-water, whole-body metabolic rates did not differ pre- and post-molt and were 2.6 and 1.6 times in-air RMRs respectively. Mass-specific metabolic rates of pre-molt pups in water were 2.8 times in-air rates. Mean mass-specific metabolic rates of post-molt pups at 20 °C in water and air did not differ (16.1±1.7 ml O2 min−1 kg−1; N=10). In-air mass-specific metabolic rates of post-molt pups were significantly lower than in-water rates at 5 °C (18.2±1.1 ml O2 min−1 kg−1; N=10) and 10 °C (19.4±1.7 ml O2 min−1 kg−1; N=10; means ± S.E.M.). Northern fur seal pups have metabolic rates comparable with those of terrestrial mammalian young of similar body size. Thermal conductance was independent of air temperature, but increased with water temperature. In-water thermal conductance of pre-molt pups was approximately twice that of post-molt pups. In-water pre-molt pups matched the energy expenditure of larger post-molt pups while still failing to maintain body temperature. Pre-molt pups experience greater relative costs when entering the water regardless of temperature than do larger post-molt pups. This study demonstrates that the development of thermoregulatory capabilities plays a significant role in determining when northern fur seal pups enter the water.