bluuebunny/crossref_metadata_2025 huggingface dataset:
Energetic Cost of Locomotion as a Function of Ambient Temperature and During Growth in the Marsupial Potorous Tridactylus
Authors: Baudinette R. V. , Halpern E. Annette , Hinds David S.
Published: April 2021

In the marsupial, the potoroo, multiple regression analysis shows that ambient temperature makes a minor (2%) contribution towards variation in oxygen consumption with speed. This suggests that the heat generated during running is substituted for heat which would otherwise have to be generated for temperature regulation. Maximum levels of oxygen consumption are also temperature-independent over the range 5–25°C, but plasma lactate concentrations at the conclusion of exercise significantly increase with ambient temperature. Adult potoroos show a linear increase in oxygen consumption with speed, and multiple regression indicates that the most significant factor affecting energy use during running is stride length. Juvenile potoroos have an incremental cost of locomotion about 40% lower than that predicted on the basis of body mass. The smaller animals meet the demands of increasing speed by increasing stride length rather than stride frequency, as would be expected in a smaller species. Our results show that juvenile potoroos diverge significantly from models based only on adult animals in incremental changes in stride frequency, length and the cost of transport, suggesting that they are not simply scaled-down adults.
Primary Cultures Of Epithelial Cells From Rainbow Trout Gills
Authors: Pärt P. , Norrgren L. , Bergström E. , Sjöberg P.
Published: April 2021

A method for obtaining primary cultures of epithelial cells from rainbow trout gills is described. The yield of cells from approximately 1.5g wet mass of tissue was 218×106±12×106 cells with a viability defined by eosin exclusion of 80±6%. Cells were seeded in culture dishes and grown in Leibowitz L-15 medium supplemented with 5 % foetal bovine serum. Attachment efficiency after 24h was 35±6%. The cells appeared confluent 10–12 days after seeding and exhibited surface structures similar to those seen on respiratory epithelial cells of trout gills in vivo. Growth rate, [3H]thymidine incorporation and attachment efficiency were used to evaluate culture conditions. Epidermal growth factor, insulin, transferrin, hydrocortisone, laminin and collagen did not improve growth and attachment. Similarly, coating the culture dishes with rat tail collagen, trout skin extract, laminin or a mixture of human basement membrane proteins (Matrigel) failed to improve attachment. It is concluded that the cells in culture are respiratory epithelial cells and that this culture system could provide a valuable new approach for studying the physiology of these cells.
Coordination of Wing Beat and Respiration in Canada Geese During Free Flight
Authors: Funk Gregory D. , Sholomenko Gerald N. , Valenzuela Ignacio J. , Steeves John D. , Milsom William K.
Published: April 2021

It remains unclear whether coordination of wing and respiratory movements is universal among birds during flight (Tomlinson, 1963). However, it is certain that many species demonstrate some form of coordination between wing and respiratory movements (Marey, 1890; Groebbels, 1932; Zimmer, 1935; all cited in Hart and Roy, 1966; Tomlinson, 1957, 1963; Lord et al. 1962; Hart and Roy, 1966; Berger et al. 1970b; Butler et al. 1977; Butler and Woakes, 1980). Ratios of wing beat frequency to respiratory frequency (fW/fV) ranging from 1:1 to 5:1 have been described, some species showing variation in fW/fV (Lord et al. 1962; Berger et al. 1970b; Butler and Woakes, 1980).
An Annular Respirometer for Measuring Aerobic Metabolic Rates of Large, Schooling Fishes
Authors: Lucas M. C. , Johnstone A. D. F. , Tang J.
Published: April 2021

Aerobic metabolic rates of fish at controlled levels of activity are usually measured with individual fish isolated in a flume-type respirometer, in which the fish must swim against a known water velocity (Brett, 1964; Beamish, 1978; Gehrke etal. 1990). Their use for large and fast-swimming fish is difficult owing to engineering problems and water turbulence and because swimming in the confined test section of the respirometer affects the performance of the fish. Some of these problems have been partially dealt with by applying corrections to compensate for the altered water flow around the body of the fish (Webb, 1971) and by developing highly sophisticated flume respirometers (Gehrke et al. 1990).
Generation of Monoclonal Antibodies Detecting Specific Epitopes in Locust Antennae
Authors: Strotmann J. , Boekhoff I. , Göggerle S. , Breer H.
Published: April 2021

Following a tissue-specific screening paradigm, monoclonal antibodies have been generated that interact with distinct subpopulations of cells in locust antennae. Antigens were identified as high molecular weight components. Immunoreactivity was not detectable during embryonic development, but rapidly appeared within a few hours of hatching. The time course of antigen expression in antennal cells could be followed in situ as well as invitro. Expression of monoclonal antibody B14/6D2-like immunoreactivity was prevented by blocking protein synthesis with cycloheximide.
Quantitative Analysis of Chemoaccumulation in Specimens of Paramecium Caudatum in Relation to Their Motile Activities
Authors: Nakazato Hiroyuki , Naitoh Yutaka
Published: April 2021

The quantitative relationship between chemoaccumulation and locomotor activity in specimens of Paramecium caudatum was examined by employing a novel chemoaccumulation assay system. Distribution of the specimens in two adjoining solutions with different chemical compositions was dependent on both the rate of arrival of the specimens at the border between two solutions (the arrival rate) and the ratio of the number of specimens crossing the border to that arriving at the border in unit time (the pass ratio). The arrival rate was higher when the forward swimming velocity was higher and when the frequency of spontaneous avoiding responses was lower. The pass ratio was higher when the degree of the avoiding response at the border was lower. The translocation rate was defined as the number of specimens crossing from one solution to another in unit time, corresponding to the product of the arrival rate and the pass ratio. In the steady-state condition, the distribution ratio, which is defined as the ratio of the number of specimens in the test solution to that in the reference solution, was proportional to the ratio of the translocation rate towards the test solution from the reference solution to that towards the reference solution from the test solution. When specimens showed a higher arrival rate in one solution than the other the pass ratio was lower, so that the arrival rate and the pass ratio acted antagonistically in establishing chemoaccumulation. The involvement of membrane-potential-mediated changes in the motile activity of specimens in establishing chemoaccumulation is discussed.
Guanine Nucleotides Modulate Calcium Currents in a Marine Paramecium
Authors: Bernal Juan , Ehrlich Barbara E.
Published: April 2021

Voltage-dependent calcium channels play a critical role in many cell functions and in many cell types ranging from protozoa to vertebrates. We have shown previously that guanine nucleotides modulate the calcium action potential and the duration of backward swimming in Paramecium, both indirect measurements of calcium channel function. To determine whether guanine nucleotides do indeed alter calcium currents, the inward calcium current (ICa) in Paramecium calkinsi was studied. First, the calcium current was characterized. The magnitude of ICa increased as the extracellular calcium concentration was increased from 0.5 to 50mmol l−1, unlike the situation in freshwater species of Paramecium where the inward calcium current magnitude is maximal when extracellular calcium levels reach 1mmoll−1. Inorganic compounds (NiCl2 at 10 μmoll−1 and CdCl2 at 1mmol l−1) and organic compounds (naphthalene sulfonamides, W-7 and W-12-Br at 100 and 2 μmol l−1, respectively) reduced ICa. Regardless of the holding membrane potential (from −80 to −20mV), the threshold activation for ICa was at −10mV and the maximum value of ICa was reached at +20mV, suggesting that there is only one type of calcium channel in P. calkinsi. Second, we injected GTPγS, GTP and GDPβS into voltage-clamped cells while monitoring calcium and/or potassium currents. GTPγS increased the magnitude of ICa by 42±6% (mean ± S.D., N=5) and the effect was irreversible, GTP increased the magnitude of ICa by 37±4% (N=4) in a reversible manner, and GDPβS decreased ICa by 57±8% (N=3) irreversibly. The outward potassium currents did not change when GTPγS was injected into the cells. These results support the hypothesis that injection of guanine nucleotides modulates the voltage-dependent calcium channel in P. calkinsi, presumably by activating G-protein-dependent processes.
Transcellular Intestinal Calcium Transport in Freshwater and Seawater Fish and its Dependence on Sodium/Calcium Exchange
Authors: Schoenmakers TH. J. M. , Verbost P. M. , Flik G. , Bonga S. E. Wendelaar
Published: April 2021

Transepithelial calcium uptake and transcellular calcium uptake mechanisms were compared in the proximal intestine of freshwater- and seawater-adapted tilapia, Oreochromis mossambicus. Stripped intestinal epithelium of seawater fish showed a higher paracellular permeability to calcium in vitro. Net transepithelial calcium uptake was 71% lower, reflecting a physiological response to the increased inward calcium gradient. Na+/K+-ATPase activity was significantly enhanced in enterocytes of seawater- adapted fish, in line with the water transport function of the intestine in seawater fish. The Vmax and the Km values for Ca2+of the ATP-dependent Ca2+ pump in seawater fish enterocytes were 28% and 27%, respectively, lower than in freshwater fish. The Km for Ca2+ of the Na+/Ca2+ exchanger was 22% lower, and a 57% decrease in the Vmax for Ca2+ of the exchanger was observed. Apparently, the density of exchanger molecules in the basolateral plasma membrane is reduced in seawater fish. From the correlation between the differences in net intestinal calcium uptake and Na+/Ca2+ exchange activity we conclude that Na+/Ca2+ exchange is the main basolateral effector of transcellular calcium uptake.
Separating the Effects of Temperature and Viscosity on Swimming and Water Movement by Sand Dollar Larvae (Dendraster Excentricus)
Authors: Podolsky R. D. , Emlet R. B.
Published: April 2021

The small size and slow movement of aquatic, microscopic organisms means that the viscosity of water has a predominant influence on their motion. Temperature, through its effects on physiological processes, also influences motion. Because water viscosity is physically coupled to temperature, changes in temperature can influence the activity of microscopic organisms through both physiological and physical means. To partition these effects, we artificially altered seawater viscosity and, at two temperatures, we measured swimming speed and water movement by larvae of the sand dollar Dendraster excentricus. Over an environmentally relevant, 10-degree drop in water temperature (22 to 12°C), swimming speed was reduced by approximately 40% and water movement was reduced by 35%. 40% of the decrease in swimming speed and 55% of the decrease in water movement were accounted for by increases in viscosity alone. The physical effects of viscosity can therefore make up a large component of the effect of temperature on activity of microscopic organisms. If uncorrected for effects of viscosity, temperature coefficients such as Q10 values can overestimate the influence of temperature on the physiological processes that underlie the generation of motion at small spatial scales. These changes in viscosity may cause substantial reductions or increases in swimming and feeding rates that are biologically relevant. Environmental variation in viscosity due to temperature fluctuations could lead to temperature responses or adaptations that are nonphysiological.
Acetate, Butyrate and Proline Uptake in the Caecum and Colon of Prairie Voles (Microtus Ochrogaster)
Authors: Hume I. D. , Karasov W. H. , Darken B. W.
Published: April 2021

We have measured unidirectional uptake (not transmural flux) of acetate, butyrate and proline by everted sleeves of intact tissue from the jejunum, caecum, proximal colon and distal colon of prairie voles (Microtus ochrogaster).

There was active (i.e. Na+-dependent) transport of L-proline in the jejunum, but we found no evidence for it in any region of the hindgut (i.e. the caecum, proximal colon and distal colon). Uptake of acetate was carrier-mediated in all three regions of the hindgut, but the Jmax and apparent Km (⩽1.5mmol l−1) were low, and uptake was primarily passive over the concentration range 10–50mmol l−1, which spanned measured acetate levels in the caecum and proximal colon. At 100mmol l−1, acetate uptake (nmolmin−1 cm−2) was higher (P<0.001) in distal colon (359±33) than in the proximal colon (225±17) and caecum (150±5) (mean ± S.E., N=8). Uptakes summed over the length of each region were also higher (P<0.001) in the distal colon at 100mmol l−1, but not at low concentrations (0.1mmol l−1).

Uptakes normalized to diffusion coefficents were higher for butyrate than acetate and were lowest for L-glucose (which is absorbed passively via an aqueous pathway) in all regions, indicating that uptake of the short-chain fatty acids involves solubilization in the lipid bilayer of the apical membrane. The short-chain fatty acids absorbed from the hindgut of the vole were equivalent to 22% of standard metabolic rate or 15% of resting (but fed) metabolic rate.
Lateral Line Stimuli Can Override Vision to Determine Sunfish Strike Trajectory
Authors: Janssen John , Corcoran Jim
Published: April 2021

Although all fishes have a mechanosensory lateral line system – a system of water flow detectors (neuromasts) in canals or free on the skin’s surface – particular behavioral functions are documented for only a few species. Work on lateral line use for feeding has focused on either cavefishes or night-active species (Montgomery, 1989). While surface-feeding fishes with well-developed eyes do use the lateral line to locate prey (Müller and Schwartz, 1982), it is generally assumed that diurnal/crepuscular fishes are visual predators. We show that a hydromechanical stimulus detected by the cephalic lateral line system in two sunfishes (Centrarchidae) can be the sole determinant of a strike trajectory. The response occurs without reinforcement and appears to be an unconditioned response. Green sunfish (Lepomis cyanellus Rafinesque) and largemouth bass (Micropterus salmoides Lacépède) are North American sunfishes that inhabit ponds, lakes and slow streams. Both species have diverse diets, including invertebrates and fishes (Carlander, 1977). These species and their congeners are active during the day; at night in field and laboratory they lie near or on the bottom and are lethargic (Neill and Magnuson, 1974; Helfman, 1981). Both species have cones and rods in the retina; the green sunfish visual pigments are characteristic of crepuscular mid-water fishes (Dearry and Barlow, 1987;
Development of Connections by Axons Growing Through Injured Spinal Cord of Neonatal Opossum in Culture
Authors: Woodward S. K. A. , Treherne J. M. , Knott G. W. , Fernandez J. , Varga Z. M. , Nicholls J. G.
Published: April 2021

The ability of neurites to grow through a lesion and form synaptic connections has been analyzed in a developing mammalian spinal cord in vitro. After isolation of the entire central nervous system (CNS) of the newly born South American opossum (Monodelphis domestica) the spinal cord was crushed. Outgrowth through and beyond the lesion was observed in living preparations for 2–5 days by staining axons with carbocyanine dyes. The structure of the acute crush and the growing neurites was examined by light and electron microscopy in tissue fixed immediately after the crush had been made. All axons had been severed and the site was filled with debris and amorphous vesicular structures. By 3 days after injury, numerous labelled neurites had grown into the lesion; by 4 days, many had extended several millimetres beyond it. At this time normal axonal profiles were apparent in electron micrographs of the crush site. Although fewer axons grew across the lesion than had been severed by the crush, the amplitudes of compound action potential volleys conducted across the crush in injured preparations were comparable with those recorded from uninjured spinal cords. Physiological experiments made with raised concentrations of extracellular magnesium in the culture fluid indicated that growing axons had formed synaptic connections. Thus, delayed major peaks of the response were abolished while the small component corresponding to through conduction remained unaffected by magnesium. These experiments demonstrate the development of synaptic interactions by the growing neurites and confirm the far greater powers of repair in neonatal mammals compared to adults. They set the stage for comparing molecular mechanisms involved in development and regeneration of the mammalian CNS.
Drag and Lift on Running Insects
Authors: Full R. J. , Koehl M. A. R.
Published: April 2021

We examined the effects of aerodynamic forces on the mechanical power output of running insects for which kinematic data were available. Drag and lift on the cockroaches Periplaneta americana (a small, rapidly running species) and Blaberus discoidalis (a larger, more slowly moving species) were measured in a wind tunnel. Although lift would be expected to affect power output by altering functional body weight, the magnitude of the lift on these cockroaches was less than 2% of their weight. Drag, which increases the horizontal force that must be exerted to run at a given speed, accounted for 20–30% of the power output of P. americana running at speeds of 1.0–1.5 ms−1, but had a much smaller effect on B. discoidalis. Aerodynamic drag on the body (parasite drag) can significantly increase the mechanical power output necessary for small, rapidly running insects in contrast to larger running animals and to flying insects.
Water Flows Around the Comb Plates of the Ctenophore Pleurobrachia Plotted by Computer: A Model System for Studying Propulsion by Antiplectic Metachronism
Authors: Barlow David , Sleigh Michael A. , White Richard J.
Published: April 2021

Patterns of water flow around steadily beating comb plates of Pleurobrachia pileus were tracked using suspended plastic beads. The positions of the beads and the comb plates in the plane of the central longitudinal axis of the comb row were digitised from high-speed ciné films covering several beat cycles. All of the data from each sequence were combined using a computer program which integrated them into a standard cycle, and the resulting data were plotted by a second computer program to produce charts for different stages in the beat cycle showing the flow velocity at a grid of points. On these charts, contour maps were drawn to indicate the speed and direction of the water flow.

Water is drawn towards each comb row from ahead and from the sides and accelerates strongly backwards in a fairly narrow stream which joins those from the other seven comb rows at the rear of the animal. At a beat frequency of 10Hz the comb plates move with a tip speed of up to 70mm s−1 in their effective stroke; they have an estimated Reynolds number of 9 in this stroke. Changes in inter-plate volume between adjacent antiplectically coordinated plates are very important in propulsion, particularly near the end of the effective stroke when pairs of adjacent plates close together and cause the high-speed water from around the ciliary tips to be shed into the overlying stream as a series of jets at speeds of 50mms−1 or more. The antiplectic coordination of the comb plates makes a major contribution to the efficiency of propulsion.
Investigations of Lipid Components of Neurone-Enriched Membranes of the Jellyfish Cyanea Capillata
Authors: Schetz John A. , Anderson Peter A. V.
Published: April 2021

The lipid components of nerve-rich tissues from the jellyfish Cyanea capillata were purified by multiple differential extractions of a single tissue pellet and detected with various chemical spray reagents following separation by thin-layer chromatography. The results indicate that gangliosides are completely absent from Cyanea capillata neurones, that the major sterol is not cholesterol, and that the five major phosphorus-containing lipids do not co-migrate with conventional phospholipid standards. The atypical lipid environment of Cyanea capillata neurones may account for some of their unusual physiological and pharmacological properties.
The effect of ambient Ph on electrolyte regulation during the postmoult period in freshwater crayfish Procambarus clarkii
Authors: Zanotto Flavia P. , Wheatly Michele G.
Published: April 2021

The effects of ambient pH on postmoult net fluxes of Ca, acidic/basic equivalents (H+, NH4+/OH−, HCO3−), Na and Cl−, total body Ca, haemolymph pH and electrolyte status were assessed in the freshwater crayfish Procambarus clarkii (Girard). Variables were monitored for 5 days postmoult in acidic (pH5.2; H2SO4) or alkaline (pH9.2; KOH) artificial tap water (ATW) and compared with those in control (pH7.4) tap water. In control ATW there was an initial net influx of Ca (+2700 μmolkg−1 h−1) and titratable basic equivalents (+5000 μmolkg−1 h−1) that declined with time. Calcium uptake accounted for 40% of total body Ca (0.49mmol g−1); haemolymph Ca concentration remained constant. Haemolymph pH was initially relatively alkalotic (7.7) but recovered within 24h. A 20% haemolymph dilution by water uptake at ecdysis necessitated uptake of Cl− and Na for the first 2–3 days postmoult (+1000 μmolkg−1 h−). In acidic ATW, Ca and basic equivalent uptake were both 60% reduced during the first 3–4 days and total body Ca was reduced by 37%. Chloride and Na uptake and haemolymph [Cl−] were decreased. In alkaline ATW, Ca and basic equivalent uptake were elevated by 30% for the first 2 days and haemolymph alkalosis was maintained. Sodium and Cl−balance were unaffected. Thus, ambient pH affects Ca and basic equivalent fluxes associated with postmoult calcification. Regulation of Na and Cl−levels is also impaired in acidic ATW.
Contribution of the Na+/H+ Antiporter to the Regulation of Intracellular pH in a Crayfish Stretch Receptor Neurone
Authors: Mair N. , Moser H. , Fresser F.
Published: April 2021

Regulation of intracellular pH (pHi) following acidosis induced by NH4+/NH3 exposures was re-investigated in a crayfish stretch receptor neurone using H+- and Na+-selective microelectrodes. All experiments were performed in nominally HCO3−/CO2 -free salines. From studies in Na+-free saline and from electrochemical calculations, we concluded that pHi regulation was dependent on extracellular Na+ concentration ([Na+]o ). The half-maximal rate of pHi recovery had an apparent Michaelis–Menten constant of 21mmol l− 1 [Na+]o. The use of this experimental approach and an improved technique enabled us to observe pHi regulation even in Cl− -free saline, in contrast to earlier findings. In addition, amiloride (2mmol l− 1) inhibited the maximum rate of pHi recovery by about 80%, SITS (1mmol l− 1) by about 20%.

The results strongly suggest the operation of two separate pHi-regulating mechanisms, a Na+-dependent HCO3− /Cl− antiporter (probably the Na+/H+/HCO3− /Cl− antiporter described earlier) and a Na+/H+ antiporter. Both mechanisms have been described in crayfish ganglion cells and muscle fibres, but the individual contribution to pHi regulation varies considerably in these preparations. Functional aspects of the pHi-regulating mechanisms in relation to ionic changes during the moulting cycle are discussed.
Effect of Amino Acid Deprivation on L-Alanine Uptake Through the Asc System in Freshly Isolated Trout Hepatocytes
Authors: Canals P. , Gallardo M. A. , Sánchez J.
Published: April 2021

Fasting in mammals and other vertebrates induces an increase in the ability of liver to extract from blood gluconeogenic substrates, such as plasma amino acids, which can also be used as an energy source (Cowey et al. 1977; Newsholme and Leech, 1983). In mammalian hepatocytes, food deprivation induces the appearance of a high-affinity component for short-chain amino acid transport, with the properties of system A, while there are no changes in the activities of a low-affinity system (the ASC system), system L (Fehlmann et al. 1979) or glutamine uptake (Hayes and McGivan, 1982). ‘A’ is the abbreviation for a Na+-dependent carrier which has L-alanine and other short-chain neutral amino acids as preferred substrates. Its tolerance to N-methylated analogues differentiates it from the ASC system. ‘L’ is the abbreviation for a Na+-independent carrier which has L-leucine as preferred substrate. ‘asc’ is the abbreviation for a carrier similar to the ‘ASC’ carrier with respect to preferred substrates, but it is Na+-independent. The ASC system is a widely distributed, short-chain neutral amino acid carrier that transports alanine, serine, cysteine and threonine in a Na+-dependent mode, although the scope of its substrates is now thought to be wider than when it was first described in Erlich ascites tumour cells (Christensen et al. 1967). Characteristically, it does not accept N-methylated amino acid derivatives (allowing easy distinction from the A system).
The Mechanism of Flight Preparation in Some Insects
Authors: Krogh August , Zeuthen Erik
Published: April 2021

In 1928 Dotterweich published under the title “Beitrâge zur Nervenphysiologie der Insekten” some very interesting and important observations and measurements mainly on Sphingidae, showing that the rapid vibration of the wings regularly observed in large moths before they take flight produces an increase in temperature of the wing muscles which is necessary to enable them to fly at all. The temperature reached was nearly the same in all cases, 32-34° C., and the time taken to reach it varied with the initial temperature deficit, up to 6 min. with a deficit of 23°. Moths kept at 34° or above would fly off at once, without any preparation, when stimulated. It had been assumed by v. Buddenbrock that this preparation was mainly required to attain the high frequency of the wing movements necessary for actual flight, but a number of observations made by Dotterweich on butterflies (Vanessa), in which the normal frequency is much lower, made it very probable that in these also preparatory wing movements were responsible for a rise in temperature necessary for actual flight.
The Melanin Content of the Skin of Rana Temporaria Under Normal Conditions and after Prolonged Light- and Dark-Adaptation. A Photometric Study
Authors: Dawes Ben
Published: April 2021

Melanin has been extracted from dorsal and ventral components of the skin of English frogs by a simple method involving the leaching out of water-soluble pigments, the peptic digestion of washed skin, and the centrifugation of unaffected pigment. The melanin was estimated in NaOH solution with the aid of an indian-ink colour standard and by the use of a Duboscq colorimeter calibrated against suitable neutral density filters at various wave-lengths. Melanin varies greatly in amount in dorsal skins, some of which contain ten times as much of the pigment as others. In extreme duskiness and pallor, the difference may be fiftyfold. In spite of such variability, melanin formation seems generally to follow the usual laws of growth. Ventral pigmentation varies more than dorsal, ranging from an almost pigmentless condition to equality with dorsal pigmentation. The mean amount of melanin in ventral skin is about 27 % of that in dorsal skin. Melanin occurs in the skin of females at spawning time in large amount. Thus, the pale, red colour of the skin is not due to lack of the pigment. Melanin does not differ significantly in amount in the sexes. Melanin can be determined by careful visual judgement of the tone of the skin to within one-third of the total amount present in dark skin. The melanin content of dorsal skin is increased or decreased when frogs are kept for some weeks in equally illuminated light-absorbing (black) or lightscattering (white) surroundings. The skin of the dark-adapted animal contains 60 % more melanin than that of the light-adapted one after 5 weeks of treatment. The melanin content of the skin of a limb is increased under post-mortem conditions following intramuscular injection of post-pituitary extract into the freshly excised living limb. An increase of 27 % was determined. No effect is produced by adrenaline under these conditions. Prolonged adaptation to light-absorbing or light-scattering surroundings produces a more fundamental effect than the mere dispersion or aggregation of pre-existing melanin granules in the melanophores, namely, the production of fresh melanin or the degradation of this pigment. The subtractive process, which is evident microscopically, is due to some agent at present unknown. Frog melanin is shown by its absorption characteristics to be chemically very closely similar to, and possibly absolutely identical with, mammalian melanin and the pigment of melanoma.
The Structure and Conduction Velocity of the Medullated Nerve Fibres of Prawns
Authors: Holmes W. , Pumphrey R. J. , Young J. Z.
Published: April 2021

The structure of the myelinated fibres of prawns is described, and the homologies of the nucleated sheath which lies between the axon and the fatty layer discussed. The relative thickness of the myelin sheath increases with decrease in total diameter of the fibre along à curve similar in shape to that found in vertebrates and earthworms. Nodes of Ranvier are found in the sheaths of most fibres of a diameter greater than about 13µ. The nodes are similar to those in vertebrate nerves in that the myelin sheath is interrupted at the node. The conduction velocity of fibres in the central nervous system of axon diameter 26µ and total diameter 35µis between 18 and 23 m. per sec., a rate faster than is found in the “unmyelinated” fibres of similar size in other crustacea.
The Pigmentation of Cavernicolous Animals
Authors: Baldwin Ernest , Beatty R. A.
Published: April 2021

The widespread reduction of pigmentation found in cavernicolous animals is discussed. The externally visible coloration of Asellus aquaticus Linn., A. meridianas Rac., and A. aquaticus cavernicolas Rac., appears to be of the melanin type. The melanin content of A. aquaticus is not appreciably affected if this animal is kept in the dark for periods of several months. Offspring produced during this period are. normal in colour. Fertile young resulted from a cross between a colourless female A. aquaticus cavernicolus and a normally pigmented male A. aquaticus. This observation is probably of significance for the genetical analysis of the colour types found among the hypogean asellids. The predominant pigments of A. aquaticus, apart from melanin, are β-carotene and cryptoxanthine. Other carotenoid pigments are present only in traces.
The Influence of Various Physical and Biological Factors of the Environment on Honeybee Activity. An Examination of the Relationship Between Activity and Solar Radiation
Authors: Butler C. G. , Finney D. J.
Published: April 2021

A review of the literature shows that those who have studied the influence of solar radiation on honeybee activity are agreed that it is an important limiting factor. This is in general agreement with observations made by beekeepers.

Brittain et al. (1933) give a detailed account of the effects of solar radiation on honeybee activity, and claim that, as might be expected from the work of Bertholf (1931, 1931 a), a higher correlation between activity and the intensity of ultra-violet radiation exists than between activity and rádiation of clear light. However, fresh analysis of their data throws considerable doubt on their conclusions.

New data were collected which clearly show an association between variations in honeybee activity and the radiation of clear light.
What Ears Do For Bats: A Comparative Study Of Pinna Sound Pressure Transformation In Chiroptera
Authors: Obrist Martin K. , Fenton M. Brock , Eger Judith L. , Schlegel Peter A.
Published: April 2021

Using a moveable loudspeaker and an implanted microphone, we studied the sound pressure transformation of the external ears of 47 species of bats from 13 families. We compared pinna gain, directionality of hearing and interaural intensity differences (IID) in echolocating and non-echolocating bats, in species using different echolocation strategies and in species that depend upon prey-generated sounds to locate their targets. In the Pteropodidae, two echolocating species had slightly higher directionality than a non-echolocating species. The ears of phyllostomid and vespertilionid species showed moderate directionality. In the Mormoopidae, the ear directionality of Pteronotus parnellii clearly matched the dominant spectral component of its echolocation calls, unlike the situation in three other species. Species in the Emballonuridae, Molossidae, Rhinopomatidae and two vespertilionids that use narrow-band search-phase echolocation calls showed increasingly sharp tuning of the pinna to the main frequency of their signals. Similar tuning was most evident in Hipposideridae and Rhinolophidae, species specialized for flutter detection via Doppler-shifted echoes of high-duty-cycle narrow-band signals. The large pinnae of bats that use prey-generated sounds to find their targets supply high sound pressure gain at lower frequencies. Increasing domination of a narrow spectral band in echolocation is reflected in the passive acoustic properties of the external ears (sharper directionality). The importance of IIDs for lateralization and horizontal localization is discussed by comparing the behavioural directional performance of bats with their bioacoustical features.
The Effect of Serotonin (5-Hydroxytryptamine) on Glycolysis in the Perfused Ventricle of the Freshwater Bivalve Anodonta Cygnea: Evidence for Phosphorylation/Dephosphorylation Control of Phosphofructokinase
Authors: Michaelidis Basile , Rofalikou Evagelia , Beis Isidoros
Published: April 2021

The ventricles of the freshwater mollusc Anodonta cygnea were isolated and perfused with serotonin in order to examine its effect on glycolysis. Serotonin induces an increase in the concentration of glycolytic intermediates. Phosphofructokinase (PFK) preparations from ventricles perfused with serotonin exhibited an increased sensitivity to activation by the substrate fructose 6-phosphate (F6P) and to the activators AMP and fructose 2,6-bisphosphate (F2,6P2) and a reduced sensitivity to inhibition by ATP. In vitro phosphorylation/dephosphorylation experiments revealed that incubation of PFK preparations from ventricles perfused with normal saline in the presence of ATP, cyclic AMP and MgCl2 alters the degree of activation by F6P. In contrast, when enzyme preparations from ventricles treated with serotonin were incubated in the presence of alkaline phosphatase and MgCl2, PFK showed a reduced sensitivity to activation by F6P. Serotonin had no significant effect on the kinetic properties of PK, while it increased the proportion of the active a form of glycogen phosphorylase. These results indicate that serotonin induces an increase in the concentration of glycolytic intermediates in the ventricle of A. cygnea and that this is at least partly due to the activation of PFK, possibly via phosphorylation by an endogenous cyclic-AMP-dependent protein kinase.
Action of the Hypaxial Muscles During Walking and Swimming in the Salamander Dicamptodon Ensatus
Authors: Carrier David R.
Published: April 2021

Activity of the hypaxial muscles during walking and swimming was measured in the salamander Dicamptodon ensatus. During walking, there was activity on both sides of the trunk simultaneously. The obliquus externus superficialis and profundus muscles were active on the side towards which the trunk was bending (flexing), while the obliquus internus and transversalis muscles were active on the opposite side. In contrast, during swimming, all four of these muscles were active on the side of the trunk that was bending to become concave. These observations are consistent with the hypothesis that during terrestrial ambulation the obliquely oriented hypaxial muscles do not contribute to lateral bending of the trunk or to horizontal propulsion, but to stabilization of the trunk against long-axis torsion.
The Effects of SDRNFLRFamide and TNRNFLRFamide on the Motor Patterns of the Stomatogastric Ganglion of the Crab Cancer Borealis
Authors: Weimann James M. , Marder Eve , Evans Bruce , Calabrese Ronald L.
Published: April 2021

TNRNFLRFamide was isolated and sequenced from the stomatogastric nervous system of the crab Cancer borealis by reverse-phase high performance liquid chromatography followed by automated Edman degradation. An SDRNFLRFamide-like peptide that exactly co-migrated with SDRNFLRFamide was also observed. The effects of TNRNFLRFamide and SDRNFLRFamide on the gastric and pyloric rhythms of the stomatogastric nervous system of the crab Cancer borealis were studied. Both peptides activated pyloric rhythms in quiescent preparations in a dose-dependent manner with a threshold between 10 −11 and 10−10 mol l−1. Both peptides increased the pyloric rhythm frequency of preparations showing moderate activity levels and had relatively little effect on preparations that showed strong pyloric rhythms prior to peptide application. Both peptides evoked gastric mill activity in preparations without existing gastric rhythms. The activation of the gastric rhythm is associated with activation of oscillatory properties in the dorsal gastric neurone. The induction of gastric rhythms by these peptides was accompanied by switches from pyloric-timed activity to gastric-timed activity by several stomatogastric ganglion neurones. Application of these peptides provides direct experimental control of circuit modification in the stomatogastric nervous system.
Neuromuscular Organization in the Swimming System of the Pteropod Mollusc Clione Limacina
Authors: Satterlie Richard A.
Published: April 2021

Swim motor neurons of the pteropod mollusc Clione limacina were identified by a combination of electrophysiological and morphological characteristics. Two types of motor neurons were found, including small motor neurons which are active during both slow and fast swimming and which innervated restricted fields of the ipsilateral wing. General excitor motor neurons have large cell bodies, innervate widespread fields and are recruited into activity for fast swimming. Small motor neurons monosynaptically innervate slow-twitch muscle cells, whereas general excitors monosynaptically innervate both slow-twitch and fast-twitch muscle cells. Activity in general excitors can centrally enhance that in small motor neurons because the neurons are electrically coupled. Neuromuscular recordings and lesion experiments indicate that a peripheral nerve network does not appear to play an important role in the spread of excitation throughout the muscle fields.
Metabolic Control of Luminescence in Isolated Photophores of Porichthys: Effects of Glucose on Oxygen Consumption and Luminescence
Authors: Mallefet J. , Baguet F.
Published: April 2021

Basal oxygen consumption of isolated photophores from Porichthys sp. at rest, i.e. without light emission, increased significantly from 0.101±0.021nmolmin−1 to 0.173±0.016nmolmin−1 in response to the addition of 5.5mmol l−1 glucose. 5.5mmol l−1 glucose pretreatment modified the time course of the two phases of adrenaline-induced luminescence; an increase in oxygen consumption was observed during the fast phase of light production but a decrease occurred during the slow phase of luminescence. Pretreatment of isolated photophores with 5.5mmol l−1 glucose totally inhibited the light emission induced by 1mmol l-1 potassium cyanide. With this treatment, the respiration rate decreased progressively and after 40min reached a value not significantly different from zero. Even after blockage of cellular respiration by cyanide, an increase in the rate of oxygen consumption was observed during the fast adrenaline-induced luminescence. Glucose utilisation by glycolysis or by oxidative metabolism may provide energy to an inhibitory mechanism that maintains the photophores in a non-luminescent state. We suggest that the oxygen consumed during the fast phase of adrenaline luminescence could represent the activity of an extramitochondrial oxidative pathway involved in the light reaction.
Thoracic Connections Between Crayfish Giant Fibres and Motor Giant Neurones Reverse Abdominal Pattern
Authors: Heitler W. J. , Fraser K.
Published: April 2021

The escape tail-flip of the crayfish is ‘commanded’ by two bilaterally paired sets of giant fibre (GF) interneurones, the lateral giant (LG) and medial giant (MG) (see e.g. Wine, 1984, for a review). The two classes of GF respond to different stimuli and initiate tail-flips with different kinematic forms. An arousal stimulus applied to the front of the animal initiates a spike in the MG system, and this causes a tail-flip that drives the animal directly backwards, away from the stimulus. An arousal stimulus applied to the rear of the animal initiates a spike in the LG system, and this causes a tail-flip that drives the animal upwards and forwards, again moving it away from the stimulus. The major motor output path from the GFs is through monosynaptic rectifying electrical connections to a class of powerful trunk flexor motor neurones called the motor giant (MoG) neurones (Furshpan and Potter, 1959a). There is one MoG neurone in each hemisegment of the thorax and abdomen.
Vision in the Ctenid Spider Cupiennius Salei: Spectral Range and Absolute Sensitivity
Authors: Barth Friedrich G. , Nakagawa Takanao , Eguchi Eisuke
Published: April 2021

Electroretinograms were recorded from all eyes of the wandering spider Cupiennius salei (Ctenidae) and were found to be simple cornea-negative potential differences with amplitudes of up to 10mV. In both the principal eyes and all of the secondary eyes, the spectral response curves show a prominent green peak at 520 or 540nm and a shoulder in the ultraviolet between 340 and 380nm. The largest response in the ultraviolet measures between 65% and 80% of the green peak. Selective chromatic adaptation to either green or ultraviolet monochromatic light does not change these relative response levels and fails to indicate the presence of more than one spectral type of receptor. In the range 450–500nm, however, the Dartnall curve clearly deviates from the spectral sensitivity (SS) curve. Since the SS curves of all eyes have a small shoulder in the blue at 480nm, the existence of two or even three visual pigments is a possibility. Intensity curves were determined with white and monochromatic light. For white light, absolute corneal illuminance thresholds were clearly below 0.01lx. For monochromatic light stimuli, a corneal illuminance of approximately 3×1012 photonscm−2 s−1 is needed to elicit a half-maximal response. At threshold, the equivalent value is 3×109 photonscm−2 s−1, which corresponds to a retinal illuminance of 5.9×109 photonscm−2 s−1. Consequently, Cupiennius salei should be able to use its visual sense not only shortly after sundown but also under much poorer light conditions, such as those provided by moonlight. The log–linear response range of all eyes covers a stimulus intensity range of 4logunits. The sensitivity of the principal eyes increases by up to 0.81logunits at night as compared with daytime. The chromophore of the visual pigment of all eyes is 11-cis retinal.
The Effects of Altered Aquatic and Aerial Respiratory Gas Concentrations on Air-Breathing Patterns in a Primitive Fish (Amia Calva)
Authors: Hedrick Michael S. , Jones David R.
Published: April 2021

The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20–24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I air-breaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6±1.1 to 26.7±2.9mlkg−1 (95% confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80mlkg−1; the percentage of gas exchanged for type I breaths ranged from 14 to 33% of VB in normoxia.

Fish exposed to aquatic and aerial normoxia , or aerial hypercapnia in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75–92% of total breaths). When fish were exposed to 100% O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98% of total breaths).

Type I breaths appear to be under feedback control from O2-sensitive chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular ; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II air-breaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.
Positive Coupling of β-Like Adrenergic Receptors With Adenylate Cyclase In The Cnidarian Renilla Koellikeri
Authors: Awad Edward W. , Anctil Michel
Published: April 2021

Coupling of the previously characterized β1-and β2-like adrenoceptors in the sea pansy Renilla koellikeri with adenylate cyclase was examined in membrane preparations from this cnidarian. Adenylate cyclase activity was stimulated by several guanine nucleotides, such as GTP, Gpp(NH)p and GTPγS. Fluoride ions and cholera toxin greatly enhanced the enzyme activity, whereas forskolin had no effect on basal or isoproterenol-induced stimulation of the enzyme. The stimulation of adenylate cyclase activity by several β-adrenergic agonists in different parts of the animal reflected a positive coupling with the β2-and β1-like adrenoceptors in autozooid and peduncle tissues, respectively. In addition, isoproterenol-induced stimulation of adenylate cyclase activity was dependent on guanine nucleotides, suggesting coupling mediated by a G protein. The pharmacological profile of various antagonists on isoproterenol-sensitive adenylate cyclase in autozooid and peduncle tissues matched that of previous radioligand binding studies. Isoproterenol-induced stimulation of adenylate cyclase activity in rachidial tissues was partially inhibited by trifluoperazine or (±)CGP12177 and was completely blocked in the presence of both antagonists. This suggests that coupling of the enzyme occurs with β1-and β2-like adrenoceptors, both being present in the rachis. Serotonin and dopamine were also found to stimulate adenylate cyclase activity. Their stimulatory effect was additive to isoproterenol-induced activation, suggesting the presence of dopaminergic and serotonergic receptors in the tissues of the sea pansy. Along with the data presented previously on β-adrenergic binding, this study suggests that elements of receptor-dependent G protein signal transduction originated early in invertebrate evolution.