bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signals and noise in the elasmobranch electrosensory system
Authors: Montgomery J. C. , Bodznick D. 
Published: April 2021

ABSTRACT
Analyzing signal and noise for any sensory system requires an appreciation of the biological and physical milieu of the animal. Behavioral studies show that elasmobranchs use their electrosensory systems extensively for prey detection, but also for mate recognition and possibly for navigation. These biologically important signals are detected against a background of self-generated bioelectric fields. Noise-suppression mechanisms can be recognized at a number of different levels: behavior, receptor anatomy and physiology, and at the early stages of sensory processing. The peripheral filters and receptor characteristics provide a detector with permissive temporal properties but restrictive spatial characteristics. Biologically important signals probably cover the range from direct current to 10 Hz, whereas the bandwidth of the receptors is more like 0.1–10 Hz. This degree of alternating current coupling overcomes significant noise problems while still allowing the animal to detect external direct current signals by its own movement. Self-generated bioelectric fields modulated by breathing movement have similar temporal characteristics to important external signals and produce very strong modulation of electrosensory afferents. This sensory reafference is essentially similar, or common-mode, across all afferent fibers. The principal electrosensory neurons (ascending efferent neurons; AENs) of the dorsal octavolateralis nucleus show a greatly reduced response to common-mode signals. This suppression is mediated by the balanced excitatory and inhibitory components of their spatial receptive fields. The receptive field characteristics of AENs determine the information extracted from external stimuli for further central processing.
Neural circuitry for communication and jamming avoidance in gymnotiform electric fish
Authors: Metzner Walter 
Published: April 2021

ABSTRACT
Over the past decade, research on the neural basis of communication and jamming avoidance in gymnotiform electric fish has concentrated on comparative studies of the premotor control of these behaviors, on the sensory processing of communication signals and on their control through the endocrine system, and tackled the question of the degree to which these behaviors share neural elements in the sensory–motor command chain by which they are controlled. From this wealth of investigations, we learned, first, how several segregated premotor pathways controlling a single central pattern generator, the medullary pacemaker nucleus, can provide a large repertoire of behaviorally relevant motor patterns. The results suggest that even small evolutionary modifications in the premotor circuitry can yield extensive changes in the behavioral output. Second, we have gained some insight into the concerted action of the brainstem, the diencephalon and the long-neglected forebrain in sensory processing and premotor control of communication behavior. Finally, these studies shed some light on the behavioral significance of multiple sensory brain maps in the electrosensory lateral line lobe that long have been a mystery. From these latter findings, it is tempting to interpret the information processing in the electrosensory system as a first step in the evolution towards the ‘distributed hierarchical’ organization commonly realized in sensory systems of higher vertebrates.
Resolving competing theories for control of the jamming avoidance response: the role of amplitude modulations in electric organ discharge decelerations
Authors: Takizawa Yumi , Rose Gary J. , Kawasaki Masashi 
Published: April 2021

ABSTRACT
The algorithm for the control of the jamming avoidance response (JAR) of Eigenmannia has been the subject of debate for over two decades. Two competing theories have been proposed to explain how fish determine the correct direction to shift their pacemaker frequency during jamming. One theory emphasizes the role of time-asymmetric beat envelopes, while the other emphasizes the role of amplitude- and phase-difference computations that arise from the differences in spatial geometry of the electric fields of neighboring fish. In repeating earlier experiments, we found that the decision to raise or lower the pacemaker frequency reliably above or below its resting level depends on the latter process, and that frequency deceleration responses to amplitude modulation appear to be sufficient to explain previous experimental results on which the former theory is based. Specifically, fish of the genus Eigenmannia show differential deceleration responses to asymmetric beat envelopes. The deceleration responses do not require phase modulation and show a sensitivity for amplitude modulation depth and selectivity for amplitude modulation rate comparable with that of JARs that are elicited when amplitude- and phase-difference information is available.
Neural command of electromotor output in mormyrids
Authors: Grant Kirsty , Emde Gerhard Von Der , Sena Leonel Gomez , Mohr Claudia 
Published: April 2021

ABSTRACT
The electric discharge of mormyrid fish has an irregular pattern controlled by the electromotor command nucleus in the medulla. Anatomical studies suggest that much of the descending information integrated by the command nucleus comes from the diencephalic precommand nucleus. But field potentials related to the motor command occur later in the precommand nucleus than in the command nucleus, suggesting that they are a corollary rather than a cause of electromotor command initiation. Recorded extracellularly, certain precommand nucleus units fire spontaneously between electromotor commands but pause briefly following each command; others units fire a burst of spikes only during the post-command pause. The firing frequency of the former is correlated with the duration of the interval between successive electromotor commands when the fish is discharging at more than approximately 5 Hz. The post-command pause in spontaneous firing is due to corollary-discharge-mediated feedback inhibition, probably generated by the activity of the bursting units that fire only during this period. Precommand nucleus neurons are activated by electrosensory input, and stimulation of the precommand nucleus modulates the endogenous pattern of electromotor command. We propose that the irregular rhythm of the motor command depends largely on the integration of descending information of various origins, conveyed via the precommand nucleus to the command nucleus, and that this process is regulated by corollary discharge feedback inhibition to the precommand nucleus.
Communication signals and sound production mechanisms of mormyrid electric fish
Authors: Crawford John D. , Huang Xiaofeng 
Published: April 2021

ABSTRACT
The African weakly electric fishes Pollimyrus isidori and Pollimyrus adspersus (Mormyridae) produce elaborate acoustic displays during social communication in addition to their electric organ discharges (EODs). In this paper, we provide new data on the EODs of these sound-producing mormyrids and on the mechanisms they use to generate species-typical sounds.
Although it is known that the EODs are usually species-specific and sexually dimorphic, the EODs of closely related sound-producing mormyrids have not previously been compared. The data presented demonstrate that there is a clear sexual dimorphism in the EOD waveform of P. isidori. Females have a multi-phasic EOD that is more complex than the male’s biphasic EOD. In this respect, P. isidori is similar to its more thoroughly studied congener P. adspersus, which has a sexually dimorphic EOD. The new data also reveal that the EODs of these two species are distinct, thus showing for the first time that species-specificity in EODs is characteristic of these fishes, which also generate species-specific courtship sounds.
The sound-generating mechanism is based on a drumming muscle coupled to the swimbladder. Transverse sections through decalcified male and female P. adspersus revealed a muscle that envelops the caudal pole of the swimbladder and that is composed of dorso-ventrally oriented fibers. The muscle is five times larger in males (14.5±4.4 μl, mean ± S.D.) than in females (3.2±1.8 μl). The fibers are also of significantly larger diameter in males than in females. Males generate courtship sounds and females do not.
The function of the swimbladder muscle was tested using behavioral experiments. Male P. adspersus normally produce acoustic courtship displays when presented with female-like electrical stimuli. However, local anesthesia of the swimbladder muscle muted males. In control trials, males continued to produce sounds after injection of either lidocaine in the trunk muscles or saline in the swimbladder muscles.
Blowfly flight and optic flow : I. Thorax kinematics and flight dynamics
Authors: Schilstra C. , Van Hateren J. H. 
Published: April 2021

ABSTRACT
The motion of the thorax of the blowfly Calliphora vicina was measured during cruising flight inside a cage measuring 40 cm×40 cm×40 cm. Sensor coils mounted on the thorax picked up externally generated magnetic fields and yielded measurements of the position and orientation of the thorax with a resolution of 1 ms, 0.3 ° and 1 mm. Flight velocities inside the cage were up to 1.2 m s−1, and accelerations were up to 1 g (≈10m s−2) vertically and 2 g horizontally. During flight, blowflies performed a series of short (approximately 20–30 ms) saccade-like turns at a rate of approximately 10 s−1. The saccades consisted of a succession of rotations around all axes, occurring in a fixed order. First, a roll was started. Second, the rolled thorax pitched (pulling the nose up) and yawed, resulting in a turn relative to the outside world. Finally, the thorax rolled back to a level position. Saccades had yaw amplitudes of up to 90 °, but 90 % were smaller than 50 °. Maximum angular velocities were 2000 ° s−1, and maximum accelerations were 105 ° s−2. The latter correspond to torques consistent with the maximal force (2×10−3 N) that can be generated by the flight motor as inferred from the maximal linear acceleration. Furthermore, the sequence of energy investment in consecutive rotations around different axes appears to be optimized during a saccade.
Blowfly flight and optic flow: II. Head movements during flight
Authors: Hateren J. H. Van , Schilstra C. 
Published: April 2021

ABSTRACT
The position and orientation of the thorax and head of flying blowflies (Calliphora vicina) were measured using small sensor coils mounted on the thorax and head. During flight, roll movements of the thorax are compensated by counter rolls of the head relative to the thorax. The yaw turns of the thorax (thorax saccades) are accompanied by faster saccades of the head, starting later and finishing earlier than the thorax saccades. Blowfly flight can be divided into two sets of episodes: ‘during saccades’, when high angular velocities of up to a few thousand degrees per second are reached by both the thorax and head, and ‘between saccades’, when the orientation of the thorax and, in particular, the head is well stabilized. Between saccades, the angular velocities of the head are approximately half those of the thorax and lie mostly in the range 0–100 ° s−1 for any rotation (yaw, pitch and roll). These velocities are low enough to limit the visual blur attributable to rotation. It is argued that the split into periods during which either rotational optic flow (‘during saccades’) or translatory optic flow (‘between saccades’) dominates is helpful for processing optic flow when signals and neurons are noisy.
Time course of salinity adaptation in a strongly euryhaline estuarine teleost, Fundulus heteroclitus: a multivariable approach
Authors: Marshall W. S. , Emberley T. R. , Singer T. D. , Bryson S. E. , McCormick S. D. 
Published: April 2021

ABSTRACT
Freshwater-adapted killifish (Fundulus heteroclitus) were transferred directly from soft fresh water to full-strength sea water for periods of 1 h, 3 h, 8 h and 1, 2, 7, 14 and 30 days. Controls were transferred to fresh water for 24 h. Measured variables included: blood [Na+], osmolality, glucose and cortisol levels, basal and stimulated rates of ion transport and permeability of in vitro opercular epithelium, gill Na+/K+-ATPase and citrate synthase activity and chloride cell ultrastructure. These data were compared with previously published killifish cystic fibrosis transmembrane conductance regulator (kfCFTR) expression in the gills measured over a similar time course. Plasma cortisol levels peaked at 1 h, coincident with a rise in plasma [Na+]. At 8 h after transfer to sea water, a time at which previous work has shown kfCFTR expression to be elevated, blood osmolality and [Na+] were high, and cortisol levels and opercular membrane short-circuit current (Isc; a measure of Cl− secretion rate) were low. The 24 h group, which showed the highest level of kfCFTR expression, had the highest plasma [Na+] and osmolality, elevated plasma cortisol levels, significantly lower opercular membrane resistance, an increased opercular membrane ion secretion rate and collapsed tubule inclusions in mitochondria-rich cells, but no change in gill Na+/K+-ATPase and citrate synthase activity or plasma glucose levels. Apparently, killifish have a rapid (&lt;1 h) cortisol response to salinity coupled to subsequent (8–48 h) expression of kfCFTR anion channel proteins in existing mitochondria-rich cells that convert transport from ion uptake to ion secretion.
Developmental patterns of heart rate in altricial avian embryos and hatchlings
Authors: Pearson James T. , Noma Yasuhiro , Tazawa Hiroshi 
Published: April 2021

ABSTRACT
The aims of this study were to determine the patterns of development of heart rate (fH) in altricial avian embryos and hatchlings, and then to examine how fH is regulated to meet metabolic requirements in altricial embryos. Embryonic mean heart rate in 12 altricial species (Passeriformes and Psittaciformes) increased during pre-pipping incubation in all species except the cockatiel (Nymphicus hollandicus), in which tended to decrease prior to pipping. The rate of increase in fH tripled during the pipping phase in all species, and was significantly higher during the pipping period and in hatchlings than during pre-pipping development. The O2 pulse (O2 consumed per cardiac beat) of altricial embryos increased in direct proportion to embryo mass (loge /loge base), although was often low prior to pipping, implying that stroke volume increases in the second half of incubation. We conclude that fH contributes more than other factors towards supplying the metabolic demands of the embryo during the middle of incubation and the final pipping phase, but less during the intervening period of late incubation.
Salivary glands of the sand fly Phlebotomus papatasi contain pharmacologically active amounts of adenosine and 5′-AMP
Authors: Ribeiro José M. C. , Katz Oren , Pannell Lewis K. , Waitumbi John , Warburg Alon 
Published: April 2021

ABSTRACT
Salivary gland homogenates of the sand fly Phlebotomus papatasi contain large amounts of adenosine and 5′-AMP, of the order of 1 nmol per pair of glands, as demonstrated by liquid chromatography, ultraviolet spectrometry, mass spectrometry and bioassays. These purines, 75–80 % of which are secreted from the glands following a blood meal, have vasodilatory and anti-platelet activities and probably help the fly to obtain a blood meal. Salivary 5′-AMP is also responsible for the previously reported protein phosphatase inhibitor in the salivary glands of P. papatasi, which is shown to be artifactual in nature as a result of allosteric modification by AMP of the phosphatase substrate used (phosphorylase a).
Influence of odour plume structure on upwind flight of mosquitoes towards hosts
Authors: Geier Martin , Bosch Oliver Jörg , Boeckh Jürgen 
Published: April 2021

ABSTRACT
Both the concentration and the fine-scale plume structure of host odours influence the upwind flight of female mosquitoes Aedes aegypti (L.) (Diptera: Culicidae) in a wind tunnel. The attractive effects of carbon dioxide, human skin odour and L-(+)-lactic acid were tested in homogeneous, turbulent and filamentous odour plumes. With carbon dioxide, the percentage of upwind-flying mosquitoes increased with the increasing fluctuations in concentration that occur in turbulent and filamentous plumes. In homogeneous plumes, an initial activation effect was observed, but sustained upwind flights were less frequent than in the other plumes. The opposite was found with plumes of human skin odour: the highest number of mosquitoes flew upwind in the homogeneous plume, whereas in turbulent or filamentous plumes their numbers were significantly lower. Regardless of plume type, the percentage of upwind-flying mosquitoes increased with increasing concentrations of carbon dioxide and of skin odour. With L-(+)-lactic acid, the dose–response characteristics were not consistent, and the relative effects of different plume types upon upwind flights differed within different ranges of concentration. Even maximum reactions to this compound were modest compared with those to carbon dioxide or to skin odour. Our findings demonstrate (1) that mosquitoes are able to orient upwind under continuous odour stimulation and (2) that upwind flight is dependent upon plume structure in different ways for different host odour components.
Arterial blood gas levels and cardiovascular function during varying environmental conditions in a mudskipper, Periophthalmodon schlosseri
Authors: Ishimatsu Atsushi , Aguilar Nancy M. , Ogawa Kougi , Hishida Yasuhiro , Takeda Tatsusuke , Oikawa Shin , Kanda Takeshi , Huat Khoo Khay 
Published: April 2021

ABSTRACT
Changes in blood gas levels, blood pressure and heart rate were studied in chronically cannulated mudskippers, Periophthalmodon schlosseri, subjected to air exposure (6 h), aquatic hypoxia with access to air (water &lt;0.9 kPa, 6 h) and forced submersion in normoxic water (12 h) at 30 °C.
Air exposure did not affect either blood O2 and had little effect on blood CO2 levels, but blood pH increased slightly, but significantly. Blood ammonia concentration was elevated sixfold during air exposure. Aquatic hypoxia caused no significant changes in blood gas levels. When the fish was forcibly submerged, blood O2 saturation decreased rapidly to approximately 30 %. Blood and total CO2 also decreased, but blood pH was unaffected by forcible submersion.
Air exposure did not affect blood pressure or heart rate. Aquatic hypoxia did not affect blood pressure but transiently increased heart rate. In contrast, forced submersion significantly depressed heart rate throughout the period of submersion, while blood pressure decreased only transiently. Upon emersion, the heart rate immediately increased to above the control level when the fish took its first air breath.
Key words: mudskipper, Periophthalmodon schlosseri, blood gas, cardiac function, hypoxia, air exposure.
A high-resolution in vitro bioassay to identify neurons containing red pigment concentrating hormone
Authors: Alvarado-Álvarez Ramón , Becerra Elizabeth , García Ubaldo 
Published: April 2021

ABSTRACT
The release of red pigment concentrating hormone (RPCH) by single peptidergic neurons of the crayfish X organ/sinus gland system (XO-SG) was demonstrated using a novel in vitro bioassay in which XO neurons were co-cultured with tegumentary erythrophores. Local retraction of the pigmentary matrix within filipodia from erythrophores plated next to presumptive RPCH-containing neurons suggest spontaneous hormone release. Topical application of synthetic RPCH onto long filipodia also produced a local response. The time course of pigmentary matrix aggregation depended on the dose of synthetic RPCH. The effect of peptide on the cultured target cells was blocked by a polyclonal antiserum against RPCH. In co-culture conditions, the time course of pigmentary matrix aggregation was accelerated when presumptive RPCH-containing neurons were depolarized by intracellular current injection or by voltage-clamping to activate the Ca2+ current. The aggregation response evoked by these maneuvers was similar to that obtained with synthetic RPCH at a concentration of 1 fmol l−1. The immune serum was also used to identify a subset of 3–7 immunoreactive neurons localized in the external rim of the XO close to the medulla interna. Under culture conditions, this subset of neurons corresponded to the cells that induced the erythrophore response.
Echolocation behaviour and prey-capture success in foraging bats: laboratory and field experiments on Myotis daubentonii
Authors: Britton Adam R. C. , Jones Gareth 
Published: April 2021

ABSTRACT
During prey-capture attempts, many echolocating bats emit a ‘terminal buzz’, when pulse repetition rate is increased and pulse duration and interpulse interval are shortened. The buzz is followed by a silent interval (the post-buzz pause). We investigated whether variation in the structure of the terminal buzz, and the calls and silent periods following it, may provide information about whether the capture attempt was successful and about the size of prey detected – detail that is valuable in studies of habitat use and energetics. We studied the trawling bat Myotis daubentonii. The time between the first call of the approach phase and the end of the terminal phase was not related to prey size in the laboratory. The last portion of the terminal buzz (buzz II) was shortened or omitted during aborted capture attempts. Both in the laboratory and in the field, the mean interpulse interval immediately after the terminal buzz (post-buzz interpulse interval) was longer in successful captures than in unsuccessful attempts. In the laboratory, the post-buzz pause was longer after successful captures than for unsuccessful attempts, and the minimum frequency of the first search-phase call emitted after the buzz (Fmin) was higher than that of the last such call prior to the buzz. These effects were not apparent in field data. Both in the laboratory (85 %) and in the field (74 %), significant discrimination between successful and unsuccessful capture attempts was possible when the duration of the post-buzz pause, post-buzz interpulse interval and Fmin were entered into a discriminant analysis. Thus, variation in the echolocation calls of bats during prey-capture attempts can reveal substantial information about capture success and prey size.