bluuebunny/crossref_metadata_2025 huggingface dataset:
Mental Rotation in A California Sea Lion (Zalophus Californianus)
Authors: Mauck B. , Dehnhardt G.
Published: April 2021

Mental rotation is a widely accepted concept that suggests an analogue mode of visual information-processing in certain visuospatial tasks. Typically, these tasks demand the discrimination between the image and mirror-image of rotated figures, for which human subjects need an increasing reaction time depending on the angular disparity between the rotated figures. In pigeons, tests of this kind yielded a time-independent rotational invariance, suggested as being the result of a non-analogue information-processing that has evolved in response to the horizontal plane that birds perceive from above while flying. Given that marine mammals use the water surface as the horizontal plane for orientation while diving, the ability of a California sea lion to mentally rotate two-dimensional shapes was tested. Using a successive two-alternative matching-to-sample procedure, the animal had to decide between the image and mirror-image of a previously shown sample. Both stimuli were rotated by a multiple of 30 ° with respect to the sample. The animal’s reaction time was measured by a computer-controlled touch-screen device, rewarding the animal for pressing its snout against the stimulus matching the sample. A linear regression analysis of the animal’s mean reaction time against the angular rotation of the stimulus yielded a significant correlation coefficient. Thus, the present data can be explained by the mental rotation model, predicting an image-like representation of visual stimuli in this species. The present results therefore correspond well with those found for human subjects, but are inconsistent with the data reported for pigeons.
Measurement of the Threshold Sensitivity of Honeybees to Weak, Extremely Low-Frequency Magnetic Fields
Authors: Kirschvink Joseph L. , Padmanabha S. , Boyce C. K. , Oglesby J.
Published: April 2021

Experiments reported previously demonstrate that free-flying honeybees are able to detect static intensity fluctuations as weak as 26 nT against the background, earth-strength magnetic field. We report here an extension of this work to weak, alternating fields at frequencies of 10 and 60 Hz. Our results indicate that the sensitivity of the honeybee magnetoreception system decreases rapidly with increasing frequency. At 60 Hz, alternating field strengths above 100 μT are required to elicit discrimination. These results are consistent with biophysical predictions of a magnetite-based magnetoreceptor.
Predictions of the Time Course of Force and Power Output by Dogfish White Muscle Fibres During Brief Tetani
Authors: Curtin N. A. , Gardner-Medwin A. R. , Woledge R. C.
Published: April 2021

The aim of this study was to identify the principal factors that determine the time course of force and power output by muscle during patterns of stimulation and movement similar to those during fish swimming. Fully activated, white muscle fibres isolated from dogfish Scyliorhinus canicula were used to characterize the force–velocity relationship of the contractile component (CC) and the stress–strain relationship of the passive, elastic component (SEC) in series with the CC. A simple model of the time course of crossbridge activation during brief contractions was devised. Using the mechanical properties of the CC and SEC and the activation time course, force and power were predicted for brief contractions with constant-velocity movement and also for brief contractions starting at various times during sinusoidal movement. The predicted force and power were compared with observations for these patterns of stimulation and movement. The predictions matched the observations well for the period during stimulation. Matching of force was much less good for some specific conditions during relaxation, the period during which force persists after the end of stimulation. If either the slow rise of activation or the SEC was omitted from the calculation, the predictions were poor, even during stimulation. Additional factors which may influence force are discussed. These include the after-effects of shortening and stretch, the variation of force during constant-velocity stretch and non-uniform behaviour within the muscle.
Collagen Orientation and Molecular Spacing During Creep and Stress-Relaxation in Soft Connective Tissues
Authors: Purslow Peter P. , Wess Tim J. , Hukins David W. L.
Published: April 2021

Collagen fibres form cross-helical, cross-ply or quasi-random feltworks in extensible connective tissues; strain-induced reorientation of these networks gives rise to the non-linear mechanical properties of connective tissue at finite strains. Such tissues are also generally viscoelastic (i.e. display time-dependent properties). The hypothesis that time-dependent reorientation of collagen fibres is responsible for the viscoelasticity of such tissues is examined here using time-resolved X-ray diffraction measurements during stress-relaxation and creep transients applied to rat skin and bovine intramuscular connective tissue. Differences in the intensity and angular orientation of the third and fifth orders of the 67 nm meridional D-spacing of collagen molecules were shown before and after the application of loads or displacements. However, no changes in the D-spacing or angular orientation of collagen occurred during the time course of either stress-relaxation or creep in both tissues. This indicates that collagen fibre reorientation is not a primary source of their viscoelastic properties. The non-linear (strain-dependent) nature of the stress-relaxation response in these tissues suggests that relaxation processes within the collagen fibres or at the fibre–matrix interface may be responsible for their viscoelastic nature.
Representation of Behaviorally Relevant Sound Frequencies by Auditory Receptors in the Cricket Teleogryllus Oceanicus
Authors: Pollack Gerald S. , Faulkes Zen
Published: April 2021

Teleogryllus oceanicus is particularly sensitive to two ranges of sound frequency, one corresponding to intraspecific acoustical signals (4–5 kHz) and the other to the echolocation cries of bats (25–50 kHz). We recorded summed responses of the auditory nerve to stimuli in these two ranges. Nerve responses consist of trains of compound action potentials (CAPs), each produced by the summed activity of a number of receptor neurons. The amplitude of the CAP is up to four times larger for stimuli at 4.5 kHz than for stimuli at 30 kHz, suggesting either that the extracellular spikes produced by receptors that respond to 4.5 kHz are larger than those that respond to 30 kHz, or that receptors fire more synchronously in response to stimulation at 4.5 kHz, or that more receptors respond to stimulation at 4.5 kHz. Neither unit spike amplitude nor conduction velocity (which is expected to vary with spike amplitude) differs for the two frequencies, and the responses to 4.5 kHz are not produced by more tightly synchronized receptor populations, as judged by CAP breadth. We conclude that more receptors respond to 4.5 kHz than to 30 kHz.
Intergeneric Distribution and Immunolocalization of a Putative Odorant-Binding Protein in True Bugs (Hemiptera, Heteroptera)
Authors: Dickens Joseph C. , Callahan Franklin E. , Wergin William P. , Murphy Charles A. , Vogt Richard G.
Published: April 2021

Lygus antennal protein (LAP) is an olfactory-related protein of the tarnished plant bug Lygus lineolaris (Hemiptera, Heteroptera: Miridae), a hemimetabolous insect. In previous work, a polyclonal antiserum was generated against the N-terminal sequence of LAP; LAP immunoreactivity was strongest in antennae of adult males, but was also present in antennae of adult females and of nymphs. In the current study, LAP immunoreactivity was examined to determine the species specificity and the tissue and cellular localization of LAP expression. Western blot analysis indicated that LAP immunoreactivity was present in the antennae of the male congeners L. lineolaris and L. hesperous, but was not detectable in male antennae of the more distant relatives Podisus maculiventris or Nezara viridula (Hemiptera, Heteroptera: Pentatomidae). Western blot analysis further confirmed that LAP expression was restricted to antennal tissue. Histological analyses showed that LAP expression within the antennae was specifically associated with chemosensory sensilla on the antenna. Within the sensilla, LAP immunoreactivity was distributed throughout the extracellular lumen and was concentrated in dense granules within the cytoplasm of sensillar support cells. LAP immunoreactivity was restricted to a subset of antennal chemosensory sensilla, specifically the multiporous olfactory sensilla. These findings suggest that LAP has an important olfactory function in Lygus sp., possibly related to that of odorant-binding proteins (OBP) found in other insect orders. If so, LAP would be the first OBP-like protein characterized outside the Endopterygota.
Acid–Base Regulation, Metabolism and Energetics in Sipunculus Nudus As a Function of Ambient Carbon Dioxide Level
Authors: Pörtner H. O. , Reipschläger A. , Heisler N.
Published: April 2021

Changes in the rates of oxygen consumption and ammonium excretion, in intra- and extracellular acid–base status and in the rate of H+-equivalent ion transfer between animals and ambient water were measured during environmental hypercapnia in the peanut worm Sipunculus nudus. During exposure to 1% CO2 in air, intracellular and coelomic plasma values rose to levels above those expected from the increase in ambient CO2 tension. Simultaneously, coelomic plasma was reduced below control values. The rise in also induced a fall in intra- and extracellular pH, but intracellular pH was rapidly and completely restored. This was achieved during the early period of hypercapnia at the expense of a non-respiratory increase in the extracellular acidosis. The pH of the extracellular space was only partially compensated (by 37%) during long-term hypercapnia. The net release of basic equivalents under control conditions turned to a net release of protons to the ambient water before a net, albeit reduced, rate of base release was re-established after a new steady state had been achieved with respect to acid–base parameters.

Hypercapnia also affected the mode and rate of metabolism. It caused the rate of oxygen consumption to fall, whereas the rate of ammonium excretion remained constant or even increased, reflecting a reduction of the O/N ratio in both cases. The transient intracellular acidosis preceded a depletion of the phosphagen phospho-L-arginine, an accumulation of free ADP and a decrease in the level of Gibbs free energy change of ATP hydrolysis, before replenishment of phosphagen and restoration of pHi and energy status occurred in parallel.

In conclusion, long-term hypercapnia in vivo causes metabolic depression, a parallel shift in acid–base status and increased gas partial pressure gradients, which are related to a reduction in ventilatory activity. The steady-state rise in H+-equivalent ion transfer to the environment reflects an increased rate of production of protons by metabolism. This observation and the reduction of the O/N ratio suggest that a shift to protein/amino acid catabolism has taken place. Metabolic depression prevails, with completely compensated intracellular acidosis during long-term hypercapnia eliminating intracellular pH as a significant factor in the regulation of metabolic rate in vivo. Fluctuating levels of the phosphagen, of free ADP and in the ATP free energy change values independent of pH are interpreted as being correlated with oscillating ATP turnover rates during early hypercapnia and as reflecting a tight coupling of ATP turnover and energy status via the level of free ADP.
Kinematic Models Of The Buccal Mass Of Aplysia Californica
Authors: Drushel Richard F. , Neustadter David M. , Hurwitz Itay , Crago Patrick E. , Chiel Hillel J.
Published: April 2021

The feeding behavior of the marine mollusc Aplysia californica is an intensively studied model system for understanding the neural control of behavior. Feeding movements are generated by contractions of the muscles of the buccal mass. These muscles are internal and cannot be visualized during behavior. In order to infer the movements of the muscles of the buccal mass, two kinematic models were constructed. The first kinematic model assumed that the complex consisting of the pincer-like radula and the underlying odontophore was spherical in shape. In this model, the radula/odontophore was moved anteriorly or posteriorly and the more superficial buccal muscles (11/13 and 12) were fitted around it. Although the overall buccal mass shapes predicted by this model were similar to those observed in vivo during protraction, the shapes predicted during retraction were very different. We therefore constructed a second kinematic model in which the shape of the radula/odontophore was based on the shapes assumed by those structures in vitro when they were passively forced into protraction, rest or retraction positions. As each of these shapes was rotated, the second kinematic model generated overall shapes of the buccal mass that were similar to those observed in vivo during swallowing and tearing, and made predictions about the antero-posterior length of the buccal mass and the relative location of the lateral groove. These predictions were consistent with observations made in vivo and in vitro. The kinematic patterns of intrinsic buccal muscles 11 and 12 in vivo were estimated using the second model. Both models make testable predictions with regard to the functions and neural control of intrinsic buccal muscles 12 and 13.
Cry1Ac, a bacillus thuringiensis toxin, triggers extracellular Ca2+ influx and Ca2+ release from intracellular stores in Cf1 cells (Choristoneura fumiferana, lepidoptera)
Authors: Potvin L. , Laprade R. , Schwartz J. L.
Published: April 2021

Intracellular Ca2+ concentration was measured in single Cf1 cells (Choristoneura fumiferana, spruce budworm) loaded with Fura-2, a Ca2+-sensitive fluorescent probe. Cf1 cells displayed Ca2+ surges in response to Cry1Ac and Cry1C proteins, two Cf1-toxic Bacillus thuringiensis products, but not to Cry1Aa and Cry3A, which are not toxic to Cf1 cells. In the presence of extracellular Ca2+, the toxin-induced Ca2+ response was insensitive to methoxyverapamil, a voltage-dependent Ca2+ channel blocker, but was abolished by lanthanum, a general inhibitor of Ca2+ transport. In the absence of external Ca2+, Cry1Ac induced a small intracellular Ca2+ transient which was inhibited by TMB-8, a blocker of Ca2+ release from inositol-1,4,5-trisphosphate-sensitive pools. Under these conditions, thapsigargin, which inhibits intracellular Ca2+-ATPases, elicited a Ca2+ surge when applied alone. However, subsequent addition of Cry1Ac failed to induce a Ca2+ signal, indicating a depletion of intracellular Ca2+ pools. In Cf1 cells, therefore, bioactive B. thuringiensis toxins triggered intracellular Ca2+ surges which were mainly due to the influx of extracellular Ca2+ through toxin-made pores, as confirmed by planar lipid bilayer experiments. Furthermore, TMB-8- and thapsigargin-sensitive Ca2+ stores contributed to the Cry1Ac-induced Ca2+ signal.
Orientation Of Snow Buntings (Plectrophenax Nivalis) Close To The Magnetic North Pole
Authors: Sandberg Roland , Bäckman Johan , Ottosson Ulf
Published: April 2021

Orientation experiments were performed with first-year snow buntings (Plectrophenax nivalis) during their autumn migration in a natural near-vertical geomagnetic field approximately 400 km away from the magnetic north pole. Migratory orientation of snow buntings was recorded using two different techniques: orientation cage tests and free-flight release experiments. Experiments were performed under clear skies, as well as under natural and simulated complete overcast. Several experimental manipulations were performed including an artificial shift of the E-vector direction of polarized light, depolarization of incoming light and a 4 h slow clock-shift experiment. The amount of stored fat proved to be decisive for the directional selections of the buntings. Fat individuals generally chose southerly mean directions, whereas lean birds selected northerly headings. These directional selections seemed to be independent of experimental manipulations of the buntings’ access to visual cues even in the local near-vertical magnetic field. Under clear skies, the buntings failed to respond to either a deflection of the E-vector direction of polarized light or an experimental depolarization of incoming skylight. When tested under natural as well as simulated overcast, the buntings were still able to select a meaningful mean direction according to their fat status. Similarly, the free-flight release test under complete overcast resulted in a well-defined southsoutheast direction, possibly influenced by the prevailing light northwest wind. Clock-shift experiments did not yield a conclusive result, but the failure of these birds to take off during the subsequent free-flight release test may indicate some unspecified confusion effect of the treatment.
Swimming Kinematics And Respiratory Behaviour Of Xenopus Laevis Larvae Raised In Altered Gravity
Authors: Fejtek Monika , Souza Kenneth , Neff Anton , Wassersug Richard
Published: April 2021

We examined the respiratory behaviours and swimming kinematics of Xenopus laevis tadpoles hatched in microgravity (Space Shuttle), simulated microgravity (clinostat) and hypergravity (3 g centrifuge). All observations were made in the normal 1 g environment. Previous research has shown that X. laevis raised in microgravity exhibit abnormalities in their lungs and vestibular system upon return to 1 g.

The tadpoles raised in true microgravity exhibited a significantly lower tailbeat frequency than onboard 1 g centrifuge controls on the day of landing (day0), but this behaviour normalized within 9 days. The two groups did not differ significantly in buccal pumping rates. Altered buoyancy in the space-flight microgravity tadpoles was indicated by an increased swimming angle on the day after landing (day1). Tadpoles raised in simulated microgravity differed to a greater extent in swimming behaviours from their 1 g controls. The tadpoles raised in hypergravity showed no substantive effects on the development of swimming or respiratory behaviours, except swimming angle. Together, these results show that microgravity has a transient effect on the development of locomotion in X. laevis tadpoles, most notably on swimming angle, indicative of stunted lung development. On the basis of the behaviours we studied, there is no indication of neuromuscular retardation in amphibians associated with embryogenesis in microgravity.
Hypertrehalosaemic Neuropeptides Decrease Levels Of The Glycolytic Signal Fructose 2,6-Bisphosphate In Cockroach Fat Body
Authors: Becker Andreas , Wegener Gerhard
Published: April 2021

In cockroach fat body, trehalogenesis and glycolysis compete for glucose phosphates as common substrates. During trehalogenesis, glycolysis is inhibited, although the mechanism responsible for this is not known. Incubation of the isolated fat body from the Argentine cockroach Blaptica dubia with an extract of the corpora cardiaca containing as little as 0.005 gland equivalents ml−1 of incubation medium increased the release of trehalose (anthrone-positive material) from the tissue by more than 100 %. The content of the glycolytic activator fructose 2,6-bisphosphate was decreased by up to 50 %. A decapeptide was isolated from the corpora cardiaca of B. dubia and shown to be identical to the naturally occurring Blaberus discoidalis hypertrehalosaemic peptide (Bld HrTH), which was also found in the corpora cardiaca. Synthetic Bld HrTH at 2 nmol l−1 and above increased trehalose production and decreased the content of fructose 2,6-bisphosphate to the same extent as did corpus cardiacum extract. The octapeptides Periplaneta americana cardioacceleratory hormones I and II (Pea CAH-I and Pea CAH-II) also had a significant effect on both parameters. Fructose 2,6-bisphosphate is a potent activator of phosphofructokinase from cockroach fat body if the enzyme is assayed at near-physiological concentrations of substrates and effectors. It is suggested that, because of the decrease in fructose 2,6-bisphosphate levels in the fat body, the activity of the key glycolytic enzyme phosphofructokinase is diminished. This can explain the inhibition of glycolytic flux by hypertrehalosaemic peptides which alters the balance of glucose metabolism in favour of trehalose formation.
The Effects of Increased Protein Intake on Kidney Size and Function
Authors: Hammond Kimberly A. , Janes Donald N.
Published: April 2021

In endothermic vertebrates, long-term increases in metabolic energy demand are often associated with increases in food intake and accompanied by increases in organ mass. Wide-scale increases in organ mass have often been attributed to a metabolic response to increased energy intake and utilization. On a constant diet, however, increased food intake is also associated with increased protein intake. We hypothesized that, while increased food intake itself may be responsible for increases in digestive tract mass, the consequent increased protein intake would be the factor responsible for increased kidney mass and function. Thus, we exposed male and female mice to diets differing in protein level (7 %, 15 % or 46 % casein by mass) at different acclimation temperatures (5 °C or 23 °C). Within an acclimation temperature, food intake rate remained constant over the entire range of dietary protein level, and protein intake rate increased as dietary content increased. The mice in the cold-acclimation group increased food intake rate by 48–120 % over those in the warm-acclimation group. Liver, kidney and stomach mass increased with protein intake rate, while digestive tract and other vital organ masses increased only in response to increased energy intake rate. Blood urea nitrogen levels increased with protein intake rate. Glomerular filtration rates increased with increases in dietary protein level in male mice but not female mice. Finally nitrogen filtration rate increased with protein intake rate for mice on the high-protein diet. We suggest that it is primarily the increased protein intake rate rather than the increased food intake rate that results in the changes in kidney and liver mass and kidney function observed to occur in situations of high energy demand.
Augmented Respiration in a Flying Insect
Authors: Komai Yutaka
Published: April 2021

The properties of the gas transport system in a tethered flying insect were investigated by directly measuring the oxygen partial pressure in a wing muscle of the sweet potato hawkmoth Agrius convolvuli using a needle electrode.

At rest, a distribution of corresponding to levels in the muscle and tracheal structures was observed. At the onset of tethered flight, in the muscle decreased. However, during a long stable flight, increased and reached a plateau approximately 2 min after the onset of flight. During stable tethered flight, in the centre of the second layer of the dorsal longitudinal muscle was locally higher than that during rest. As wing amplitude increased, increased in spite of the concurrent increase in metabolic rate. During tethered flight at a constant wing amplitude, was proportional to the mean wing positional angle.

The results suggest that this insect effectively uses muscle movement, which increases the frequency and stroke volume of ventilation, to augment gas exchange during flight.
Variation in Kinematics and Dynamics of the Landing Flights of Pigeons on a Novel Perch
Authors: Green Patrick R. , Cheng Peter
Published: April 2021

Pigeons made 10 flights to a novel perch. Kinematic measurements of these flights were obtained from video recordings, and the forces exerted on the perch on each landing were measured. There was wide variation (20-fold range) in the kinetic energy of the pigeons just before landing, arising almost entirely from variation in horizontal velocity. The maximum force exerted on the perch varied in magnitude from approximately twice to eight times the pigeons’ body weight, and in direction from 40 to 90 ° below the horizontal. In landings with high final kinetic energy, the maximum force exerted on the perch was larger and was applied at a shallower angle than in those with low final kinetic energy. Landing flights with high final kinetic energy showed straighter trajectories and a larger peak deceleration during the last 300 ms of approach flight than those with low final kinetic energy, which had downward-curving trajectories and a more prolonged and steady pattern of deceleration. Mean final kinetic energy was lower in the first two landings made on the perch than in subsequent landings, indicating that pigeons are more likely to adopt a slow, downward-curving approach to a novel perch and a fast, straight approach to a familiar one.
Interactive Effects of Salinity On Metabolic Rate, Activity, Growth and Osmoregulation in the Euryhaline Milkfish (Chanos Chanos)
Authors: Swanson Christina
Published: April 2021

The euryhaline milkfish (Chanos chanos) is an excellent subject for studies of the physiological and behavioral processes involved in salinity adaptation. In this study, energy partitioning for metabolism, activity and growth, maximal activity performance and blood osmotic concentrations were assessed at two activity levels in juvenile milkfish fed equal rations and maintained at a relatively constant temperature (26±2 °C) and at salinities (15, 35 and 55 ‰) that represented a wide range of osmoregulatory challenges. Changes in the measured parameters were not consistently related to the magnitude of the trans-integumentary osmotic gradients. Routine oxygen consumption rates were high in 35 ‰ salinity (mean ±1 S.E.M. 167±8 mg O2 kg−1 h−1) and comparably low in 15 and 55 ‰ salinity (133±6 and 127±3 mg O2 kg−1 h−1, respectively). Routine activity levels (relative swimming velocity) were highest in 35 ‰ salinity (0.96±0.04 L s−1), where L is standard length, intermediate in 15 ‰ salinity (0.77±0.03 L s−1) and lowest in 55 ‰ salinity (0.67±0.03 L s−1). Growth was significantly higher in 55 ‰ salinity (3.4±0.2 % increase in wet body mass per day) than in 35 ‰ salinity (2.4±0.2 % increase per day) and intermediate in 15 ‰ salinity (2.9±0.5 % increase per day). Maximum swimming velocities decreased with increases in salinity, from 9.9±0.7 L s−1 in 15 ‰ salinity to 6.6±0.5 L s−1 in 55 ‰ salinity. Sustained swimming activity above routine levels for 2 h resulted in an increase in blood osmotic concentrations in milkfish in 55 ‰ salinity, but osmoregulation was re-established during the second 2 h of activity. Thus, patterns of variation in metabolic rate and growth were largely parallel to variations in routine activity although, comparing 15 and 55 ‰ salinity, elevated maintenance costs for osmoregulation at the high salinity were detectable. Reduced osmoregulatory abilities and reductions in maximal swimming performance suggest that high salinity may constrain activity. The results demonstrate that investigations of salinity adaptation in euryhaline fishes should take into account the interactive effects of salinity on physiology and behavior.
Inter-Tissue Differences In Mitochondrial Enzyme Activity, Rna And Dna In Rainbow Trout (Oncorhynchus Mykiss)
Authors: Leary S. C. , Battersby B. J. , Moyes C. D.
Published: April 2021

We examined whether the relationships between mitochondrial enzyme activity, mitochondrial DNA (mtDNA) and mitochondrial RNA (mtRNA) were conserved in rainbow trout (Oncorhynchus mykiss) tissues that differ widely in their metabolic and molecular organization. The activity of citrate synthase (CS), expressed either per gram of tissue or per milligram of total DNA, indicated that these tissues (blood, brain, kidney, liver, cardiac, red and white muscles) varied more than 100-fold in mitochondrial content. Several-fold differences in the levels of CS mRNA per milligram of DNA and CS activity per CS mRNA were also observed, suggesting that fundamental differences exist in the regulation of CS levels across tissues. Although tissues varied 14-fold in RNA g−1, poly(A+) RNA (mRNA) was approximately 2 % of total RNA in all tissues. DNA g−1 also varied 14-fold across tissues, but RNA:DNA ratios varied only 2.5-fold. The relationship between two mitochondrial mRNA species (COX I, ATPase VI) and one mitochondrial rRNA (16S) species was constant across tissues. The ratio of mtRNA to mtDNA was also preserved across most tissues; red and white muscle had 10-to 20-fold lower levels of mtDNA g−1 but 7-to 10-fold higher mtRNA:mtDNA ratios, respectively. Collectively, these data suggest that the relationship between mitochondrial parameters is highly conserved across most tissues, but that skeletal muscles differ in a number of important aspects of respiratory gene expression (‘respiratory genes’ include genes located on mtDNA and genes located in the nucleus that encode mitochondrial protein) and mtDNA transcriptional regulation.
Stimulation Of Fluid Secretion Of Malpighian Tubules Of Drosophila Melanogaster Meig. By Cyclic Nucleotides Of Inosine, Cytidine, Thymidine And Uridine
Authors: Riegel J. A. , Maddrell S. H. P. , Farndale R. W. , Caldwell F. M.
Published: April 2021

External application of the 3′,5′-cyclic monophosphates of inosine, cytidine, uridine and thymidine stimulated the fluid secretion rate (FSR) of Malpighian tubules isolated from Drosophila melanogaster. The evidence suggested that the cyclic nucleotides acted intracellularly in some capacity. Receptors of the ‘purinergic’ type appeared not to be major contributors to fluid secretion; of three purinergic agonists tried, adenosine, adenosine 5′-monophosphate (AMP) and adenosine 5′-triphosphate (ATP), only adenosine had an effect, but this was not observed consistently. None of the purinergic agonists interfered with the stimulation of the FSR by adenosine 3′,5′-cyclic monophosphate (cAMP). The maximum stimulation of the fluid-secretion rate by any cyclic nucleotide was approximately double the unstimulated (control) rate. Tubules stimulated to less than maximal FSR by one cyclic nucleotide could be stimulated maximally by an appropriate concentration of another cyclic nucleotide. Malpighian tubules bathed in solutions that contained either [3H]cAMP or [3H]cGMP accumulated radioactivity to a level many times that in the medium. Accumulation of radioactivity by tubules bathed in 430 nmol l−1 [3H]cAMP was suppressed by 1 mmol l−1 non-radioactive cyclic nucleotides in the order cAMP⪢cGMP>cIMP>cCMP; neither cTMP nor cUMP suppressed the accumulation of [3H]cAMP. Approximately 35 % of the [3H]cAMP and 80 % of the [3H]cGMP that entered the Malpighian tubule cells was metabolised to compounds that were not identified. It was concluded that cyclic nucleotides enter the Malpighian tubule cells by at least one transport mechanism which is particularly sensitive to purine-based nucleotides.
Sarcomere Number Adaptation After Retinaculum Transection In Adult Mice
Authors: Burkholder Thomas J. , Lieber Richard L.
Published: April 2021

Skeletal muscle has been shown to adjust serial sarcomere number in response to chronic static length changes. However, the adaptive responses to alterations in the dynamic environment are less well defined. The adaptations of the adult mouse tibialis anterior (TA) muscle to altered length and excursion were investigated by surgical transection of the flexor retinaculum. TA moment arm and muscle excursion increased by 38±7 % (mean ± S.E.M.) and fully extended (plantarflexed) muscle length was decreased by 8 % after flexor retinaculum transection. In spite of the significant shortening of the muscle in full plantar- and dorsiflexion, serial sarcomere number decreased by 10±1 % after 2 weeks of recovery. Gait analysis of these transected animals revealed a 14±3 % decrease in dorsiflexion angular velocity after transection. The decrease in angular velocity was less than the increase in moment arm and, as a result, muscle velocity was calculated to increase by 20±4 %. These data suggested that the muscle adapted in response to the underlying change in length, irrespective of the altered excursion or velocity.
Testing Hypotheses Concerning The Phenotypic Plasticity Of Escape Performance In Fish Of The Family Cottidae
Authors: Temple Genevieve K. , Johnston Ian A.
Published: April 2021

A knowledge of the natural history of two species of marine Cottidae was used to construct a set of complex a priori hypotheses to test the idea that seasonal temperature acclimation conferred a fitness advantage and to examine whether acclimation responses were constant through development. The species studied were the short-horn sculpin (Myoxocephalus scorpius L.) and the long-spined sea scorpion (Taurulus bubalis Euphr.). Fast-start escape performance was measured as a proxy of fitness, and maximum body-length-specific speed (Ûmax) and acceleration (Âmax), and angular velocity (ωmax) and cumulative turning angle (CTA) were quantified. Fish were acclimated to 5, 15 and 20 °C and filmed using high-speed cinematography at 0.8, 5.0, 15.0 and 20.0 °C. The following hypotheses were tested: (1) improvements in escape performance following acclimation to high temperature in adult short-horn sculpin that live offshore would involve a trade-off in performance at low temperature, (2) the escape response of the sea scorpion, which experiences large daily temperature variation, would exhibit low thermal sensitivity and be unchanged by acclimation between 5 and 15 °C, and (3) in short-horn sculpin, the ability to acclimate maximum speed thermally is acquired during ontogeny in parallel with the offshore migration of the late juvenile stage. At 20.0 °C, in adult short-horn sculpin, Ûmax and Âmax were 110 % and 55 % higher, respectively, in 15 °C-than in 5 °C-acclimated fish. No evidence was obtained for improved fast-start performance at 0.8 °C or 5.0 °C following cold acclimation. In the long-spined sea scorpion, acclimation to 5 and 15 °C did not improve Ûmax or Âmax compared with fish acutely exposed to these temperatures, although acclimation to 5 °C increased ωmax (P=0.005).

When tested over the most extreme thermal range found in the field, all variables were improved at a test temperature of 0.8 °C in 5 °C-compared with 15 °C-acclimated sea scorpion. Acclimation therefore appeared to be beneficial in some instances in both species. How this affects relative fitness is uncertain. The scaling of Ûmax with acclimation to 5 and 15 °C was examined in both species over the test range 5.0–15.0 °C. Temperature acclimation did not affect scaling relationships of Ûmax in long-spined sea scorpion ranging in total body length (L) from 45 to 160 mm. At a test temperature of 15.0 °C, the scaling of Ûmax for short-horn sculpin ranging in total body length from 43 to 270 mm changed from aL−0.98 in 5 °C-acclimated fish to aL−0.50 (where a is the proportionality coefficient in the regression equation) in 15 °C-acclimated fish (P<0.01). In short-horn sculpin, therefore, the ability to modify escape performance with temperature acclimation was found to vary during ontogeny, potentially paralleling a migration from a more variable to a more stable thermal environment.
Rattlesnake Strike Behavior: Kinematics
Authors: Kardong Kenneth V. , Bels Vincent L.
Published: April 2021

The predatory behavior of rattlesnakes includes many distinctive preparatory phases leading to an extremely rapid strike, during which venom is injected. The rodent prey is then rapidly released, removing the snake’s head from retaliation by the prey. The quick action of the venom makes possible the recovery of the dispatched prey during the ensuing poststrike period. The strike is usually completed in less than 0.5 s, placing a premium on an accurate strike that produces no significant errors in fang placement that could result in poor envenomation and subsequent loss of the prey. To clarify the basis for effective strike performance, we examined the basic kinematics of the rapid strike using high-speed film analysis. We scored numerous strike variables. Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures. (3) Forces generated during acceleration of the head are transferred to posterior body sections to decelerate the head before contact with the prey, thereby reducing impact forces upon the snake’s jaws. (4) Body acceleration is based on two patterns of body displacement, one in which acute sections of the body open like a gate, the other in which body segments flow around postural curves similar to movements seen during locomotion. There is one major implication of these results: recruitment of body segments, launch postures and kinematic features of the strike may be quite varied from strike to strike, but the overall predatory success of each strike by a rattlesnake is very consistent.
Homing Pigeons Use Olfactory Cues for Navigation In England
Authors: Guilford Tim , Gagliardo Anna , Chappell Jackie , Bonadonna Francesco , Perera Theresa Burt De , Holland Richard
Published: April 2021

Although the use of olfactory cues in pigeon navigation is well established, the generality of olfactory navigation remains uncertain because of apparent variability in results gained by different researchers in different regions. We report the results of the first experiments investigating the effect of anosmia on homing pigeons reared in a previously uninvestigated region, southern England. In series 1, experienced birds showed little effect of anosmia induced with zinc sulphate at unfamiliar sites 30 km and 39 km from the loft, but treated birds were significantly poorer than controls at homing from an unfamiliar site 66 km distant (and in pooled results). In series 2, naïve (untrained) birds, both control and zinc-sulphate-treated, showed poor homing abilities and initial orientation from sites 25 km, 36 km and 39 km from the loft. Nevertheless, in pooled results, controls showed significantly better homeward orientation than anosmic birds and were significantly more likely to home on the day of release. The most likely explanation for our results is that pigeons are able to use olfactory navigation in southern England, but that for some reason the olfactory map is relatively weak.
Scaling of Muscle Performance During Escape Responses in the Fish Myoxocephalus Scorpius L
Authors: James Rob S. , Johnston Ian A.
Published: April 2021

Fast-starts associated with escape responses were studied in short-horn sculpin (Myoxocephalus scorpius L.), ranging from 5.5 to 32 cm in total length (L). Electromyography and sonomicrometry were used simultaneously to measure muscle activation and length changes, respectively, in the superficial layers of fast muscle in rostral myotomes. Escape responses consisted of a half tailbeat to bend the body into a C-shape (C-bend), another half tailbeat (contralateral contraction), followed by one or two more tailbeats and/or a gliding phase. The scaling relationships for both muscle strain and shortening duration differed between the C-bend and the contralateral contraction. As a result, relative muscle shortening velocity (V/V0) scaled as −1.18L1.06 for the C-bend and as 1.23L−0.66 for the contralateral contraction. Therefore, the scaling relationships for muscle shortening velocity varied throughout the time course of the escape response. Muscle power output was determined by using the work-loop technique to subject isolated muscle fibres to in vivo strain and stimulation patterns. Plots of the instantaneous muscle forces and velocities achieved during the contralateral contraction were found to deviate from the steady-state force–velocity relationship. Maximum instantaneous muscle power output was independent of body size, with mean maximum values of 307 and 222W kg−1 wet muscle mass for the C-bend and the contralateral contraction, respectively.
Finding Food: Senses Involved in Foraging for Insect Larvae in the Electric Fish Gnathonemus Petersii
Authors: Emde Gerhard Von Der , Bleckmann Horst
Published: April 2021

The weakly electric fish Gnathonemus petersii searches at night for insect larvae in tropical African streams. The aim of this study was to determine the contributions of different sensory modalities to foraging. The time that fish needed to find two randomly placed chironomid larvae was measured. The influence of various senses on search time was investigated by blocking the use of one or more senses. Active electrolocation was used by most fish for prey detection in the dark. In addition, passive electrolocation played a role in some individuals. If light was available, vision could become the dominant sense in some individuals, replacing active electrolocation. The presence of chemical cues decreased prey detection time in most fish. Prey movements also shortened search times when active electrolocation and vision were not possible, indicating that the mechanosensory lateral line also plays a role in the detection of moving prey. The results show that G. petersii uses several senses simultaneously during foraging. Each individual favours a specific combination of the available sensory inputs. If one sensory modality is eliminated, fish can switch to other modalities, indicating that the food detection system is flexible and plastic.
Oxygen and the Upper Limits to Animal Design and Performance
Authors: Suarez Raul K.
Published: April 2021

Mass-specific rates of aerobic metabolism (/Mb) scale in inverse proportion to body mass (Mb). Thus, small hummingbirds display the highest / Mb known among vertebrates. Among all animals, higher /Mb values are known only in flying insects. The high body-mass-specific rates of metabolism seen in hummingbirds are made possible by high lung O2 diffusing capacities, cardiac outputs, ratios of capillary surface area to muscle fiber surface area, mitochondrial volume densities, cristae surface densities and concentrations of enzymes involved in energy metabolism. Current evidence from control analyses of O2 transport through the respiratory and cardiovascular systems and of metabolic fluxes through pathways of energy metabolism indicates shared control of maximum flux rates among multiple steps (i.e. the absence of single rate-limiting steps). This supports the suggestion that functional capacities at each step in linear pathways or processes are matched to each other, and provides an explanation for why the up-regulation of functional capacities has occurred at virtually all steps in the evolution of the smallest vertebrate homeotherms. Flying insects make use of a tracheal system for O2 transport and, like hummingbirds, possess a highly up-regulated biochemical machinery for substrate oxidation. Studies of hummingbirds and honeybees reveal closer matches between biochemical flux capacities and maximum physiological flux rates than in animals capable of lower maximum /Mb. It is proposed that the upper limits to functional capacities set the upper limit to /Mb. This upper limit to aerobic metabolic rate may contribute, along with other factors, towards establishing the lower limit to vertebrate homeotherm size.
Self-Association, Cooperativity and Supercooperativity of Oxygen Binding by Hemoglobins
Authors: Riggs Austen F.
Published: April 2021

Cooperative ligand binding by tetrameric vertebrate hemoglobins (Hbs) makes possible the delivery of oxygen at higher pressures than would otherwise occur. This cooperativity depends on changes in dimer–dimer interactions within the tetramer and is reflected in a 50 000-fold increase in the tetramer–dimer dissociation constant in human Hb upon oxygenation at pH 7.4, from approximately 2×10−11 mol l–1 to approximately 10−6 mol l−1. Hbs that undergo such ligand-dependent changes in association are widespread in non-vertebrates, where the mechanisms are very different from those in vertebrates. Oligomeric Hbs have been identified in organisms in five phyla (molluscs, echinoderms, annelids, phoronids and chordates) that dissociate to subunits upon oxidation of the heme iron and reassociate with the binding of ferric iron ligands such as CN−, N3− or NO2−. Thus, the valence and ligand state of the heme iron control the stability of a critical subunit interface. The broad distribution of this phenomenon suggests a common mechanism of communication between heme and interface that may be almost universal among non-vertebrate Hbs. This interaction may be similar to that known for the homodimeric Hb of the mollusc Scapharca inaequivalvis.

Although muscle tissue Hbs or myoglobins (Mbs) are usually monomeric, with non-cooperative O2 binding, the radular muscles of gastropod molluscs and chitons have homodimeric Mbs that bind O2 cooperatively. Cooperative non-muscle tissue Hbs have also been identified. These include the neural Hb of the nemertean worm Cerebratulus lacteus and the Hb of the diving beetle Anisops assimilis, which exhibit deoxygenation-dependent self-association of monomers that is associated with high Hill coefficients. Calculations suggest that the 2–3 mmol l−1 concentration of Hb on a heme basis in the brain of Cerebratulus should substantially extend the time as an active predator in an anaerobic or hypoxic environment. Oxygen from the Hb of Anisops is delivered to a gas bubble and thereby controls the buoyant density.

Many Hbs of amphibians, reptiles, birds and some embryonic mammals exhibit a further ‘supercooperativity’ of O2 binding which depends on reversible deoxygenation-dependent tetramer–tetramer association to form an assemblage with a very low affinity for O2. This phenomenon results in steeper O2-binding curves than exhibited by tetramers alone. The increased cooperativity should result in an increase in the amount of O2 delivered to the tissues and should be especially valuable for avian flight muscles.