bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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

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.
Theoretical and Empirical Scaling Patterns and Topological Homology in Bone Trabeculae
Authors: Swartz Sharon M. , Parker Antigone , Huo Christine
Published: April 2021

Trabecular or cancellous bone is a major element in the structural design of the vertebrate skeleton, but has received little attention from the perspective of the biology of scale. In this study, we investigated scaling patterns in the discrete bony elements of cancellous bone. First, we constructed two theoretical models, representative of the two extremes of realistic patterns of trabecular size changes associated with body size changes. In one, constant trabecular size (CTS), increases in cancellous bone volume with size arise through the addition of new elements of constant size. In the other model, constant trabecular geometry (CTG), the size of trabeculae increases isometrically. These models produce fundamentally different patterns of surface area and volume scaling. We then compared the models with empirical observations of scaling of trabecular dimensions in mammals ranging in mass from 4 to 40×106 g. Trabecular size showed little dependence on body size, approaching one of our theoretical models (CTS). This result suggests that some elements of trabecular architecture may be driven by the requirements of maintaining adequate surface area for calcium homeostasis. Additionally, we found two key consequences of this strongly negative allometry. First, the connectivity among trabecular elements is qualitatively different for small versus large animals; trabeculae connect primarily to cortical bone in very small animals and primarily to other trabeculae in larger animals. Second, small animals have very few trabeculae and, as a consequence, we were able to identify particular elements with a consistent position across individuals and, for some elements, across species. Finally, in order to infer the possible influence of gross differences in mechanical loading on trabecular size, we sampled trabecular dimensions extensively within Chiroptera and compared their trabecular dimensions with those of non-volant mammals. We found no systematic differences in trabecular size or scaling patterns related to locomotor mode.
Kinematic, Aerodynamic and Anatomical Mechanisms in the Slow, Maneuvering Flight of Pigeons
Authors: Warrick Douglas R. , Dial Kenneth P.
Published: April 2021

A high-speed (200 Hz) infrared video system was used in a three-dimensional analysis of pigeon wing and body kinematics to determine the aerodynamic and anatomical mechanisms they use to produce force asymmetries to effect a turn during slow (3 m s−1) flight. Contrary to our expectations, pigeons used downstroke velocity asymmetries, rather than angle of attack or surface area asymmetries, to produce the disparities in force needed for directional changes. To produce a bank, a velocity asymmetry is created early in the downstroke and, in the majority of cases, then reversed at the end of the same downstroke, thus arresting the rolling angular momentum. When the velocity asymmetry was not reversed at the end of downstroke, the arresting force asymmetry was produced during upstroke, with velocity asymmetries creating disparate drag forces on the wings. Rather than using subtle aerodynamic variables to produce subtle downstroke force asymmetries, pigeons constantly adjust their position using a series of large alternating and opposing forces during downstroke and upstroke. Thus, a pigeon creates a precise ‘average’ body position (e.g. bank angle) and flight path by producing a series of rapidly oscillating movements. Although the primary locomotor event (downstroke) is saltatory, maneuvering during slow flight should be considered as a product of nearly continuous, juxtaposed force generation throughout the wingbeat cycle. Further, viewing upstroke as more than stereotypical, symmetrical wing recovery alters the evolutionary and functional context of investigations into the musculoskeletal mechanisms and the associated neural control involved in this unique kinematic event.
Forewing Movements and Intracellular Motoneurone Stimulation in Tethered Flying Locusts
Authors: Hedwig B. , Becher G.
Published: April 2021

A new optoelectronic method was used for the measurement of wing movements in tethered flying locusts. The method is based on laser light coupled into a highly flexible optical fibre fastened to a forewing. A dual-axis position-sensing photodiode, aligned to the wing hinge, revealed the flapping, i.e. up–down movement, and lagging, i.e. forward–backward movement, of the wingtip as indicated by the emitted light. Measurements were combined with electromyographic recordings from flight muscles and with intracellular recording and stimulation of flight motoneurones. Compared with muscle recordings, intracellular recordings showed an increase in the variability of motoneurone activity. Stimulation of flight motoneurones reliably caused distinct effects on wing movements. Inhibition of elevator (MN83, MN89) activity led to a decrease in the amplitude of the upstroke. Inhibition of depressor (MN97) activity reduced the amplitude of the downstroke and sometimes stopped flight behaviour. An increase in MN97 activity caused a reduction in the extent of the upward movement and prolonged the flight cycle.
Crocodiles as dinosaurs: behavioural thermoregulation in very large ectotherms leads to high and stable body temperatures
Authors: Seebacher Frank , Grigg Gordon C. , Beard Lyn A.
Published: April 2021

Empirical field data describing daily and seasonal cycles in body temperature (Tb) of free-ranging Crocodylus porosus (32–1010 kg) can be predicted by a mathematical analysis. The analysis provides a mechanistic explanation for the decreased amplitude of daily cycles in Tb and the increase in ‘average’ Tb with increasing mass. Assessments of ‘average’ daily Tb were made by dividing the integral of the difference between measured values of Tb and minimum operative temperature by the period of integration, to yield a thermal index expressing relative ‘warmth’ of crocodiles. The average daily Tb of a 1010 kg crocodile was 3.7 °C warmer than that of a 42 kg individual in summer and 1.9 °C warmer than that of a 32 kg individual in winter. The success of this mathematical approach confirms that crocodiles are simple ectotherms and that there is unlikely to be a significant contribution to their thermal biology from physiological mechanisms. Behaviour, however, is very important even in large individuals. Crocodiles in the field typically move daily between land and water in cycles that vary seasonally. We predicted Tb for the reverse of these behavioural cycles, which more than doubled seasonal fluctuations in Tb compared with the observed fluctuations. We were also able to predict the Tb of very large, dinosaur-sized crocodiles in a similar climate to that at our study site. A 10 000 kg ‘crocodile’, for example, would be expected to have a Tb of 31 °C in winter, varying by less than 0.1 °C during a day when operative temperatures varied by nearly 20 °C, from 20 to 38 °C. The study confirms that, in low latitudes at least, large dinosaurs must have had an essentially high and stable value of Tb, without any need for endothermy. Also, access to shade or water must have been crucial for the survival of large dinosaurs at low latitudes. Furthermore, the finding of increasing ‘average’ Tb as ectotherms grow larger may have implications for the metabolic rates of very large reptiles, because the Q10 effect could counteract the downscaling of metabolic rate with mass, an effect that seems not to have been recognised previously.
Elastic energy storage and release in white muscle from dogfish Scyliorhinus canicula
Authors: Lou Fang , Curtin N. A. , Woledge R. C.
Published: April 2021

The production of work by the contractile component (CC) and the storage and release of work in the elastic structures that act in series (the series elastic component, SEC) with the contractile component were measured using white muscle fibres from the dogfish Scyliorhinus canicula. Heat production was also measured because the sum of work and heat is equivalent to the energy cost of the contraction (ATP used). These energy fluxes were evaluated in contractions with constant-velocity shortening either during stimulation or during relaxation. The muscle preparation was tetanized for 0.6 s and shortened by 1 mm (approximately 15 % of L0) at 3.5 or 7.0 mm s−1 (approximately 15 or 30 % of V0), where L0 is the muscle length at which isometric force is greatest and V0 is the maximum velocity of shortening. In separate experiments, the stiffness of the SEC was characterized from measurements of force responses to step changes in the length of contracting muscle. Using the values of SEC stiffness, we evaluated separately the work and heat associated with the CC and with the SEC. The major findings were (1) that work stored in the SEC could be completely recovered as external work when shortening occurred during relaxation (none of the stored work being degraded into heat) and (2) that, when shortening occurred progressively later during the contraction, the total energy cost of the contraction declined towards that of an isometric contraction.
Soaring and Non-Soaring Bats of the Family Pteropodidae (Flying Foxes, Pteropus Spp.): Wing Morphology and Flight Performance
Authors: Lindhe Norberg Ulla M. , Brooke Anne P. , Trewhella William J.
Published: April 2021

On oceanic islands, some large diurnal megachiropteran bat species (flying foxes; Pteropus spp.) frequently use thermal or slope soaring during foraging flights to save energy. We compared the flight morphology and gliding/soaring performance of soaring versus non-soaring Pteropus species, one pair on American Samoa and one pair on the Comoro Islands, and two other soaring/flap-gliding species and one non-soaring species. We predicted that the soaring species should have a lower body mass, longer wings and, hence, lower wing loadings than those species that use mainly flapping flight. This would give a lower sinking speed during gliding, a higher glide ratio, and enable the bats to make tighter turns with lower sinking speeds than in the non-soaring species. We theoretically calculated the gliding and circling performances of both the soaring and non-soaring species.

Our results show that there are tendencies towards longer wings and lower wing loadings in relation to body size in the gliding/soaring flying foxes than in the non-soaring ones. In the species-pair comparison of the soaring and non-soaring species on American Samoa and the Comoro Islands, the soarers on both islands turn out to have lower wing loadings than their non-soaring partners in spite of opposite size differences among the pairs. These characteristics are in accordance with our hypothesis on morphological adaptations. Most differences are, however, only significant at a level of P<0.1, which may be due to the small sample size, but overlap also occurs. Therefore, we must conclude that wing morphology does not seem to be a limiting factor preventing the non-soarers from soaring. Instead, diurnality in the soaring species seems to be the ultimate determinant of soaring behaviour.

The morphological differences cause visible differences in soaring and gliding performance. The glider/soarers turn out to have lower minimum sinking speeds, lower best glide speeds and smaller turning radii than the non-soarers. When the wing measurements and soaring performance are normalized to a body mass of 0.5 kg for all species, the minimum sinking speed becomes significantly lower (P<0.05) in the three soaring and the one flap-gliding species (0.63 m s−1) than in the three non-soaring species (0.69 m s−1). Interestingly, the zones in the diagrams for the glide polars and circling envelopes of these similar-sized bats become displaced for the glider/soarers versus the non-soarers. The glide polars overlap slightly only at the gliding speeds appropriate for these bats, whereas the circling envelopes do not overlap at the appropriate bank angles and turning radii. This points towards adaptations for better gliding/soaring performance in the soaring and gliding species.
The Physiology of Salinity Tolerance in Larvae of two Species of Culex Mosquitoes: The Role oF Compatible Solutes
Authors: Patrick Marjorie L. , Bradley Timothy J.
Published: April 2021

We investigated the physiological basis for differences in salinity tolerance ranges in mosquito larvae of the genus Culex. We examined the response of larvae of C. quinquefasciatus, a freshwater obligate, and C. tarsalis, a euryhaline osmoconformer, following transfer from fresh water to 34 % sea water. Hemolymph Na+ and Cl− levels increased similarly in both species, indicating that ion regulation does not differ under these conditions. C. quinquefasciatus responded to increased environmental salinity with increased hemolymph levels of serine, but suffered a significant reduction in levels of trehalose. C. tarsalis responded to increased environmental salinity with increased hemolymph levels of both proline and trehalose. When C. tarsalis larvae were held in 64 % sea water, which C. quinquefasciatus larvae cannot tolerate, hemolymph proline and trehalose were accumulated approximately 50-fold and twofold, respectively, relative to freshwater values. We found that proline serves as both an intra- and extracellular compatible solute in C. tarsalis, the first such circumstance documented in an animal in response to increased environmental salinity. Analyses of the acute responses of the two species to an increase in salinity (from 30 % to 50 % sea water) indicate that larvae of C. tarsalis are able to volume-regulate via drinking and to attenuate increases in hemolymph NaCl concentration using unknown mechanisms during large, rapid increases in salinity.
Differential Branchial and Renal Handling of Urea, Acetamide and Thiourea in the Gulf Toadfish Opsanus Beta: Evidence for Two Transporters
Authors: McDonald M. Danielle , Wood Chris M. , Wang Yuxiang , Walsh Patrick J.
Published: April 2021

The possible presence of a urea transporter in the kidney of the gulf toadfish (Opsanus beta) and further characterization of the pulsatile facilitated transporter previously identified in its gills were investigated by comparing the extra-renal and renal handling of two urea analogues with the handling of urea. Toadfish were fitted with caudal artery and indwelling urinary ureteral catheters and injected with an iso-osmotic dose of 14C-labelled urea analogue (acetamide or thiourea) calculated to bring plasma analogue concentrations close to plasma urea concentrations. Branchial permeabilities to urea, acetamide and thiourea were similar during non-pulsing periods and all increased during pulse events, although urea permeability was greater than analogue permeability during pulses. The incidence and magnitude of acetamide and urea pulses at the gills were significantly correlated, acetamide pulses being 35–50 % of the size of urea pulses. However, the thiourea and urea pulses at the gills were only weakly correlated, thiourea pulses being less than 16 % of the size of urea pulses. Thiourea inhibited branchial urea excretion by reducing the pulse frequency. The renal handling of thiourea and urea were similar in that both substances were more concentrated in the urine than in the plasma, whereas acetamide was found in equal concentrations in the urine and plasma. Urea and thiourea were secreted 2–3 times more effectively than Cl− and water, whereas acetamide was secreted at a similar relative rate. The differential handling of the urea analogues by the gills and kidney indicates the presence of a different, possibly unique, transporter in the kidney. The movement of thiourea and urea into the renal tubule against an apparent concentration gradient suggests the presence of an active transport mechanism.
Concentrations of Myoglobin and Myoglobin mRNA in Heart Ventricles From Antarctic Fishes
Authors: Moylan Thomas J. , Sidell Bruce D.
Published: April 2021

We used a combined immunochemical and molecular approach to ascertain the presence and concentrations of both the intracellular oxygen-binding hemoprotein myoglobin (Mb) and its messenger RNA (mRNA) in 13 of 15 known species of Antarctic channichthyid icefishes. Mb protein is present in the hearts of eight species of icefishes: Chionodraco rastrospinosus, Chionodraco hamatus, Chionodraco myersi, Chaenodraco wilsoni, Pseudochaenichthys georgianus, Cryodraco antarcticus, Chionobathyscus dewitti and Neopagetopsis ionah. Five icefish species lack detectable Mb protein: Chaenocephalus aceratus, Pagetopsis macropterus, Pagetopsis maculatus, Champsocephalus gunnari and Dacodraco hunteri. Mb concentrations range from 0.44±0.02 to 0.71±0.08 mg Mb g−1 wet mass in heart ventricle of species expressing the protein. A Mb-mRNA-specific cDNA probe was used to quantify mRNA in five Mb-expressing icefishes. Mb mRNA was found in low but detectable amounts in Champsocephalus gunnari, one of the species lacking detectable Mb. Mb mRNA concentrations in heart ventricle from Mb-expressing species ranged from 0.78±0.02 to 16.22±2.17 pg Mb mRNA μg−1 total RNA). Mb protein and Mb mRNA are absent from the oxidative skeletal muscle of all icefishes. Steady-state concentrations of Mb protein do not parallel steady-state concentrations of Mb mRNA within and among icefishes, indicating that the concentration of Mb protein is not determined by the size of its mRNA pool.
Orientation Discrimination Independent of Retinal Matching by Blowflies
Authors: Campbell Holly R.
Published: April 2021

Blowflies, Phaenicia sericata, can be trained to discriminate in a learning paradigm in which one of the two visual cues is positively rewarded. Retinotopic matching of a learned visual image to the same retinal location from viewing to viewing has been hypothesized to underlie visual pattern learning and memory in insects. To address the theory of retinotopic matching, a detailed analysis was made of the flies’ body orientations during learned discriminations between +45 ° and −45 ° gratings. Initial approaches to the positive rewarded visual cue did not originate from the same spatial location within the behavioral arena with respect to the visual cues; thus, individual flies approached the positive cue from a different vantage point from trial to trial. During initial approaches to the rewarded visual cue, the distributions of body angles with respect to the cue were different from trial to trial for each individual. These data suggest that Phaenicia sericata can learn a visual pattern with one eye region and later recognize the same pattern with another eye region. Thus, retinotopic matching is not necessary for the recognition of pattern orientation in the experimental paradigm used here. The average amount of head turning in the yaw plane was too small to compensate for the changes in body orientation exhibited by the flies. Flies view the visual patterns with distinct retinal regions from trial to trial during orientation discrimination.
The Salivary Adenosine Deaminase Activity of the Mosquitoes Culex quinquefasciatus and Aedes aegypti
Authors: Ribeiro José M. C. , Charlab Rosane , Valenzuela Jesus G.
Published: April 2021

A cDNA coding for a protein with significant similarity to adenosine deaminase (ADA) was found while randomly sequencing a cDNA library constructed from salivary gland extracts of adult female Culex quinquefasciatus. Prompted by this result, we found high ADA activities in two culicine mosquitoes, Culex quinquefasciatus and Aedes aegypti, but not in the anopheline Anopheles gambiae. Homogenates from Culex quinquefasciatus also have an AMP deaminase activity that is three times greater than the ADA activity, whereas in Aedes aegypti the AMP deaminase activity is less than 10% of the ADA activity. Evidence for secretion of ADA during blood feeding by Aedes aegypti includes the presence of ADA activity in warm solutions probed through a membrane by mosquitoes and in serotonin-induced saliva and a statistically significant reduction in the levels of the enzyme in Aedes aegypti following a blood meal. We could not demonstrate, however, that C. quinquefasciatus secrete ADA in their saliva. Male Aedes aegypti and C. quinquefasciatus, which do not feed on blood, have less than 3% of the levels of ADA found in females. We propose that ADA activity in A. aegypti may help blood feeding by removing adenosine, a molecule associated with both the initiation of pain perception and the induction of mast cell degranulation in vertebrates, and by producing inosine, a molecule that potently inhibits the production of inflammatory cytokines. The role of salivary ADA in Culex quinquefasciatus remains unclear.
Cuttlefish camouflage: visual perception of size, contrast and number of white squares on artificial checkerboard substrata initiates disruptive coloration
Authors: Chiao Chuan-Chin , Hanlon Roger T.
Published: April 2021

We investigated some visual background features that influence young cuttlefish, Sepia pharaonis, to change their skin patterning from ‘general resemblance’ of the substratum to disruptive coloration that breaks up their body form. Using computer-generated black/white checkerboard patterns as substrata, we first found that the size of the white squares had to be within a certain narrow range (relative to the size of the cuttlefish ‘white square’) for the animal to exhibit disruptive skin patterning. Second, given the appropriate size of checker, cuttlefish regulated their disruptive skin patterns according to the contrast between white and black squares. Third, by manipulating the number of white squares on a black background, we found that as few as four white squares among 316 black squares (or 1.25%) produced disruptive patterning, yet increasing the number of white squares to 20, 40 or 80 did not increase the frequency of appearance of the cuttlefish ‘white square’, but only its clarity of expression. These results demonstrate that the size, contrast and number of white objects in the surrounding substratum influence the production and expression of disruptive skin patterns in young cuttlefish.

Movies available on-line
Suppression of allograft rejection in the spongeSuberites domunculaby FK506 and expression of genes encoding FK506-binding proteins in allografts
Authors: Müller Werner E. G. , Steffen Renate , Lorenz Bernd , Batel Renato , Kruse Michael , Krasko Anatoli , Müller Isabel M. , Schröder Heinz C.
Published: April 2021

Porifera (sponges) are, evolutionarily, the oldest metazoan phylum. Recent molecular data suggest that these animals possess molecules similar to and homologous with those of the innate and adaptive immune systems of higher Metazoa. Applying the biological system of parabiosis and the technique of differential display of mRNA, two cDNAs encoding putative FK506-binding proteins were isolated. FK506 is successfully used in clinics as a drug to prevent allograft rejection and is toxic to Suberites domuncula cells in vitro at doses above 100ng ml−1. Autograft fusion of transplants from S. domuncula was not affected by FK506. Allograft non-fusion was not affected by FK506 at toxic doses; however, at the non-toxic dose of 20ng ml−1, the allografts fused with each other. It is shown that at the attachment zone in untreated and (particularly drastic) in FK506-treated allografts, expression of the genes encoding the FK506-binding proteins is upregulated. These data indicate that the drug FK506 suppresses allograft rejection in S. domuncula, most probably via interaction with expression of the gene coding for the FK506-binding proteins.
Physiological characterisation of antennal mechanosensory descending interneurons in an insect (Gryllus bimaculatus, Gryllus campestris) brain
Authors: Gebhardt Michael , Honegger Hans-Willi
Published: April 2021

We investigated five different descending brain interneurons with dendritic arborizations in the deutocerebrum in the crickets Gryllus bimaculatus and G. campestris. These interneurones convey specific antennal mechanosensory information to the ventral nerve cord and all responded to forced antennal movements. These interneurones coded for velocity and showed preferences for distinct sectors of the total range of antennal movements. Their axons descended into the posterior connective either ipsilateral or contalateral to the cell body. Electrical stimulation of sensory nerves indicated that the interneurons received input from different afferents of the two antennal base segments. One interneuron had a particularly large axon with a conduction velocity of 4.4ms−1. This was the only one of the five interneurons that also received visual input. Its activity was reduced during voluntary antennal movements. The reduction in activity occurred even after de-efferentation of the antenna, indicating that it had a central origin. Although we do not have experimental evidence for behavioural roles for the descending antennal mechanosensory interneurons, the properties described here suggest an involvement in the perception of objects in the path of the cricket.
Seasonal variation in energy expenditure, water flux and food consumption of Arabian oryx Oryx leucoryx
Authors: Williams Joseph B. , Ostrowski Stéphane , Bedin Eric , Ismail Khairi
Published: April 2021

We report on the energy expenditure and water flux, measured in the laboratory and in the field, of the Arabian oryx Oryx leucoryx, the largest desert ruminant for which measurements of the field metabolic rate of free-living individuals have been made using doubly labeled water. Prior to extirpation of this species in the wild in 1972, conservationists sequestered a number of individuals for captive breeding; in 1989, oryx were reintroduced in Saudi Arabia into Mahazat as-Sayd (2244km2). Apart from small pools of water available after rains, oryx do not have free-standing water available for drinking and therefore rely on grasses that they eat for preformed water intake as well as their energy needs. We tested whether oryx have a reduced fasting metabolic rate and total evaporative water loss (TEWL) in the laboratory, as do some other arid-adapted mammals, and whether oryx have high field metabolic rates (FMRs) and water influx rates (WIRs), as predicted by allometric equations for large arid-zone mammals. We measured FMR and WIR during the hot summer, when plant moisture content was low and ambient temperatures were high, and after winter rains, when the water content of grasses was high.

For captive oryx that weighed 84.1kg, fasting metabolic rate averaged 8980kJday−1, 16.7% lower than predictions for Artiodactyla. Our own re-analysis of minimal metabolic rates among Artiodactyla yielded the equation: logV̇O2=−0.153+0.758logM, where V̇O2 is the rate of oxygen uptake in lh−1 and M is body mass in kg. Fasting metabolic rate of oryx was only 9.1% lower than predicted, suggesting that they do not have an unusually low metabolic rate. TEWL averaged 870.0mlday−1, 63.9% lower than predicted, a remarkably low value even compared with the camel, but the mechanisms that contribute to such low rates of water loss remain unresolved.

For free-living oryx, FMR was 11076kJday−1 for animals with a mean body mass of 81.5kg during summer, whereas it was 22081kJday−1 for oryx in spring with a mean body mass of 89.0kg, values that were 48.6% and 90.4% of allometric predictions, respectively. During summer, WIR averaged 1310mlH2Oday−1, whereas in spring it was 3438mlH2Oday−1. Compared with allometric predictions, WIR was 76.9% lower than expected in summer and 43.6% lower in spring. We found no evidence to support the view that the WIR of large desert ungulates is higher than that of their mesic counterparts. On the basis of the WIR of the oryx averaged over the year and the water contents of plants in their diet, we estimated that an oryx consumes 858kg of dry matter per year.
Nuclear p26, a small heat shock/α-crystallin protein, and its relationship to stress resistance in Artemia franciscana embryos
Authors: Willsie Julia K. , Clegg James S.
Published: April 2021

The role of the small heat shock/α-crystallin protein, p26, in transcription in Artemia franciscana embryos was examined using isolated nuclei, containing either control or elevated levels of p26, in transcription run-on assays. Heat shock or anoxia in vivo and acid pH in vitro were used to transfer p26 into nuclei. The results suggest that parameters other than, or in addition to, p26 are responsible for the reduced transcription rates observed and that decreases in pHi are involved. In vivo experiments indicate that RNA synthesis and, to a lesser extent, protein synthesis are downregulated in intact embryos recovering from heat shock and that the precursor pool is not limiting. Confocal microscopy confirmed that p26 moves into nuclei in response to heat shock and anoxia in vivo, and to low pH in vitro, and indicated that the nuclear distribution of p26 is similar under all three conditions. We present evidence that unstressed (control) embryos containing p26 in all their nuclei will not hatch, even under permissive conditions, and propose that they are unable to terminate diapause.

Potential nuclear targets of p26 chaperone activity are discussed.