bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Gas Gland Metabolism and Blood Flow on Gas Deposition into the Swimbladder of the European Eel Anguilla Anguilla
Authors: Pelster Bernd , Scheid Peter
Published: April 2021

The effects of blood flow through, and metabolic activity in, the swimbladder epithelium on gas deposition into the swimbladder have been analysed in the European eel, Anguilla anguilla. Blood flow in the artery supplying the retia was measured by Doppler flow probes; measurement of O2 and CO2 content in arterial and venous blood samples from the swimbladder allowed calculation of the rates of O2 removal from, and CO2 addition to, swimbladder blood. 83% of the O2 removed from the blood was transferred into the swimbladder lumen and only 17% was metabolized in the tissue. In spite of the deposition of CO2 into the swimbladder lumen, the CO2 content in rete venous blood was higher than that in arterial blood, indicating production of CO2 in the swimbladder tissue. The respiratory exchange ratio, calculated from O2 consumption and CO2 production of the swimbladder tissue, was significantly greater than one. Gas deposition into the swimbladder increased with increasing swimbladder arteriovenous pH difference, indicating acid release from gas gland cells, and thus their metabolic activity. The rate of gas deposition into the swimbladder increased with increasing blood perfusion of the swimbladder tissue. Under hypoxic conditions, gas deposition was significantly reduced, as was blood flow through the swimbladder tissue. The decrease in gas deposition during hypoxia coincided with a reduction in the swimbladder arteriovenous pH difference. The results therefore demonstrate that the rate of gas deposition is dependent on blood perfusion of the swimbladder tissue and on metabolic activity of the swimbladder tissue, both of which are reduced under hypoxic conditions.
Actions of Ion-Transport Peptide From Locust Corpus Cardiacum on Several Hindgut Transport Processes
Authors: Audsley Neil , Mcintosh Chris , Phillips John E.
Published: April 2021

Schistocerca gregaria ion-transport peptide (Scg-ITP), a neuropeptide isolated from locust corpora cardiaca, stimulates ileal Cl − transport (Isc) in a dose-dependent manner and causes increases in Na+, K+ (IK) and fluid reabsorption (Jv) as previously observed with crude extracts of corpus cardiacum and with cyclic AMP. Unlike cyclic AMP, Scg-ITP does not stimulate ileal NH4+ secretion. H+ secretion (JH) in the ileum, which is not affected by cyclic AMP, is almost completely abolished by Scg-ITP. Although ITP may act via cyclic AMP as second messenger to stimulate NaCl, KC1 and fluid reabsorption, it apparently acts through a different intracellular pathway to influence xJH. Scg-ITP is unlikely to be the chloride transport stimulating hormone previously reported to act on the rectum, because it did not produce a maximum rectal Isc response and had no effect on either rectal Jv (which is Cl− -depcndent) or IK.
Direct Measurement of Mass Loss During Discontinuous Ventilation in Two Species of Ants
Authors: Lighton John R. B.
Published: April 2021

A central controversy in the field of insect ventilation is the effect of the discontinuous ventilation cycle (DVC) on respiratory water loss rates. An accurate method of measuring water loss rates during the ventilation cycle would provide a direct means of resolving the controversy. It would also create opportunities for the comparative study of respiratory water loss rates in insects that employ different ventilation strategies and occupy different habitats.
Further Efforts at Training Pigeons to Discriminate Changes in the Geomagnetic Field
Authors: Couvillon P. A. , Asam Anne M. , Bitterman M. E.
Published: April 2021

Although magnetic sensitivity in pigeons can reasonably be inferred from the impairment of homing by magnetic attachments to their heads (e.g. Keeton, 1971; Walcott and Green, 1974), which have been found to contain magnetite (Walcott et al. 1979), attempts to develop training methods suitable for systematic psychophysical analysis have been largely unsuccessful. Of four classical conditioning experiments with magnetic change as the conditioned stimulus, shock as the unconditioned stimulus and overt activity (Orgel and Smith, 1954) or cardiac acceleration (Beaugrand, 1976; Kreithen and Keeton, 1974; Reille, 1968) as the conditioned response, only one (Reille’s) gave any indication of conditioning. Of three experiments in which pigeons were rewarded with food or water for pecking a target in response to magnetic change (Alsop, 1987; Meyer and Lambe, 1966; Moore et al. 1987), all gave negative results. Bookman (1977) had some success with a flight tunnel in which his animals were rewarded for going to one or the other of two food boxes depending on the prevailing magnetic field, but the results of similar experiments by subsequent investigators were negative (Carman et al. 1987; Mclsaac and Kreithen, 1987).
Voltage-Activated Currents in Somatic Muscle of the Nematode Parasite Ascaris Suum
Authors: Martin R. J. , Thorn P. , Gration K. A. F. , Harrow I. D.
Published: April 2021

Voltage-activated currents in cell bodies of the somatic muscle cells of Ascaris suum were studied using a two-microelectrode voltage-clamp technique. Cells recorded from had resting membrane potentials around −35 mV and had input conductances in the range 1–10 μS. In cells bathed in artificial perienteric fluid, depolarizing steps from a holding potential of −35 mV elicited outward currents at a threshold of − 15 mV. These currents had inwardly directed inflections on the rising phase, suggesting the presence of more than one current. Hyperpolarizing steps did not activate current. Tetraethylammonium (TEA+, 69 mmol l−1) blocked the outward currents and allowed a voltage-dependent inactivating Ca2+ current to be observed. The peak current-voltage relationship was U-shaped with a threshold around −15 mV and peak at +5 mV. The reversal potential of the Ca2+ current was estimated by extrapolation to be +45 mV. The permeability of the voltage-activated outward currents was studied by examining reversal potentials of tail currents. The reversal potentials were linearly dependent on the logarithm of the extracellular potassium concentration if extracellular [K+] was greater than 10 mmol 1−1. The Na+/K+ permeability ratio of the currents was 0.04. Inactivation, seen as a decline following the peak of the K+ current, was produced by maintained depolarization. The recovery from inactivation was complex and could be described by the sum of two exponentials with time constants of 0.67 s and 20.1 s. Steadystate inactivation of the K+ currents was observed at a range of holding potentials. Only a proportion (34%) of the total K+ current was inactivated by holding potentials more positive than −20 mV. Extracellular application of 5 mmol l−1 4-aminopyridine (4-AP) selectively abolished an early fast component of the K+ current (the peak). The 4-AP-sensitive current decayed quickly with a time constant of around 10 ms; a Boltzmann fit to its activation curve had a half-maximal activation voltage of +14 mV and a ‘slope’ of 10.5mV. The 4-AP-resistant current decayed with a time constant of around Is; a Boltzmann fit to its activation curve had a half-maximal activation voltage of +29 mV and a ‘slope’ of 12 mV. Depolarization activates a Ca2+ current and two K+ currents: the K+ currents were separated into lower-threshold, fast-inactivating (Ia-like) and higher-threshold, slowly inactivating (Ik-like) currents.
Fibre Heterogeneity in the Closer and Opener Muscles of Crayfish Walking Legs
Authors: Günzel Dorothee , Galler Stefan , Rathmayer Werner
Published: April 2021

The closer and opener muscles in the third walking legs of the three crayfish Pacifastacus leniusculus, Procambarus clarkii and Astacus leptodactylus are composed of fibres which differ in histochemistry, electrophysiology and morphology. Three major groups of fibres (A, B and C) were distinguished. Group A fibres react weakly to histochemical stains for myofibrillar ATPase (mATPase) activity characteristic of fibres with slow shortening speeds. In the opener muscle, they are innervated by the opener excitor (OE) and the specific opener inhibitor (OI). In the closer muscle, group A fibres are innervated by the common inhibitory neurone (CI) in addition to single (slow closer excitor, SCE) or double excitatory (SCE and fast closer excitor, FCE) innervation. Group A fibres have the largest excitatory junction potentials (EJPs), the longest membrane time constants (τ) and the longest sarcomeres. They are located at the very distal and proximal ends of both muscles. Group B fibres show higher mATPase activity than group A fibres. In the opener muscle, they are innervated by OE and OI; in the closer muscle, they receive double excitatory (SCE and FCE) and CI innervation. Single SCE and OE EJPs are small; those caused by FCE are larger. τ is shorter than in the other two fibre groups. Sarcomere lengths lie between those of group A and C fibres. Group B fibres are found along the entire lengths of both muscles. Group C fibres exhibit the highest mATPase activity (characteristic of fibres with fast shortening velocity) which, in contrast to the ATPase of group B fibres, is not resistant to alkaline preincubation at pH10.05. In the closer, these fibres lack innervation by CI, otherwise the innervation pattern is identical to that of group B fibres. EJP size is similar to that of group B fibres; τ ranges between values for group A and B fibres. Sarcomere lengths are the shortest of all the fibre types. Group C fibres constitute the majority of the fibres in the two muscles and mainly occupy the central regions.
The Effects of Body Size on the Acid–Base and Metabolite Status in the White Muscle of Rainbow Trout Before and After Exhaustive Exercise
Authors: Ferguson Ralph A. , Kieffer James D. , Tufts Bruce L.
Published: April 2021

The effect of body size on the white muscle acid–base and metabolite status was examined in rainbow trout (Oncorhynchus mykiss) ranging in length from 8 to 54cm. Following 5min of exhaustive exercise, white muscle lactate concentration was approximately doubled (approximately 32 μmol g−1) in larger fish than in smaller fish (approximately 16 μmol g−1). Associated with this post-exercise increase in lactate was a nearly parallel increase in the number of metabolic protons produced by larger fish. Larger fish did not possess a greater non-bicarbonate buffering capacity or soluble protein concentration, so their mean muscle intracellular pH (pHi) decreased by approximately 0.70 units compared with a change in mean pHi of about 0.40 units in the smallest fish. The relationship between resting pHi and length was independent of size (mean pHi7.31). Concentrations of muscle energy metabolites were also determined in trout white muscle before and after exercise. Under resting conditions, larger fish possessed a twofold greater concentration of ATP (approximately 7 μmol g−1) than did smaller fish (approximately 3μmol g−1). Similarly, resting values of muscle glycogen range from about 6 μmol g−1 in the smallest fish to as high as 15 μmol g−1 in the largest fish. However, the smaller fish had higher levels (approximately 35 μmol g−1) of phosphocreatine (PCr) than the larger fish (approximately 25 μmol g−1). Following exercise, however, both ATP and glycogen concentrations remained size-dependent and increased with increases in fish length. Levels of PCr were size-independent following exercise. These results demonstrate that body size has an important influence on the acid–base and metabolic status of fish before and after exercise.
Discontinuous Ventilation in a Non-Insect, The Tick Amblyomma Marmoreum (Acari, Ixodidae): Characterization and Metabolic Modulation
Authors: Lighton John R. B. , Fielden Laura J. , Rechav Yigal
Published: April 2021

We examined and quantified the discontinuous ventilation cycle (DVC) characteristics of unfed nymphs and adults, as well as engorged nymphal and engorged diapausing and non-diapausing female adult life-stages, of the African tortoise tick Amblyomma marmoreum (Koch). All engorged stages ventilated continuously, with little evidence of active spiracular control. Unfed nymphs and adults ventilated discontinuously; at low activity and standard metabolic rate (SMR) levels, mean DVC duration was approximately 0.4h in nymphs (mean mass 0.7mg) and 2.8h in female adults (mean mass 70mg). SMR, measured as rate of CO2 production (; 0.064 μl mg−1 h−1 and 0.019 μl mg−1 h−1, respectively), was almost tenfold lower than that estimated for spiders of equivalent mass. In adults, the DVC was modulated to accommodate changing chiefly by changes in DVC frequency. Modulation of other DVC characteristics was bimodal; at low (below the ‘SMR threshold’), burst volumes were large and not correlated with but the rate of CO2 emission during the burst was modulated by Above the SMR threshold, burst volumes were small and tightly correlated with . No fluttering-spiracle phase could be detected, but CO2 bursts were triggered at low volumes above the SMR threshold, suggesting that hypoxia in addition to hypercapnia may initiate the termination of DVCs in the burst phase, rather than initiating the flutter phase as in insects. To explain this bimodal modulation of the DVC by (and hence ) above and below the SMR threshold, we hypothesize that, below the SMR threshold, unfed ixodid ticks – with their very low SMR and large surface area/volume ratio – may obtain significant amounts of O2 by transcuticular or other putative non-spiracular avenues of O2 uptake (larval ticks obtain all their O2 in this way).
Paddlefish buccal flow velocity during ram suspension feeding and ram ventilation
Authors: Sanderson S. Laurie , Cech Joseph J. , Cheer A. Y.
Published: April 2021

A micro-thermistor probe was inserted into the buccal cavity of freely swimming paddlefish to measure flow velocity during ram ventilation, ram suspension feeding and prey processing. Swimming speed was measured from videotapes recorded simultaneously with the buccal flow velocity measurements. Both swimming velocity and buccal flow velocity were significantly higher during suspension feeding than during ram ventilation. As the paddlefish shifted from ventilation to feeding, buccal flow velocity increased to approximately 60 % of the swimming velocity. During prey processing, buccal flow velocity was significantly higher than the swimming velocity, indicating that prey processing involves the generation of suction. The Reynolds number (Re) for flow at the level of the paddlefish gill rakers during feeding is about 30, an order of magnitude lower than the Re calculated previously for pump suspension-feeding blackfish. These data, combined with data available from the literature, indicate that the gill rakers of ram suspension-feeding teleost fishes may operate at a substantially lower Re than the rakers of pump suspension feeders.
Help, there are ‘omics’ in my comparative physiology!
Authors: Torson Alex S. , Dong Yun-wei , Sinclair Brent J.
Published: April 2021

‘Omics’ methods, such as transcriptomics, proteomics, lipidomics or metabolomics, yield simultaneous measurements of many related molecules in a sample. These approaches have opened new opportunities to generate and test hypotheses about the mechanisms underlying biochemical and physiological phenotypes. In this Commentary, we discuss general approaches and considerations for successfully integrating omics into comparative physiology. The choice of omics approach will be guided by the availability of existing resources and the time scale of the process being studied. We discuss the use of whole-organism extracts (common in omics experiments on small invertebrates) because such an approach may mask underlying physiological mechanisms, and we consider the advantages and disadvantages of pooling samples within biological replicates. These methods can bring analytical challenges, so we describe the most easily analyzed omics experimental designs. We address the propensity of omics studies to digress into ‘fishing expeditions’ and show how omics can be used within the hypothetico-deductive framework. With this Commentary, we hope to provide a roadmap that will help newcomers approach omics in comparative physiology while avoiding some of the potential pitfalls, which include ambiguous experiments, long lists of candidate molecules and vague conclusions.
The Use of Heart Rate to Estimate Oxygen Consumption of Free-Ranging Black-Browed Albatrosses Diomedea Melanophrys
Authors: Bevan R. M. , Woakes A. J. , Butler P. J. , Boyd I. L.
Published: April 2021

Heart rates (fH) and rates of oxygen consumption were measured in eight black-browed albatrosses (Diomedea melanophrys) when walking on a treadmill, with the aim of using fH to predict in free-ranging albatrosses. The resulting relationship between the variables was: (ml min−1) = [0.0157fH (beats min−1)]1.60, r2=0.80, P<0.001. In addition to the calibration procedure, six of the albatrosses were injected with doubly labelled water (DLW), and fH and were monitored continuously over a 3 day period while the birds were held in a respirometer. During the 3 day period, the birds were walked for up to 3–4 h day−1 in bouts lasting approximately 0.5 h. The heart rate data were used to estimate the metabolic rates of these birds using the above regression. Estimates of metabolic rate derived from fH, DLW and respirometry did not differ (ANOVA; P=0.94), primarily because of the variance between individual birds. There was also no significant difference between the different estimates obtained from the different equations used to calculate energy expenditure from the DLW technique (ANOVA; P=0.95). Mean estimates of from fH under active and inactive conditions differed from measured values of by -5.9% and -1.7% respectively. In addition, the estimates of from fH at different walking speeds did not differ significantly from the measured values. It appears that, in the black-browed albatross, fH is as good a predictor of the mean metabolic rate of free-ranging birds as DLW or time–energy budgets combined with either respirometry or DLW. However, the method should be applied to as many individuals and as many instances of a particular behaviour as possible. The heart rate technique offers potential for much more detailed analyses of the daily energy budgets of these birds, and over much longer periods, than has previously been possible.
Sexually Dimorphic Spatial Learning in Meadow Voles Microtus Pennsylvanicus and Deer Mice Peromyscus Maniculatus
Authors: Galea Liisa A. M. , Kavaliers Martin , Ossenkopp Klaus-Peter
Published: April 2021

A number of studies examining developmental, neural and hormonal aspects of sexually dimorphic spatial learning (Morris water-maze) in meadow voles (Microtus pennsylvanicus) and deer mice (Peromyscus maniculatus) are described. We found that, in adult deer mice, female spatial performance decreased during the breeding season relative to the non-breeding season, whereas the reverse pattern was observed in male performance. There was a sex difference favouring males in spatial learning during the breeding season, but not during the non-breeding season. In adult meadow voles, females with low levels of oestradiol and males performed better in the water-maze than females with high levels of oestradiol. Postweaning voles (20 and 25 days after birth) acquired the water-maze task more quickly than preweaning voles (day 10). No sex difference in water-maze performance was evident at any of these juvenile ages. When these same voles were tested again as adults to investigate retention and re-acquisition of the water-maze, both males and females from male-biased litters re-acquired the task better than males and females from female-biased litters. Together, the results of these studies indicate that sexually dimorphic spatial ability is dependent on the organizational (in utero) and activational effects of gonadal hormones. These studies provide the first demonstration of the influence of natural changes in reproductive status on spatial learning of deer mice and meadow voles. The results also demonstrate that spatial performance of males and females is differentially affected by changes in reproductive status and that group differences in the laboratory are associated with group differences in space utilization in the wild. These findings help to clarify previous apparently contradictory findings about sex differences in spatial ability.
The Mechanics Of Swallowing And The Muscular Control Of Diverse Behaviours in Gopher Snakes
Authors: Moon Brad R.
Published: April 2021

Snakes are excellent subjects for studying functional versatility and potential constraints because their movements are constrained to vertebral bending and twisting. In many snakes, swallowing is a kind of inside-out locomotion. During swallowing, vertebral bends push food from the jaws along a substantial length of the body to the stomach. In gopher snakes (Pituophis melanoleucus) and king snakes (Lampropeltis getula), swallowing often begins with lateral bending of the head and neck as the jaws advance unilaterally over the prey. Axial movement then shifts to accordion-like, concertina bending as the prey enters the oesophagus. Once the prey is completely engulfed, concertina bending shifts to undulatory bending that pushes the prey to the stomach. The shift from concertina to undulatory bending reflects a shift from pulling the prey into the throat (or advancing the mouth over the prey) to pushing it along the oesophagus towards the stomach. Undulatory kinematics and muscular activity patterns are similar in swallowing and undulatory locomotion. However, the distinct mechanical demands of internal versus external force exertion result in different duty factors of muscle activity. Feeding and locomotor movements are thus integral functions of the snake axial system.
Brainstem lateral line responses to sinusoidal wave stimuli in still and running water
Authors: Kröther Sophia , Mogdans Joachim , Bleckmann Horst
Published: April 2021

The fish lateral line consists of superficial and canal neuromasts. In still water, afferent fibers from both types of neuromast respond equally well to a sinusoidally vibrating sphere. In running water, responses to a vibrating sphere of fibers innervating superficial neuromasts are masked. In contrast,responses of fibers innervating canal neuromasts are barely altered. It is not known whether this functional subdivision of the peripheral lateral line is maintained in the brain. We studied the effect of running water on the responses to a 50 Hz vibrating sphere of single units in the medial octavolateralis nucleus (MON) in goldfish Carassius auratus. The MON is the first site of central processing of lateral line information. Three types of units were distinguished. Type I units (N=27) were flow-sensitive; their ongoing discharge rates either increased or decreased in running water, and as a consequence, responses of these units to the vibrating sphere were masked in running water. Type II units (N=7) were not flow-sensitive; their ongoing discharge rates were comparable in still and running water, so their responses to the vibrating sphere were not masked in running water. Type III units (N=7) were also not flow-sensitive, but their responses to the vibrating sphere were nevertheless masked in running water. Although interactions between the superficial and canal neuromast system cannot be ruled out, our data indicate that the functional subdivision of the lateral line periphery is maintained to a large degree at the level of the medial octavolateralis nucleus.
Squeaking with a sliding joint: mechanics and motor control of sound production in palinurid lobsters
Authors: Patek Sheila N.
Published: April 2021

The origin of arthropod sound-producing morphology typically involves modification of two translating body surfaces, such as the legs and thorax. In an unusual structural rearrangement, I show that one lineage of palinurid lobsters lost an antennal joint articulation, which transformed this joint from moving with one degree of freedom into a sliding joint with multiple degrees of freedom. With this sliding joint, `stick-and-slip' sounds are produced by rubbing the base of each antenna against the antennular plate. To understand the musculo-skeletal changes that occurred during the origin and evolutionary variation of this sound-producing mechanism, I examined joint morphology and antennal muscle anatomy across sound-producing and non-sound-producing palinurids. Plectrum movement and antennal muscle activity were measured in a sound-producing species, Panulirus argus. The promotor muscle pulls the plectrum over the file during sound-producing and non-sound-producing movements; a higher intensity of muscle activity is associated with sound production. The promotor muscle is larger and attaches more medially in sound-producing palinurids than in non-sound producers. In Panulirus argus, each shingle on the file has an additional ridge; in Palinurus elephas, the shingle surfaces are smooth. These differences in shingle surface features suggest variation in the stick-and-slip properties of the system. Translational motion permitted by the sliding joint is necessary for sound production; hence, the construction of a sliding joint is a key modification in the origin of this sound-producing mechanism.
A kinematic model of swallowing inAplysia californicabased on radula/odontophore kinematics andin vivomagnetic resonance images
Authors: Neustadter David M. , Drushel Richard F. , Crago Patrick E. , Adams Benjamin W. , Chiel Hillel J.
Published: April 2021

A kinematic model of the buccal mass of Aplysia californica during swallowing has been developed that incorporates the kinematics of the odontophore, the muscular structure that underlies the pincer-like grasping structure, the radula. The model is based on real-time magnetic resonance images (MRIs) of the mid-sagittal cross section of the buccal mass during swallowing. Using kinematic relationships derived from isolated odontophores induced to perform feeding-like movements, the model generates predictions about movement of the buccal mass in the medio-lateral dimension during the feeding cycle that are well-matched to corresponding coronal MRIs of the buccal mass during swallowing. The model successfully reproduces changes in the lengths of the intrinsic (I) buccal muscles I2 and I3 measured experimentally. The model predicts changes in the length of the radular opener muscle I7 throughout the swallowing cycle, generates hypotheses about the muscular basis of radular opening prior to the onset of forward rotation during swallowing and suggests possible context-dependent functions for the I7 muscle, the radular stalk and the I5 (ARC) muscle during radular opening and closing.
A Critical Study of Techniques for Determining the Cytological Position of Alkaline Phosphatase
Authors: Danielli J. F.
Published: April 2021

It has been proved that the technique of Takamatsu and of Gömorri indicates the cytological sites of alkaline phosphatase activity. The critical time limits for the various operations in the technique have been determined. Several alternative techniques are given for demonstrating phosphatase activity on the cytological level. A selection of fixatives is given which do not produce severe destruction of alkaline phosphatase activity. It has been shown that alkaline phosphatase in fixed preparations is found in sites which are those in which it occurs under physiological conditions. It is suggested that the function of the phosphatase found in the brush borders of the proximal tubules of the kidney is to hydrolyse phosphate esters in the glomerular filtrate, and thereby permit the reabsorption of the component molecules by tubular processes.
The Effects of Low Atmospheric Pressure on the Fertility of Male Rabbits
Authors: Walton Arthur , Uruski W.
Published: April 2021

Low atmospheric pressure has a detrimental effect upon the fertility of male rabbits. Changes can be detected in semen samples and by histological examination of the testis. The changes induced in the testis take a chronic course but are completely reversible on returning the animal to normal atmospheric pressures.
The Nature of the Action Potentials of Crustacean Muscles
Authors: Wiersma C. A. G. , Wright Ernest B.
Published: April 2021

An investigation has been made of the action potentials of the muscles of the crayfish, Cambarus clarkii. It was found that the polarity of these potentials was in many instances the reverse of that expected. It is shown that ‘positive’ potentials cannot be explained by injury to the active tissue, by the complex structure of the muscles, or by the direction of the muscle fibres. Using muscles in which all extraneous connexions could be rigorously avoided, the muscle action potentials were invariably found to be negative. Direct evidence is presented for the local non-conducted nature of the crustacean muscle action potentials. An hypothesis is offered to explain the monophasicity and polarity of these action potentials on the basis of multiple unilateral innervation of the muscle fibres.
Spontaneous Rhythmical Impedance Changes in the Egg of the Trout. II
Authors: Rothschild Lord
Published: April 2021

The spontaneous rhythmical impedance changes that occur in fertilized and unfertilized eggs of the rainbow trout after about 7 hr. immersion in tap water have been analysed. They are found to be almost entirely capacitative and correspond to a change of between 5 and 10 % when measured at a frequency of about 1.0 kc. The possibility of any associated resistance change being virtually unobservable is discussed. These changes, which have not so far been recorded in other living material, are compared with the impedance changes that occur in nerve cells and Nitella.
Studies on Sterility and Prenatal Mortality in Wild Rabbits
Authors: Allen Patricia , Rogers Brambell F. W. , Mills Ivor H.
Published: April 2021

The technical problems underlying the estimation and analysis of the total prenatal mortality in a mammal are reviewed, with particular reference to the rabbit. The material consisted of 7137 wild rabbits, of which 5089 were females. These comprise eleven series, according to the year, locality and treatment, particulars of which are given. The experimental error in counts of corpora lutea was investigated and the technique critically examined. The changes in size of the corpus luteum during pregnancy were measured and a growth curve constructed. The mean number of corpora lutea in a litter, as determined from macroscopic counts, was found to be significantly lower at the beginning and end of pregnancy than in the middle. If this is due to omissions in the counts it represents a maximum error of 6.8% of corpora lutea. Microscopic counts of the corpora lutea in freehand sections of 180 pairs of ovaries of pregnant animals were made as a control. These revealed a total error in the original counts of 6.4% of the corpora lutea, affecting 25.6% of the litters, but this was distributed evenly throughout gestation. Corpora lutea atretica formed from unruptured follicles are present in 16% of the pairs of ovaries, and comprise less than 2% of all corpora lutea. They are formed at the same time as the normal corpora lutea, and there is no evidence that any are formed subsequently during pregnancy in the rabbit. It is estimated that 0.23% of the follicles which ovulate produce two embryos through the liberation of two ova. Transperitoneal migration of 0.37% of ova, affecting 2% of the litters, was found to occur. The probability of migration either from left to right or from right to left appeared to be equal. Significant changes in the mean number of implantation sites in the uteri counted at successive stages of pregnancy were observed, and particularly a decline at the end of gestation. They are of the same order as those in the mean number of corpora lutea, which they will tend to compensate so far as estimates of loss of ova before implantation are concerned. It is by no means clear that these are due to experimental error in the counts. Estimates of the loss of embryos before implantation are based on the difference between the number of corpora lutea in the ovaries and of implantation sites in the uteri, and estimates of the loss after implantation on the difference between the number of implantation sites and of developing embryos. No significant relation has been found between the loss before and after implantation respectively, and it is concluded that the loss suffered after implantation is distributed independently of that which occurs before implantation.
Visual and movement memories steer foraging bumblebees along habitual routes
Authors: Bertrand Olivier J. N. , Doussot Charlotte , Siesenop Tim , Ravi Sridhar , Egelhaaf Martin
Published: April 2021

One persistent question in animal navigation is how animals follow habitual routes between their home and a food source. Our current understanding of insect navigation suggests an interplay between visual memories, collision avoidance and path integration, the continuous integration of distance and direction travelled. However, these behavioural modules have to be continuously updated with instantaneous visual information. In order to alleviate this need, the insect could learn and replicate habitual movements (‘movement memories’) around objects (e.g. a bent trajectory around an object) to reach its destination. We investigated whether bumblebees, Bombus terrestris, learn and use movement memories en route to their home. Using a novel experimental paradigm, we habituated bumblebees to establish a habitual route in a flight tunnel containing ‘invisible’ obstacles. We then confronted them with conflicting cues leading to different choice directions depending on whether they rely on movement or visual memories. The results suggest that they use movement memories to navigate, but also rely on visual memories to solve conflicting situations. We investigated whether the observed behaviour was due to other guidance systems, such as path integration or optic flow-based flight control, and found that neither of these systems was sufficient to explain the behaviour.
Dimorphic cocoons of the robin moth, Hyalophora cecropia, reflect the existence of two distinct architectural syndromes
Authors: Parlin Adam F. , Guerra Patrick A.
Published: April 2021

The architectural design of animal structures forms part of an individual's extended phenotype that can be subjected to strong selection pressures. We examined cocoon architectural dimorphism in robin moths (Hyalophora cecropia), which construct multilayered silk-woven cocoons that possess either a ‘baggy’ or ‘compact’ morphology. These dimorphic cocoons reflect extended phenotypes that can enable survival during a critical developmental period (pupal stage to adult emergence), with cocoons occurring either sympatrically or as monomorphic groups across different climatic regions in North America. We hypothesized that cocoon dimorphism is related to the cocoon's role as a mediating barrier for moisture. We predicted that the macro- and micro-architectural differences between the cocoon morphs would be consistent with this function. We compared the cocoon morphs in terms of their orientation when spun under natural field conditions, examined how these orientations affected cocoon water absorption under simulated rain trials, and performed material surface tests to compare the hydrophobicity of cocoons. We found that compact cocoons had traits that increased water resistance, as they had significantly greater hydrophobicity than baggy cocoons, because they absorbed less water and released water vapor faster. In contrast, the increased water absorptiveness of baggy cocoons can allow for greater moisture retention, a function related to the prevention of desiccation. Our study suggests that cocoon dimorphism in robin moths reflects distinct architectural syndromes, in which cocoons are spun to optimize either water resistance or retention. These different functions are consistent with strategies that act to respond to uncertain external environmental conditions that an individual might encounter during development.
The Absorption of Volatile Fatty Acids from the Rumen
Authors: Gray F. V.
Published: April 2021

The fermentation of carbohydrates in the rumen of sheep is known to lead to the formation of large amounts of the lower fatty acids. The important part that these acids assume in the metabolism of ruminants has been remarked upon (Marston, 1939, 1946). While it is believed that acetic, propionic and butyric acids are the main fatty acid products of the fermentation, there is no certain knowledge of the proportions and quantities in which they are formed.
The Digestion of Cellulose by Sheep
Authors: Gray F. V.
Published: April 2021

Until recently, information of the extent to which cellulose is digested in the alimentary tract of the ruminant was available only indirectly through studies of the fate of that indefinite and variable complex mixture of cellulose, hemicellulose and encrusting substances which is conventionally referred to as ‘crude fibre’. This, in the past, has been taken as a measure of the less readily digested part of the carbohydrates of plants, in contrast to the ‘N-free extractives’ which represent the more soluble and therefore more readily digestible portion.
Preliminary Studies on the Nutritional Requirements of the Bedbug (Cimex Lectularius L.) and the Tick Ornithodorus Moubata Murray
Authors: De Meillon Botha , Golberg Leon
Published: April 2021

The nutritional requirements of insects have been the object of much investigation in recent years. These studies have been largely confined to holometabolous insects which feed on a variety of unsterile food in nature. By working under aseptic conditions in the laboratory the exact requirements of the insects concerned may be assessed. The original object of these investigations was to determine the nutritional requirements of a hemimetabolous insect, Cimex lectularius, which during its whole life takes only sterile blood as a source of food. For this purpose it became necessary to feed the insects in vitro through a membrane so that the medium presented to them could be varied at will. It was also intended to induce changes in the blood taken by the bugs in vivo, i.e. in the living animal on which they were fed.
The relationship between myonuclear number and protein synthesis in individual rat skeletal muscle fibres
Authors: Ato Satoru , Ogasawara Riki
Published: April 2021

Skeletal muscle has numerous nuclei within a cell. The nucleus is considered as the central organelle for muscle protein synthesis (MPS). However, it is unclear whether myonuclear number is associated with MPS capacity within the individual muscle fibres. Therefore, the purpose of the present study was to reveal the relationship between myonuclear number per unit muscle fibre length and MPS under basal and conditions of elevated MPS by high-intensity muscle contraction (HiMC) using an in vivo nascent protein labelling technique (SUnSET) in rodents. We found that myonuclear number was positively correlated with MPS in individual muscle fibres in the basal condition. Similarly, ribosomal protein S6 (rpS6) content, which is a rough estimate of ribosome content, was positively correlated with MPS. However, myonuclear number was not associated with rpS6 content. In contrast to the basal condition, when MPS was increased by acute HiMC, no correlation was observed between myonuclear number and MPS, but the association between rpS6 and MPS was maintained. Importantly, these observations indicate that the number of nuclei in individual myofibers is related only to MPS at rest. However, the ribosome content in individual fibres is related to MPS of individual myofibers both at rest and following HiMC.
The Propulsive Powers of Blue and Fin Whales
Authors: Kermack K. A.
Published: April 2021

Gray (1936), discussing the swimming of the dolphin and porpoise, demonstrates that, for the horse-power developed per lb. of muscle to agree with that expected by analogy with man and the dog, the flow past the body of the animal must be free from turbulence. An attempt is made here to repeat his calculations for Blue and Fin whales (Balaenoptera musculus and B. physalus). This arose out of observations made on these whales by the writer during a recent visit to the Antarctic on the floating factory Empire Victory.
The Composition of the Body Fat of Small Green Chironomids
Authors: Grindley D. N.
Published: April 2021

During the winter months, the banks of the Nile near Khartoum abound with small non-biting midges, Tanytarsus lewisi Freeman (Diptera, Chironomidae), which emerge from the surface of the river shortly after sunset and fly around in the immediate neighbourhood for about hr. In an endeavour to relate variations in the incidence of these insects (‘nimitti’) to seasonal and climatic factors, collections were made every evening for some considerable time; the insects trapped for this purpose provided the source of material used for the experimental work described below.
Hormone Balance and the Control of Metamorphosis in Rhodnius Prolixus (Hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

The body cells of the developing insect carry the potentialities for both larval and imaginal differentiation. During larval life imaginai differentiation is suppressed because in the presence of the juvenile hormone (sometimes referred to as the ‘inhibitory hormone’), secreted by the corpus allatum, the intracellular system which leads to the formation of larval structures takes precedence over the system which leads to the formation of adult structures (Wigglesworth, 1940).
Transpiration Through the Cuticles of Some Aquatic Insects
Authors: Holdgate M. W.
Published: April 2021

Measurement of the rate of water loss in dry air from ten species of aquatic insects, representing six orders, has shown that the cuticles are in all cases more permeable than are those of typical terrestrial species. There is, however, a wide range of permeability within the group. The rate of water loss increases exponentially with temperature. There is no ‘critical temperature’. The steepness of the exponential relating transpiration and temperature is greatest in the least permeable examples. Chloroform treatment produces a marked increase in water loss, but abrasion by mineral dusts has very little effect. Adult specimens of ‘Notonecta obliqua’ immersed in distilled water gain weight at a rate which suggests that the cuticle is comparatively permeable under these conditions also. The rate of water uptake is increased by chloroform treatment. The results support the general theory advanced by Holdgate and Seal (1955), but no sound interpretation of the structural basis of cuticular permeability can yet be advanced.
On the Light Response of the Chromatophore of the Sea-Urchin, Diadema Setosum (Leske)
Authors: Yoshida Masao
Published: April 2021

The responses of chromatophores to Eght stimuli have been reported in various kinds of animals. In almost all cases, the stimuli have been regarded as not affecting the chromatophore directly, but through nervous or hormonal mediation. Little is understood about chromatophore behaviour as a primary response to light.
Endothermy and Ectothermy in Mice at—3°C
Authors: Barnett S. A.
Published: April 2021

A study is being made of the effects on laboratory mice (Mus musculus L.) of breeding at an environmental temperature of—2 to—4° C. It has been found that both A (white) and C57 (black) mice, rigorously inbred, can be maintained indefinitely at this temperature, given cotton-wool for nesting (Barnett & Manly, 1954).
On the Relative Importance of Body Weight and Surface Area Measurements For the Prediction of the Level of Oxygen Consumption of Ligia Oceanica L. and Prepupae of Drosophila Melanogaster Meig
Authors: Ellenby C. , Evans D. A.
Published: April 2021

Previous investigations with Ligia oceanica and prepupae of Drosophila melanogaster (Ellenby, 1951, 1953) have suggested that it may be possible to predict the level of oxygen consumption more precisely from a measurement of surface area (Drosophila) or body length (Ligia) than from body weight, in spite of the greater accuracy of the latter measurement. The point is now examined more closely by applying the technique of multiple regression to the original data. For Ligia, it is shown that the suggestion cannot be upheld, for the level of oxygen consumption can be predicted with greater accuracy from body weight than from a function of body length. On the other hand, for diploid male and female prepupae of Drosophila, it is shown that surface area does, in fact, give a better prediction than body weight. In the case of triploid female prepupae, however, body weight is superior. It is shown that there are no grounds for believing that the measurements of surface area were less accurate in the case of the triploids; for this and other reasons, it is suggested that the difference between diploids and triploids may be due to a fundamental difference between the two sorts of prepupae.
Metachronism and Frequency of Beat in the Peristomial Cilia of Stentor
Authors: Sleigh M. A.
Published: April 2021

A stroboscopic method was used to determine the frequency of beat of the peristomial cilia of Stentor polymorphus (Ehrbg.). The metachronal wave-length was measured from photographs. These two values were used to calculate the rate of propagation of the metachronal wave. The Arrhenius temperature characteristics for frequency and for wave velocity were calculated for the temperature range from o to 25° C. The average values found, 11,350 and 7520, were significantly different for the two factors. An increase in the viscosity of the medium by addition of methyl cellulose caused a decrease in frequency, but no significant change in wave velocity. The presence of magnesium chloride in low concentrations caused an increase in frequency, but no significant change in wave velocity. Aluminium chloride caused similar increases in frequency at lower concentrations than magnesium chloride. The drug digitoxin had different quantitative and qualitative effects on the frequency and on the wave velocity. Small increases in frequency occurred over the concentration range in which large increases in wave velocity were recorded. The wave velocity increase reached a maximum at about 0.4 mg./l. of digitoxin and was some six times as great as the frequency increase at this concentration. It is concluded that the mechanical process involved in ciliary activity functions independently of the co-ordination process. A combination of these two factors determines the magnitude of the metachronal wave-length.
Some Aspects of the Respiration of Six Species of Fish From Uganda
Authors: Fish G. R.
Published: April 2021

The present study is an attempt to correlate ecological data with certain aspects of the respiration of six species of fish typical of local waters. The species of fish examined were: