bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neuronal Mechanisms Underlying The Facilitatory Control Of Uropod Steering Behaviour During Treadmill Walking In Crayfish:I. Antagonistically Regulated Background Excitability Of Uropod Motoneurones
Authors: Murayama Maki , Takahata Masakazu 
Published: April 2021

ABSTRACT
One of the postural reflexes of crayfish, the uropod steering response, is elicited by specific sensory inputs while the animal is walking. It is not elicited, however, by the same inputs when the animal is at rest. To clarify the neuronal mechanisms underlying this facilitatory control of body posture in the active animals, we used intracellular recordings to analyse the synaptic activities of uropod motor system neurones in an unanaesthetized whole-animal preparation. Several uropod motoneurones were found to receive sustained depolarizing inputs during walking, whereas the walking leg motoneurones sampled always showed rhythmic activity. The membrane conductance of the uropod motoneurones increased during the sustained synaptic activity. Premotor nonspiking interneurones showed depolarizing or hyperpolarizing membrane potential changes during walking that were also accompanied by increases in membrane conductance. Some of these interneurones enhanced uropod motoneurone activity, whereas others suppressed it during walking. These results suggest that the background excitability of uropod motoneurones is kept at an intermediate level during walking by the antagonistic inputs from premotor nonspiking interneurones so that the uropod motor system can be responsive to both further excitatory and inhibitory inputs resulting from postural changes.
Conservation and Variation in the Feeding Mechanism of the Spiny Dogfish Squalus Acanthias
Authors: Wilga Cheryl D. , Motta Philip J. 
Published: April 2021

ABSTRACT
Changes in the feeding mechanism with feeding behavior were investigated using high-speed video and electromyography to examine the kinematics and motor pattern of prey capture, manipulation and transport in the spiny dogfish Squalus acanthias (Squalidae: Squaliformes). In this study, Squalus acanthias used both suction and ram behaviors to capture and manipulate prey, while only suction was used to transport prey. The basic kinematic feeding sequence observed in other aquatic-feeding lower vertebrates is conserved in the spiny dogfish. Prey capture, bite manipulation and suction transport events are characterized by a common pattern of head movements and motor activity, but are distinguishable by differences in duration and relative timing. In general, capture events are longer in duration than manipulation and transport events, as found in other aquatic-feeding lower vertebrates. Numerous individual effects were found, indicating that individual sharks are capable of varying head movements and motor activity among successful feeding events. Upper jaw protrusion in the spiny dogfish is not restricted by its orbitostylic jaw suspension; rather, the upper jaw is protruded by 30 % of its head length, considerably more than in the lemon shark Negaprion brevirostris (Carcharhinidae: Carcharhiniformes) (18 %) with its hyostylic jaw suspension. One function of upper jaw protrusion is to assist in jaw closure by protruding the upper jaw as well as elevating the lower jaw to close the gape, thus decreasing the time to jaw closure. The mechanism of upper jaw protrusion was found to differ between squaliform and carcharhiniform sharks. Whereas the levator palatoquadrati muscle assists in retracting the upper jaw in the spiny dogfish, it assists in protruding the upper jaw in the lemon shark. This study represents the first comprehensive electromyographic and kinematic analysis of the feeding mechanism in a squaliform shark.
A Note on Interactions Between Temperature, Viscosity, Body Size and Swimming Energetics in Fish Larvae
Authors: Wieser Wolfgang , Kaufmann Rüdiger 
Published: April 2021

ABSTRACT
In a previous study, it was shown that at a given speed the larvae of a species of freshwater fish, the Danube bleak Chalcalburnus chalcoides, expended considerably more metabolic energy at 15 °C than at 20 °C. We applied hydromechanical arguments to our previous data in order to determine whether the higher cost of swimming at the lower temperature might be due to the effects of viscous forces. However, even under the unrealistic assumption of the larvae swimming in the viscous regime at Reynolds numbers as high as 2000, we show here that hydromechanical forces cannot explain the high energy cost of swimming at 15 °C. Instead, we offer a new hypothesis that the ‘two-gear system’ of the swimming muscles operating in juvenile and adult fish is not yet functional in the larvae, with the consequence that, when these fish are swimming at high speeds in cold water, the muscle fibres have to operate over an increasingly inefficient range of shortening velocities.
Cardio-Respiratory Ontogeny During Chronic Carbon Monoxide Exposure in the Clawed Frog Xenopus Laevis
Authors: Territo Paul R. , Burggren Warren W. 
Published: April 2021

ABSTRACT
The present study investigates the ontogeny of cardio-respiratory physiology in Xenopus laevis where O2 transport is obstructed. Animals were raised from eggs (NF stage 1) to metamorphic climax (NF stage 63), while maintained either in air or in chronic 2 kPa CO, which functionally ablates O2 transport by hemog.lobin (Hb). Whole-animal rate of oxygen consumption , whole-body lactate concentration, individual mass, heart rate (fH) and stroke volum. e (VS) were measured. Additionally, cardiac output (Q̇) and the ratio of the rate of oxygen consumption to the total rate at which oxygen is transported in the blood were calculated to determine limitations imparted when O2 transport is impaired.
Our data on early development suggest that the onset of convective blood flow occurs prior to the absolute need for convection to supplement diffusive transport. Values for , whole-body lactate concentration, mass and fHdid not differ significantly between controls and CO-exposed animals. However, CO-exposed animals showed a. significant (P&lt;0.05) increase in VS, and Q̇ compared with controls. These results indicate that limiting blood O2 transport is not deleterious to metabolism and development as a whole and that convective oxygen transport via Hb is not essential for normal cardiovascular or respiratory function during larval development.
Proprioceptive Contribution to Distance Estimation by Motion Parallax in a Praying Mantid
Authors: Poteser Michael , Pabst Maria Anna , Kral Karl 
Published: April 2021

ABSTRACT
The behavioural experiments described here examined, in the praying mantis Tenodera sinensis, the manner in which the proprioceptive cervical hair plate sensilla are involved in the measurement of the distance to a jump target with the aid of motion parallax actively produced by translatory head motion. Various combinations of surgical deafferentation of the cervical hair plate sensilla had no influence on the linearisation of head motion. However, the measurement of relative and absolute distance and the jump frequency were impaired by these interventions. From the results, it is concluded that the cervical hair plate sensilla are involved in the distance measurement mechanism, probably by allowing the nervous system to compare retinal image motion with head motion.
Systematic biology of gymnotiform and mormyriform electric fishes: phylogenetic relationships, molecular clocks and rates of evolution in the mitochondrial rRNA genes
Authors: Alves-Gomes José A. 
Published: April 2021

ABSTRACT
The phylogenetic relationships of both African and South American electric fish orders are reviewed at their intra-ordinal level taking into consideration recent studies in which cladistic principles have been employed. Several concordant topologies emerge from the different data sets, but some unsettled issues still remain. From the studies available, a consensus topology has been suggested for the Mormyriformes and for the Gymnotiformes. Subsequently, the evolutionary relationships of these two electric fish clades are considered within each respective superorder, i.e. in relation to the other osteoglossomorph and ostariophysan orders. The inter-ordinal phylogenies are used as a framework to test the molecular clock hypothesis with two gene fragments of the mitochondrial genome. Gymnotiformes, Siluriformes and Characiformes are accumulating mutations at the same pace in relation to their respective outgroups, but for all the other combinations of sister clades tested the molecular clock can be statistically rejected. Fossil records are then surveyed and used to calibrate absolute rates of genetic differentiation for each main lineage (orders) of both osteoglossomorphs and ostariophysans. The most conserved regions (stems) of the 12S and 16S gene fragments used are evolving at an average rate of 0.123 % 106 years− 1 for the osteoglossomorphs and 0.137 % 106 years− 1 for the ostariophysans, with no significant difference between these two values. The rate of mutation in the loops, the faster-evolving segments, estimated for closely related electric fish taxa is 0.82 % 106 years− 1 for four Brienomyrus species and 1.01 % 106 years− 1 for the four eigenmanniid genera. When the entire molecule (loops + stems) is considered, the rate of mutation in both mormyriforms and gymnotiforms converges to a rounded value of 0.23 % 106 years− 1.
Oscillatory and burst discharge in the apteronotid electrosensory lateral line lobe
Authors: Turner Ray W. , Maler Leonard 
Published: April 2021

ABSTRACT
Oscillatory and burst discharge is recognized as a key element of signal processing from the level of receptor to cortical output cells in most sensory systems. The relevance of this activity for electrosensory processing has become increasingly apparent for cells in the electrosensory lateral line lobe (ELL) of gymnotiform weakly electric fish. Burst discharge by ELL pyramidal cells can be recorded in vivo and has been directly associated with feature extraction of electrosensory input. In vivo recordings have also shown that pyramidal cells are differentially tuned to the frequency of amplitude modulations across three ELL topographic maps of electroreceptor distribution. Pyramidal cell recordings in vitro reveal two forms of oscillatory discharge with properties consistent with pyramidal cell frequency tuning in vivo. One is a slow oscillation of spike discharge arising from local circuit interactions that exhibits marked changes in several properties across the sensory maps. The second is a fast, intrinsic form of burst discharge that incorporates a newly recognized interaction between somatic and dendritic membranes. These findings suggest that a differential regulation of oscillatory discharge properties across sensory maps may underlie frequency tuning in the ELL and influence feature extraction in vivo.
Physiology of electrosensory lateral line lobe neurons in Gnathonemus petersii
Authors: Sugawara Yoshiko , Grant Kirsty , Han Victor , Bell Curtis C. 
Published: April 2021

ABSTRACT
In mormyrid electric fish, sensory signals from electroreceptors are relayed to secondary sensory neurons in a cerebellum-like structure known as the electrosensory lateral line lobe (ELL). Efferent neurons and interneurons of the ELL also receive inputs of central origin, including electric organ corollary discharge signals, via parallel fibers and via fibers from the juxtalobar nucleus. To understand the cellular mechanisms of the integration of sensory inputs and central inputs in the ELL, the intracellular activity and ionic properties of the efferent projection neurons and interneurons were examined in an in vitro slice preparation.
We focus here on the electrophysiological properties of the efferent neurons of the ELL network, the large fusiform cells and large ganglion cells, and on a class of γ-aminobutyric acid (GABA)-ergic interneurons known as medium ganglion (MG) cells. In response to current injection through a recording pipette, both types of efferent neuron fire a large narrow spike followed by a large hyperpolarizing afterpotential. The MG cells fire a complex spike which consists of small narrow spikes and a large broad spike. Although the forms of the action potentials in efferent neurons and in MG cells are different, all spikes are mediated by tetrodotoxin (TTX)-sensitive Na+ conductances and spike repolarization is mediated by tetraethylammonium (TEA+)-sensitive K+ conductances. In the presence of TEA+, substitution of Ba2+ for Ca2+ in the bath revealed the presence of a high-voltage-activated Ca2+ conductance.
Stimulation of parallel fibers conveying descending input to the ELL molecular layer in vitro evokes an excitatory postsynaptic potential (EPSP), generally followed by an inhibitory postsynaptic potential (IPSP), in the efferent neurons. In MG cells, the same stimulation evokes an EPSP, often followed by a small IPSP. Synaptic transmission at parallel fiber synapses is glutamatergic and is mediated via both N-methyl-D-aspartate (NMDA)- and (AMPA)-type glutamate receptors. The inhibitory component of the parallel fiber response is GABAergic. It is probably mediated via the stellate neurons and the MG cells, which are themselves GABAergic interneurons intrinsic to the ELL network.
A hypothetical neural circuit of the intrinsic connections of the ELL, based on the known morphology of projection neurons and medium ganglion interneurons, is presented. This circuit includes an excitatory and an inhibitory submodule. The excitatory submodule is centered on a large fusiform cell and appears to relay the sensory input as a positive ‘ON’ image of an object. The inhibitory submodule is centered on a large ganglion cell and relays a negative ‘OFF’ image to the next higher level. We suggest that MG cells exert an inhibitory bias on efferent neuron types and that the ELL network output is modulated by the dynamically plastic integration of central descending signals with sensory input.
Central mechanisms of temporal analysis in the knollenorgan pathway of mormyrid electric fish
Authors: Xu-Friedman Matthew A. , Hopkins Carl D. 
Published: April 2021

ABSTRACT
Mormyrid electric fish communicate using pulse-type electric organ discharges (EODs). The fine temporal structure of the waveforms of EODs varies widely throughout the 200 or more species of mormyrids. These signals carry information about the species, the sex and even the individual identity of the signaller. Behavioral experiments have shown that some species of fish are capable of using this information. Of the four known types of electroreceptors in mormyrid fish, the knollenorgan electroreceptor is the one most likely to be involved in the detection of conspecific EOD signals. Here, we review some recent advances in understanding how the central knollenorgan pathway might be analyzing the temporal structure of the EOD waveform. Fine temporal analysis appears to take place in the nucleus exterolateralis pars anterior (ELa), where tightly phase-locked inputs from the hindbrain drive a direct, excitatory input through a long axonal delay line and also drive an indirect, inhibitory input with negligible delay through the ELa large cell. These two inputs converge on ELa small cells, where they are hypothesized to interact in a ‘delay-line/blanking’ model. This initial temporal analysis is further refined in the nucleus exterolateralis pars posterior, where units tuned to ranges of pulse durations have been identified physiologically.
Electroreception in monotremes
Authors: Pettigrew John D. 
Published: April 2021

ABSTRACT
I will briefly review the history of the bill sense of the platypus, a sophisticated combination of electroreception and mechanoreception that coordinates information about aquatic prey provided from the bill skin mechanoreceptors and electroreceptors, and provide an evolutionary account of electroreception in the three extant species of monotreme (and what can be inferred of their ancestors). Electroreception in monotremes is compared and contrasted with the extensive body of work on electric fish, and an account of the central processing of mechanoreceptive and electroreceptive input in the somatosensory neocortex of the platypus, where sophisticated calculations seem to enable a complete three-dimensional fix on prey, is given.
Branching out in locomotion: the mechanics of perch use in birds and primates
Authors: Bonser Richard H. C. 
Published: April 2021

ABSTRACT
Many animals use thin perches, such as the branches of trees, as locomotory substrates. In this paper, I have reviewed the literature concerned with measurements of locomotory forces made by birds and primates on thin and flexible substrates. Through a knowledge of the locomotory forces exerted by animals when using different substrates, the mechanical cost of their use can be established. We are just beginning to learn about the magnitude and patterns of force production in various branch-using vertebrates, primarily as a result of the development of instrumented perches. Instrumented perches have been designed to measure the forces produced by birds and primates when leaping from rigid and flexible horizontal and flexible vertical perches, and also from instrumented handgrips during brachiation. The development of these techniques for birds and primates allows us to compare the way in which they use perches as locomotory substrates.
In both birds and primates, the magnitudes of landing forces are smaller than those during take-off. Two explanations have been proposed; the difference is either a consequence of perch compliance or it is a strategic decision to be cautious of ‘new’ perches. Leaps from flexible perches may be somewhat inefficient because considerable energy is dissipated in bending the perch, and this energy may remain unrecovered when the animal leaves contact with the perch.
Locomotor mechanics during early life history: effects of size and ontogeny on fast-start performance of salmonid fishes
Authors: Hale Melina E. 
Published: April 2021

ABSTRACT
Fast-start locomotor behavior is important for escaping from predators and for capturing prey. To examine the effects of size and other aspects of developmental morphology on fast-start performance, the kinematics of the fast-start escape behavior were studied through early post-hatching development in three salmonid species: chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch) and brown trout (Salmo trutta). These three species, while morphologically and developmentally similar, hatch and mature at different sizes (total length). Comparison of these species shows that some fast-start performance variables, including stage duration, maximum velocity and maximum acceleration, are highly dependent on ontogenetic state, while another, the overall distance traveled during stage 2, scales with total body length. Brown trout were studied from hatching into the juvenile development period. Aspects of fast-start performance peak at the end of yolk-sac absorption (the end of the eleutheroembryo phase) when the fish reaches the juvenile period. At this time, the durations of the fast-start stages are at their minima, and maximum velocity and maximum acceleration are at their highest levels relative to body length. Thus, escape behavior reaches its maximum size-specific performance at a relatively small size, just as the fish absorbs its yolk sac and begins to search for food. This peak in fast-start performance occurs during a life history period in which fast-start ability is likely to be particularly important for survival.
Mechanics of ventilation in swellsharks, Cephaloscyllium ventriosum (Scyliorhinidae)
Authors: Ferry-Graham Lara A. 
Published: April 2021

ABSTRACT
A simple two-pump model has served to describe the mechanics of ventilation in cartilaginous and bony fishes since the pioneering work of G. M. Hughes. A hallmark of this model is that water flow over the gills is continuous. Studies of feeding kinematics in the swellshark Cephaloscyllium ventriosum, however, suggested that a flow reversal occurred during prey capture and transport. Given that feeding is often considered to be simply an exaggeration of the kinematic events performed during respiration, I investigated whether flow reversals are potentially present during respiration. Pressure and impedance data were coupled with kinematic data from high-speed video footage and dye studies and used to infer patterns of water flow through the heads of respiring swellsharks. Swellsharks were implanted with pressure transducers to determine the pattern and magnitude of pressures generated within the buccal and parabranchial (gill) cavities during respiration. Pressure traces revealed extended periods of pressure reversal during the respiratory cycle. Further, impedance data suggested that pressures within the buccal and parabranchial cavities were not generated by the cyclic opening and closing of the jaws and gills in the manner previously suggested by Hughes. Thus, the classic model needs to be re-evaluated to determine its general applicability. Two alternative models for pressure patterns and their mechanism of generation during respiration are provided. The first depicts a double-reversal scenario common in the swellshark whereby pressures are reversed following both of the pump stages (the suction pump and the pressure pump) rather than after the pressure-pump stage only. The second model describes a scenario in which the suction pump is insufficient for generating a positive pressure differential across the gills; thus, a pressure reversal persists throughout this phase of respiration. Kinematic analysis based on high-speed video footage and dye studies, however, suggested that during respiration, as opposed to feeding, distinct flow reversals do not result from the pressure reversals. Thus, water is probably pooling around the gill filaments during the long periods of pressure reversal.
Mechanisms of thermal stability during flight in the honeybee Apis mellifera
Authors: Roberts Stephen P. , Harrison Jon F. 
Published: April 2021

ABSTRACT
Thermoregulation of the thorax allows honeybees (Apis mellifera) to maintain the flight muscle temperatures necessary to meet the power requirements for flight and to remain active outside the hive across a wide range of air temperatures (Ta). To determine the heat-exchange pathways through which flying honeybees achieve thermal stability, we measured body temperatures and rates of carbon dioxide production and water vapor loss between Ta values of 21 and 45 °C for honeybees flying in a respirometry chamber. Body temperatures were not significantly affected by continuous flight duration in the respirometer, indicating that flying bees were at thermal equilibrium. Thorax temperatures (Tth) during flight were relatively stable, with a slope of Tth on Ta of 0.39. Metabolic heat production, calculated from rates of carbon dioxide production, decreased linearly by 43 % as Ta rose from 21 to 45 °C. Evaporative heat loss increased nonlinearly by over sevenfold, with evaporation rising rapidly at Ta values above 33 °C. At Ta values above 43 °C, head temperature dropped below Ta by approximately 1–2 °C, indicating that substantial evaporation from the head was occurring at very high Ta values. The water flux of flying honeybees was positive at Ta values below 31 °C, but increasingly negative at higher Ta values. At all Ta values, flying honeybees experienced a net radiative heat loss. Since the honeybees were in thermal equilibrium, convective heat loss was calculated as the amount of heat necessary to balance metabolic heat gain against evaporative and radiative heat loss. Convective heat loss decreased strongly as Ta rose because of the decrease in the elevation of body temperature above Ta rather than the variation in the convection coefficient. In conclusion, variation in metabolic heat production is the dominant mechanism of maintaining thermal stability during flight between Ta values of 21 and 33 °C, but variations in metabolic heat production and evaporative heat loss are equally important to the prevention of overheating during flight at Ta values between 33 and 45 °C.