bluuebunny/crossref_metadata_2025 huggingface dataset:
The Contribution of a Ca2+-Activated Cl− Conductance to Amino-Acid-induced Inward Current Responses of Ciliated Olfactory Neurons of the Rainbow Trout
Authors: Sato Koji , Suzuki Noriyo
Published: April 2021

To determine whether amino-acid-induced inward currents of ciliated olfactory receptor neurons (ORNs) in rainbow trout (Oncorhynchus mykiss) include a Ca2+-activated Cl− conductance, we first studied changes in reversal potential and the current/voltage relationships of the responses of ORNs to an amino acid mixture (L-alanine, L-arginine, L-glutamate and L-norvaline; all 10 mmol l−1) with different concentrations of Na+ and Cl− in the perfusion and recording pipette solutions. We also examined the effects of six different Cl− channel blockers on the responses of ORNs using a conventional whole-cell voltage-clamp technique. The amino acid mixture and one blocker were applied focally to the cilia of ORNs using a double-barrelled micropipette and a pressure ejection system. The expected shifts in reversal potential, indicating the contribution of the Ca2+-activated Cl− conductance, occurred in both positive and negative directions depending on the external and internal Na+ and Cl− concentrations. Niflumic acid, flufenamic acid, NPPB [5-nitro-2-(3-phenylpropylamino)-benzonate] and DCDPC (3′,5-dichlorodiphenylamine-2-carboxylate), at 0.5 mmol l−1, reversibly blocked both the amino-acid-induced inward currents and the background activity in most ORNs. The effectiveness of these blocking agents varied from 77 to 91 % for ORNs perfused externally with standard Ringer’s solution. SITS (4-acetamido-4′-isothiocyanatostilbene-2,2′-disulphonate), at 5.0 mmol l−1, irreversibly inhibited the physiological response (100 % inhibition), whereas DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulphonate), at 5.0 mmol l−1, had the smallest effect (45 %) of the inhibitors tested. The dose of niflumic acid inducing 50 % inhibition (IC50), determined specifically for the current component of the Ca2+-activated Cl− channels, was 70 µmol l−1. Our results suggest that these blockers are not specific for Ca2+-activated Cl− channels and that the density of these channels varies between individual ORNs. Our results also show that the Ca2+-activated Cl− conductance plays an important role in olfactory transduction and allows fishes to adapt to various ionic environments.
Osteopontin Expression in Spontaneously Developed Neointima in Fowl (Gallus Gallus)
Authors: Kuykindoll Rhonda J. , Nishimura Hiroko , Thomason Donald B. , Nishimoto Satoru K.
Published: April 2021

Fowl show spontaneous elevation of blood pressure and neointimal plaque formation in the abdominal aorta at young ages. A similar neointima can be induced by a balloon-catheter-induced endothelium injury to the fowl aorta. Both spontaneously developed and injury-induced vascular lesions exhibit subendothelial hyperplasia consisting of neointimal cells with a synthetic phenotype and abundant extracellular matrix. The role of the extracellular matrix in the formation of neointima is not known. In this study, we investigated whether osteopontin, an adhesive glycoprotein present in the extracellular matrix, is expressed in aortic smooth muscle tissue of the fowl abdominal aorta, in spontaneously developed neointimal plaques and in the aortic smooth muscle underlying neointimal plaques. Crude protein extracted from isolated aortic smooth muscle tissues and neointimal plaques was fractionated by SDS–polyacrylamide gel electrophoresis and analyzed by immunoblotting with rabbit anti-fowl osteopontin (provided by Dr L. C. Gerstenfeld, Boston University) or anti-alpha smooth muscle actin antibodies. The anti-fowl osteopontin antibody predominantly recognized a 66–70 kDa protein band in neointimal plaques that co-migrated with the osteopontin phosphoprotein from chick bone. In contrast, intact aortic smooth muscle and the smooth muscle underlying neointimal plaques equally expressed three proteins (66–70 kDa, approximately 50 kDa and approximately 43 kDa) recognized by the anti-osteopontin antibody. Anti-alpha smooth muscle actin antibody recognized a 43 kDa protein band, and the expression of alpha smooth muscle actin was higher in aortic smooth muscle than in neointimal plaques. Osteopontin mRNA expression was examined using reverse transcription– polymerase chain reaction (RT–PCR) of total RNA from vascular tissues with specific primers constructed on the basis of the reported fowl osteopontin nucleotide sequence. The PCR products from intact aortic smooth muscle and neointimal plaques correspond to the product from recombinant plasmid cDNA (a gift from Dr L. C. Gerstenfeld) transcribed in vitro. These results suggest that osteopontin is synthesized in intact aortic smooth muscle and neointimal plaques in fowl and that unmetabolized approximately 66 kDa osteopontin protein is a predominant form in the neointima, indicating that osteopontin protein may be actively synthesized in the neointima.
Killer Whales (Orcinus Orca) Feeding On Schooling Herring (Clupea Harengus) Using Underwater Tail-Slaps: Kinematic Analyses of Field Observations
Authors: Domenici Paolo , Batty Robert S. , Similä Tiu , Ogam Erick
Published: April 2021

Killer whales (Orcinus orca) feeding on herring (Clupea harengus) in a fjord in northern Norway were observed using underwater video. The whales cooperatively herded herring into tight schools close to the surface. During herding and feeding, killer whales swam around and under a school of herring, periodically lunging at it and stunning the herring by slapping them with the underside of their flukes while completely submerged. The kinematics of tail-slapping were analysed in detail. Tail-slaps were made up of a biphasic behaviour consisting of two phases with opposite angles of attack, a preparatory phase (negative angles of attack) and a slap phase (positive angles of attack). During the slap phase, the mean maximum angle of attack of the flukes was 47 °. The maximum speed of the flukes, measured at the notch, increased with whale length (Lw) and was 2.2 Lw s−1, while the maximum acceleration of the flukes was size-independent and was 48 m s−2.

When killer whales slapped the herring successfully, disoriented herring appeared on the video at approximately the time of maximum fluke velocity, in synchrony with a loud noise. This noise was not heard when the tail-slaps ‘missed’ the target, suggesting that the herring were stunned by physical contact. Killer whales then ate the stunned herring one by one. Of the tail-slaps observed, 61 % were preceded by lunges into the school. We suggest that lunging was aimed at directing the school rather than at capturing the herring, since it occurred at a relatively low speed and there were no observations of the killer whales attempting to capture the herring during lunging behaviour. Given the high performance of the tail-slaps in terms of speed and acceleration, we suggest that tail-slapping by killer whales is a more efficient strategy of prey capture than whole-body attacks, since acceleration and manoeuvrability are likely to be poor in such large vertebrates.
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

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

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

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

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

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

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

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

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

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

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

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

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 (<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.
Molecular Cloning and Hormonal Control in the Ovary of Connexin 31.5 Mrna and Correlation with the Appearance of Oocyte Maturational Competence in Red Seabream
Authors: Choi Cheol Young , Takashima Fumio
Published: April 2021

Gap junctions are aggregates of intercellular channels, composed of the protein connexin (Cx), between adjacent cells. This study examined whether, in the ovary of the red seabream Pagrus major, the connexin gene essential for the production of RNA and protein during the acquisition of oocyte maturational competence is active. Mixed primers for this reaction were designed on the basis of the high sequence homology of selected regions of known connexin genes. Polymerase-chain-reaction-amplified cDNA fragments generated by 3′ and 5′ rapid amplication of cDNA ends were combined to generate full-length cDNA sequences. The resulting 2400 base pair cDNA had an open reading frame encoding a polypeptide containing 275 amino acid residues (31493 Da; Cx31.5). Hydropathicity analysis of the predicted amino acid sequence indicated that red seabream Cx31.5 has four major hydrophobic regions and four major hydrophilic regions indicative of a topology similar to that of known connexins. Typical connexin consensus sequences were also observed in the first and second extracellular loops. During the acquisition of oocyte maturational competence, red seabream Cx31.5 mRNA transcription levels increased after treatment with gonadotropin-II. It is therefore proposed that expression of Cx31.5 contributes to the acquisition of oocyte maturational competence in this species.
Seasonal Changes in Energy and Water use by Verdins, Auriparus Flaviceps
Authors: Webster Marcus D. , Weathers Wesley W.
Published: April 2021

We used the doubly labeled water (DLW) method to measure field metabolic rate (FMR) and water turnover during winter and summer in a very small (6.5 g) insectivorous desert passerine bird, the verdin (Auriparus flaviceps). Concurrently, we monitored weather conditions and used time–activity budget data of free-living birds and laboratory data on resting metabolic rate to construct time–activity laboratory (TAL) estimates of daily energy expenditure (DEE) and to partition the verdins’ energy budget into thermoregulatory, activity and basal components. The FMR of adult verdins was 33.6±0.9 kJ day−1 (mean ± S.E.M.; N=14) in winter and 22.8±0.45 kJ day−1 (N=7) in summer. FMR correlated negatively with the mean standard operative environmental temperature (Tes) prevailing during the measurement period. TAL analysis produced DEE estimates that corresponded on average to within −0.9±2.4 % of our DLW-measured FMR values (range of individual values −18.3 % to +14.3 %). Metabolic expeditures for cold defense were 19.5±2.1 % of DEE in winter (computed assuming substitution of exercise thermogenesis for thermoregulatory costs in active birds). In the summer, thermoregulatory costs amounted to 9.0±0.4 % of DEE for keeping warm and 1.0±0.1 % of DEE for keeping cool in the heat. Activity costs were 21.0±0.5 % of DEE in winter and 17.5±0.1 % of DEE in summer. The water efflux of nonbreeding adult verdins was 3.9±0.2 ml day−1 (624±22 ml kg−1 day−1) in summer (N=5) and 3.4±0.2 ml day−1 (498±26 ml kg−1 day−1) in winter (N=14). The water economy index (WEI; water efflux per unit FMR) of verdins was higher in summer (0.17±0.01 ml kJ−1) than in winter (0.10±0.01 ml kJ−1) and correlated negatively with mean Tes.
Bioconvective Dynamics: Dependence on Organism Behaviour
Authors: Czirók András , Jánosi Imre M. , Kessler John O.
Published: April 2021

Bioconvection occurs when a macroscopic nonuniformity of the concentration of microbial populations is generated and maintained by the directional swimming of the organisms. This study investigated the properties of the patterns near the onset of the instability and later during its evolution into a fully nonlinear convection regime. In suspensions of the bacteria Bacillus subtilis, which tend to swim upwards in a gradient of oxygen concentration that they create by consumption, we discovered that the dominant wavelength at the onset of the instability is determined primarily by the cell density and is influenced only weakly by the fluid depth. This observation contrasts strongly with previous observations on the gravitactic alga Chlamydomonas nivalis, in which the opposite dependence was found. Considerable differences were also found in the long-term evolution of the convection patterns. These results demonstrate the existence of readily distinguishable types of bioconvection systems, even at early stages of the instability. The observed differences are clearly and causally correlated with disparate reasons for upward swimming by these micro-organisms, leading to different geometric distributions of the density of the suspension.
High Environmental Salinity Induces Memory Enhancement and Increases Levels of Brain Angiotensin-Like Peptides in the Crab Chasmagnathus Granulatus
Authors: Delorenzi Alejandro , Dimant Beatriz , Frenkel Lia , Nahmod Victor E. , Nässel Dick R. , Maldonado Héctor
Published: April 2021

Previous work on the brackish-water crab Chasmagnathus granulatus demonstrated that an endogenous peptide similar to angiotensin II plays a significant role in enhancing long-term memory that involves an association between context and an iterative danger stimulus (context-signal memory). The present results show that this memory enhancement could be produced by moving crabs from brackish water to sea water (33.0 ‰) and keeping them there for at least 4 days. The possibility that such a facilitatory effect is due to osmotic stress is ruled out. Coincidentally, the level of angiotensin-II-like peptides in crab brain, measured by radioimmunoassay, increases with the length of exposure to sea water, reaching a significantly different level at the fourth day. The presence of angiotensin-II-like immunoreactive material in neural structures of the supraoesophageal and eyestalk ganglia was confirmed by immunohistochemical analysis. The results are interpreted as supporting the hypothesis that exposure to water of high salinity is an external cue triggering a process mediated by angiotensins that leads to enhanced memory in these crabs.
Morphometric Partitioning of Respiratory Surfaces in Amphioxus (Branchiostoma Lanceolatum Pallas)
Authors: Schmitz Anke , Gemmel Maj , Perry Steven F.
Published: April 2021

The anatomical diffusing factors (ADFs), defined as the ratio of surface area to the thickness of the diffusion barrier, of possible respiratory surfaces of adult amphioxus (Branchiostoma lanceolatum) were evaluated using stereological methods. The ADF is greatest for the lining of the atrium and for the skin covering the segmental muscles. Calculation of the diffusing capacities for O2 revealed that the lining of the atrium makes up nearly 83 % of the entire diffusing capacity (8.86×10−3 μl min−1 mg−1 kPa−1 ) while the skin over the segmental muscles (9 %), the skin over the metapleural fold (4 %) and the gill bars (4 %) are of minor importance. The diffusing capacity of surfaces lying over coelomic cavities makes up 76 % of the whole diffusing capacity, which is consistent with the hypothesis that the coelom may function as a circulatory system for respiratory gases. Muscles have approximately 23 % of the entire diffusing capacity, indicating that they may be self-sufficient for O2 uptake. The diffusing capacity of the blood vessels in the gill bars is only 1 % of the total. Thus, the ‘gills’ lack significant function as respiratory organs in amphioxus (lancelets).
Does a Rigid Body Limit Maneuverability?
Authors: Walker Jeffrey A.
Published: April 2021

Whether a rigid body limits maneuverability depends on how maneuverability is defined. By the current definition, the minimum radius of the turn, a rigid-bodied, spotted boxfish Ostracion meleagris approaches maximum maneuverability, i.e. it can spin around with minimum turning radii near zero. The radius of the minimum space required to turn is an alternative measure of maneuverability. By this definition, O. meleagris is not very maneuverable. The observed space required by O. meleagris to turn is slightly greater than its theoretical minimum but much greater than that of highly flexible fish. Agility, the rate of turning, is related to maneuverability. The median- and pectoral-fin-powered turns of O. meleagris are slow relative to the body- and caudal-fin-powered turns of more flexible fish.
The Optomotor Response and Spatial Resolution of the Visual System in Male Xenos Vesparum (Strepsiptera)
Authors: Pix Waltraud , Zanker Johannes M. , Zeil* Jochen
Published: April 2021

The Strepsiptera are an enigmatic group of parasitic insects whose phylogenetic relationships are hotly debated. Male Strepsiptera have very unusual compound eyes, in which each of a small number of ommatidia possesses a retina of at least 60 retinula cells. We analysed the optomotor response of Xenos vesparum males to determine whether spatial resolution in these eyes is limited by the interommatidial angle or by the higher resolution potentially provided by the extended array of retinula cells within each ommatidium. We find that the optomotor response in Strepsiptera has a typical bandpass characteristic in the temporal domain, with a temporal frequency optimum at 1–3 Hz. As a function of spatial wavelength, the optomotor response is zero at grating periods below 12 ° and reaches its maximum strength at grating periods between 60 ° and 70 °. To identify the combination of interommatidial angles and angular sensitivity functions that would generate such a spatial characteristic, we used motion detection theory to model the spatial tuning function of the strepsipteran optomotor response. We found the best correspondence between the measured response profile and theoretical prediction for an irregular array of sampling distances spaced around 9 ° (half the estimated interommatidial angle) and an angular sensitivity function of approximately 50 °, which corresponds to the angular extent of the retina we estimated at the centre of curvature of the lens. Our behavioural data strongly suggest that, at least for the optomotor response, the resolution of the strepsipteran compound eye is limited by the ommatidial sampling array and not by the array of retinula cells within each ommatidium. We discuss the significance of these results in relation to the functional organisation of strepsipteran compound eyes, their evolution and the role of vision in these insects.
The Membrane Permeability Transition in Liver Mitochondria of the Great Green Goby Zosterisessor Ophiocephalus (Pallas)
Authors: Toninello A. , Salvi M. , Colombo L.
Published: April 2021

Liver mitochondria from the great green goby Zosterisessor ophiocephalus (Pallas) normally exhibit bioenergetic variables (membrane potential 165±7 mV; respiratory control ratio 6.6±0.4; ADP/O ratio 1.85±0.8; means ± s.e.m., N=6) and activities of physiological transport systems (phosphate/proton symporter, adenine nucleotide antiporter, Ca2+ electrophoretic uniporter) comparable with those of rat liver mitochondria. When incubated in the presence of Ca2+ and an inducer agent such as phosphate, these mitochondria undergo a complete collapse of membrane potential accompanied by a large-amplitude swelling of the matrix, influx of sucrose from the incubation medium, release of endogenous Mg2+ and K+ (approximately 90 % of the total) and of preaccumulated Ca2+ and oxidation of endogenous pyridine nucleotides. All these phenomena, which are completely eliminated by cyclosporin A and inhibited with different efficacies by Mg2+ and spermine, demonstrate that the induction of the permeability transition in this type of mitochondria has characteristics similar to those described in rat liver mitochondria. In contrast, the requirement for very high Ca2+ concentrations (greater than 100 μmol l−1 ) for the induction of the permeability transition represents a very important difference that distinguishes this phenomenon in fish and mammalian mitochondria.
Open-Sea Migration of Magnetically Disturbed Sea Turtles
Authors: Papi F. , Luschi P. , Åkesson S. , Capogrossi S. , Hays G. C.
Published: April 2021

Green turtles (Chelonia mydas) that shuttle between their Brazilian feeding grounds and nesting beaches at Ascension Island in the middle of the Atlantic Ocean are a paradigmatic case of long-distance oceanic migrants. It has been suggested that they calculate their position and the direction of their target areas by using the inclination and intensity of the earth’s magnetic field. To test this hypothesis, we tracked, by satellite, green turtles during their postnesting migration from Ascension Island to the Brazilian coast more than 2000 km away. Seven turtles were each fitted with six powerful static magnets attached in such a way as to produce variable artificial fields around the turtle that made reliance on a geomagnetic map impossible. The reconstructed courses were very similar to those of eight turtles without magnets that were tracked over the same period and in the previous year, and no differences between magnetically disrupted and untreated turtles were found as regards navigational performance and course straightness. These findings show that magnetic cues are not essential to turtles making the return trip to the Brazilian coast. The navigational mechanisms used by these turtles remain enigmatic.
The Pacemaker Activity Generating the Intrinsic Myogenic Contraction Of the Dorsal Vessel Of Tenebrio Molitor (Coleoptera)
Authors: Markou T. , Theophilidis G.
Published: April 2021

Combined intracellular and extracellular recordings from various parts of the isolated dorsal vessel of Tenebrio molitor revealed some of the following electrophysiological properties of the heart and the aorta. (i) The wave of depolarization causing forward pulsation of the dorsal vessel was always transmitted from posterior to anterior, with a conduction velocity of 0.014 m s−1 in the heart and 0.001 m s−1 in the aorta when the heart rate was 60 beats min−1. (ii) There was no pacemaker activity in the aorta. (iii) The duration of the compound action potential in the aortic muscle depended on the duration of the pacemaker action potential generated in the heart. (iv) Isolated parts of the heart continued to contract rhythmically for hours, indicating powerful pacemaker activity in individual cardiac segments. (v) There was a direct relationship between action potential duration and the length of the preceding diastolic interval. (vi) The rhythmic wave of depolarization was dependent on the influx of Ca2+. (vii) The recovery of the electrical properties of myocardial cells that had been disrupted by sectioning was rapid. (viii) In hearts sectioned into two halves, the rhythmic pacemaker action potentials recorded simultaneously from the two isolated halves eventually drifted out of phase, but they had the same intrinsic frequency. In the light of these data, we discuss two alternative models for the generation of spontaneous rhythmic pumping movements of the heart and aorta.
Cues by which Portia Fimbriata, An Araneophagic Jumping Spider, Distinguishes Jumping-Spider Prey From Other Prey
Authors: Harland Duane P. , Jackson Robert R.
Published: April 2021

Portia fimbriata from Queensland, Australia, is an araneophagic jumping spider (Salticidae) that includes in its predatory strategy a tactic (cryptic stalking) enabling it to prey effectively on a wide range of salticids from other genera. Optical cues used by P. fimbriata to identify the salticid species on which it most commonly preys, Jacksonoides queenslandicus, were investigated experimentally in the laboratory using odourless lures made from dead prey on which various combinations of features were altered. P. fimbriata adopted cryptic stalking only against intact salticid lures and modified lures on which the large anterior-median eyes were visible. Ordinary stalking was usually adopted when the lure did not have the anterior-median eyes visible. There was no evidence that cues from the legs of prey salticids influence the choice of stalking style of P. fimbriata, but cues from the legs do appear to influence strongly whether a prey is stalked at all. Cues from the cephalothorax and abdomen also influenced the stalking tendency, but to a lesser degree than cues from the legs. An algorithm to describe the perceptual processes of P. fimbriata when visually discriminating between salticid and non-salticid prey is discussed.