bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematics of Prey Capture in A Flatfish, Pleuronichthys Verticalis
Authors: Gibb Alice C. 
Published: April 2021

ABSTRACT
Hornyhead turbot, Pleuronichthys verticalis (Pleuronectiformes: Pleuronectidae), are morphologically asymmetrical teleosts with substantial bilateral asymmetry in the neurocranium, suspensorium and anterior jaws. In order to quantify the kinematics of prey capture and to test for functional bilateral asymmetries, four individuals of this species were video-taped feeding using a high-speed video system at 200 fields s−1. Frame-by-frame analysis revealed several features not commonly found in prey capture behavior of previously studied ray-finned fishes. These features include (1) extreme lateral compression of the suspensorium and opercular series prior to mouth opening, indicating the consistent presence of a preparatory phase during feeding, (2) apparent dissociation of hyoid retraction and lower jaw depression, (3) prolonged hyoid retraction throughout much of the feeding cycle, and (4) concomitant dorsal rotation of the neurocranium and closing of the jaws. P. verticalis also demonstrate a significant degree of functional bilateral asymmetry during prey capture. When approaching prey, fish flex their heads towards the ocular (anatomically the right) side of the body. During prey capture, their jaws bend out of the midline towards the blind (left) side. Comparisons of the displacement and timing for movements of homologous anatomical features on the ocular and blind sides of the head reveal that maximum gape is always larger on the blind side of the head than on the ocular side. In contrast, other kinematic variables measured are similar on both sides of the head. These results suggest that P. verticalis possess unique functional features of prey capture behavior and that morphological bilateral asymmetry of the head and jaws is associated with, and perhaps causally related to, the functional bilateral asymmetry present during feeding.
The Effects of Thiocyanate on the Intracellular Ion Concentrations of Branchial Epithelial Cells of Brown Trout
Authors: Morgan I. J. , Potts W. T. W. 
Published: April 2021

ABSTRACT
Exposure of brown trout (Salmo trutta) in fresh water to 0.15 mmol l−1 external thiocyanate for 1 h resulted in a significant decrease in chlorine concentration in the branchial mitochondria-rich (MR) cells from 37 mmol l−1 to 22 mmol l−1 . The intracellular sodium concentration in these cells decreased by a similar amount, whilst the intracellular phosphorus concentration increased significantly. In contrast to the MR cells, 0.15 mmol l−1 external thiocyanate had no effect on the intracellular ion concentrations in the pavement epithelial cells. Thiocyanate is known to inhibit chloride uptake in a number of freshwater animals and therefore these data suggest that it is only the MR cells that are involved in the uptake of Cl− in brown trout.
Is Chemosensory Input Essential for the Rapid Rejection of Toxic Foods?
Authors: Glendinning John I. 
Published: April 2021

ABSTRACT
Herbivorous insects often rapidly reject foods containing toxic plant compounds. While the functional significance of this rejection response is clear, the mechanistic basis is not. The role of peripheral chemoreceptors in the rapid rejection of toxic foods was examined using a model system consisting of nicotine and the tobacco hornworm (Manduca sexta), which is a pest of tobacco plants. When offered diets containing naturally occurring concentrations of nicotine, larvae initially fed readily, but abruptly stopped feeding within 30 s. A high percentage of larvae also exhibited toxic responses mediated by the central nervous system (twitching and writhing) to the ingested nicotine within 30 s, indicating that nicotine could have been absorbed within the same time as the rejection response. Two lines of evidence are provided against a role of peripheral chemoreceptors in this rapid rejection response. First, all mouthpart chemoreceptors were ablated from the larvae, and they were then subjected to feeding tests with diets containing either nicotine or a compound (caffeine) that is known to stimulate deterrent taste receptors in M. sexta. Whereas the ablations virtually eliminated the rejection response to caffeine, they had no measurable impact on the rejection response to nicotine. Second, sensory recordings from two important gustatory sensilla (the medial and lateral styloconica) failed to demonstrate a plausible role of sensory input from either sensillum in the rapid rejection of nicotine. The most parsimonious interpretation of these results is that the nicotine rejection response was mediated by a rapidly acting post-ingestive mechanism.
Spatial Patterns of Olfactory Neurons Expressing Specific Odor Receptor Genes in 48-Hour-Old Embryos of Zebrafish Danio Rerio
Authors: Vogt Richard G. , Lindsay Sara M. , Byrd Christine A. , Sun Ming 
Published: April 2021

ABSTRACT
Olfactory neurons have a complex phenotype characterized by their expression of a specific odor receptor (OR) gene and their targeting of an equally specific locus in the olfactory bulb. In the adult fish, olfactory neurons expressing specific ORs are broadly distributed in the epithelium, intermingling with neurons expressing other OR phenotypes. This distributed adult pattern has led to the suggestion that olfactory neuron phenotype is determined by a stochastic process, independent of external positional cues. However, when the fish olfactory system is established during embryogenesis it is simple in its organization, with few olfactory neurons and an olfactory epithelium that has not yet folded into the adult morphology. It is possible that positional cues might act in the embryo to establish an initial population and pattern of olfactory neuron phenotypes and that subsequent morphogenesis and neuronal addition lead to the randomized distribution of neurons. To test this possibility, we examined the spatial patterns of olfactory neurons expressing specific OR genes in 48 h embryos, a time of relative simplicity in the developing olfactory epithelium. Three-dimensional plots of neuron distributions were made, and comparisons of OR expression patterns were made between right and left epithelia, between individual animals and between different OR genes. The patterns of OR gene expression were not conserved in these comparisons. Mathematical analysis of 21 epithelia for the degree of order in the distribution of olfactory neurons argued strongly that the neurons expressing given ORs are randomly distributed in the 48 h embryos. These results are consistent with those observed from adult tissue and support models suggesting that extrinsic positional cues do not have a major role in specifying olfactory neuron phenotypes.
The Energetic Cost of Activation of White Muscle Fibres from the Dogfish Scyliorhinus Canicula
Authors: Lou F. , Curtin N. A. , Woledge R. C. 
Published: April 2021

ABSTRACT
The energetic cost of activation was measured during an isometric tetanus of white muscle fibres from the dogfish Scyliorhinus canicula. The total heat production by the fibres was taken as a measure of the total energetic cost. This energy consists of two parts. One is due to crossbridge interaction which produces isometric force, and this part varies linearly with the degree of filament overlap in the fibres. The other part of the energy is that associated with activation of the crossbridges by Ca2+, mainly with uptake of Ca2+ into the sarcoplasmic reticulum by the ATP-driven Ca2+ pump. Total heat production was measured at various degrees of filament overlap beyond the optimum for force development. Extrapolation of heat versus force production data to evaluate the heat remaining at zero force gave a value of 34±5 % (mean ± S.E.M., N=24) for activation heat as a percentage of total heat production in a 2.0 s isometric tetanus. Values for 0.4 and 1.0 s of stimulation were similar. Comparison with values in the literature shows that the energetic cost of activation in dogfish muscle is very similar to that of frog skeletal muscle and it cannot explain the lower maximum efficiency of dogfish muscle compared with frog muscle. The proportion of energy for activation (Ca2+ turnover) is similar to that expected from a simple model in which Ca2+ turnover was varied to minimize the total energy cost for a contraction plus relaxation cycle.
The Metabolic Cost Of Swimming In Marine Homeotherms
Authors: Hind A. T. , Gurney W. S. C. 
Published: April 2021

ABSTRACT
This paper describes a model of the metabolic cost of swimming in pinnipeds and its application to other marine homeotherms. The model takes account of both hydrodynamic and thermal processes. The thermal component incorporates both free and forced convection and takes account of the effect of hair on free convection. Using data from the literature to evaluate all but two of the parameters, we apply the model to metabolic rate data on phocid seals, otariids (sea lions), penguins and minke whales. We show that the model is able to reproduce two unusual features of the data; namely, a very rapid increase in metabolic rate at low velocities and an overall rise in metabolic rate with velocity which is slower than the rise in hydrodynamic drag force. The work shows the metabolic costs of propulsion and thermoregulation in a swimming homeotherm to be interlinked and suggests differing costs of propulsion for different modes of swimming. This is potentially of ecological significance since the swimming speed that minimises the cost of transport for an animal will change with changes in water temperature.
Dragonfly Flight: I. Gliding Flight and Steady-State Aerodynamic Forces
Authors: Wakeling J. M. , Ellington C. P. 
Published: April 2021

ABSTRACT
The free gliding flight of the dragonfly Sympetrum sanguineum was filmed in a large flight enclosure. Reconstruction of the glide paths showed the flights to involve accelerations. Where the acceleration could be considered constant, the lift and drag forces acting on the dragonfly were calculated. The maximum lift coefficient (CL) recorded from these glides was 0.93; however, this is not necessarily the maximum possible from the wings. Lift and drag forces were additionally measured from isolated wings and bodies of S. sanguineum and the damselfly Calopteryx splendens in a steady air flow at Reynolds numbers of 700–2400 for the wings and 2500–15 000 for the bodies. The maximum lift coefficients (CL,max) were 1.07 for S. sanguineum and 1.15 for C. splendens, which are greater than those recorded for all other insects except the locust. The drag coefficient at zero angle of attack ranged between 0.07 and 0.14, being little more than the Blassius value predicted for flat plates. Dragonfly wings thus show exceptional steady-state aerodynamic properties in comparison with the wings of other insects. A resolved-flow model was tested on the body drag data. The parasite drag is significantly affected by viscous forces normal to the longitudinal body axis. The linear dependence of drag on velocity must thus be included in models to predict the parasite drag on dragonflies at non-zero body angles.
A Tympanal Hearing Organ in Scarab Beetles
Authors: Forrest T. G. , Read M. P. , Farris H. E. , Hoy R. R. 
Published: April 2021

ABSTRACT
We describe the paired hearing organ of the scarab beetle Euetheola humilis. The auditory structures of the beetle are typical of other insect ears in that they have a thinned tympanic membrane backed by a tracheal airsac with associated chordotonal sensory structures. The tympanic membranes of the beetle are part of its cervical membrane and are located behind the head, where the cervix attaches dorsally and laterally to the pronotum. Each membrane is approximately 3 μm thick. The chordotonal sensory organ, which lies within the tracheal airsac, contains 3–8 scolopidia that attach by accessory cells directly to the tympanic membrane. Neurophysiological recordings from the neck connective of the beetle revealed that the auditory system is sensitive to frequencies between 20 and 80 kHz and has a minimum threshold of approximately 58 dB at 45 kHz. The neurophysiological audiogram is identical to the behavioral audiogram for a head roll, one behavioral component of the beetle’s startle response elicited by ultrasound. Blocking experiments show that the membranous structures on the cervix are indeed the hearing organs. Neurophysiologically determined thresholds increased by more than 35 dB when drops of water covered the tympanic membranes and were essentially restored to the control level when the water was later removed. At least three other genera of Dynastinae scarabs have similar tympanum-like structures located in their cervical membranes. Behavioral and neurophysiological data show that the frequency tuning of species in two of these genera, Cyclocephala and Dyscinetus, is nearly identical to that of E. humilis. Our discovery represents only the second group of beetles known to respond to airborne sounds. However, the hearing organs of these scarab beetles differ in structure and placement from those of the tiger beetles, and thus they represent an independent evolution of auditory organs in the Coleoptera.
Myotomal Slow Muscle Function of Rainbow Trout Oncorhynchus Mykiss During Steady Swimming
Authors: Hammond Lucy , Altringham John D. , Wardle Clement S. 
Published: April 2021

ABSTRACT
Strain and activity patterns were determined during slow steady swimming (tailbeat frequency 1.5–2.5 Hz) at three locations on the body in the slow myotomal muscle of rainbow trout Oncorhynchus mykiss using sonomicrometry and electromyography. Strain was independent of tailbeat frequency over the range studied and increased significantly from ±3.3 % l0 at 0.35BL to ±6 % at 0.65BL, where l0 is muscle resting length and BL is total body length. Muscle activation occurred significantly later in the strain cycle at 0.35BL (phase shift 59 °) than at 0.65BL (30 °), and the duration of activity was significantly longer (211 ° at 0.35BL and 181 ° at 0.65BL). These results differ from those of previous studies. The results have been used to simulate in vivo activity in isolated muscle preparations using the work loop technique. Preparations from all three locations generated net positive power under in vivo conditions, but the negative power component increased from head to tail. Both kinematically, and in the way its muscle functions to generate hydrodynamic thrust, the rainbow trout appears to be intermediate between anguilliform swimmers such as the eel, which generate thrust along their entire body length, and carangiform fish (e.g. saithe Pollachius virens), which generate thrust primarily at the tail blade.
Spatial Vision in the Prosobranch Gastropod Ampularia Sp.
Authors: Seyer Jan-Olof , Nilsson Dan-E. , Warrant Eric J. 
Published: April 2021

ABSTRACT
The eyes of gastropods of the genus Ampularia superficially resemble the well-developed camera-type eyes of Littorina littorea and Strombus raninus. The eyes are of the closed-vesicle type, having a cornea and a lens that is separated from the retina by a narrow vitreous body.
Light and electron microscopy were used to generate an accurate geometrical model of the Ampularia sp. eye, which was then used to predict its optical performance. The image quality of the lens was investigated using a modified microscope and revealed that images suffer from severe aberrations. The focal length was estimated to be approximately 430 μm, putting the plane of best focus in or just proximal to the rhabdoms. The aberrant optics result in a large retinal blur-circle with a diameter of approximately 120 μm and an angular half-width of approximately 17 °, allowing only comparatively poor resolution compared with the eyes of Littorina littorea and Strombus raninus. Behavioural experiments revealed no significant optomotor response.
The results imply that Ampularia sp. has poor spatial vision, limited by the blur-circles on the retina. The eyes appear to be suitable only for relatively simple visual tasks, such as finding an open water surface for breathing, but the large size of the eye allows it to perform this task even at night.
A Study of the Temporary Adhesion of the Podia in the Sea Star Asterias Rubens (Echinodermata, Asteroidea) through their Footprints
Authors: Flammang Patrick , Michel Alain , Van Cauwenberge Anne , Alexandre Henri , Jangoux Michel 
Published: April 2021

ABSTRACT
Sea stars are able to make firm but temporary attachments to various substrata owing to secretions released by their podia. A duo-glandular model has been proposed in which an adhesive material is released by two types of non-ciliated secretory (NCS1 and NCS2) cells and a de-adhesive material is released by ciliated secretory (CS) cells. The chemical composition of these materials and the way in which they function have been investigated by studying the adhesive footprints left by the asteroids each time they adhere to a substratum. The footprints of Asterias rubens consist of a sponge-like material deposited as a thin layer on the substratum. Inorganic residues apart, this material is made up mainly of proteins and carbohydrates. The protein moiety contains significant amounts of both charged (especially acidic) and uncharged polar residues as well as half-cystine. The carbohydrate moiety is also acidic, comprising both uronic acids and sulphate groups. Polyclonal antibodies have been raised against footprint material and were used to locate the origin of footprint constituents in the podia. Extensive immunoreactivity was detected in the secretory granules of both NCS1 and NCS2 cells, suggesting that their secretions together make up the bulk of the adhesive material. No immunoreactivity was detected in the secretory granules of CS cells, and the only other structure strongly labelled was the outermost layer of the cuticle, the fuzzy coat. This pattern of immunoreactivity suggests that the secretions of CS cells are not incorporated into the footprints, but instead might function to jettison the fuzzy coat, thereby allowing the podium to detach.
Glutamatergic Neuromuscular Transmission in the Heart Of The Isopod Crustacean Ligia Exotica
Authors: Sakurai Akira , Mori Akihiko , Yamagishi Hiroshi 
Published: April 2021

ABSTRACT
Neuromuscular transmission between the cardiac ganglion (CG) and the myocardium was examined in the adult heart of the isopod crustacean Ligia exotica. Intracellular injection of neurobiotin into the CG neurones revealed that all six CG neurones send their axons onto the cardiac muscle, where they form axon terminals bearing varicosities. All the CG neurones and their processes exhibited glutamate-like immunoreactivity. The cardiac muscle showed depolarizing membrane potential responses to glutamate applied focally to sites close to axon terminals bearing varicosities. Both the glutamate-induced response and the excitatory junctional potential (EJP) showed desensitization in response to the repeated application of glutamate. Under voltage-clamp conditions, the cardiac muscle produced inward current responses to focally applied glutamate. The reversal potential for the glutamate-induced current estimated from extrapolation of the linear current/voltage relationship was similar to that of the excitatory junctional current evoked by ganglionic nerve stimulation. Both the glutamate-induced response and the EJP were blocked by a glutamate-specific antagonist, Joro spider toxin. These results led us to conclude that the CG neurones of Ligia exotica are glutamatergic motoneurones.
Acid–Base and Respiratory Responses to Hypoxia in the Grasshopper Schistocerca Americana
Authors: Greenlee Kendra J. , Harrison Jon F. 
Published: April 2021

ABSTRACT
How do quiescent insects maintain constant rates of oxygen consumption at ambient values as low as 2–5 kPa? To address this question, we examined the response of the American locust Schistocerca americana to hypoxia by measuring the effect of decreasing ambient on haemolymph acid–base status, tracheal and CO2 emission. We also tested the effect of hypoxia on convective ventilation using a new optical technique which measured the changes in abdominal volume during ventilation. Hypoxia caused a progressive increase in haemolymph pH and a decrease in haemolymph . A Davenport analysis suggests that hypoxia is accompanied by a net transfer of base to the haemolymph, perhaps as a result of intracellular pH regulation. Hypoxia caused a progressive increase in convective ventilation which was mostly attributable to a rise in ventilatory frequency. Carbon dioxide conductance (μmol h−1 kPa−1) across the spiracles increased more than threefold, while conductance between the haemolymph and primary trachea nearly doubled in 2 kPa O2 relative to room air. The rise in trans-spiracular conductance is completely attributable to the elevations in convective ventilation. The rise in tracheal conductance in response to hypoxia may reflect the removal of fluid from the tracheoles described by Wigglesworth. The low critical of quiescent insects can be attributed (1) to their relatively low resting metabolic rates, (2) to the possession of tracheal systems adapted for the exchange of gases at much higher rates during activity and (3) to the ability of insects to rapidly modulate tracheal conductance.
Ca2+-ATPase ACTIVITY AND Ca2+ UPTAKE BY SARCOPLASMIC RETICULUM IN FISH HEART: EFFECTS OF THERMAL ACCLIMATION
Authors: Aho Eija , Vornanen Matti 
Published: April 2021

ABSTRACT
This study was designed to compare the activities of sarcoplasmic (SR) Ca2+-ATPase and Ca2+ uptake in fish and mammalian hearts and to determine whether thermal acclimation has any effect on the function of the cardiac SR in fish. To this end, we measured thapsigargin-sensitive Ca2+-ATPase activity and thapsigargin-inhibitable Ca2+ uptake velocity in crude cardiac homogenates of newborn and adult rats and of two teleost fish (crucian carp and rainbow trout) acclimated to low (4°C) and high (17°C and 24°C for trout and carp, respectively) ambient temperatures.
The TG-sensitive Ca2+-ATPase activity was highest in adult rat, and the corresponding activities of cold-acclimated trout, warm-acclimated trout, warm-acclimated carp, cold-acclimated carp and newborn rat were 76, 58, 43, 28 and 23%, respectively, of that of the adult rat at 25°C. SR Ca2+ uptake velocity, measured using Fura-2 at room temperature (approximately 22°C), was highest in cold-acclimated trout, and the values for adult rat, warm-acclimated trout, newborn rat, warm-acclimated carp and cold-acclimated carp were 93, 56, 24, 21 and 14% of the uptake velocity of cold-acclimated trout, respectively. When corrected to the body temperature of the animal, the relative rates of SR Ca2+ uptake were 100, 26, 19, 18, 11 and 2% for adult rat, newborn rat, cold-acclimated trout, warm-acclimated trout, warm-acclimated carp and cold-acclimated carp, respectively.
These findings show that SR Ca2+ uptake is slower in fish than in mammalian hearts and that marked species-specific differences exist among teleost fish in this respect. Furthermore, acclimation to cold increases the Ca2+ uptake rate of trout cardiac SR (complete thermal compensation) but decreases the SR Ca2+ uptake rate of crucian carp heart. This difference in acclimation response probably reflects the different activity patterns of the two species in their natural habitat during the cold season.