bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial and Temporal Changes in the Coupling of Cockroach Spiracles to Ventilation
Authors: Miller P. L. 
Published: April 2021

ABSTRACT
Spiracles 10 of Blaberus giganteus can be coupled with ventilation so as to open either with inspiration or with expiration. Similar activity in a mantid has been shown to produce either anteriorly or posteriorly directed ventilating airstreams in longitudinal tracheae. Switching between the two modes of coupling, which can be controlled experimentally, may pass through a maintained transitional stage when both forms occur. Coupling with inspiration involves symmetrical activity in opener muscles of left and right spiracles. However, when coupled to expiration only one spiracle is active. The unilateral application of electrical or mechanical stimuli to various regions of the body causes the spiracle on that side to open with expiration. Medially divided abdominal ganglia still joined to the CNS through the connectives are capable of both forms of coupling. It is suggested therefore that reciprocal inhibitory coupling between coordinating intemeurones and not between motor neurones accounts for asymmetrical activity when the spiracles are coupled to expiration. Spiracles 3, 6, 7 and 8 act in a similar way to spiracle 10 but have higher thresholds. Spiracles 4, 5 and 9 are associated with glandular structures and their activity is different. They may allow chemicals to be expelled through them when the insect is strongly stimulated. A model is presented which accounts for some aspects of the activity of spiracles 10.
Neuro-Muscular Mechanisms of Abdominal Pumping in the Locust
Authors: Lewis G. W. , Miller P. L. , Mills P. S. 
Published: April 2021

ABSTRACT
The muscles involved in dorso-ventral and longitudinal ventilation in the pregenital segments of Schistocerca gregaria are described. Expiratory muscles are shown to be innervated by paired lateral nerves whereas the dorso-ventral inspiratory muscles are innervated by the unpaired median nerve system. Normal pumping activity is brought about by alternating bursts of impulses in expiratory and inspiratory motor nerves. Inspiratory bursts are relatively invariant, whereas expiratory bursts show a positive correlation with ventilatory cycle length. The firing patterns of some units within the bursts are described. In general anterior segments fire motor bursts earlier than posterior segments during well synchronized active ventilation, the metathoracic ganglion firing first. However, much variation is seen both within one locust and between different locusts. Burst-formation continues in isolated nerve cords. Activity, phase-locked with expiration, has been recorded in the connectives. The evidence suggests that it occurs in a pair of co-ordinating interneurones which run from the metathoracic ganglion to the last abdominal ganglion and determine the initiation, duration and possibly the intensity of the expiratory motor bursts in each segment. A second parallel system may co-ordinate activity when the metathoracic co-ordinating interneurones are inactive. Inspiratory motor neurones are probably autoactive and the duration of their firing may normally be determined by the discharge phase of a metathoracic oscillator which acts by inhibiting the co-ordinating interneurones.
The Respiratory Physiology of the Marine Nematodes Enoplus Brevis (Bastian) and E. Communis (Bastian)
Authors: Atkinson H. J. 
Published: April 2021

ABSTRACT
The rate of oxygen consumption of individual male Enoplus brevis and E. communis was measured at 15 °C, after altering the oxygen regime experienced since the animals were collected. When both E. brevis and E. communis were transferred to 35 Torr from atmospheric oxygen tensions, their oxygen consumption was only two-thirds of that of individuals maintained at this lower oxygen tension. The rate of oxygen consumption of the two species at 135 Torr was unaltered by exposure for 2 h to oxygen-free sea water. The results are discussed in relation to the overall influence of fluctuating oxygen regimes on the oxygen requirements of nematodes.
Sensory Mechanisms in Paramecium
Authors: Naitoh Yutaka , Eckert Roger 
Published: April 2021

ABSTRACT
Small, brief mechanical stimuli were delivered with a microstylus to the surface of Paramecium caudatum bathed in solutions of 1 mM-CaCl2, 1 mM KC1 +1 mM Tris HC1, pH 7 2. Stimulation of the caudal end produced a graded hyperpolarizing receptor potential which reached a maximum within 50 msec and decayed more slowly. The input conductance at the peak of the caudal receptor potential increased to a value of at least 6 times that of the resting membrane. The potential diminished in amplitude when the membrane was hyperpolarized by injected d.c. current, and reversed sign with sufficient hyperpolarization. The reversal potential in a solution of 1 mM-CaCl2 + 4 mM-KCl was − 37 mV, while the resting potential was − 20 mV. The peak of the receptor potential was shifted about + 50 mV per 10-fold increase in extracellular K+. C−and Ca2+ and other cations produced little or no shift in the potential peak of the response. It is concluded that mechanical stimulation of the caudal surface produces a local increase in conductance, predominantly to K+. Extracellular tetraethylammonium converts the normally hyperpolarizing receptor potential to a depolarization similar to the potential produced in response to mechanical stimulation of the anterior surface. The TEA effect is antagonized by calcium ions.
Some Evidence for Colour-Blindness in Octopus
Authors: Messenger J. B. , Wilson A. P. , Hedge A. 
Published: April 2021

ABSTRACT
Groups of O. vulgaris were trained successively to make brightness and hue discriminations with painted vertical rectangles. These were of approximately the same physical intensity and were equally preferred. Using one-cue discrimination training we found that (a) Seven octopuses that discriminated between dark blue and light blue did not discriminate between dark blue and dark red shapes. (b) Nine octopuses that discriminated between light red and black did not discriminate between light red and light green shapes, (c) Fifteen octopuses that discriminated between medium green and light green did not discriminate between medium green and medium blue shapes. All these octopuses later discriminated between black and white shapes. Another group of octopuses was trained with two cues, one or both of which were relevant. The cues used were brightness (dark or light) and hue (blue or green), (a) Group 1 (N =14) discriminated between dark and light shapes where hue was irrelevant. (b) Group 2 (N = 14) discriminated between dark blue and light green shapes, (c) Group 3 (N =14) failed to discriminate between blue and green shapes where brightness was irrelevant. Overall the scores of Groups 1 and 2 did not differ significantly. Thus under experimental conditions where octopuses rapidly learned to make brightness discriminations they did not learn discriminations based on hue alone; even if colour is perceived, it seems a relatively unimportant cue for this animal. Another group of octopuses (N = 10) was tested, in a special apparatus, for nystagmus and optomotor responses. Such responses were always given when stripes of different brightness moved relative to the retina, but when stripes of the same subjective brightness but different hue moved across the eyes they rarely occurred. Such occurrences were no more frequent than the responses given to a plain grey background. Similar results were obtained under conditions of illumination ranging from less than 1 lux to 7·5 × 104 lux. The absence of visual response to moving coloured stripes suggests that the failure of octopuses to learn a hue discrimination may be the result of an inherent incapacity at the retinal level. Together with other findings, which are discussed, this strongly suggests that O. vulgaris is colour-blind.
The Circulatory Physiology of Helix Pomatia: III. The Hydrostatic Pressure Changes in the Circulatory System of Living Helix
Authors: Sommerville Barbara A. 
Published: April 2021

ABSTRACT
The pressure changes in the mantle cavity and various parts of the circulatory system of Helix pomatia have been measured. There are characteristic pressure changes associated with the breathing movements, the pattern depending upon the point at which the measurement was made and, in the case of the heart, the position of the body at the time of recording. These pressure changes fall mainly within the range 2–8 cm H2O. The pressure changes associated with contraction of the heart chambers fall within the range 1–2 cm H20 in pulmonary vein and auricle, 10–32 cm H20 in the ventricle, 1–3 cm H2O in the aorta and 1–8 cm H2O in the pericardial cavity. An increased frequency and amplitude of heart beat was associated with an increased rate of blood flow.
Central Control of Postural Orientation in Flatfish
Authors: Platt Christopher 
Published: April 2021

ABSTRACT
Flatfish metamorphose from a larval form that swims upright like a standard fish to an adult that lies on one side, with both eyes on the upper side, having rotated posture 90 ° relative to gravity and the former normal posture. Adult Citharichthys stigmaeus and Hypsopsetta guttulata were used in behavioural and physiological experiments to determine whether the postural change is a peripheral or central phenomenon. Cleared and sectioned specimens verify that the otolith organs, unlike the eyes, do not rotate within the skull, and so do not maintain the normal vertebrate orientation with respect to gravity. Ocular compensation to lateral tilt shows that tactile cues, vision, and the semicircular canals are inadequate to produce tilt responses, but elimination of otolith function abolishes tilt responses. The major postural role of the otolith organs is not lost. Selective removal of otoliths demonstrates that the flatfish utriculus has only a minor role in tilt responses, and that the sacculus-lagena is required, unlike the situation in other vertebrates. The details of the ocular compensation responses are similar to those of standard fishes. Each sacculus lies at an angle of up to 45 ° when in the normal position, but unilateral loss does not change the phase of the response curve, indicating that the null response is set for a non-zero value of gravitational shear, unlike the null at zero shear to the utriculus in other vertebrates. Hysteresis effects suggest a differential sensitivity between tilts near the normal and the upside-down null positions. The narrowness of the effect argues against mechanical restrictions. Possibly the vertical utriculus is useful only near the normal, as an accessory organ, like the vertical lagena in other vertebrates. Neural units recorded from both eighth nerve and medulla show the expected activity properties of regular and irregular rate, tonic and phasic responses to tilt, directional dependence and ‘multi-valuedness’, as in other vertebrates. No novel response types are found, nor any distinctive ‘into-level’ types described for some vertebrates. Vibration sensitivity is associated with irregular rate, and exclusively vibration-sensitive units are apparent only in the utriculus. The shift in functional relations of the otolith organs relative to gravity is not apparently compensated for by any major change in peripheral afferent gravistatic unit properties. An increasing distinction between the null at normal and the null upside-down is shown by limited data on ocular compensation in three year-classes of flatfish. A central change in vestibular function is suggested that might be dependent on experience, as is gradual compensation to a vestibular lesion. Since peripheral changes are not responsible for the postural change, alternative central mechanisms are proposed, including central weighting of input, recognition of a complex input pattern, and plasticity of connexions, all of which have received some supporting evidence from these results.
Effects of Partial Caudal-Fin Amputation on the Kinematics and Metabolic Rate of Underyearling Sockeye Salmon (Oncorhynchus Nerka) At Steady Swimming Speeds
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
Propulsive wavelength, tail-beat frequency, trailing-edge amplitude, critical swimming speed and oxygen consumption rates have been measured for sockeye salmon in which the trailing edge depth and caudal-fin area were variously reduced by partial caudal-fin amputation. The swimming mode was sub-carangiform. The 45 min critical swimming speed for intact fish was 61·6 cm/sec (3·0 l/sec). The critical speed was not significantly reduced by removal of either the epaxial or hypaxial caudal-fin lobes, but was reduced significantly (P &lt; 0·05) to 51·8 cm/sec (2·5 l/sec) when both lobes were removed. The mean length of the propulsive wave was 1·00 body length, and was not affected by the caudal-fin surgery. Both tail-beat frequency and amplitude increased with speed, their product linearly so. Normalization of data in relation to the physiological maximum at the critical swimming speed showed no relative changes in frequency and amplitude. No significant differences were observed in standard or active metabolic rates. General equations describing thrust (Lighthill, 1969) and drag were compared. It was shown that the drag on the caudal fin was markedly increased by lateral propulsive movements as suggested by Bone ‘s boundary-layer thinning hypothesis (Lighthill, 1971). Drag coefficients for the caudal fin were one to two orders of magnitude higher than would be expected in the absence of lateral movements. It is considered that the principal function of the caudal fin is in manoeuvre and acceleration.
The Relations Between Membrane Potential and Parameters of Ciliary Beat in Free-Swimming Paramecium Caudatum
Authors: Offen R. J. , Roberts A. M. 
Published: April 2021

ABSTRACT
A method of analysing the parameters of ciliary beat as a function of membrane potential in free-swimming organisms is presented. The method obviates artefacts which may be produced on impaling small organisms with micro-electrodes. Changes in the membrane potential of Paramecium caudatum produce two effects : an increase in frequency of beat of up to (23 ± 3) % mV−1 at 25 °C for both depolarizations and hyperpolarizations which falls to zero within a few minutes, and a change in the direction of ciliary beat of (9 ± 1) degree mV-1 for depolarizations only, which in a spiralling organism do not accommodate to the field. The orientation of P. caudatum towards the cathode in an electric field is due principally to changes in the angle of ciliary beat on the cathodal side of the organism ; changes in frequency seem to be relatively unimportant. Axial spinning during normal locomotion in P. caudatum is satisfactorily accounted for by transverse components of ciliary thrust. The oblique orientation of P. caudatum near boundaries is caused by an asymmetry (geometrical or electrical or both) over the surface of the organism. Comparison with observations on extracted organisms indicates that a change in the direction of beat of 9° is associated with an increase in calcium concentration at the ciliary apparatus of about 25 %.
Motor Activity During Walking in the Cockroach Periplaneta Americana
Authors: Delcomyn Fred 
Published: April 2021

ABSTRACT
The patterns of electrical activity in selected muscles of the rear legs were studied during locomotion in tethered cockroaches. Stepping movements did not appear significantly different in a tethered insect compared to one which was freely moving. During walking, the muscle potentials due to ‘fast’ flexor and ‘slow’ extensor motoneurones were always grouped into alternating bursts separated by periods of silence, but those due to ‘slow’ flexor motoneurones were not usually grouped in this way. Muscle potentials due to ‘slow’ flexor activity were usually modulated in frequency such that the highest frequencies occurred when in the free-walking insect one would have expected a burst to occur. ‘Slow’ extensor and ‘fast’ flexor bursts were studied in detail. Minor fluctuations of the frequency of impulses within each burst were not related to any other parameter of activity which was measured. For ‘slow’ extensor bursts, the duration of the bursts, the number of impulses per burst and the mean interval between impulses in a burst each increased significantly as the duration of the associated step increased. As in free-walking animals, the rate at which the latter two changed as a function of step duration was often significantly higher for steps shorter than about 300 msec, than for longer ones. However, the absolute value of these two parameters in tethered preparations was about half that at corresponding step durations in free-walking preparations. For ‘fast’ flexor bursts, weak positive correlations between step duration and burst duration, number of impulses per burst and mean interval per burst could be demonstrated only in a few preparations. The relationships were not significantly different from those seen in free-walking preparations. The results suggest that reflex feedback loops can strongly affect some parameters of motor output, such as discharge rate within a burst, but affect others, such as burst duration, only very slightly if at all. A model of the mechanism by which steps may be generated is modified accordingly.
Contraction Kinetics of the Fast Muscles Used in Singing by A Katydid
Authors: Josephson R. K. 
Published: April 2021

ABSTRACT
The sound-pulse frequency, and by inference the wing-stroke frequency, in the song of the katydid, Euconocephalus nasutus, is 160 Hz. The thoracic temperature during singing is 36 °C, which represents a gradient between the insect ‘s thorax and its environment of 12 °C. Contraction kinetics were measured as a function of temperature for a singing muscle (first tergocoxal forewing muscle of males) and homologous, purely flight muscles (forewing muscles of females, hindwing muscles of males). Because the performance of the singing muscle was found to be easily degraded, the measurements were made from nearly intact animals. At 35 °C the contraction rise time for an isometric twitch of a singing muscle is 7·7 msec. The twitch duration, measured from onset to 90% relaxation, is 12·2 msec. Purely flight muscles are about half as fast, but develop more tension per crosssectional area, both in twitches and tetani. The temporal characteristics of twitch contractions, including the delay between the onset of the muscle action potential and the onset of contraction, have Q10 values between 1·5 and 2. At 35 °C a singing muscle contracts in an unfused tetanus when stimulated at 150 Hz, relaxing about half-way between tension peaks. This result suggests that this is the way the muscle operates during singing. At 25 °C the muscle contracts in a smooth tetanus when stimulated at 150 Hz. A warm thorax is not only a consequence of the intense activity during singing but also necessary for the performance achieved. Isometric twitch tension is maximum at muscle lengths more than one-third greater than the in situ length. Twitch contraction time is nearly independent of muscle length but relaxation time increases as the muscle is stretched.
A Technique for the Cultivation of Insect Tissues
Authors: Frew J. G. H. 
Published: April 2021

ABSTRACT
In vitro tissue culture is shown to be a possible mode of experimentation with the tissues of the Blow Fly larva. Methods are described-whereby the tissues, and the body fluids requisite as culture media may be obtained free from bacteria. The imperfections of the technique are noted and the conclusion reached that a successful technique must depend on the rearing of bacteria-free larvae, for which a method is briefly outlined. It is shown that progress in this part of the work must await further physiological knowledge, particularly in respect to the nature of the body fluids.
Observations on the Physiology of the Swim Bladder in Cyprinoid Fishes
Authors: Evans H. M. , Damant G. C. C. 
Published: April 2021

ABSTRACT
The swim bladder of fishes is primarily a hydrostatic organ and with rare exceptions contains or tends to contain the exact quantity of gas which is necessary to make the specific gravity of the whole fish equal to that of the water in which it is swimming, so that it can rest in mid-water tending neither to rise nor sink: this normal condition is called neutral buoyancy. Since gas is compressible and water is not, any increase of external or atmospheric pressure by acting through the non-rigid body walls will reduce the volume of gas in the swim bladder and cause the fish to sink in the water (condition of negative buoyancy). This condition can also be produced by aspirating some of the gas from the swim bladder or by attaching a small weight to the fish.
A New Type of Mammalian Intersexuality
Authors: Baker John R. 
Published: April 2021

ABSTRACT
(1) In certain islands of the New Hebrides (in the Pacific Ocean) a considerable proportion of the pigs are intersexual. Nowhere in the world are intersexual mammals so abundant. (2) These intersexes differ from the rare intersexes of European pigs in the invariable absence of any rudiment of uterus or vagina. (3) A tendency to intersexuality is inherited. (4) The intersexes are interpreted as genetic males in which the testicular hormone has been produced too late in development.
The Effect of Variation in Relative Humidity on Certain Species of Collembola
Authors: Davies W. Maldwyn 
Published: April 2021

ABSTRACT
Authorities have differed regarding the optimum degree of moisture associated with the presence of Collembola. Experiments have, therefore, been carried out to ascertain the influence of variation in relative humidity on the death-rate of certain species of these insects. At a uniform temperature of 25° C. it was found that saturated conditions of the environment are necessary for the survival of all species of Collembola used in the experiments. It has been found that, with the exception of the genus Entomobrya, Collembola devoid of a tracheal system are very susceptible to dry conditions. Sminthurus viridis, which possesses a tracheal system and well-developed ventral tube, is much less susceptible to atmospheric dryness. An experiment carried out with Sminthurus viridis suggests that the ventral tube is used for conveying droplets of water from the hairs of the body to the mouth. It also serves as a “cleaning” organ. The results of the above experiments have had direct practical application in methods of control of Collembola.
The Relation of Electrolytes to the Cardiac Rhythm of Palinurus (Jasus) Lalandii and Octopus Horridus
Authors: Zoond Alexander , Slome David 
Published: April 2021

ABSTRACT
The heart of Palinurus lalandii and the ventricle of Octopus horridus maintain their normal rhythm for long periods in solutions containing only sodium and calcium chlorides. The removal of calcium from the perfusion fluids causes systolic arrest in both hearts. Both hearts are sensitive to very low concentration of potassium when perfused with potassium-free fluid. Excess of magnesium and strontium produce the same effect as excess of calcium, but magnesium cannot be successfully substituted for calcium in the perfusing fluid. The physiological range of H ion concentration is determined for the two preparations. Both hearts have low temperature optima, and the high limit of their range is in the neighbourhood of 20° C.