bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aquatic Surface Respiration, Buoyancy Control and the Evolution of Air-Breathing in Gobies (Gobiidae: Pisces)
Authors: Gee John H. , Gee Phyllis A. 
Published: April 2021

ABSTRACT
The role of a buccal gas bubble, held while performing aquatic surface respiration (ASR; ventilating the gills with surface water during hypoxia), was examined in benthic, intertidal Australian gobies (Favonigobius tamarensis, F. exquisitus, Pseudogobius olorum, Chlamydogobius sp., Mugilogobius paludis, Cryptocentroides cristatus and Arenigobius bifrenatus). Analyses of the forces of lift and weight of the head and body during ASR indicate a hydrostatic role for the bubble. During ASR, lift from the bubble was sufficient to provide neutral or positive buoyancy to the head, anchoring the mouth at the water surface. A buoyancy role was confirmed by experiments demonstrating the ability of some species to alter bubble volume, to compensate either for different body positions or for water densities (salinities). Use of the bubble for aerial respiration by Cryptocentroides, Mugilogobius, Chlamydogobius and Arenigobius was confirmed in hypoxia by the presence of blood-filled capillaries in the buccal subepithelium (mean air-blood barrier less than 30 μm) in areas of the buccal cavity that contacted the bubble. Blood-filled capillaries were rare or absent in normoxia in all species except Mugilogobius. Cutaneous respiration was inferred from the presence of blood-filled capillaries in the dermis and epidermis of emersed portions of the head in Mugilogobius, Chlamydogobius and Arenigobius. The buccal bubble has respiratory and hydrostatic roles and there is support for the hypothesis that ASR and the buoyancy regulation (air-gulping) required to perform it effectively are prerequisite steps in the evolution of air-breathing in these gobies.
Bacillus Thuringiensis δ-Endotoxin And Larval Manduca Sexta Midgut Brush-Border Membrane Vesicles Act Synergistically To Cause Very Large Increases In The Conductance Of Planar Lipid Bilayers
Authors: Martin Francis G. , Wolfersberger Michael G. 
Published: April 2021

ABSTRACT
Brush-border membrane vesicles prepared from midguts of Manduca sexta larvae were incorporated into planar phospholipid bilayers. Addition of Bacillus thuringiensis δ-endotoxin to the buffered salt solutions bathing these bilayers resulted in large irreversible increases in conductance. At pH 9.6, the smallest toxin-dependent increase in bilayer conductance observed was 13 nS. Similar conductance increases were never observed in the absence of δ-endotoxin or in δ-endotoxin-treated bilayers not containing components of insect brush-border membranes.
Magnetic Orientation of Spiny Lobsters in the Ocean: Experiments with Undersea Coil Systems
Authors: Lohmann Kenneth J. , Pentcheff N. Dean , Nevitt Gabrielle A. , Stetten George D. , Zimmer-Faust Richard K. , Jarrard Hugh E. , Boles Larry C. 
Published: April 2021

ABSTRACT
The western Atlantic spiny lobster Panulirus argus undergoes an annual migration and is also capable of homing to specific dens in its coral reef environment. Relatively little is known, however, about the orientation cues that lobsters use to guide their movements. To determine whether lobsters can orient to the earth’s magnetic field, divers monitored the orientation of lobsters tethered inside magnetic coil systems submerged offshore in the Florida Keys, USA. Each coil could be used to reverse either the horizontal or vertical component of the earth’s field.
Tethered lobsters walking inside the coils often established and maintained consistent courses towards specific directions. After a lobster had established a course, it was exposed to one of three conditions: (1) a reversal of the horizontal component of the earth’s field; (2) a reversal of the vertical component of the earth’s field; or (3) no change in the ambient field (controls). Lobsters subjected to the horizontal field reversal deviated significantly from their initial courses. In contrast, control lobsters and those subjected to the reversed vertical field did not.
These results demonstrate that spiny lobsters possess a magnetic compass sense. Because inverting the vertical component of the earth’s field had no effect on orientation, the results suggest that the lobster compass is based on field polarity and thus differs from the inclination compasses of birds and sea turtles. The magnetic compass of lobsters may function in homing behavior, in guiding the autumn migration or in both.
Recovery of Function, Peripheral Sensitization and Sensory Neurone Activation by Novel Pathways Following Axonal Injury in Aplysia Californica
Authors: Dulin Michael F. , Steffensen Isabella , Morris Catherine E. , Walters Edgar T. 
Published: April 2021

ABSTRACT
Recovery of behavioural and sensory function was examined following unilateral pedal nerve crush in Aplysia californica. Nerve crush that transected all axons connecting the tail to the central nervous system (CNS) eliminated the ipsilateral tail-evoked siphon reflex, whose sensory input travels in the crushed tail nerve (p9). The first reliable signs of recovery of this reflex were observed within 1 week, and most animals displayed tail-evoked siphon responses within 2 weeks. Wide-dynamic-range mechanosensory neurones with somata in the ventrocaudal (VC) cluster of the ipsilateral pleural ganglion exhibited a few receptive fields (RFs) on the tail 3 weeks after unilateral pedal nerve crush, indicating that the RFs had either regenerated or been reconnected to the central somata. These RFs were smaller and sensitized compared with corresponding RFs on the contralateral, uncrushed side. Centrally conducted axon responses of VC sensory neurones to electrical stimulation distal to the nerve crush site did not reappear until at least 10 days after the crush. Because the crush site was much closer to the CNS than to the tail, the failure of axon responses to be restored earlier than the behavioural responses indicates that early stages of reflex recovery are not due to regeneration of VC sensory neurone axons into the tail. Following nerve crush, VC sensory neurones often could be activated by stimulating central connectives or peripheral nerves that do not normally contain the sensory neurone’s axons. These results suggest that recovery of behavioural function after nerve injury involves complex mechanisms, including regenerative growth of axotomized VC sensory neurones, sensitization of regenerating RFs and sprouting of VC sensory neurone fibres within the CNS. Furthermore, the rapidity of behavioural recovery indicates that its initial phases are mediated by additional mechanisms, perhaps centripetal regeneration of unidentified sensory neurones having peripheral somata, or transient reconnection of proximal and distal stumps of axotomized VC cells.
Adenylate Compartmentation and Storage in Coelomic Cells of the Polychaete Nereis Virens
Authors: Hoeger U. , Dunn J. F. , Märker C. 
Published: April 2021

ABSTRACT
The concentrations of adenine nucleotides (AMP, ADP, ATP) were determined in coelomic cells (eleocytes) of the polychaete Nereis virens. In cells of immature and male animals, total ADP and AMP contents (each 10–15 μmol ml−1 packed cell volume) greatly exceeded that of ATP (0.8 μmol ml−1 packed cell volume). 31P-nuclear magnetic resonance (NMR) studies of living eleocytes showed that the high concentrations of both AMP and ADP are free in solution. Comparisons of in vivo NMR spectra with those obtained from metabolite extracts of eleocytes suggest that the adenylate pools are compartmentalized, with a large pool being in an environment with a pH&lt;6.0 and a small pool being in a domain where pH&gt;6.7. This indicates that eleocytes are capable of storing high concentrations of ADP and AMP without inhibiting energy metabolism by sequestering these compounds into an acidic compartment. The large acidic vacuole characteristic of eleocytes may function as this compartment.
Large-Scale Changes in Thermal Sensitivity of Flight Performance During Adult Maturation in a Dragonfly
Authors: Marden James H. 
Published: April 2021

ABSTRACT
Newly emerged adult dragonflies are physiologically immature in a number of ways, including the mass, ultrastructure and biochemistry of their flight muscles. In Libellula pulchella dragonflies, adult maturation of flight muscle is accompanied by striking changes in thermal physiology. Vertical force production during fixed flight attempts in newly emerged adults (tenerals) shows a broad plateau of near-peak performance, first attained at cool thoracic temperatures (typically 28–34 °C) and maintained up to thoracic temperatures of 40–45 °C [mean optimal thoracic temperature (OTT)=34.6 °C; mean upper lethal temperature (ULT)=45.3 °C]. In contrast, fully mature adults show narrow thermal sensitivity curves, wherein peak performance is approached only within a few degrees of the thermal optimum, which invariably occurs at hot thoracic temperatures (38–50 °C; mean OTT=43.5 °C; mean ULT=48.6 °C). These changes in the shape and position of thermal performance curves are compared with predictions from hypotheses for the evolution of thermal sensitivity.
Energetic Consequences of Flight Speeds of Foraging Red and Hoary Bats (Lasiurus Borealis and Lasiurus Cinereus; Chiroptera: Vespertilionidae)
Authors: Cueva Salcedo Horacio De La , Fenton M. Brock , Hickey M. Brian C. , Blake Robert W. 
Published: April 2021

ABSTRACT
We used Doppler radar readings of the flight speeds of foraging, lactating female Lasiurus borealis (N=826) and Lasiurus cinereus (N=544) to test morphologically based predictions about their flight performance. Both species flew at speeds (V=6.7 and 7.7 m s−1, respectively) that differed significantly from predicted minimum power speed (Vmp ; 4.0 and 5.08 m s−1, respectively) or predicted maximum range speed (Vmr ; 5.25 and 6.69 m s−1, respectively), perhaps reflecting the active pursuit of moths performing evasive manoeuvres. Estimates of costs of flight and lactation are combined with data on prey size together with encounter and capture rates to illustrate the energetic benefits accruing to these species when they forage in concentrations of insects.
Sensitivity of the Mystacial Vibrissae of Harbour Seals (Phoca Vitulina) For Size Differences of Actively Touched Objects
Authors: Dehnhardt G. , Kaminski A. 
Published: April 2021

ABSTRACT
We studied the capability of one male and one female harbour seal Phoca vitulina to discriminate diameter differences of circular discs by means of active touch with their mystacial vibrissae. To prevent the animals from perceiving visual information, they were blindfolded during trials. In a two-alternative forced-choice procedure, the seals were required to choose the larger of two Perspex discs. Weber fractions c (the ratio of the lowest diameter difference detected by the seals on 75 % of occasions to the starting disc diameter D, ΔD/D=c) were determined for three standard discs (diameters 1.12 cm, 5.04 cm and 8.74 cm) by the psychophysical method of limits. While the seals achieved Weber fractions of 0.29 (male) and 0.26 (female) at the smallest standard disc, their performance improved with increasing disc size, resulting in an approximately constant Weber fraction of 0.13 (male) and 0.08 (female) for the two larger standard discs. The difference in performance between the two seals did not reflect a real difference in sensitivity, but may best be explained by a difference in choice behaviour. As a measure of tactile acuity, the Weber fractions obtained for the larger standard discs indicate that harbour seals can use their mystacial vibrissae as efficiently for active touch as monkeys use their hands.
Simultaneous Control of Head and Thoracic Temperature by the Green Darner Dragonfly Anax Junius (Odonata: Aeshnidae)
Authors: May Michael L. 
Published: April 2021

ABSTRACT
Anax junius is a large dragonfly that regulates thoracic temperature (Tth) during flight. This species, like several other intermittently endothermic insects, achieves control of Tth at least in part by increasing circulation of hemolymph to the abdomen at high air temperature (Ta), thus facilitating heat loss from the thorax. In this paper, I demonstrate that heat transfer to the head is also under active control, very probably owing to temperature-sensitive alteration of hemolymph circulation. As a result, head temperature (Th) is strikingly elevated above Ta during endothermic warm-up and flight. Furthermore, during unrestrained flight in the field, Th is regulated actively by increasing hemolymph circulation from the warm thorax at low Ta. Concurrent measurements of abdominal temperature (Tab) confirm that the abdomen is used as a ‘thermal window’ at Ta&gt;30 ˚C but apparently not at lower Ta; thus, some additional mechanism(s) must exist for regulation of Tth at low Ta.
Haemoglobin function in intact lamprey erythrocytes: interactions with membrane function in the regulation of gas transport and acid–base balance
Authors: Nikinmaa Mikko , Airaksinen Susanna , Virkki Leila V. 
Published: April 2021

ABSTRACT
Haemoglobin function within lamprey erythrocytes offers a unique solution to gas transport among vertebrates. Lamprey haemoglobin within intact erythrocytes is in oligomer/monomer equilibrium and has an oxygen affinity similar to that of haemoglobin in other active fishes. The cooperativity of oxygen binding, which is reduced at low pH values, the effect of protons and the effect of the concentration of haemoglobin on its oxygen affinity are all due to dissociation/association reactions of the haemoglobin molecules. The permeability of the lamprey red cell membrane to acid and base equivalents is very low, and plasma bicarbonate cannot therefore be dehydrated to carbon dioxide to any significant extent during the residence time of blood in the gills. This potential limitation on carbon dioxide excretion is overcome, however, by the high intraerythrocytic pH and the marked oxygenation-linked pH changes in the erythrocyte, which are due to the large Haldane effect of the haemoglobin. Owing to the relative impermeability of the erythrocyte membrane to acid equivalents, intraerythrocytic haemoglobin cannot take part in the acid–base buffering of the extracellular compartment. As a consequence, extracellular acid loads cause marked fluctuations in plasma pH.
Developmental changes in oxygen consumption regulation in larvae of the South African clawed frog Xenopus Laevis
Authors: Hastings Dulynn , Burggren Warren 
Published: April 2021

ABSTRACT
Well-developed larval Xenopus laevis (NF stages 58–66) are oxygen regulators, at least during mild hypoxia. When and how they change from oxygen conformers (the presumed condition of the fertilized egg) to oxygen regulators is unknown. Also unknown is how anaerobic metabolic capabilities change during development, especially in response to acute hypoxia, and to what extent, if any, anaerobiosis is used to supplement aerobic metabolism. Consequently, we have investigated resting rates of oxygen consumption and concentrations of whole-body lactate (lactic acid) during development in normoxia and in response to acute hypoxia in Xenopus laevis. increased in an episodic, non-l inear fashion during development. Resting, normoxic increased about tenfold (to approximately 0.20 μmol g−1 h−1) between NF stages 1–39 and 40–44, and then another tenfold between NF stages 45–48 and 49–51 (to approximately 2.0 μmol g−1 h−1), remaining at about 2 μmol g−1 h−1 for the remainder of larval development. reached its highest level in newly metamorphosed frogs (nearly 4 μmol g−1 h−1), before decreasing to about 1.0 μmol g−1 h−1 in large adults. X. laevis embryos and larvae up to NF stage 54–57 were oxygen conformers when exposed to variable levels of acute hypoxia. The only exception was NF stage 45–48 (external gills present yet body mass still very small), which showed some capability of oxygen regulation. All larvae older than stage 54–57 and adults were oxygen regulators and had the lowest values of Pcrit (the oxygen partial pressure at which begins to decline). Whole-body lactate concentration in normoxia was about 1 μmol g−1 for all larval groups, rising to about 12 μmol g−1 in adults. Concentrations of lactic acid in NF stages 1–51 were unaffected by even severe ambient hypoxia. However, whole-body lactate levels in NF stages 52–66 increased in response to severe hypoxia, indicating that some anaerobic metabolism was being used to supplement diminishing aerobic metabolism. The largest increases in concentration of lactate occurred in late larvae and adults.
Immunolocalization of proton pumps (H+-ATPase) in pavement cells of rainbow trout gill
Authors: Sullivan Gary V. , Fryer James N. , Perry Steve F. 
Published: April 2021

ABSTRACT
The expression of the V-type proton ATPase (H+-ATPase) was examined in the gill of the freshwater rainbow trout (Oncorhynchus mykiss) using immunocytochemistry in concert with laser scanning confocal or electron microscopy. A synthetic peptide consisting of the carboxy-terminal region of the 31 kDa subunit of the bovine renal H+-ATPase was used to generate an antiserum in rabbits, and its suitability for use in trout gill was confirmed by western blotting.
Gill epithelial cells demonstrated specific immunoreactivity, the intensity of which was increased markedly after 18 h of exposure to hypercapnia (1 % CO2 in air). The increased intensity of H+-ATPase immunoreactivity was associated with elevated branchial net acid excretion. In the hypercapnic fish, the specific immunoreactivity was associated with both the apical membrane and cytoplasm. Electron microscopy revealed that specific immunoreactivity was localized to the pavement cells and was particularly associated with the apical membrane and subapical cytoplasmic vesicles.
The increased H+-ATPase immunoreactivity in the epithelial cells of hypercapnic fish and the increased intensity of the immunoreactive bands in western blots from hypercapnic fish demonstrate an ‘up-regulation’ of this protein in response to respiratory acidosis. The results are discussed with reference to current models of acid–base and ion regulation in the gill of freshwater fish.
The Effect of Cycle Frequency on the Power Output of Rat Papillary Muscles in vitro
Authors: Layland Joanne , Young Iain S. , Altringham John D. 
Published: April 2021

ABSTRACT
Papillary muscles were isolated from the right ventricles of rats and the length for maximum active force generation (Lmax) was determined isometrically. The work loop technique was used to derive the length for maximum work production (Lopt) at the cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output. Lopt was typically 7% shorter than Lmax and within the physiological length range (87.5%Lmax to Lmax). Net work and power output were measured during sinusoidal strain cycles around Lopt, over the cycle frequency range 1–9 Hz, strain amplitude and phase shift being optimised for work and power at each frequency. Experiments were performed at 37°C.
Distinct optima were found in both the work–frequency and the power–frequency relationships. The optimum cycle frequency for net work production was lower than the frequency for maximum power output. The mean maximum power output at 37°C was 8.62±0.50 W kg−1 (mean ± S.E.M., N=9) and was achieved at a cycle frequency of approximately 6 Hz, close to the estimated resting heart rate of 5.8 Hz for the rats used (mean mass 223±25 g). The cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output produced an in vitro contraction closely simulating the basal in vivo contraction.
Atmospheric Controls On Elephant Communication
Authors: Garstang Michael , Larom David , Raspet Richard , Lindeque Malan 
Published: April 2021

ABSTRACT
Atmospheric conditions conducive to long-range transmission of low-frequency sound as used by elephants are found to exist in the Etosha National Park in Namibia during the late dry season. Meteorological measurements show that strong temperature inversions form at the surface before sunset and decay with sunrise, often accompanied by calm wind conditions during the early evening. These observations are used in an acoustic model to determine the sensitivity of infrasound to the effects of (a) the strength, thickness and elevation of temperature inversions, and (b) the growth and decay of an inversion typical of dry, elevated African savannas. The results suggest that the range over which elephants communicate more than doubles at night. Optimum conditions occur 1–2 h after sunset on clear, relatively cold, calm nights. At these times, ranges of over 10 km are likely, with the greatest amplification occurring at the lowest frequency tested. This strong diurnal cycle in communication range may be reflected in longer-lasting changes in weather and may exert a significant influence on elephant behaviour on time scales from days to many years.
Perception of Ocean Wave Direction by Sea Turtles
Authors: Lohmann Kenneth J. , Swartz Andrew W. , Lohmann Catherine M. F. 
Published: April 2021

ABSTRACT
At the beginning of their offshore migration, hatchling sea turtles enter the ocean at night and establish a course away from land by swimming directly into oceanic waves. How turtles can detect wave direction while swimming under water in darkness, however, has not been explained.
Objects in a water column beneath the surface of the ocean describe a circular movement as waves pass above. In principle, swimming turtles might, therefore, detect wave direction by monitoring the sequence of accelerations they experience under water. To determine whether loggerhead (Caretta caretta L.) and green turtle (Chelonia mydas L.) hatchlings can detect wave direction in this way, we constructed a wave motion simulator to reproduce in air the circular movements that occur beneath small ocean waves. Hatchlings suspended in air and subjected to movements that simulated waves approaching from their right sides attempted to turn right, whereas movements that simulated waves from the left elicited left-turning behavior. Movements simulating waves from directly in front of the turtles elicited little turning in either direction.
The results demonstrate that hatchling sea turtles can determine the propagation direction of ocean waves by monitoring the circular movements that occur as waves pass above. Although sea turtles are the first animals shown to be capable of detecting wave direction in this way, such an orientation mechanism may be widespread among other transoceanic migrants such as fish and cetaceans.