bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short-Range Navigation: Does it Contribute to Understanding Navigation Over Longer Distances?
Authors: Collett T. S. 
Published: April 2021

ABSTRACT
A major reason for analysing short-range navigation is that it is relatively easy to record on video tape the details of an animal’s behaviour over an area of about a square metre. Frequently, the orientation of the animal’s body is revealed in addition to its trajectory through space. This is particularly useful in the study of insect navigation, the subject of the four contributions to this section. An insect’s eyes are fixed in its head, and there are often no significant head movements during flight. Consequently, reasonable assumptions can be made about where the insect looks while it navigates and how the image of its surroundings moves over its retina. All four contributions depend to a large degree upon being able to freeze behaviour on video tape and to infer what the animal sees. To what extent do the conclusions using the abundant information that can be collected in this way extrapolate to navigation on a larger scale? Clearly, the coded information that instructs the monarch butterfly on its migrations from wide areas of North America to northern Michoacan in Mexico contains elements unique to long-distance travel. But there may be many similarities in the mechanisms available to an orchid bee as it travels over its 20 km foraging route from orchid to orchid and a wasp negotiating the last few metres through a complex environment to reach its nest.
Insect Navigation En Route to the Goal: Multiple Strategies for the Use of Landmarks
Authors: Collett T. S. 
Published: April 2021

ABSTRACT
There are at least four distinct ways in which familiar landmarks aid an insect on its trips between nest and foraging site. Recognising scenes: when bees are displaced unexpectedly from their hive to one of several familiar locations, they are able to head in the direction of home as though they had previously linked an appropriate directional vector to a view of the scene at the release site. Biased detours: ants recognise familiar landmarks en route and will correct their path by steering consistently to the left or to the right around them. Aiming at beacons: bees and ants also guide their path by approaching familiar landmarks lying on or close to the direct line between start and finish. Simulations suggest that such mechanisms acting together may suffice to account for the routes taken by desert ants through a landmark-strewn environment: the stereotyped trajectories of individual ants can be modelled by a weighted combination of dead reckoning, biased detours and beacon-aiming. These mechanisms guide an insect sufficiently close to an inconspicuous goal for image matching to be successfully employed to locate it. Insects then move until their current retinal image matches a stored view of the surrounding panorama seen from a vantage point close to the goal.
Bees and wasps perform learning flights on their first departure from a site to which they will return. These flights seem to be designed to pick up the information needed for several navigational strategies. Thus, a large portion of the learning flight of a bee leaving a feeder tends to be spent close to the feeder so aiding the acquisition of a view from that vantage point, as is needed for image matching. Bees and social wasps also tend to inspect their surroundings while facing along preferred directions and to adopt similar bearings before landing, thereby making it easy to employ retinotopically stored patterns in image matching. Aiming at beacons, in contrast, requires a landmark to be familiar to the frontal retina. Objects tend to be viewed frontally while the insect circles through arcs centred on the goal. This procedure may help insects to pick out those objects close to the goal that are best suited for guiding later returns.
Magnetic Orientation in Birds
Authors: Wiltschko Wolfgang , Wiltschko Roswitha 
Published: April 2021

ABSTRACT
The magnetic field of the earth is an omnipresent, reliable source of orientational information. A magnetic compass has been demonstrated in 18 species of migrating birds. In all species studied with regard to its functional properties, it was found to be an ‘inclination compass’, i.e. the birds derive directional information from the inclination of the field lines, and thus distinguish between ‘poleward’ and ‘equatorward’ rather than ‘north’ and ‘south’. Such a mechanism means that birds from the northern and southern hemisphere may rely on the same migratory programme. Long-distance migrants, however, face the problem that their magnetic compass gives bimodal information at the magnetic equator. Transfers of information between the magnetic field and celestial sources of directional information have been demonstrated; the two systems interact in a complex way. The data on the use of magnetic parameters for position finding are less clear. The experiments involve releases of homing pigeons; correlations of their orientation with natural variations in the magnetic field and the effects of magnetic manipulation reveal an enormous variability. The role of magnetic parameters in the multifactorial navigational system is poorly understood.
Orientation and Open-Sea Navigation in Sea Turtles
Authors: Lohmann Kenneth J. , Lohmann Catherine M. F. 
Published: April 2021

ABSTRACT
Loggerhead sea turtle hatchlings (Caretta caretta L.) emerge from underground nests, scramble to the sea and begin a transoceanic migration by swimming away from their natal beach and into the open ocean. Evidence suggests that hatchlings sequentially use three different sets of cues to maintain orientation during their initial migration offshore. While on the beach, hatchlings find the ocean by crawling towards the lower, brighter seaward horizon and away from the dark, elevated silhouettes of vegetation and dunes. Upon entering the ocean, turtles initially orient seawards by swimming into waves, which can be detected as orbital movements from under water.
Laboratory experiments have demonstrated that turtles can transfer a course initiated on the basis of waves or visual cues to a course mediated by a magnetic compass. Thus, by setting a magnetic course on the basis of nearshore cues that indicate the seaward direction, hatchlings may continue on offshore headings after entering deep water beyond sight of land.
Sea turtles may use the earth’s magnetic field not only as a cue for compass orientation but also as a source of world-wide positional information. Recent experiments have demonstrated that loggerheads can detect subtle differences in magnetic field inclination and intensity, two geomagnetic features that vary across the surface of the earth. Because most nesting beaches and oceanic regions are marked by a unique combination of these features, these findings raise the possibility that adult sea turtles navigate using a bicoordinate magnetic map.
Monarch Butterfly Orientation: Missing Pieces of a Magnificent Puzzle
Authors: Brower Lincoln P. 
Published: April 2021

ABSTRACT
From late August to early September, millions of adult monarch butterflies of the eastern North American population cease reproducing, become highly gregarious and begin migrating southwards. By mid-October, they migrate through central Texas into Mexico where they follow the Sierra Madre Oriental across the Tropic of Cancer. They then shift direction westwards towards the Transverse Neovolcanic Belt of mountains where they overwinter without breeding. A rapid exodus northwards occurs at the spring equinox, and by early April both sexes reach the Gulf Coast states where the females lay eggs on the resurgent spring milkweed (Asclepias) flora and die. Adults of the new generation continue the migration to the northernmost breeding range, arriving by early June. Two or more short-lived breeding generations are produced over the summer, spread eastwards across the Appalachian Mountains and, by September, the autumn migration is again under way. This paper presents a new hypothesis that the orientation of adult monarchs undergoes a continual clockwise shifting throughout the 3–5 generations, rotating by 360 ° in the course of the year. This hypothesis is consistent with the timing of arrivals and the relative abundances of the successive generations of monarchs throughout eastern North America, with the directions of movement of their spring, summer and autumn generations, and with the timing of their arrival at the overwintering area in central Mexico.
The Interaction of Pulmonary Ventilation and the Right–Left Shunt on Arterial Oxygen Levels
Authors: Wang Tobias , Hicks James W. 
Published: April 2021

ABSTRACT
In adult mammals, arterial blood gases closely reflect lung gas composition, and arterial blood gases can, therefore, be effectively regulated through changes in ventilation. This is not the case among most ectothermic vertebrates, where the systemic and pulmonary circulations are not completely separated, resulting in central vascular shunts. In the presence of a right-to-left shunt (R–L shunt), the O2 levels ( and haemoglobin O2-saturation) of systemic arterial blood are depressed relative to those of the blood returning from the lungs. Arterial blood gas composition is, accordingly, not determined only by ventilation, but also by the magnitude of admixture as well as the blood gas composition of systemic venous blood. Changes in the central shunt patterns, therefore, represent an alternative mechanism by which to control arterial blood gas levels. The primary aim of this report is to evaluate the relative importance of the R–L shunt and ventilation in determining arterial blood gas levels.
Using standard equations for gas exchange and the two-compartment model, we predicted arterial O2 levels at physiologically relevant levels of ventilation, R–L shunt and blood flows. The analyses show that the effects of changing ventilation and the size of the R–L shunt on arterial O2 levels vary with parameters such as the rate of O2 uptake, the blood O2-carrying capacity and the level of hypoxia. The relative importance of ventilation and the R–L shunt in determining arterial values is largely explained by the sigmoidal shape of the O2 dissociation curve. Thus, if lung is high relative to blood O2 affinity, a large change in ventilation may have little effect on pulmonary venous O2 content, although may have changed considerably. If an R–L shunt is taking place, this, in turn, implies that arterial O2 content is affected only marginally, with a correspondingly small effect on . These predictions are discussed in the light of the limited existing experimental data on cardiac shunts in lower vertebrates; we propose that, in future experiments, the measurement of both ventilatory and cardiovascular parameters must be combined if we aim to understand the regulation of arterial blood gas levels in lower vertebrates.
Functions of Fish Skin: Flexural Stiffness and Steady Swimming of Longnose Gar Lepisosteus Osseus
Authors: Long John H. , Hale Melina E. , Mchenry Matt J. , Westneat Mark W. 
Published: April 2021

ABSTRACT
The functions of fish skin during swimming remain enigmatic. Does skin stiffen the body and alter the propagation of the axial undulatory wave? To address this question, we measured the skin’s in situ flexural stiffness and in vivo mechanical role in the longnose gar Lepisosteus osseus. To measure flexural stiffness, dead gar were gripped and bent in a device that measured applied bending moment (N m) and the resulting midline curvature (m−1). From these values, the flexural stiffness of the body (EI in N m2) was calculated before and after sequential alterations of skin structure. Cutting of the dermis between two caudal scale rows significantly reduced the flexural stiffness of the body and increased the neutral zone of curvature, a region of bending without detectable stiffness. Neither bending property was significantly altered by the removal of a caudal scale row. These alterations in skin structure were also made in live gar and the kinematics of steady swimming was measured before and after each treatment. Cutting of the dermis between two caudal scale rows, performed under anesthesia, changed the swimming kinematics of the fish: tailbeat frequency (Hz) and propulsive wave speed (body lengths per second, L s−1) decreased, while the depth (in L) of the trailing edge of the tail increased. The decreases in tailbeat frequency and wave speed are consistent with predictions of the theory of forced, harmonic vibrations; wave speed, if equated with resonance frequency, is proportional to the square root of a structure’s stiffness. While it did not significantly reduce the body’s flexural stiffness, surgical removal of a caudal scale row resulted in increased tailbeat amplitude and the relative total hydrodynamic power. In an attempt to understand the specific function of the scale row, we propose a model in which a scale row resists medio-lateral force applied by a single myomere, thus functioning to enhance mechanical advantage for bending. Finally, surgical removal of a precaudal scale row did not significantly alter any of the kinematic variables. This lack of effect is associated with a lower midline curvature of the precaudal region during swimming compared with that of the caudal region. Overall, these results demonstrate a causal relationship between skin, the passive flexural stiffness it imparts to the body and the influence of body stiffness on the undulatory wave speed and cycle frequency at which gar choose to swim.
Contributions of Structure and Innervation Pattern of the Stick Insect Extensor Tibiae Muscle to the Filter Characteristics of the Muscle–Joint System
Authors: Bässler Ulrich , Stein Wolfgang 
Published: April 2021

ABSTRACT
It is shown that the low-pass filter characteristics of the muscle–joint system of the femur–tibia joint of the stick insect Cuniculina impigra result from co-contraction of the extensor and flexor tibiae muscles. The most distal region of the extensor muscle, which contains a high percentage of slow muscle fibres, is involved in this co-contraction. This conclusion results from the following evidence. (1) Inertial and friction forces do not affect the characteristics of the low-pass filter of the muscle–joint system. (2) There is some co-contraction of the extensor and flexor muscles during sinusoidal stimulation of the femoral chordotonal organ at high stimulus frequencies. Both muscles generate tonic forces that increase with increasing stimulus frequency and also increase with time from the beginning of stimulation until a plateau is reached. (3) For the extensor muscle, this tonic force is produced by its most distal portion only. (4) Electrical stimulation of the common inhibitory motoneurone (CI1) reduces the tonic force generated in this most distal portion of the extensor muscle. Therefore, CI1 stimulation reduces the amplitude of tibial movement in response to sinusoidal stimulation of the femoral chordotonal organ at stimulus frequencies below 0.5 Hz (over this frequency range, the tibial movement amplitude is a function of the force amplitude produced by the whole extensor muscle and there is no co-contraction), but at chordotonal organ stimulus frequencies of 1 Hz and above, CI1 stimulation increases the tibial movement amplitude (in this case, movement amplitude is limited by the degree of co-contraction of the extensor and flexor muscles).
With repeated chordotonal organ stimulation at higher stimulus frequencies, the tibial movement amplitude steadily decreases. This must be a consequence of increasing levels of co-contraction of the extensor and flexor muscles, since at low stimulus frequencies (no co-contraction) there is no reduction in movement amplitude during repeated stimulations.
It is concluded that co-contraction of the extensor and flexor tibiae muscles prevents instability in the reflex loop in spite of the high gain necessary for the generation of catalepsy. Therefore, the mechanism described can be considered to be an adaptation to the ecological niche occupied by this animal. The contribution of the distal part of the extensor muscle to this system can be switched off by the CI1 during active movements.
Heterocercal Tail Function in Leopard Sharks: A Three-Dimensional Kinematic Analysis of Two Models
Authors: Ferry Lara A. , Lauder George V. 
Published: April 2021

ABSTRACT
Two different models have been proposed to explain the function of the heterocercal tail in shark locomotion. The classical model proposes that, as a result of lift generated by the tail as it beats, the net force acting on the tail is directed dorsally and anteriorly. In contrast, Thomson’s model suggests that the tail generates a net force directed through the shark’s center of gravity, i.e. ventrally and anteriorly. In this study, we evaluate these two models by describing the three-dimensional kinematics of the heterocercal tail in the leopard shark Triakis semifasciata during swimming. Lateral and posterior views of the tail were examined from four individuals swimming in a flow tank at 1.2 L s−1 (where L is total length) using two high-speed video cameras filming simultaneously at 250 fields s−1. These two simultaneous views allowed eight landmarks on the tail to be followed in three dimensions through time. These landmarks allowed the tail to be divided into separate surfaces whose orientation over time was calculated. Points located anteriorly on the tail go through significantly smaller excursions and reach their maximum lateral excursion significantly earlier in the beat cycle than points on the trailing edge of the tail. Three-dimensional angle calculations show that the terminal lobe leads the ventral lobe through a beat, as predicted by the classical model. Dye-stream visualizations confirmed that this pattern of movement deflects water ventrally and posteriorly to the moving tail, providing strong support for the classical model. Additionally, our results show that a three-dimensional analysis is critical to understanding the function of the heterocercal tail.
Electrophysiological and Endocrinological Evidence That F-Series Prostaglandins Function as Priming Pheromones in Mature Male Atlantic Salmon (Salmo Salar) Parr
Authors: Moore Andrew , Waring Colin P. 
Published: April 2021

ABSTRACT
Previous work has demonstrated that the urine from mature female salmonids contains a priming pheromone that significantly enhances the reproductive physiology of receiving males. The chemical identity of the pheromone(s) has not yet been identified. The present study investigated the possibility that F-type prostaglandins (PGFs) may have a pheromonal role in Atlantic salmon by measuring the olfactory sensitivity of male salmon to PGFs, the effect of waterborne PGFs on male reproductive physiology and the PGF content of mature female urine. Electrophysiological studies demonstrated that the olfactory epithelium of mature male salmon parr was acutely sensitive to PGF1α and PGF2α, with detection threshold concentrations of 10−11 mol l−1. The olfactory epithelium was also sensitive to the PGF metabolite 15-ketoPGF2α (threshold 10−8 mol l−1), but did not detect a further metabolite, 13,14-dihydro-15-ketoPGF2α. Sensitivity to both PGF1α and PGF2α increased as the reproductive season progressed. Exposure of mature male parr to waterborne PGF1α and PGF2α (10−8 mol l−1) resulted in significant increases in levels of expressible milt and in the plasma concentrations of 17,20β-dihydroxy-4-pregnen-3-one, testosterone and 11-ketotestosterone. Urine from ovulated female salmon also contained large quantities (18 ng ml−1) of immunoreactive PGFs, whereas urine from mature males and non-ovulated mature females contained significantly smaller amounts (&lt;1 ng ml−1). The results support the theory that PGFs function as priming pheromones in Atlantic salmon and are released in the urine of ovulated female salmon. The involvement of these pheromones in synchronising male–female salmon spawning is discussed.
Mitochondria-Rich, Proton-Secreting Epithelial Cells
Authors: Brown Dennis , Breton Sylvie 
Published: April 2021

ABSTRACT
Several transporting epithelia in vertebrates and invertebrates contain cells that are specialized for proton or bicarbonate secretion. These characteristic ‘mitochondria-rich’ (MR) cells have several typical features, the most important of which is an extremely high expression of a vacuolar-type proton-pumping ATPase (H+V-ATPase) both on intracellular vesicles and on specific domains of their plasma membrane. Physiological modulation of proton secretion is achieved by recycling the H+V-ATPase between the plasma membrane and the cytoplasm in a novel type of nonclathrin-coated vesicle. In the kidney, these cells are involved in urinary acidification, while in the epididymis and vas deferens they acidify the luminal environment to allow normal sperm development. Osteoclasts are non-epithelial MR cells that use H+V-ATPase activity for bone remodeling. In some insects, similar cells in the midgut energize K+ secretion by means of a plasma membrane H+V-ATPase. This review emphasizes important structural and functional features of proton-secreting cells, describes the tissue distribution of these cells and discusses the known functions of these cells in their respective epithelia.
New Features of the Locust Optic Lobe: Evidence of a Role for Nitric Oxide in Insect Vision
Authors: Elphick Maurice R. , Williams Les , O’shea Michael 
Published: April 2021

ABSTRACT
The enzyme nitric oxide synthase can be localised by NADPH-diaphorase histochemistry. Here we have applied this technique to the optic lobe of the locust Schistocerca gregaria and revealed new features of the insect visual system. Extensive but locally intense staining is associated with identified tracts, distinct neuropiles and cell body groups, and a detailed analysis of stained elements is provided here. The most striking staining occurs in the anterior lo Nbe of the lobula complex and its connection with the medulla by means of the dorsal uncrossed bundle. Eleven groups of cell bodies are identified and their contribution to fibre tracts and neuropile areas is described. Diaphorase-positive fibre tracts pass between all major subdivisions of the optic lobe, but there are no conspicuous fibre connections from the optic lobe to the brain. The widespread distribution of NADPH-diaphorase staining in the optic lobe suggests that nitric oxide is likely to play an important role in information processing in insect vision.