bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respiratory Cost of Swimming in Larval and Juvenile Cyprinids
Authors: Kaufmann Ruediger 
Published: April 2021

ABSTRACTThe relationship between swimming speed and respiration rate for larvae and juveniles (1.5–600 mg fresh mass) of two cyprinid species, Chalcalburnus chalcoides and Rutilus rutilus, was measured in a flow-tunnel at 20°C.A special tunnel respirometer with small volume and fast response had to be constructed to cope with the methodological difficulties encountered with the larvae. The oxygen uptake increased quadratically with swimming speed if the oxygen debt incurred at the highest speeds was included in the calculations. The maximum speeds sustainable over 2 min were 6–8 lengths s−1; the critical speed marking the onset of anaerobic processes was only 10–15 % lower. Energetics and performance were similar for both species. The cost of transport was much higher for larvae and juveniles than for adult fish and decreased rapidly during growth. Standard and routine metabolic rates scaled with an allometry of M−0.23, active rates with M−015, where M is body mass in grams. In the smallest larvae, however, the standard rates were nearly independent of body mass. Their active rates of 80μmol O2h−1g−1 fresh mass were twice as high as those of adults. The scope for activity was high on an absolute scale, but not when expressed as factorial scope, since the standard rate was also high. For the same reason, routine activity accounted for less than 25 % of the energy budget, despite the high cost of transport. The data are discussed with respect to the changing swimming pattern during ontogeny, the shift from cutaneous to branchial respiration and the metabolic processes involved.
Ion Transport Across the Midgut of the Tobacco Hornworm (Manduca Sexta)
Authors: Chamberlin M. E. 
Published: April 2021

ABSTRACTThe transport of K+, Na+ and Cl− across the three morphologically distinct regions of the tobacco hornworm midgut was measured under open-circuit and short-circuit conditions. Using a saline which contained physiological levels of haemolymph ions, amino acids and sugars, it was shown that all three sections actively secrete K+ and Cl− and absorb Na+. The anterior section maintained the highest short-circuit current (Isc), transepithelial potential difference (PD) and net K+ secretion. The middle section had the lowest Isc, PD and K+ secretion, but absorbed Na+ at the greatest rate. The posterior section had the greatest rate of Cl− secretion. Omission of K+ depressed the Isc, Subsequent addition of K+ stimulated the Isc to control levels in the middle and posterior sections, but not in the anterior section. Omission of Cl− or Na+ also inhibited the Isc. Reintroduction of Cl− had no stimulatory effect and, although reintroduction of Na+ stimulated the Isc, control levels were not attained. Unlike the results reported in previous studies, the net K+ transport exceeded the Ix in all three midgut sections. The deficit in was not made up by the transport of Na+ and Cl−. The results are discussed with respect to proposed models of ion transport across this epithelium.
Short Communication: Luminal Alkalinization by the Isolated Midgut of the Tobacco Hornworm (Manduca Sexta)
Authors: Chamberlin M. E. 
Published: April 2021

ABSTRACTThe midgut contents of lepidopteran larvae are often several pH units more basic than the haemolymph (Berenbaum, 1980). One species, Manduca sexta, maintains a luminal pH of 11.3 (Dow, 1984) while the haemolymph has a pH of 6.7-6.8 (Dow, 1984; Dow et al. 1984). The midgut of M. sexta is divided into three morphologically distinct regions (Cioffi, 1979), and Dow (1984) has shown that the luminal pH is greatest in the anterior and middle sections of the midgut. The posterior midgut lumen, while still more basic than the haemolymph, has a pH lower than the middle and anterior sections. Whereas these results suggest that alkaline secretion may differ along the length of the midgut, no direct measurements of alkaline secretion have been made. In this study the rate of luminal alkalinization in the three midgut sections was measured in vitro.
Activity Patterns of Inhibitory Motoneurones and their Impact on Leg Movement in Tethered Walking Locusts
Authors: Wolf Harald 
Published: April 2021

ABSTRACTA preparation is described which permits intracellular recording of neural activity in tethered walking locusts. Minimal dissection is required, leaving the animal nearly intact.In this preparation, the activities of the three common inhibitory motoneurones (CIs) supplying the muscles of the middle leg were recorded. CIs were completely or almost completely silent in quiescent locusts but often produced a tonic spike discharge during walking activity. This tonic discharge was modulated in the step cycle, bursts of action potentials being generated in conjunction with the swing phase of the leg movement. The bursts peaked at around the start of leg protraction. They were remarkably similar in all three CIs and in a variety of different walking situations (forward and backward walking, searching, etc.). The only notable difference was that bursts of CI1 normally peaked some 40 ms before those of CI2. These results indicate that CI activity is timed according to the muscle group innervated but that no further functional specializations exist.Activity of CI1 was manipulated by current injection. For example, decreasing CI spike discharge by the application of hyperpolarizing current reduced the velocity of leg protraction in the walking animal. This demonstrates that CI1 plays an important role in determining the speed of the swing movement.
Control of Locomotion in the Freshwater SnailPlanorbis Corneus: II. Differential Control of Various Zones of the Ciliated Epithelium
Authors: Deliagina T. G. , Orlovsky G. N. 
Published: April 2021

ABSTRACTIn the freshwater snail Planorbis corneus, the neuronal mechanisms of the pedal ganglia that control ciliary locomotion were studied. The foot was attached to the bottom of a recording chamber with the ciliated epithelium facing upwards. To record the total motor effect produced by ciliary beating, a small disk with its edge lying on the sole of the foot was used. The ciliary beating forced the disk to rotate.In the pedal ganglia, efferent locomotor neurones (ELNs) were found, which control the locomotor activity of the ciliated epithelium. This locomotor activity increased with excitation of an ELN, and decreased with its inhibition. Axons of the ELNs, controlling the anterior, middle and posterior zones, traverse the corresponding pedal nerves. For the anterior zone, two ELNs were found. For the middle and posterior zones, only one ELN per zone was found. The activity of ELNs correlated with the intensity of ciliary beating during the following central and reflex influences upon the locomotor mechanisms: (1) spontaneous fluctuations of the locomotor activity, (2) changes of temperature, (3) transections of central connections (interganglionic connectives), (4) defensive reactions evoked by tactile stimuli or switching off the light, and (5) activation of feeding behaviour by natural stimuli. The data strongly suggest that ELNs are responsible for the differential control of locomotor activity in various zones of the ciliated epithelium during different behavioural acts.
Ultrasound-Triggered, Flight-Gated Evasive Maneuvers in the Praying MantisParasphendale Agrionina: II. Tethered Flight
Authors: Yager David D. , May Michael L. 
Published: April 2021

ABSTRACTIn tethered flight, Parasphendale agrionina (Gerst.) males respond to ultrasonic stimuli with a unique suite of behaviors that includes full extension of the forelegs, strong dorsiflexion of the abdomen, a head roll, a 5% decrease in wingbeat frequency and a 33% increase in forewing excursion. Latency for the foreleg extension averages 66 ms while the latency to onset of yaw is 174 ms. The direction of the turn is unrelated to the location of the speaker. Yaw magnitude and latency are only weakly related to sound pressure level, and variability in these and other parameters is high. The behavior shows moderately sharp tuning to 40–60 kHz with a lowest mean threshold of 60 dB SPL. A male will not respond to ultrasound unless in flight, and the context-gating is independent of sensory input from the tarsi. Several components of the in-flight evasive behavior resemble defensive displays on the ground, and we suggest that this mantis has responded to predation pressure from bats with both flight-derived maneuvers and an aerial deimatic display.
Magnesium Transport in Fish Intestine
Authors: Van Der Velden J. A. , Groot J. A. , Flik G. , Polak P. , Kolar Z. I. 
Published: April 2021

ABSTRACT
Literature on the mechanisms of magnesium transport through fish intestine is scarce. Indirect evidence for a net magnesium transport via the intestinal tract of fish has been established by dietary experiments (e.g. with carp Cyprinus carpio L. and nile perch Oreochromis niloticus Peters), showing that dietary magnesium is essential for the growth of these fish (Ogino and Chiou, 1976; Dabrowska et al. 1989). Nakamura and Hirano (1986) suggested ‘solvent drag’ as a mechanism for net magnesium transport in eel Anguilla japonica intestine. For mammals, the reports on this topic are equivocal. In the small intestine of the rat, diffusion (Ross, 1962; Aldor and Moore, 1970; O’Donnell and Smith, 1973) as well as solvent drag (Behar, 1974) were reported to underlie magnesium absorption, although the possibility of an active transport component was kept open by these authors. For the intestine of guinea pig, active transport of magnesium was demonstrated (Ross and Care, 1962; Partridge et al. 1987). This communication deals with magnesium transport across stripped intestinal epithelium of freshwater tilapia and its possible mechanisms.
Adhesion and Detachment of the Toe Pads of Tree Frogs
Authors: Hanna Gavin , Barnes W. Jon P. 
Published: April 2021

ABSTRACTThe mechanisms by which the toe pads of tree frogs adhere to and detach from surfaces during climbing have been studied in Osteopilus septentrionalis and other tree frogs using a variety of techniques.The experiments on attachment lend general support to the theory that toe pads stick by wet adhesion. First, the presence of a meniscus surrounding the area of contact shows that pad and surface are connected by a fluid-filled joint. Second, experiments on single toe pads of anaesthetised frogs demonstrate that the pads exhibit the velocity-dependent resistance to shear forces expected of any system employing a fluid as an adhesive mechanism. Third, the largest adhesive forces that toe pads can generate (approx. 1.2mNmm−2, calculated from data on sticking ability) are within the range that can be produced by wet adhesion. Simple measurements of the forces needed to separate a pair of metal discs joined by mucus demonstrate that both viscous forces (Stefan adhesion) and surface tension (the two components of wet adhesion) are likely to play significant roles in the tree frog’s adhesive mechanism.The experiments on detachment demonstrate that toe pads are detached from surfaces by peeling, the pads being removed from the rear forwards during forward locomotion up a vertical surface. When the frogs were induced to walk backwards down this vertical slope, peeling occurred from the front of the pad rearwards. Use of a force platform to measure directly the forces exerted by the feet during climbing shows that, during forward locomotion up a vertical slope, this peeling is not accompanied by any detectable detachment forces. Such forces of detachment are seen, however, during backward walking down the slope and when belly skin comes into contact with the platform. That peeling occurs automatically during forward locomotion is supported both by observations of peeling in single toe pads of anaesthetised frogs and by the inability of frogs to adhere to vertical surfaces in a head-down orientation. Indeed, frogs on a rotating vertical surface were observed to adjust their orientations back towards the vertical whenever their deviation from the vertical reached 85.1 ±21.5°. During forward locomotion peeling seems to occur as a natural consequence of the way in which the toes are lifted off surfaces from the rear forwards, while during backward locomotion it is an active process involving the distal tendons of the toes.
Serotonin Depresses the After-Hyperpolarization Through the Inhibition of the Na+/K+ Electrogenic Pump in T Sensory Neurones of the Leech
Authors: Catarsi Stefano , Brunelli Marcello 
Published: April 2021

ABSTRACTIn T sensory neurones of the leech, a train of impulses elicited by intracellular electrical stimulation leads to an after-hyperpolarization of up to 30 mV, mainly due to the activation of the electrogenic Na+/K+-ATPase but partly to a Ca2+-activated K+ conductance. It was found that serotonin reversibly reduced the amplitude of this after-hyperpolarization. We investigated the mechanism of action of serotonin and found: (1) after inhibition of the Ca2+-activated K+ conductance with BaCl2 or CdCl2, serotonin was still able to reduce the afterhyperpolarization; (2) when penetration of T cells with microelectrodes leaking sodium was preceded by serotonin perfusion of the ganglia, the normal hyperpolarization due to the activation of the electrogenic pump was converted to a depolarization; (3) after long-lasting perfusion with K+-free saline solution (which inhibits the Na+/K+ pump), the application of CsCl caused repolarization by reactivating the electrogenic ATPase; serotonin slowed and reduced this repolarization; (4) serotonin potentiated the depolarization of T neurones caused by the inhibition of the Na+/K+ pump following cooling of ganglia and depressed the hyperpolarization after rewarming to room temperature. These data taken together suggest that serotonin directly inhibits the Na+/K+ electrogenic pump.
Ion Activities and Electrochemical Gradients in the Mealworm Rectal Complex
Authors: O’donnell M. J. , Machin J. 
Published: April 2021

ABSTRACTIon activities and potential differences in cellular and extracellular compartments of the rectal complex of Tenebrio molitor L. larvae have been recorded simultaneously using double-barrelled ion-sensitive microelectrodes. On average, the tubule lumen (TL) was 44mV positive to the haemolymph. Values of aK in the posterior rectal complex exceeding 2700 mmol I-1 were measured, sufficient to account for much of the osmolality of 6.8osmolkg-1 driving uptake of water from the rectal lumen. The mean value of 797 mmol l-1 exceeded the Nernst equilibrium activity more than 75-fold, indicating active transport of K+. Intracellular potassium activities in the tubules (153 mmol l-1) were high relative to the values in other insect cells, but moderate relative to TL values. Tubule lumen Na+ activities as high as 400 mmol l-1 and pH values of 6.8 were well above the equilibrium values of 11 mmol I-1 and 7.9, respectively, indicating active transport of these cations as well. The ease and frequency of impaling a perinephric space (PNS) surrounding the tubules established it as a functional compartment. On average, the PNS was 22 mV negative to the haemolymph. Potassium activities in the PNS were close to electrochemical equilibrium with the haemolymph, whereas mean aNa and pH were reduced fivefold and 0.5 units, respectively, below the corresponding Nernst equilibrium values. The results suggest that cations move from haemolymph to PNS, and that the PNS is the immediate source for cation transport into the tubule lumen. Cl- was close to electrochemical equilibrium with the haemolymph in both compartments, and presumably enters the tubule lumen as a passive consequence of positive potential differences (PDs) in the tubule lumen.
Neural Control of the Buccal Muscle Movement in the African Giant Snail Achatina Fulica
Authors: Yoshida Masayuki , Kobayashi Makoto 
Published: April 2021

ABSTRACT
Five pairs of neurones, R(L)-B1, R(L)-B2, R(L)-B3, R(L)-B4 and R(L)-B5, controlling buccal muscle movement, were identified in the buccal ganglia of the African giant snail Achatina fulica Férussac. All these neurones fired during the radula retraction phase of rhythmic buccal activity. Neurones Bl, B2, B4 and B5 made direct excitatory connections to the radula retractor, and Bl, B2, B3 and B5 also made direct excitatory connections with the outer muscle of the buccal mass. Of these neurones, B4 had the most potent effect on contraction of the ipsilateral radula retractor. Physiological and pharmacological analyses suggested that the principal excitatory transmitter of B4 at the neuromuscular junctions was acetylcholine (ACh), although glutamate and aspartate also elicited the contraction. A pair of cerebral ganglion cells, v-RCDN and v-LCDN, was found to have modulatory effects on the muscle contraction evoked by B4 firing and ACh application. Morphological, physiological and immunohistochemical analyses suggested that the modulatory actions of v-CDN on muscle contraction are mediated by serotonin, which may be released from nerve terminals of v-CDN and act directly on the muscle. v-CDN also increased the activity of motoneurone B4. v-CDN shared several common features with serotonergic cerebral cells in other gastropod molluscs.
Magnetic Orientation Of Migratory Wheatears (Oenanthe Oenanthe) In Sweden And Greenland
Authors: Sandberg Roland , Ottosson Ulf , Pettersson Jan 
Published: April 2021

ABSTRACTOrientation experiments were performed with wheatears (Oenanthe oenanthe) subjected to artificially manipulated magnetic fields, in Sweden and Western Greenland, during the autumn migration period. The objective was to compare responses by birds exposed to widely different geomagnetic conditions and, specifically, to clarify if birds are able to use magnetic cues for orientation at high geomagnetic latitudes, as in Western Greenland. Orientation experiments were run under clear sunset skies and under simulated total overcast. Clear-sky tests did not reveal any clearcut orientation responses by wheatears in deflected and vertical magnetic fields. There was a tendency, however, for previous experience of the relationship between geomagnetic cues and visual information to affect the birds’ orientation in a vertical magnetic field. Under simulated overcast, the birds closely followed a 90° shift in magnetic direction in both study areas, and both samples failed to exhibit statistically significant mean directions when tested in vertical magnetic fields. The results clearly demonstrate that wheatears possess a magnetic compass. Furthermore, the birds are able to detect and use local geomagnetic information even at high magnetic latitudes in Western Greenland, notwithstanding the steep inclination (+81°) and large declination (—46°). A persistent attraction towards magnetic northwesterly headings, under both clear and overcast skies, is not consistent with migratory directions according to ringing recoveries and warrants further investigation.
The Relationship Between Oxygen Consumption and Ion Loss in A Freshwater Fish
Authors: Gonzalez Richard J. , Mcdonald D. G. 
Published: April 2021

ABSTRACT
An increase in the functional surface area (FSA) of the gills of freshwater fish facilitates increased oxygen consumption but also increases ion loss across the gills - a phenomenon that has been termed the osmorespiratory compromise. This study on the rainbow trout confirms that Na+ loss accelerates with increasing but also shows that the former always exceeds the latter, i.e. the ion/gas ratio (IGR, ) increases. Since an increase in FSA should affect and equally, the increase in the IGR is attributed to an increase in ion permeability and is thought to arise through opening of paracellular diffusion channels via disruption of tight junctions - a conclusion supported by the effects of brief osmotic shock, low external Ca2+ concentration and catecholamine infusion on ion losses across the gills. By analogy with extensive studies on ‘leaky’ epithelia, these treatments disrupt tight junctions by cell shrinkage, by displacement of Ca2+ from tight junction surfaces or by increasing intralamellar pressure, respectively. While enforced exercise or handling stress substantially increased the IGR of the trout above routine levels, animals were also capable of reducing IGR to about one-tenth of routine levels. This regulation may, in part, be due to decreasing intralamellar pressure, achieved in part by down-regulation of adrenergic receptors, but there appears to be a significant additional level of control that is probably exerted directly at the tight junctions. Such a degree of control is only possible, however, if animals do not continue to exercise and if Ca2+ levels in the water are not reduced. With continued exercise, the IGR returns to routine levels. Consequently, ion losses remain substantially elevated, suggesting that they may ultimately limit maximum sustainable activity. Measurement of the IGR under routine conditions is proposed as a simple means of predicting ion losses during activity and of analyzing the nature of the osmorespiratory compromise.
Mechanisms Controlling Stomach Volume of the Atlantic Cod (Gadus Morhua) Following Gastric Distension
Authors: Grove David J. , Holmgren Susanne 
Published: April 2021

ABSTRACT
Inflation of the cardiac stomach of the cod induced rhythmic contractions of the muscles and a slow increase in stomach volume towards a maximum. After deflation, the stomach remained relaxed and easily distensible for one or more hours. Section of the vagal tracts to the stomach did not change the response. Inflation in vitro produced a somewhat faster relaxation and a much faster recovery to the pre-distended state than occurred in vivo. Stimulation of the cut ends of the vagus raised gastric tone and increased resistance to distension, an effect mediated by cholinergic nerves. Tetrodotoxin and atropine relaxed the stomach so that distension was rapid and the maximal volume increased, revealing slower, possibly myogenic, contractions. The 5-hydroxytryptamine (5-HT) antagonist methysergide, vasoactive intestinal polypeptide (VIP), met-enkephalin and neurotensin did not affect the responses to distension. Somatostatin abolished spontaneous contractions in the resting stomach and lowered gastric tone, but did not further affect the responses to distension. In conclusion, cholinergic nerves maintain gastric tone in the cod. 5-HT neurones are absent in the cod stomach, and there are no indications of a 5-HT/VIP-controlled mechanism operating during distension. The effect of somatostatin differs from that in rainbow trout. For comparison with trout and cod, responses to in vivo gastric distension are also described for the flatfish Scophthalmus maximus, Scophthalmus rhombus, Limanda limanda and Pleuronectes platessa.
Interneurones Mediating the Escape Reaction of the marine Mollusc Clione Limacina
Authors: Arshavsky Yu. I. , Deliagina T. G. , Orlovsky G. N. , Panchin YU. V. , Popova L. B. 
Published: April 2021

ABSTRACT
Neural mechanisms underlying the escape reaction have been extensively studied for over 20 years in many species of animals belonging to several different phyla (for a review, see Eaton, 1984). Among molluscs, the escape reaction has been most thoroughly studied in Tritonia. In this animal a strong mechanical or chemical stimulus applied to the posterior part of the body evokes swimming (for a review, see Getting, 1983; Getting and Dekin, 1985). Electrophysiological experiments on the isolated nervous system revealed that neurones constituting the central pattern generator (CPG) for swimming were strongly depolarized in response to sensory stimulation and that this depolarization caused rhythmic activity in the CPG. However, attempts to identify command neurones mediating the escape reaction in Tritonia have failed (Getting, 1983).