bluuebunny/crossref_metadata_2025 huggingface dataset:
Exhaustive Exercise in the Sea Lamprey (Petromyzon Marinus): Relationship Between Anaerobic Metabolism and Intracellular Acid–Base Balance
Authors: Boutilier R. G. , Ferguson R. A. , Henry R. P. , Tufts B. L.
Published: April 2021

We measured intracellular acid–base balance and indicators of carbohydrate and high-energy phosphate metabolism as lampreys recovered from exhaustive exercise.

A combined respiratory and metabolic acidosis was observed in the locomotory muscle following ‘burst’ exercise. Muscle pH decreased from approximately 7.2 to 6.7, whereas intracellular rose from approximately 0.6 to 1.6kPa. Unlike the situation in similarly stressed teleost fish such as rainbow trout, the respiratory acidosis in muscle persisted for several hours. This apparent CO2 retention in lamprey muscle may be the result of a restricted ability of the circulatory system to transport CO2 due to reduced erythrocyte anion exchange, or it could represent a restricted ability of the muscle itself to clear the intracellular pool of CO2 due to reduced carbonic anhydrase activity.

Maximal lactate dehydrogenase activity of lamprey muscle exhibited a marked dependence on pH, increasing in activity by 30% as pH decreased from 7.2 to 6.7 (reflecting the ‘resting’ to ‘post-exercise’ pH change observed invivo).

Following exhaustive exercise, the acid–base balance of the muscle is influenced by both proton-consuming (e.g. AMP deamination, glycogen replenishment) and proton-producing (e.g. rephosphorylation of creatine) metabolic processes. The net effect is that, although intracellular pH is maximally depressed, energy stores such as phosphocreatine and glycogen are partially restored within 1h of exhaustive exercise, placing the animal in good stead for further locomotory work.
The Effect Of Solid And Porous Channel Walls On Steady Swimming Of Steelhead Trout Oncorhynchus Mykiss
Authors: Webb Paul W.
Published: April 2021

Kinematics and steady swimming performance were recorded for steelhead trout (approximately 12.2cm in total length) swimming in channels 4.5, 3 and 1.6cm wide in the centre of a flume 15cm wide. Channel walls were solid or porous. Tail-beat depth and the length of the propulsive wave were not affected by spacing of either solid or porous walls. The product of tail-beat frequency, F, and amplitude, H, was related to swimming speed, u, and to harmonic mean distance of the tail from the wall, z. For solid walls:

and for grid walls:

where ±2 S.E. are shown for regression coefficients. Thus, rates of working were smaller for fish swimming between solid walls, but the reduction due to wall effects decreased with increasing swimming speed. Porous grid walls had less effect on kinematics, except at low swimming speeds. Spacing of solid walls did not affect maximum tail-beat frequency, but maximum tail-beat amplitude decreased with smaller wall widths. Maximum tail-beat amplitude similarly decreased with spacing between grid walls, but maximum tail-beat frequency increased. Walls also reduced maximum swimming speed. Wall effects have not been adequately taken into account in most studies of fish swimming in flumes and fish wheels.
The Body Temperature of the Frog
Authors: Mellanby Kenneth
Published: April 2021

Under most conditions the amount of metabolic heat produced by a frog is so small that the animal behaves like a non-living system and its temperature is controlled by external physical conditions.

The frog’s skin is so permeable that when the animal is exposed to moderately rapidly moving air (1 m. per sec. or over) evaporation reduces its internal temperature to the wet-bulb temperature.

About 25 % of the frog’s weight may be lost by evaporation before death ensues. After death water continues to evaporate at the same rapid rate until 50 % of the animal’s weight is lost.
On Oviposition, Olfactory Conditioning and Host Selection in Rhizopertha Dominica Fab. (Insecta, Coleoptera)
Authors: Crombie A. C.
Published: April 2021

The senses used in food finding and the factors inducing oviposition in Rhizo-pertha dominica (Fab.), a Bostrichid beetle pest of stored grain, were investigated. The sense of smell appears to be the most important in leading the animal to an environment where food is present. Responses were obtained in an olfactometer with maize, wheat, oats and barley and with different extracts of wheat and maize. The use of the sense of sight was also investigated.

Once within an environment having the odour of food the sense of touch appears to be paramount in the selection of oviposition site. The influence of size, shape and texture were investigated. But in the absence of appropriate patterns of stimuli involving both olfactory and tactile sensations, restraint from ovippsition was exercised.

No predilection was shown for oviposition or feeding in the food in which they were reared as larvae. Neither did the larvae especially choose for entry substances in which their parents have been reared.

The animal can be made tolerant to the odour of peppermint instead of repelled by it in an olfactometer by exposing the adults to the odour of peppermint for a few weeks. The effect wears off after 10-14 days’ isolation from peppermint in wheat.

Olfactory receptors which appear to be located on the antennae and legs were used in both food-finding and recognition of the opposite sex.

A list is given of the substances in which the animal was reared.

The bearing of these results on the problem of “gestalt” in conditioning, and on changes in habit in economic insects, is discussed.
Osmotic Behaviour of the Fairy Shrimp Chirocephalus Diaphanus Prévost
Authors: Panikkar N. Kesava
Published: April 2021

Nothing is known of the osmotic concentration of the blood of fresh-water phyllopods. In the cladoceran Daphnia magna, Fritzsche (1917) obtained freezing-point depressions for blood varying between—0·2 and—0·67° C. Krogh (1939) did some preliminary experiments on Branchipus (.? grubii) and Apus (Lepidurus) productus and found that these animals can be kept alive without food only for a day or two, whether they are in tap water, distilled water or in Ringer/100. Regular loss of chloride occurred in all experiments, which indicated the absence of active regulation and the necessity of food to make good the constant loss of salts. Artemia, which is closely related to Branchipus, inhabits concentrated salines up to about 35 % salt and shows highly developed powers of regulation involving ability to maintain hypotonicity to the external medium. By Barger’s method, Medwedewa (1927) and Kuenen (1939) found that the osmotic pressure of its blood varied only between 1 · 2 and 2 · 6% NaCl for a change in the external medium from 4 · 7 to 17 · 7% NaCl. Chirocephalus, which belongs to the same tribe of phyllopods as Artemia and Branchipus, is an essentially fresh-water form, though by frequent drying and flooding the pools in which it lives may accumulate slight quantities of salt. Weldon (1909) found them alive in an aquarium where, by evaporation, the chloride content of water had risen up to 0 · 019% NaCl. The following experiments were performed in order to study the osmotic properties of Chirocephalus when a limited supply was available in the summer of 1940.
The Biology and Behaviour of Ptinus Tectus Boie. (Coleoptera, Ptinidae), a Pest of Stored Products
Authors: Bentley E. W. , Gunn D. L. , Ewer D. W.
Published: April 2021

In alternating light and darkness at 25 ° C., Ptinus tectus shows a diurnal rhythm of locomotory activity with maximum activity occurring in the dark period. The rhythm is continued for a few days in continuous light.

In continuous light, no inherent 24 hr. rhythm is apparent, but in subsequent alternating light and darkness, within 1 day, activity becomes practically confined to the dark period.

The rhythm can be reversed by reversing the hours of light and darkness and the reversed rhythm is similarly continued in continuous light.

In conditions of alternating light and darkness with fluctuating temperature (10–20 ° C. with low temperature in thé dark periods) Ptinus shows greater activity than at 25 ° C., and maximum activity occurs in the cold, dark period.

In constant light and daily fluctuating temperature (17–23 ° C.), the period of greatest activity occurs when the temperature is falling. After transfer to constant temperature, this period still occurs at the same time of day for a few days.
A Comparative Study of Peripheral Inhibition in Decapod Crustaceans
Authors: Wiersma C. A. G. , Ellis C. H.
Published: April 2021

The effectiveness with which different contractions in a number of muscles can be inhibited was investigated. As a measure of this effectiveness the frequency of inhibition which can just inhibit a contraction with a given frequency of excitation was determined. It was found that in all systems the ratio (Rc) of such inhibitory frequencies to that of the excitatory frequencies they can suppress was constant for a wide range of frequencies.

At high frequencies either the inhibition or the excitation may become less effective. This is explained by failure of the respective system to function normally at such a frequency.

The effectiveness of inhibition of different systems was determined. Some systems show a very constant Rc value; in a second group Rc varies within wider limits; and a third group shows two distinct Re’s sometimes in the same preparation at different times.

Rc values have been found to vary widely. For instance, in the bender inhibitor-slow bender system of Pachygrapsus three excitatory impulses are suppressed by one inhibitory impulse; in the closer inhibitor-slow closer system of Cambarus one excitatory impulse needs five inhibitory impulses to counteract its effect. The fast closer contraction of Cambarus and the fast closer and fast bender contraction of Pachygrapsus were found to be uninhibitable, i.e. no effect of inhibition what-soever was noticed on any of these contractions. All three systems are distinguished by giving a mechanical response to a single stimulus in contrast with all the inhibitable systems which do not respond to single impulses.

Reduction of the action potentials during inhibition is obtainable in only a few systems, namely, the opener inhibitor-opener and the stretcher inhibitor-stretcher systems of Cambarus and the crabs. (In the crabs this applies only to the ‘true1 inhibitors.) In all other systems, including every system of Panultrus, no reduction of the muscle action potential is obtained.
Carbohydrate Metabolism of Chick Fibroblasts in Vitro
Authors: Willmer E. N.
Published: April 2021

The glucose consumption of osteoblasts growing in a medium of plasma and embryo juice has been compared with that of the same cells in plasma and Tyrode medium. Embryo juice causes an initial increased glucose consumption which later falls below the level characteristic of a Tyrode-plasma medium. A modification of a method of measuring the nucleoprotein phosphorus content of tissue cultures is described and among other data obtained the changes which occur in this figure have been noted for fourth passage chick osteoblast cultures and for fresh heart explants during the first 4 days of culture in media of plasma and Tyrode and of plasma and embryo juice. The figures for nucleoprotein content have been correlated with those for glucose consumption and lactic acid production and pronounced differences have been observed in the behaviour of the two types of tissue. The possible significance of the findings is discussed. There is no absolute correlation between high growth rate and high sugar consumption or lactic acid production. The data discussed are consistent with the idea that an increased protein metabolism, and a decreased carbohydrate metabolism result from the addition of embryo juice to osteoblast cultures. Embryo juice has no detectable effects on the carbohydrate metabolism of fresh heart cultures.
Leading Edge Section and Asymmetric Twisting in the Wings of Flying Butterflies (Insecta, Papilionoidea)
Authors: Wootton Robin J.
Published: April 2021

Insect wings are mounted on hinges, restricting the extent to which their bases can be supinated for the upstroke. The forewings of many insects therefore include devices that allow the distal part of the wing to twist relative to the base under aerodynamic loading in the upstroke, but restrict such twisting in the downstroke where the effect would be detrimental. In the broad forewings of butterflies, this asymmetric resistance to aerodynamic twisting seems to be a consequence of the curved section of the leading edge. The wing can be modelled as a cantilevered, thin cambered plate. Torsional tests on the forewings of four butterfly species and on a paper wing of curved section confirm the effect. Differences between the results for the four species appear to fit their morphological and kinematic differences. The nature of the mechanism is outlined.
H+ -ATPase Activity in Crude Homogenates of Fish Gill Tissue: Inhibitor Sensitivity and Environmental and Hormonal Regulation
Authors: Lin Hong , Randall David J.
Published: April 2021

N-ethymaleimide-sensitive ATPase activity was measured in crude homogenates of gill tissue from rainbow trout using a coupled-enzyme ATPase assay in the presence of EGTA, ouabain and azide. This NEM-sensitive ATPase activity, determined to be about 1.5 μmolmg−1 protein h−1 at 15°C for freshwater trout, is also inhibited by other H+-ATPase blockers such as DCCD, DES, PCMBS and bafilomycin. It is concluded, therefore, that the NEM-sensitive ATPase activity was generated by a proton-translocating ATPase. Since this NEM-sensitive ATPase was also sensitive to the plasma membrane ATPase inhibitor vanadate, we conclude that the H+-ATPase in fish gill is of the plasma membrane type. The major role of the H+-ATPase in the gill epithelium is to facilitate Na+ uptake from fresh water. Sodium concentration in the external medium was the primary regulator of the H+-ATPase in fish gills, with low sodium levels being associated with high H+-ATPase activity. High external calcium concentration had a marked stimulatory effect on H+-ATPase activity in fish gills when the sodium level was low. Environmental hypercapnia induced a 70% increase in the H+-ATPase activity in fish gills. H+-ATPase activity was also elevated in freshwater fish after chronic cortisol infusion.
Lactate Metabolism In Rainbow Trout
Authors: Milligan C. Louise , Girard Stéphane S.
Published: April 2021

We have investigated the metabolic fate of blood lactate in resting rainbow trout and in fish recovering from a bout of exhaustive exercise. At rest and during recovery from exercise, the majority of blood lactate was oxidized, the proportion increasing with increasing oxygen consumption. It is estimated that, during recovery from exhaustive exercise, lactate released from the muscle has the potential to fuel a significant portion of oxidative metabolism. The bulk of the remaining blood lactate reappeared in the muscle lactate pool, probably via direct uptake by the muscle. There was a significant incorporation of blood lactate into the muscle glycogen pool, providing strong evidence for in situ glycogenesis as the mode for muscle glycogen replenishment. To investigate the role of the liver in blood lactate clearance, trout were functionally hepatectomized by ligation of the hepatic portal circulation. The exercise performance of hepatectomized fish was equal to that of sham-operated fish and controls, indicating that muscle relies primarily on endogenous fuel stores. Furthermore, blood lactate levels immediately after exercise were greater and muscle metabolic recovery was faster in hepatectomized fish than in sham-operated fish and controls. These observations suggest that glycogen resynthesis in trout muscle may be retarded because of a non-recoverable loss of substrate (i.e. lactate) from the muscle, because the lactate released is utilized by the liver. These results are discussed in view of what is known about these processes in other ectothermic vertebrates.
The Renin–Angiotensin System in Blood Pressure Control During Exercise in the Cod Gadus Morhua
Authors: Platzack Björn , Axelsson Michael , Nilsson Stefan
Published: April 2021

The effects of angiotensin I, angiotensin II and exercise on ventral and dorsal aortic blood pressure and heart rate were investigated in the Atlantic cod, Gadus morhua. Both angiotensins produced a marked increase in blood pressure. After injection of the angiotensin-converting enzyme (ACE) inhibitor enalapril, both ventral and dorsal blood pressures decreased significantly and the effect of angiotensin I was abolished. This demonstrates that ACE activity is necessay for conversion of angiotensin I to angiotensin II in the cod, as in other teleosts investigated, and provides a tool for further study of angiotensin function.

During swimming exercise at 2/3 body lengths per second, ventral and dorsal aortic blood pressures increased, but this exercise hypertension was absent in fish pretreated with the α-adrenoceptor antagonist prazosin. Instead, an increase in both ventral and dorsal aortic blood pressures occurred immediately after the exercise period. This post-exercise hypertension could be abolished by injection of enalapril, suggesting that the angiotensin system is the responsible ‘anti-drop’ factor activated in the absence of a functional adrenergic vasomotor control.

We conclude that the angiotensin system provides a major contribution to the resting blood pressure regulation in the cod, and that this system can be activated to offset a decrease in arterial blood pressure.
Stress-Induced Failure of Osmoregulation in the Parasitic Nematode Pseudoterranova Decipiens: Indirect Evidence for Hormonal Regulation
Authors: Davey K. G. , Sommerville R. I. , Fusé M.
Published: April 2021

When third-stage larvae of Pseudoterranova decipiens maintained at 5°C are placed in either 40% artificial sea water (ASW, iso-osmotic) or 15% ASW (hypo-osmotic) and weighed once at 0h and again at 24h, they neither lose nor gain weight, and the osmotic pressure (OP) of their pseudocoelomic fluid (PCF) remains unchanged. In contrast, when worms are weighed six additional times during the 24h interval, those maintained in iso-osmotic conditions lose weight, while those maintained in hypo-osmotic conditions gain weight. Worms which had been exposed to hypo-osmotic conditions and weighed at various times between 0 and 24h exhibited an increase in weight which was correlated with the number of weighings. Worms exposed to hypo-osmotic conditions and weighed three additional times between 0 and 24h also gained weight, and the OP of the PCF decreased such that worms experiencing the greatest increase in weight suffered the greatest dilution of the PCF. In worms ligatured at the head or tail or at the head and tail, and then exposed to either 15% or 40% ASW, the effect of multiple weighings is exaggerated in a complex way. The presence of a ligature on the tail in worms immersed in an iso-osmotic medium leads to an increase in weight and to a very marked additional increase in weight in worms immersed in a hypo-osmotic medium. The presence of a head ligature in worms in an iso-osmotic medium leads to a decrease in weight and to a smaller weight gain in a hypo-osmotic medium. The addition of a head ligature to worms ligatured at the tail increases the weight gain in both iso-osmotic and hypo-osmotic media. These results demonstrate that stress induced by handling disrupts the normal capacity to osmoregulate in P. decipiens; they are consistent with the stress-induced release of postulated diuretic and antidiuretic factors.
Rapid Respiratory Changes in Trout Red Blood Cells During Na+/H+ Exchange Activation
Authors: Perry S. F. , Thomas S.
Published: April 2021

Respiratory variables of rainbow trout (Oncorhynchus mykiss) blood were monitored continuously in vivo using an extracorporeal circulation or in vitro using blood flowing in a semi-closed loop. The experiments were designed to assess the rapid effects of endogenous catecholamines on red blood cell (RBC) O2 and CO2 transport. The addition of catecholamines (nominal final blood concentrations were 250nmol l−1 adrenaline and 20nmol l−1 noradrenaline) caused activation of RBC Na+/H+ exchange both in vivo and in vitro as indicated by the reductions in whole-blood pH.

In both experimental systems, the activation of Na+/H+ exchange was associated with a rapid reduction of blood , indicating a sudden net movement of plasma CO2 into the RBC. In vitro the initial reduction of blood was followed by a pronounced elevation as a result of the titration of plasma HCO3− by H+ extruded from the RBC. Blood fell markedly in a transitory manner after the addition of catecholamines. The decreases in were probably caused by rapid increases in the affinity/capacity of haemoglobin for O2 which, in turn, caused O2 molecules to enter the RBC from the plasma. The results are discussed with reference to the role of circulating catecholamines in rapidly modifying blood O2 and CO2 transport in rainbow trout.
Ammonia, Na+, K+ and Cl− Levels in Rainbow Trout Yolk-Sac Fry in Response to External Ammonia
Authors: Paley R. K. , Twitchen I. D. , Eddy F. B.
Published: April 2021

Body ammonia content of rainbow trout alevins was about 0.6μmol g−1 but increased to 4 μmol g−1 after 24h of exposure to an external ammonia concentration of 36.2 μmol l−1 NH3 (15.8mmol l−1 ammonia) at pH7 and 10°C. During ammonia loading, the mass of alevins remained unchanged, but body ion concentrations decreased by about 28% for Na+ and Cl− and by 35% for K+. These effects were reduced at lower ammonia concentrations. Exposure for 24h to 36.2 μmol l−1 NH3 (15.8mmol l−1 ammonia) at pH7 and 10°C resulted in a build up of body ammonia that was almost complete within 10h, whereas Na+ loss from the body was delayed and commenced after about 5h of exposure. After exposure, ammonia unloading from the body was complete in about 10h but there was a delay of about 5h before Na+ uptake commenced. During ammonia exposure, alevins lost substantial amounts of K+ (14 μmol g−1) that were not replaced for several days after exposure to ammonia. Ammonia exposure has major effects on ionic regulation in juvenile fish and possible regulatory processes are discussed.
An Evaluation of Factors Limiting Carbon Dioxide Excretion by Trout Red Blood Cells in Vitro
Authors: Perry Steve F. , Gilmour Kathleen
Published: April 2021

An evaluation of several potential factors limiting carbon dioxide excretion by rainbow trout (Oncorhynchus mykiss) red blood cells was performed in vitro using a recently developed radioisotopic assay. Red blood cell (RBC) CO2 excretion was reduced by pre-treatment (30min) of blood with the carbonic anhydrase inhibitor acetazolamide (final nominal concentration 10−4 mol l−1) or the Cl−/HCO3− exchange inhibitor SITS (4-acetamido-4′-isothiocyanatostilbene-2,2′-disulphonic acid; 10−4 mol l−1). The addition of bovine carbonic anhydrase to plasma stimulated CO2 excretion in a dose-dependent manner, with maximal levels of CO2 excretion achieved at a concentration of 3mgml−1. These results confirmed that carbonic anhydrase activity and/or Cl−/HCO3− exchange velocity are potential limiting factors in CO2 excretion.

Increasing the haematocrit elevated the rate of RBC CO2 excretion, although the effect was apparent only between 0 and 15% haematocrit; the rate of CO2 excretion was unaffected by further increases in haematocrit between 15 and 35%. Acute elevation of plasma HCO3− levels increased the rate of CO2 excretion in blood but not in plasma (with or without added carbonic anhydrase). These data suggest that HCO3− availability may limit CO2 excretion at higher haematocrits when the Cl−/HCO3− exchange sites are most plentiful.

Lysis of RBCs and the accompanying release of intracellular carbonic anhydrase into the plasma significantly increased CO2 excretion at all haematocrit and HCO3− levels, indicating that the velocity of Cl−/HCO3− exchange does indeed limit trout RBC CO2 excretion. The addition of carbonic anhydrase (3mgml−1) to lysed blood caused a further increase in the rate of CO2 excretion but only at the low haematocrit of 5%. This result suggests that the activity of RBC carbonic anhydrase does not normally limit CO2 excretion except at unusually low haematocrits, such as might occur during severe anaemia.

The rapid oxygenation of partially deoxygenated blood during the 3min assay caused a marked stimulation of CO2 excretion that was concurrent with a significant decrease of RBC intracellular pH (pHi). These data indicate that the supply of Bohr protons during the oxygenation of the blood is a key factor limiting CO2 excretion. Oxygenation of the blood prior to performing the assay also lowered RBC pHi, although CO 2 excretion was actually reduced, indicating a possible specific effect of pHi on Cl−/HCO3− exchange activity or HCO3− dehydration. The results are discussed with reference to the control of carbon dioxide excretion in fish.
The Sensing of Electrical Capacitances by Weakly Electric Mormyrid Fish: Effects of Water Conductivity
Authors: Emde Gerhard Von Der
Published: April 2021

Weakly electric fish can perceive electric properties of objects by monitoring the responses of their epidermal electroreceptors (mormyromasts) to their own electric organ discharges (EOD), a process known as active electrolocation. Mormyrid fish can distinguish capacitative from resistive properties of objects. It is mainly animate objects that possess capacitative properties. Water conductivity is a critical environmental factor that varies widely from season to season and has strong effects on the emitted EOD.

The two goals of this study were: (1) to investigate the ability of Gnathonemus petersii to detect the properties of capacitative objects in waters of different ion content and (2) to test a recently formulated hypothesis which states that the detection of the features of a capacitative object depends on a comparison of the inputs from the two types of mormyromast primary afferents. Individuals of G. petersii were tested in a conditioned electrolocation procedure.

With increasing water conductivities from 50 to 1100 μS cm−1, EOD amplitude decreased and the detection threshold for small capacitances increased. At 50 μS cm−1, the smallest detectable capacitative value was below 0.5nF; this increased to about 20nF at 800 μS cm−1. When conductivity approached about 1000 μS cm−1, fish were no longer able to electrolocate, probably because of the reduction in EOD amplitude at high conductivities.

The fish’s ability to discriminate a capacitative object unequivocally from every resistive object was also tested at different conductivities. Below about 800 μS cm−1, all fish could do so. Above that conductivity, however, fish could no longer discriminate between capacitative and resistive objects of similar impedance, although they could still discriminate between objects of different impedances. The two types of receptor afferents (from the ‘A’ and ‘B’ cells) of mormyromast electroreceptor organs have different thresholds, with the B afferents being more sensitive. I suggest that only the B receptor cells remain active at about 800 μS cm-1, when the EOD amplitude is much reduced. With input from B afferents only, an unambiguous capacitance detection was no longer possible. This supports the hypothesis that capacitance detection is achieved by comparing inputs of A and B electroreceptor cells.
Glucose Concentration Regulates Freeze Tolerance In the Wood Frog Rana Sylvatica
Authors: Costanzo Jon P. , Lee Richard E. , Lortz Peter H.
Published: April 2021

In spring, the lowest temperature during freezing that can be survived by wood frogs (Rana sylvatica) from southern Ohio is approximately −3°C. We investigated whether the thermal limit of freeze tolerance in these frogs is regulated by tissue levels of glucose, a putative cryoprotectant that is distributed to tissues during freezing. Frogs receiving exogenous glucose injections prior to freezing showed dose-dependent increases in glucose within the heart, liver, skeletal muscle and blood. Tissue glucose concentrations were further elevated during freezing by the production of endogenous glucose. Most glucose-loaded frogs survived freezing to −5°C, whereas all control (saline-injected) frogs succumbed. Further, we investigated some mechanisms by which glucose might function as a cryoprotectant in R. sylvatica. Organ dehydration, a normal, beneficial response that reduces freezing injury to tissues, occurred independently of tissue glucose concentrations. However, elevated glucose levels reduced both body ice content and in vivo erythrocyte injury. These results not only provided conclusive evidence for glucose’s cryoprotective role in R. sylvatica, but also revealed that tissue glucose level is a critical determinant of freeze tolerance capacity in this species.
Kinematics of Birdsong: Functional Correlation of Cranial Movements and Acoustic Features in Sparrows
Authors: Westneat Mark W. , Long John H. , Hoese William , Nowicki Stephen
Published: April 2021

The movements of the head and beak of songbirds may play a functional role in vocal production by influencing the acoustic properties of songs. We investigated this possibility by synchronously measuring the acoustic frequency and amplitude and the kinematics (beak gape and head angle) of singing behavior in the white-throated sparrow (Zonotrichia albicollis) and the swamp sparrow (Melospiza georgiana). These birds are closely related emberizine sparrows, but their songs differ radically in frequency and amplitude structure. We found that the acoustic frequencies of notes in a song have a consistent, positive correlation with beak gape in both species. Beak gape increased significantly with increasing frequency during the first two notes in Z. albicollis song, with a mean frequency for note 1 of 3kHz corresponding to a gape of 0.4cm (a 15° gape angle) and a mean frequency for note 2 of 4kHz corresponding to a gape of 0.7cm (a 30° gape angle). The relationship between gape and frequency for the upswept third note in Z. albicollis also was significant. In M. georgiana, low frequencies of 3kHz corresponded to beak gapes of 0.2–0.3 cm (a 10–15° beak angle), whereas frequencies of 7–8kHz were associated with flaring of the beak to over 1cm (a beak angle greater than 50°). Beak gape and song amplitude are poorly correlated in both species. We conclude that cranial kinematics, particularly beak movements, influence the resonance properties of the vocal tract by varying its physical dimensions and thus play an active role in the production of birdsong.
Compartmentation of Liver Phosphoenolpyruvate Carboxykinase in the Aquatic Turtle Pseudemys Scripta Elegans: A Reassessment
Authors: Land Stephen C. , Hochachka Peter W.
Published: April 2021

Phosphoenolpyruvate carboxykinase (PEPCK) catalyses the conversion of oxaloacetate to pyruvate in the first step of gluconeogenesis. Since oxaloacetate is impermeable to the inner mitochondrial membrane, the localisation of PEPCK within the cell plays a major role in defining substrate preferences for gluconeogenesis. As a result, the immunochemically distinct isoenzymes of PEPCK found within the mitochondrial and the cytosolic cell fractions vary in their proportion to one another between organs and species and with prandial state.
The Effect of Exercise on the Cardiac Output and Blood Flow Distribution of the Largescale Sucker Catostomus Macrocheilus
Authors: Kolok Alan S. , Spooner R. Michael , Farrell Anthony P.
Published: April 2021

Cardiac output (Q̇) and blood flow distribution were measured in adult largescale suckers at rest and while swimming. Cardiac output was directly measured using an ultrasonic flowprobe in fish during the summer (16°C), fall (10°C) and winter (5°C).

Largescale suckers were adept at holding station against a current without swimming and, when engaged in this behavior, they did not signific.antly increase Q̇ relative to that found in fish in still water. When fish began to swim, Q̇ increased significantly. From 16 to 10°C, the critical swimming speed (Ucrit), maximum Q̇ and scope for Q̇ of the suckers did not change. However, from 10 to 5°C all three traits were significantly reduced. Thus, these fish respond to variation in water temperature in two different ways. From 16 to 10°C, the fish compensate perfectly for the change in temperature with respect to cardiac and swimming performance. From 10 to 5°C, however, largescale suckers experience a dramatic decline in cardiac and swimming performance that may be associated with a quiescent overwintering strategy.

Blood flow distribution in the fish at rest and while swimming was measured at 16°C using injection of colored microspheres. In the resting fish, over 10% of the microspheres were recovered from the kidney and over 43% were recovered from white muscle. When the fish were swimming, there was a 60-fold increase in blood flow to the red muscle while blood flow to all other tissues remained consistent with that at rest.
Muscle Temperature and Swim Velocity Profiles During Diving in a Weddell Seal, Leptonychotes Weddellii
Authors: Ponganis P. J. , Kooyman G. L. , Castellini M. A. , Ponganis E. P. , Ponganis K. V.
Published: April 2021

Locomotory muscle temperature and swim velocity profiles of an adult Weddell seal were recorded over a 21h period. The highest temperatures occurred during a prolonged surface period (mean 37.3°C, S.D. 0.16°C). Muscle temperature averaged 36.8 and 36.6°C (S.D. 0.25°C, 0.19°C) during two dive bouts and showed no consistent fluctuations between dive and interdive surface intervals. Swim velocities were also constant, near 1.3 ms−1. These data indicate that past records of low aortic temperatures (35°C) during and after prolonged dives are not indicative of whole-body temperature changes, and that muscle temperature, even during dives as long as 45min, remains near 37°C.
Power Output of Glycerinated Bumblebee Flight Muscle
Authors: Gilmour K. M. , Ellington C. P.
Published: April 2021

The properties of asynchronous insect flight muscle have been examined using a glycerol-extracted single-fibre preparation of dorsal longitudinal muscle from the bumblebees Bombus lucorum and B. terrestris. Chemical, mechanical and thermal conditions were controlled with the objective of maximizing power output. The problems arising from diffusion limitation were avoided through a combination of fibre paring and the use of an ATP backup system. Work and power output tended to increase with increasing oscillatory strain in the range 1–5%. Workloop shape, and hence work and power, varied with fibre extension; optimum extensions ranged from 4 to 12%. The mechanical performance of glycerinated bumblebee muscle fibres was strongly temperature-dependent, and rate processes (frequency, power) displayed higher thermal sensitivities than processes associated with tension development (work). The experimental conditions that maximized the power output were identified as: oscillatory strain ϵ=4–5%, extension ϵo=8–10%, oscillation frequency f=50Hz and temperature T=40°C. The maximum power output observed under these ‘optimal’ conditions was about 110 W kg−1 (muscle), demonstrating for the first time that glycerinated fibres are capable of producing the power predicted from free-flight studies to be required for flight: 100 W kg−1.
Screening-Pigment Migration in the Octopus Retina Includes Control by Dopaminergic Efferents
Authors: Gleadall Ian G. , Ohtsu Kohzoh , Gleadall Etsuko , Tsukahara Yasuo
Published: April 2021

The extent of screening-pigment (SP) migration in the intact octopus retina and the amplitude of the early receptor potential (ERP) correspond with the degree of adaptation to light or darkness. The light-adapted retina has SP granules concentrated in an apical layer, at the tips of the photoreceptor rhabdoms and supporting cells, and the ERP is barely detectable. In the fully dark-adapted retina, the SP granules are mostly at the base of the rhabdoms, and the ERP is at its maximum. Retinae at intermediate stages, between the fully dark-and light-adapted states, show corresponding intermediate stages of SP migration and ERP amplitude.

A series of experiments demonstrates the effects on SP migration of the efferent nerves, which form a subset of fibres in the optic nerves. When the optic nerves to one half of the retina have been severed, there is a dramatic difference in the distribution of SP in areas of the retina (of the dark-adapted eye) connected with severed or intact nerves: apical versus basal, respectively. On incubation of a light-adapted retina with 5 μmol l−1 dopamine, but not with other catecholamines or other putative neurotransmitter substances, SP migrates basally and the ERP is significantly larger than for controls. In octopuses treated with reserpine, SP stays in an apical location and the ERP remains very small, regardless of the state of adaptation and of whether the optic nerves are intact. It is concluded that dopaminergic efferents from the optic lobes effect dark-adaptational SP migration in the cephalopod retina. The arrival in the retina of efferent signals that effect adaptational changes through the mediation of dopamine is a remarkable analogue of the vertebrate system.
Power Output and Propulsive Efficiency of Swimming Bottlenose Dolphins (Tursiops Truncatus)
Authors: Fish Frank E.
Published: April 2021

The power output and propulsive efficiency of swimming bottlenose dolphins (Tursiops truncatus) were determined from a hydromechanical model. The propulsive movements were filmed as dolphins swam in large pools. Dolphins swam at velocities of 1.2–6.0 ms−1. Propulsion was provided by dorsoventral oscillations of the posterior body and flukes. The maximum angle of attack of the flukes showed a linear decrease with velocity, whereas the frequency of the propulsive cycle increased linearly with increasing velocity. Amplitude was 20% of body length and remained constant with velocity. Propulsive efficiency was 0.81. The thrust power computed was within physiological limits. After correction for effects due to swimming depth, the coefficient of drag was found to be 3.2 times higher than the theoretical minimum assuming turbulent boundary conditions. The motions of the body and flukes are primarily responsible for the increased drag. This analysis supports other studies that indicate that bottlenose dolphins, although well adapted for efficient high-performance swimming, show no unusual hydrodynamic performance.
Properties of Voltage-Activated Ionic Currents in cells from the Brains of the Triclad Flatworm Bdelloura Candida
Authors: Blair Kevin L. , Anderson Peter A. V.
Published: April 2021

Cells were dispersed from the brains of the triclad flatworm Bdelloura candida and maintained in primary culture for up to 2 weeks. Cultured cells assumed a variety of morphologies consistent with those of neurones in vivo. Whole-cell voltage-clamp recordings from cultured cells revealed that these cells possess a variety of ionic currents, including a fast transient sodium current, a calcium current and several potassium currents. The sodium current does not inactivate completely but instead decays to a steady-state component which has the same physiology and pharmacology as the fast transient component, suggesting that the two components are carried by the same population of channels. The physiology and pharmacology of these various currents were not remarkable save for the fact that, contrary to earlier reports, all sodium currents examined were sensitive to tetrodotoxin (TTX). These animals are, therefore, the lowest animals known to possess TTX-sensitive sodium currents and, as such, represent a major stage in sodium channel evolution.
Excretion in the House Cricket: Stimulation of Rectal Reabsorption by Homogenates of the Corpus Cardiacum
Authors: Spring Jeffrey H. , Albarwani Sulayma A.
Published: April 2021

We describe an in vitro perfused preparation of Acheta domesticus rectum which allows direct comparison of Malpighian tubule secretion and rectal absorption under identical conditions. Rectal absorption is stimulated four-to sixfold by corpora cardiaca (CC) homogenates and the stimulated rate is sufficiently rapid to account for all the fluid secreted by the tubules. The time course for increased fluid absorption is similar to that required to stimulate electrogenic chloride transport in locusts and grasshoppers. Chloride is rapidly absorbed by the rectum under all conditions, along with lesser amounts of Na+ and K+. Unlike the situation in locusts, K+ uptake is unaffected by CC homogenates and the stimulated absorbate is NaCl-rich, similar in composition to the NaCl-rich tubule fluid produced under stimulated conditions. The absorbate is always slightly hypo-osmotic to the perfusate, reaching a maximum differential of approximately 15 mosmoll-1 following CC stimulation. The antidiuretic factor that reduces tubule secretion does not promote fluid reabsorption by the rectum.
A Three-Compartment Model Describing Temperature Changes in Tethered Flying Blowflies
Authors: Stavenga D. G. , Schwering P. B. W. , Tinbergen J.
Published: April 2021

A three-compartment model is presented that describes temperature measurements of tethered flying blowflies, obtained by thermal imaging. During rest, the body temperature is approximately equal to the ambient temperature. At the start of flight, the thorax temperature increases exponentially with a time constant of 30s; in steady flight, a temperature of approximately 30°C is reached (ambient temperature approximately 25°C). After flight, the temperature of the thorax decreases exponentially with a time constant of 50s. Fitting the time courses of the three body compartments, i.e. head, thorax and abdomen, with the model allows the thermal parameters to be calculated. The metabolic heat produced by a blowfly during tethered flight is estimated to be approximately 23mW.
Anosmia In ZnSO4-Treated Pigeons: Loss of Olfactory Information During Ontogeny and the Role of Site Familiarity in Homing Experiments
Authors: Schmid Jutta , Schlund Wolfgang
Published: April 2021

Depriving homing pigeons of olfactory information by spraying an 18% zinc sulphate solution onto their olfactory ephithelium results in anosmia that persists for at least 5 days (tested using the ‘orienting response’). To study whether anosmic zinc-sulphate-treated pigeons (ZnSO4-pigeons) were able to compensate for their loss of olfactory information by using familiar landmarks, we made releases from two different distances (9–24km, 54–70km). The birds had homed once before from each release site. At shorter distances, ZnSO4-pigeons, sham-treated controls and untreated super controls were well oriented. At the longer distances, the anosmic pigeons and the sham-treated controls did not show any directional preference whereas the super controls were oriented towards home. In all cases, however, fewer anosmic pigeons homed successfully and their homing speed was slower than the speed of either control group.

In order to determine whether experience during ontogeny affects the orientation behaviour, a group of young pigeons was reared anosmically by application of ZnSO4 solution once a week. A second group of experimental pigeons was made anosmic just before the critical release. When released at unfamiliar sites located between 15 and 24km from home, all but the group of short-term ZnSO4-pigeons were well oriented. Neither permanently nor temporarily anosmic ZnSO4-pigeons showed good homing performances. These data indicate that homing pigeons determine their home direction by relying on the navigational factors they have collected during rearing. The paradoxical finding that anosmically reared pigeons were oriented towards home but did not home successfully leads to the questions of whether intra-nasal irrigation with ZnSO4 solution results in extensive brain damage or whether initial orientation and the rest of the homing process are based on different mechanisms.
Interactions of Acid–base Status and Nitrogen Excretion and Metabolism in the Ureogenic Teleost Opsanus Beta
Authors: Barber M. Lee , Walsh Patrick J.
Published: April 2021

The interactions of acid–base status, waste nitrogen excretion and metabolism in the gulf toadfish Opsanus beta, a ureogenic teleost, were examined by exposing toadfish to a variety of water treatments. Our measurements show that, like other marine teleosts, toadfish rapidly regulate acid–base status by manipulating blood [HCO3−]. Several treatments affected nitrogen excretion. The initial stages of hypercapnia (1% CO2) led to significant reductions in ureogenesis, and the later compensated stages (with elevated plasma [HCO3−]) led to significant increases in ureogenesis. Treatment of water with HCl (which lowered pH and reduced the carbonate content) substantially inhibited ureogenesis. Subsequent experiments with NH4Cl loading and several other treatments suggest that this depression is less likely to be the result of acid–base perturbations, but is probably an enhancement of the fish’s ability to excrete waste nitrogen as ammonia, thereby decreasing the drive for ureogenesis. Enzyme activities and hepatocyte ureogenic potential were unaffected by various acid–base treatments, but a significant depletion of plasma amino acid levels was associated with the increase in plasma [HCO3−] induced by hypercapnia. Changes in ureogenesis associated with our treatments appear to be due primarily to changes in substrate levels, rather than to wholesale changes of the biochemical machinery. Our results are discussed in the context of the hypothesis of Atkinson and colleagues, that ureogenesis is a means for acid–base regulation via bicarbonate consumption.
Ventilatory responses to hypoxia in the toad Bufo paracnemis before and after a decrease in haemoglobin oxygen-carrying capacity
Authors: Wang Tobias , Branco Luiz G. S. , Glass Mogens L.
Published: April 2021

The ventilatory and cardiovascular effects of a decreased O2-carrying capacity of the blood were evaluated in the toad Bufo paracnemis. Pulmonary ventilation was monitored using a pneumotachographic technique. Chronic arterial catheters served to record both cardiac frequency and blood pressure and enabled the withdrawal of blood samples for analysis of pH and partial pressure of O2. Haemoglobin concentrations were determined by the cyanmethaemoglobin method. The ventilatory response to hypoxia was not affected by the reduction in blood O2-carrying capacity, which suggests that rather than O2 content is the regulated variable. The reduction in capacity is accompanied by an increased normoxic heart rate and by a reversal of the hypoxic tachycardia normally observed.