bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of Thermal Balance in Flying Centris Pallida (Hymenoptera: Anthophoridae)
Authors: Roberts Stephen P. , Harrison Jon F. , Hadley Neil F. 
Published: April 2021

ABSTRACT
Thermoregulation of the thorax is critical for bees and other endothermic insects to achieve high rates of flight muscle power production. However, the mechanisms allowing insects to regulate thorax temperatures during flight are not well understood. To test whether variations in metabolic heat production, evaporation or heat transfer from the thorax to the abdomen contribute to the maintenance of stable body temperatures during flight in the bee Centris pallida, we measured CO2 production, water vapor loss, wingbeat frequency and body segment temperatures during flight at varying air temperatures (Ta). While hovering in the field and while flying in the respirometer, C. pallida males maintain extremely stable, elevated thorax temperatures (45±2 °C; mean ± S.E.M.). Measurements of head, thorax and abdomen temperatures as a function of Ta during hovering flight in the field indicated that C. pallida males were not actively increasing heat transfer from the thorax to the head or abdomen at high Ta values. As Ta increased from 26 to 35 °C, increases in evaporative water loss were relatively small compared with the decrease in carbon dioxide emission. As Ta values increased from 26 to 35 °C, the factorial decreases in metabolic heat production and the elevation of thorax temperature above Ta were closely matched (35 %), suggesting that variation in metabolic heat production is the major mechanism of thermoregulation in flying C. pallida. The thermal effects on rates of water loss and metabolic water production resulted in a strong positive water balance at cooler Ta values, but a strong negative water balance at Ta values above 31 °C. During the first minute of flight in the respirometry chamber, wingbeat frequency was independent of Ta. However, by the fourth minute, there was a significant negative relationship between Ta and wingbeat frequency, which was similar to the thermal relationship observed for wingbeat frequency in the field. These data suggest that, either through homeostatic regulation or resulting secondarily from thermal effects on flight motor properties, variation in metabolic heat production may occur via altered wingbeat kinematics.
Activation Patterns and Length Changes in Hindlimb Muscles of the Bullfrog Rana Catesbeiana During Jumping
Authors: Olson John M. , Marsh Richard L. 
Published: April 2021

ABSTRACT
We measured the electromyographic (EMG) activity of seven hindlimb muscles during jumping in the bullfrog Rana catesbeiana. The semimembranosus, gracilis major, gluteus magnus, adductor magnus, cruralis and plantaris longus were consistently active approximately 20–40 ms before any perceptible movement, as indicated by simultaneous video recordings. Activity ended before full extension of the hindlimb and take-off. Activity in the semitendinosus was variable among the jumps recorded. Simultaneous measurements of EMG activity and length changes (via sonomicrometry) in the semimembranosus (SM) and gluteus magnus (GM) muscles indicated that the performance characteristics of these two muscles differed. The SM muscle (a hip extensor) shortens and is activated in a manner consistent with its producing power during a significant fraction of the take-off phase. It shortened by a mean of 26.2 % of the resting length during the propulsive phase of the two longest jumps for each frog. The delay between the onset of EMG activity and the beginning of shortening averaged 24 ms, which was brief compared with that found for the GM. The total strain and mean shortening velocity of the SM increased with jumping distance. Contrary to our initial expectations, the GM muscle does not shorten as one would expect of a muscle involved in powering the jump throughout take-off. This muscle has an extensor action at the knee, but also has a flexor action at the hip. A long delay existed between the onset of EMG activity and the beginning of shortening (46–116 ms among the individuals tested). Shortening during take-off by the GM (a mean of 16.7 % for all jumps) was much less than by the SM, and in many jumps most of this shortening occurred late in the take-off period. Although the GM cannot contribute directly to power output early in take-off, it may contribute to powering the jump indirectly by transferring energy from the hip extensors to the knee joint. We conclude that muscles previously assumed (on the basis of anatomical criteria) by ourselves and others to be powering the jump may show considerable diversity of function. We hypothesize that elastic energy storage is used to help power jumping, and therefore suggest that muscles in series with major tendinous elements should be targeted for further study.
Functional Partitioning of Energy Reserves by Larvae of the Marine Bryozoan Bugula NeritinA (L.)
Authors: Hunter E. , Okano Keiju , Tomono Y. , Fusetani N. 
Published: April 2021

ABSTRACT
The effects of extended swimming on short-lived lecithotrophic larvae of the marine bryozoan Bugula neritina (L.) were examined. Larvae were forced to swim for 2 or 24 h by bath application of serotonin. Settlement and metamorphosis success were significantly reduced, larval dimensions were unaffected and ancestrulae were smaller after 24 h of swimming. Larvae settled predominantly on seawater-conditioned glass after 2 h, but became less discriminative after 24 h.
Lipid content in intact larvae and dissociated surface ciliated and interior cell fractions was analysed by thin-layer chromatography. Hydrophilic lipids were unaffected by swimming regime. The hydrophobic fraction contained triglyceride, confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR) analysis and correlation spectroscopy (1H-1H COSY) patterns, which was significantly depleted after 24 h, and diacylglycerol, which was not. NMR spectra suggested no differences in fatty acid chain compositions between larvae swimming for 2 and 24 h. Triglyceride depletion was limited to the ciliated cell fraction.
We propose that the functional partitioning of lipid reserves has evolved in association with the costs and benefits linked with larval dispersal.
Diet Quality Influences the δ13C and δ15N of Locusts and Their Biochemical Components
Authors: Webb Sarah C. , Hedges Robert E. M. , Simpson Stephen J. 
Published: April 2021

ABSTRACT
To determine whether relative enrichments of 15N and 13C in locusts are influenced by diet, locust nymphs were raised from hatchlings to adults on either seedling wheat or maize. Maize provided less hexose sugars and protein per gram than did wheat. Maize also depends on the C4 form of photosynthesis, while wheat uses the C3 form; this difference in photosynthetic pathways produces two distinguishable ranges of δ13C values.
The lower-quality maize diet corresponded to a 5.1 ‰ increase in animal δ15N, relative to diet, whereas the wheat diet corresponded to an increase of only 2.3 ‰. The maize-fed animals were more δ13C-depleted in lipid, trehalose and chitin than those fed wheat. The results for δ15N and δ13C suggest that substrate recycling occurred on the low-quality maize diet. Consequently, we examined the variations in the isotopic differences between locusts and their diet at the biochemical level.
Using laboratory selection for desiccation resistance to examine the relationship between respiratory pattern and water loss in insects
Authors: Williams Adrienne E. , Rose Michael R. , Bradley Timothy J. 
Published: April 2021

ABSTRACT
We conducted concurrent measurements of rates of CO2 and H2O release from individual fruit flies Drosophila melanogaster taken from populations subjected to three different selective regimes: (1) populations selected for resistance to desiccation (D flies); (2) populations maintained as their controls (C flies); and (3) the ancestral populations of the D and C populations (O flies). In the D flies, water loss rates were significantly reduced, the standard error of the regression (SER) of the CO2 release pattern measured over the survival period of th.e flies. was increased, and the ratio of CO2 loss to H2O loss was increased. Correlations across all 15 populations from the three selection treatments indicate that survival time was negatively correlated with water loss rate, positively correlated with the SER of CO2 release and positively correlated with the ratio. We did not, however, find a significant correlation between the SER of CO2 release and rates of water loss or the ratio.
Novel non-cellular adhesion and tissue grafting in the mutable collagenous tissue of the sea cucumber Parastichopus parvimensis
Authors: Szulgit Greg K. , Shadwick Robert E. 
Published: April 2021

ABSTRACT
Previous work on wound healing in holothurians (sea cucumbers) has been concerned with the relatively long-term cellular processes of wound closure and regeneration of new tissue. In this report, we characterize a short-term adhesion that is a very early step in holothurian wound healing. Dissected pieces of dermis from the sea cucumber Parastichopus parvimensis adhered to each other after only 2 h of contact, whether the cells in the tissues were intact or had been lysed. Lapshear tests showed that the breaking stresses of adhered tissues reached approximately 0.5 kPa after 24 h of contact. Furthermore, dermal allografts were incorporated into the live recipient individuals without any external pressures, sutures or artificial gels to keep them in place. Dislodging the grafts after 24 h of contact required shear stresses of approximately 14 kPa. It appears that the adhesive property of the dermis plays a key role in the initiation of this grafting.
Mechanics of the Fast-Start: Muscle Function and the Role of Intramuscular Pressure in the Escape Behavior of Amia Calva and Polypterus Palmas
Authors: Westneat Mark W. , Hale Melina E. , Mchenry Matthew J. , Long John H. 
Published: April 2021

ABSTRACT
The fast-start escape response is a rapid, powerful body motion used to generate high accelerations of the body in virtually all fishes. Although the neurobiology and behavior of the fast-start are often studied, the patterns of muscle activity and muscle force production during escape are less well understood. We studied the fast-starts of two basal actinopterygian fishes (Amia calva and Polypterus palmas) to investigate the functional morphology of the fast-start and the role of intramuscular pressure (IMP) in escape behavior. Our goals were to determine whether IMP increases during fast starts, to look for associations between muscle activity and elevated IMP, and to determine the functional role of IMP in the mechanics of the escape response. We simultaneously recorded the kinematics, muscle activity patterns and IMP of four A. calva and three P. palmas during the escape response. Both species generated high IMPs of up to 90 kPa (nearly 1 atmosphere) above ambient during the fast-start. The two species showed similar pressure magnitudes but had significantly different motor patterns and escape performance. Stage 1 of the fast-start was generated by simultaneous contraction of locomotor muscle on both sides of the body, although electromyogram amplitudes on the contralateral (convex) side of the fish were significantly lower than on the ipsilateral (concave) side. Simultaneous recordings of IMP, escape motion and muscle activity suggest that pressure change is caused by the contraction and radial swelling of cone-shaped myomeres. We develop a model of IMP production that incorporates myomere geometry, the concept of constant-volume muscular hydrostats, the relationship between fiber angle and muscle force, and the forces that muscle fibers produce. The timing profile of pressure change, behavior and muscle action indicates that elevated muscle pressure is a mechanism of stiffening the body and functions in force transmission during the escape response.
Soil Hydric Characteristics and Environmental Ice Nuclei Influence Supercooling Capacity of Hatchling Painted Turtles Chrysemys Picta
Authors: Costanzo Jon P. , Litzgus Jacqueline D. , Iverson John B. , Lee Richard E. 
Published: April 2021

ABSTRACT
Hatchling painted turtles (Chrysemys picta) hibernate in their shallow natal nests where temperatures occasionally fall below −10 °C during cold winters. Because the thermal limit of freeze tolerance in this species is approximately −4 °C, hatchlings rely on supercooling to survive exposure to extreme cold. We investigated the influence of environmental ice nuclei on susceptibility to inoculative freezing in hatchling C. picta indigenous to the Sandhills of west-central Nebraska. In the absence of external ice nuclei, hatchlings cooled to −14.6±1.9 °C (mean ± S.E.M.; N=5) before spontaneously freezing. Supercooling capacity varied markedly among turtles cooled in physical contact with sandy soil collected from nesting locales or samples of the native soil to which water-binding agents (clay or peat) had been added, despite the fact that all substrata contained the same amount of moisture (7.5 % moisture, w/w). The temperature of crystallization (Tc) of turtles exposed to frozen native soil was −1.6±0.4 °C (N=5), whereas turtles exposed to frozen soil/clay and soil/peat mixtures supercooled extensively (mean Tc values approximately −13 °C). Hatchlings cooled in contact with drier (⩽4 % moisture) native soil also supercooled extensively. Thus, inoculative freezing is promoted by exposure to sandy soils containing abundant moisture and little clay or organic matter. Soil collected at turtle nesting locales in mid and late winter contained variable amounts of moisture (4–15 % w/w) and organic matter (1–3 % w/w). In addition to ice, the soil at turtle nesting locales may harbor inorganic and organic ice nuclei that may also seed the freezing of hatchlings. Bulk samples of native soil, which were autoclaved to destroy any organic nuclei, nucleated aqueous solutions at approximately −7 °C (Tc range −6.1 to −8.2 °C). Non-autoclaved samples contained water-extractable, presumably organic, ice nuclei (Tc range −4.4 to −5.3 °C). Ice nuclei of both classes varied in potency among turtle nesting locales. Interaction with ice nuclei in the winter microenvironment determines whether hatchling C. picta remain supercooled or freeze and may ultimately account for differential mortality in nests at a given locale and for variation in winter survival rates among populations.
External work and potential for elastic storage at the limb joints of running dogs
Authors: Gregersen Colin S. , Silverton Natalie A. , Carrier David R. 
Published: April 2021

ABSTRACT
The storage and recovery of elastic strain energy in muscles and tendons increases the economy of locomotion in running vertebrates. In this investigation, we compared the negative and positive external work produced at individual limb joints of running dogs to evaluate which muscle–tendon systems contribute to elastic storage and to determine the extent to which the external work of locomotion is produced by muscles that shorten actively rather than by muscles that function as springs. We found that the negative and positive external work of the extensor muscles is not allocated equally among the different joints and limbs. During both trotting and galloping, the vast majority of the negative work was produced by the two distal joints, the wrist and ankle. The forelimb produced most of the negative work in both the trot and the gallop. The hindlimb produced most of the positive work during galloping, but not during trotting. With regards to elastic storage, our results indicate that the forelimb of dogs displays a greater potential for storage and recovery of elastic energy than does the hindlimb. Elastic storage appears to be more important during trotting than during galloping, and elastic storage appears to be more pronounced in the extensor muscles of the distal joints than in the extensor muscles of the proximal joints. Furthermore, our analysis indicates that a significant portion of the external work of locomotion, 26 % during trotting and 56 % during galloping, is produced by actively shortening muscles. We conclude that, although elastic storage of energy is extremely important to the economy of running gaits, actively shortening muscles do make an important contribution to the work of locomotion.
The functioning of the haemocyanin of the terrestrial christmas island red crab gecarcoidea natalis and roles for organic modulators
Authors: Adamczewska Agnieszka M. , Morris Stephen 
Published: April 2021

ABSTRACT
Gecarcoidea natalis is a land crab that migrates annually several kilometres to breed. The O2-binding properties of haemocyanin in G. natalis were investigated in vitro to test the idea that the O2-binding properties of the haemocyanin of land crabs are not dependent on circulating modulators and to provide a model of haemocyanin functioning during exercise. The affinity of the haemocyanin for O2 decreased with increasing temperature (change in the heat of oxygenation; ΔH=−59 kJ mol−1 ). The haemocyanin of G. natalis apparently differs from that of other terrestrial crabs in showing haemocyanin O2 modulation by both organic and inorganic molecules. Haemocyanin O2-affinity was not affected by Mg2+ but was sensitive to changes in Ca2+ concentration (ΔlogP50/Δlog[Ca]=−0.61, where P50 is the partial pressure of O2 required for half-maximal O2 binding). The Bohr factor was modest (ϕ=−0.26±0.03, N=4, in whole haemolymph at 25 °C) and there was no specific effect of CO2 on the O2-binding properties of the haemocyanin. An increase in urate concentration increased haemocyanin O2-affinity, but the effect was linear (ΔlogP50/Δ[urate]=−0.06) and not logarithmic as is the case in other species. The effect of L-lactate on the haemocyanin O2-affinity in G. natalis was unique among the crustaceans, because an increase in L-lactate concentration decreased the haemocyanin O2-affinity. The effect of L-lactate on haemocyanin O2-affinity (ΔlogP50/Δlog[lactate]) was time- dependent and decreased from a maximum of 0.044 on day 1 to 0.001 after 4 days of storage at 4 °C. The presence of an unknown dialysable and unstable factor in the haemolymph is postulated to explain the time-dependent effect of L-lactate on haemocyanin O2-binding properties. Model oxygen equilibrium curves constructed for in vivo conditions showed that the reverse effect of L-lactate was advantageous by decreasing the O2-affinity of the haemocyanin beyond that predicted by the Bohr shift alone and assisted in O2 off-loading at the tissues. This effect of lactate can only provide an advantage if the gas-exchange organs maintain arterial O2 loading and thus is dependent on lung function in land crabs and must have occurred coincident with the evolution of these other features.
Sensorimotor Learning in Bumblebees: Long-Term Retention and Reversal Training
Authors: Chittka Lars 
Published: April 2021

ABSTRACT
Bumblebees were trained in biologically realistic sensorimotor tasks to test how learnt information from more than a single task is organised in memory. Bees (Bombus impatiens and Bombus occidentalis) learned to collect sucrose solution from the arms of small T-mazes. The reward was offered in the right arm of a maze when the entrance was marked blue, and in the left arm when the entrance was yellow. Bees were trained on either one or both of these tasks until after they had reached saturation in terms of speed and accuracy. One group of bees (Bombus impatiens) was evaluated for long-term retention by retesting (a) on the day after training and (b) between 3 and 4 weeks after training. Performance did not decline overnight but, when bees were tested after a delay of several weeks, an increase in error scores and times taken to negotiate mazes occurred. However, bees started out at a better level than during the initial training, indicating that information acquired during initial training had not been entirely erased from memory. A second group of bees (Bombus occidentalis) was tested to see whether it was possible to reverse the association between colour and direction, so that blue entrances now meant that the reward was on the left side, and yellow entrances meant that it was on the right. Bees reached saturation on both tasks as rapidly as they had during the initial training.
However, after a second reversal, bees chose directions randomly for several hundred trials, indicating that the first-learnt colour–direction associations had not been forgotten as a consequence of the first reversal: instead, information from the initial training must have been retained, but actively suppressed, causing difficulties in re-establishing the appropriate sensorimotor associations during the second reversal. Finally, a single Bombus impatiens worker was trained on only a single task, but with multiple reversals. The bee went through an intermediate phase when performance was poor until, after more than seven reversals, it required only three trials to assess that a reversal had taken place. This indicates that bees can learn actively to suppress irrelevant information, but only with an extended training schedule. Taken together, these results suggest that sensorimotor information is rarely lost from long-term memory, either during extended lay-offs or during interfering reversal training sessions. Organizing, correctly retrieving and suppressing information accumulated in memory seems to be more of a challenge than storing new information.
Distribution of Regional Cerebral Blood Flow in Voluntarily Diving Rats
Authors: Ollenberger G. P. , West N. H. 
Published: April 2021

ABSTRACT
The distribution of regional cerebral blood flow (rCBF) was examined in conscious, voluntarily diving rats using the brain blood flow tracer N-[14C]isopropyl-p-iodoamphetamine and quantitative autoradiography. A detailed examination of the regional distribution of cerebral blood flow revealed that almost all brain regions were hyperperfused during diving. During diving, rCBF increased by an average of 1.7-fold in 29 of the 33 brain regions examined, despite a 69.2% decrease in cardiac output. Only some regions of the basal ganglia (caudate-putamen and globus pallidus) and limbic areas (hippocampus and amygdala) did not increase rCBF significantly during diving. We determined that the increase in rCBF during diving is primarily due to a corresponding 20.9% decrease in cerebrovascular resistance. A significant increase in perfusion pressure during diving also potentially contributed to the increase in rCBF. Because some brain regions did not increase flow significantly during diving, these results suggest that not all brain regions participate equally in the global cerebrovascular response to diving. This study provides evidence to support the view that the brain is preferentially perfused during conscious voluntary diving in the rat. The mechanism(s) that probably produce the cerebrovascular changes during diving are discussed.