bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limits to Optimization: Fluid Dynamics, Adhesive Strength and the Evolution of Shape in Limpet Shells
Authors: Denny Mark W. 
Published: April 2021

ABSTRACT
Limpets are commonly found on wave-swept rocky shores, where they may be subjected to water velocities in excess of 20 m s−. These extreme flows can impose large forces (lift and drag), challenging the animal’s ability to adhere to the substratum. It is commonly thought that the conical shape of limpet shells has evolved in part to reduce these hydrodynamic forces while providing a large aperture for adhesion. This study documents how lift and drag actually vary with the shape of limpet-like models and uses these data to explore the potential of hydrodynamic forces to serve as a selective factor in the evolution of limpet shell morphology. At a low ratio of shell height to shell radius, lift is the dominant force, while at high ratios of height to radius drag is dominant. The risk of dislodgment is minimized when the ratio of height to radius is 1.06 and the apex is in the center of the shell. Real limpets are seldom optimally shaped, however, with a typical height-to-radius ratio of 0.68 and an apex well anterior of the shell’s center. The disparity between the actual and the hydrodynamically optimal shape of shells may be due to the high tenacity of limpets’ adhesive system. Most limpets adhere to the substratum so strongly that they are unlikely to be dislodged by lift or drag regardless of the shape of their shell. The evolution of a tenacious adhesion system (perhaps in response to predation) has thus pre-empted selection for a hydrodynamically optimal shell, allowing the shell to respond to alternative selective factors.
Hydrodynamics, Shell Shape, Behavior and Survivorship in the Owl Limpet Lottia Gigantea
Authors: Denny Mark W. , Blanchette Carol A. 
Published: April 2021

ABSTRACT
On wave-swept rocky shores, limpets are subjected to water velocities in excess of 20 m s−1, which may impose large hydrodynamic forces. Despite the extreme severity of this flow environment, predictions from conical models suggest that limpets’ shells are typically far from the optimal shape that would minimize the risk of dislodgment, a deviation that is allowed by the high tenacity of the limpets’ adhesive system. In this study, we test this conclusion using an actual limpet. The shell of Lottia gigantea differs substantially from the hydrodynamic optimum in that its apex is displaced anteriorly to form a plough, which is used to defend the limpet’s territory. The hydrodynamic effects of this shape are similar to those observed in conical models: the animal experiences an increased lift when facing into the flow and a decreased lift when the flow is at its back. However, neither effect has a substantial impact on the risk of dislodgment. When the animal is stationary, its adhesion to the substratum is very strong, and its risk of being dislodged is small regardless of its orientation to the flow and despite its sub-optimal shape. In contrast, when the animal is crawling rapidly, its adhesion is substantially decreased, and it would probably be dislodged by rapid flow even if the shell were shaped optimally. The risk of dislodgment by waves is therefore functionally independent of shell shape. In essence, despite the extremely high water velocities to which this species is subjected, its shell has had the ‘permission’ of the flow environment to respond to other selective factors, in particular those associated with its aggressive, territorial behavior. The result is a shell that is both a potent territorial weapon and a functional (albeit less than optimal) hydrodynamic shape.
Blocking and the detection of odor components in blends
Authors: Hosler Jay S. , Smith Brian H. 
Published: April 2021

ABSTRACT
Recent studies of olfactory blocking have revealed that binary odorant mixtures are not always processed as though they give rise to mixture-unique configural properties. When animals are conditioned to one odorant (A) and then conditioned to a mixture of that odorant with a second (X), the ability to learn or express the association of X with reinforcement appears to be reduced relative to animals that were not preconditioned to A. A recent model of odor-based response patterns in the insect antennal lobe predicts that the strength of the blocking effect will be related to the perceptual similarity between the two odorants, i.e. greater similarity should increase the blocking effect. Here, we test that model in the honeybee Apis mellifera by first establishing a generalization matrix for three odorants and then testing for blocking between all possible combinations of them. We confirm earlier findings demonstrating the occurrence of the blocking effect in olfactory learning of compound stimuli. We show that the occurrence and the strength of the blocking effect depend on the odorants used in the experiment. In addition, we find very good agreement between our results and the model, and less agreement between our results and an alternative model recently proposed to explain the effect.
Estimation of the rate of oxygen consumption of the common eider duck (Somateria Mollissima), With some measurements of heart rate during voluntary dives
Authors: Hawkins P. A. J. , Butler P. J. , Woakes A. J. , Speakman J. R. 
Published: April 2021

ABSTRACT
The relationship between heart rate (fH) and rate of oxygen consumption (V˙O2) was established for a marine diving bird, the common eider duck (Somateria mollissima), during steady-state swimming and running exercise. Both variables increased exponentially with speed during swimming and in a li.near fashion during running. Eleven linear regressions of V˙O2 (ml kg-1 min_1) on fH (beats min_1) were obtained: five by swimming and six by running the birds. The common regression was described by V˙O2=10.1+0.15 fH (r2=0.46, N=272, P&lt;0.0001). The accuracy of this relationship for predicting mean V˙O2was determined for a group of six birds by recording fHcontinuously over a 2-day period and comparing estimated V˙O2obtained using the common regression with (i) V˙O2estimated using . the doubly labelled water technique (DLW) and (ii) V˙O2 measured using respirometry. A two-pool model produced the most accurate estimated V˙O2using DLW. Because of individual variability within mean values of V˙O2estimated using both techniques, there was no significant difference between mean V˙O2 estimated using fH or DLW and measured V˙O2values (P&gt;0.2), although individual errors were substantially less when fH was used rather than DLW to estimate V˙O2. Both techniques are, however, only suitable for estimating mean V˙O2for a group of animals, not for individuals.
Heart rate and behaviour were monitored during a bout of 63 voluntary dives by one female bird in an indoor tank 1.7 m deep. Tachycardia occurred both in anticipation of and following each dive. Heart rate decreased before submersion but was above resting values for the whole of the dive cycle. Mean fH at mean dive duration was significantly greater than fH while swimming at maximum sustain.able surface speeds. Heart rate was used to estimate mean V˙O2 during the dive cycle and to predict aerobic dive limit (ADL) for shallow dives.
Comparative study of tongue protrusion in three iguanian lizards, Sceloporus Undulatus, Pseudotrapelus Sinaitus and Chamaeleo Jacksonii
Authors: Meyers Jay J. , Nishikawa Kiisa C. 
Published: April 2021

ABSTRACT
The goal of this study was to investigate the function of the hyolingual muscles used during tongue protraction in iguanian lizards. High-speed videography and nerve-transection techniques were used to study prey capture in the iguanid Sceloporus undulatus, the agamid Pseudoptrapelus sinaitus and the chameleonid Chamaeleo jacksonii. Denervation of the mandibulohyoideus muscle slips had an effect only on P. sinaitus and C. jacksonii, in which tongue protrusion or projection distance was reduced. In C. jacksonii, denervation of the M. mandibulohyoideus completely prevented little hyoid protraction. Denervation of the M. verticalis had no effect on S. undulatus, but reduced tongue protrusion distance in P. sinaitus. Denervation of the accelerator muscle in C. jacksonii inhibited tongue projection completely. The function of the M. mandibulohyoideus and M. verticalis has become increasingly specialized in P. sinaitus and especially in C. jacksonii to allow greater tongue protrusion. The combined results of these treatments suggest that these three groups represent transitional forms, both morphologically and functionally, in the development of a projectile tongue.
The mechanics of locomotion in the squid Loligo Pealei: Locomotory function and unsteady hydrodynamics of the jet and intramantle pressure
Authors: Anderson Erik J. , Demont M. Edwin 
Published: April 2021

ABSTRACT
High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects.
Squid were observed to eject up to 94% of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.
The Hind Wing of the Desert Locust (Schistocerca Gregaria Forskål): II. Mechanical Properties and Functioning of the Membrane
Authors: Smith C. W. , Herbert R. , Wootton R. J. , Evans K. E. 
Published: April 2021

ABSTRACT
As part of an investigation of the functional mechanics of the hind wing of the desert locust Schistocerca gregaria, the Young’s modulus of the membrane was measured using a newly developed universal materials test machine capable of testing very small specimens of cuticle, down to 1 mm gauge length. Strain was measured optically. Specimens were cut from various locations around the wing and tested under controlled temperature and humidity. The modulus of the membrane was typically between 1 and 5 GPa, but both this and the membrane thickness varied around the wing, with the remigium and the anal fan showing markedly different properties. The membrane was tested for chitin using two methods: a gas pyrolysis/mass spectrometry assay, and a gold-labelled immunoassay specific to chitin. None was detected, and the membrane may consist of epicuticle alone. The wings were examined for evidence of crystalline material using standard polarising microscopy and an advanced technique that distinguishes between three components of the polarised image. Birefringence was detected in the membrane of the anterior part of the wing, but vanished when the membrane was separated from the surrounding veins, suggesting that it was due to pre-stress rather than to ultrastructure. The implications are discussed.
The Hind Wing of the Desert Locust (Schistocerca Gregaria Forskål): III. A Finite Element Analysis of a Deployable Structure
Authors: Herbert R. C. , Young P. G. , Smith C. W. , Wootton R. J. , Evans K. E. 
Published: April 2021

ABSTRACT
Finite element analysis is used to model the automatic cambering of the locust hind wing during promotion: the umbrella effect. It was found that the model required a high degree of sophistication before replicating the deformations found in vivo. The model has been validated using experimental data and the deformations recorded both in vivo and ex vivo. It predicts that even slight modifications to the geometrical description used can lead to significant changes in the deformations observed in the anal fan. The model agrees with experimental data and produces deformations very close to those seen in free-flying locusts. The validated model may be used to investigate the varying geometries found in orthopteran anal fans and the stresses found throughout the wing when loaded.
Characterisation of the H+/Peptide Cotransporter of eel Intestinal Brush-Border Membranes
Authors: Verri Tiziano , Maffia Michele , Danieli Antonio , Herget Martina , Wenzel Uwe , Daniel Hannelore , Storelli Carlo 
Published: April 2021

ABSTRACT
H+/peptide cotransport in brush-border membrane vesicles (BBMVs) from eel (Anguilla anguilla) intestine was studied by measuring D-[3H]-phenylalanyl-L-alanine uptake and by monitoring peptide-dependent intravesicular acidification using the pH-sensitive dye Acridine Orange. D-[3H]-phenylalanyl-L-alanine influx was greatly stimulated by an inside-negative membrane potential and enhanced by an inwardly directed H+ gradient. In parallel, vesicular H+ influx was significantly increased in the presence of extravesicular D-phenylalanyl-L-alanine or a series of glycyl and L-prolyl peptides. H+/peptide cotransport displayed saturable kinetics involving a single carrier system with apparent substrate affinities of 0.9–2.6 mmol l−1 depending on the particular peptide. All substrates tested competed with this system.
Pre-incubation of BBMVs with dipeptides prevented diethylpyrocarbonate inhibition of transport activity, suggesting that the substrates mask histidine residues involved in the catalytic function of the transporter. Using human PepT1-specific primers, a reverse transcription–polymerase chain reaction (RT-PCR) signal was detected in eel intestine. Our results suggest that, in eel intestine, a brush-border membrane ‘low-affinity’-type H+/peptide cotransport system is present that shares kinetic features with the mammalian intestinal PepT1-type transporters.
Improvement in the Efficiency of Oxidative Phosphorylation in the Freshwater eel Acclimated to 10.1 MPa Hydrostatic Pressure
Authors: Theron Michaël , Guerrero François , Sébert Philippe 
Published: April 2021

ABSTRACT
Previous studies have suggested that the efficiency of oxidative phosphorylation in the freshwater eel (Anguilla anguilla) is increased after acclimation to high hydrostatic pressure. Analysis at atmospheric pressure of the respiratory chain complexes showed that, after 21 days at 10.1 MPa, the activity of complex II was decreased to approximately 50 % (P&lt;0.01) of the control value and that cytochrome c oxidase (complex IV) activity was significantly increased to 149 % of the control value (P&lt;0.05). ADP/O ratios calculated from mitochondrial respiration measurements were significantly increased after acclimation to high hydrostatic pressure (2.87 versus 2.52, P&lt;0.001) when measured in the presence of pyruvate plus malate at atmospheric pressure. These results clearly show an increased oxidative phosphorylation efficiency in response to high-pressure acclimation.
Hydrodynamics of Unsteady Fish Swimming and the Effects of Body Size: Comparing the Flow Fields of Fish Larvae and Adults
Authors: Müller U. K. , Stamhuis E. J. , Videler J. J. 
Published: April 2021

ABSTRACT
Zebra danios (Brachydanio rerio) swim in a burst-and-coast mode. Most swimming bouts consist of a single tail flick and a coasting phase, during which the fish keeps its body straight. When visualising the flow in a horizontal section through the wake, the effects of the flow regime become apparent in the structure of the wake. In a two-dimensional, medio-frontal view of the flow, larvae and adults shed two vortices at the tail during the burst phase. These vortices resemble a cross section through a large-core vortex ring: two vortex cores packed close together with the central flow directed away from the fish. This flow pattern can be observed in larvae (body length approximately 4 mm) at Reynolds numbers below 100 as well as in adult fish (body length approximately 35 mm) at Reynolds numbers above 1000. Larval vortices differ from those of adult zebra danios mainly in their relatively wider vortex cores (higher ratio of core radius to ring radius) and their lower vortex circulation. Both effects result from the increased importance of viscosity on larval flows. During the coasting phase, larval and adult flows again differ because of the changing importance of viscosity. The high viscosity of the water causes large vortical flows adjacent to the larva”s body. These regions of high vorticity represent the huge body of water dragged along by the larva, and they cause the larva to stop almost immediately after thrust generation ceases. No such areas of high vorticity are visible adjacent to adult zebra danios performing a comparable swimming manoeuvre. The rapid decrease in vortex circulation and the severe reduction in the coasting distance due to viscous drag contribute to the high cost that larvae – unlike adult fish – face when using a burst-and-coast swimming style.
Na+ and Ca2+ Pumps in the Gills, Epipodites and Branchiostegites of the European Lobster Homarus Gammarus: Effects of Dilute Sea Water
Authors: Flik Gert , Haond Christophe 
Published: April 2021

ABSTRACT
Crude homogenates and plasma-membrane-enriched fractions were prepared from the epithelium of the gills, epipodites and branchiostegites of intermoult European lobsters Homarus gammarus, and Na+/K+-ATPase, Ca2+-ATPase and Na+/Ca2+ exchange activities were quantified in these tissues. Lobsters were kept in sea water (salinity 35 ‰) or were adapted to dilute sea water (22.1 ‰). The lobster hyperregulates haemolymph osmolarity and Ca2+ levels in both media. Homogenates of the podobranchs, arthrobranchs and pleurobranchs had comparable Na+/K+-ATPase specific activities, and mean activities increased significantly for all three types of gills when the animals were kept in dilute sea water. In the epipodites and branchiostegites, Na+/K+-ATPase specific activities exceeded those in the gills, and exposure to dilute sea water greatly enhanced these activities. In sea water, 80 % of the total Na+/K+-ATPase activity is associated with the gills and epipodites (each tissue containing 40 %) and 20 % with the branchiostegites; in dilute sea water, the gills contained approximately 25 %, the epipodites 40 % and the branchiostegites approximately 35 % of the total activity, indicating the relative importance of the epipodites and branchiostegites for ionic hyperregulation in dilute media. In plasma membrane vesicles isolated from the gills, epipodites and branchiostegites, Ca2+ transport driven by ATP and by a Na+ gradient was demonstrated. Exposure to dilute sea water enhanced Na+/Ca2+ exchange and Ca2+-ATPase activities in the epipodites and branchiostegites; in the gills, however, Ca2+ transport activities decreased. The role of these tissues and enzymes in Na+ and Ca2+ handling by the lobster is discussed.
Time of Contact and Step Length: the Effect of Limb Length, Running Speed, Load Carrying and Incline
Authors: Hoyt Donald F. , Wickler Steven J. , Cogger Edward A. 
Published: April 2021

ABSTRACT
Using published values for twelve species of birds and mammals, we investigated the effects of limb length and running speed on time of contact and step length. In addition, we measured the time of contact in horses trotting up a 10 % incline and when carrying a load averaging 19 % of their body mass. From these values, we calculated stride period and step length. Our analysis of the interspecific data yielded the following relationship between time of contact (tc in s) and leg length (L in m) and running speed (v in m s−1): tc=0.80L0.84/v0.87 (r2=0.97). Both exponents in this relationship are significantly different from 1.0, indicating that step length increases with speed and that small species use a step length that, relative to their leg length, is longer than the relative step length used by larger species. Time of contact increased when a horse carried a load but not when it trotted up an incline.
Phenotypic Effects of Leptin in an Ectotherm: A New Tool to Study the Evolution of Life Histories and Endothermy?
Authors: Niewiarowski Peter H. , Balk Michelle L. , Londraville Richard L. 
Published: April 2021

ABSTRACT
Leptin is a hormone that regulates energy expenditure and body mass in mammals, and it has attracted considerable attention because of its potential in treating human obesity. Comprehensive data from both pathological and non-pathological systems strongly support a role for leptin in regulating energy metabolism, in thermoregulation and in regulating the onset of puberty. We report here that daily injections of recombinant murine leptin in fence lizards (Sceloporus undulatus) produce phenotypic effects similar to those observed when leptin injections are given to mice. Lizards injected with leptin had body temperatures 0.6 °C higher, ate 30 % less food and showed a 14 % reduction in activity rates, and females showed a 2.5-fold increase in resting metabolic rates, compared with lizards injected with vehicle only (phosphate-buffered saline). We also detected native lizard leptin using an immunoassay. Our results indicate that leptin is expressed in ectotherms and may be conserved both functionally and structurally. In the wake of unprecedented research activity on the role of leptin as a cause of, and potential treatment for, human obesity, we believe that other applications of leptin research have been ignored. For example, the response of lizards to leptin injection in our study has important implications for two broad areas of research in evolutionary biology: the evolution of age at first reproduction and of endothermy. We argue that research in these areas, previously limited to comparative approaches, may now benefit from experimental manipulations using leptin.