bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental Changes in Cardiac and Metabolic Physiology of the Direct-Developing Tropical FrogEleutherodactylus Coqui
Authors: Burggren Warren W. , Infantino Robert L. , Townsend Daniel S.
Published: April 2021

The neotropical frog Eleutherodactylus coqui (Thomas) undergoes direct development within the egg, emerging at hatching as a juvenile frog. The aim of this study was to investigate cardiorespiratory changes that accompany development, as well as to determine how the developmental physiology of direct-developing anurans differs from anurans with free-living larval stages. Heart rate (fH), oxygen uptake , vitelline fluid pH, and the protein and lactate concentrations of vitelline fluid were measured as a function of development. At 24–25 °C, fH doubled from 50 to 100 beats min−1 during the early stages of heart development, then increased more slowly with later embryonic development to 120 beats min−1 at hatching. The act of hatching itself was accompanied by a transient increase in fH to 155 beats min−1, this mild tachycardia lasting for at least 2 h. In juveniles and adults, heart rate decreased with increasing body mass, falling to about 80beats min−1 in 6 g frogs at 24–25°C. at 24–25 °C increased from about 2μmol g egg−1h−1 for the earliest embryos examined to about 12μmolg egg−1h−1 at hatching. in adults decreased with increasing body size, ranging from 4 to 5μmolg−1h−1 in the largest adults examined (6g). Both fH and were also measured at 18°C. The Q10 for/it was between 1.5 and 2 throughout development. The Q10 for in embryos ranged between 3.5 and 6.5 until hatching, falling to 1.6–2.0 in juveniles and small adults. Vitelline fluid pH (24–25°C) decreased from 5.2’ in early embryonic stages to 4.7 at the time of hatching. Egg dehydration caused a significant decrease in the pH of vitelline fluid and was associated with a significant rise in fH. Vitelline fluid protein concentration was about 5–6mgdl−1, and showed no consistent change with development. Whole-egg lactate concentration ranged from 4 to 11 μ g g egg−1, and also showed no consistent change during development. These findings indicate considerable changes in cardiac and metabolic physiology associated with opment in Eleutherodactylus coqui. These changes appear to be associated with both organogenesis (primary influence before hatching) and body mass changes (primary influence after hatching).
Effects of taurine on Ca2+-dependent force development of skinned muscle fibre preparations
Authors: Galler S. , Hutzler C. , Haller T.
Published: April 2021

The effects of the naturally occurring amino acid taurine (2-aminoethanesul-phonic acid) on isometric force development were investigated using skinned muscle fibre preparations. In atrial and ventricular pig heart muscles, as well as in fibres of slow abdominal extensor muscle of crayfish, an increase of submaximal isometric force was observed in Ca2+-activated skinned fibre preparations at physiological concentrations of taurine. The maximal isometric force remained unaffected in all preparations. It is assumed that taurine increases the Ca2+ sensitivity of the force-generating myofilaments in mammalian hearts and tacean slow skeletal muscle fibres.
Control of Locomotion in the Freshwater SnailPlanorbis CorneusI. Locomotory Repertoire of the Snail
Authors: Deliagina T. G. , Orlovsky G. N.
Published: April 2021

The freshwater snail Planorbis corneus moves as a result of the beating of cilia covering the sole of the foot. The tracks of snails crawling on the walls and on the bottom of an aquarium were recorded visually under various conditions of snail feeding. The following results were obtained.

In the absence of food, the snails exhibited diurnal changes in locomotor activity, with a maximum during the day. Horizontal tracks on the aquarium walls were commonest during the day and vertical ones at night. When crawling on the aquarium wall, the snail actively stabilized its horizontal or vertical orientation: when encountering an obstacle or after a forced turn, the snail re-established the initial direction of locomotion. When fed on the water surface, the snail decreased its locomotor speed if food particles entered its mouth. The decrease in speed resulted from the slowing down of ciliary beating in the anterior part of the sole of the foot. This finding demonstrates that motor activity in different parts of the ciliated epithelium can be controlled independently by the nervous system. When searching for food particles, the snail exhibited very sinuous tracks, the turns occurring spontaneously at irregular intervals. This finding shows that there is a programme of ‘looping’ in the nervous system. When the snail was fed on the bottom near a vertical wall, it used the wall to climb to the water surface for lung ventilation. After ventilation, the snail performed a standard 180° turn and then returned to the food along the original outward track. Motion along a track was performed with high accuracy. The locomotor apparatus of a snail allowed it to crawl not only on a flat surface but also along the very thin mucus thread that it makes.
Adaptations to a Terrestrial Existence by the Robber CrabBirgus Latro: VI. The Role of the Excretory System in Fluid Balance
Authors: Greenaway Peter , Taylor H. H. , Morris S.
Published: April 2021

Primary urine is formed by filtration in the antennal organ of Birgus latro L. Urine isosmotic with the haemolymph is released into the anterior branchial chambers where substantial reabsorption of water and ions may occur. Some of the branchial fluid is ingested and the remainder (final excretory fluid, P) is released.

Crabs supplied with fresh water have a low drinking rate (1.82ml 100g−1 day−1). Primary urine is partially reabsorbed (27%) in the antennal organ and urine flow (4.48 ml 100 g−1 day−1) is significantly lower than filtration rate (5.77ml 100g−1 day−1). The volume of P released is small in crabs drinking fresh water (0.45 ml 100 g−1 day−1) and the fluid is dilute (≈25mmoll−1 NaCl). The difference between P flow and drinking rate (1.37ml 100 g−1 day−1) represents evaporative and faecal water losses.

Provision of saline drinking water (300, 600 or 1000mosmolkg−1 sea water) doubles rates of drinking, filtration and urine flow and increases P flow fourfold. Evaporative/faecal water loss remains constant. Reabsorption of salts from the P rapidly decreases when saline media are provided for drinking.
The Cooling Power of Pigeon Wings
Authors: Craig Albert , Larochelle Jacques
Published: April 2021

The rate of heat loss through the stretched wings (Ḣwings) was studied in resting pigeons preheated to a body temperature (43.7°C) within the range of those recorded during flight. The experimental system was designed to allow the calculation of Ḣwings from the increase in whole-body cooling rates resulting from exposure of the wings to various wind speeds (0–50 km h−1) at 23°C. The maximum value of Ḣwings was 3.8 W, less than twice the heat production of a resting pigeon. This indicates that the contribution of the wings to heat dissipation during flight may not be nearly as important as has been supposed. At low windspeeds (0–12.5 km h−1), Ḣwings corresponded to about 40% of the resting rate of heat production, and this value is discussed in connection with the various wing postures observed in hyperthermic birds.
Mechanics of Breathing in Horses at Rest and During Exercise
Authors: Lafortuna Claudio L. , Saibene Franco
Published: April 2021

The respiratory mechanics together with the rate of work of breathing were studied in five healthy adult Standardbred horses at rest and during different levels of exercise on a treadmill (0.8–2.3 ms−1, 7% slope). In three of the horses the stride frequency was also determined.

The ventilatory response to exercise increased linearly with treadmill speed up to 9.6 times the resting values and was sustained more by an increase in respiratory frequency than by an increase in tidal volume. At the most elevated work load, respiratory frequency and tidal volume averaged 5.2 and 1.4 times the resting values, respectively. Lung resistance decreased during the most intense level of exercise to about 30% of the average value observed at rest, while lung dynamic compliance remained unchanged. The rate of work of breathing (Ẇresp, in W) increased exponentially with ventilation (, in 1min−1) according to the equation: . In the three animals investigated a definite locomotor-respiratory coupling was observed at a trot and in two animals also during walking. This observation, together with other considerations based on available data on the energetics of respiration, suggests that the efficiency of the equine respiratory system is relatively high. In addition, when compared with other smaller mammals (man and dog), horses are, in mechanical terms, more economical breathers.
Temperature Acclimation in the Common Carp: Force-Velocity Characteristics and Myosin Subunit Composition of Slow Muscle Fibres
Authors: Langfeld Karen S. , Crockford Tony , Johnston Ian A.
Published: April 2021

Live slow fibre bundles were isolated from the superficial region of the pectoral fin abductor superficialis muscle of common carp (Cyprinus carpio L.) acclimated to either 8 or 20°C.

The maximum tetanic tension (P0) of fibre bundles was similar when measured at the acclimation temperature of each group. However, at 8°C, P0 was significantly higher in 8 °C-than in 20°C-acclimated fish (202 ±8 versus 153±4kNm−2, respectively). For isometric tetani at 8°C, the times to 50% peak force and from peak force to 50 % relaxation were 15–20 % faster in preparations from cold-than from warm-acclimated carp. Force-velocity (P–V) curves were fitted using a hyperbolic-linear equation. The curvature of the P–V relationship was found to be independent of acclimation temperature. Unloaded contraction velocity (Vmax) was 17 % higher at 8°C in fibres from fish acclimated to 8°C than in fish acclimated to 20°C (1.18±0.04 and 0.98±0.04 muscle lengths s−1, respectively). Calculated values for maximum power output at 8°C were 26.5 W kg−1 for cold-acclimated and 18.0 W kg−1 for warm-acclimated fish.

Native myosin was purified from isolated fibre bundles using sodium pyrophosphate gel electrophoresis. The mobility of myosin heavy chains on 8% SDS– PAGE gels was similar for both acclimation groups. Myosin light chain subunits were separated on 15% SDS–PAGE gels. Fibre bundles from warm-acclimated fish contained almost exclusively slow myosin light chains (LC1S and LC2S). Preparations from cold-acclimated fish contained a significant proportion of fast myosin light chains (LClf and LC2f) in addition to LC1S and LC2S. Histochemical studies revealed no differences in the fibre composition of preparations from warm- and cold-acclimated fish: both contained an average of 3% fast oxidative fibres in addition to slow fibres.

It is concluded that cold-acclimation results in modest improvements in the contractile performance of slow muscle fibres at low temperatures. The mechanism may involve the expression of myosin light chain isoforms normally associated with faster-contracting fibre types.
Cytoplasmic pH and Goblet Cavity pH in the Posterior Midgut of the Tobacco Hornworm Manduca Sexta
Authors: Chao Anthony C. , Moffett David F. , Koch Alan
Published: April 2021

In the larval lepidopteran midgut, the major energy-requiring step of transepi-thelial K+ secretion occurs across the goblet cell apical membrane. Studies of vesicles of goblet cell apical membrane suggest that K+ secretion across this membrane is a secondary active process in which electroneutral K+/H+ antiport is driven by primary electrogenic H+ secretion. Transbasal K+ movement is thermodynamically passive under standard conditions, but the presence of an active process is revealed in hypoxic solutions or at low extracellular K+ concentration.

We measured the pH of cytoplasm and goblet cell cavities, together with the corresponding transmembrane voltages, using double-barreled pH and voltage-sensing microelectrodes. For short-circuited midguts in standard bathing solution (pH 8.0) the weighted mean of cytoplasmic pH was 7.14±0.06 (mean±s.E.M.), an average of 0.34 units more acid than expected for electrochemical equilibrium with the hemolymphal solution. The mean pH of goblet cavities was 7.23±0.11, 1.62 units more acid than expected for equilibrium with the luminal solution. The pH gradient across the goblet cell apical membrane is thus of the wrong polarity to drive K+ secretion by electroneutral K+/H+ antiport; however, if the exchange ratio were two or more H+ per K+, the cavity-positive electrical potential could drive H+ back to the goblet cell cytoplasm coupled to K+ secretion from cytoplasm to the goblet cavity.

Insensitivity of the goblet cavity pH to the change in the transvalve voltage caused by open-circuiting suggests either that the goblet cavity pH is well regulated or that the valve connecting the cavity to the gut lumen poses a significant barrier to protons. Transbasal potential and cytoplasmic pH were insensitive to a decrease of hemolymphal pH to 6.8, suggesting that the basal membrane is relatively nonconductive to H+. Intracellular pH was unaffected by a decrease of hemolymphal K+ to 5 mmol 1-1 suggesting that K+/H+ exchange is not important for transbasal K+ uptake.
Changes at the Surface of Nereis Limbata Eggs After Insemination
Authors: Novikoff Alex B.
Published: April 2021

One of the classic descriptions of the insemination process is that of F. R. Lillie (1911) in the egg of the annelid, Nereis. According to Lillie, there exists beneath the vitelline membrane of the unfertilized Nereis egg a wide cortical layer. He describes it as “a coarsely alveolar layer with homogeneous alveolar contents. The walls of the alveoli are continuous internally with the protoplasm of egg, and unite externally to form a protoplasmic layer applied to the vitelline membrane.” Within 2 or 3 min. after the attachment of the spermatozoon to the egg, an outpouring of jelly from the cortical alveoli occurs, so that in about 15 min. this layer is represented only by the perivitelline space and the delicate walls of the original alveoli crossing this space to the vitelline membrane. A fertilization cone rises from the egg surface, moves gradually across the perivitelline space, and comes in contact with the membrane beneath the sperm. After the retraction of the cone, the sperm head passes through the membrane into the egg. There is no discussion of the nature of the alveolar walls, nor is there any account of how these walls disappear even though they are not visible in many of the figures.
The Relation Between the Electrolytic Solution Pressures of the Metals and Their Toxicity to the Stickleback (Gasterosteus Aculeatus L.)
Authors: Jones J. R. Erichsen
Published: April 2021

Lethal concentration limits have been determined for the hydrogen ion and the ions of eighteen metals. The three-spined stickleback (Gasterosteus aculeatus L.) has been employed as test animal. According to their lethal concentration limits on a mg./l. basis their order of increasing toxicity is : Sr Ca Na Ba Mg K Mn″ Co″ Cr″ Ni″ Au″ Zn Cd″ Pb″ Al Cu″ H Hg″ Ag. On a molar concentration basis the order is as follows: Na Ca Sr Mg Ba K Mn″ Co″ Cr″′ Ni″ H Zn Al Au″′ Cd″ Pb″ Cu″ Hg″ Ag. All these ions, with the exception of the first six (the metals of the alkalis and alkaline earths), bring about the death of fish by precipitating the gill secretions, thus causing asphyxiation. The alkali and alkaline earth metals appear to enter the body and act as true internal poisons. The position of iron is uncertain. The toxicity of solutions of iron salts appears to be due, mainly if not entirely, to their acidity. On a mg./l. or molar concentration basis there is a marked relationship between the toxicity of the metals and their solution pressures. The metals of very low solution pressure (Ag, Cu, etc.), i.e. those whose ions are most ready to part with their charges and enter into combination with other ions or compounds, are the most toxic as they precipitate the gill secretions and bring about asphyxiation with extreme rapidity. Metals of somewhat higher solution pressure (Zn, Pb, Cd) act in the same way but more slowly. Manganese, which of all the heavy metals has the highest solution pressure, takes effect very slowly and the ions of the alkali and alkaline earth metals, which have a high affinity for their charges, do not precipitate the gill secretions at all. In the case of all the ions other than those of the alkali and alkaline earth metals the reactions responsible for the death of the fish take place outside the body. Thus their speed of action does not depend on their penetrating power and the permeability factor does not enter. This is probably responsible in great measure for the good agreement observed between their toxicity and their affinity for their electrical charges.
The Micro-Estimation of Sulphates in Sea Water and The Body Fluids of Marine Animals
Authors: Webb D. A.
Published: April 2021

In a series of methods recently proposed (Robertson & Webb, 1939) for the micro-estimation of the principal constituents of sea water and of the body fluids of marine animals, that for sulphate was on the whole the least satisfactory. As there described it consists of precipitation by means of barium chloride and direct titration of the excess barium with sodium sulphate, using rhodizonic acid as indicator. The simplicity of the method is to some extent outweighed by the capricious behaviour of the indicator, which renders the judging of the end-point an operation which, even after considerable practice, it is difficult to perform with great confidence. Although the error may usually be kept without difficulty below 2 %, duplicate titrations are necessary if an occasional error somewhat larger than this is to be avoided. In cases where speed is of greater importance than the highest accuracy the method is probably the best that is available, but it was thought that an alternative method, based on that of Van Slyke et al. (1927) for total base in blood, might be made to yield more accurate results and require less practice.
Photomechanical Changes in the Pineal of Lampreys
Authors: Knowles F. G. W.
Published: April 2021

The pigment present in the pineals of ammocoete larvae is a reflecting pigment. There are indications from its solubilities that this pigment is guanin. No differences in the distribution of this pineal pigment can be seen in animals kept under various conditions of illumination, or when examined soon after transference from light to darkness. The position of the nuclei in the pineal retinal cells changes under different conditions of illumination. They are diffusely scattered in the retinal region of the pineals of animals kept in the dark for seven days, but in animals kept in moderate illumination, the nuclei take up the same position in each retinal cell, thus presenting the appearance of a line of nuclei when viewed laterally. Strong illumination further accentuates this linear distribution of the nuclei. These changes further substantiate the view that the pineals of ammocoete larvae are sensitive to changes of illumination.
Muscle Action During Locomotion: A Comparative Perspective
Authors: Johnston Ian A.
Published: April 2021

This essay explores how the properties of striated muscles are matched to the tasks they perform during running, swimming and flying. During exercise the major locomotory muscles undergo alternate cycles of lengthening and shortening. Force development is greatly influenced by the timing of stimulation in relation to the length-change cycle and by the nature of elastic structures connecting the muscle fibres to the skeleton. The storage and recovery of elastic strain energy by the tendons (apodema in insects) results in a considerable saving of metabolic energy. Strain is independent of locomotory frequency, body size and muscle temperature. In contrast, the frequency of cycles, and hence strain rate, generally increases with speed and is inversely proportional to body size. The maximum isometric stress (P0) striated muscles can exert is rather similar. During steady running or hopping in mammals the peak muscle stress is around one-third of P0. Behaviours such as vertical jumping impose higher stresses requiring disproportionately larger muscles and tendons, which may limit the storage of elastic strain energy. Muscles of small animals consume significantly more energy per gram than do those of large ones. This may be because they need to activate and deactivate their muscles at a higher rate to move at an equivalent speed. When differences in force production are normalised, by multiplying the energy consumed per stride by stride frequency, similar values for the mass-specific cost of locomotion are found in animals with different leg architectures, numbers of legs, skeletal type, body sizes and muscle temperatures.

The power output of isolated muscle fibres can be measured by imposing cyclical strain fluctuations and stimulating briefly during each cycle to approximate normal operating conditions in vivo. This approach yields values for maximum power output of 76–130 W kg−1 for synchronous insect flight muscles at temperatures and wingbeat frequencies appropriate for flight. Frog sartorius muscle produces 20 W kg−1 at the hopping frequency used during escapes at 20°C. The strain rates and deactivation rates of muscle fibres are optimised to produce maximum power over a particular range of locomotory frequencies. In vertebrates this necessitates the sequential recruitment of muscle fibre types with faster maximum strain rates and shorter contraction times as speed increases. Estimates of overall muscle efficiency during locomotion in insects, fish and small mammals are mostly in the range 6–20%.
The Energetics and Cardiorespiratory Correlates of Mammalian Terrestrial Locomotion
Authors: Baudinette R. V.
Published: April 2021

Energy costs of locomotion in mammals can be predicted from running speed and body mass, with the minimum cost decreasing regularly with increasing mass (Mb−0.30). The predictive value of this model is surprising, given the differences in gait and limb structure among mammals. The decrease in mass-specific cost cannot be explained by the work done in moving the limbs and the centre of mass, as animals of different sizes do the same amount of work to move a unit mass a unit distance. The magnitude of the muscle forces involved and the shortening velocity are more likely causes. Terrestrial mammals use a variety of gaits to minimise locomotory energy costs with a ‘preferred speed’ within each of those gaits correlating with the point of greatest economy. The maximum mass-specific energy cost during locomotion is about 10 times the resting level, but there is marked variation among species, especially between wild and domestic forms.

The total cost for locomotion in mammals lies between 1 and 6% of the daily energy budget. Hopping is an energetically cheap way of moving in large animals and correlates with phase-locking of respiratory and limb frequencies. This form of coupling is also seen in most other mammals, especially at higher running speeds.

Comparison of the relative costs of running, flying and swimming for a given body mass shows a respective decrease, but each of these costs scales similarly with body size.
Limitations on Animal Flight Performance
Authors: Ellington C. P.
Published: April 2021

Flight performance seems to change systematically with body size: small animals can hover and fly over a wide range of speeds, but large birds taxi for takeoff and then fly over a narrow speed range. The traditional explanation for this is that the mass-specific power required for flight varies with speed according to a U-shaped curve, and it also scales between m0 and m1/6, where m is body mass. The mass-specific power available from the flight muscles is assumed to scale as m−1/3 As available power decreases with increasing body size, the range of attainable flight speeds becomes progressively reduced until the largest animals can only fly in the trough of the U-shaped curve. Above a particular size, the available power is insufficient and flapping flight is not possible.

The underlying assumptions of this argument are examined in this review. Metabolic measurements are more consistent with a J-shaped curve, with little change in power from hovering to intermediate flight speeds, than with a U-shaped curve. Scaling of the mass-specific power required to fly agrees with predictions. The mass-specific power available from, the muscles, estimated from maximal loading studies, varies as m0.13. This scaling cannot be distinguished from that of the power required to fly, refuting the argument that power imposes an intrinsic scaling on flight performance. It is suggested instead that limitations on low-speed performance result from an adverse scaling of lift production with increasing body size
Rotational Movement of a Spermatozoon Around Its Long Axis
Authors: Ishijima Sumio , Hamaguchi Miyako S. , Naruse Masakazu , Ishijima Sanae A. , Hamaguchi Yukihisa
Published: April 2021

The rotational movement of a spermatozoon around its longitudinal axis was investigated by two methods: by observing a spermatozoon attached vertically to a coverslip by the tip of its head, and by observing a spermatozoon freely swimming in a medium by means of ‘double-focal microscopy’, which yielded simultaneous images at two different focal planes.

Similar results were obtained by these two methods. Sea urchin, starfish, medaka, human, golden hamster and bull spermatozoa rolled in both clockwise and counterclockwise directions, although there was a large difference in the proportion of spermatozoa rolling in each direction in the different species. The majority of sea urchin and starfish spermatozoa rolled in a clockwise direction when an observer viewed the cell from its anterior end, whereas the majority of medaka, golden hamster, human and bull spermatozoa rolled in a counterclock-wise direction relative to the same observer. Moreover, some spermatozoa occasionally changed their rotational direction.

These results suggest that the mechanism regulating the direction of rotation of the spermatozoa is lax. As rotational movement of a spermatozoon around its longitudinal axis is due to the three-dimensional component of the beat of the flagellum, the direction of the three-dimensional movement presumably changes as the spermatozoa swim.
Penetration of Water Into Blind-Ended Capillary Tubes and Its Bearing on the Functional Design of the Lungs of Soldier Crabs Mictyris Longicarpus
Authors: Maitland David P. , Maitland Arthur
Published: April 2021

Soldier crabs, Mictyris longicarpus Latreille, inhabit intertidal sand-flats of Eastern Australia. Their gill chambers are modified for both water circulation and air-breathing. Water circulates through the lower gill compartments. The upper regions of the gill chambers are air-filled and function as lungs. The deep vascular parenchyma lining the upper gill chambers, or lungs, is penetrated by a regular series of fine branching airways. Scanning electron micrographs of lung architecture are shown. Measurements relating to lung structure were made on plastic casts.

Because of the lung’s design, water circulating through the lower gill compartments does not interfere with lung function. The airways are blind-ended and nonanastomosing, acting in effect as air-filled capillary tubes sealed at one end. A mathematical model and explanation show how the air trapped within this lung structure substantially reduces water penetration, despite surface tension (capillary) processes. This same lung design also facilitates the shedding of the lung cuticle at each moult.
Response Properties Of Interneurons Of The Cricket Cercal Sensory System Are Conserved In Spite Of Changes In Peripheral Receptors During Maturation
Authors: Chiba Akira , Kämper Günter , Murphey R. K.
Published: April 2021

During postembryonic development of the cricket, the total number of filiform hair sensilla in the cereal sensory system increases approximately 40-fold. In addition, individual receptor hairs grow in size, changing the transducer properties of the sensilla and, thereby, the information transmitted to the central nervous system (CNS) by the sensory neurons. Interneurons MGI and 10-3 receive monosynaptic inputs from these sensory neurons and send outputs to anterior ganglia. We show that, in spite of the changes in the periphery, the response properties of these interneurons are relatively constant during development. The two interneurons differ in their frequency response, intensity response and rate of response decrement. Their respective response properties are conserved during the postembryonic period. The results suggest that systematic rearrangement of the sensory neuron-to-interneuron synapses plays an important role in maintaining a constant output of this sensory system to higher centers of the CNS during maturation of the cricket.
Individual and Sex Specificity in the Electric Organ Discharges of Breeding Mormyrid Fish (Pollimyrus Isidori)
Authors: Crawford John D.
Published: April 2021

I monitored the electric organ discharges (EODs) of 14 Pollimyrus isidori, (Cuvier and Valenciennes) during an artificially induced breeding season, to examine sex and individual differences in reproductive fish. EODs were repeatedly recorded over an 11-day period to ascertain the stability of each individual’s EOD and to make a quantitative assessment of sex differences. Within days, I found the individual’s EOD to be constant from one EOD to the next. Over the 11-day sampling period, individuals were also quite stable and exhibited only slight changes in EOD duration and relative amplitude of the phases of the waveform. I found that the differences between individuals of the same sex were highly significant in measures of EOD duration and in measures of the relative amplitude of the phases. Differences between the sexes were also highly significant in relative amplitude but were not significant in duration. In a multivariate discriminant function analysis, I have found that individual fish can be correctly classified on the basis of temporal, relative amplitude and spectral cues in the EOD, despite slight changes in these parameters with time. The EOD exhibits characteristics of a good signature in the context of an information system.
The Profile Drag of A Hawk’s Wing, Measured by Wake Sampling in A Wind Tunnel
Authors: Pennycuick C. J. , Heine Carlton E , Kirkpatrick Sean J. , Fuller Mark R.
Published: April 2021

The distribution of dynamic pressure behind a Harris’ hawk’s wing was sampled using a wake rake consisting of 15 pitot tubes and one static tube. The hawk was holding on to a perch, but at an air speed and gliding angle at which it was capable of gliding. The perch was instrumented, so that the lift developed by the wing was known and the lift coefficient could be calculated. The mean of 92 estimates of profile drag coefficient was 0.0207, with standard deviation 0.0079. Lift coefficients ranged from 0.51 to 1.08. Reynolds numbers were nearly all in the range 143000–194000. The estimates of profile drag coefficient were reconcilable with previous estimates of the wing profile drag of the same bird, obtained by the subtractive method, and also with values predicted by the ‘Airfoil-ii’ program for designing aerofoils, based on a digitized wing profile from the ulnar region of the wing. The thickness of the wake suggested that the boundary layer was mostly or fully turbulent in most observations and separated in some, possibly as an active means of creating drag for control purposes. It appears that the bird could momentarily either increase or decrease the profile drag of specific parts of the wing, by active changes of shape, and it appeared to use the carpo-metacarpal region especially for such control movements. Further investigation in a low-turbulence wind tunnel would help to resolve doubts about the possible influence of airstream turbulence on the behaviour of the boundary layer.
The Perception Of The Visual Flow Field By Flying Locusts: A Behavioural And Neuronal Analysis
Authors: Baader Andreas , Schäfer Marcel , Rowell C. H. F.
Published: April 2021

Tethered locusts (Locusta migratoria’) were stimulated with an artificial flow field (FF) device, which produced the visual effect of forward motion (‘progressive flow field’) or backward motion (‘regressive flow field’). Progressive FFs (contrast frequencies, CF, of 2–10Hz and angular period of pattern, λ, of 33° or 42°) can initiate and maintain flight, even without frontal wind. Regressive FFs inhibit flight. The locusts adjust their wingbeat frequency (and thus probably their flight speed) in response to a gradually changing FF contrast frequency; they fly faster when the FF motion is faster and vice versa. Sudden decelerations of FF motion, however, are transiently counteracted by increases in wingbeat frequency. Rotational movements of the entire flow field device, simulating yaw and/or roll deviations during progressive flight, elicit compensatory steering responses of the head and abdomen. Corrective steering behaviour and simultaneously presented FF stimuli do not influence each other. A descending interneurone (FFDN1) is described which reports the progressive visual FF. It receives input from both compound eyes, prefers FFs on the ventral retina, and responds over the range of contrast frequencies of 1–20 Hz. Its response is tonic and adapts only weakly to maintained FF stimuli. It follows changing FF velocities but tends to counteract sudden decelerations. In addition, FFDN1 is excited by frontal and contralateral wind and inhibited by ipsilateral wind. It is also excited by the flight motor and sometimes by light-off at the ocelli. The neurone is generally insensitive to simulated roll and yaw deviations. Electrical stimulation of the cell can result in lifting of the abdomen, inhibition of dorsal neck muscle activity, and occasional flight muscle spikes. FFDN1 is probably a sister cell of the previously described DNM neurone, but the two could be one neurone with very variable responses. At least one further descending interneurone responding selectively to progressive flow fields, but with a different morphology, is present in the central nervous system. Additionally, two different thoracic intemeurones have been found with properties suggesting that they are postsynaptic to FFDNs and presynaptic to the flight circuitry.

5. The possible role of the visual flow field in the regulation of flight activity of locusts and other insects is discussed.
Heart Rates and Swim Speeds of Emperor Penguins Diving Under Sea Ice
Authors: Kooyman Gerald L. , Ponganis Paul J. , Castellini Michael A. , Ponganis Edward P. , Ponganis Katherine V. , Thorson Philip H. , Eckert Scott A. , Lemaho Yvon
Published: April 2021

Heart rate during overnight rest and while diving were recorded from five emperor penguins with a microprocessor-controlled submersible recorder. Heart rate, cardiac output and stroke volume were also measured in two resting emperor penguins using standard electrocardiography and thermodilution measurements. Swim velocities from eight birds were obtained with the submersible recorder. The resting average of the mean heart rates was 72 beats min−1. Diving heart rates were about 15 % lower than resting rates. Cardiac outputs of 1.9–2.9mlkg−1 s−1 and stroke volumes of 1.6–2.7 ml kg−1 were similar to values recorded from mammals of the same body mass. Swim velocities averaged 3ms−1. The swim speeds and heart rates suggest that muscle O2 depletion must occur frequently: therefore, many dives require a significant energy contribution from anaerobic glycolysis.
Interactive Effects of Seasonal Temperature and Low pH on Resting Oxygen Uptake and Swimming Performance of Adult Brown Trout Salmo Trutta
Authors: Butler P. J. , Day N. , Namba K.
Published: April 2021

Adult brown trout were acclimated for 2–4 weeks to artificial, soft water (Ca2+ 25μmol l-1) at neutral pH and at summer (15°C) or winter (5°C) temperatures. During this period they swam against a current of approximately 0.25 ms-1. They were then exposed to neutral or sublethal pH for 4 days in still water. For fish with their dorsal aorta catheterized, sublethal pH was 4 at 5°C and 4.5 at 15°C.

After 4 days of exposure to sublethal pH, resting oxygen uptake was 40 % higher than that at neutral pH for fish held at 15 °C and 38 % higher for fish held at 5°C. Critical swimming speeds (Ucrit), in contrast, were 35% and 31% lower, respectively. These two phenomena may be related in as much as the ‘metabolic cost’ of exposure to low pH may increase as swimming speed increases, thus reducing the scope for activity. Another important factor could be an impairment of oxygen delivery to the red muscle fibres. Although arterial O2 concentrations and heart rate are both similar for fish at Ucrit in neutral and acid water, there are signs of haemoconcentration in fish exposed to low pH, and the consequent increase in blood viscosity could disrupt the local circulation in the red fibres. Whatever its causes, an impairment of swimming activity resulting from exposure to acid water may have severe consequences for active fish such as salmonids.

Exposure to sublethal pH caused significant reductions in plasma Na+ and Cl-concentrations at both temperatures, although these were more substantial at 5°C than at 15 °C. Swimming at Ucrit had no significant effect on plasma concentrations of Na+, K+ and Cl- except at sublethal pH at 5°C, when there were significant reductions in all three.

Seasonal temperature had significant but small effects on resting and Ucrit, and these are discussed in terms of the possible effects of low temperature and continued swimming activity (training) on hypertrophy of skeletal and cardiac muscles and on the aerobic capacity of the ‘red’ muscle fibres.
Walking of the Shore Crab Pachygrapsus Crassipes in its two Natural Environments
Authors: Hui Clifford A.
Published: April 2021

Video analyses of crabs walking on smooth and rocky terrains when in air and when submerged in water were conducted. Modifications of walking in the two environments, between which the animal’s weight changes sixfold, are consistent with the goals of maximizing ease of walking and minimizing risk of injury. The duty factor (fraction of step cycle in which the dactylus is in contact with the substratum) was greater than 50 % when in air compared to less than 46 % when submerged, indicating a need for greater stability against the destabilizing vertical force of gravity when in air. The duty factors of the trailing and leading leg rows were the same for the two terrains in air but the trailing leg row had a larger duty factor when submerged, indicating a greater pushing effort to overcome drag forces. Width of stance differed among the four conditions and was narrowest in animals walking over rocky terrain in air, the condition which has the greatest potential for injury. The mean phase difference (percentage of a step cycle by which ipsilateral legs differ) between leading and trailing rows did not differ under any condition except for submerged smooth terrain, meeting the unique requirements of that condition. The observed walking speed range had no effect on stance, duty factor or phase difference.
Arterio-Venous Branchial Blood Flow in the Atlantic Cod Gadus Morhua
Authors: Sundin Lena , Nilsson Stefan
Published: April 2021

We have estimated the branchial venous blood flow in the Atlantic cod by direct single-crystal Doppler blood flow measurements in vivo. In the undisturbed animal, this flow amounts to 1.7 ml min−1 kg−1, which corresponds to about 8 % of the cardiac output. Studies of both an isolated perfused gill apparatus in situ and simultaneous measurements of cardiac output and branchial venous flow in vivo were made to assess the effects of some putative vasoregulatory substances. Adrenaline dilates the arterio-arterial pathway and constricts the arterio-venous pathway, thus decreasing branchial venous drainage. 5-Hydroxytryptamine (5-HT), in contrast, produced marked vasoconstriction in the arterio-arterial pathway of the branchial vasculature, increasing the branchial venous blood flow. Cholecystokinin-8 (CCK-8) and caerulein produced similar cardiovascular effects, with marked constriction of both arterio-arterial and arterio-venous pathways. The study demonstrates the ability of the vascular system of the gills to regulate the distribution of branchial blood flow, and summarizes the vasomotor effects of some substances with possible vasomotor function in the cod gills.
Integrating Metabolic Pathways in Post-Exercise Recovery of White Muscle
Authors: Schulte Patricia M. , Moyes Christopher D. , Hochachka Peter W.
Published: April 2021

Purine nucleotides (ATP, ADP, AMP, IMP), creatine, phosphocreatine, lactate, pyruvate and glycogen were measured in rainbow trout (Oncorhynchus my kiss) white muscle following exercise to exhaustion. Estimates of intracellular pH permitted calculation of free concentrations of nucleotides ([nucleotide]f) required for most models of control of energy metabolism. Creatine charge, [PCr]/([PCr]+[Cr]), fell from 0.49±0.05 (mean±S.E.M.) to 0.08±0.02 with exercise but recovered completely by the first sample (2h). Although [ATP] declined to 24% of resting levels and recovered very slowly, RATP, [ATP]/ ([ATP] + [ADP]f+[AMP]f), and energy charge, EC, ([ATP]+0.5[ADP]f)/ ([ATP] + [ADP]f+[AMP]f), recovered as quickly as creatine charge. Changes in [IMP] mirrored those in [ATP], suggesting that AMP deaminase is responsible for maintaining RATP and EC. Recovery of carbon status was much slower than recovery of energy status. Lactate increased from 4 μmol g−1 at rest to 40 μmol g−1 at exhaustion and did not recover for more than 8h. Glycogen depletion and resynthesis followed a similar time course. During the early stages of recovery, calculated [ADP]f declined by more than 10-fold relative to the resting values. The resulting high [ATP]/[ADP]f ratios may limit the rate at which white muscle mitochondria can produce ATP to fuel glycogenesis in situ. It is postulated that the high [ATP]/[ADP]f ratios are required to drive pyruvate kinase in the reverse direction for glyconeogenesis in recovery.
Blood Flow Distribution in Submerged and Surface-Swimming Ducks
Authors: Stephenson Richard , Jones David R.
Published: April 2021

Observations that the response of the avian heart rate to submergence varies under different circumstances have led to speculation about variability of blood flow distribution during voluntary dives. We used a radiological imaging technique to examine the patterns of circulating blood flow in captive redhead ducks (Aythya americana) during rest, swimming, escape dives, forced dives and trapped escape dives and have shown that blood flow distribution in escape dives was the same as that in ducks swimming at the water surface. The response during trapped escape dives, however, was highly variable. Blood pressure was unchanged from the resting value during all activities. Predictions made about blood flow distribution during unrestrained dives on the basis of heart rate and other indirect data were confirmed in this study. However, the trapped escape dive responses indicated that heart rate alone is not always a reliable indicator of tissue blood flow in exercising ducks.
Mechanisms Controlling Modulation by Haemolymph Amino Acids of Gustatory Responsiveness in The Locust
Authors: Simpson S. J. , Simpson C. L.
Published: April 2021

Previous work has shown that fifth-instar nymphs of Locusta migratoria (L.) adjust their feeding behaviour to compensate for variation in dietary protein and carbohydrate levels. These changes in behaviour are accompanied by nutrient-specific changes in the responsiveness of taste receptors on the mouthparts. Levels of free amino acids in the haemolymph affect the responsiveness of maxillary gustatory receptors to stimulation by amino acids. The mechanisms mediating this response are investigated. Sectioning the maxillary nerve does not prevent an injection of amino acids into the haemolymph from causing reduced chemo-responsiveness, indicating that centrifugal neural feedbacks are not involved. Isolating the distal two segments of the palp by ligature and then micro-injecting amino acids into the palp tip also causes modulation of responsiveness, showing that the effect is mediated at, or close to, the sensory receptors. Radio-labelling studies indicate that amino acids injected into the abdomen are found in the haemolymph of the palp within the time necessary to cause a peripheral change in gustatory responsiveness. Possible mechanisms enabling amino acids in the blood of the palp to influence sensory responsiveness are discussed. The simplest mechanism consists of amino acids in the haemolymph reaching the sensillum liquor and adapting the receptors to further stimulation from the food.
Utilization and Digestion of Carbohydrates by the Adult Blowfly
Authors: Fraenkel Gottfried
Published: April 2021

It has been frequently stated that many species of flies, including houseflies and blowflies, can be kept alive and healthy on a diet consisting only of cane sugar and water; on this they are able to live for the maximum length of time, which, in the case of the blowfly Calliphora erythrocephala, is about 2 months at 27° C. Addition of protein is essential only for the development of the eggs, as it does not increase the duration of life and there is, indeed, evidence that it may have the contrary effect. Flies thus represent an excellent medium for studying problems of carbohydrate metabolism, and the present investigation deals particularly with two questions: what effect have substances other than cane sugar on the length of life of the fly, and to what extent does the presence and absence of enzymes in the gut account for the utilization or non-utilization of these various substances?
Studies on Amphibian Metamorphosis
Authors: Helff O. M.
Published: April 2021

Previous work by the writer has shown that normal development of the tympanic membrane in R. pipiens is due to inductive influences of the annular tympanic cartilage. The present work concerns the nature of the developmental influences, specifically as regards whether or not non-living cartilage still possesses inductive properties. The experiments performed and results obtained were as follows:

Controls consisted of autoplastic transplantation of annular tympanic cartilage beneath back integument of metamorphosed and involuting R. palustris larvae. In general, integumentary thinning, coupled with partial to total glandular degeneration, occurred. This is typical of partial membrane formation.

Similar transplantations were made involving cartilage killed in ethyl alcohol, saturated chloretone solution, and boiling water, or by desiccation in strong sunlight. The results differed considerably depending on the type of killing treatment employed and the degree of subsequent transplant degeneration. Partial membrane formation was usually induced, however, in the overlying back integument. Similar series were run with half-metamorphosed larvae. In general, membrane induction was even more pronounced.

The same experiments were performed on R. catesbeiana larvae. Transplantation, however, was made beneath the skin of the upper jaw, posterior-ventral to the external nares. Wide variations in results were observed. No membrane changes occurred in some cases, while in others considerable transformation was induced.

It is concluded that dead annular tympanic cartilage still retains inductive influences capable of initiating varying degrees of tympanic membrane formation in integument. In general, the greater the degree of cartilage degeneration, the less the extent of membrane formation.

The results are discussed in general and the conclusion reached that the inductive influences arising in the developing annular tympanic cartilage of the anuran are quite probably chemical secretions or excretions. These, when transmitted to the integument of the ear region during metamorphosis, serve to induce a dedifferentiation of the larval skin into that type characteristic of adult tympanic membrane.