bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematic scaling of locomotion by hydrostatic animals: ontogeny of peristaltic crawling by the earthworm Lumbricus terrestris
Authors: Quillin Kim J. 
Published: April 2021

ABSTRACT
This study examined the relationship between ontogenetic increase in body size and the kinematics of peristaltic locomotion by the earthworm Lumbricus terrestris, a soft-bodied organism supported by a hydrostatic skeleton. Whereas the motions of most vertebrates and arthropods are based primarily on the changes in the joint angles between rigid body segments, the motions of soft-bodied organisms with hydrostatic skeletons are based primarily on the changes in dimensions of the deformable body segments themselves. The overall kinematics of peristaltic crawling and the dynamic shape changes of individual earthworm segments were measured for individuals ranging in body mass (mb) by almost three orders of magnitude (0.012–8.5 g). Preferred crawling speed varied both within and among individuals: earthworms crawled faster primarily by taking longer strides, but also by taking more strides per unit time and by decreasing duty factor. On average, larger worms crawled at a greater absolute speed than smaller worms (U∝mb0.33) and did so by taking slightly longer strides (l∝mb0.41, where l is stride length) than expected by geometric similarity, using slightly lower stride frequencies (f∝mb−0.07) and the same duty factor (df∝mb−0.03). Circumferential and longitudinal body wall strains were generally independent of body mass, while strain rates changed little as a function of body mass. Given the extent of kinematic variation within and among earthworms, the crawling of earthworms of different sizes can be considered to show kinematic similarity when the kinematic variables are normalized by body length. Since the motions of peristaltic organisms are based primarily on changes in the dimensions of the deformable body wall, the scaling of the material properties of the body wall is probably an especially important determinant of the scaling of the kinematics of locomotion.
The linkage between Na+ uptake and ammonia excretion in rainbow trout: kinetic analysis, the effects of (NH4)2SO4 and NH4HCO3 infusion and the influence of gill boundary layer pH
Authors: Salama Annika , Morgan Ian J. , Wood Chris M. 
Published: April 2021

ABSTRACT
The nature of the linkage between between branchial ammonia excretion (JAmm) and unidirectional Na+ influx was studied in the freshwater rainbow trout (Oncorhynchus mykiss). Arterial plasma total [ammonia], PNH and JAmm were all elevated approximately threefold by intravascular infusion for 24 h with either 70 mmol l−1 (NH4)2SO4 or 140 mmol l−1 NH4HCO3 at a rate of approximately 400 μmol kg−1 h−1. Both treatments markedly stimulated . NH4HCO3 induced metabolic alkalosis in the blood plasma, whereas (NH4)2SO4 caused a slight metabolic acidosis. Experiments with Hepes-buffered water (5 mmol l−1) under control conditions demonstrated that increases in gill boundary layer pH were associated with decreases in both and JAmm. Thus, the stimulation of caused by ammonium loading was not simply a consequence of a Na+-coupled H+ extrusion mechanism activated by internal acidosis or by alkalosis in the gill boundary layer. Indeed, there was no stimulation of net acidic equivalent excretion accompanying NH4HCO3 infusion. Michaelis–Menten kinetic analysis by acute variation of water [Na+ ] demonstrated that both infusions caused an almost twofold increase in but no significant change in Km, indicative of an increase in transporter number or internal counterion availability without an alteration in transporter affinity for external Na + . The increase in was larger with (NH4)2SO4 than with NH4HCO3 infusion and in both cases lower than the increase in JAmm. Additional evidence of quantitative uncoupling was seen in the kinetics experiments, in which acute changes in of up to threefold had negligible effects on JAmm under either control or ammonium-loaded conditions. In vitro measurements of branchial Na + /K +-ATPase activity demonstrated no effect of NH4+ concentration over the concentration range observed in vivo in infused fish. Overall, these results are consistent with a dominant role for NH3 diffusion as the normal mechanism of ammonia excretion, but indicate that ammonium loading directly stimulates , perhaps by activation of a non-obligatory Na+/NH4+ exchange rather than by an indirect effect (e.g. Na +-coupled H+ excretion) mediated by altered internal or external acid–base status.
Tegula function during free locust flight in relation to motor pattern, flight speed and aerodynamic output
Authors: Fischer Hanno , Ebert Eckhard 
Published: April 2021

ABSTRACT
Tegulae are complex proprioceptors at the wing base of locusts. Deafferentation of the tegulae causes a lack of specific phasic information related to the wing downstroke and the timing of the upstroke. Employing telemetry during free flight of the locust Schistocerca gregaria, we investigated the consequences of tegula ablation on free flight parameters including motor patterns (wingbeat frequency and the relationship between the activation of flight muscle antagonists), free flight speed and aerodynamic output. We investigated the role of the tegula pairs of both wings on the motor pattern generated in free-flying locusts. We show that the tegula organs are not essential for generating the motor patterns necessary for free flight. However, they are required for increasing the motor output to give additional effective lifting power during adaptive behaviour. We also investigated long-term changes in the free flight parameters after tegula ablation. The recovery of the adult flight system revealed in the present study suggests that there is adaptation to the loss of proprioceptive information; this argues for a full functional and behavioural recovery of the flight system of the locust under closed-loop conditions.
Transformation of leech microglial cell morphology and properties following co-culture with injured central nervous system tissue
Authors: Bernhardi Rommy Von , Nicholls John G. 
Published: April 2021

ABSTRACT
When the leech central nervous system (CNS) is injured, microglial cells migrate to the site of the lesion. It is possible that the injured CNS releases diffusible substances that alter the properties of microglial cells; to investigate this, microglial cells were cultured in the presence of injured or uninjured CNS tissue. Grown on Concanavalin A (Con-A), 75 % of microglial cells are rounded in shape and are avoided by growing neurites. However, when chains of leech ganglia with damaged connectives were cultured on Con-A next to microglial cells, many of the microglial cells changed their morphology. The number of rounded cells present decreased to 48 %, 4 % became spindle-shaped and 48 % had an intermediate form. In addition, the presence of crushed ganglionic chains allowed more growth of neurites across microglial cells than occurred under control conditions, although round-shaped microglia were still avoided by growing neurites. Similar changes in microglial cells were produced in cells plated on Con-A in the presence of conditioned medium from crushed ganglionic chains. Hence, a diffusible substance from injured CNS tissue caused the morphology of the microglial cells plated on Con-A to become more like that of microglia plated on laminin, on which only 22 % of the cells are rounded while the remainder are spindle-shaped and are readily crossed by neurites. Changes in morphology were not observed when microglial cells were cultured with frozen and crushed ganglionic chains or with uncrushed chains. These experiments demonstrate that substances released from damaged leech CNS cause microglial cells plated on Con-A to change their morphology and the way in which they interact with growing neurites.
Dopamine stimulates salivary duct cells in the cockroach Periplaneta americana
Authors: Lang Ingo , Walz Bernd 
Published: April 2021

ABSTRACT
This study examines whether the salivary duct cells of the cockroach Periplaneta americana can be stimulated by the neurotransmitters dopamine and serotonin. We have carried out digital Ca2+-imaging experiments using the Ca2+-sensitive dye fura-2 and conventional intracellular recordings from isolated salivary glands. Dopamine evokes a slow, almost tonic, and reversible dose-dependent elevation in [Ca2+]i in the duct cells. Upon stimulation with 10−6 mol l−1 dopamine, [Ca2+]i rises from 48±4 nmol l−1 to 311±43 nmol l−1 (mean ± S.E.M., N=18) within 200–300 s. The dopamine-induced elevation in [Ca2+]i is absent in Ca2+-free saline and is blocked by 10−4 mol l−1 La3+, indicating that dopamine induces an influx of Ca2+ across the basolateral membrane of the duct cells. Stimulation with 10−6 mol l−1 dopamine causes the basolateral membrane to depolarize from −67±1 to −41±2 mV (N=10). This depolarization is also blocked by La3+ and is abolished when Na+ in the bath solution is reduced to 10 mmol l−1. Serotonin affects neither [Ca2+]i nor the basolateral membrane potential of the duct cells. These data indicate that the neurotransmitter dopamine, which has previously been shown to stimulate fluid secretion from the glands, also stimulates the salivary duct cells, suggesting that dopamine controls their most probable function, the modification of primary saliva.
Post-ingestive feedbacks and associative learning regulate the intake of unsuitable sterols in a generalist grasshopper
Authors: Behmer Spencer T. , Elias Damian O. , Bernays Elizabeth A. 
Published: April 2021

ABSTRACT
Behavioural studies of the grasshopper Schistocerca americana were undertaken to identify the mechanisms that regulate the intake of dietary sterols. In the first experiment, grasshoppers were allowed to feed on spinach, a plant containing only unsuitable sterols; immediately after this first meal, a suitable or unsuitable sterol was injected into the haemolymph. Grasshoppers injected with unsuitable sterols had second meals on spinach that were significantly shorter than those of grasshoppers injected with suitable sterols, indicating that unsuitable dietary sterols are detected post-ingestively. In the second experiment, grasshoppers were fed food containing only unsuitable sterols and were then presented with glass-fibre discs containing different concentrations of a suitable sterol or sucrose only (the control). The results suggest that grasshoppers do not use a direct feedback operating on mouthpart chemoreceptors to regulate their intake of suitable sterols. In the third experiment, grasshoppers were presented with artificial diets containing different sterols and flavours, and feeding was observed over a sequence of meals. The results from both the first and last experiments suggest a role for associative learning in regulating the intake of unsuitable sterols.
Does Gill Boundary Layer Carbonic Anhydrase Contribute to Carbon Dioxide Excretion: a Comparison Between Dogfish (Squalus Acanthias) and Rainbow Trout (Oncorhynchus Mykiss)
Authors: Perry S. F. , Gilmour K. M. , Bernier N. J. , Wood C. M. 
Published: April 2021

ABSTRACT
In vivo experiments were conducted on spiny dogfish (Squalus acanthias) and rainbow trout (Oncorhynchus mykiss) in sea water to determine the potential role of externally oriented or gill boundary layer carbonic anhydrase in carbon dioxide excretion. This was accomplished by assessing pH changes in expired water using a stopped-flow apparatus. In dogfish, expired water was in acid–base disequilibrium as indicated by a pronounced acidification (ΔpH=−0.11±0.01; N=22; mean ± S.E.M.) during the period of stopped flow; inspired water, however, was in acid–base equilibrium (ΔpH=−0.002±0.01; N=22). The acid–base disequilibrium in expired water was abolished (ΔpH=−0.005±0.01; N=6) by the addition of bovine carbonic anhydrase (5 mg l−1) to the external medium. Addition of the carbonic anhydrase inhibitor acetazolamide (1 mmol l−1) to the water significantly reduced the magnitude of the pH disequilibrium (from −0.133±0.03 to −0.063±0.02; N=4). However, after correcting for the increased buffering capacity of the water caused by acetazolamide, the acid–base disequilibrium during stopped flow was unaffected by this treatment (control Δ[H+]=99.8±22.8 μmol l−1; acetazolamide Δ[H+]=81.3±21.5 μmol l−1). In rainbow trout, expired water displayed an acid–base disequilibrium (ΔpH=0.09±0.01; N=6) that also was abolished by the application of external carbonic anhydrase (ΔpH=0.02±0.01).
The origin of the expired water acid–base disequilibrium was investigated further in dogfish. Intravascular injection of acetazolamide (40 mg kg−1) to inhibit internal carbonic anhydrase activity non-specifically and thus CO2 excretion significantly diminished the extent of the expired water disequilibrium pH after 30 min (from −0.123±0.01 to −0.065±0.01; N=6). Selective inhibition of extracellular carbonic anhydrase activity using a low intravascular dose (1.3 mg kg−1) of the inhibitor benzolamide caused a significant reduction in the acid–base disequilibrium after 5 min (from −0.11±0.01 to −0.07±0.01; N=14). These results demonstrate that the expired water acid–base disequilibrium originates, at least in part, from excretory CO2 and that extracellular carbonic anhydrase in dogfish may have a significant role in carbon dioxide excretion. However, externally oriented carbonic anhydrase (if present in dogfish) plays no role in catalysing the hydration of the excretory CO2 in water flowing over the gills and thus is unlikely to facilitate CO2 excretion.
Morphology and mechanics of tongue movement in the african pig-nosed frog Hemisus marmoratum: a muscular hydrostatic model
Authors: Nishikawa Kiisa C. , Kier William M. , Smith Kathleen K. 
Published: April 2021

ABSTRACT
The goal of this study was to investigate morphological adaptations associated with hydrostatic elongation of the tongue during feeding in the African pig-nosed frog Hemisus marmoratum. Whereas previous studies had suggested that the tongue of H. marmoratum elongates hydraulically, the anatomical observations reported here favour a muscular hydrostatic mechanism of tongue elongation. H. marmoratum possesses a previously undescribed compartment of the m. genioglossus (m. genioglossus dorsoventralis), which is intrinsic to the tongue and whose muscle fibres are oriented perpendicular to the long axis of the tongue. On the basis of the arrangement and orientation of muscle fibres in the m. genioglossus and m. hyoglossus, we propose a muscular hydrostatic model of tongue movement in which contraction of the m. genioglossus dorsoventralis, together with unfolding of the intrinsic musculature of the tongue, results in a doubling in tongue length. Electron micrographs of sarcomeres from resting and elongated tongues show that no special adaptations of the sarcomeres are necessary to accommodate the observed doubling in tongue length during feeding. Rather, the sarcomeres of the m. genioglossus longitudinalis are strikingly similar to those of anuran limb muscles. The ability to elongate the tongue hydrostatically, conferred by the presence of the m. genioglossus dorsoventralis, is associated with the appearance of several novel aspects of feeding behaviour in H. marmoratum. These include the ability to protract the tongue slowly, thereby increasing capture success, and the ability to aim the tongue in azimuth and elevation relative to the head. Compared with other frogs, the muscular hydrostatic system of H. marmoratum allows more precise, localized and diverse tongue movements. This may explain why the m. genioglossus of H. marmoratum is composed of a larger number of motor units than that of other frogs.
Respecified larval proleg and body wall muscles circulate hemolymph in developing wings of Manduca sexta pupae
Authors: Lubischer Jane L. , Verhegge Laura D. , Weeks Janis C. 
Published: April 2021

ABSTRACT
Most larval external muscles in Manduca sexta degenerate at pupation, with the exception of the accessory planta retractor muscles (APRMs) in proleg-bearing abdominal segment 3 and their homologs in non-proleg-bearing abdominal segment 2. In pupae, these APRMs exhibit a rhythmic ‘pupal motor pattern’ in which all four muscles contract synchronously at approximately 4 s intervals for long bouts, without externally visible movements. On the basis of indirect evidence, it was proposed previously that APRM contractions during the pupal motor pattern circulate hemolymph in the developing wings and legs. This hypothesis was tested in the present study by making simultaneous electromyographic recordings of APRM activity and contact thermographic recordings of hemolymph flow in pupal wings. APRM contractions and hemolymph flow were strictly correlated during the pupal motor pattern. The proposed circulatory mechanism was further supported by the findings that unilateral ablation of APRMs or mechanical uncoupling of the wings from the abdomen essentially abolished wing hemolymph flow on the manipulated side of the body. Rhythmic contractions of intersegmental muscles, which sometimes accompany the pupal motor pattern, had a negligible effect on hemolymph flow. The conversion of larval proleg and body wall muscles to a circulatory function in pupae represents a particularly dramatic example of functional respecification during metamorphosis.
Purification and cloning of the salivary peroxidase/catechol oxidase of the mosquito Anopheles albimanus
Authors: Ribeiro José M. C. , Valenzuela Jesus G. 
Published: April 2021

ABSTRACT
Salivary homogenates of the adult female mosquito Anopheles albimanus have been shown previously to contain a vasodilatory activity associated with a catechol oxidase/peroxidase activity. We have now purified the salivary peroxidase using high-performance liquid chromatography. The pure enzyme is able to relax rabbit aortic rings pre-constricted with norepinephrine. The peroxidase has a relative molecular mass of 66 907 as estimated by mass spectrometry. Amino-terminal sequencing allowed us to design oligonucleotide probes for isolation of cDNA clones derived from the salivary gland mRNA from female mosquitoes. The full sequence of the cDNA demonstrated homology between A. albimanus salivary peroxidase and several members of the myeloperoxidase gene family. A close comparison of A. albimanus salivary peroxidase with canine myeloperoxidase, for which the crystal structure is known, showed that all six disulfide bridges were conserved and demonstrated identity for all five residues associated with a Ca2+-binding site. In addition, 16 of 26 residues shown to be in close proximity to the heme moiety in the canine myeloperoxidase were identical. We conclude that the salivary peroxidase of A. albimanus belongs to the myeloperoxidase gene family. Other possible functions for this molecule in blood feeding are discussed.
Changes in motor network expression related to moulting behaviour in lobster: role of moult-induced deep hypoxia
Authors: Clemens Stefan , Massabuau Jean-Charles , Meyrand Pierre , Simmers John 
Published: April 2021

ABSTRACT
The well known rhythmically active pyloric neural network in intact and freely behaving lobsters Homarus gammarus was monitored prior to and following ecdysis. Despite long-lasting hormonal and metabolic alterations associated with this process, spontaneous pyloric network activity remained largely unaltered until the last 12–48 h before exuviation. At this time, the most notable change was a progressive lengthening of pyloric cycle period, which eventually attained 500–600 % of control values. It was only in the very last minutes before ecdysis that burst patterning became irregular and the otherwise strictly alternating motor sequence broke down. After the moult, coordinated rhythmicity was re-established within 10 min. Concomitant with these final changes in motor network expression at ecdysis was a drastic reduction in blood oxygen levels which led to a temporary near-anoxia. By imposing similarly deep hypoxic conditions both on intermoult animals and on the pyloric network in vitro, we mimicked to a large extent the moult-induced changes in pyloric network performance. Our data suggest that, despite major surrounding physiological perturbations, the pyloric network in vivo retains stable pattern-generating properties throughout much of the moulting process. Moreover, some of the most significant modifications in motor expression just prior to ecdysis can be related to a substantial reduction in oxygen levels in the blood.
Urine release in freely moving catheterised lobsters (Homarus americanus) with reference to feeding and social activities
Authors: Breithaupt Thomas , Lindstrom Daniel P. , Atema Jelle 
Published: April 2021

ABSTRACT
Previous studies suggest that urine-borne pheromones play an important role in lobster agonistic and sexual behaviour. This paper investigates the pattern of urine release in catheterised, but otherwise freely moving, adult lobsters with respect to feeding, social and non-social activities. Lobsters on average released 4.1 ml (1 % of body mass) of urine over a 12 h period; this more than doubled to 10.6 ml over the 12 h period after feeding. Hourly monitoring revealed that most urine was released in the first hour after feeding (2.84 ml). With the exception of the first hours after feeding, urine release was intermittent, with pauses lasting up to 17 h. The probability of urine release per hour in unfed lobsters was 0.34 (median); this value increased during agonistic interactions elicited by the introduction of a conspecific (median 0.63) and during activity initiated by non-social disturbance (median 0.56). Mean urine volume during output hours in unfed lobsters amounted to 1.09 ml h−1. This volume was significantly increased by the presence of a conspecific (1.88 ml h−1) and decreased during activity initiated by non-social disturbances (0.56 ml h−1). No sex-specific differences in urine release were found. The data demonstrate that lobsters control their urine release in a manner dependent on behavioural context. This supports recent findings suggesting the use of urine for chemical signalling in agonistic interactions.
The case for light-dependent magnetic orientation in animals
Authors: Deutschlander Mark E. , Phillips John B. , Borland S. Chris 
Published: April 2021

ABSTRACT
Light-dependent models of magnetoreception have been proposed which involve an interaction between the magnetic field and either magnetite particles located within a photoreceptor or excited states of photopigment molecules. Consistent with a photoreceptor-based magnetic compass mechanism, magnetic orientation responses in salamanders, flies and birds have been shown to be affected by the wavelength of light. In birds and flies, it is unclear whether the effects of light on magnetic orientation are due to a direct effect on a magnetoreception system or to a nonspecific (e.g. motivational) effect of light on orientation behavior. Evidence from shoreward-orienting salamanders, however, demonstrates that salamanders perceive a 90° counterclockwise shift in the direction of the magnetic field under long-wavelength (⩾500 nm) light. A simple physiological model based on the antagonistic interaction between two magnetically sensitive spectral mechanisms suggests one possible way in which the wavelength-dependent effects of light on the salamander’s magnetic compass response might arise. Assuming that the wavelength-dependent characteristics of the avian magnetic response can be attributed to an underlying magnetoreception system, we discuss several hypotheses attempting to resolve the differences observed in the wavelength-dependent effects of light on magnetic orientation in birds and salamanders. By considering the evidence in the context of photoreceptor- and non-photoreceptor-based mechanisms for magnetoreception, we hope to encourage future studies designed to distinguish between alternative hypotheses concerning the influence of light on magnetoreception.