bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sperm Penetration of the Zona Pellucida of the Pig Egg
Authors: Dickmann Z. , Dziuk P. J. 
Published: April 2021

ABSTRACT
Pig eggs were examined with the ordinary and phase-contrast microscope in search for clues about the process of sperm penetration of the zona pellucida. The following observations were made, (i) The zona pellucida consists of three concentric layers—the inner-zona, the middle-zona, and the outer-zona, (ii) The fertilizing spermatozoon makes a narrow slit in the zona by penetrating through it. The slit has a particular shape referred to as ‘the penetration curve ‘. (iii) Extra spermatozoa (i.e. spermatozoa other than the fertilizing spermatozoon) enter the zona and follow a course very similar to that of the fertilizing spermatozoon, but they can penetrate it only as far as the middle-zona. Extra spermatozoa have not been observed in the inner-zona, indicating that in this layer the ‘zona reaction’ is normally absolute, (iv) A filament extending from the apex of the sperm head has been observed in spermatozoa embedded in the zona. It is suggested that the sperm path through the zona is determined by this filament, which is therefore termed the sperm-penetration filament (SPF). On the basis of these observations the following sequence of events in the passage of a spermatozoon through the zona is suggested. First, the spermatozoon attaches to the zona; it then ejects into the zona the SPF. The SPF, in turn, guides the spermatozoon on its curved course through the zona.
Water Balance in Corixa Dentipes (Thoms.) (Hemiptera, Heteroptera)
Authors: Staddon B. W. 
Published: April 2021

ABSTRACT
The water balance in Corixa dentipes (Thoms.) has been investigated under conditions of starvation in de-ionized water. The rectal fluid was found to contain almost sufficient ammonium bicarbonate to account for the total osmotic pressure. It was invariably strongly hypotonic to the haemolymph. The water output, as estimated by measuring the ammonia output and ammonia concentration of the rectal fluid, was shown to be appreciable but no connexion was found between the output of ammonia and of water. Adults were shown to gain water by the mouth and some evidence was obtained that the cuticle may be an important route of water intake.
Detour Experiments With Octopuses
Authors: Wells M. J. 
Published: April 2021

ABSTRACT
Octopuses will make detours to get at prey seen through a transparent barrier, even though the detours carry them temporarily out of sight of the prey. The possibility of non-visual intermediate cues can be eliminated experimentally. Eight out of 29 octopuses tested made a successful detour at the first trial. The remainder had to be led through the maze by means of a crab on a string on one or more occasions before they did it spontaneously. Once having completed a successful detour down a passage to get into a feeding compartment to the side of the corridor, an octopus rarely failed in subsequent trials, whether making a detour to right or to left. Eleven unoperated control animals, each tested 20 times, totalled only 10 errors, by going into the feeding compartment on the wrong side of the corridor; they failed to make a detour only 13 times in 220 trials. Performance nevertheless showed some improvement with practice. The number of seconds spent attacking through the wall of the feeding compartment before entering the corridor and the number of abortive entries into the corridor both decreased as trials continued. Removal of the statocysts did not stop the high proportion of correct responses. In 39 trials four animals made 6 errors, 3 of them attributable to unilateral blinding of one of the animals (see below). Blinding the animals in one eye led to systematic errors in detours towards the unblinded side. In 63 trials towards the unblinded side, four octopuses made 16 errors and failed to complete the detour 28 times. In 63 trials towards the blind side there were only 4 errors and 9 failures. It is concluded that orientation in detours is maintained by keeping close visual contact with the wall separating the octopus from its prey. The experimental results indicate that octopuses do not take bodily position into account in learning to make detours. Animals trained to make a detour to one side only performed faultlessly when first required to make a detour in the other direction; there is no indication that octopuses are guided by external cues in these experiments. These results are discussed in relation to the organization of motor and learning systems in animals generally. Creatures with hydrostatic skeletons and flexible bodies must of necessity have a decentralized motor control system, and this has important consequences on their learned behaviour.
Experiments on Substrate Selection byCorophium Volutator(Pallas): Depth Selection and Population Density
Authors: Meadows P. S. 
Published: April 2021

ABSTRACTAn apparatus is described for testing substrate-depth preferences of Corophium volutator (Pallas). Corophium burrow in mud whatever its depth, if only one depth of mud is available. If presented with muds of different depths, more animals burrow in the deeper muds. Very shallow muds, of 0·5 cm. depth, are particularly avoided. Although preferring deeper muds, animals are persuaded to burrow in shallow muds when the surface population density in the deeper muds is at a high level (&gt; 0·1 animals/cm.2). This would be explained by a pattern of territorial behaviour which shows itself only at relatively high population densities. Analysis of the distribution of animals at low densities indicates some tendency towards gregariousness. Because of the periodic tendency for animals to vacate their burrows and burrow elsewhere, more than 50% of burrows at very low surface-population densities (ca. 0·01 animals/cm.2) may be unoccupied. Larger animals tend to be found in deeper muds. This would lead to substrate depth influencing the age structure of populations in the field. Limitations imposed by the shape and size of the burrow, rather than animal size in itself, probably explain why animals avoid shallow muds and why larger animals are found in relatively deeper muds.
Responses of Nymphon Gracile (Pycnogonida) to Pressure Cycles of Tidal Frequency
Authors: Morgan Elfed , Nelson-Smith A. , Knight-Jones E. W. 
Published: April 2021

ABSTRACT
The responses of Nymphon gracile to changes in hydrostatic pressure are described. (M, the unit of pressure used here, denotes 1 metre sea water.) A sudden increase in pressure tended to inhibit swimming, while a reduction promoted it, a response opposite in sense to that normally associated with depthregulation. Nymphon showed no adaptive response to cyclical pressure changes similar to those produced by onshore waves. Pressure changes of similar range (1M) but with a 2 sec. period usually induced swimming in previously sluggish individuals. Pressure cycles of 8M range and periods ranging from 14 to 160 min. evoked a depth-regulatory type of response in several individuals, but the majority responded in the opposite way. Nymphon responded to cyclical pressure changes of approximately tidal range (8M) and frequency, by swimming most actively during the late ebb or low water of the artificial cycles. The data of Fage (1932) support the hypothesis that Nymphon swims most often when stimulated by decreasing pressure as the tide ebbs.
The Control of Emergence and Metabolism by External Osmotic Pressure and the Role of Free Glycerol in Developing Cysts of Artemia Salina
Authors: Clegg James S. 
Published: April 2021

ABSTRACT
The effects of external osmotic pressure on the rates of development and emergence, respiration, and on changes in glycogen, glycerol, and trehalose concentrations have been studied in cysts of Artemia salina. The only measured effect of external osmotic pressures less than 30 atm. on emergence and development is to determine the time required for the embryo to emerge from the cyst. Above this value the onset, rate, and final percent of emergence decrease. No emergence occurs at osmotic pressures greater than about 65 atm. The oxygen consumption decreases with increased osmotic pressure, and is negligible at about 65 atm. Several lines of evidence show that trehalose is the respiratory substrate, that most of the trehalose present in the dormant embryo is converted to glycogen and glycerol during development, and that the direction and extent of these conversions are controlled by the external osmotic pressure. Glycerol appears to be present in at least two distinct locations in the cyst: within the embryo, and between the embryo and shell. Glycerol in the latter location is released into the medium at the time of emergence; the embryonic glycerol is rapidly metabolized after emergence. The physiological significance of glycerol and trehalose in the emergence process is discussed.
Tension At The Surface of Sea-Urchin Egg: A Critical Examination Of Cole’s Experiment
Authors: Yoneda Mitsuki 
Published: April 2021

ABSTRACT
The sea-urchin egg can be deformed by external force, and on removing the force it tends to round up. Assuming that the inner protoplasm is liquid, such a return to sphericity must be due to a force working at or near the surface of the egg. The surface force, or the tension at the surface, as referred to by Harvey, has been measured by several methods (Vlès, 1926; Harvey, 1931; Cole, 1932; Cole & Michaelis, 1932; Sichel & Burton, 1936; Norris, 1939). Most of them were reviewed by Harvey & Danielli (1938). Among these workers, however, Cole alone provided information which has been accepted as a proof that the cortex is elastic.
Excretion in the Cephalopod, Octopus Dofleini
Authors: Harrison F. M. , Martin A. W. 
Published: April 2021

ABSTRACT
Although excretory processes in vertebrate animals have been studied extensively during the past fifty years, comparatively few investigations have been carried out on invertebrates. The cephalopod molluscs represent a group which is suited to experimental study due to the large size that has been attained by some of the forms, their relatively high and constant level of metabolic activity and the presence of excretory structures which are accessible and well defined. For these reasons a study was initiated on the large octopus of Puget Sound, Octopus dofleini martini (Pickford, 1964).
Copulation and Egg-Production in Rhodnius Prolixus: The Role of the Spermathecae
Authors: Davey K. G. 
Published: April 2021

ABSTRACT
Mated females of Rhodnius prolixus lay eggs at approximately twice the rate of unmated females. Males which have had their seminal vesicles or opaque accessory glands removed produce spermatophores at mating, but no spermatozoa appear in the spermathecae of the females. The females involved in such matings do not exhibit an increase in eggproduction. When females lacking their spermathecae are mated to normal males, the increase in egg production which follows normal matings does not materialize. Implanting spermathecae from mated females into virgin females increases the egg-production of the host. Implanting spermathecae from virgin females or seminal vesicles or transparent accessory glands from males has no effect on the egg-production of the donor. It is tentatively concluded that a blood-borne factor from the spermathecae containing spermatozoa is the primary stimulus to increased egg production in a mated female.
The Electrical Potential Difference Across the Epithelium of Isolated Gills of the Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Croghan P. C. , Curra R. A. , Lockwood A. P. M. 
Published: April 2021

ABSTRACT
A technique is described for recording the electrical potential differences across the epithelium (epithelial potential) of isolated podobranch gills of Austropotamobius pallipes continuously perfused with Ringer solution in various external media. In a medium of 0·01 Ringer, in which the animals had previously been kept, the mean epithelial potential ± standard deviation was —60 ±12 mV. (Sign defines potential of body fluid with respect to external medium.) Chloride, sodium and potassium must be actively transported into the body fluid against an electrochemical gradient. Calcium and magnesium ions appear to be approximately in equilibrium. The steady-state membrane potentials were recorded in various external concentrations of Ringer solution. The potential is about zero with Ringer solution outside and rises to a maximum with 0·01 Ringer outside. Changes of the electrical potential were recorded when the concentration of a single electrogenic ion was changed in the external medium (0·01 Ringer), and were used to define an apparent transport number of the ion in the outer cell membrane. There was no correlation between the transport numbers and the epithelial potential. There was a continuous gradation of gill types from a predominantly cation-permeable type towards a more chloride permeable type. There is a correlation between the type of gill and the position in the gill series. The properties of the epithelial cells of Austropotamobius gill are significantly different from those of the epithelial cells of frog skin. It is suggested that in Austropotamobius a chloride pump is situated in the outer cell membrane.
The Thermal Dependence of Flagellar Activity in Strigomonas Oncopelti
Authors: Holwill M. E. J. , Silvester N. R. 
Published: April 2021

ABSTRACT
The flagellar beat frequency of Strigomonas oncopelti was found by cinémicro-photography at temperatures in the range 4 − 45 ° C. The thermal dependence is described by an activation enthalpy (ΔH‡) of 15·4 kcal./mole and an activation entropy (ΔS‡) of — i e.u. ΔH‡ is comparable with published data on cilia and glycerol-extracted sperm. Values of ΔS‡ ( — 20 e.u.) deduced from the literature suggest a ratelimiting reaction between ions of like charge although the present value does not support this idea.
Eye Movements of the Dogfish Squalus Acanthi As L
Authors: Harris A. John 
Published: April 2021

ABSTRACT
A method for recording the positions of the eyes of a free-swimming dogfish is described. The eyes of the dogfish do not compensate completely for the lateral swinging of the head which occurs during swimming. The labyrinthine apparatus and the extraocular musculature are capable of providing complete compensation, but this compensation is opposed by influences from the spinal cord. Full compensation during swimming would stabilize only objects at infinity. Partial compensation serves to stabilize a plane of reference close to the fish. Eye movements, allied with the normal zig-zag progression of the fish, serve to eliminate the blind area behind the fish. Other movements of the dogfish’s eyes are discussed, and arranged in five categories. Spontaneous movements of the eyes of resting dogfish are described, and related to the eye movements of swimming dogfish. The spontaneous movements are suggested to be manifestations of an otherwise subliminal central excitatory state affecting turning and swimming.
The Penetration of Acetylcholine Into the Central Nervous Tissues of An Insect (Periplaneta Americana L.)
Authors: Treherne J. E. , Smith D. S. 
Published: April 2021

ABSTRACT
14C-labelled acetylcholine was found to penetrate rapidly into the tissues of the intact abdominal nerve cord. Uptake in the presence of 10−4 M eserine occurred as a two-stage process, the initial rapid influx being identified as the penetration into the extracellular system of the nerve cord. There was a more rapid accumulation of radioactivity in normal preparations as compared with those treated with 10−4 M eserine, presumably as a result of intracellular uptake of the products of hydrolysis of the acetylcholine. The level of radioactivity in the rapidly exchanging fraction was consistent with the hypothesis that the acetylcholine ions were distributed in the extracellular fluid according to a Donnan equilibrium with the haemolymph in eserinized preparations. These results are discussed in relation to the possible physiological role of acetylcholine in synaptic transmission in this insect.
The Lift Produced by the Heterocercal Tails of Selachii
Authors: Alexander R. McN. 
Published: April 2021

ABSTRACT
The upward forces produced by tails of dogfish and tope, moving transversely through water at various speeds, have been measured. The lift is approximately proportional to the 1-4 power of the transverse speed. The equilibrium of dogfish and tope, swimming horizontally with the whole body horizontal, is discussed quantitatively. It is estimated that in each case the hypocaudal lobe, acting passively, would give more lift than is required for equilibrium, at all swimming speeds greater than about 0-5 length/sec. The lift may be adjusted to the required value by means of the radial muscles of the hypocaudal lobe.
Non-Sinusoidal Bending Waves of Sperm Flagella*
Authors: Brokaw C. J. 
Published: April 2021

ABSTRACT
Photomicrographs giving greater resolution than previously available have been obtained for the spermatozoa of a sea urchin, a tunicate, and an annelid. The bending waves are not sine waves. They contain circular arcs, in which the amount of bending is constant, separated by shorter regions which are nearly straight. The flagellum must be effectively very stiff to maintain this waveform as it moves through the medium, but this stiffness must be greatly reduced at the junctions between straight and circular regions, where the flagellum is actively bending and unbending. This type of wave pattern may be generated by a simple ‘on-or-off’ activation of bending elements, but the amount of bending which occurs can be influenced by environmental conditions, such as the viscosity of the medium. A mathematical analysis of the wave movement can be carried out more easily than with sinusoidal waves, and expressions have been obtained for the forward swimming speed, the distribution of bending moment along the flagellum, and the energy expenditure for movement, in terms of the parameters of the waves. The expression for the forward swimming speed accurately predicts the swimming speed of headless spermatozoa, confirming the validity of the hydrodynamic assumptions used in this analysis.
Regulation of Transpiration in the Clover MiteBryobia PraetiosaKoch (Acarina: Tetranychidae)
Authors: Winston Paul W. , Nelson V. Eugene 
Published: April 2021

ABSTRACTGroups of sixteen mites were starved for 48 hr. at 29% R.H. and then exposed for 18 or 24 hr. to one of nine humidities, from 0% to 93% R.H. They were weighed as groups before and after the treatments to determine total weight loss. Dry weights were also obtained to find water content and for the calculation of water and dry-weight losses. All work was done at 25° C. Water loss, considered equivalent to total weight loss, was also obtained under several other conditions; and at all humidities it was found to be highest in mites killed in chloroform vapour while it was considerably less in those killed in HCN gas. Mites with spiracles kept open by air with 10% CO2 lost weight at rates midway between those for dead and those for living animals. There is apparent regulation of body-water content as a percentage of the final weight over the whole humidity range. Water loss is restricted by a CO2-sensitive mechanism, presumably the spiracles. Active regulation of water loss by a cuticular mechanim was shown between 53% and 85% R.H., while at humidities below this, loss was actively restricted but not regulated. It is postulated that both restriction and regulation are brought about by the same mechanism, which might be a form of active transport. Uptake of water from unsaturated air was not found with any of the methods used. Regulation such as was found here would help to maintain the internal environment of these mites as nearly constant as possible in the face of fluctuating humidities.
The Muscular Basis of the Respiratory Pumps in the Trout
Authors: Ballintijn C. M. , Hughes G. M. 
Published: April 2021

ABSTRACT
An account is given of the muscles and skeleton of the trout head and of the mechanisms coupling the different functional components of the skull. The activity of the main respiratory muscles has been recorded electromyo-graphically and simultaneously with pressure and movement recordings from the buccal and opercular cavities. The muscles may be divided into two main groups according to whether they are active during the expansion or contraction phase of the pumps. The protractor hyoideus (geniohyoideus) was found to be active only during the contraction phase. There are differences in the muscles that are active, depending upon the depth of ventilation. Shallow ventilation is maintained by the adductor mandibulae, adductor arcus palatini et operculi, and levator hyomandibulae et arcus palatini. During deeper ventilation the stemohyoideus, protractor hyoideus and hyohyoideus muscles come into action. Only during strong ventilation does contraction of the dilator operculi play a part in opercular abduction. There are variations in the pattern of muscular activity in different individuals and also in the same individual at different times. Such differences in muscular activity are not clearly reflected in the movement and pressure recordings, because of the complex couplings between different parts of the pumping mechanism. As contraction of most muscles affects both the opercular and buccal cavities it is concluded that a model of teleost ventilation based upon a double pumping mechanism must incorporate the couplings between these pumps.
The Muscular Basis of the Respiratory Pumps in the Dogfish (Scyliorhinus Canicula)
Authors: Hughes G. M. , Ballintijn C. M. 
Published: April 2021

ABSTRACTThe mechanism of gill ventilation in the dogfish has been shown to be fundamentally the same as that found in teleost fishes (Hughes, 1960b; Hughes & Shelton, 1962). Water enters the respiratory system through both the mouth and the spiracle during expansion of the oro-branchial cavity (Woskoboinikoff, 1932) and after passing across the gills it enters the parabranchial cavities before being ejected to the outside through the five pairs of gill slits. The flow across the gills is maintained partly as a result of the increased pressure in front of the gill resistances but also because of the suction pump action of the parabranchial cavities. The muscular activities producing the changes in volume of these two cavities and hence the required pressure gradient across the gills have not been established and descriptions of the relationships of muscles and skeleton are not always clear in detail. Woskoboinikoff (1932) and others were of the opinion that the coraco-mandibularis muscle was of importance during the phase of the cycle when the mouth opens and the oro-branchial cavity expands, but this was categorically denied by Balabai (1938) in a footnote to his paper. From observations on dogfish, anaesthetized so that they no longer pumped water across their gills, it was suggested (Hughes, 1960 a) that the main muscular action during the cycle was due to the constrictor muscles. These compress the branchial region and on their relaxation the elastic properties of the skeleton and ligaments are sufficient to account for expansion of the parabranchial cavities. A dogfish in this condition can be made to pump water through its respiratory system by compressing the branchial region by hand. It was also clear in Scyliorhinus that, as had also been observed by Satchell (1959) in Squalus, the respiratory cycle begins with a compression and is followed by relaxation and a relatively long respiratory pause.