bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gliding Flight: Drag and Torque of a Hawk and a Falcon With Straight and Turned Heads, and a Lower Value For The Parasite Drag Coefficient
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
Raptors – falcons, hawks and eagles in this study – such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 ° to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s−1. With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct.
The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor’s higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals.
In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (CD,par) of 0.18 previously used for calculating the gliding performance of a peregrine.
The accuracy with which drag coefficients measured on wingless bird bodies in a wind tunnel represent the CD,par of a living bird is unknown. Another method for determining CD,par selects values that improve the fit between speeds predicted by mathematical models and those observed in living birds. This method yields lower values for CD,par (0.05–0.07) than wind tunnel measurements, and the present study suggests a value of 0.1 for raptors as a compromise.
The Deep Fovea, Sideways Vision and Spiral Flight Paths in Raptors
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
Raptors – falcons, hawks and eagles in this study – have two regions of the retina in each eye that are specialized for acute vision: the deep fovea and the shallow fovea. The line of sight of the deep fovea points forwards and approximately 45 ° to the right or left of the head axis, while that of the shallow fovea also points forwards but approximately 15 ° to the right or left of the head axis. The anatomy of the foveae suggests that the deep fovea has the higher acuity.
Several species of raptors in this study repeatedly moved their heads among three positions while looking at an object: straight, with the head axis pointing towards the object; or sideways to the right or left, with the head axis pointing approximately 40 ° to the side of the object. Since raptors do not rotate their eyes noticeably in the sockets, these movements presumably cause the image of the object to fall on the shallow and deep foveae. The movements occurred approximately every 2 s on average in hawks and falcons, and approximately every 5 s in bald eagles.
The proportion of time that the raptors spent looking straight or sideways at an object depended on how far away the object was. At a distances closer than 8 m, they spent more time looking at the object straight, but as the distance increased to 21 m, they spent more time looking at it sideways. At distances of 40 m or more, raptors looked sideways at the object 80 % or more of the time. This dependence of head position on distance suggests that raptors use their more acute sideways vision to look at distant objects and sacrifice acuity for stereoscopic binocular vision to look at close objects.
Having their most acute vision towards the side causes a conflict in raptors such as falcons, which dive at prey from great distances at high speeds: at a speed of 70 m s−1, turning their head sideways to view the prey straight ahead with high visual acuity may increase aerodynamic drag by a factor of 2 or more and slow the raptor down. Raptors could resolve this conflict by diving along a logarithmic spiral path with their head straight and one eye looking sideways at the prey, rather than following the straight path to the prey with their head turned sideways. Although the spiral path is longer than the straight path, a mathematical model for an ‘ideal falcon’ shows that the falcon could reach the prey more quickly along the spiral path because the speed advantage of a straight head more than compensates for the longer path.
Mass, Temperature and Metabolic Effects on Discontinuous Gas Exchange Cycles in Eucalyptus-Boring Beetles (Coleoptera: Cerambycidae)
Authors: Chappell Mark A. , Rogowitz Gordon L. 
Published: April 2021

ABSTRACT
Ventilatory accommodation of changing metabolic rates is a relatively little-studied aspect of the discontinuous gas exchange cycles (DGCs) that occur in a wide variety of terrestrial arthropods. We used correlation analysis of resting metabolic rate (RMR, measured as the rate of CO2 emission; ) and several components of the DGC to examine accommodation to both temperature-induced changes and individual variation in RMR in two wood-boring beetles (Phorocantha recurva and P. semipunctata; Coleoptera: Cerambycidae).
At low to moderate ambient temperatures (Ta; 10–20 °C), Phorocantha spp. displayed a characteristic DGC with relatively brief but pronounced open (O) phase bursts of CO2 emission separated by longer periods of low , the flutter (F) phase. However, the never fell to zero, and we could not reliably differentiate a typical closed (C) phase from the F phase. Accordingly, we pooled the C and F phases for analysis as the C+F phase. At higher Ta (30 °C), the duration of the combined C+F phase was greatly reduced. There were no differences between the two species or between males and females in either RMR or characteristics of the DGC. We found large variation in the major DGC components (cycle frequency, durations and emission volumes of the O and C+F phases); much of this variation was significantly repeatable. Accommodation of temperature-induced RMR changes was almost entirely due to changes in frequency (primarily in the C+F phase), as has been found in several other discontinuously ventilating arthropods. Frequency changes also contributed to accommodation at constant Ta, but modulation of emission volumes (during both O and C+F phases) played a larger role in this case.
The DGC is often viewed as a water conservation mechanism, on the basis that respiratory evaporation is minimal during the C and F phases. This hypothesis assumes that the F phase is primarily convective (because of a reduction in tracheal and total intratracheal pressure during the C phase). To test this, we measured the DGC in beetles subjected to varying degrees of hypoxia in addition to normoxia. As predicted for a largely diffusive F phase, we found an increase in the volume of CO2 emitted during the C+F phase in hypoxic conditions (10.4 % oxygen). This finding, together with a reduced tendency to utilize a DGC at high Ta (when water stress is greatest) and a natural history in which water availability is probably not limiting for any life stage, suggests that a reduction of respiratory evaporation may not have been critical in the evolution of the DGC of Phorocantha spp. Instead, selection may have favored discontinuous ventilation because it facilitates gas exchange in the hypercapnic and hypoxic environments commonly encountered by animals (such as Phorocantha spp.) that live in confined spaces.
Olfactory Sensitivity to Changes In Environmental [Ca2+] in The Marine Teleost Sparus Aurata
Authors: Hubbard P. C. , Barata E. N. , Canario A. V. M. 
Published: April 2021

ABSTRACT
Estuarine and/or migratory teleosts may experience large and rapid changes in external [Ca2+]. Previous studies have largely centred on the physiological mechanisms that maintain a constant plasma [Ca2+] in the face of such external fluctuations, but little work has been directed to examining how these changes may originally be detected. We present evidence that the olfactory system of the gilthead seabream (Sparus aurata) is highly sensitive to reductions in environmental [Ca2+] and suggest a possible mechanism by which this may be mediated. Multi-unit extracellular recordings were made from the olfactory nerve of Sparus aurata while the [Ca2+] of artificial sea water flowing over the olfactory epithelium was varied from 10 to 0 mmol l−1. Reductions in [Ca2+] caused a large, non-accommodating increase in the firing rate of the olfactory nerve (apparent IC50=1.67±0.26 mmol l−1, apparent Hill coefficient=−1.22±0.14; means ± S.E.M., N=6). This response was not due to the concomitant reduction in osmolality and was specific for Ca2+. During continuous exposure of the olfactory epithelium to Ca2+-free sea water, the apparent IC50 and Hill coefficient in response to increases in [Ca2+] were 0.48±0.14 mmol l−1 and −0.76±0.16 (means ± S.E.M., N=6), respectively, suggesting an adaptation of the Ca2+-sensing system to low-[Ca2+] environments. Ca2+ is intimately involved in signal transduction in the olfactory receptor neurones, but our data support a true olfactory response, rather than a non-specific effect to lowering of external [Ca2+]. The absence of Ca2+ from sea water only partially and temporarily blunted the olfactory response to the odorant L-serine; the response amplitude recovered to control levels within 20 min. This suggests that the olfactory system in general is able to adapt to low-[Ca2+] environments. We suggest that the Ca2+ sensitivity is mediated by an extracellular Ca2+-sensing receptor similar to the recently characterized mammalian Ca2+-sensing receptor.
Interruption of Cardiac Output Does Not Affect Short-Term Growth and Metabolic Rate in day 3 And 4 Chick Embryos
Authors: Burggren Warren W. , Warburton Stephen J. , Slivkoff Mark D. 
Published: April 2021

ABSTRACT
The heart beat of vertebrate embryos has been assumed to begin when convective bulk transport by blood takes over from transport by simple diffusion. To test this hypothesis, we measured eye grow.th, cervical flexure and rates of oxygen consumption in day 3–4 chick embryos denied cardiac output by ligation of the outflow tract and compared them with those of embryos with an intact cardiovascular system.
Eye diameter, used as the index for embryonic growth, increased at a rate of approximately 4.5–5 % h−1 during the observation period. There was no significant difference (P&gt;0.1) in the rate of increase in eye diameter between control (egg opened), sham-ligated (ligature present but not tied) and ligated embryos. Similarly, the normal progression of cervical flexure was not significantly altered by ligation (P&gt;0.1).
(ml O2 g−1 h−1) at 38 °C, measured by closed respirometry, was not significantly different (P&gt;0.1) on day 3 in sham-ligated (14.5±1.9 ml O2 g−1 h−1) and ligated 17.6±1.8 ml O2 g−1 h−1) embryos. Similarly, on day 4, in sham-ligated and ligated embryos was statistically the same (sham-ligated 10.5±2.9 ml O2 g−1 h−1; ligated 9.7±2.9 ml O2 g−1 h−1). Expressed as a linear function of body mass (M), in sham-ligated embryos was described by the equat.ion , while in ligated embryos was described by the equation . The regression line describing the relationship between body mass and for pooled sham-ligated and ligated embryos (the two populations being statistically identical) was . The slope of this regression line, which was significantly different from zero (r2=0.30, N=34, P&lt;0.01), was similar to slopes calculated from previous studies over the same range of body mass.
Collectively, these data indicate that growth and are not dependent upon cardiac output and the convective blood flow it generates. Thus, early chick embryos join those of the zebrafish, clawed frog and axolotl in developing a heart beat and blood flow hours or days before required for convective oxygen and nutrient transport. We speculate that angiogenesis is the most likely role for the early development of a heart beat in vertebrate embryos.
Octopamine Reverses the Isolation-Induced Increase in Trophallaxis in the Carpenter ant Camponotus Fellah
Authors: Boulay R. , Soroker V. , Godzinska E. J. , Hefetz A. , Lenoir A. 
Published: April 2021

ABSTRACT
Social deprivation is an unusual situation for ants that normally maintain continuous contact with their nestmates. When a worker was experimentally isolated for 5 days and then reunited with a nestmate, she engaged in prolonged trophallaxis. It is suggested that trophallaxis allows her to restore a social bond with her nestmates and to re-integrate into the colony, particularly via the exchange of colony-specific hydrocarbons. Octopamine reduced trophallaxis in these workers as well as hydrocarbon transfer between nestmates, but not hydrocarbon biosynthesis. Administration of serotonin to such 5-day-isolated ants had no effect on the percentage of trophallaxis. Administration of phentolamine alone, an octopamine antagonist, had no effect, but when co-administrated with octopamine it reduced the effect of octopamine alone and restored trophallaxis to control levels. Moreover, the observed effect of octopamine was not due to a non-specific effect on locomotor activity. Therefore, we hypothesise that octopamine mediates behaviour patterns linked to social bonding, such as trophallaxis. On the basis of an analogy with the role of norepinephrine in vertebrates, we suggest that the levels of octopamine in the brain of socially deprived ants may decrease, together with a concomitant increase in their urge to perform trophallaxis and to experience social contacts. Octopamine administration may reduce this social deprivation effect, and octopamine could therefore be regarded as being partly responsible for the social cohesion between nestmates in ant colonies.
Temperature-Induced Pupil Movements in Insect Superposition Eyes
Authors: Nordström Peter , Warrant Eric J. 
Published: April 2021

ABSTRACT
In this paper, we describe the hitherto largely overlooked effect of temperature on the pupil of insect compound eyes. In the turnip moth Agrotis segetum and in two other nocturnal insects with superposition eyes, the lacewing Euroleon nostras and the codling moth Cydia pomonella, the pupil not only opens and closes with changes in the ambient light level, as expected, but also with changes in temperature in the absence of light. In complete darkness, the pupil of A. segetum responds over a wide range of temperatures, with the pupillary pigments migrating to a light-adapted position when the animal is exposed to either low or high temperatures. At temperatures between 21.0 and 22.7 °C, the pigments migrate to the fully dark-adapted position, resulting in an open pupil and maximal eye glow. Pupil closure at high temperatures shows two distinct thresholds: the first at 23.8±0.7 °C and a second some degrees higher at 25.7±1.2 °C (means ± S.D., N=10).
Temperatures exceeding the first threshold (the activation temperature, Ta) initiate a closure of the pupil that is completed when the temperature exceeds the second threshold (the closure temperature, Tc), which causes rapid and complete migration of pigment to the light-adapted position. All temperatures above Ta affect the pupil, but only temperatures exceeding Tc result in complete closure. Temperatures between Ta and Tc cause a slow, partial and rather unpredictable closure. The lacewing and the codling moth both show very similar responses to those of A. segetum, suggesting that this response to temperature is widespread in superposition eyes. The possibility that the ambient temperature could be used to pre-adapt the eye to different light intensities is discussed.
Transcriptional control of Ca2+-activated K+ channel expression: identification of a second, evolutionarily conserved, neuronal promoter
Authors: Bohm Rudolf A. , Wang Bin , Brenner Robert , Atkinson Nigel S. 
Published: April 2021

ABSTRACT
Neuronal signaling properties are largely determined by the quantity and combination of ion channels expressed. The Drosophila slowpoke gene encodes a Ca2+-activated K+ channel used throughout the nervous system. The slowpoke transcriptional control region is large and complex. To simplify the search for sequences responsible for tissue-specific expression, we relied on evolutionary conservation of functionally important sequences. A number of conserved segments were found between two Drosophila species. One led us to a new 5′ exon and a new transcriptional promoter: Promoter C0. In larvae and adults, Promoter C0 was demonstrated to be neural-specific using flies transformed with reporter genes that either contain or lack the promoter. The transcription start site of Promoter C0 was mapped, and the exon it appends to the 5′ end of the mRNA was sequenced. This is the second neural-specific slowpoke promoter to be identified, the first being Promoter C1. Promoter choice does not alter the encoded polypeptide sequence. RNAase protection assays indicate that Promoter C0 transcripts are approximately 12 times more abundant that Promoter C1 transcripts. Taken together, these facts suggest that promoter choice may be a means for cells to control channel density.
The Molecular Biology of Invertebrate Voltage-Gated Ca2+ Channels
Authors: Jeziorski Michael C. , Greenberg Robert M. , Anderson Peter A. V. 
Published: April 2021

ABSTRACT
The importance of voltage-gated Ca2+ channels in cellular function is illustrated by the many distinct types of Ca2+ currents found in vertebrate tissues, a variety that is generated in part by numerous genes encoding Ca2+ channel subunits. The degree to which this genetic diversity is shared by invertebrates has only recently become apparent. Cloning of Ca2+ channel subunits from various invertebrate species, combined with the wealth of information from the Caenorhabditis elegans genome, has clarified the organization and evolution of metazoan Ca2+ channel genes. Functional studies have employed novel structural information gained from invertebrate Ca2+ channels to complement ongoing research on mammalian Ca2+ currents, while demonstrating that the strict correspondence between pharmacological and molecular classes of vertebrate Ca2+ channels does not fully extend to invertebrate tissues. Molecular structures can now be combined with physiological data to develop a more cogent system of categorizing invertebrate channel subtypes. In this review, we examine recent progress in the characterization of invertebrate Ca2+ channel genes and its relevance to the diversity of invertebrate Ca2+ currents.
Responsiveness of Olfactory Neurons to Distinct Aliphatic Aldehydes
Authors: Kaluza Jan F. , Breer Heinz 
Published: April 2021

ABSTRACT
The responsiveness of isolated olfactory sensory neurons to stimulation with aliphatic aldehydes of varying chain length (5–10 hydrogenated carbon atoms) was investigated by means of Ca2+ imaging. More than half the cells examined were responsive to aliphatic aldehydes. Individual cells did not react or reacted to one or multiple aldehydes; in the latter case, cells only reacted to aldehydes of consecutive carbon chain lengths. The largest proportion of cells responded to octanal. It was also demonstrated that a structural difference as small as one hydrogenated carbon atom was detectable by the olfactory neurons.
Neurons were increasingly able to discriminate between two aldehydes as the difference in chain length between the two increased. Discrimination between aldehydes with longer carbon chains was reduced. Although the odorants examined belong to a distinct chemical class and differ only slightly in structure, individual olfactory sensory neurons showed quite different receptive properties.
Heat Shock-Induced Thermoprotection of Hindleg Motor Control in the Locust
Authors: Barclay J. W. , Robertson R. M. 
Published: April 2021

ABSTRACT
Functional neuromuscular connections are critical for appropriate behavioural responses, but can be negatively affected by increases in temperature. We investigated the effects of heat shock on the thermosensitivity of a neuromuscular pathway to the hindleg tibial extensor muscle of Locusta migratoria. We found that exposure to heat shock induced thermoprotection of both neuromuscular transmission and extensor muscle contraction by (i) increasing the upper temperature limit for failure, (ii) improving recovery following heat-induced failure and (iii) stabilizing excitatory junction potential amplitude and duration and extensor muscle contraction force at high temperatures. Furthermore, the heat-shock-induced thermoprotection of extensor muscle contraction was not attributable to a protective effect on intrinsic components of muscle contraction. Finally, the use of jumping as a locomotor strategy to avoid capture, a behavioural response dependent upon functionally competent neuromuscular connections at the hindleg tibial extensor muscle, became less sensitive to temperature following heat shock. We conclude that the natural stress response of the locust stabilizes neuromuscular signalling during temperature stress, and that this can underlie a thermoprotection of muscle contraction force and thus alter the thermosensitivity of an escape behaviour critical for survival.
Thermotolerant Desert Lizards Characteristically Differ in Terms of Heat-Shock System Regulation
Authors: Zatsepina O. G. , Ulmasov KH. A. , Beresten S. F. , Molodtsov V. B. , Rybtsov S. A. , Evgen’EV M. B. 
Published: April 2021

ABSTRACT
We compare the properties and activation of heat-shock transcription factor (HSF1) and the synthesis of a major family of heat-shock proteins (HSP70) in lizard species inhabiting ecological niches with strikingly different thermal parameters. Under normal non-heat-shock conditions, all desert-dwelling lizard species studied so far differ from a northern, non-desert species (Lacerta vivipara) in the electrophoretic mobility and content of proteins constitutively bound to the regulatory heat-shock elements in the heat-shock gene promoter. Under these conditions, levels of activated HSF1 and of both HSP70 mRNA and protein are higher in the desert species than in the non-desert species. Upon heat shock, HSF1 aggregates in all species studied, although in desert species HSF1 subsequently disaggregates more rapidly. Cells of the northern species have a lower thermal threshold for HSP expression than those of the desert species, which correlates with the relatively low constitutive level of HSPs and high basal content of HSF1 in their cells.