bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrimination Between Movements of Eye and Object by Visual Interneurones of Crickets
Authors: Palka John 
Published: April 2021

ABSTRACT
One large neurone on each side of the cervical and thoracic ventral nerve cord of crickets responds to object motion anywhere in the visual field of the ipsilateral compound eye, but not to the forced or voluntary movement of the eye itself. This discrimination between self-movement and object-movement is accomplished by an inhibitory mechanism mediated by the same eye. Inhibition must be present because a potent moving stimulus becomes ineffective if presented during a forced eye movement. Its visual origin is demonstrated in two ways : (a) abolishing all known mechano-sensory feedback does not disrupt the mechanism, but (b) alteration of visual conditions does so in a predictable way. Sweeping the eye past a complex visual environment suppresses the neurone’s response to a concurrently or subsequently presented moving target, whereas the same movement past a simplified or homogeneous environment produces little or no inhibition. Responses to eye movement itself are greatly enhanced in appropriately simplified visual fields, reinforcing the conclusion that the inhibition preventing response in complex fields is of visual origin. Suggestive evidence for an additional inhibitory mechanism associated with voluntary movement is presented.
Energetics of Ciliary Movement in Sabellaria and Mytilus
Authors: Sleigh M. A. , Holwill M. E. J. 
Published: April 2021

ABSTRACT
High-speed cinephotography has been used to study the movements performed by compound cilia from the segmental gills of Sabellaria and from the abfrontal face of the gill filaments of Mytilus. The two types of cilium have distinctly different beat patterns. Equations are derived which allow the calculation of the energy necessary to overcome viscous resistance during the effective and recovery strokes of a cilium in terms of its dimensions and angular frequency. In Sabellaria cilia the energy needed to overcome viscous forces is greater for the effective stroke than for the recovery stroke, but the reverse is true for Mytilus abfrontal cilia. Estimates of the work done to overcome elastic forces are probably too high, but it appears that the elastic work done in the recovery stroke is greater than that in the effective stroke for cilia of both types if the stiffness remains constant throughout the beat. The energy released if each fibrillar arm causes the breakdown of one ATP molecule per beat cycle is greater than that required to overcome viscous resistance to ciliary motion.
The Site of Synaptic Activity and Impulse Initiation in an Identified Motoneurone in the Crab Brain
Authors: Sandeman D. C. 
Published: April 2021

ABSTRACT
Recordings with an extracellular focal electrode have been taken from different points along the length of an identified motoneurone in the crab brain. Measurements of changes in the conduction velocity, wave-form and amplitude of orthodromic and antidromic spikes show that the site for impulse initiation is separated from the synaptic site by about 300 μm of axon which does not actively propagate spike potentials. The regenerative axon spike invades this non-excitable region electrotonically, the current being focused at two points: one close to the synapse and one near the impulse-initiating site.
The Orientation of Plaice Larvae (Pleuronectes Platessa L.) in Water Currents
Authors: Arnold G. P. 
Published: April 2021

ABSTRACT
An apparatus is described to study the response of fish larvae to water currents. Close to the wall of the water tunnel all pelagic larval stages of the plaice showed a typical rheotropic response. Vector analyses of orientation showed that the response occurred only within 3 cm. from the wall and was absent in midwater. Although the ability to swim against the current increased with age, significant upstream movement only appeared in stage III larvae. Laterally flattened stage IV larvae were less able to swim upstream, but on touching the bottom lay on their sides and showed the behaviour of fully metamorphosed stage V larvae and older fish. In dim light ( &lt; 2·5 m. candles) orientation to the current at the side of the tank also disappeared, but observations with an infra-red viewer and source showed that larvae which touched the wall in the dark could still orientate. It was concluded that the mechanism of the rheotropic response was primarily visual, although it could also be produced by tactile clues. There was no evidence that larvae could respond to the velocity gradients at the tank wall.
Gill Dimensions for Three Species of Tunny
Authors: Muir B. S. , Hughes G. M. 
Published: April 2021

ABSTRACT
Measurements of gill dimensions have been made for many species of fish (e.g. Byczskowska-Smyk, 1957, 1958, 1959; Gray, 1954; Hughes, 1966; Price, 1931; Saunders, 1962; Hughes & Morgan, 1969) with the purpose of estimating the total area of the respiratory surface. Of these, only Price (1931) and Hughes & Morgan (1969) have made a serious effort to determine the relation between size and area within single species. Price reported that for Micropterus dolomieu the total area was related to body weight by the power of 0·78. For the roach and several other species, Hughes and Morgan have found that the relationship is closer to the power of 0·9. For the large number of species ranging from ‘sluggish’ to ‘active’ that he examined, Gray (1954) reported about an order of magnitude of range in the total gill area per gram of fish, but specimen size varied considerably. I. E. Gray (personal communication to G.M.H., 1959) has pointed out that it is important to compare fish of approximately the same size. In his 1954 paper he included Scomber scombrus and Gymnosarda alleterata (= Euthynnus alletteratus) and has also reported (personal communication to G. M. H.) data on the blackfin tuna and the yellowfin tuna. Except for this preliminary work, few studies appear to have been reported on members of the genus Thunnus, which is of considerable interest as it includes some of the largest and most active teleosts.
Sound Production in A Brazilian Cicada
Authors: Aidley D. J. 
Published: April 2021

ABSTRACT
Some aspects of the physiology of sound production in the Brazilian cicada Fidicana rana Walker have been investigated. Three types of natural song are described. Singing can also be induced by electrical stimulation of the head. The tymbal muscles are neurogenically activated and contract alternately. The directional properties of the sound field produced by clicking of the tymbal are described, and the physical properties of the system necessary to produce this directionality are discussed. Removal of the abdomen does not decrease the sound intensity during song produced by electrical stimulation, hence it is concluded that the abdominal air sac does not act as a resonant chamber. The means whereby the sound intensity is varied are discussed. A brief account is given of the occurrence of the different types of song in the natural habitat.
Sound Reception in the Brazilian Cicada Fidicina Rana Walk*
Authors: Enger Per S. , Aidley David J. , Szabo Thomas 
Published: April 2021

ABSTRACT
Sound reception in the Brazilian cicada Fidicina rana has been studied by recording the electrical activity in the auditory nerve in response to various sound stimuli. The highest sensitivity to pure tones is in the frequency range of 6-9 kHz. A considerable and rapid adaptation occurs. The response to trains of clicks consists of a series of compound action potentials. At repetition rates above loo/sec. this response also shows adaptation. The response to the natural continuous song of the cicada is not very different from the response to trains of artificially produced clicks. In the two other types of natural song the adaptation of the auditory response is circumvented. Thus the response to the ‘zeep’ call (during which the intensity of consecutive cficks increases) consists of a series of compound action potentials of about the same amplitude, and the response to the distress call consists of a short burst of action potentials for each burst of clicks. It is suggested that these songs therefore constitute very effective methods of intraspecific signalling.
A Functional Analysis of the Aquatic and Aerial Respiratory Movements of An African Lungfish, Protopterus Aethiopicus, with Reference to the Evolution of the Lungventilation Mechanism in Vertebrates
Authors: McMahon B. R. 
Published: April 2021

ABSTRACT
Recent palaeontological evidence (Jarvik, 1967; White, 1966) indicates that the Dipnoi should be regarded as a specialized group of fishes, which have been structurally different from the Rhipidistia (now thought to have included the prototetrapods) for as long as the fossil record can yet show. However, the homology of the dipnoan lung with that of the tetrapod, and the similarities of organization and development between living Dipnoi and Amphibia, might indicate a closer relationship between the two groups than can be revealed by palaeontological studies. The level of organization seen in the living Dipnoi is not thought to be basically different from that of the Devonian forms and a study of the physiology of these animals must expand our knowledge of the development of vertebrate physiological mechanisms. Since the Dipnoi are adapted to a habitat very similar to that in which the first terrestrial verte-brates are thought to have evolved, and since they possess functional aerial and aquatic respiratory systems, a study of respiratory function in these animals may help to elucidate the manner in which the ancestral tetrapods became able to colonize the terrestrial habitat.
Structure of the Retinae of the Principal Eyes of Jumping Spiders (Salticidae: Dendryphantinae) in Relation to Visual Optics
Authors: Land M. F. 
Published: April 2021

ABSTRACT
The retinae of the principal (AM) eyes of jumping spiders contain four layers of receptors, one behind the other with respect to the incident light. The distribution of receptors in each layer has been determined. The deepest layers (1 and 2) cover the whole area of the retina, and have the greatest density of receptors. The minimum receptor separation is 1.7 μm., or 11 min. visual angle. The more superficial layers (3 and 4) are confined to the central region of the retina. In layers 1, 2 and 3 the rhabdomere-containing segments are rod-shaped, and are parallel to the incident light. In layer 4 they are ovoid, and are oriented approximately at right angles to the light. At the first optic glomerulus the primary fibres from each receptor layer appear to terminate in separate regions of neuropile. The focal lengths, radii of curvature and refractive indices of the lenses of the principal and side eyes have been measured. For the principal eyes, estimates have also been made of the diffraction limit, the depth of focus, and the magnitudes of chromatic and spherical aberration. The normal position of the image in the eye was found by ophthalmoscopy. For blue-green light, the best image of distant objects is formed on the next-to-deepest layer (2). The deepest layer (1) is conjugate with a plane about 2 cm. in front of the animal for blue-green light, or with infinity for red light, because of the eye’s chromatic aberration. Two theories are offered to account for the retinal layering. Either the spider uses different layers to examine maximally sharp images of objects at different dis tances; or each layer exploits the sharpest image of distant objects, but for light of different wavelengths. Optical considerations indicate that either theory is possible, but the seconds (wavelength) theory is the more probable, because jumping spiders are known to possess colour vision. It predicts that layer 1 receptors contain red-sensitive, layer 2 blue-green sensitive and layer 3 violet-ultraviolet Sensitive pigments. The structural peculiarities of the most superficial layer (4), and the fact that it is not conjugate with any plane in front of the animal for any visible wavelength, suggest that it is not resolving an image, but performing some other function. Reasons are given for thinking that this might be the analysis of the pattern of polarization of skylight.
Movements of the Retinae of Jumping Spiders (Salticidae: Dendryphantinae) in Response to Visual Stimuli
Authors: Land M. F. 
Published: April 2021

ABSTRACT
Movements made by the principal eyes of jumping spiders (Phidippus and Metaphidippus spp.) have been investigated using an ophthalmoscopic technique which permits simultaneous observation and stimulation of the retinal surface. The eye-movements are produced by six muscles. Four are attached to the carapace, and displace each retina latero-medially and dorso-ventrally. The remaining pair are thin bands of muscle which encircle the eye-tube. TThe nerve supplying these muscles contains only six axons. Each axon terminates in one of the six muscles. The nerve supplying these muscles contains only six axons. Each axon terminates in one of the six muscles. Four types of eye-movements are observed. These are spontaneous activity, saccades, tracking and scanning. All movements are usually conjugate. Spontaneous activity consists of a very variable, periodic side-to-side motion of the retinae. It is associated with states of high excitability, and occurs whether or not there is any structure in the field of view. Saccades occur when a small stimulus (e.g. a dark dot) is presented to, or moved upon, the retinae of either the principal eyes or the antero-lateral eyes. In a saccade the retinae move towards the image of the target so that they come to rest with their central regions fixated on the target. If the target moves the retinae track it, maintaining central fixation. Scanning normally follows a saccade. It consists of an oscillatory, side-to-side movement of the retinae across the stimulus, with a period of 1-2 sec., and a simultaneous torsional movement in which the retinae partially rotate about the visual axes, through an angle of approximately 50° and with a period of 5-15 sec. Jumping spiders distinguish other jumping spiders from potential prey by the geometry of their legs. It is suggested that scanning is a pattern-recognition procedure in which the torsional movements are concerned with the spatial alignment of line or edge detectors, and the horizontal component with providing relative motion between these detectors and the stationary stimulus.
Rapid Contractions and Associated Potentials in A Sand-Dwelling Anemone
Authors: Pickens Peter E. 
Published: April 2021

ABSTRACT
Two kinds of electrical potentials can be recorded from the surface of the. retractor muscle of the anemone, Calamactis, during rapid contraction. These are large muscle action potentials and smaller pulses which are thought to be nerve spikes The latter resemble nerve impulses of higher organisms in that they are all-or-none and of short duration. A nerve spike follows each of a pair of electrical stimuli, but the muscle potential and contraction occur only after the second shock, indicating that facilitation is required at the neuromuscular junction. The size of the muscle potential and of the contraction are correlated with the interval between paired electrical stimuli. Maximum size is reached when stimuli are zoo msec. apart even though the minimum effective interval is 30 msec. A muscle potential precedes contraction only along the upper part of the retractor muscle and this is the part that contracts rapidly during the withdrawal response. The lower retractor does not contract. Conduction velocity along the upper retractor is higher than along the lower. The histological correlate of rapid conduction is a nerve net with large, long, longitudinally oriented fibres. The refractory period of the conducting system of the upper retractor is shorter than that of the lower retractor. Consequently, spread of excitation toward the aboral end is limited if paired stimuli are further apart than 250-300 msec. A mechanical stimulus which is just strong enough to elicit a withdrawal response evokes a single muscle potential of maximum size, suggesting that two nerve impulses closer together than 200 msec. precede the muscle potential. Stronger mechanical stimuli evoke a burst of muscle potentials.
Reflex Organization in the Swimmeret System of the Lobster
Authors: Davis W. J. 
Published: April 2021

ABSTRACT
The intrasegmental feedback reflexes in the swimmeret system of the lobster Homarus americanas were activated while recording the responses from the swimmeret nerves and muscles. Two main sources of sensory feedback were identified; proprioceptors in the coxal region of the swimmeret, and sensory setae on the edges of the two rami of each swimmeret. The reflexes activated by these inputs are described. Reflexive feedback from the powerstroke movement to the powerstroke excitatory motor neurones is positive, further reinforcing the movement. Intrasegmental reflexes capable of independently initiating or terminating the powerstroke activity are absent, however. Therefore the powerstroke movement of each cycle can begin and end only in response to a purely central nervous motor command. It follows that the intrasegmental swimmeret reflexes are incapable of contributing to the periodicity seen in the motor output pattern which underlies swimmeret beating. In addition to strengthening the powerstroke, the intrasegmental reflexes strengthen the linkage between the powerstroke and the returnstroke within each movement cycle. The reflexes may also reinforce the reciprocity between excitor and inhibitor axon activity to the main powerstroke and returnstroke muscles. It is shown, however, that these three features of the motor output pattern are programmed into the CNS independently of the sensory feedback. The intrasegmental reflexes thus act as subservient amplifying devices for cyclic motor patterns which are produced independently by purely central nervous mechanisms.
Active Transport and Sodium Fluxes at Moult in the Amphipod, Gammarus Duebeni
Authors: Lockwood A. P. M. , Andrews W. R. H. 
Published: April 2021

ABSTRACT
The sodium fluxes of individual Gammarus duebeni, which moulted in sea water, have been followed daily from the morning following moult for at least 6 days. Sodium influx from sea water declined from 15·1µM/animal/hr. on the first morning after moult to 1·7 µM/animal/hr. by the tenth day after moult. Sodium influx from 10 mM/l. NaCl plus sucrose solution isotonic with sea water declines from 4·48 µM/animal/hr. to 0·14 µM/animal/hr. in inter-moult animals. Thionine inhibits over 90% of the influx from 10 mM/l. NaCl plus isotonic sucrose on the first day after moult, and this, together with other evidence, suggests that the major part of the influx from this medium is due to active sodium uptake. The rate of active uptake is comparable with, or faster than, the rate of uptake by animals acclimatized to fresh water. The influx occurs primarily across the body surface. It is suggested that the high level of sodium uptake is associated with the water uptake which occurs at moult.
The Input-Output Organization of A Pair of Giant Neurones in the Mollusc, Anisodoris Nobilis (Macfarland)
Authors: Gorman A. L. F. , Mirolli M. 
Published: April 2021

ABSTRACT
Each of the two gastro-oesophageal ganglia of the nudibranch mollusc, Anisodoris nobilis, contains one giant neurone (G cell) whose axon is directed toward the oesophagus in the gastro-oesophageal nerve. In the absence of stimulation the G cells are normally silent. However, they receive inhibitory and excitatory synaptic inputs from more central ganglia and a predominantly excitatory input from the periphery. The inputs from the central ganglia are bilaterally distributed to both G cells, whereas the inputs from the periphery are limited to the ipsilateral G cell. Intracellular stimulation shows that there is no interaction between the G cells, nor between the G cell and other cells in the same or contralateral gastro-oesophageal ganglia. The axon of the G cell makes synaptic contact with a series of peripheral cells (P cells). In most P cells the post-synaptic potential elicited by intracellular stimulation of the G cell is constant in amplitude and latency and probably results from a unitary monosynaptic contact. Intracellular stimulation shows that the P cells are not connected to the G cell. The P cells are inter-connected by low-resistance electrotonic junctions which allow slow potentials of either polarity to spread between cells. These junctions exist between distant as well as adjacent peripheral neurones. Our results show that the G cell functions as a command interneurone for an aggregate of electrically interconnected peripheral neurones.
The Reactions of the Plaice (Pleuronectes Platessa L.) to Water Currents
Authors: Arnold G. P. 
Published: April 2021

ABSTRACT
Observations were made on the reactions of plaice (2-28 cm. length) to water currents in a small flume (30 × 32·5 × 550 cm.), and a behaviour pattern is described. At a threshold velocity fish turned to face upstream, usually showing burying movements or a clamped-down posture. With increasing current velocity they remained on the bottom, showing a posterior fin-beating response. Fish displaced by the current reacted firstly by moving upstream on the bottom and re-settling and at higher velocities by bursts of swimming in midwater. A velocity was finally reached at which each fish was displaced downstream over the weir. On a sandy bottom small buried plaice did not usually react to the current until the covering layer of sand was eroded away. Observations with an infra-red viewer showed that although the typical optomotor response shown in midwater disappeared in the dark, behaviour on the bottom remained the same as in the fight. The lowest velocity at which fish turned to face the current was o·8 cm./sec. and most fish orientated at a velocity below 8 cm./sec. ; there was no increase in threshold velocity with length. There was great variation in the velocity at which individual fish were finally displaced, but there was a general increase with length from 50 to 70 cm./sec. A displacement velocity was found for anaesthetized fish (24−30 cm. length) heading upstream, which was significantly higher than for those heading downstream. Photographs of the flow patterns over live fish on the bottom showed that they were most effectively streamlined when heading directly upstream. Injection of dye showed that water penetrating beneath the fish was ejected by the posterior fin-beating response, and that the operculum of the ocular surface only was used to exhale water from the gills. Experiments with water jets demonstrated three areas whose stimulation elicited a behavioural response shown in the current. These were the leading edges of the body on either side of the head, including the right nasal papilla, and the tail. The results are discussed in relation to the ecology of the plaice and the contranatant theory of fish migrations. It is concluded that the observed behaviour is hydrodynamically advantageous in maintaining station on the sea-bed.