bluuebunny/crossref_metadata_2025_split huggingface dataset:
Postprandial Heat Increment Does not Substitute for Active Thermogenesis in Cold-Challenged Star-Nosed Moles (Condylura Cristata)
Authors: Campbell Kevin L. , Mcintyre Ian W. , Macarthur Robert A. 
Published: April 2021

ABSTRACT
The postprandial increase in metabolic rate associated with consuming, assimilating and excreting a meal is often termed the heat increment of feeding (HIF). The metabolic heat production of star-nosed moles, Condylura cristata, held at thermoneutrality was monitored for 4 h following a single 10 min session of feeding on a ration consisting of 0 g (controls), 3.5 g or 10 g of earthworms. Coefficients for metabolizable energy digestibility and digesta passage rate of earthworms fed to C. cristata were also determined. We then tested whether feeding-induced thermogenesis substitutes partially or completely for thermoregulatory heat production in these animals exposed to sub-thermoneutral air temperatures (9–24 °C). A single feeding on earthworms had both short- and long-term effects on the metabolic rate and respiratory exchange ratio of C. cristata. The observed short-term (0–65 min) rise in metabolic rate, assumed to be associated primarily with the physical costs of nutrient digestion, absorption and excretion, was similar to the calculated mean retention time (66.7±7.8 min; mean ± S.E.M., N=5) of this species. This component of the HIF represented 2.9 % of the food energy ingested by moles fed a single 3.5 g (13.21 kJ) meal of earthworms and 1.4 % of the food energy ingested by moles fed a single 7.5 g (28.09 kJ) meal of earthworms. At all test temperatures, resting metabolic rate typically remained above fasting levels for 1–4 h following ingestion of the high-protein earthworm diet. This protracted rise in metabolic rate, presumably associated with the biochemical costs of amino acid oxidation/gluconeogenesis and ureagenesis, averaged 12.8 % of the metabolizable energy and 8.7 % of the gross energy intake. Despite the potential thermoregulatory benefit, we found no evidence that biochemical HIF substitutes for facultative thermogenesis in star-nosed moles exposed to low air temperatures.
The Influence of Temperature on Power Production During Swimming: I. In Vivo Length Change and Stimulation Pattern
Authors: Swank Douglas M. , Rome Lawrence C. 
Published: April 2021

ABSTRACT
Ectothermal animals are able to locomote effectively over a wide range of temperatures despite low temperature reducing the power output of their muscles. It has been suggested that animals recruit more muscle fibres and faster fibre types to compensate for the reduced power output at low temperature, but it is not known how much low temperature actually reduces power output in vivo. ‘Optimized’ work-loop measurements, which are thought to approximate muscle function in vivo, give a Q10 of approximately 2.3 for power output of scup (Stenotomus chrysops) red muscle between 10 °C and 20 °C. However, because of the slower muscle relaxation rate at low temperatures, ‘optimizing’ work loops requires stimulation duration to be reduced and oscillation frequency to be decreased to obtain maximal power output. Previous fish swimming experiments suggest that similar optimization may not occur in vivo, and this may have substantial consequences in terms of muscle power generation and swimming at low temperatures.
To assess more precisely the effects of temperature on muscle performance and swimming, in the present study, we measured the length change, stimulation duration and stimulus phase of red muscle at various positions along scup swimming at several speeds at 10 °C and 20 °C. In a companion study, we determined the effects of temperature on in vivo power generation by driving muscle fibre bundles through these in vivo length changes and stimulation conditions, and measuring the resulting power output. The most significant finding from the present study is that, despite large differences in the in vivo parameters along the length of the fish (a decrease in stimulus duration, an increase in strain and a negative shift in phase) moving posteriorly, these parameters do not change with temperature. Thus, although the nervous system of fish could, in theory, compensate for slow muscle relaxation by greatly reducing muscle stimulation duration at low temperatures, it does not. This lack of compensation to low temperatures might reflect a potential limitation in neural control.
Na+/K+-ATPase Immunoreactivity in Branchial Chloride Cells of Oreochromis Mossambicus Exposed to Copper
Authors: Dang Zhichao , Lock Robert A. C. , Flik Gert , Wendelaar Bonga Sjoerd E. 
Published: April 2021

ABSTRACT
Chloride cells were identified by Na+/K+-ATPase immunocytochemistry at the light and electron microscope levels in gills of freshwater tilapia Oreochromis mossambicus. Turnover of chloride cells was enhanced by exposing the fish to waterborne copper (3.2 μmol l−1) for 14 days, as indicated by a 38 % increase in cells expressing proliferating cell nuclear antigen (PCNA) relative to controls. The expression of PCNA was most marked in the central area of the filamental epithelium, from where the chloride cells are thought to originate and migrate. In control fish, chloride cells were associated exclusively with the filamental epithelium. In both controls and copper-exposed fish, two chloride cell populations were seen after Na+/K+-ATPase immunostaining. These probably represent subpopulations of newly emerged chloride cells: (1) strongly stained cells (mature chloride cells) in the filamental and lamellar epithelium and (2) weakly stained cells, identified by electron microscopy as apoptotic and necrotic chloride cells, mainly in the filamental epithelium. Absolute numbers of mature chloride cells fell, while necrotic and apoptotic chloride cell numbers increased, in copper-exposed fish. A strong correlation could be established for gill Na+/K+-ATPase specific activity and the number of strongly stained chloride cells in controls and copper-exposed fish and for Na+/K+-ATPase specific activity and total numbers of immunoreactive cells in copper-exposed fish owing to an increased incidence of weakly staining cells.
Adaptations to a Terrestrial Existence in the Robber Crab Birgus Latro L. IX. Hormonal Control of Post-Renal Urine Reprocessing and Salt Balance in the Branchial Chamber
Authors: Morris Stephen , Greenaway Peter , Adamczewska Agnieszka M. , Ahern Mark D. 
Published: April 2021

ABSTRACT
The terrestrial robber crab Birgus latro L. regulates the composition of its final excretory product (termed P) depending on the availability of dietary salt by reabsorbing ions from urine passed over the gills. Laboratory and field-based studies investigated the nature of the mechanisms of control of this branchial ion uptake. B. latro were prepared such that their branchial chambers could be perfused with artificial urine, and the rate of ion transport from the artificial urine was determined. For B. latro acclimated to drinking fresh water, the rates of Na+ and Cl− uptake were more than four times those of crabs drinking 70 % sea water. Crabs were injected with either saline carrier or the same solution containing either dopamine or dibutyryl cyclic AMP (db-cAMP) (final concentration 8.7×10−7 mol l−1 haemolymph). Dopamine and db-cAMP inhibited Na+ and Cl− uptake in animals acclimated to fresh water and markedly reduced their gill Na+/K+-ATPase activity. Dopamine stimulated the production of cyclic AMP within the branchial epithelial cells. Dopamine, released from the pericardial organs, acts as a primary messenger, and cyclic AMP acts as a second messenger most likely promoting phosphorylation of membrane proteins. In contrast to aquatic brachyuran crabs, ion transport in B. latro, an anomuran, is controlled via an inhibitory effect. Terrestrial crabs normally have access to fresh water and must salvage salt from their urine, and a mechanism to down-regulate a normally active uptake system seems more appropriate to their ecology. Whether the control is stimulatory or inhibitory in the various air-breathing crabs may depend on the osmoregulatory abilities of their aquatic ancestors, but in either case has significant implications for the evolution of crustaceans to life on land. Further work must establish whether terrestrial brachyuran crabs are similar to B. latro and whether this crab is unique amongst the anomuran crabs.
What it Takes to Fly: The Structural and Functional Respiratory Refinements in Birds and Bats
Authors: Maina J. N. 
Published: April 2021

ABSTRACT
In absolute terms, flight is a highly energetically expensive form of locomotion. However, with respect to its cost per unit distance covered, powered flight is a very efficient mode of transport. Birds and bats are the only extant vertebrate taxa that have achieved flight. Phylogenetically different, they independently accomplished this elite mode of locomotion by employing diverse adaptive schemes and strategies. Integration of functional and structural parameters, a transaction that resulted in certain trade-offs and compromises, was used to overcome exacting constraints. Unique morphological, physiological and biochemical properties were initiated and refined to enhance the uptake, transfer and utilization of oxygen for high aerobic capacities. In bats, exquisite pulmonary structural parameters were combined with optimal haematological ones: a thin blood–gas barrier, a large pulmonary capillary blood volume and a remarkably extensive alveolar surface area in certain species developed in a remarkably large lung. These factors were augmented by, for example, exceptionally high venous haematocrits and haemoglobin concentrations. In birds, a particularly large respiratory surface area and a remarkably thin blood–gas (tissue) barrier developed in a small, rigid lung; a highly efficient cross-current system was fabricated within the parabronchi. The development of flight in only four animal taxa (among all the animal groups that have ever evolved; i.e. insects, the now-extinct pterosaurs, birds and bats) provides evidence for the enormous biophysical and energetic constraints that have stymied volancy. Bats improved a fundamentally mammalian lung to procure the large amounts of oxygen needed for flight. The lung/air sac system of birds is not therefore a prescriptive morphology for flight: the essence of its design can be found in the evolution of the reptilian lung, the immediate progenitor stock from which birds arose. The attainment of flight is a classic paradigm of the remarkable adaptability inherent in organismal and organic biology for countering selective pressures by initiating elegant morphologies and physiologies.
Immunolocalization of Dpfp1, a Byssal Protein of the Zebra Mussel Dreissena Polymorpha
Authors: Anderson Kevin E. , Waite J. Herbert 
Published: April 2021

ABSTRACT
The zebra mussel is one of only a few freshwater bivalves known to produce a byssus. This fibrous, proteinaceous and highly cross-linked structure allows the mussel to attach to a variety of substrata and contributes to its notoriety as a major freshwater biofouling species. We have successfully expressed a full-length version of Dreissena polymorpha foot protein 1 (Dpfp1), a putative byssal thread precursor, and have used the recombinant protein as an antigen for polyclonal antibody production. Antisera obtained from rabbits immunized with recombinant Dpfp1 recognize the protein in western blots of extracts from foot tissue and byssal threads. On the basis of this evidence, we conclude that Dpfp1 is a byssal precursor protein manufactured and stored in the foot of the mussel. Immunohistochemical localization of Dpfp1 suggests that the protein is localized in secretory granules in a large gland surrounding the ventral groove of the foot. Only a subset of these glandular cells stockpiles the protein, implying that the zebra mussel foot is a complex organ capable of several distinct secretory activities involved in byssal thread formation. The uniform distribution of Dpfp1-containing cells suggests that the protein is a significant load-bearing component of zebra mussel byssal threads, although a more rigorous test of this hypothesis awaits ultrastructural localization of the protein in mature byssal threads.
Ontogenetic Changes in Characteristics Required for Endothermy in Juvenile Black Skipjack Tuna (Euthynnus Lineatus)
Authors: Dickson Kathryn A. , Johnson Noel M. , Donley Jeanine M. , Hoskinson Jennifer A. , Hansen Michael W. , D’souza Tessier Jennifer 
Published: April 2021

ABSTRACT
To characterize better the development of endothermy in tunas, we assessed how the abilities to generate heat and to conserve heat within the aerobic, slow-twitch (red) myotomal muscle using counter-current heat exchangers (retia) change with size in juvenile black skipjack tuna (Euthynnus lineatus) above and below the hypothesized minimum size for endothermy of 207 mm fork length (FL). Early juvenile scombrids (10–77 mm FL) collected off the Pacific coast of Panama were raised to larger sizes at the Inter-American Tropical Tuna Commission Laboratory at Achotines Bay, Panama. Evidence of central and lateral rete blood vessels was found in E. lineatus as small as 95.9 mm FL and 125 mm FL, respectively. In larger E. lineatus juveniles (up to 244 mm FL), the capacity for heat exchange increased with fork length as a result of increases in rete length, rete width and the number of vessel rows. The amount (g) of red muscle increased exponentially with fork length in both E. lineatus (105–255 mm FL) and a closely related ectothermic species, the sierra Spanish mackerel Scomberomorus sierra (151–212 mm FL), but was greater in E. lineatus at a given fork length. The specific activity (international units g−1) of the enzyme citrate synthase in red muscle, an index of tissue heat production potential, increased slightly with fork length in juvenile E. lineatus (84.1–180 mm FL) and S. sierra (122–215 mm FL). Thus, total red muscle heat production capacity (red muscle citrate synthase activity per gram times red muscle mass in grams) increased with fork length, primarily because of the increase in red muscle mass. Below 95.9 mm FL, E. lineatus cannot maintain red muscle temperature (Tm) above the ambient water temperature (Ta) because juveniles of this size lack retia. Above 95.9 mm FL, the relationship between Tx (Tm−Ta) and FL for E. lineatus diverges from that for the ectothermic S. sierra because of increases in the capacities for both heat production and heat retention that result in the development of endothermy.
Maximum Sustainable Speeds and Cost of Swimming in Juvenile Kawakawa Tuna (Euthynnus Affinis) and Chub Mackerel (Scomber Japonicus)
Authors: Sepulveda Chugey , Dickson Kathryn A. 
Published: April 2021

ABSTRACT
Tunas (Scombridae) have been assumed to be among the fastest and most efficient swimmers because they elevate the temperature of the slow-twitch, aerobic locomotor muscle above the ambient water temperature (endothermy) and because of their streamlined body shape and use of the thunniform locomotor mode. The purpose of this study was to test the hypothesis that juvenile tunas swim both faster and more efficiently than their ectothermic relatives. The maximum sustainable swimming speed (Umax, the maximum speed attained while using a steady, continuous gait powered by the aerobic myotomal muscle) and the net cost of transport (COTnet) were compared at 24 °C in similar-sized (116–255 mm fork length) juvenile scombrids, an endothermic tuna, the kawakawa (Euthynnus affinis) and the ectothermic chub mackerel (Scomber japonicus). Umax and COTnet were measured by forcing individual fish to swim in a temperature-controlled, variable-speed swimming tunnel respirometer. There were no significant interspecific differences in the relationship between Umax and body mass or fork length or in the relationship between COTnet and body mass or fork length. Muscle temperatures were elevated by 1.0–2.3 °C and 0.1–0.6 °C above water temperature in the kawakawa and chub mackerel, respectively. The juvenile kawakawa had significantly higher standard metabolic rates than the chub mackerel, because the total rate of oxygen consumption at a given swimming speed was higher in the kawakawa when the effects of fish size were accounted for. Thus, juvenile kawakawa are not capable of higher sustainable swimming speeds and are not more efficient swimmers than juvenile chub mackerel.
Effects of Feeding on Arterial Blood Gases in the American Alligator Alligator Mississippiensis
Authors: Busk Morten , Overgaard Johannes , Hicks James W. , Bennett Albert F. , Wang Tobias 
Published: April 2021

ABSTRACT
Reptiles habitually ingest large meals at infrequent intervals, leading to changes in acid–base status as the net secretion of acid to the stomach causes a metabolic alkalosis (the alkaline tide). In chronically cannulated and undisturbed amphibians and reptiles, the pH changes in arterial blood are, nevertheless, reduced by a concomitant respiratory acidosis (increased caused by a relative hypoventilation). Alligators (Alligator mississippiensis) have been reported to exhibit exceptionally large increases in plasma [HCO3−] following feeding, but these studies were based on blood samples obtained by cardiac puncture, so stress and disturbance may have affected the blood gas levels. Furthermore, crocodilian haemoglobin is characterised by a unique binding of HCO3− that act to reduce blood oxygen-affinity, and it has been proposed that this feature safeguards oxygen offloading by counteracting pH effects on blood oxygen-affinity. Therefore, to study acid–base regulation and the interaction between the alkaline tide and oxygen transport in more detail, we describe the arterial blood gas composition of chronically cannulated and undisturbed alligators before and after voluntary feeding (meal size 7.5±1 % of body mass).
Digestion was associated with an approximately fourfold increase in metabolic rate (from 0.63±0.04 to 2.32±0.24 ml O2 min−1 kg−1) and was accompanied by a small increase in the respiratory gas exchange ratio. The arterial of fasting alligators was 60.3±6.8 mmHg (1 mmHg=0.133 kPa) and reached a maximum of 81.3±2.7 mmHg at 96 h following feeding; there was only a small increase in lactate levels, so the increased metabolic rate seems to be entirely aerobic. Plasma [HCO3−] increased from 24.4±1.1 to 36.9±1.7 mmol l−1 (at 24 h), but since arterial increased from 29.0±1.1 to 36.8±1.3 mmHg, arterial pH remained virtually unaffected (changing from 7.51±0.01 to 7.58±0.01 at 24 h). The changes in plasma [HCO3−] were mirrored by equimolar reductions in plasma [Cl−]. The in vitro blood oxygen-affinity was reduced during the post-prandial period, whereas the estimated in vivo blood oxygen-affinity remained virtually constant. This supports the view that the specific HCO3− effect prevents an increased blood oxygen-affinity during digestion in alligators.
Sustaining Olfaction at Low Salinities: Mapping Ion Flux Associated with the Olfactory Sensilla of the Blue Crab Callinectes Sapidus
Authors: Gleeson Richard A. , Hammar Katherine , Smith Peter J. S. 
Published: April 2021

ABSTRACT
To test the hypothesis of a diffusion-generated, ionic/ osmotic microenvironment within the olfactory sensilla (aesthetascs), flux gradients of Ca2+ and K+ associated with the external surfaces of these sensilla were spatially mapped using self-referencing, ion-selective microelectrodes. Blue crabs (Callinectes sapidus) acclimated to low-salinity conditions (15 % sea water and fresh water) showed a net efflux of ions from the aesthetascs. The region of maximum flux associated with each aesthetasc conformed to that predicted from structural data and corresponded to the permeable region of the cuticle separating the olfactory dendrites from the external environment. Estimates of net flux from the entire tuft of aesthetascs for both Ca2+ and K+ fell within the predicted range on the basis of comparisons with 22Na+ flux measured previously and assuming a passive diffusion model of ion movement from the hemolymph to the sensillar lymph and, ultimately, to the external environment. The maximum concentrations of these ions measured deep within the tuft are discussed in the light of a potential across the aesthetascs that may limit ion efflux at low salinities.
Flexibility in Basal Metabolic Rate and Evaporative Water Loss Among Hoopoe Larks Exposed to Different Environmental Temperatures
Authors: Williams Joseph B. , Tieleman B. I. 
Published: April 2021

ABSTRACT
The ‘energy demand’ hypothesis for short-term adjustments in basal metabolic rate (BMR) posits that birds adjust the size of their internal organs relative to food intake, a correlate of energy demand. We tested this hypothesis on hoopoe larks (Alaemon alaudipes), inhabitants of the Arabian desert, by acclimating birds for 3 weeks at 15 °C and at 36 °C, then measuring their BMR and total evaporative water loss (TEWL). Thereafter, we determined the dry masses of their brain, heart, liver, kidney, stomach, intestine and muscles of the pectoral region. Although mean body mass did not differ initially between the two groups, after 3 weeks, birds in the 15 °C group had gained mass (44.1±6.5 g), whereas larks in the 36 °C group had maintained a constant mass (36.6±3.6 g; means ± S.D., N=6).
Birds in the 15 °C group had a mean BMR of 46.8±6.9 kJ day−1, whereas birds in the 36 °C group had a BMR of 32.9±6.3 kJ day−1, values that were significantly different when we controlled for differences in body mass. When measured at 35 °C, larks in the cold-exposure group had a TEWL of 3.55±0.60 g H2O day−1, whereas TEWL for birds in the 36 °C group averaged 2.23±0.28 g H2O day−1, a difference of 59.2 %. Mass-independent TEWL differed significantly between groups.
Larks in the 15 °C group had a significantly larger liver, kidney and intestine than larks in the 36 °C group. The total increase in organ mass contributed 14.3 % towards the total mass increment in the cold exposure group. Increased food intake among larks in the cold group apparently resulted in enlargement of some of the internal organs, and the increase in mass of these organs required a higher rate of oxygen uptake to support them. As oxygen demands increased, larks apparently lost more evaporative water, but the relationship between increases in BMR and TEWL remains unresolved.
Sub-Ice Foraging Behavior of Emperor Penguins
Authors: Ponganis P. J. , Dam R. P. Van , Marshall G. , Knower T. , Levenson D. H. 
Published: April 2021

ABSTRACT
Emperor penguins (Aptenodytes forsteri) were equipped with a remote underwater video camera, the Crittercam, to evaluate sub-ice foraging behavior while the birds dived from an isolated dive hole. Three birds dived and foraged successfully for 1 h periods after being trained to wear and to dive with a harness for camera attachment. Video and depth profile recordings revealed that emperor penguins travel at shallow depths (&lt;50 m), ascend to the undersurface of the ice to feed on fish, and descend back to depth to return to the exit hole. Although the mean durations of dives of individual birds with the Crittercam were 21–35 % shorter than the diving durations of these same birds without the camera, the dive profiles in both situations were similar, thus demonstrating a similar foraging strategy in birds diving without the camera. Despite shorter diving durations with the camera, the penguins were still successful at prey capture in 80 % of 91 dives greater than 1 min in duration. Prey included the sub-ice fish Pagothenia borchgrevinki. Hunting ascents (from depth to within 5 m of the surface) occurred in 85 % of dives, ranged from zero to three per dive, and were associated with successful prey capture in 77 % of 128 ascents. Occasionally, several fish were captured during a single ascent. These observations and this application of video technology create a model for further physiological and behavioral studies of foraging, and also emphasize the potential importance of shallow dives as sources of food intake for emperor penguins during foraging trips to sea.