bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Hormones, Second Messengers and pH on the Expression of Metabolic Responses to Anoxia in a Marine Whelk
Authors: Brooks Stephen P. J. , Storey Kenneth B.
Published: April 2021

The roles of hormones, second messengers and pH in triggering or potentiating biochemical responses to anaerobiosis were evaluated using in vitro incubations of isolated muscle tissues (foot, radular retractor, ventricle) from the marine whelk Busycon canaliculatum (L.). Incubating tissues in vitro under anoxic conditions stimulated changes in muscle fructose-2,6-bisphosphate levels and pyruvate kinase kinetics (Km values for phosphoenolpyruvate, values for L-alanine) that were virtually equivalent to those that occur in vivo. Additions of hormones (epinephrine, norepinephrine, octopamine, serotonin, glucagon, insulin) or inhibitors of prostaglandin synthesis (dexamethasone, aspirin) had no effect on these metabolic responses to anoxia. The second messenger compounds, dibutyryl cyclic AMP and Ca2+ + ionophore A23187 + phorbol myristate acetate, produced isolated and tissue-specific responses in muscles incubated under aerobic conditions, but the magnitude and pattern of these responses differed from those seen in anoxia. Second messengers also had no effect on the development of biochemical responses in anoxic muscles. Tissue pH was artificially altered in order to evaluate the role of pH change (acidification occurs during anoxia in vivo) in the control of metabolic responses to anoxia. In all cases, the changes in the kinetic properties of pyruvate kinase (PK) correlated with the state of oxygenation of the tissue and not with the measured tissue pH value; higher tissue pH did not prevent anoxia-induced phosphorylation of PK and lower tissue pH did not alter the kinetic patterns of the aerobic enzyme. Overall, the study indicates that cells and tissues of the whelk respond individually to anoxia and that coordination of the action of protein kinases during anoxia is not mediated by pH or by common second-messenger mechanisms.
Relationship of Wing Beat Frequency and Temperature During Take-Off Flight in Temperate-Zone Beetles
Authors: Oertli J. J.
Published: April 2021

In 24 species of temperate-zone beetles thoracic temperatures (Tth), and wing beat frequency (n) were measured over a range of ambient temperatures (Ta) during take-off flight. The sensitivity of wing beat frequency to thoracic temperature varied greatly in different species: Q10 values ranged from 0·8 to 1·3. The wing beat frequency of beetles with higher average n was more sensitive to thoracic temperature. It is suggested that the temperature sensitivity of wing beat frequency results from temperature-dependent changes in the resonant properties of the beetle flight system rather than from changes in the temperature sensitivity of the muscle or nervous system.

There was large variability in thermoregulatory precision. Beetles with higher n tended to thermoregulate more precisely than beetles with lower n. Measurements of thoracic temperature before and after flight indicated endothermic heat production during pre-flight activity, but not during the brief take-off flights.
Energetically Defining the Thermal Limits of the Snow Crab
Authors: Foyle Timothy P. , O’Dor Ronald K. , Elner Robert W.
Published: April 2021

The snow crab, Chionoecetes opilio, is a cold-water species found naturally at temperatures below 5 °C. Its physiology and energetics were examined to understand the metabolic limitations that restrict the snow crab to these temperatures. The species is not confined to cold water because of a limited respiratory system. Routine oxygen demand can be met even at lethal temperatures of 18°C (56mgO2kg−1h−1, with a Q10 of 2·2). Blood lactate levels remain below 1·5 mmol 1−1 and actually decline slightly with temperature.

Energy budgets, which were constructed from an examination of oxygen uptake, activity and food consumption in morphometrically mature male animals between 0 and 18 °C, indicate that the snow crab is energetically restricted to cold water. Rising metabolic costs overtake caloric intake around 7 °C. This is probably due to digestive metabolism which is temperature-sensitive. Food consumption increases up to 6°C but then falls. Crabs stop feeding above 12°C. Although the growth equation is positive between 1 and 7°C, it becomes slightly negative below 1°C. This observation is unexpected since snow crabs are commonly found between 0 and 1 °C. Slight temperature changes in the natural environment may, therefore, regulate growth and reproduction in this species.
Sodium- and Calcium-Dependent Mechanisms in the Action Potential of the Secretory Epithelium of a Clam Mantle
Authors: Beirão Paulo S. , Nascimento José Hamilton M.
Published: April 2021

The secretory epithelium of the mantle of the clam Anomalocardia brasiliana is excitable. The ionic dependence of its action potentials was investigated. Two distinct phases could be recognized by their ionic dependences. The early spike phase, that appeared in all action potentials, was dependent on the Na+ concentration of the solution in the interstitial space and was insensitive to tetrodotoxin (TTX) at concentrations as high as 36μmoll−1. It was inhibited by local anesthetics, and its repolarization was inhibited by veratrine. The data show this electrogenesis is caused by TTX-insensitive sodium channels located at the basolateral membrane of this epithelium. Cardiac-like action potentials were recorded in several specimens: the rapid Na+-dependent spike was followed by a slower repolarization phase that formed a plateau and increased the action potential duration. The plateau amplitude was markedly increased when the external Ca2+ concentration was increased to 60 mmol I−1 and it was inhibited by the addition of inorganic calcium channel blockers such as Mn2+ and Cd2+. These observations suggest that inward Ca2+ currents cause the sustained depolarization during the plateau.
Second-messenger systems underlying amine and peptide actions on cardiac muscle in the horseshoe crab Limulus polyphemus
Authors: Groome J. R. , Watson W. H.
Published: April 2021

The biochemical mechanisms by which octopamine, catecholamines and the peptide proctolin exert their actions on Limulus cardiac muscle were investigated. Amines produced long-lasting increases in the amplitude of contractions evoked by electrical stimulation. At 10−5moll−1, the apparent order of potency for amine-induced increases in evoked contraction amplitude was dopamine≈ octopamine > norepinephrine ≈ epinephrine. At this dose, amines produced long-lasting increases in the levels of cyclic AMP (octopamine > dopamine ≈ norepinephrine ≈ epinephrine), but not of cyclic GMP, in Limulus cardiac muscle.

Like the amines, the adenylate cyclase activator forskolin enhanced cardiac muscle contractility and increased levels of cyclic AMP, but not of cyclic GMP. The phosphodiesterase inhibitor IBMX produced a transient increase in cardiac muscle contractility, but typically produced long-lasting negative inotropy. This agent increased levels of both cyclic AMP and cyclic GMP in Limulus cardiac muscle.

Proctolin and the protein kinase C activator phorbol dB increased the contraction amplitude of the intact heart and the electrically stimulated myocardium. These compounds, as well as dopamine, elicited sustained contractures and rhythmic contractions when applied to deganglionated Limulus cardiac muscle rings. Unlike the amines, proctolin and phorbol dB did not increase cardiac muscle cyclic AMP levels.

These results suggest that several second-messenger systems may be utilized by amines and peptides to produce excitatory actions on cardiac muscle fibers of the Limulus heart. Cyclic AMP appears to be an important second messenger underlying the effects of amines to enhance cardiac muscle contractility. Pharmacological data suggest that proctolin may alter cardiac muscle contractility and excitability by a mechanism which involves the phosphatidylinositol pathway. Dopamine, unlike the other amines, produces a number of proctolin-like effects and may activate both the cyclic AMP and the phosphatidylinositol systems in Limulus cardiac muscle.
The Effect of Seasonal Acclimatization on the Buffering Capacity and Lactate Dehydrogenase Activity in Tissues of the Freshwater Turtle Chrysemys Picta Marginata
Authors: Olson John M. , Crawford Kenneth M.
Published: April 2021

Freshwater turtles are remarkably tolerant of anoxic conditions, a tolerance essential for animals that spend much of their time submerged (Belkin, 1963). Many metabolic adaptations for efficient anaerobiosis have been elucidated in turtles, and are essential for allowing these animals not only to dive over a wide range of water temperatures (Gatten, 1981) but also to survive the long hibernation during winter in the higher latitudes (see Penney, 1987, for a review).
Dependence of Blood Viscosity on Haematocrit and Shear Rate in a Primitive Vertebrate
Authors: G. Wells R. M. , Forster M. E.
Published: April 2021

Hagfish have an unusual circulation with intravascular pressures that are lower than those in other vertebrates (Davie et al. 1987; Forster, 1989) and since peripheral resistances appear similar to those of teleost fishes (Flood, 1979; Eiger, 1987), it follows that blood flow rates will also be lower. One might therefore predict that the relatively low haematocrits in hagfish (Johansen et al. 1962; Forster et al. 1989) and lack of plasma albumins (Manwell, 1963) would maintain a relatively low blood viscosity at low flow rates when blood tends to become more viscous by virtue of its non-Newtonian behaviour (McDonald, 1974; Fletcher & Haedrich, 1987).
Honeybees can be Trained to Respond to very Small Changes in Geomagnetic Field Intensity
Authors: Walker Michael M. , Bitterman M. E.
Published: April 2021

It has been demonstrated repeatedly (Kirschvink & Kirschvink, 1989; Walker et al. 1989; Walker & Bitterman, 1985, 1989) that free-flying honeybees can be trained to respond to local anomalies in the geomagnetic field, but none of the training methods previously available has been sensitive enough for threshold studies. Here we report some determinations of intensity thresholds with a new and more powerful technique that permits objective measurement of response.
A Malpighian Tubule Lime Gland in an Insect Inhabiting Alkaline Salt Lakes
Authors: Herbst David B. , Bradley Timothy J.
Published: April 2021

The alkali fly, Ephydra hians Say, inhabits alkaline salt lakes which can contain concentrations of dissolved carbonate and bicarbonate as high as 500 mmol l−1. Larvae of the alkali fly possess two pairs of Malpighian tubules. The posterior pair has a morphology similar to that of the tubules of most other insects, but the anterior pair is modified into an enlarged gland containing white microsphere concretions. We describe the ultrastructure of all cell types in both pairs of tubules. Using scanning electron microscope (SEM) X-ray microanalysis and chemical CO2 quantification, we demonstrate that the concretions in the lime glands are composed of nearly pure calcium carbonate. Isolated preparations of lime gland tubules accumulate 45Ca significantly more rapidly than do normal tubules. Although similar to the lime concretions found in the Malpighian tubules of other Diptera, the lime glands of this insect may function to regulate the high concentrations of carbonate and bicarbonate encountered in their aquatic environment. It is proposed that the mechanism of this regulation may be chemical precipitation of carbonate/bicarbonate with calcium in the lumen of these specialized lime gland tubules.
Long-Term Adaptation of a Phasic Extensor Motoneurone in Crayfish
Authors: Mercier A. Joffre , Atwood Harold L.
Published: April 2021

Long-term adaptation (LTA), a phenomenon previously studied in the crayfish claw, was examined in one of the motoneurones innervating the phasic abdominal extensor muscles. The motoneurone was conditioned by electrically stimulating the second root of the third abdominal ganglion in situ for 4 h per day, using trains of stimuli with an average impulse frequency of 2·5 Hz. In juvenile crayfish, 3 days of conditioning produced a marked (81%) reduction in EPSP amplitude, which recovered only slightly during the succeeding 7 days. The quantal content of synaptic currents also decreased (by an average of 65 %). Estimated values of the binomial parameter p were lower for conditioned neurones than for controls, suggesting that the observed decrease in transmitter release involves a decrease in release probability. Conditioned neurones also displayed less synaptic depression than controls during repetitive stimulation at 5 Hz.

In adult crayfish, conditioning for 7 days also produced a marked (74%) reduction in EPSP amplitude and resistance to synaptic depression. These results differ from those of previous work with the phasic axon of the claw closer muscle, which shows virtually no synaptic changes in adults after conditioning for 2 weeks. The ability to exhibit LTA, therefore, is not lost with age in all neurones.
Visual pigments and the acquisition of visual information
Authors: Lythgoe J. N. , Partridge J. C.
Published: April 2021

All the information available to the brain for the interpretation of the visual scene comes from the number of photons absorbed by a very limited number of photoreceptor types which are characterized by their spectral sensitivity. In vertebrates there are considerable differences in the spectral absorption of the rods and cones making up the retinal mosaic of different animals and, in some cases, including fish and primates, there are considerable differences between the cone sets of individuals within a species.

Broadly speaking, the spectral sensitivity of the photoreceptors is related to the spectral distribution of the ambient light and this is particularly true of the colour-biased light under water. When an animal migrates from one visual environment to another, its cone complement may change to that suited to the new conditions. However, significant differences between the cone sets of animals living within the same environment and colour vision polymorphism within a species suggest that visual tasks critical to survival or breeding success require particular visual pigment sets. A start has been made in trying to understand what tasks are best served by different pigment sets.
Descending Interneurones of the Locust Reporting Deviation from Flight Course: What is their role in Steering
Authors: Rowell C. H. F.
Published: April 2021

Some descending intemeurones (DNs) in insects encode deviation from flight course. Intracellular recording reveals their inputs (from eyes, wind hairs, proprioceptive information from the neck and in some cases ocelli). Intracellular stimulation during flight reveals their motor effects. All components of steering (modification of wing stroke, ruddering with the hind legs, ruddering with the abdomen and head rotation) can be initiated by single DNs. Steering in flight involves the concerted action of at least 10 pairs of DNs synapsing with motor neurones and premotor intemeurones. The whole system forms an autopilot, well suited for corrective steering. It is modulated principally by head movements, which have both optical and proprioceptive effects: compensatory head move-ments increase the accuracy of correctional steering by reducing overshoot, and disable the autopilot during turns evoked by directional pulsed ultrasound for purposes of bat-evasion. DNs responding specifically to visual flow fields are also known, but appear to be related to control of velocity rather than to steering.
Processing of mechanosensory signals in local reflex pathways of the locust
Authors: Burrows M.
Published: April 2021

The processing of mechanosensory signals responsible for the reflex adjustment of the posture or movement of the legs of the locust is described in terms of the actions and connections of identified neurones. Signals can be followed from the major classes of exteroceptors of a leg, through their various integrative stages in the central nervous system to their emergence as specific patterns in known motor neurones. Particular emphasis is placed on the integrative roles of two classes of local interneurones. The spiking local interneurones map the leg as a series of overlapping receptive fields and reverse the sign of the afferent input. The nonspiking local interneurones control the output of the motor neurones by the graded release of chemical transmitter and can adjust the gain of a local reflex depending on the position and movements of the joints of that leg.

The reflex movements of one leg must not impair the stability of the animal and must therefore be influenced by events at the other legs. Populations of intersegmental interneurones convey sensory information from one segment to another to ensure such coordination. These interneurones do not produce stereotyped intersegmental reflexes but, instead, alter the performance of a local reflex in a distant leg by making synaptic connections with nonspiking local interneurones. These connections change the effectiveness of the outputs to the motor neurones and consequently the local reflex. The local interneurones therefore play a crucial role both in the production of local reflexes and in the integration of these actions with the movements of the other legs.
Principles of auditory information-processing derived from neuroethology
Authors: Suga N.
Published: April 2021

For auditory imaging, a bat emits orientation sounds (pulses) and listens to echoes. The parameters characterizing a pulse-echo pair each convey particular types of biosonar information. For example, a Doppler shift (a difference in frequency between an emitted pulse and its echo) carries velocity information. For a 61-kHz sound, a 1·0-kHz Doppler shift corresponds to 2·8ms-1 velocity. The delay of the echo from the pulse conveys distance (range) information. A 1·0-ms echo delay corresponds to a target distance of 17 cm. The auditory system of the mustached bat, Pteronotus parnellii, from Central America solves the computational problems in analyzing these parameters by creating maps in the cerebral cortex.

The pulse of the mustached bat is complex. It consists of four harmonics, each of which contains a long constant-frequency (CF) component and a short frequency-modulated (FM) component. Therefore, there are eight components in the emitted pulse (CF1-4 and FM1-4). The CF signal is particularly suited for target velocity measurement, whereas the FM signal is suited for target distance measurement. Since the eight components differ from each other in frequency, they are analyzed in parallel at different regions of the basilar membrane in the inner ear. Then, they are separately coded by primary auditory neurons and are sent up to the auditory cortex through several auditory nuclei. During the ascent of the signals through these auditory nuclei, neurons responding to the FM components process range information, while other neurons responding to the CF components process velocity information.

A comparison of the data obtained from the mustached bat with those obtained from other species illustrates both the specialized neural mechanisms specific to the bat’s auditory system, and the general neural mechanisms which are probably shared with many different types of animals.
The neural coding of auditory space
Authors: Takahashi T. T.
Published: April 2021

The barn owl’s auditory system computes interaural differences in time and amplitude and derives from them the horizontal and vertical coordinates of the sound source, respectively. Within the external nucleus of its inferior colliculus are auditory neurones, called ‘space-specific neurones’, that have spatial receptive fields. To activate a space-specific neurone, a sound must originate from a circumscribed region of space, or, if the sounds are delivered to each ear separately, using earphones, the stimuli must have the combination of interaural time and amplitude difference that simulates a sound broadcast from their receptive field. The sound-localization cues are processed in parallel, nonoverlapping pathways extending from the cochlear nuclei to the subdivision of the inferior colliculus that innervates the space-specific neurones. Processing in the time pathway involves the coding of monaural phase angle, the derivation of sensitivity for interaural phase difference, and the calculation of interaural time difference (1TD) from interaural phase difference. The last process involves groups of neurones in the inferior colliculus whose collective firing signals a unique 1’1 L), even though the activity of each constituent neurone signals multiple ITDs. The projections of these ensembles to the space-specific neurone endow the latter with a selectivity for IHD. Processing in the amplitude channel, about which less is known, initially involves an inhibitory process that sharpens the directional sensitivity of neurones in a lateral lemniscal nucleus. The inhibition is mediated by a commissural projection from the same lemniscal nucleus of the opposite side. At higher levels of the auditory system, neurones that are tuned to a limited range of interaural amplitude differences are found. It is proposed that at these higher stages, interaural amplitude difference, like ITD, is coded amidst an ensemble of neurones.
The Hymenopteran Skylight Compass: Matched Filtering and Parallel Coding*
Authors: Wehner Rüdiger
Published: April 2021

In deriving compass information from the pattern of polarized light in the sky (celestial e-vector pattern), hymenopteran insects like bees and ants accomplish a truly formidable task. Theoretically, one could solve the task by going back to first principles and using spherical geometry to compute the exact position of the sun from single patches of polarized skylight. The insect, however, does not resort to such computationally demanding solutions. Instead, during its evolutionary history, it has incorporated the fundamental spatial properties of the celestial pattern of polarization in the very periphery of its nervous system, the photoreceptor layer. There, in a specialized part of the retina (POL area), the analyser (microvillar) directions of the photoreceptors are arranged in a way that mimics the e-vector pattern in the sky (matched filtering). When scanning the sky, i.e. sweeping its matched array of analysers across the celestial e-vector pattern, the insect experiences peak responses of summed receptor outputs whenever it is aligned with the symmetry plane of the sky, which includes the solar meridian, the perpendicular from the sun to the horizon. Hence, the insect uses polarized skylight merely as a means of determining the symmetry plane of the polarization pattern, and must resort to other visual subsystems to deal with the remaining aspects of the compass problem (parallel coding).

The more general message to be derived from these results is that in small brains sensory coding consists of adapting the peripheral rather than the central networks of the brain to the functional properties of the particular task to be solved. The matched peripheral networks translate the sensory information needed for performing a particular mode of behaviour into a neuronal code that can easily be understood by well-established, unspecialized central circuits. This principle of sensory coding implies that the peripheral parts of the nervous system exhibit higher evolutionary plasticity than the more central ones. Furthermore, it is reminiscent of what one observes at the cellular level of information processing, where the membrane-bound receptor molecules are specialized for particular molecular signals, but the subsequent molecular events are not.
Frameworks of analysis for the neural representation of animate objects and actions
Authors: Perrett D. I. , Harries M. H. , Bevan R. , Thomas S. , Benson P. J. , Mistlin A. J. , Chitty A. J. , Hietanen J. K. , Ortega J. E.
Published: April 2021

A variety of cell types exist in the temporal cortex providing high-level visual descriptions of bodies and their movements. We have investigated the sensitivity of such cells to different viewing conditions to determine the frame(s) of reference utilized in processing. The responses of the majority of cells in the upper bank of the superior temporal sulcus (areas TPO and PGa) found to be sensitive to static and dynamic information about the body were selective for one perspective view (e.g. right profile, reaching right or walking left). These cells can be considered to provide viewer-centred descriptions because they depend on the observer’s vantage point. Viewer-centred descriptions could be used in guiding behaviour. They could also be used as an intermediate step for establishing view-independent responses of other cell types which responded to many or all perspective views selectively of the same object (e.g. head) or movement. These cells have the properties of object-centred descriptions, where the object viewed provides the frame of reference for describing the disposition of object parts and movements (e.g. head on top of shoulders, reaching across the body, walking forward ‘following the nose’). For some cells in the lower bank of the superior temporal sulcus (area TEa) the responses to body movements were related to the object or goal of the movements (e.g. reaching for or walking towards a specific place). This goal-centred sensitivity to interaction allowed the cells to be selectively activated in situations where human subjects would attribute causal and intentional relationships.
A Study of Diffusional Permeability of Water, Sodium and Chloride in Yolk-Sac Larvae of Cod (Gadus Morhua L.)
Authors: Tytler Peter , Bell Michael V.
Published: April 2021

The fluxes of 3H2O, 22Na and 36Cl were simultaneously measured in yolk-sac larvae of cod (Gadus morhua L.) in 34 %o sea water at 4·5 °C. The rates of turnover of all three isotopes were higher than in adult fish. Diffusional permeability coefficients, which relate ion fluxes to surface area, were however lower, indicating that larvae are less permeable than adults. Furthermore, there is close agreement between the diffusional and osmotic permeability coefficients, which supports a previous hypothesis that relatively low drinking rates in marine fish larvae are a consequence of low integumental permeability. Estimates of the sodium and chloride concentrations derived from the equilibrium levels of 22Na, 36Cl and 3H2O indicate that yolk-sac larvae of cod regulate their body fluids hypotonic to sea water. Also, the ionic concentrations of the tissues of yolk-sac cod larvae are similar to those of adults.
Adaptational Responses of Rainbow Trout to Lowered External Nacl Concentration: Contribution of the Branchial Chloride Cell
Authors: Perry Steve F. , Laurent Pierre
Published: April 2021

Whole-body ionic fluxes and gill chloride cell (CC) morphology were monitored in rainbow trout (Salmo gairdneri) exposed acutely or chronically to natural fresh water (NFW; [Na+]=0·120 mmol l−1; [Cl−]=0·164 mmol l−1) or artificially prepared fresh water with reduced [NaCl] (AFW; [Na+]=0·017 mmoll−1; [Cl−]=0·014mmoll−1). Net fluxes of Na+ and Cl− became extremely negative (indicating net NaCl loss to the environment) upon immediate exposure to AFW exclusively as a result of reduced NaCl influx ( and ) and were gradually restored to control rates during prolonged (30 days) exposure to AFW. The restoration of in AFW was due both to increased and to reduced Cl− efflux , whereas the primary response contributing to the restoration of was an increase of . The total apical surface area of branchial CCs exposed to the external environment increased markedly after 24 h in AFW and remained elevated for 1 month as a consequence of enlargement of individual CCs and, to a lesser extent, increased CC density. and were correlated significantly with total CC apical surface area. Plasma cortisol levels rose transiently in fish exposed to AFW. Treatment of NFW-adapted fish with cortisol for 10 days (a protocol known to cause CC proliferation) caused pronounced increases in and as measured in both NFW and AFW. These results suggest that an important adaptational response of rainbow trout to low environmental [NaCl] is cortisol-mediated enlargement of branchial epithelial CCs which, in turn, enhances the NaCl-transporting capacity of the gill as a result of the proliferation of Na+ and Cl− transport sites.
Temporal Changes in the Quality of the Song of a Bush Cricket
Authors: Hartley J. C. , Stephen R. O.
Published: April 2021

The first songs produced by newly adult Poecilimon schmidti (Fieber) are shown to be composed of pure tone bursts. At this time the file is in its pristine condition. After a week of stridulatory activity the songs of the same individual start to be contaminated with anharmonic components, arising from wear damage that occurs to the file teeth and plectrum. The disruption of the pure tone burst adds other elements to the Fourier spectra so that they now become difficult to interpret. The number of plectrum-tooth impacts, normally 2–5, also varies with ageing. Although females responded well to old males there is a possibility that the change in song quality would enable the female to discriminate between males.
The temperature dependence of the time course of growth and decay of miniature end-plate currents in carp extraocular muscle following thermal acclimation
Authors: Harper A. A. , Shelton J. R. , Watt P. W.
Published: April 2021

The effect of temperature (5–35°C) on the decay and growth phases of miniature end-plate currents (MEPCs) was investigated in extraocular muscle from freshwater carp acclimated to either high (28°C) or low (8°C) temperature. The temperature dependence of the time constant of decay (TD) was found to follow an Arrhenius relationship; the relationship between logTD and reciprocal of absolute temperature (1/K) being linear in both groups. The TD of MEPCs recorded from cold-acclimated carp was not statistically significant from that of the warm group. T D was moderately temperature-dependent. Regression gave a Q10 of 1·78 for the warm-acclimated carp, corresponding to an activation energy, Ea, of 41·15 ± 2·17 kJ mol−1. For the cold-acclimated carp, the Q10 was 1·79, and Ea was 41·43 ±2·46 kJ mol−1. Growth time (TG) was less susceptible than TD to temperature change. The relationship between growth time (taken as the time for MEPCs to rise from 20 to 80% of maximum) and temperature was linear for the cold-acclimated group, with a Q10 of 1·34 and Ea of 20·94 ± 4·75 kJ mol−1. The data for the warm group were, in contrast, best fitted by two linear regressions meeting at 15·1°C. At temperatures below 15·1°C Q10 was 3·16 and Ea was 82·20 ± 15·47 kJ mol−1; above 15 °C, Q10 was 1·22 and Ea was 14·15 ± 12·24 kJ mol−1. The acetylcholinesterase inhibitor neostigmine increased TD by approximately twofold and raised TG to approximately 1·4 times control values. These effects were observed across the temperature range scanned for both groups. The results are discussed with reference to the documented effects of temperature and temperature acclimation on membrane lipids and proteins.
Effects of Changes in Locomotor Intensity, Hypoxia and Hypercapnia on Locomotorrespiratory Synchrony During Walking/Running in Canada Geese
Authors: Funk Gregory D. , Valenzuela Ignacio J. , Sholomenko Geraldc N. , Steeves John D. , Milsom William K.
Published: April 2021

To examine the effects of locomotor frequency and respiratory drive on the incidence of locomotor-respiratory coupling (i.e. entrainment), we examined the relationship between locomotor and ventilatory patterns in trained Canada geese that were: (1) running at three speeds (0·40, 0·52 and 0·72ms-1) on a treadmill, (2) free-running at three velocity intervals (0·40–0·72, 1·0–1·5 and 1·5–2·0ms-1) overground, and (3) breathing hypoxic (12 % O2/l % CO2) and hypercapnic (5 % CO2/30% O2) gas mixtures while running at one speed (0·52ms-1) on the treadmill.

The portion of the time that the locomotor and respiratory systems were coupled was significantly greater during overground locomotion (41·1 ±3·2%) than at comparable speeds on the treadmill (29·0 ±2·6%). In addition, a significant increase in coupling with velocity was only observed during overground locomotion (41·1 ±3·2% at 0·40–0·72ms-1 vs 57·7 ±6·3% at 1·5–2·0ms-1). This increase in entrainment appeared to be the direct result of an increase in locomotor frequency per se and not due to the increase in metabolic rate associated with greater locomotion velocity.

The effects of hypercapnia on the degree of entrainment were unclear owing to inter-animal variability; however, hypoxia caused a substantial decrease in entrainment from air-breathing values (34·8 ± 3·9 %) to levels not different from those possible due to chance alone (20%).

Thus, it appears that locomotor pattern does entrain ventilatory rhythm and that the degree of entrainment is partially dependent on limb movement frequency. However, the increased respiratory drive associated with hypoxia appears to override the influence of locomotor rhythm on respiratory pattern, with a subsequent decrease in entrainment.
An in Vitro Model of Post-Exercise Hepatic Gluconeogenesis in the Gulf Toadfish Opsanus Beta
Authors: Walsh Patrick J.
Published: April 2021

During strenuous exercise, fish develop substantial proton and lactate loads. Although acidosis is usually rapidly corrected during recovery (1–2 h), lactate levels often remain elevated for up to 8–12 h. The quantitative role of the liver in clearance of the lactate load during recovery from exercise in fish has received little direct examination. The purposes of this study were (1) to attempt to quantify hepatic contribution to lactate clearance, and (2) to identify factors that regulate hepatic gluconeogenesis during recovery from exercise in fish. Both in vivo and in vitro (isolated hepatocytes) approaches were used. Important blood parameters (pHe, , [lactate], [glucose], [epinephrine] and [norepinephrine]) were measured in the gulf toadfish (Opsanus beta Goode and Bean) during recovery from strenuous exercise, and they conformed to the general patterns for sluggish benthic species noted in earlier studies. When toadfish hepatocytes were exposed to simulated post-exercise conditions in vitro, gluconeogenesis from lactate was stimulated by over 2·5-fold in ‘0–1 h-’ and ‘l–2h-post-exercise periods’. Variation of the extracellular parameters in controlled combinations indicated that exercise-induced changes in [glucose], [epinephrine], [norepinephrine], and [HCO3−] had no significant effects on rates of gluconeogenesis. The observed stimulation of gluconeogenesis could be induced independently by either decreased pH (which lowered Km for lactate) or increased [lactate] (by simple hyperbolic kinetic effects), but the effects were not additive. Despite this potentially adaptive stimulation of gluconeogenesis, I estimate, based on observed in vitro rates and in vivo estimates of lactate load, that hepatic gluconeogenesis accounts for less than 2 % of the lactate load clearance in toadfish.
Structure and Mechanics of Starfish Body Wall
Authors: O’Neill Patricia
Published: April 2021

The structure of the dorsal body wall of the starfish Echinaster spinulosus was studied using polarized light microscopy of frozen tissues, scanning electron microscopy and histology. The collagen fibres of the body wall form a threedimensional orthogonal web. Voids in the web contain ossicles and papulae. The orthogonal web delivers dimensional stability but allows shear necessary for ray torsion. The ossicles and fibres interact to load the fibres in tension and the ossicles in compression.

Strain rates of the dorsal body wall were measured on live animals during typical movements. Uniaxial tension tests of the body wall yielded Young’s moduli of 267MPa (longitudinal), 249MPa (transverse) and 353MPa (bias); curves were essentially linear. The body wall was approximately linearly viscoelastic and showed hysteresis at 0.01 Hz. Stress relaxation over five decades of time (in seconds) yielded relaxation spectra with peaks in relaxation time at 2.96–3.35, depending on test direction. Stress relaxation caused the connective tissue to soften. The surface of fractured stress-relaxed tissue revealed wispy, dissociated fibril tufts, whereas unrelaxed fractures produced blunt-ended fibre bundles. Neural control was necessary for body wall integrity.
Short Communication Power Output from Skeletal Muscle During Linear and Sinusoidal Shortening
Authors: Josephson R. K.
Published: April 2021

Several recent accounts have estimated the maximum sustainable mechanical power available from a skeletal muscle based on measured or assumed force–velocity characteristics of the muscle and the assumption that the muscle, when active, shortens constantly at the velocity that is optimal for power output. Curtin and Woledge (1988) used this approach in estimating how much mechanical power is available from the myotomal muscles of a dogfish to power swimming. The muscles of a fish operate cyclically, shortening and doing work for half a cycle and being lengthened, possibly absorbing work, for the other half-cycle. Curtin and Woledge allowed for the periodic nature of power output by assuming that only half the muscles were active at any time, which is equivalent to assuming that the sustainable power is half the peak power. During swimming, the shape of the trunk of a fish changes sinusoidally with time (Hess and Videler, 1984), and the shortening velocity of a trunk muscle fiber must also vary approximately sinusoidally. Thus shortening velocity cannot be at the optimum velocity for power output through the entire shortening half-cycle: the assumption of shortening at a constant, optimum velocity must overestimate the power output. Weis-Fogh and Alexander (1977) and Pennycuick and Rezende (1984) have also estimated the maximum sustainable power output of muscle based on the assumption of shortening at constant velocity. The principal muscles considered in the latter two studies were flight muscles. For flight muscles, as for swimming muscles, a sinusoidal length trajectory and a sinusoidally varying shortening velocity are more realistic assumptions than a linear length change and a constant velocity of shortening. The following analysis was begun to determine the magnitude of the error that is likely to enter into estimates of power output from the assumption that muscle shortening during normal locomotion is at constant velocity rather than at a velocity which varies sinusoidally with time. It is shown that the assumption of shortening at constant velocity overestimates maximum power output by 20 % or less.
Dactyl Sensory Influences on Rock Lobster Locomotion: II. ROLE IN INTERLEG COORDINATION
Authors: Müller U. W. E. , Clarac François
Published: April 2021

The effects of cyclic electrical stimulation of the dactyl sensory nerve (DN) on the walking pattern of rock lobsters were examined at the two crucial points within the step cycle: the anterior extreme position (AEP) and the posterior extreme position (PEP). Stimulation during the occurrence of the PEP affected neither the movement pattern of the stimulated leg itself nor that of the ipsilateral adjacent legs. Stimulation of the same intensity during the occurrence of the AEP interrupted the oscillation of the stimulated leg and affected the phase relationships of the ipsilateral adjacent legs. The possibility that indirect influences were mediated by coupling to the substratum can be excluded. Neuronal connections may therefore exist between the funnel canal organs (FCO) of a single leg and the motor output of the adjacent legs. The discussion deals with whether the described channels alone are able to fulfil the requirements of a ‘coordinating mechanism’ as described in the literature.
A Peripheral Arterial O2-Sensitive Pathway to the Respiratory Oscillator of the Shore Crab Carcinus Maenas
Authors: Zinebi H. , Simmers J. , Truchot J. P.
Published: April 2021

Experiments on whole crab, Carcinus maenas, as well as on two types of isolated perfused preparations were performed to locate the origin of the O2 chemosensitivity which drives hyperventilation in hypoxia and hypoventilation in hyperoxia.

Electromyographic recordings from the scaphognathite muscles confirmed the existence of strong ventilatory responses in the whole animal exposed to various water oxygen levels. Furthermore, surgical section of the circumoesophageal connectives did not suppress these responses, thereby excluding the cerebral ganglia as the only site or relay for the O2 chemosensitivity.

In semi-isolated preparations in which the thoracic ganglion and anterior arterial system were perfused by saline at various values, extracellular recordings of the motor output in the peripheral ventilatory nerves showed respiratory responses qualitatively similar, but quantitatively weaker, than those observed in the whole animal. These responses were suppressed by bilateral section of the ventilatory nerves or ligation of the anterior sternal artery.

In perfused preparations of the completely isolated thoracic ganglion, respiratory frequency was reduced under hypoxia. This is consistent with a purely metabolic response and excludes a central O2 chemosensitivity at the level of the respiratory oscillator itself.

We conclude that a population of peripheral O2-sensitive chemoreceptors is present within the arterial system in the ventral anterior region, probably around the scaphognathites. These receptors are reversibly stimulated by potassium cyanide, lobeline and almitrine bismesylate, as also are peripheral O2 chemoreceptors in vertebrates.
Mechanics of Forward Flight in Bumblebees: I. Kinematics and Morphology
Authors: Dudley R. , Ellington C. P.
Published: April 2021

Using high-speed cinematography, bumblebees in free flight were filmed over a range of forward airspeeds. A detailed description of the wing tip and body kinematics was obtained from a three-dimensional reconstruction of the twodimensional film image. A technique for determining quantitatively the angle of attack of the wing was developed. Kinematic parameters found to vary consistently with airspeed were body angle, stroke plane angle, geometrical angle of attack, and rotational angles of the wings at the ends of half-strokes. Results of a morphological analysis of the wings and bodies of those insects filmed in free flight are presented for use in later calculations of the lift and power requirements of forward flight.
The Fast Response Mediated by The C3 Motoneurone of Helix is not Attributable to the Contained FMRFamide
Authors: Bewick G. S. , Price D. A. , Cottrell G. A.
Published: April 2021

The C3 neurone of Helix aspersa is known to induce contraction of the ipsilateral tentacle retractor muscle. It is immunoreactive for peptides of the FMRFamide series and immunoreactive FMRFamide nerve fibres occur in the muscle.

Here we found that FMRFamide-like immunoreactivity was released from the isolated muscle following depolarization with high-potassium saline and that such release was calcium-dependent. HPLC characterization of the immunoreactive material in the muscle showed that FMRFamide itself, rather than the other FMRFamide-related peptides known from Helix, accounted for most of the immunoreactivity. Parallel radioimmunoassay (RIA) also showed that FMRFamide predominates in the C3 neurone.

The nicotinic acetylcholine (ACh) receptor antagonists benzoquinonium (10−5mol l−1) and trimetaphan (5×10−5mol l−1) reversibly reduced tension evoked in the muscle by C3 stimulation. These drugs also blocked the muscle response to bath-applied ACh. Physostigmine (5×10−8mol l−1), an acetylcholinesterase antagonist, potentiated the C3-evoked muscle response. Depolarizing excitatory junction potentials recorded in the muscle cells in response to C3 neurone stimulation corresponded 1:1 with action potentials in the C3 neurone. Whereas locally applied ACh evoked a depolarizing response in the muscle fibres, similar to that evoked by C3 neurone activation, locally applied FMRFamide, even at very high doses, did not affect the membrane potential of the muscle cells. Also, exposure of the cerebral ganglia to high-Mg2+/low-Ca2+ saline did not block the C3 neurone-evoked muscle tension. Taken together, these findings indicate that the C3 neurone makes monosynaptic connections with the tentacle retractor muscle cells and that the contraction of the muscle it induces is due, at least in part, to the release of ACh at the neuromuscular junction. The role of the FMRFamide contained in the neurone is not yet clear.
The temperature dependence of the adrenergic Na+/H+ exchanger of trout erythrocytes
Authors: Cossins A. R. , Kilbey R. V.
Published: April 2021

The effects of temperature upon the adrenergic Na+/H+ exchange of rainbow trout erythrocytes have been studied in vitro. The initial rates of H+ ejection and of increase of intracellular Na+ ([Na+1) in adrenergically stimulated cells were highly temperature-dependent, with apparent Arrhenius activation energies of 112.8±10.0 (mean±S.D., N=4) and 84.1±3.0 kJ mol−1 (N=3), respectively. The steady-state [Na+]i following stimulation decreased progressively with cooling, whilst the time required for [Na+]1 to return to control values after removal of agonist was greatly increased. The change in intracellular pH resulting from adrenergic stimulation was reduced by cooling, such that at 4°C adrenergic responses were barely measurable. The effect of temperature upon the steady state [Na+]i and pHi was probably caused by a disparity in the temperature dependence of the transport mechanisms that contribute to the respective steady states.
The Mandibular Ganglion – a new Peripheral Ganglion of the Locust
Authors: Bräunig Peter
Published: April 2021

Paired peripheral ganglia within the locust mandibular segment are described. Each mandibular ganglion contains the cell bodies of 22–25 neurones. Four of these are sensory neurones which innervate the receptor strand of one of the mandibular proprioceptors. The other neurones connect the suboesophageal ganglion with the tritocerebral lobes of the brain, and with the first ganglion of the stomatogastric nervous system, the frontal ganglion.
External Design and Field of View of the Compound Eyes in a Raptorial Neuropteran Insect, Mantispa Styriaca
Authors: Eggenreich U. , Kral K.
Published: April 2021

Visual fields and ommatidial angles of the compound eyes of Mantispa styriaca were determined using luminous pseudopupil and histological-anatomical techniques. The maximal horizontal overlap averaged 42.7° in females and 52.4° in males; females had only one overlap maximum, whereas males had two. In the dorsoventral direction, the binocular field had an overlap of 135.2° in the female and 142° in the male.

In light-adapted eyes, optical acceptance angles reached values of 2.0°, and they reached 3.6° with dark adaptation; interommatidial angles were between 1.8° and 2.3°. The angles were very similar over the entire eye; no acute zone was found in the frontal part of the eye, as the large binocular overlap would suggest. The results are compared with those for the praying mantis: this animal is in no way related to Mantispa but resembles it in appearance and capture behaviour.