bluuebunny/crossref_metadata_2025 huggingface dataset:
Sodium Efflux from the Central Nervous Connectives of the Cockroach
Authors: Tucker Lois E. , Pichon Y.
Published: April 2021

It has been found that the efflux of sodium from intact penultimate connectives of the ventral nerve cord of the cockroach, Periplaneta americana, can be represented by three components with half times of approximately 30 sec, 100 sec and 16 min. The rate at which sodium escapes in the fast component is correlated with the height of the extraneuronal potential developed when a connective is exposed to a high-potassium bathing medium, the slower the rate of sodium escape the larger being the size of the extraneuronal potential. This gives support to the hypothesis that the extraneuronal potential is a diffusion potential brought about by restriction to ion movement imposed by the tight junctions at the inner ends of the perineurial clefts. De-sheathing a connective greatly speeds up the rate of sodium efflux, the fast component being the most affected. These results can be explained in terms of a three-compartment system, the properties of which are affected by stretching and de-sheathing. It is concluded that the movement of ions is regulated at different levels of the C.N.S. but that the peripheral barrier (which is responsible for the production of the extraneuronal potential) may be the most important one in non-steady-state conditions.
A Note on the Biliary System of the Domestic Duck and a Method for Collecting Bile
Authors: Crompton D. W. T. , Nesheim M. C.
Published: April 2021

The morphology of the biliary system of the domestic duck is described. There is a connexion between the hepato-enteric and cysto-hepatic ducts. Consequently, the bile secreted in the right and left lobes of the liver need not drain separately into the duodenum via the cysto-enteric and hepato-enteric ducts respectively. A simple apparatus and method for collecting bile from ducks is described. The method could easily be modified for other animals which possess a gall-bladder.
Ionic Distribution in Amoeba Proteus
Authors: Prusch Robert D. , Dunham Philip B.
Published: April 2021

The intracellular concentrations of K, Na, Ca and Cl in Amoeba proteus are 24·83, 1·08, 2·93 and 9·73 mM/kg cells respectively. Intracellular Na is always slightly higher than that of the external medium when external Ca is low. Addition of Ca to the medium reduces the intracellular concentration of Na by decreasing the permeability of the plasmalemma to Na. The membrane potential of Amoeba proteus in Prescott-James medium is −89·5 mV and is sensitive to changes in both external K and external Na when external Ca is low. Intracellular Na and K are both sensitive to the addition of CN to the external medium. Both Na and K are actively transported in the amoeba ; K is actively accumulated from the external medium and Na is actively expelled from the cell. It has been suggested that the effects of Ca on Amoeba proteus, i.e. reduction of PNa, reduced internal concentration of Na, reduced unidirectional Na and K influxes, and increased membrane resistance are due to Ca binding to the plasmalemma.
Structure and Synaptic Activation of the Fast Coxal Depressor Motoneurone of the Cockroach, Periplaneta Americana
Authors: Iles J. F.
Published: April 2021

Using Procion Yellow dye injection the structure of the fast coxal depressor motoneurone was determined. The cell body of the slow depressor motoneurone was located within the metathoracic ganglion. Intracellular records from the fast motoneurone failed to reveal any post-synaptic response when the largest abdominal giant fibres were stimulated. Smaller abdominal afferent fibres gave an excitatory input.
Aspects of Osmotic and Ionic Regulation in the Sturgeon
Authors: Potts W. T. W. , Rudy P. P.
Published: April 2021

Analyses have been made of the blood and urine of the euryhaline sturgeon Acipenser medirostris and the rates of turnover of sodium and water in both sea water and fresh water have been measured. The blood concentration is rather lower in fresh water than in sea water and the concentration of magnesium ions declines markedly. The rate of turnover of sodium ions is high in sea water and similar to that of marine teleosts. The rate of turnover of sodium is much lower in fresh water but adaptation to fresh water is slow and the animals are more permeable to sodium than are teleosts. The rate of turnover of tritiated water is more rapid in fresh water than in sea water but in each medium it is similar to that of teleosts of a similar size.
Operant Conditioning As A Means of Testing the Ability of White-Crowned Sparrows to Discriminate Star Patterns
Authors: Terhune Elinor C.
Published: April 2021

Operant conditioning can be a valuable technique for investigating biological problems, as has been demonstrated with pigeons (e.g. Meyer, 1964; McDonald, 1968). If an appropriate operant is selected, such as perch-hopping, the technique can be extended to passerine birds. Stevenson (1967) used alighting on a perch as the conditioned response with first-year male chaffinches which lived in the experimental chamber. Bastian & Hothersall (1970) obtained high fixed-ratio responses (FR up to 40) with redwinged blackbirds, which again lived in the experimental cages.
Limited Permeability and Metabolism of L-Glutamate in the Locust Gut Wall
Authors: Murdock L. L. , Koidl B.
Published: April 2021

A method is described which enables the passage of nutrients through the gut wall of locusts to be studied quantitatively in vivo. The method consists of infusing the radio-labelled precursor into the gut lumen while the haemocoel is perfused with saline. The perfusate is collected and analysed. Compared to L-alanine and glycine, intact L-glutamate crosses the locust gut wall slowly, if at all. Metabolism of L-glutamate in the gut wall is extensive, that of alanine markedly less, while there is little metabolism of glycine. It is suggested that limited permeability and extensive metabolism in the gut wall combined to severely restrict the entry of intact dietary L-glutamate into the blood. The gut wall may be an important site of regulation of blood L-glutamate, preventing or hindering influx of this abundant dietary amino acid. The system could be a contributing factor in protecting neuromuscular synapses from non-adaptive excitation by helping to prevent the concentration of blood L-glutamate from rising.
Blood Metabolites After Intestinal Absorption of Amino Acids in Locusts
Authors: Murdock L. L. , Koidl B.
Published: April 2021

After infusion of the locust gut with L-glutamate-U-14C, L-glutamine was found to be the major radioactive product in blood sampled 1 h later. Smaller amounts of alanine were also found. In most experiments not even traces of unchanged L-glutamate were detectable. When D-glutamate was infused, the main radioactive product was D-glutamate, with lesser amounts of glutamine. With L-alanine-1-14C, the major product was unchanged alanine, with smaller amounts of glutamine. With glycine-1-14C, only glycine could be recovered. Gastric caeca, which presumably are the major tissue sites of amino acid absorption, metabolized L-glutamate to glutamine and alanine. Metabolism of glycine was-negligible. Slow infusion of L-glutamate-1-14C into the haemocoel of locusts was followed by recovery of the radioactivity from blood as glutamine. Unchanged L-glutamate was not in evidence. Rises in the blood concentration of L-glutamate appear to be suppressed. This seems not to be the case for D-glutamate, L-alanine, and glycine. Destruction of dietary L-glutamate in the gut wall may be a functional adaptation to help maintain a low blood concentration of the pharmacologically active substance while producing energy required for absorption and tissue maintenance. Should any L-glutamate enter the blood from the gut or other tissue source, it will be converted to glutamine, which suggests the existence of a complementary mechanism for ensuring low blood L-glutamate.
Water Exchange in the Mantle of A Terrestrial Snail During Periods of Reduced Evaporative Loss
Authors: Machin J.
Published: April 2021

Based on surface temperature, steady-state rates of evaporation of the mantle of inactive Otala lactea are very low even down to 1·5 % relative humidity. Mantle permeability is 0·016 mg/cm2/h per mmHg vapour pressure difference. Marked peaks in surface temperature following humidity change are interpreted as net gain or loss of water to the mantle. Smaller fluctuations in surface temperature are interpreted as limited mucusgland activity. The existence of a superficial hygroscopic layer overlying an impermeable barrier in the mantle is discussed.
Electrotonic Coupling Between Identified Large Cells in the Buccal Ganglia of Planorbis Corneus
Authors: Berry Michael S.
Published: April 2021

The electrotonic coupling between three pairs of large neurones in the buccal ganglia is compared.

In both ganglia a large motoneurone (cell 3) is coupled to a smaller, ipsilateral neurone (cell 4) which is probably a motoneurone also. Neither cell is coupled to its symmetric partner. The coupling is quite strong when measured by the transmission of long, intracellularly applied pulses but spikes are considerably attenuated. Resultant EPSPs are of short duration and usually ineffective. Cell 4 produces bursts of spikes but cell 3 is silent unless artificially depolarized close to threshold when it produces a burst of spikes simultaneous with the cell 4 burst; individual spikes are not synchronous. Cell 2, whose function is unknown but which is not involved in feeding, is cross coupled to its symmetric partner. The coupling is strong, and a spike in one cell produces a large electrotonic EPSP, which often reaches threshold, in the other. One cell may drive the other or they may fire simultaneously owing to synchronous pacemaker depolarizations. Short periods of reverberation occur. All observed input was excitatory and chemically mediated. Following nerve stimulation the input is of similar large amplitude (up to 30 mV) in each cell and the resulting spikes are synchronous. The cells are therefore co-ordinated both by common input and direct connexions.
Ciliary Activity and the Origin of Metachrony in Paramecium: Effects of Increased Viscosity
Authors: Machemer Hans
Published: April 2021

In forward-swimming Paramecium the direction of metachronal wave propagation is turned progressively clockwise from forward-right to backward-left if the viscosity of the medium is increased to more than 100 cP. With increasing viscosity the direction of the power stroke is turned clockwise at a lower rate than the direction of waves. This leads to a gradual transformation of the dexioplectic metachrony toward a symplectic pattern. As viscosity is raised the polarization of the ciliary cycle in time and space is progressively reduced, so that the beat becomes increasingly helicoidal. Metachronal coordination gradually breaks down at viscosities of more than about 100 cP, but is retained better at the anterior end of the cell than in more posterior regions. At viscosities above 12 cP the left-handed swimming helix of Paramecium is changed into a right-handed helix. This is produced primarily by the viscositydependent clockwise shift in the direction of the power stroke from backward-right to backward-left. The frequency of peristomal cilia (32/s. at 20 °C) decreases with rising viscosity. Under constant conditions, a posteriorly directed gradient of decreasing frequency can be observed with the stroboscope. Raising the viscosity leads to an increase of the average wavelength from 10·7 µm at 1 cP to 14·3 µm at 40 cP. In the same range of viscosity the wave velocity, which is the product of frequency and wavelength, is reduced from 340 to 200 µm/s, since the drop in frequency exceeds the increase in wavelength. The wave velocity tends to be stabilized by reciprocal relations between frequency and wavelength, if all other factors are kept constant. However, the wavelength is found to be different in forward-swimming and backward-swimming animals at 40 cP without a change in frequency (14·1 bps; 14·3 compared to 12·7µm). This is explained if the metachronal wavelength is increased by decreasing polarization of the ciliary cycle. A working hypothesis is put forward which explains the origin of a metachronal system by the distribution of forces parallel to the cell surface produced by polarized or unpolarized cycles of ciliary movement.
Mechanical Tuning of the Acoustic Receptor of Prodenia Eridania (Cramer) (Noctuidae)
Authors: Adams William B.
Published: April 2021

Mechanical stimulation of the tympanic membrane with vibrating probes eliminates the acoustic tuning of the receptor and allows the mechanical tuning to be determined. Using neural firing rates as a measure of the response magnitude, three separate regions of high sensitivity are found. They are centred at approximately 2, 14 and 60 kHz. Displacements of 0·1 to 1·0 Å suffice for excitation at 60 kHz. The regions of high sensitivity appear to correspond to the first, third and fifth order mechanical resonances of the scoloparium. Comparison with the results of acoustic stimulation experiments indicates that low-frequency acoustic stimuli are filtered out by the acoustic system of the receptor.
The Physiology and Energetics of Bat Flight
Authors: Thomas Steven P. , Suthers Roderick A.
Published: April 2021

Bats are unique in being the only mammals capable of flight. The mobility, speed, and agility associated with this means of locomotion must have been an important factor in their successful radiation, which has made this diverse group the second largest order of mammals. Excluding man, and possibly rodents, bats have the widest distribution of any terrestrial mammals (Simpson, 1945; Walker, 1964; Anderson & Jones, 1967).

Despite a growing literature on the physiology of resting or hibernating bats, almost nothing is known regarding the physiology or energetics of bat flight. Mammalian flight is of particular physiological interest since recent studies of bird flight (e.g. Tucker, 1968b, 1969; Berger, Hart & Roy, 1970) show that it requires a metabolic rate well above the maximum of which similar size, terrestrial mammals are capable during exercise (Pasquis, Lacaisse & Dejours, 1970). Furthermore, birds possess a number of adaptations for flight which are not shared by mammals. In the following research we have measured the energetic cost of flight to a bat and attempted to determine what adaptations permit these mammals to maintain the high metabolic rates for which birds seem so uniquely specialized. Some of the data which we report here were summarized in a brief preliminary report (Thomas & Suthers, 1970).
The Activity of Lateral-Line Efferent Neurones in Stationary and Swimming Dogfish
Authors: Roberts B. L. , Russell I. J.
Published: April 2021

The activity of efferent neurones innervating lateral-line organs on the body of dogfish was followed by recording from filaments of cranial nerve X in 41 decerebrate preparations. The efferent nerves were not spontaneously active. Tactile stimulation to the head and body, vestibular stimulation and noxious chemical stimulation were followed by activity of the efferent nerves. In contrast, natural stimulation of lateral-line organs (water jets) did not reflexly evoke discharges from the efferent fibres. Reflex efferent responses were still obtained to mechanical stimulation even after the lateral-line organs had been denervated. Electrical stimulation of cranial nerves innervating lateral-lines organs was followed by reflex activity of the efferent fibres. But similar stimuli applied to other cranial nerves were equally effective in exciting the efferent system. Vigorous movements of the fish, involving the white musculature, were preceded and accompanied by activity of the efferent fibres which persisted as long as the white muscle fibres were contracting. Rhythmical swimming movements were accompanied by a few impulses in the efferent fibres grouped in bursts at the same frequency as the swimming movements. It is concluded that the efferent neurones cannot contribute to a feedback regulatory system because they are not excited by natural stimulation of the lateral-line sense organs. The close correlation found between efferent activity and body movement suggests that the efferent system might operate in a protective manner to prevent the sense organs from being over-stimulated when the fish makes vigorous movements.
Lung-Air-Sac Anatomy and Respiratory Pressures in the Bird
Authors: Brackenbury John H.
Published: April 2021

Regardless of its tidal volume an individual air sac shows a respiratory pressure-wave which is similar to that of every other sac. These is a process of pressure equilibration within the lung-air-sac system involving very short-lived streams of air between air sacs, whose significance becomes larger as pressure accelerations become bigger; and when a steady state has been achieved in any respiratory phase the pressure wave becomes normalized in all parts of the system. Small pressure differentials between sacs are part of the equilibrium distribution of pressure within the lung-air-sac system. They result from differences in the resistance path through the lung to each sac, and differences in their respective tidal volumes. Their wave-form closely resembles that of the parent pressure waves and has a maximum value of one-tenth their value. In general, the bronchial pathways to the posterior sacs have greater resistances to air flow than those to the anterior sacs. During vocalization pressures in the coelom and air sacs exceed normal respiratory pressures by about 40 times. Airway resistance vastly increases as the syringeal membranes begin to vibrate.
Tension at the Surface of the Dividing Sea-Urchin Egg
Authors: Yoneda Mitsuki , Dan Katsuma
Published: April 2021

Several theories have been put forward to explain the mechanics of cleavage of animal cells. According to the expanding membrane theory of Mitchison and Swann (Mitchison, 1952; Mitchison & Swann, 1955; Swann & Mitchison, 1958), the cleaving furrow is passively pushed in as a result of ‘active’ expansion of poles; while the constricting ring theory (Marsland, 1950, 1956 a, b) anticipates that the furrow region has independent power to contract. A third alternative is ‘astral relaxation theory’ of Wolpert (1960), who advocates that cleavage is initiated by relaxation of the membrane in the polar region which allows the furrow to contract.
A Note on the Paling Centre of the Minnow (Phoxinus Phoxinus L.)*
Authors: Gentle Michael J.
Published: April 2021

The degeneration of the tectal efferent fibres was studied using the paraffin Nauta technique following lesion to the optic tectum in Phoxinus phoxinus L. A degenerating fibre bundle of the tractus tecto-bulbaris ventralis rectus was found to end in a group of neurones in the anterior medulla.
The Control of Changes in Peripheral Sensilla Associated with Feeding in Locusta Migratoria (L.)
Authors: Bernays E. A. , Chapman R. F.
Published: April 2021

The electrical resistance across the tips of the maxillary palps is not affected by stimulation of the palps, but increases to the normal level found after feeding as a result of distension of the foregut with agar or injection of corpus cardiacum homogenates into the haemolymph. No increase in resistance occurs if the posterior pharyngeal nerves or the frontal connectives are cut. It is inferred that distension of the foregut stimulates stretch receptors which, acting via the posterior pharyngeal nerves, the frontal connectives and the brain, cause the release of hormone from the storage lobes of the corpora cardiaca. This hormone acts on the terminal sensilla of the palps, causing them to close and so increasing the resistance across the palps. Release of the diuretic hormone is controlled via the same pathway.
On the Suggestion that the Secretion from the Metathoracic Scent Glands of A Surface-Dwelling Aquatic Insect, Gerris Najas (De Geer), (Heteroptera; Gerridae) Has A Waterproofing Function
Authors: Staddon B. W.
Published: April 2021

Experiments have been carried out which give no support to the suggestion that the secretion from the metathoracic scent glands of the pond skater Gerris najas has a waterproofing function. The ability of the hair pile to resist wetting by surface forces was determined by treatment with graded solutions of pure methyl alcohol in water. In experiments of up to 7·5 weeks duration it was found that the hydrofuge hair pile of insects with sealed scent gland openings was no less resistant to wetting by surface forces than that of the controls.
Osmoregulation in the Larva of the Marine Caddis Fly, Philanisus Plebeius (Walk.) (Trichoptera)
Authors: Leader John P.
Published: April 2021

The larva of Philanisus plebeius is capable of surviving for at least 10 days in external salt concentrations from 90 mm/l sodium chloride (about 15% sea water) to 900 mm/l sodium chloride (about 150% sea water). Over this range the osmotic pressure and the sodium and chloride ion concentrations of the haemolymph are strongly regulated. The osmotic pressure of the midgut fluid and rectal fluid is also strongly regulated. The body surface of the larva is highly permeable to water and sodium ions. In sea water the larva is exposed to a large osmotic flow of water outwards across the body surface. This loss is replaced by drinking the medium. The rectal fluid of larvae in sea water, although hyperosmotic to the haemolymph, is hypo-osmotic to the medium, making it necessary to postulate an extra-renal site of salt excretion. Measurements of electrical potential difference across the body wall of the larva suggest that in sea water this tissue actively transports sodium and chloride ions out of the body.
The Effects of Sodium-Free Solutions on the Fast Action Potentials ofViviparus Contectus(Millet) (Gastropoda: Prosobranchia)
Authors: Sattelle D. B.
Published: April 2021

A 2 h exposure of connectives of Viviparus contectus to sodium-free Ringer, in which dextran maintains osmolarity, results in a decline in the conduction velocity of the fast axons to 50% of the value obtained in normal Ringer. The changes in conduction velocity of the fast axons in response to the replacement in stages of the sodium salts of normal Ringer correspond to those exhibited by conventional excitable cells when tris is the substitute, but depart considerably from this behaviour when dextran is the substitute. Experiments employing mannitol, sucrose, raffinose, inulin and dextran to replace the sodium salts of normal Ringer reveal that dextran alone of these nonelectrolytes maintains fast action potentials in the absence of sodium. Weight losses of connectives under sodium-free (isosmotic) conditions are greatest and are most rapidly achieved when dextran (of the range of non-electrolytes studied) replaces the sodium salts of normal Ringer. Adjusting to isotonic conditions (8 mM dextran) does not diminish the ability of this non-electrolyte to maintain fast action potentials. During prolonged perfusion of connectives by tris Ringer brief (5 min) exposures to dextran Ringer at 15 min intervals rapidly restore fast action potentials. The decline of conduction velocity in these restored fibres closely follows the normal pattern of decline when function is maintained continuously in dextran Ringer.
A Field Study of Flight Temperatures in Moths in Relation to Body Weight and Wing Loading
Authors: Bartholomew George A. , Heinrich Bernd
Published: April 2021

Flight temperatures were measured in representatives of ten families of moths-Sphingidae, Noctuidae, Geometridae, Arctiidae, Saturniidae, Ctenuchidae, Peri-copidae, Lasiocampidae, Notodontidae and Pyralidae. In all cases thoracic flight temperatures and abdominal flight temperatures were higher than ambient, and thoracic temperatures far exceeded abdominal temperatures. Within the individual species, thoracic flight temperature was relatively uniform, and independent of ambient temperatures from 7 to 17 °C. Within the various families, flight temperature was independent of body weight except in the Ctenuchidae and Arctiidae; in these two closely related families, in contrast to all the others, body weight and wing loading were positively correlated. When the families are considered as units, mean thoracic flight temperature increased with mean body weight. Between species in the same family and between families thoracic flight temperatures increased directly with wing loading. However, because thoracic flight temperature is affected by insulation and body weight, species with the same wing loading but belonging in different families may have markedly different flight temperatures. Members of those families that have high flight temperatures and must undergo a pre-flight warm-up have attributes that reduce vulnerability to predation when at rest-threat display, death feigning, production of noxious secretions, and mimicry of stinging insects.
Flapping Flight of the Andean Condor in Nature
Authors: McGahan Jerry
Published: April 2021

At air speeds approximating to those of equilibrium gliding (14–15 m/sec), flapping by Andean condors acts to reduce sinking speed and does so without increasing forward air speed. Apparently the flapping wing provides lift by increasing the speed of the air striking its surfaces and by twisting at the same time so as to present airfoils with optimum orientation toward the changing direction of the relative wind throughout the cycle. Positive or negative components of lift and thrust forces are produced in various combinations depending on the angle of attack. Thrust forces appear at reduced air speeds, a normal condition in take off. In level flight the average velocity of the wind around the wing is greater during the downstroke than during the upstroke because of the anterior rotation of the downstroke axis. Mechanical efficiency of the lever system operating in a wingbeat is greatest during the downstroke so this orientation is important for producing maximum lift forces. The minimum power output generated by a startled condor in escape flight was computed to be 54 W/kg muscle. Assuming (a) the ratio of power output for exceptional and sustained efforts by human muscle (40:17) is similar to that of the condor and (b) the mechanical efficiency for exceptional and sustained efforts is similar, then approximately 23 W/kg wing muscle are available, only about 70% of that estimated as necessary for sustained flight in still air. On the basis of flight performance and of differences in physical dimensions the turkey vulture appears to be capable of more extended flights in still air than the condor.
Two Rates of Relaxation in the Dorsal Longitudinal Muscle of A Leech
Authors: Miller Jennifer B. , Aidley D. J.
Published: April 2021

Experiments were performed to measure the mechanical properties of a preparation of the dorsal body wall of the leech Haemopis sanguisuga. A quantitative histological description of this preparation is provided. It is concluded that the fibres of the dorsal longitudinal muscle are almost entirely responsible for the contractile properties of the preparation, as measured along its longitudinal axis. The preparation was subjected to two types of electrical stimulation. Pulsed stimulation produced a fairly rapid contraction and relaxation. Contraction after a d.c. stimulus was slightly slower, and the relaxation consisted of an initial rapid phase followed by a much slower phase. The extent of the residual tension in this second phase was greater at higher stimulus intensities. The muscle showed some degree of fatigue when subjected to a series of stimuli. Each type of electrical stimulus caused fatigue of both responses. Curare had no effect on relaxation rates. Both phases of relaxation were somewhat slower in the presence of a high concentration of magnesium ion or γ-amino butyric acid, and faster in the presence of 5-hydroxytryptamine. It was thus not possible to separate the two types of response by pharmacological means. The mechanism whereby two rates of relaxation are produced is discussed. It is suggested that d.c. stimulation affects excitation-contraction coupling in some way.
Body-Weight, Energetics, and the Determination of Body Temperature
Authors: McNAB Brian K.
Published: April 2021

An analysis of the influence of body weight on the energetics of endotherms has been proposed by McNab (1970). It was based on the observations that (1) when body temperature is constant heat production equals heat loss, and (2) heat loss may be described as the product of thermal conductance and the temperature differential between the body and the environment: M = C(Tb–Ta). This expression with some misfortune and inappropriateness has come to be called Newton’s law of cooling. Its application means that the energetics of an endotherm has a limited number of degrees of freedom; at a particular environmental temperature, fixing two of the factors will determine the third. It was argued that thermal conductance and the rate of heat production vary with body size and with ecological conditions. Consequently, these factors are mainly responsible for setting the level of body temperature.
Oxygen Dissociation Curves of the Blood of the Tench, Tinca Tinca
Authors: Eddy F. B.
Published: April 2021

Oxygen dissociation curves of tench (Tinca tinca) blood were constructed for fish which had been acclimated to 5, 13 or 20 °C for at least 3 weeks. Compared to the blood of an active fish such as the rainbow trout tench blood, has a high affinity for oxygen; at 13 °C and a of 2–3 mmHg the blood was half saturated with oxygen at a of 4 mmHg. Increasing temperature, increasing and increasing hydrogen ion concentration decreased the oxygen affinity of the blood. At low temperatures the blood had an elevated pH value compared to blood at high temperatures. This is discussed in terms of the temperature dependence of ionization constants, in particular that of water. The Bohr effect and the factors influencing the loading and unloading tensions of oxygen in tench blood are discussed. The role of the blood in respiration and some properties of fish haemoglobins are also discussed.
On the Respiration of the Killifish Oryzias Latipes
Authors: Umezawa Shun-Ichi , Watanabe Hideki
Published: April 2021

It has been shown that many factors are involved in determining the metabolic rate of an individual fish (Fry, 1957; Hughes & Shelton, 1962). The rate of respiration, for example, is influenced not only by environmental factors such as temperature and the concentration of dissolved oxygen and carbon dioxide, but also by such complicated physiological and ecological features as the size, activity and history of the fish, and external stimuli, e.g. light and sound.
Power Input During Flight of the Fish Crow, Corvus Ossifragus
Authors: Bernstein Marvin H. , Thomas Steven P. , Schmidt-Nielsen Knut
Published: April 2021

The fish crow and the laughing gull, although similar in body mass, differ in wing morphology and wingbeat frequency. We studied the power input during sustained flight in the fish crow for comparison with data reported for the laughing gull. Two fish crows (mean mass 275 g) were trained to fly in a wind-tunnel for 15 − 20 min at air speeds of 7 − 11 m s-1 in descending flight at angles of 2 °, 4 ° and 6 ° relative to horizontal. Oxygen consumption was determined by analysing air sampled through a mask and attached trailing air tube. Power input was defined as the rate of metabolic energy expenditure calculated from rate of oxygen consumption. The results were corrected for the drag of the mask and tube, and power input for horizontal flight was calculated. Power input varied little with air speed, but decreased with increasing angle of descent. Minimum power input for horizontal flight (0.083 W g-1) was 6.4 times greater than mean resting power input. During horizontal flight, power input for the fish crow exceeded by about one-third that for the laughing gull.
Membrane Control of Ciliary Activity in the Protozoan Euplotes
Authors: Epstein Miles , Eckert Roger
Published: April 2021

Membrane control of ciliary activity in the protozoan Euplotes was investigated by a combination of electrophysiological and cinematographic techniques. The anal cirri, which are quiescent in the absence of stimulation, were selected for this study. Membrane depolarization by means of injected current produced a reversal of the direction of beating (i.e. towards the cell anterior so as to make the ciliate swim backwards). Depolarization also increased the frequency of beating. Increasing depolarizations resulted in an increased number of reversed beats and increased frequency. When the membrane potential was shifted beyond + 70 mV, reversed beating did not occur until after the current pulse ended. Depolarization did not evoke reversed beating when the external calcium (Ca) concentration was reduced to 10−6 M with EGTA. Hyperpolarization caused the cirri to beat in a normal direction (i.e. towards the rear of the ciliate so as to cause the animal to swim forward). Increasing hyperpolarizations resulted in an increased number of forward beats and an increased frequency. The cell was treated with the detergent Triton X-100 to permit Ca, Mg and ATP direct access through the extracted membrane to the cell interior. At Ca concentrations below 10−7 M, Mg-ATP-reactivated cilia of Triton-extracted cells beat normally. At Ca concentrations above approximately 10−7 M the reactivated beat resembled the reversed beat in the living cell. The evidence suggests that membrane-regulated concentrations of intracellular Ca control the direction of ciliary beating. Thus, stimuli which produce an adequate Ca influx lead to ciliary reversal.
The Eye Muscle of Calliphora Vomitoria L.
Authors: Patterson John
Published: April 2021

A muscle attached to the medial edge of the compound eye is described for the blowfly Calliphora-vomitoria. Electrophysiological activity in the form of continuous tonically firing potentials can be recorded extracellularly from the muscle. These potentials are generated by the muscle and have the same origin as the ‘clock-spikes’ recorded previously from the optic lobe of Calliphora erythrocephala. The interspike interval of the eye muscle potentials varies inversely with the ambient temperature. Light-adaptation results in a decrease and dark-adaptation an increase in the resting interspike interval of the eye-muscle potentials. Light-adaptation is correlated with increase and dark-adaptation with decrease in the depth of the compound eye as measured at the insertion of the muscle. The pseudopupil produced by illumination of the compound eye from the inside displays spontaneous movements which can be correlated with the anatomicall arrangement and spontaneous activity of the eye muscle. The probable function of spontaneous and transient changes in eye-muscle activity is to promote scanning of the visual images produced by the dioptrics of the compound eye.
The Eye Muscle of Calliphora Vomitoria L
Authors: Patterson John
Published: April 2021

Changes in the intensity of the illumination falling on the compound eye produce transient changes in the interspike interval of the tonic potentials generated by the eye muscle of Calliphora vomitoria. These changes are distinct and frequently different in direction from changes in resting activity produced by light and dark adaptation which have been described previously. The effect of ‘light-on’ at high stimulus intensities is to produce a transient increase in the interspike intervals of the eye-muscle potentials. At lower intensities the result is a transient decrease in the interspike intervals. ‘Light-off’ consistently evokes a decrease in the interspike interval, and the magnitude of the decrease is graded with the logarithm of the preceding light intensity. With high-intensity stimuli changes in the interspike intervals occur within 200 msec of a change in illumination and continue to develop for at least 2 sec. The interspike intervals have returned to near to the pre-stimulus values within 30 sec to 2 min of the onset of the stimulus. The behaviour of the eye-muscle system is described for ‘near-threshold’ stimuli and response ‘threshold’ is found to vary with adapting intensity in a way which illustrates a Weber-Fechner relationship.
Activation of the Fibrillar Muscles in the Bumblebee During Warm-Up, Stabilization of Thoracic Temperature and Flight
Authors: Heinrich Bernd , Kammer Ann E.
Published: April 2021

Extracellular action potentials and thoracic temperatures (TTh) were simultaneously recorded from the fibrillar flight muscles of Bombus vosnesenskii queens during preflight warm-up, during stabilization of TTh in stationary bees, and during fixed flight. In most stationary bees during warm-up and during the stabilization of the rate of heat production, as calculated from thoracic temperature and passive rates of cooling, is directly related to the frequency of action potentials in the muscles. The rate of heat production increases throughout warm-up primarily because of a greater spike frequency at higher TTh. In stationary bees during the stabilization of TTh at different ambient temperatures (TA) the fibrillar muscles are activated by any in a continuous range of spike frequencies, rather than only by on-off responses. Regulation of TTh in stationary bees may involve not only changes in the rate of heat production but also variations of heat transfer from the thorax to the abdomen. During fixed flight the fibrillar muscles are usually activated at greater rates at the initiation of flight than later in flight, but the spike frequency and thus heat production are not varied in response to differences in TA and heating and cooling rates. During fixed flight TTh is not regulated at specific set-points; TTh appears to vary passively in accordance with the physical laws of heating and cooling. Differences in the TTh of bees in free and in fixed flight are discussed with regard to mechanisms of thermoregulation.
The Antennular Activities of the Hermit Crab, Pagurus Alaskensis (Benedict)
Authors: Snow P. J.
Published: April 2021

The antennular activities of the hermit crab, Pagurus alaskensis, were studied with the aid of motion pictures taken at speeds of 50, 200 and 400 frames/sec. Most movements of the antennule represent one of four types of antennular activity: flicking, rotation, wiping and withdrawal. These activities are described in detail. Water resistance forces contribute to the timing and duration of some antennular movements. Flicking occurs non-rhythmically and flicks of the left and right antennules ail never synchronized. The factors which influence the mean frequency of flicking are discussed. The timing of joint movements during a flick, and the morphology of the outer flagellum and the aesthetasc hairs, appear to be adapted to facilitate splaying of the aesthetascs. It is proposed that this splaying might facilitate the chemoreceptive process by circulating water around the aesthetasc hairs. During antennular wiping the endopodites of the 3rd maxillipeds are used to remove debris caught amongst the aesthetasc hairs. Light mechanical stimulation of the aesthetascs is sufficient to elicit wiping. The antennules are reflexively withdrawn from certain stimuli either by extension or by slow or fast flexion. The functional significance of the withdrawal reflexes are discussed in relation to the stimuli involved and the form of the reflexes. Continued application of certain stimuli to the antennules, eyestalks, antennae or body results in tonic flexion withdrawal which involves postural modifications of the antennules, eyestalks and antennae.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M.
Published: April 2021

Despite partial degeneration of the larval muscles and reorganization of the nervous system, pupae of the privet hawk moth, Sphinx ligustri, show simple behaviour patterns including abdominal flexion and twirling, and a movement which closes the gin trap. The gin trap closes when the motor neurones driving muscles in the ipsilateral half of the adjacent anterior segment discharge together in a brief high-frequency volley. The system which excites the volley is restricted to these motor neurones and is. activated only by input at a high frequency from triggering receptors. A second system excites efferent neurones in several segments and is driven by triggering and non-triggering receptors. Therefore at low input frequencies the discrimination between the two kinds of receptors disappears. Motor patterns associated with twirling movements drive the efferent neurones. in a sequence which interferes with their simultaneous response to triggering inputs. The arrangement of the closure system shows that the afferent neurones are separated from the efferent neurones by at least one intemeurone.
Mechanisms of Ciliary Co-ordination in Ctenophores
Authors: Tamm Sidney L.
Published: April 2021

An experimental analysis of ciliary metachronism was performed on ctenophores of two types: those with a continuation of the ciliated groove running between adjacent comb plates (lobates), and those in which the ciliated grooves end at the first plate of each comb row (cydippids and beroids). The results showed that the comb plates of cydippids and beroids are co-ordinated by mechanical forces arising from the movement of the plates themselves. Only along the ciliated grooves and at their junctions with the comb rows is a neuroid conduction process likely in this group of ctenophores. Ctenophores with an interplate ciliated groove, on the other hand, do not depend on mechanical interaction between active plates for co-ordination. Instead, the lobates use neuroid conduction at the junction between the interplate ciliated groove and the comb plate, at the junction between adjacent interplate ciliated grooves, and probably along the ciliated grooves and interplate ciliated grooves as well. Ciliary co-ordination may therefore be entirely neuroid in lobate ctenophores. In both types of ctenophores the comb plates may be triggered to beat by depolarization of the comb-plate cells. Electrical excitation of a plate could be caused by mechanical deformation of its base arising from the motion of the preceding plate (in cydippids and beroids), or by a neuroid process at the interplate ciliated groovecomb plate junction (in lobates). These findings resolve a long-standing controversy over the mechanism of ciliary co-ordination in ctenophores.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M.
Published: April 2021

Pupae of the privet hawk moth Sphinx ligustri are equipped with defensive devices known as gin traps. The function of the traps depends on a discrimination between receptors inside and outside their margins. The traps close when the sensilla within them are disturbed. There is no consistent difference in the response of the trichoid sensilla inside and outside the traps. Discriminations between them must depend on a difference in their central connexions. There is no fusion of the afferent axons from individual receptors in the region of the gin trap. Maps of the triggering and non-triggering receptors show that the pupa does not discriminate between receptors inside and outside the trap, but between receptors at different points on the antero-posterior axis. The distinctive feature of the triggering receptors may be their position in a segmental antero-posterior gradient.
The time Course of Pacemaker Inhibition in the Hydroid Tubularia
Authors: Josephson R. K. , Rushforth N. B.
Published: April 2021

Stimulating the DOS, a conducting system in Tubularia, inhibits spontaneous firing of the principal pacemaker systems of the polyp, the NP and HP systems. The overall inhibition is greater the greater the stimulus frequency and there is rebound from inhibition at the end of the stimulation period. The latent period for NP inhibition is 0·4–0·6 sec and the duration of inhibition is 4–5 sec. The time course and extent of NP inhibition is independent of stimulus frequency except at high frequency where there is diminishing effectiveness of inhibition with time. HP inhibition has a similarly long latent period and even longer duration, lasting 15–20 sec. HP inhibition from successive stimuli can sum to produce a more intense effect. The behavioural significance of the inhibition seems to be to reduce spontaneous polyp movements during food capture and ingestion.
Relative Contribution of Synaptic and Non-Synaptic Influences to Response Decrements in A Post-Synaptic Neurone
Authors: Stephens Cathy Lamar
Published: April 2021

Repeated trans-synaptic stimulation of the giant neurone in the abdominal ganglion from Aplysia californica produced decrements of nervous activity. Although the EPSP amplitude decreased during the stimulation, the firing probability of the post-synaptic neurone continued to decrease after the amplitude had reached a constant low value. When the cell was hyperpolarized and stimulated until the EPSP had decreased to a constant low value, the firing probability immediately after removal of the hyperpolarization was the same as with no previous stimulation. These results and previous work suggest that a process occurring in the post-synaptic neurone, independent of synaptic modification, may contribute significantly to habituation-like phenomena.
Cardiovascular and Respiratory Changes During Heat Stress in Rainbow Trout (Salmo Gairdneri)
Authors: Heath Alan G. , Hughes G. M.
Published: April 2021

Trout were subjected to a steady increase in water temperature (1·5 °C/h) from 15 °C until death occurred, while several respiratory and cardiovascular parameters were monitored. Oxygen consumption increased during the warming (Q10 = 2·35 between 16 and 20 °C). At the higher temperatures the increase was more marked (Q10= 4·96 between 20 and 26 °C). Ventilatory frequency increased during the rising temperature with a general levelling off observed above 23 °C. The amplitude of the pressure changes in the buccal and opercular cavities increased more than did the ventilatory frequency. Further analysis of the differential pressure across the gills suggests that the adjustment of respiratory pumping to the increased oxygen demand is predominantly in the volume pumped per stroke (cycle). Heart rate rose steadily with the increasing temperature until about 24– 25 °C, when a bradycardia usually became evident. Synchrony between the heart beat and the respiratory pumps was observed in some preparations at the higher temperatures. Blood pressure increases during the warming were more marked in the ventral aorta than in the dorsal aorta. At the highest temperatures, abnormal cardiac cycles were frequently observed. Arterial oxygen content declined slightly during warming and venous oxygen content dropped to zero above 23 °C. It is suggested that cardiovascular adjustments may be a limiting factor in this type of stress.
Masking of Auditory Responses in the Medulla Oblongata of Goldfish
Authors: Enger Per S.
Published: April 2021

The nervous activity of single auditory neurones in goldfish brain have been measured. Four types of acoustic stimuli were used, (1) pure tones, (2) noise of one-third octave band width, (3) noise of one-octave band width with centre frequency equal to the pure tone, and (4) white noise. Except for white noise, these stimuli produced the same response to equal sound pressures. The white noise response was less, presumably because the frequency range covered by a single neurone is far narrower than the range of white noise. The conclusion has been reached that for low-frequency acoustic signals, the acoustic power over a frequency band of one to two octaves is integrated by the nervous system. The masking effect of background noise on the acoustic threshold of single units to pure tones is strongest when the noise band has the same centre frequency as the test tone. In this case the tone threshold increases linearly with the background noise level. When the noise band was centred at a different frequency from the tone, the masking effect decreased at a rate of 20–22 dB/octave for the first one-third octave for a tone frequency of 250 Hz. For a tone of 500 Hz the masking effect of lower frequencies was stronger and was reduced by only some 9 dB/octave for the first one-third octave.