bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Sterility and Prenatal Mortality in Wild Rabbits
Authors: Allen Patricia , Rogers Brambell F. W. , Mills Ivor H. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTA 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

ABSTRACT
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

ABSTRACT
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.
Environmental Factors Influencing the Induction and Termination of Diapause in the Emperor Dragonfly, Anax Imperator Leach (Odonata: Aeshnidae)
Authors: Corbet Philip S. 
Published: April 2021

ABSTRACT
Preliminary experiments have been conducted to determine the environmental factors influencing the induction and termination of diapause in the Emperor Dragonfly, Anax imperator Leach. A facultative diapause is located in the final larval instar and takes the form of an interruption of morphogenesis such that, at about 230 C., metamorphosis does not occur until some 105 days after ecdysis. In non-diapause larvae this period is about 30 days. Feeding continues during diapause development. Diapause appears to be determined in the first few days of the final instar. It can be induced by decreasing photoperiods, irrespective of the lengths of day involved, and alsoby a regime of unchanging photoperiods of a length corresponding to 31 July. Diapause can be prevented by exposure to an increase in photoperiod immediately after ecdysis. This may take the form of a single large increase (of more than 20 min.), or of successive small increments such as occur naturally in March and April. It is possible that under unnaturally long photoperiods larvae do not respond normally to regular increments. Ecdysis to the final instar appears to be stimulated by photoperiods of slightly more than equinoctial length. This tends to localize the sensitive stage to seasons when changes in day length are most pronounced. A previous exposure to winter temperatures in the penultimate instar is not necessary for diapause to be averted in spring. It is likely that diapause development proceeds most rapidly at a temperature near io° C. Negligible diapause development had occured after exposure to 6° C. for 12 weeks, although variation in the period necessary for its completion was then reduced. Diapause development has already been completed in nature by February. After this, metamorphosis occurs as a simple response to adequate temperature and food. It cannot take place when the average temperature is below n° C. Metamorphosis is not prevented by a regime of decreasing photoperiods.
The Water Relations of Earthworms
Authors: Roots Betty I. 
Published: April 2021

ABSTRACT
The water content of Lumbricus terrestris, after keeping on moist filter-paper for 3 or 4 days, is 84-8 % of its body weight. That of Allolobophora chlorotica is 80 % of its body weight. Both species can survive a loss of 60 % of the body weight, but not much more. Earthworms of the species A. chlorotica, A. terrestris f. longa, Dendrobaena subrubicunda, L. rubellus and L. terrestris are all able to survive from 31 to 50 weeks in soil totally submerged beneath aerated water. The same species, and A. caliginosa can survive for 72-137 days in aerated tap water without food. Garden specimens of A. chlorotica make U-shaped burrows in soil beneath water. They do not irrigate either the burrows or glass tubes. Egg-cocoons of A. chlorotica, taken from culture pots of soil, will hatch under water and the young worms will feed and grow though totally immersed. D. subrubicunda, L. rubellus and L. terrestris avoid immersion in water when allowed a choice between water-saturated and moist but air-filled soil. When A. caligmosa, A. chlorotica and A. terrestris f. longa are allowed a similar choice, a small proportion of the population is always found in the water-filled soil. Enforced submergence before being allowed a choice of environment does not affect the behaviour of L. rubellus, i.e. water is still avoided. Similar treatment of A. chlorotica and L. terrestris results in a more frequent choice of water. It is unnecessary to postulate that the individuals of A. chlorotica occurring in Lake Windermere constitute a ‘biological race’. The avoiding reaction of earthworms to immersion may explain why they leave the soil after heavy rain.
The Quantitative Nutritional Requirements ofDrosophila Melanogaster
Authors: Sang James H. 
Published: April 2021

ABSTRACTA technique for sterilizing large numbers of Drosophila eggs is described. This gives about 95 % successful cultures. Using this method, dose-response curves have been obtained for all the main dietary constituents under conditions in which interactions between them are likely to be of little significance. Responses to the following are detailed : casein, fructose, cholesterol, lecithin, RNA, thiamine, riboflavine, nicotinic acid, pantothenic acid, biotin, pyridoxine, folic acid, choline and a water-soluble fraction of yeast which improves growth. Other substances which have been included in Drosophila media are shown to have no value for the inbred strain of flies tested. It is also shown that only K, P, Mg and Na salts need to be included in the food. On the basis of these findings an optimal medium is formulated which allows larval development to be completed in about 4 4 days. This compares with 4-1 days when the same strain is reared on an optimal supply of killed yeast. The minimal nutritional requirements of Drosophila larvae are shown to be considerably less than those of other aseptically cultured insects and, as far as the vitamins are concerned, only broadly related to the amounts found in yeast. The possible reasons for this are discussed.
The Epicuticular Wax Layers of the Pupa ofTenebrio MolitorL.
Authors: Holdgate M. W. , Seal M. 
Published: April 2021

ABSTRACTA study has been made of the structure of the outer epicuticle of the pupa of Tenebrio molitor (Coleoptera), particular attention being paid to a surface wax layer. In this study two electron optical techniques, reflexion electron microscopy and electron diffraction, have been used. At moulting, the Tenebrio pupa has a wax layer exposed on its surface. The nature of this wax has been investigated by electron diffraction. Most of the wax melts at about 40° C, and there is no indication of a ‘transition’ below this temperature. A cement layer is secreted soon after moulting. Later, a surface wax layer, made up of numerous fine filaments, appears. These filaments melt at about 80° C, and are removed by wax solvents. Material obtained from chloroform washings of mature pupae shows a wide range of melting-points, but an investigation by electron diffraction provides no evidence for a ‘transition’. The validity of the concept of a ‘critical temperature’ in the water-loss curves is discussed. The experimental data can in every case be fitted by smooth and continuous curves. It is, therefore, suggested that any physical changes (e.g. melting) which may occur in the epicuticular waxes, take place over a range of temperatures rather than at a definite ‘critical temperature’. The water-loss curves for Tenebrio pupae change shape as the outer epicuticle develops. Mature pupae show good waterproofing to a higher temperature than do young pupae. This change in the curves is associated with the secretion of the cement layer. Parallel studies have been carried out on Rhodnius nymphs and similar results obtained.