bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antagonistic frequency tuning of hair bundles by different chemoreceptors regulates nematocyst discharge
Authors: Watson Glen M. , Hessinger David A. 
Published: April 2021

ABSTRACT
Sea anemones capture prey by discharging nematocysts into them. Chemical and mechanical cues identify suitable prey to sensory receptor systems on the anemone. Conjugated N-acetylated sugars from prey bind to chemoreceptors on cnidocyte/supporting cell complexes to tune hair bundles on the complexes to lower frequencies matching prey movements. The hair bundles regulate discharge of microbasic p-mastigophore nematocysts into vibrating targets. Provided that proline receptors are activated after those for N-acetylated sugars, nematocyst discharge is tuned to much higher frequencies. Thus, anemone hair bundles are tuned to either higher or lower frequencies by antagonistic chemoreceptors. Chemoreceptors for proline can adapt to 10−8 mol l−1 proline and yet respond to increases in proline concentration of less than 10−15 mol l−1. Under these conditions, too few molecules of proline are added to activate chemoreceptors on all responding cnidocyte/supporting cell complexes. Evidence indicates that the extreme sensitivity of anemones to proline may be attributed, in part, to intercellular communication.
The swimming of unipolar cells of Spirillum volutans: Theory and observations
Authors: Ramia M. , Swan M. A. 
Published: April 2021

ABSTRACT
Bright-field high-speed cinemicrography was employed to record the swimming of six unipolar cells of Spirillum volutans. A complete set of geometrical parameters for each of these six cells, which are of typical but varying dimensions, was measured experimentally. For each cell, the mean swimming linear and angular speeds were measured for a period representing an exact number of flagellar cycles (at least four and up to 12 cycles). Two independent sets of measurements were carried out for each cell, one relating to the trailing and the other to the leading configuration of the flagellar bundle. The geometry of these cells was numerically modelled with curved isoparametric boundary elements (from the measured geometrical parameters), and an existing boundary element method (BEM) program was applied to predict the mean swimming linear and angular speeds. A direct comparison between the experimentally observed swimming speeds and those of the BEM predictions is made. For a typical cell, a direct comparison of the swimming trajectory, in each of the trailing and the leading flagellar configurations, was also included. Previous resistive force theory (RFT) as well as slender body theory (SBT) models are both restricted to somewhat non-realistic ‘slender body’ geometries, and they both fail to consider swimming kinematics. The present BEM model, however, is applicable to organisms with arbitrary geometry and correctly accounts for swimming kinematics; hence, it agrees better with experimental observations than do the previous models.
Mechanism of the net uptake of water in moulting blue crabs (Callinectes Sapidus) acclimated to high and low salinities
Authors: Neufeld Douglas S. , Cameron James N. 
Published: April 2021

ABSTRACT
Blue crabs (Callinectes sapidus Rathbun) acclimated to a salinity of 2 ‰ approximately doubled in wet mass (excluding carapace) during the period from 10 h before moult to 2 h after moult. Both in blue crabs acclimated to 2 ‰ salinity and in crabs acclimated to 28 ‰ salinity, the drinking rate increased from approximately 0.4 ml 100 g−1 h−1 at 1 day prior to moult to approximately 8 ml 100 g−1 h−1 during the first hour after moult. The drinking rate had decreased 1 day after moult in both salinities, but was significantly higher in crabs acclimated to high salinity (1.84±0.16 ml 100 g−1 h−1) than in crabs acclimated to low salinity (0.26±0.04 ml 100 g−1 h−1). Drinking accounted for two-thirds of the weight gain during the first hour after moult at both acclimation salinities, indicating that water enters the body at moult primarily through the gut rather than through the gills. [14C]polyethylene glycol, added as a tracer in the bath water, was concentrated in the midgut gland rather than in the stomach, implicating the midgut gland as the primary site of water absorption. The rate of water efflux was significantly greater in crabs acclimated to 30 ‰ salinity (66.4±9.0 ml 100 g−1 h−1) than in crabs acclimated to 2 ‰ salinity (34.0±4.7 ml 100 g−1 h−1). The osmotic uptake of water is equal at both salinities as a result of the decreased water permeability at low salinity. The rate of urine formation was estimated to be between 0.5 and 1 ml 100 g−1 h−1 during the first hour after moult in crabs acclimated to both low and high salinities, suggesting that the antennal gland plays a relatively small role in water regulation during this period.
Exercise in the terrestrial christmas island red crab Gecarcoidea Natalis: I. Blood gas transport
Authors: Adamczewska Agnieszka M. , Morris Stephen 
Published: April 2021

ABSTRACT
The respiratory and circulatory physiology of the terrestrial Christmas Island red crab Gecarcoidea natalis was investigated with respect to exercise in the context of its annual breeding migration. Red crabs were allowed to walk for predetermined periods of up to 45 min. During this exercise period, blood gas measurements were made on venous, pulmonary and arterial samples to assess the function of the lungs in gas exchange and the performance of the circulatory system in gas transport and to determine the role and importance of the haemocyanin.
The lungs of G. natalis were very efficient at O2 uptake, pulmonary blood being 80–90 % saturated throughout the 45 min exercise period. The maximum O2-carrying capacity was 1.1 mmol l−1, and haemocyanin (Hc) delivered 86 % of oxygen in resting crabs and 97 % during exercise. Oxygen delivery to the tissues was diffusion-limited during exercise. Indirect evidence, from the changes in haemolymph pH during transit through the lungs, suggested that the lung is the site of CO2 excretion. The Bohr shift was high at high pH (pH 7.8–7.5, φ.=-1.23) but decreased at low pH (pH 7.1–6.8, φ.=-0.48). The decreased Hc affinity for O2 during the exercise period facilitated O2 delivery to the tissues without impairing O2 loading at the lungs. The decrease in pH was sufficient to explain the change of affinity of Hc for O2 during the exercise period. The marked acidosis (0.8 pH unit decrease) was largely metabolic in origin, especially during sustained locomotion, but less than could be predicted from concomitant lactate production.
Exercise in the terrestrial christmas island red crab Gecarcoidea Natalis: II. Energetics of locomotion
Authors: Adamczewska Agnieszka M. , Morris Stephen 
Published: April 2021

ABSTRACT
The respiratory and circulatory physiology of exercising Christmas Island red crabs Gecarcoidea natalis were investigated with respect to their annual breeding migration. Red crabs were allowed to walk for up to 45 min. During this exercise period, the functioning of the circulatory system in gas transport and the energy status of the red crabs were quantified.
Energy production during exercise required both aerobic and anaerobic contributions. The aerobic scope of G. natalis was low, with only a doubling of the resting rate of oxygen consumption . Maximal O2 consumption was attained within the first 5 min of exercise and the level remained stable thereafter.
The anaerobic contribution to energy production was directly related to the speed of locomotion. L-lactate levels in blood and leg muscle were similar throughout the exercise period; blood lactate concentration was 33.39±2.29 mmol l−1 after 45 min of exercise. Heart rate in resting animals was 56±7 beats min−1. At the onset of exercise, heart rate also doubled, but without a significant increase in cardiac output. Increased O2 delivery was facilitated by increased extraction from the blood.
During the 45 min of exercise, glucose levels increased rapidly in the muscle tissue (from 2.30±0.54 to 8.78±1.20 mmol l−1) and subsequently in the blood (from 1.22±0.26 to 2.12±0.17 mmol l−1), fuelling increased glycolysis during locomotion. The energy production from stored glucose/glycogen was sufficient to support the energetic needs of locomotion, since the energy charge remained stable at 0.82.
Haemolymph L-lactate levels in crabs sampled in the field after migration were high compared with levels in many crustacean species but equivalent to L-lactate levels in laboratory animals exercised for less than 10 min. During their migration, therefore, the red crabs avoid exceptional L-lactate build-up in the blood by either walking very slowly or intermittently. However, G. natalis are exceptionally well adapted to cope with exhaustive locomotion and the resultant severe metabolic acidosis.
Use of a specialized magnetoreception system for homing by the eastern red-spotted newt Notophthalmus Viridescens
Authors: Phillips John B. , Borland S. Chris 
Published: April 2021

ABSTRACT
Laboratory experiments were carried out to investigate the effects of varying the wavelength of light on the use of an earth-strength magnetic field for shoreward orientation and for the compass component of homing. In the earlier shoreward orientation experiments, newts tested under full-spectrum and short-wavelength (i.e. 400 and 450 nm) light exhibited shoreward magnetic compass orientation. Under long-wavelength (i.e. 550 and 600 nm) light, newts exhibited magnetic compass orientation that was rotated 90 ° counterclockwise to the shoreward direction. This wavelength-dependent shift in magnetic compass orientation was shown to be due to a direct effect of light on the underlying magnetoreception mechanism. In homing experiments, newts tested under full-spectrum and short-wavelength light exhibited homeward magnetic compass orientation. Under long-wavelength light, newts were randomly distributed with respect to the magnetic field. The different effects of long-wavelength light on shoreward orientation and homing confirmed earlier evidence that different magnetoreception systems mediate these two forms of orientation behaviour. The properties of the newt’s homing response are consistent with the use of a hybrid magnetoreception system receiving inputs from the light-dependent magnetic compass and from a non-light-dependent intensity (or inclination) detector which, unlike the compass, is sensitive to the polarity of the magnetic field.
Acclimation of the threshold induction temperatures for 70-kDa and 90-kDa heat shock proteins in the fish Gillichthys mirabilis
Authors: Dietz Thomas J. 
Published: April 2021

ABSTRACT
The characteristic heat shock or stress response is induced upon exposure of an organism (cell) to a number of environmental stressors, e.g. heat, anoxia and heavy metals (reviewed in Morimoto et al. 1990; Ellis and van der Vies, 1991). The heat shock or stress proteins are the most broadly distributed class of proteins known and amongst the most highly conserved. These stress proteins and their cognates (non-stress-inducible forms of the proteins) play key roles in the proper folding, oligomerization, compartmentalization, translocation and activation of other cellular proteins. They have additionally been implicated in the process of acquired thermotolerance (Bosch et al. 1988; Mosser and Bols, 1988; McLennan and Miller, 1990; Sanchez and Lindquist, 1990) and in restoring aberrant proteins to their native state subsequent to thermal denaturation (Morimoto et al. 1990).
Allatotropin is a cardioacceleratory peptide in Manduca sexta
Authors: Veenstra Jan A. , Lehman Herman K. , Davis Norman T. 
Published: April 2021

ABSTRACT
Allatotropin is a neuropeptide that was originally isolated from the sphinx moth Manduca sexta, in which it stimulates the synthesis of juvenile hormone in adults (Kataoka et al. 1989). An antiserum raised against this peptide was characterized, shown to be specific for allatotropin and used in a competitive enzyme-linked immunosorbent assay (ELISA) to demonstrate that allatotropin is present not only in the brain and retrocerebral complex but also in the ventral nerve cord of Manduca sexta (Veenstra and Hagedorn, 1993). In the present study, allatotropin-immunoreactive neurons were located using the allatotropin antiserum in a whole-mount immunofluorescence method adapted from Davis et al. (1989). Several cell types were found to be immunoreactive, including three pairs of intensely staining median neurons in abdominal ganglia 3–6 of the pharate adult. The location of these median pairs of cells in each ganglion is anterior, mid-dorsal and posterio-ventral (Fig. 1A). The cells project bilaterally via the ventral nerves of each ganglion to the next transverse nerve (Fig. 2), where their axons terminate in numerous superficial varicosities (Fig. 1D). It is well established that the transverse nerve is a neurohemal organ in Lepidoptera (Provansal, 1972; Taghert and Truman, 1982; Tublitz and Truman, 1985a–d). The location and projection pattern of these three pairs of median neurons indicate that they belong to a group of abdominal median neurosecretory cells identified previously (Taghert and Truman, 1982; Tublitz and Truman, 1985a). Using the nomenclature of Davis et al. (1993), these are the M1, M2 and M5 neurosecretory cells. The M1 and M2 cells mature during adult development, but the M5 cells are already differentiated in the larval stages (Taghert and Truman, 1982; Tublitz and Truman, 1985a). The M5 cells of larvae were not stained by the allatotropin antiserum and only became immunoreactive, along with the M1 and M2 cells, during adult metamorphosis. Two pairs of the abdominal median neurosecretory cells were not allatotropin-immunoreactive: (1) the M3 cells, which are ventral and mature during adult metamorphosis (Taghert and Truman, 1982); and (2) the M4 cells, which are already differentiated in the larval stages (Tublitz and Truman, 1985a).
The position-dependent nature of postural resistance reflexes in the locust
Authors: Field L. H. , Coles M. M. L. 
Published: April 2021

ABSTRACT
The resistance reflexes of tibial extensor and flexor muscles, of all six legs in the locust, show changes in gain at different femur–tibia angles (FTA). In all muscles the gain is high for small angles (near full flexion) and low for large angles (near full extension, approximately 160 °). An exception occurs in the mesothoracic flexor muscle, which shows two modes: one as above and another in which maximum gain occurs at 100–120 ° FTA.
The position-dependent character is evident at each stage of the reflex pathway: motor neurone, non-spiking interneurone and femoral chordotonal organ (the afferent source of the reflex). We conclude that position-dependency originates from a decrease in the number of phasic femoral chordotonal organ neurones sensitive to joint movement as larger FTAs are approached.
Position-dependency is only roughly correlated with the postural FTAs most commonly observed in the meso- and metathoracic legs of unrestrained resting locusts; no such correlation was evident for prothoracic legs. We propose that the major role of position-dependency is to allow resistance reflexes efficiently to counter torque introduced onto the femur–tibia joint by perturbations in the horizontal plane when the insect rests on a horizontal substratum and in the vertical plane when it rests on a vertical substratum.
The use of stomach temperature records for the calculation of daily food intake in cormorants
Authors: Grémillet David J. H. , Plös Andrea L. 
Published: April 2021

ABSTRACT
We present a new method of measuring the food intake in cormorants based on stomach temperature recordings. Stomach temperature loggers were deployed both in captive and in free-living birds. We examine the accuracy of this method and compare it with the standard methods of evaluating food intake by pellet or stomach content analysis.
Comparison between thermoreceptor and mechanoreceptor currents in Paramecium caudatum
Authors: Tominaga Takashi , Naitoh Yutaka 
Published: April 2021

ABSTRACT
A voltage-clamped Paramecium produced an inward membrane current upon thermal or mechanical stimulation of its anterior region, whereas it produced an outward membrane current upon similar stimulation of its posterior region. Anterior thermo- and mechanoreceptor currents decreased when the membrane potential was shifted in a positive direction, showing sign reversal at a positive membrane potential, whereas posterior thermo- and mechanoreceptor currents decreased when the membrane potential was shifted in a negative direction, showing sign reversal at a membrane potential more negative than the resting potential. The reversal potential for both anterior receptor currents shifted in a positive direction when external [Ca2+] was increased, whereas those for both posterior receptor currents shifted in a positive direction when external [K+] was increased. External [Mg2+], [Mn2+], [Na+], [Rb+] and [TEA+] had similar effects on the thermo- and mechanoreceptor currents. Thermoreceptor currents decreased whereas mechanoreceptor currents increased as the ambient temperature was raised. When a mechanical stimulus was applied to the membrane where a thermoreceptor current was being produced, an algebraic summation of these receptor currents occurred. It is concluded that thermoreceptor currents are dependent on ion channels different from those responsible for the mechanoreceptor currents, although the ionic pores for the channels are similar to each other in various respects. A possibility that a thermoreceptor mechanism exclusively shares a Ca2+ pore in the anterior membrane, or a K+ pore in the posterior membrane, with a mechanoreceptor mechanism is discussed.
Urea production, acid–base regulation and their interactions in the lake magadi tilapia, a unique teleost adapted to a highly alkaline environment
Authors: Wood Chris M. , Bergman Harold L. , Laurent Pierre , Maina J. N. , Narahara Annie , Walsh Patrick J. 
Published: April 2021

ABSTRACT
The Lake Magadi tilapia, Oreochromis alcalicus grahami, thrives in highly alkaline geothermal springs and pools surrounding Lake Magadi, Kenya (control ), has a functional hepatic ornithine–urea cycle (OUC) and excretes all nitrogenous waste as urea-N at variable rates (JUrea) related to O2 consumption . The mean value of was high for fish but below the theoretical maximum (approximately 0.27) for 100 % aerobic respiration of protein, so an exogenous source of substrates is not required to explain the observed JUrea. JUrea was insensitive to thiourea. Urea excretion occurred largely (80 %) through the gills, but urea-N was also present in bile and urine. Control blood pHe, pHi and [HCO3−] (approximately 8.1, 7.6 and 15 mmol l−1, respectively, at approximately 32 °C) were extremely high. When fish were exposed to lake water titrated with HCl and aerated to remove CO2, N/O2 progressively declined. At a lake water pH of 7.05 and of 0 mmol l−1, N/O2 was reduced by 80 % and an intense metabolic acidosis occurred (pHe=7.04, [HCO3−]=1.5 mmol l−1). Restoration of control water pH 9.9 at a of 0 mmol l−1 resulted in intermediate levels of N/O2 and internal acid–base status. Additional experiments confirmed that urea production was inhibited by low pHe, was dependent on blood [HCO3−] with a Km of 3.06 mmol l−1 and was insensitive to acetazolamide. While metabolic acidosis clearly inhibited OUC ureagenesis, the system appeared to be saturated with HCO3− under control conditions so that additional basic equivalent loading would not stimulate ureagenesis. Urea production in the Lake Magadi tilapia does not appear to remove exogenous HCO3− or to play a role in normal acid–base regulation.
Kinematics of pectoral fin locomotion in the bluegill sunfish Lepomis macrochirus
Authors: Gibb Alice C. , Jayne Bruce C. , Lauder George V. 
Published: April 2021

ABSTRACT
The pectoral fins of ray-finned fishes are flexible and capable of complex movements, and yet little is known about the pattern of fin deformation during locomotion. For the most part, pectoral fins have been modeled as rigid plates. In order to examine the movements of different portions of pectoral fins, we quantified the kinematics of pectoral fin locomotion in the bluegill sunfish Lepomis macrochirus using several points on the distal fin edge and examined the effects of swimming speed on fin movements. We simultaneously videotaped the ventral and lateral views of pectoral fins of four fish swimming in a flow tank at five speeds ranging from 0.3 to 1.1 total lengths s−1. Four markers, placed on the distal edge of the fin, facilitated field-by-field analysis of kinematics. We used analyses of variance to test for significant variation with speed and among the different marker positions. Fin beat frequency increased significantly from 1.2 to 2.1 Hz as swimming speed increased from 0.3 to 1.0 total lengths s−1. Maximal velocities of movement for the tip of the fin during abduction and adduction generally increased significantly with increased swimming speed. The ratio of maximal speed of fin retraction to swimming speed declined steadily from 2.75 to 1.00 as swimming speed increased. Rather than the entire distal edge of the fin always moving synchronously, markers had phase lags as large as 32 °with respect to the dorsal edge of the fin. The more ventral and proximal portions of the fin edge usually had smaller amplitudes of movement than did the more dorsal and distal locations. With increased swimming speed, the amplitudes of the lateral and longitudinal fin movements generally decreased. We used two distal markers and one basal reference point to determine the orientation of various planar fin elements. During early adduction and most of abduction, these planar fin elements usually had positive angles of attack. Because of fin rotation, angles of attack calculated from three-dimensional data differed considerably from those estimated from a simple lateral projection. As swimming speed increased, the angles of attack of the planar fin elements with respect to the overall direction of swimming approached zero. The oscillatory movements of the pectoral fins of bluegill suggest that both lift- and drag-based propulsive mechanisms are used to generate forward thrust. In addition, the reduced frequency parameter calculated for the pectoral fin of Lepomis (&lt;Y=0.85) and the Reynolds number of 5×103 indicate that acceleration reaction forces may contribute significantly to thrust production and to the total force balance on the fin.
Control of cellular contraction by calcium in Vorticella
Authors: Katoh Kaoru , Naitoh Yutaka 
Published: April 2021

ABSTRACT
Vorticella extracted with Triton X-100 contracted (i.e. the cell body shrank and the stalk coiled) when the external Ca2+ concentration was raised. The degree of contraction increased with increasing Ca2+ concentration. The threshold Ca2+ concentration for shrinkage of the cell body was identical with that for coiling of the stalk in Vorticella extracted with Triton X-100. Living Vorticella showed a graded shrinkage of the cell body when Ca2+ buffer was injected into the cell body, while the stalk showed coiling of an all-or-nothing type. The degree of shrinkage of the cell body increased with increasing free Ca2+ concentration of the buffer. Living Vorticella showed a sustained contraction in response to external application or intracellular injection of caffeine. The effect of caffeine was inhibited by intracellular injection of procaine or Ruthenium Red. Vorticella injected with Ruthenium Red showed graded shrinkage of the cell body as well as graded coiling of the stalk when Ca2+ buffer was injected into the cell body. Caffeine, procaine and Ruthenium Red had no measurable effect on Ca2+-activated contraction in Vorticella extracted with Triton X-100. It is assumed that regenerative liberation of Ca2+ from the endoplasmic reticulum and/or membranous tubules in the contractile system (Ca2+-induced Ca2+ release) is responsible for evoking contraction of an all-or-nothing type following stimulation in living Vorticella.