bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pigeon Homing: Observations, Experiments and Confusions
Authors: Walcott Charles 
Published: April 2021

ABSTRACT
Homing pigeons can return from distant, unfamiliar release points. Experienced pigeons can do so even if they are transported anesthetized and deprived of outward journey information. Airplane tracking has shown that they make relatively straight tracks on their homeward journey; therefore, pigeons must have some way of determining the home direction at the release site. Manipulating the pigeon’s internal clock causes predictable deviations in their flight direction relative to home. When the sun is not visible, such clock shifts have no effect. This result implies a two-step system: the determination of the home direction and the use of a sun compass to fly in that direction. When pigeons cannot see the sun they use a magnetic compass. The use of compass cues to select and maintain a direction of flight is well understood compared with the uncertainty surrounding the nature of the cues used to determine the home direction when pigeons are released at an unfamiliar site. Because they generally home successfully from any direction and distance from the loft, without requiring information gathered on the outward journey, it seems likely that they use some form of coordinate system. Presumably, a displaced pigeon compares the values of some factor at the release site with its remembered value at the home loft. This factor might be olfactory, it might be some feature of the earth’s magnetic field or it might be something else. There is some evidence that pigeons may use several cues and that pigeons raised in different lofts under different environmental conditions may prefer to use one cue over another. I believe that it is this flexible use of multiple cues that has led to so much confusion in experiments on pigeon homing.
Computations on Metric Maps in Mammals: Getting Oriented and Choosing a Multi-Destination Route
Authors: Gallistel C. R. , Cramer Audrey E. 
Published: April 2021

ABSTRACT
The capacity to construct a cognitive map is hypothesized to rest on two foundations: (1) dead reckoning (path integration); (2) the perception of the direction and distance of terrain features relative to the animal. A map may be constructed by combining these two sources of positional information, with the result that the positions of all terrain features are represented in the coordinate framework used for dead reckoning. When animals need to become reoriented in a mapped space, results from rats and human toddlers indicate that they focus exclusively on the shape of the perceived environment, ignoring non-geometric features such as surface colors. As a result, in a rectangular space, they are misoriented half the time even when the two ends of the space differ strikingly in their appearance. In searching for a hidden object after becoming reoriented, both kinds of subjects search on the basis of the object’s mapped position in the space rather than on the basis of its relationship to a goal sign (e.g. a distinctive container or nearby marker), even though they have demonstrably noted the relationship between the goal and the goal sign. When choosing a multi-destination foraging route, vervet monkeys look at least three destinations ahead, even though they are only capable of keeping a maximum of six destinations in mind at once.
Do Animals Have Cognitive Maps?
Authors: Bennett Andrew T. D. 
Published: April 2021

ABSTRACT
Drawing on studies of humans, rodents, birds and arthropods, I show that ‘cognitive maps’ have been used to describe a wide variety of spatial concepts. There are, however, two main definitions. One, sensu Tolman, O’Keefe and Nadel, is that a cognitive map is a powerful memory of landmarks which allows novel short-cutting to occur. The other, sensu Gallistel, is that a cognitive map is any representation of space held by an animal. Other definitions with quite different meanings are also summarised. I argue that no animal has been conclusively shown to have a cognitive map, sensu Tolman, O’Keefe and Nadel, because simpler explanations of the crucial novel short-cutting results are invariably possible. Owing to the repeated inability of experimenters to eliminate these simpler explanations over at least 15 years, and the confusion caused by the numerous contradictory definitions of a cognitive map, I argue that the cognitive map is no longer a useful hypothesis for elucidating the spatial behaviour of animals and that use of the term should be avoided.
Genetic Basis, Mode of Inheritance and Evolutionary Changes of Migratory Directions in Palearctic Warblers (Aves: Sylviidae)
Authors: Helbig A. J. 
Published: April 2021

ABSTRACT
The genetic basis, mode of inheritance and recent evolutionary changes of migratory directions in birds are discussed on the basis of published and new experimental evidence. Displacement experiments with wild-caught migrants and orientation tests with hand-reared passerines illustrate that inexperienced young birds possess genetic information about the direction and approximate distance of migration, but not about the geographic location of the winter quarters. Hand-raised blackcaps Sylvia atricapilla from east and west of the Central European migratory divide, when tested under identical conditions, exibited population-specific migratory directions in orientation cages. Cross-breeding of birds from these two populations demonstrated an intermediate mode of inheritance of this behavioural character. New data on the orientation of an F2 generation suggest that the directional information is encoded by only a few major genes. Migratory adaptations may have evolved recently, in some cases rapidly, as is illustrated by the establishment of a new migration route of central European blackcaps to winter quarters in the British Isles. This new route is shown (in a captive breeding experiment) to be based on a novel, genetically programmed westnorthwesterly migratory direction. It must have spread from almost zero to 7–11 % frequency in parts of central Europe within only three decades. The novel direction is also inherited phenotypically intermediately; its rapid evolution may be mediated by assortative mating based on differential arrival times at the breeding grounds. The evolutionary flexibility of migratory adaptations is discussed in relation to changes in the environment, both natural and accelerated by man.
Pinpointing ‘Isla Meta’: the Case of Sea Turtles and Albatrosses
Authors: Papi F. , Luschi P. 
Published: April 2021

ABSTRACT
Satellite tracking has recently shown that the very long open-sea journeys of sea turtles and albatrosses share several features, in spite of the different physiological and environmental constraints to which turtles and birds are subjected. The reviews of data obtained by tracking migration and feeding routes show that both sea turtles and albatrosses are able (i) to pinpoint small, isolated targets by following straight courses, (ii) to continue on a bearing at night even when the moon is not visible, (iii) to compensate for wind or current drift and (iv) to return home after experimental, long-distance displacements. Sea turtles and albatrosses seem to rely on a position-fixing capacity which cannot be explained by known navigational mechanisms but might be shared by other animals that display similar feats of open-sea guidance. Future research will further benefit from satellite telemetry and other new techniques applied to experimental investigations.
Studies of Wireworm Populations
Authors: Salt George , Hollick F. S. J. 
Published: April 2021

ABSTRACT
Twenty stations were established in a grass field of 8 acres, and twenty-nine soil samples were examined from each station in the course of 213 years. Wireworms (Agriotes sputator) were distributed among the twenty stations in a non-random manner. In this field, the wireworm distribution was correlated to a highly significant degree with nine factors (loss on ignition, organic carbon, nitrogen, Lolium, Agrostis, Chilopoda, staphylinid larvae, ants and Nematocera) and to a significant degree with three factors (altitude, pH of the soil and Diplopoda). Among these factors, three (the organic content of the soil as measured by loss on ignition, the prevalence of the grass Lolium, and the numbers of staphylinid larvae) were found by analysis to be most significantly correlated with the wireworm distribution. Sixteen stations were set up in a grass plot of 14 acre, and twenty-one soil samples were examined from each station during a period of 3 years. The distribution of wireworms at these stations was markedly non-random throughout the sampling period, some stations being consistently three or four times as heavily infested as others only 5 yd, away. Within this plot the distribution of wireworms was correlated to a highly significant degree with altitude, depth of loam and amount of soil moisture at 3 and at 9 in. depth. It was significantly correlated with the lime content of the soil. Ranunculus was prevalent on an area of low wireworm infestation. Among the factors studied in this plot, the amount of soil moisture at 3 in. depth was most important. It was negatively correlated with the distribution of wireworms. Within the plot, stations having high wireworm populations were infested almost exclusively by Agriotes sputator; those having low wireworm populations were infested about equally by A. sputator and A. ‘obscurus-lineatus’. Four square-yard samples were examined, each in eighty-one quadrats 4 in. square. Within each square yard, the wireworms were not distributed at random and independently, but were markedly aggregated. Separation of the wireworms collected from these samples into three size groups showed that the non-random distribution in square-yard samples was largely due to the small larvae, which were strongly aggregated. The medium-sized larvae were less markedly aggregated. The distribution of the large larvae under grass was not significantly different from a random distribution. To understand the factors controlling wireworm distribution it will be necessary to consider the distribution of the different larval age-groups. Two suggestions are made towards an explanation of the geographical distribution of wireworms in England. Study of the spatial distribution of wireworms raises some of the major problems of ecology and, in particular, illustrates the interdependence of spatial distribution and seasonal succession.
Studies on Tapeworm Physiology
Authors: Smyth J. D. 
Published: April 2021

ABSTRACT
A technique has been elaborated that enabled the plerocercoid larvae of Schistocephalus solidus to be removed from the body cavity of Gasterosteus aculeatus without bacterial contamination. Larvae were cultured in plugged test-tubes under completely aseptic conditions in a variety of balanced salines, glucose salines and nutrient peptone broth. The most successful results were obtained with peptone broth at room temperatures (16-19° C) in which plerocercoids remained active and showed normal behaviour for periods up to 300 days. In ¾ strength Locke’s solution, which was found by experiment to be approximately isotonic with Schistocephalus (Δ =-0.44 ± 0.02° C), the mean period of normal behaviour was 114 days. In the remaining saline and saline-glucose media, the mean viability and period of normal behaviour was considerably less. In the plerocercoid, histological examination revealed that the genitalia are in an immature condition. During cultivation at room temperatures, the genitalia remained in this undifferentiated condition and showed no signs of undergoing spermatogenesis, oogenesis or vitellogenesis. Plerocercoids were induced to develop into sexually mature adults by raising the temperature of cultivation in peptone broth to 40° C. (i.e. the body temperature of the final host in the natural life cycle). Oviposition took place after 48-60 hr. at this temperature, and histological examination revealed that spermatogenesis, oogenesis, vitellogenesis and shell formation had taken place in a normal manner. The viability of artificially matured Schistocephalus was 4-6 days in vitro--a period equivalent to the viability of the adult in vivo. The eversion of the cirris was observed in each proglottid after 40 hr. cultivation at 40° C. During the sexual process the cirris everted and invaginated at the rate of about once per second. Cross-fertilization between segments of the same worm or with segments of another worm was not observed. Except for one specimen in ¾ strength Locke’s solution which underwent spermatogenesis and partial vitellogenesis, larvae cultured in salines or glucose salines at 40° C. died within 1-3 days without further development. Attempts to hatch out the eggs produced by the cultivation of larvae in peptone broth at 40° C. proved unsuccessful. Histological examination revealed that spermatozoa had not been taken into the vagina. It was concluded that the eggs were not fertilized owing to the failure of normal copulation to take place.
The Mechanism of Locomotion in Snakes
Authors: Gray J. 
Published: April 2021

ABSTRACT
Among snakes four main types of terrestrial progression have been described: (i) serpentine movement which is observable in all, or nearly all, genera; (ii) concertina movement as briefly described by Wiedemann (1932) in Vipera and Coronella; (iii) crotaline or ‘side-winding’ as seen in Crotalus or Cerastes (Mosauer, 1932a,b); and (iv) rectilinear movement as exhibited by boas and other large types (Home, 1812). The observations described in the present paper have all been made on the common grass snake (Tropidonotus natrix); the evidence to be presented shows that serpentine, concertina or crotaline movements can all be elicited in this genus by appropriate modification of the external forces operating on the body of the moving animal.
The Responses of Onion and Lily Mitosis to Coumarin and Parasorbic Acid
Authors: Cornman Ivor 
Published: April 2021

ABSTRACT
In Allium and Lilium roots, saturated aqueous solution of coumarin produced a disruption of the metaphase typical of many benzene derivatives, viz. suppression of the spindle, splitting and shortening of the chromosomes, with retarded division of the centromere. The resultant polyploid nuclei and binucleate cells resumed division when the roots were returned to water. Saturated solution of parasorbic acid slowed Allium mitosis, but caused no abnormalities. Both coumarin and parasorbic acid eventually prevented the inception of mitosis, and this suppression of prophases persisted for several hours after removal of the agent. The results are in agreement with prior evidence that in some configurations the benzene ring disrupts mitosis whereas the lactone ring inhibits growth.
The Oxygen Consumption of Gasterosteus Aculeatus L. In Toxic Solutions
Authors: Erichsen Jones J. R. 
Published: April 2021

ABSTRACT
A simple apparatus is described with which the oxygen consumption of a small fish may be estimated, first in water and then at successive time intervals in a toxic solution, so that the progressive effect of the solution on the rate of oxygen intake may be graphed.
Chloroform solutions of concentration 1/3000 to 1/5000 gradually depress the respiration rate and are ultimately fatal. A 14/100,000 solution appears to produce a state of anaesthesia in which the oxygen intake is about 30 % normal.
Sodium cyanide solutions bring about a progressive decline in the oxygen intake which is closely accompanied by a decline in the rate of opercular movement. The critical concentration is about 0.00004N, which depresses the respiration rate to 32 % normal in 90 min. At greater dilution the survival time lengthens rapidly. Sodium sulphide solutions give very similar results but are somewhat less toxic than cyanide solutions, and the value for the critical concentrations is about 0.0002N.
Heavy metal salts (mercuric chloride, copper sulphate, lead nitrate) produce at first an increase in the respiration rate. Then the oxygen intake declines, but the rate of opercular movement continues to increase, reaches 180-240/min., continues at this increased rate for some time in the case of dilute solutions and then falls rapidly when the oxygen intake is reduced to 38 % normal.
It is concluded that in the case of cyanides and sulphides, where respiration is inhibited at the tissues, the close agreement between the oxygen intake and opercular movement rate may be attributed to the decline in carbon dioxide production. In the case of the heavy metal salts, on the other hand, where respiration is obstructed at the gill surfaces, it would appear that the carbon dioxide content of the blood is raised so that the respiratory centre is stimulated and the opercular movements increase in speed and amplitude. The continued fall in oxygen intake and accumulation of carbon dioxide maintains this effect for some time, but eventually the fish becomes exhausted, the respiratory movements fail and the fish dies.
The work concludes with some suggestions for further investigation.
Studies on Sterility and Prenatal Mortality in Wild Rabbits
Authors: Rogers Brambell F. W. , Mills Ivor H. 
Published: April 2021

ABSTRACT
The yolk-sac contents were observed to be gelatinous in many embryos of wild rabbits at from 7-to 12-day stages, but particularly at 8 and 9 days. Gelatinous strands were observed in the uterine lumen, often connecting adjoining blastocysts, in 8–12-day stages, but particularly at 8 and 9 days. Gelatinous blastocysts and strands frequently were encountered together in the same uterus. Evidence is adduced that these abnormalities, though tending to occur at slightly earlier stages, are related to the mortality which attains a maximum on the 11th and 12th days. Microscopic examination revealed the presence of a reticulum of fine fibrils in the yolk-sac cavity, the histological characters of which are described. The degree of development of this reticulum varied widely from one uterus to another, and often in the individual embryos of the one litter. The presence of this reticulum, when sufficiently dense, was responsible for the gelatinous character of the yolk-sac contents. The gelatinous strands consisted of felted masses of these fibres and of maternal and foetal tissue debris. The fibrous reticulum was absent from the cavities of the amnion and exocoele. A similar reticulum was present sometimes, though rarely so well developed, in the embryos of tame rabbits. Frequently it was absent. It was shown by histological means that the reticulum was not an artefact. The alternatives, that it was either a micro-organism or a network of organic fibres, remained. Morphologically the reticulum resembled the mycelium of an actinomycete so closely that the possibility that it was an invasive organism belonging to this group could not be ignored. Culture experiments disproved this theory and provided satisfactory evidence that the yolk-sac cavities of tame rabbit embryos containing the reticulum were bacteriologically sterile. Sections of clots of fibrin prepared from rabbit-blood plasma presented a similar histological appearance. The presence of fibrinogen in the yolk-sac fluid of 9-day embryos of tame rabbits was demonstrated by clotting the aspirated and citrated fluid with thrombin. Comparison of the clots formed in parallel series of dilutions of the yolk-sac fluid and of plasma indicated that the concentration of fibrinogen in the former was of the order of 50% of that in the latter. Separation of the fibrin from the residue of the yolk-sac fluid was effected by filtration and repeated washing. The mean weight of dried fibrin obtained per ml. of yolk-sac fluid was 37% of that from plasma and its nitrogen content was 33%. The amount of fibrin in the yolk-sac fluid varied significantly from litter to litter. The mean quantity of nitrogen in the residue of the yolk-sac fluid was 57 % of that in the blood serum. The significance of these results in relation to embryonic nutrition and prenatal mortality is discussed.
The Production-of Fatty Acids in the Alimentary Tract of the Dog
Authors: Phillipson A. T. 
Published: April 2021

ABSTRACT
The significance of fermentation in the large gut of the dog has been investigated. According to the quantities of volatile acids and their relation to body weight, the lower fatty acids do not appear to contribute more than a small portion of the energy requirements of the animal. Evidence is presented to show that the individual acids produced in the large intestine consist largely of acetic and propionic acids and that the amount of butyric present is small. This is the same mixture of acids found where fermentation occurs in the alimentary tract of ruminants, horses, pigs, rabbits and rats. The higher proportion of propionic acid is interesting and suggests that the propionic acid bacteria are normal inhabitants of the large intestine of the dog and possibly of a wide variety of animals.
Transpiration and the Structure of the Epicuticle in Ticks
Authors: Lees A. D. 
Published: April 2021

ABSTRACT
The passage of water through the cuticle of living ticks is greatly influenced by the activities of the underlying epidermal cells. In a previous paper (Lees, 1946) it was shown, for example, that unfed ticks reach a state of equilibrium at a relative humidity of about 90%; and if their water balance is depleted they will take up water through the cuticle when exposed to higher humidities. Furthermore, although exposure to humidities below the equilibrium results in water loss through the cuticle, evaporation is much less rapid than it becomes subsequently if the tick is killed or asphyxiated. It was therefore argued that at low humidities secretion assists in the retention of water. These active processes are only well developed in the unfed tick and become imperceptible after the blood meal has been ingested.
In considering the mechanisms involved in the exchanges of water through the cuticle the assumption was made that, in addition to active secretion, the passage of water, and particularly its retention, is also influenced by the presence of lipoid material in the cuticle. Ticks show great diversity in their powers of resisting desiccation, and this was thought to be accounted for by the specific nature of the waterproofing lipoid. Nevertheless, no direct evidence of such a component was advanced in this paper.
Hovering flight in hummingbird hawkmoths: kinematics, wake dynamics and aerodynamic power
Authors: Warfvinge Kajsa , Johansson L. Christoffer , Hedenström Anders 
Published: April 2021

ABSTRACTHovering insects are divided into two categories: ‘normal’ hoverers that move the wing symmetrically in a horizontal stroke plane, and those with an inclined stroke plane. Normal hoverers have been suggested to support their weight during both downstroke and upstroke, shedding vortex rings each half-stroke. Insects with an inclined stroke plane should, according to theory, produce flight forces only during downstroke, and only generate one set of vortices. The type of hovering is thus linked to the power required to hover. Previous efforts to characterize the wake of hovering insects have used low-resolution experimental techniques or simulated the flow using computational fluid dynamics, and so it remains to be determined whether insect wakes can be represented by any of the suggested models. Here, we used tomographic particle image velocimetry, with a horizontal measurement volume placed below the animals, to show that the wake shed by hovering hawkmoths is best described as a series of bilateral, stacked vortex ‘rings’. While the upstroke is aerodynamically active, despite an inclined stroke plane, it produces weaker vortices than the downstroke. In addition, compared with the near wake, the far wake lacks structure and is less concentrated. Both near and far wakes are clearly affected by vortex interactions, suggesting caution is required when interpreting wake topologies. We also estimated induced power (Pind) from downwash velocities in the wake. Standard models predicted a Pind more than double that from our wake measurements. Our results thus question some model assumptions and we propose a reevaluation of the model parameters.