bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gain Changes in Sensorimotor Pathways of the Locust Leg
Authors: Büschges Ansgar , Wolf Harald 
Published: April 2021

ABSTRACT
Feedback systems that control the leg joints of animals must be highly flexible in adapting to different behavioural tasks. One manifestation of such flexibility is changes in the gain of joint control networks. The femur–tibia (FT) control network of the locust leg is one of the feedback systems most thoroughly studied with regard to its neural circuitry. Despite excellent information concerning network topology, however, actual gain changes and their underlying mechanisms have not yet been examined because of the marked spontaneous variations in the action of the control network for this joint. We describe a behavioural situation and a preparation in which the locust (Locusta migratoria L.) FT control network exhibits reproducible changes in gain, allowing investigation of the neuronal basis of gain control. After (‘fictive’) flight motor activity, the gain of resistance reflexes in the FT joint of the locust middle leg is significantly decreased, with the flexor tibiae muscles being affected more strongly than the extensor muscles. Immediately after flight motor activity, the gain may be as low as 30 % of pre-flight levels. It returns to pre-flight values in under 150 s.
The decrease in gain following flight motor activity is due to a decrease in motoneurone recruitment in the resistance reflex elicited by stimulation of the appropriate mechanoreceptor, the femoral chordotonal organ. Motoneurone recruitment is changed as a result of a drastic decline in the stimulus-related synaptic input to the motoneurones, which appears to be produced exclusively at the level of the pre-motor network. Two factors led to this conclusion: first, we found no indication of changes in membrane potential or membrane conductance of the tibia flexor and extensor motoneurones; second, recording from identified pre-motor nonspiking interneurones demonstrated that these may be involved in the observed gain changes. The putative behavioural relevance is discussed.
Mechanism and Possible Behavioural Relevance of Retinal Movements in the Ctenid Spider Cupiennius Salei
Authors: Kaps Florian , Schmid Axel 
Published: April 2021

ABSTRACT
Like most spiders, the nocturnal hunting spider Cupiennius salei is able to move the retinae of its antero-median (AM) eyes. In the present study, the morphological and physiological properties of the eye muscles and the mechanism and behavioural relevance of retinal movements are investigated.
The retinal movements are brought about by two forces: (i) contractions of the dorsal and ventral eye muscles, and (ii) the passive elastic restoring force of the eye tube and eye muscles (the presumed counteracting force). The dorsal eye muscle consists of 15–18 striated fibres and is 600 µm long. The ventral eye muscle is longer (650 µm) and consists of 20–22 striated fibres.
The direction of the gaze of the retinae brought about by the eye muscles (active retinal movements) depends on the contraction states of the two eye muscles. The medially directed action of both eye muscles does not allow active movements of the eye tube in any lateral direction. Thus, the direction of gaze cannot actively be shifted medially. After active displacement of the retina, the elasticity of the eye tube and eye muscles passively moves the eye tube back to its resting position.
There are two types of retinal movements. (i) Spontaneous microsaccades (duration 80ms; excursion 3 °) are caused by the spontaneous contraction of only the dorsal eye muscle. They are ideally suited for preventing the adaptation of the sensory cells since their mean excursion (3°) perfectly fits the inter-receptor angle (2.9°) in the AM eye of Cupiennius salei. (ii) Induced movements (duration 100–500ms; excursions 4–15°) are caused by the contraction of both eye muscles and occur only after mechanical stimulation. Induced movements were elicited by stimulating the mechanosensory organs (trichobothria and slit sense organs) of the spider’s legs. A stimulus on one side of the spider induces movements of the ipsilateral retina only. We therefore suggest that induced retinal movements are saccades shifting the gaze of the spider laterally towards the site of mechanical stimulation.
According to behavioural experiments, the ability of a spider to locate an immobile target is highly impaired after blinding its AM eyes. We suggest that the motility of the AM eyes is required to locate stationary objects.
Food-Deprivation Affects Seawater Acclimation in Tilapia: Hormonal and Metabolic Changes
Authors: Vijayan Mathilakath M. , Morgan John D. , Sakamoto Tatsuya , Grau E. Gordon , Iwama George K. 
Published: April 2021

ABSTRACT
We tested the hypothesis that nutritional state affects seawater acclimation by transferring either fed or food-deprived (2 weeks) male tilapia (Oreochromis mossambicus) from fresh water to full-strength sea water. Food-deprivation resulted in a significant increase in plasma concentrations of Na+, Cl−, cortisol, glucose, total amino acid, glutamate, serine and alanine, and in hepatic pyruvate kinase (PK) and lactate dehydrogenase (LDH) activities, whereas the prolactin-188 to prolactin-177 ratio (tPRL188:tPRL177) and plasma prolactin-188 (tPRL188), lactate, arginine and hepatic glycogen content and hepatic alanine aminotransferase (AlaAT) and 3-hydroxyacyl-Coenzyme A dehydrogenase (HOAD) activities were lower than in the fed group. Seawater transfer significantly increased the tPRL188:tPRL177 ratio and plasma concentrations of Na+, Cl−, K+, growth hormone (GH), glucose, aspartate, tyrosine, alanine, methionine, phenylalanine, leucine, isoleucine and valine levels as well as gill Na+/K+-ATPase activity and hepatic PK and LDH activities, whereas plasma tPRL177, tPRL188, glycine and lysine concentrations were significantly lower than in fish retained in fresh water. There was a significant interaction between nutritional state and salinity that affected the tPRL188:tPRL177 ratio and plasma concentrations of Cl−, GH, glucose, aspartate, tyrosine, serine, alanine, glycine, arginine and hepatic PK, LDH, AlaAT, aspartate aminotransferase, glutamate dehydrogenase and HOAD activities. These results, taken together, indicate that food-deprived fish did not regulate their plasma Cl− levels, despite an enhancement of plasma hormonal and metabolic responses in sea water. Our study also suggests the possibility that plasma prolactin and essential amino acids may be playing an important role in the seawater acclimation process in tilapia.
Axial Muscle Function During Lizard Locomotion
Authors: Ritter Dale 
Published: April 2021

ABSTRACT
It was recently reported that the epaxial muscles of a lizard, Varanus salvator, function to stabilize the trunk during locomotion, and it was suggested that this stabilizing role may be a shared derived feature of amniotes. This result was unexpected because it had previously been assumed that the epaxial muscles of lizards function to produce lateral bending during locomotion and that only in mammals and birds were the epaxial muscles active in stabilizing the trunk. These results and the inferences made from them lead to two questions. (1) Is the pattern of epaxial muscle activity observed in V. salvator representative of a basal lizard condition or is it a derived condition that evolved within lizards? (2) If the epaxial muscles do not produce lateral bending, which muscles do carry out this function? These questions were addressed by collecting synchronous electromyographic (EMG) and kinematic data from two lizard species during walking and running. EMG data were collected from the epaxial muscles of a lizard species from a basal clade, Iguana iguana, in order to address the first question. EMG data were collected from the hypaxial muscles of both Iguana iguana and Varanus salvator to address the second question. The timing of epaxial muscle activity in Iguana iguana relative to the kinematics of limb support and lateral trunk bending is similar to that observed in Varanus salvator, a finding that supports the hypothesis that the epaxial muscles stabilize the trunk during locomotion in lizards and that this stabilizing role is a basal feature of lizards. Therefore, a stabilizing function of the epaxial muscles is most parsimoniously interpreted as a basal amniote feature. In both Iguana iguana and Varanus salvator, the activity of two of the hypaxial muscles, the external oblique and rectus abdominis, is appropriately timed for the production of lateral bending. This indicates that elements of the hypaxial musculature, not the epaxial musculature, are the primary lateral bending muscles of lizards.
Prolactin Antagonizes the Corticoid-Promoted Development of Adult-Type Epidermis in Cultured Larval Bullfrog Skin
Authors: Takada Makoto , Yai Hideko , Komazaki Shinji , Takayama-Arita Kazue 
Published: April 2021

ABSTRACT
EDTA-treated larval bullfrog skin, in which apical and skein cells had been removed and only basal cells remained, was cultured in one of four media. These contained either aldosterone (Aldo) or a mixture of Aldo, hydrocortisone (HC) and corticosterone (C), each either supplemented with prolactin (PRL) or lacking PRL. Skin cultured with Aldo alone or with the corticoid mixture (Aldo+HC+C) developed an adult-type epidermis: (i) both types of skin reacted to human blood group antigen A, a marker for the adult-type epidermis of bullfrog skin; (ii) amiloride decreased the short-circuit current Isc in these skin preparations, but acetylcholine (ACh) had no effect on the Isc. It seemed to make little difference to the results whether the skin was cultured with Aldo or with the corticoid mixture. PRL antagonized the action of Aldo and induced the development of a larval-type epidermis in both skin preparations: (i) the skin preparations did not react to human blood group antigen A; (ii) acetylcholine and amiloride each stimulated Isc in these preparations. Since ACh and amiloride each stimulated the Isc in skin with apical cells, ACh/amiloride-stimulated channels may be located on these cells.
Comparison Of The Fast-Start Performances Of Closely Related, Morphologically Distinct Threespine Sticklebacks (Gasterosteus Spp.)
Authors: Law T. C. , Blake R. W. 
Published: April 2021

ABSTRACT
Fast-start escape performances for two species of threespine stickleback, Gasterosteus spp., were investigated using high-speed cinematography (400 Hz). The two fishes (not yet formally described, referred to here as benthic and limnetic) inhabit different niches within Paxton Lake, British Columbia, Canada, and are recent, morphologically distinct species. All escape responses observed for both species were double-bend C-type fast-starts. There were no significant differences between the species for any linear or angular parameter (pooled averages, both species: duration 0.048 s, distance 0.033 m, maximum velocity 1.10 m s−1, maximum acceleration 137m s−2, maximum horizontal angular velocity 473.6 rad s−1 and maximum overall angular velocity 511.1 rad s−1). Benthics and limnetics have the greatest added mass (Ma) at 0.3 and 0.6 body lengths, respectively. The maximum Ma does not include the fins for benthics, but for limnetics the dorsal and anal fins contribute greatly to the maximum Ma. The deep, posteriorly placed fins of limnetics enable them to have a fast-start performance equivalent to that of the deeper-bodied benthics.
Both the limnetic and benthic fishes have significantly higher escape fast-start velocities than their ancestral form, the anadromous threespine stickleback Gasterosteus aculeatus, suggesting that the high performance of the Paxton Lake sticklebacks is an evolutionarily derived trait. In this biomechanical study of functional morphology, we demonstrate that similar high fast-start performance can be achieved by different suites of morphological characteristics and suggest that predation might be the selective force for the high escape performance in these two fishes.
Kinematics and Critical Swimming Speed of Juvenile Scalloped Hammerhead Sharks
Authors: Lowe Christopher G. 
Published: April 2021

ABSTRACT
Kinematics and critical swimming speed (Ucrit) of juvenile scalloped hammerhead sharks Sphyrna lewini were measured in a Brett-type flume (635 l). Kinematic parameters were also measured in sharks swimming in a large pond for comparison with those of sharks swimming in the flume. Sharks in the flume exhibited a mean Ucrit of 65±11 cm s− (± S.D.) or 1.17±0.21 body lengths per second (L s−1), which are similar to values for other species of sharks. In both the flume and pond, tailbeat frequency (TBF) and stride length (LS) increased linearly with increases in relative swimming speed (Urel=body lengths traveled per second). In the flume, tailbeat amplitude (TBA) decreased with increasing speed whereas TBA did not change with speed in the pond. Differences in TBF and LS between sharks swimming in the flume and the pond decreased with increases in Urel. Sharks swimming at slow speeds (e.g. 0.55 L s−1) in the pond had LS 19 % longer and TBF 21 % lower than sharks in the flume at the same Urel. This implies that sharks in the flume expended more energy while swimming at comparable velocities. Comparative measurements of swimming kinematics from sharks in the pond can be used to correct for effects of the flume on shark swimming kinematics and energetics.
Size-Dependence of Water-Running Ability in Basilisk Lizards (Basiliscus Basiliscus)
Authors: Glasheen J. W. , Mcmahon T. A. 
Published: April 2021

ABSTRACT
In the past, it has been proposed that basilisk lizards (Basiliscus basiliscus) are able to reach high population densities because the juveniles and adults have differing water-running abilities and therefore live in different habitats. However, there is no a priori reason to expect juveniles to be better able to run on water than adults. To determine the causal relationship between body size and water-running ability, we made three types of measurements: (1) direct morphological measurements on preserved specimens; (2) hydrodynamic measurements on physical models of the lizards’ feet; and (3) kinematic measurements on basilisk lizards running on water. The information gathered from these investigations was used to develop an allometric model which predicted the maximum upward force impulses that the lizards could generate. We find that small lizards have a capacity to generate large force surpluses. A 2 g lizard can generate a maximum upward impulse that is more than twice that needed to support its body weight (225 %). In contrast, a 200 g lizard, under optimal conditions, can just barely support its body weight (111 %).
Contralateral Sprouting and Compensatory Innervation Following the permanent Lesion of a Ganglionic Connective in the Snail
Authors: Baker Michael W. , Chiasson Bernard J. , Croll Roger P. 
Published: April 2021

ABSTRACT
The fate of sprouted fibres was examined following long-term recovery from lesions to the central nervous system of the snail Achatina fulica. Axonal dye-labelling of one of the cerebrobuccal connectives (CBC), following either a cut or a crush to the opposite CBC, revealed supernumerary labelling of neuronal elements in both the cerebral and buccal ganglia in the weeks following treatment. A part of this sprouting response involved the rerouting of axonal projections from injured neurones that project contralaterally into the uninjured CBC. In addition, intracellular dye-fills, immunocytochemistry for detection of serotonin and electrophysiological measurements all revealed that a contralateral, uninjured neurone, the metacerebral giant (MCG) cell, sprouted new processes to invade the buccal ganglion denervated by the lesion. The contralateral MCG also increased synaptic drive over a neurone in the denervated buccal ganglion, a cell that normally receives strong input only from the lesioned ipsilateral MCG. After 5 weeks of recovery, morphological and electrophysiological measurements returned to normal levels in animals receiving a crush to the CBC, suggesting a retraction of sprouted projections following successful regeneration across the lesioned pathway. In contrast, the measurements indicative of sprouted fibres continued for up to 5 months when the regenerative response was prevented by cutting the CBC. Together, these results suggest that both the cessation of sprouting and the eventual retraction of sprouted fibres in Achatina fulica is contingent upon successful regeneration of the damaged axonal pathway.
Wave-Induced Forces on the Giant Kelp Macrocystis Pyrifera (Agardh): Field Test of a Computational Model
Authors: Utter Barbara D. , Denny Mark W. 
Published: April 2021

ABSTRACT
We propose a hydro-mechanical numerical model that predicts the maximal tension to which stipes of the giant kelp Macrocystis pyrifera will be subjected when exposed to ocean waves. Predicted maximal tensions are close to those measured in the field. The strength of Macrocystis pyrifera stipes was measured, allowing our prediction of forces to be translated into a prediction of the fraction of stipes broken. Predicted breakage is low even for extreme storm waves, a testament to the mechanical design of individual kelp fronds. However, empirically measured rates of kelp mortality can be high, considerably higher than those predicted on the basis of hydrodynamic forces acting alone. This indicates that factors not taken into account in our model (such as holdfast dislodgment, entanglement of stipes, damage from herbivory and wave breaking) contribute substantially to mortality in Macrocystis pyrifera.
Differences in Thermal Balance, Body Temperature and Activity Between Non-Melanic and Melanic Two-Spot Ladybird Beetles (Adalia Bipunctata) Under Controlled Conditions
Authors: Jong Peter W. De , Gussekloo Sander W. S. , Brakefield Paul M. 
Published: April 2021

ABSTRACT
The consequences of the elytral colour difference between non-melanic (red) and melanic (black) two-spot ladybirds for their thermal properties were studied by applying and testing a biophysical model. The expected differential effects of variation in transmission through the elytra, body size, width of the subelytral cavity, ambient temperature, radiation intensity and wind speed are described, assuming that the two colour patterns represent differences in elytral reflectance and transmittance. The model predicts a higher body temperature for melanic beetles under most conditions. Invasive temperature measurements on living beetles under ranges of specified conditions with respect to ambient temperature, radiative regime and wind speed were in qualitative agreement with the model predictions and, considering the assumptions made, closely corresponded at the quantitative level. The consequences of the temperature differences for morph activity were studied by measuring walking speeds and the time needed to become active for each morph under the various conditions. The results are consistent with the differences in body temperature, assuming an optimum curve relating performance to body temperature. The colour difference between morphs appeared to be the principal factor influencing activity.
A Novel Type of Mechanoreception By the Flagella of Chlamydomonas
Authors: Yoshimura Kenjiro 
Published: April 2021

ABSTRACT
A novel type of mechanosensory mechanism is found in Chlamydomonas reinhardtii. When a cell is captured with a suction pipette and a negative pressure is applied, the cell produces repetitive Ca2+ impulses at a frequency of 0.5–1.0 Hz. The impulse frequency increases with the applied pressure. The impulses are produced when the flagella are sucked into the pipette but not when the cell body is sucked in leaving the flagella outside the pipette. Cells with short flagella produce impulses of small amplitude. Thus, the site where the cell senses mechanical stimuli and generates the impulse current must be localized at the flagella. The amplitude, shape and ion selectivity of the pressure-induced impulses are distinct from the all-or-none flagellar current that is evoked by photostimulation. The impulses are possibly produced by a combination of currents passing through mechanosensitive channels and Ca2+ channels. This response probably functions to modulate flagellar beating and thereby to regulate the behaviour of the cell.
Control of Resting Ventilation Rate in Grasshoppers
Authors: Gulinson Scotti L. , Harrison Jon F. 
Published: April 2021

ABSTRACT
We examined the effect of extracellular acid–base status and tracheal gas levels on the ventilation rate of resting Romalea guttata and Schistocerca americana grasshoppers. We manipulated haemolymph pH and [HCO3- ] within normal physiological ranges using injections of HCl, NaOH, NaHCO3 and NaCl into the haemocoel. In contrast to terrestrial vertebrates, there was no evidence that extracellular acidification increases ventilation rate in grasshoppers. Elevation of haemolymph bicarbonate levels (by NaHCO3 injection) increased ventilation rate, while depression of haemolymph bicarbonate levels (HCl injection) had no effect. Injection of NaHCO3 also increased tracheal , suggesting that the effect of the NaHCO3 injection might be mediated by a sensitivity of the ventilatory system to tracheal gases. We tested for effects of tracheal gases on ventilation rate by independently manipulating tracheal and using tracheal perfusions. Ventilation rate was positively correlated with tracheal and negatively correlated with tracheal . Increasing tracheal above normal resting levels or decreasing tracheal below normal levels decreased ventilation rate. We conclude that quiescent grasshoppers regulate tracheal and by varying ventilation rate and that both and in the trachea stimulate ventilation in normal, resting grasshoppers.
The Effects of Serotonin and Dopamine on Salivary Secretion by Isolated Cockroach Salivary Glands
Authors: Just Frank , Walz Bernd 
Published: April 2021

ABSTRACT
We have studied the effects of 3-hydroxytyramine (dopamine) and 5-hydroxytryptamine (serotonin) on (1) the rates of salivation from isolated salivary glands of the cockroach Periplaneta americana, (2) the protein content of the saliva, and (3) the ultrastructure of the salivary gland epithelium. The rates of neurotransmitter-induced salivation varied in a dose-dependent manner within the concentration range 10−9 to 10−4 mol l−1. Half-maximal secretory rates were induced by 6×10−7 mol l−1 serotonin and 1.1×10−7 mol l−1 dopamine. Stimulation of the glands by serotonin resulted in the production of a protein-rich saliva, whereas saliva was protein-free after stimulation by dopamine. Electron microscopic studies revealed that the central cells, which are believed to produce the proteinaceous components of the saliva, secrete their vesicular content after stimulation by 10−6 mol l−1 serotonin for 20 min. In contrast, no morphological changes could be detected after stimulation by 10−6 mol l−1 dopamine. These data indicate that dopamine stimulates only the secretion of the fluid component of the saliva, whereas serotonin is necessary to stimulate secretion of the proteinaceous components.
Measuring Leg Thrust Forces in the Common Starling
Authors: Bonser Richard H. C. , Rayner Jeremy M. V. 
Published: April 2021

ABSTRACT
We describe the design of a force-transducing perch which measures the reaction forces of small birds taking off and landing. In common starlings, landing forces are lower than take-off forces, because the bird may decelerate prior to landing by using its wings. Both landing and take-off forces are significantly correlated with body mass; however, the angles of these reaction forces show no significant mass-dependence and are not repeatable within individuals. Diversity in take-off or landing strategy could be advantageous in confusing predators.