bluuebunny/crossref_metadata_2025 huggingface dataset:
Experience-dependent changes in the number of chemosensory sensilla on the mouthparts and antennae of Locusta Migratoria
Authors: Rogers S. M. , Simpson S. J.
Published: April 2021

The effect of diet on the number of gustatory and olfactory sensilla was investigated in locusts. Insects fed for the final two stadia on nutritionally adequate synthetic foods have fewer sensilla on the maxillary palps and antennae than insects fed on the usual rearing diet of seedling wheat. This effect was seen irrespective of the nutritional balance of the foods and was independent of the concentration of nutrients present or the size of the insect. Supplying wheat odour to locusts fed synthetic foods had no effect on the number of sensilla present on the palps, but completely reversed the decrease in the number of olfactory sensilla of the antennae and partially reversed the decrease in the number of antennal uniporous trichoid sensilla. Locusts that were allowed to select between two nutritionally unbalanced but complementary synthetic foods had a higher number of sensilla on the maxillary palps than those fed individual synthetic foods, providing the two foods differed substantially in their protein:carbohydrate ratios. Insects also developed more sensilla if they were fed on two foods of identical nutritional composition but with different added flavours (1 % tannic acid or amygdalin). Exposing locusts to synthetic foods for a single stadium did not cause any significant decrease in sensilla number. The results suggest that the number of sensilla that develop in a given sensory field is influenced by the variety of chemical stimuli experienced and the chemical complexity of the environment as provided by the presence of distinct individual sources of stimulation.
The First Peptide-Gated Ion Channel
Authors: Cottrell Glen A.
Published: April 2021

Patch-clamp experiments on the C2 neurone of Helix aspersa have shown that the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) directly gates a Na+ channel. The channel is amiloride-sensitive. Activation of this channel is responsible for the fast excitatory action of the peptide. Using primers based on amiloride-sensitive epithelial Na+ channels, a complete cDNA sequence (FaNaCh) was cloned and sequenced from a Helix library. The sequence is predicted to have just two membrane-spanning regions and a large extracellular loop. When expressed in Xenopus laevis oocytes, the channel responded to FMRFamide. Taken together, these data provide the first evidence for a peptide-gated ion channel. Comparison of the properties of the expressed FaNaCh with the native neuronal channel show small differences in the sensitivities to some drugs and in channel conductance. It is not yet clear whether the native channel is a homo-oligomer or comprises other subunits. The peptide FKRFamide is an effective antagonist of FMRFamide on the expressed and neuronal channels. Nucleotide sequences encoding similar channel proteins occur in neurones of species as dissimilar as man and Caenorhabditis elegans. Some channels are thought to be associated with mechano-sensation, at least one is a proton-gated channel and others may also be ligand-gated channels.
A Stereological Comparison of Villous and Microvillous Surfaces in Small Intestines of Frugivorous and Entomophagous Bats: Species, Inter-Individual and Craniocaudal Differences
Authors: Makanya A. N. , Maina J. N. , Mayhew T. M. , Tschanz S. A. , Burri P. H.
Published: April 2021

The extents of functional surfaces (villi, microvilli) have been estimated at different longitudinal sites, and in the entire small intestine, for three species of bats belonging to two feeding groups: insect- and fruit-eaters. In all species, surface areas and other structural quantities tended to be greatest at more cranial sites and to decline caudally. The entomophagous bat (Miniopterus inflatus) had a mean body mass (coefficient of variation) of 8.9 g (5 %) and a mean intestinal length of 20 cm (6 %). The surface area of the basic intestinal tube (primary mucosa) was 9.1 cm2 (10 %) but this was amplified to 48 cm2 (13 %) by villi and to 0.13 m2 (20 %) by microvilli. The total number of microvilli per intestine was 4×1011 (20 %). The average microvillus had a diameter of 89 nm (10 %), a length of 1.1 μm (22 %) and a membrane surface area of 0.32 μm2 (31 %). In two species of fruit bats (Epomophorus wahlbergi and Lisonycteris angolensis), body masses were greater and intestines longer, the values being 76.0 g (18 %) and 76.9 g (4 %), and 73 cm (16 %) and 72 cm (7 %), respectively. Surface areas were also greater, amounting to 76 cm2 (26 %) and 45 cm2 (8 %) for the primary mucosa, 547 cm2 (29 %) and 314 cm2 (16 %) for villi and 2.7 m2 (23 %) and 1.5 m2 (18 %) for microvilli. An increase in the number of microvilli, 33×1011 (19 %) and 15×1011 (24 %) per intestine, contributed to the more extensive surface area but there were concomitant changes in the dimensions of microvilli. Mean diameters were 94 nm (8 %) and 111 nm (4 %), and mean lengths were 2.8 μm (12 %) and 2.9 μm (10 %), respectively. Thus, an increase in the surface area of the average microvillus to 0.83 μm2 (12 %) and 1.02 μm2 (11 %) also contributed to the greater total surface area of microvilli. The lifestyle-related differences in total microvillous surface areas persisted when structural quantities were normalised for the differences in body masses. The values for total microvillous surface area were 148 cm2 g−1 (20 %) in the entomophagous bat, 355 cm2 g−1 (20 %) in E. wahlbergi and 192 cm2 g−1 (17 %) in L. angolensis. This was true despite the fact that the insect-eater possessed a greater length of intestine per unit of body mass: 22 mm g−1 (8 %) versus 9–10 mm g−1 (9–10 %) for the fruit-eaters.
Contractile Properties of Obliquely Striated Muscle from the Mantle of Squid (Alloteuthis Subulata) and Cuttlefish (Sepia Officinalis)
Authors: Milligan Brian J. , Curtin N. A. , Bone Quentin
Published: April 2021

The mechanical properties of obliquely striated muscle fibres were investigated using thin slices of mantle from squid Alloteuthis subulata and cuttlefish Sepia officinalis. Brief tetani or twitch stimuli were used as this pattern is likely to occur during jetting of the intact animal. The length–active force relationship for twitches and tetani (0.1 s, 50 Hz) was similar to that of vertebrate cross-striated fibres. Passive force at the length giving maximum tetanic force was 0.13±0.05P0 (mean ± S.E.M., N=6, where P0 is maximum isometric tetanus force) and increased steeply at longer lengths. Peak force in a brief isometric tetanus (0.2 s, 100–150 Hz) was 262±16 mN mm−2 cross-sectional area of wet tissue (N=6) for squid, and 226±19 mN mm−2 (N=7) for cuttlefish. The force–velocity relationship for isotonic shortening during twitches of squid mantle slices was a ‘double hyperbolic’ relationship as described for cross-striated fibres by Edman. Fitting Edman’s equation to the results gave: P*=1.18±0.07, Vmax=2.43±0.11Ltw s−1 and 1/G=0.69±0.13 (N=8), where P* is the intercept on the force axis expressed relative to Ptw, peak isometric twitch force, Vmax is the intercept on the velocity axis, Ltw is the length at which Ptw is produced and G is the constant expressing curvature. The large values of 1/G indicate that the force–velocity relationship is not very curved. Maximum power was produced during shortening at 0.45±0.03Ptw (N=8). Maximum power during twitch contraction was 18.3±1.7 mW g−1 wet mass or, expressed in relative units, (V/Vmax)(P/Ptw), where V is the velocity during shortening and P is the force during shortening, was 0.16±0.01 (N=8), which is higher than that of many cross-striated locomotor muscles.
Three Opsin-Encoding cDNAS from the Compound Eye of Manduca Sexta
Authors: Chase Michael R. , Bennett Ruth R. , White Richard H.
Published: April 2021

Three distinct opsin-encoding cDNAs, designated MANOP1, MANOP2 and MANOP3, were isolated from the retina of the sphingid moth Manduca sexta. MANOP1 codes for a protein with 377 amino acid residues. It is similar in sequence to members of a phylogenetic group of long-wavelength-sensitive arthropod photopigments, most closely resembling the opsins of ants, a praying mantis, a locust and the honeybee. MANOP2 and MANOP3 opsins have 377 and 384 residues respectively. They belong to a related group of insect visual pigments that include the ultraviolet-sensitive rhodopsins of flies as well as other insect rhodopsins that are also thought to absorb at short wavelengths. The retina of Manduca sexta contains three rhodopsins, P520, P450 and P357, with absorbance peaks, respectively, at green, blue and ultraviolet wavelengths. There is evidence that MANOP1 encodes the opsin of P520. We suggest that MANOP2 encodes P357 and that MANOP3, representing a class of blue-sensitive insect photopigments, encodes P450.
Defensive Production Of Quinoline By A Phasmid Insect (Oreophoetes Peruana)
Authors: Eisner Thomas , Morgan Randy C. , Attygalle Athula B. , Smedley Scott R. , Herath Kithsiri B. , Meinwald Jerrold
Published: April 2021

Adults and nymphs of the Peruvian stick insect Oreophoetes peruana (order Phasmatodea) have a pair of thoracic glands from which they discharge a malodorous fluid when disturbed. The secretion contains a single volatile component, quinoline. Quinoline has not been reported previously from an animal source. The compound proved repellent or topically irritant in assays with ants, spiders, cockroaches and frogs. O. peruana nymphs, at molting, do not extricate the shed cuticular lining of the glands, thereby managing not to lose their secretory supply when they cast their skin. They are able, as a consequence, to discharge secretion even while still teneral after molting.
Acid–Base Regulation in Tadpoles of Rana Catesbeiana Exposed to Environmental Hypercapnia
Authors: Busk Morten , Larsen Erik Hviid , Jensen Frank B.
Published: April 2021

Tadpoles of Rana catesbeiana were exposed to different levels of environmental hypercapnia. The acid–base regulatory response differed from that in adult amphibians in showing a high degree of pH compensation in the extracellular fluid (65–85 %) and complete compensation in the intracellular fluid (tail muscle and liver) within 24 h. Hypercapnia induced a massive transfer of HCO3− equivalents and Ca2+ from the tadpoles to the environment, which lasted some 4–6 h. Bicarbonate accumulated in the body fluids came mainly from internal buffer sources (probably CaCO3 in lime sacs and/or skin deposits). It is suggested that the large bicarbonate efflux from the animal is a consequence of the dissolution of CaCO3 stores and the delayed adjustment of bicarbonate-retaining mechanisms. Re-exposure of tadpoles to hypercapnia after 1–3 weeks of normocapnic recovery only affected transepithelial fluxes of acid–base equivalents marginally, suggesting that mobilisable CaCO3 stores were depleted during the first exposure to hypercapnia and that they were not refilled. The CaCO3 stores may normally be mobilised during the slowly developing internal hypercapnia that occurs during metamorphosis.
Visually Mediated Odometry in Honeybees
Authors: Srinivasan M. V. , Zhang S. W. , Bidwell N. J.
Published: April 2021

The ability of honeybees to gauge the distances of short flights was investigated under controlled laboratory conditions where a variety of potential odometric cues such as flight duration, energy consumption, image motion, airspeed, inertial navigation and landmarks were manipulated. Our findings indicate that honeybees can indeed measure short distances travelled and that they do so solely by analysis of image motion. Visual odometry seems to rely primarily on the motion that is sensed by the lateral regions of the visual field. Computation of distance flown is re-commenced whenever a prominent landmark is encountered en route. ‘Re-setting’ the odometer (or starting a new one) at each landmark facilitates accurate long-range navigation by preventing excessive accumulation of odometric errors. Distance appears to be learnt on the way to the food source and not on the way back.
Regulation Analysis Of Energy Metabolism
Authors: Brand Martin D.
Published: April 2021

This paper reviews top-down regulation analysis, a part of metabolic control analysis, and shows how it can be used to analyse steady states, regulation and homeostasis in complex systems such as energy metabolism in mitochondria, cells and tissues. A steady state is maintained by the variables in a system; regulation is the way the steady state is changed by external effectors. We can exploit the properties of the steady state to measure the kinetic responses (elasticities) of reactions to the concentrations of intermediates and effectors. We can reduce the complexity of the system under investigation by grouping reactions into large blocks connected by a small number of explicit intermediates – this is the top-down approach to control analysis. Simple titrations then yield all the values of elasticities and control coefficients within the system. We can use these values to quantify the relative strengths of different internal pathways that act to keep an intermediate or a rate constant in the steady state. We can also use them to quantify the relative strengths of different primary actions of an external effector and the different internal pathways that transmit its effects through the system, to describe regulation and homeostasis. This top-down regulation analysis has been used to analyse steady states of energy metabolism in mitochondria, cells and tissues, and to analyse regulation of energy metabolism by cadmium, an external effector, in mitochondria. The combination of relatively simple experiments and new theoretical structures for presenting and interpreting the results means that top-down regulation analysis provides a novel and effective way to analyse steady states, regulation and homeostasis in intricate metabolic systems.
Volume-Sensitive Transport Systems and Volume Homeostasis in Vertebrate Red Blood Cells
Authors: Cossins Andrew R. , Gibson John S.
Published: April 2021

Animal cells regulate their volume in the short term by controlling solute movements into and out of the cell. A suite of dissipative transport systems are involved which allow either regulatory volume increase (RVI) or decrease (RVD) responses depending upon the direction of the electrochemical gradients of the solutes. Many of these transporters have been identified at the molecular level and structure–function studies have identified transmembrane transport domains and cytoplasmic regulatory domains. In vertebrate red blood cells, protein phosphorylation appears to be central to the coordinated regulation of transporter activity. Inhibitors of protein phosphatases (PPs) cause inhibition of the K+/Cl− cotransporter (a transporter mediating RVD), whilst some inhibitors of protein kinases (PKs) cause activation. A sequence of potential phosphorylation sites appears to constitute a cascade of reactions leading to transporter regulation. PP and PK inhibitors have opposite effects on transporters mediating RVI responses, which is consistent with the coordinated but reciprocal regulation of transporters activated during both RVI and RVD using some common phosphorylation reactions. The transporters are sensitive to other stimuli including, in red blood cells, changes in and pH. These responses are also sensitive to PK/PP inhibitors and may involve elements of the volume-sensitive transduction pathway.
Imidacloprid actions on insect neuronal acetylcholine receptors
Authors: Buckingham S. D. , Lapied B. , Le Corronc H. , Grolleau F. , Sattelle D. B.
Published: April 2021

The neonicotinoid insecticide Imidacloprid acts at three pharmacologically distinct acetylcholine receptor (AChR) subtypes in the cockroach (Periplaneta americana) nervous system, but is ineffective on muscarinic receptors. Imidacloprid (3–100 μmol l−1) induced dose-dependent depolarizations at cockroach cercal afferent/giant interneurone synapses. These responses were insensitive to 20 μmol l−1 atropine but were completely blocked by the nicotinic antagonist mecamylamine (50 μmol l−1). Similarly, Imidacloprid-induced depolarizations of cultured cockroach dorsal unpaired median (DUM) neurones dissociated from the same (terminal abdominal) ganglion were also completely blocked by 100 μmol l−1 mecamylamine. However, two components of the response could be distinguished on the basis of their differential sensitivities to 0.1 μmol l−1 α-bungarotoxin (α-BTX), which selectively blocks AChRs with ‘mixed’ nicotinic/muscarinic pharmacology in this preparation. This indicates that Imidacloprid affects both AChRs sensitive to α-BTX and α-BTX-insensitive nicotinic acetylcholine receptors (nAChRs). Thus, in the cockroach, Imidacloprid activates α-BTX-sensitive synaptic nAChRs in giant interneurones, α-BTX-insensitive extrasynaptic nAChRs in DUM neurones, and a recently characterized DUM neurone ‘mixed’ AChR that is sensitive to both nicotinic and muscarinic ligands. Imidacloprid does not act on muscarinic acetylcholine receptors (mAChRs) present on DUM neurone cell bodies and at the cercal afferent/giant interneurone synapses. This study shows that Imidacloprid can act on pharmacologically diverse nAChR subtypes.
Measuring the angle of attack of beating insect wings: robust three-dimensional reconstruction from two-dimensional images
Authors: Willmott Alexander P. , Ellington Charles P.
Published: April 2021

A robust technique for determining the angle of attack of insect wings from film of free flight has to date proved elusive. This report describes the development of two new methods – the Strips and Planes techniques – which were designed to overcome some of the limitations experienced in previous studies. The accuracy and robustness of these novel methods were tested extensively using simulated hawkmoth wing outlines generated for a realistic range of wing positions and torsion. The results were compared with those from two existing methods – the Symmetry and Landmarks procedures. The performance of the latter technique will be strongly species-dependent; it could not be successfully applied to hawkmoth flight because of practical difficulties in obtaining suitable landmarks.

The Planes method was the least successful of the remaining techniques, especially during those phases of the wingbeat when the orientations of the two wings relative to the camera viewpoint were similar. The Symmetry and Strips methods were tested further to investigate the effects on their performance of introducing additional camber or wing motion asymmetry. The results showed clearly that the Strips method should be the technique of choice wherever the axis of wing torsion is close to the longitudinal axis of the wing. The procedure involves the experimenter matching a model wing divided into chordwise strips to the true wing outline digitized from high-speed film. The use of strips rather than the points digitized in previous studies meant that the analysis required only one wing outline to be digitized. Symmetry of motion between the left and right wings is not assumed.

The implications of requiring human input to the Strips method, as opposed to the strictly numerical algorithms of the alternative techniques, are discussed. It is argued that the added flexibility that this provides in dealing with images which have typically been recorded in suboptimal conditions outweighs the introduction of an element of subjectivity. Additional observations arising from the use of the Strips analysis with high-speed video sequences of hawkmoth flight are given.
The mechanics of flight in the hawkmoth Manduca sexta II. Aerodynamic consequences of kinematic and morphological variation
Authors: Willmott Alexander P. , Ellington Charles P.
Published: April 2021

Mean lift coefficients have been calculated for hawkmoth flight at a range of speeds in order to investigate the aerodynamic significance of the kinematic variation which accompanies changes in forward velocity. The coefficients exceed the maximum steady-state value of 0.71 at all except the very fastest speeds, peaking at 2.0 or greater between 1 and 2 m s−1. Unsteady high-lift mechanisms are therefore most important during hovering and slow forward flight. In combination with the wingtip paths relative to the surrounding air, the calculated mean lift coefficients illustrate how the relative contributions of the two halfstrokes to the force balance change with increasing forward speed. Angle of incidence data for fast forward flight suggest that the sense of the circulation is not reversed between the down- and upstrokes, indicating a flight mode qualitatively different from that proposed for lower-speed flight in the hawkmoth and other insects. The mid-downstroke angle of incidence is constant at 30–40 ° across the speed range. The relationship between power requirements and flight speed is explored; above 5 m s−1, further increases in forward velocity are likely to be constrained by available mechanical power, although problems with thrust generation and flight stability may also be involved.

Hawkmoth wing and body morphology, and the differences between males and females, are evaluated in aerodynamic terms. Steady-state force measurements show that the hawkmoth body is amongst the most streamlined for any insect.
Different Excitation–Contraction Coupling Mechanisms Exist in Squid, Cuttlefish and Octopod Mantle Muscle
Authors: Rogers C. M. , Nelson L. , Milligan B. J. , Brown E. R.
Published: April 2021

Excitation–contraction (EC) coupling was studied in central zone mantle muscle fibres of a squid (Alloteuthis subulata), a cuttlefish (Sepia officinalis) and an octopod (Eledone cirrhosa). Thin slices of muscle were used for twitch experiments and enzymatic isolation of single fibres for whole-cell patch-clamp studies. The current required for a supramaximal twitch response during direct stimulation of muscle slices was lower for squid than for cuttlefish. In squid, but not in cuttlefish, the current–response relationship was independent of slice thickness (range 0.1–0.5 mm). Twitches of squid and cuttlefish slices were reversibly abolished by removal of extracellular Ca2+. In squid, but not in cuttlefish, the current–response relationship was Na+-dependent, and in the absence of Na+ higher current strengths were required to generate a supramaximal response. In whole-cell voltage-clamp experiments on isolated muscle fibres from squid, cuttlefish and Eledone cirrhosa, a sustained inward current was recorded upon depolarisation. This current was blocked by 5 mmol l−1 Co2+ and suppressed by 10 μmol l−1 nifedipine. In squid, an additional inward fast-activating transient current was seen which was blocked by 2 μmol l−1 tetrodotoxin and depolarised holding potentials. The fast current represents a voltage-activated Na+ channel, and the slow currents represent L-type Ca2+ channels. We conclude that squid possess a specialised rapid EC coupling mechanism in central zone fibres that is absent in cuttlefish and Eledone cirrhosa.
Diving and Swimming Performance of White Whales, Delphinapterus Leucas: an Assessment of Plasma Lactate and Blood Gas Levels and Respiratory Rates
Authors: Shaffer S. A. , Costa D. P. , Williams T. M. , Ridgway S. H.
Published: April 2021

The white whale Delphinapterus leucas is an exceptional diver, yet we know little about the physiology that enables this species to make prolonged dives. We studied trained white whales with the specific goal of assessing their diving and swimming performance. Two adult whales performed dives to a test platform suspended at depths of 5–300 m. Behavior was monitored for 457 dives with durations of 2.2–13.3 min. Descent rates were generally less than 2 m s−1 and ascent rates averaged 2.2–3 m s−1. Post-dive plasma lactate concentration increased to as much as 3.4 mmol l−1 (4–5 times the resting level) after dives of 11 min. Mixed venous measured during voluntary breath-holds decreased from 79 to 20 mmHg within 10 min; however, maximum breath-hold duration was 17 min. Swimming performance was examined by training the whales to follow a boat at speeds of 1.4–4.2 m s−1. Respiratory rates ranged from 1.6 breaths min−1 at rest to 5.5 breaths min−1 during exercise and decreased with increasing swim speed. Post-exercise plasma lactate level increased to 1.8 mmol l−1 (2–3 times the resting level) following 10 min exercise sessions at swimming speeds of 2.5–2.8 m s−1. The results of this study are consistent with the calculated aerobic dive limit (O2 store/metabolic rate) of 9–10 min. In addition, white whales are not well adapted for high-speed swimming compared with other small cetaceans.
Endocardial Endothelium in the Avascular Heart of the Frog: Morphology and Role of Nitric Oxide
Authors: Sys Stanislas U. , Pellegrino Daniela , Mazza Rosa , Gattuso Alfonsina , Andries Luc J. , Tota Bruno
Published: April 2021

Endocardial endothelial morphology and the physiological modulatory role of nitric oxide (NO) were studied in an in vitro preparation of the working intact heart of the frog Rana esculenta, which lacks coronary vasculature and is thus devoid of a coronary vascular endothelium. En face confocal scanning laser microscopy of samples of perfused fixed hearts demonstrated the presence of NO synthase as a cytoplasmic constituent of the endocardial endothelial cells. Stroke volume (as a measure of performance in paced frog hearts) and stroke work (as an index of systolic function) increased by approximately 5 % after inhibition of the NO–cGMP pathway with 10−4 mol l−1NG-nitro-L-arginine methyl ester and by approximately 8 % after inhibition with 10−6 mol l−1 Methylene Blue. In contrast, stroke volume and stroke work decreased by approximately 22 % after activation of the NO–cGMP pathway with sodium nitroprusside (10−4 mol l−1), while 3-morpholinosydnonimine (5×10−8 to 10−5 mol l−1) caused a decrease of between 15 and 30 % and 8-bromo-cGMP (10−6 mol l−1) a decrease of approximately 8 %. These responses were significantly attenuated after exposure of the ventricular luminal to Triton X-100 (0.05 %, 0.1 ml), which itself increased performance (by over 10 %) without detectable morphological changes. These results show that the endocardial endothelium of Rana esculenta produces amounts of NO sufficient to modulate ventricular performance.
Differential Physiology and Morphology of Phasic and Tonic Motor Axons in a Crayfish Limb Extensor Muscle
Authors: Bradacs H. , Cooper R. L. , Msghina M. , Atwood H. L.
Published: April 2021

The main leg extensor muscle of the crayfish Procambarus clarkii is innervated by two excitatory motor axons (phasic and tonic) and by the common inhibitory axon. The axons and their terminals were investigated using vital fluorescent dyes, antibodies and electron microscopy. Correlative physiological observations were made using intracellular microelectrodes and focal ‘macro-patch’ electrodes. The excitatory axons innervate the muscle fibres more extensively than does the inhibitory axon. Striking morphological and physiological differences between the two excitatory axons were discerned. The tonic motor axon contains many mitochondria and has varicose junctional terminals; the phasic axon has fewer mitochondria and thin terminals. In freely moving animals, the tonic axon is very active, whereas the phasic axon is inactive but fires in brief bursts during walking. Throughout the muscle, tonic excitatory postsynaptic potentials (EPSPs) are very small at low frequencies and facilitate greatly at higher frequencies. The EPSPs of the phasic axon are larger at low frequencies and depress with maintained stimulation. At identified tonic terminals, quantal content at 1–10 Hz is very low, whereas at identified phasic terminals, quantal content is 50-to 200-fold greater. The results indicate that transmitter release is regulated differently at the synapses of the two axons.
Anguilliform Locomotion in an Elongate Salamander (Siren Intermedia): Effects of Speed on Axial Undulatory Movements
Authors: Gillis Gary B.
Published: April 2021

Many workers interested in the mechanics and kinematics of undulatory aquatic locomotion have examined swimming in fishes that use a carangiform or subcarangiform mode. Few empirical data exist describing and quantifying the movements of elongate animals using an anguilliform mode of swimming. Using high-speed video, I examine the axial undulatory kinematics of an elongate salamander, Siren intermedia, in order to provide data on how patterns of movement during swimming vary with body position and swimming speed. In addition, swimming kinematics are compared with those of other elongate vertebrates to assess the similarity of undulatory movements within the anguilliform locomotor mode. In Siren, most kinematic patterns vary with longitudinal position. Tailbeat period and frequency, stride length, Froude efficiency and the lateral velocity and angle of attack of tail segments all vary significantly with swimming speed. Although swimming speed does not show a statistically significant effect on kinematic variables such as maximum undulatory amplitude (which increases non-linearly along the body), intervertebral flexion and path angle, examination of the data suggests that speed probably has subtle and site-specific effects on these variables which are not detected here owing to the small sample size. Maximum lateral displacement and flexion do not coincide in time within a given tailbeat cycle. Furthermore, the maximum orientation (angle with respect to the animal’s direction of forward movement) and lateral velocity of tail segments also do not coincide in time. Comparison of undulatory movements among diverse anguilliform swimmers suggests substantial variation across taxa in parameters such as tailbeat amplitude and in the relationship between tailbeat frequency and swimming speed. This variation is probably due, in part, to external morphological differences in the shape of the trunk and tail among these taxa.
Digging in Sand Crabs (Decapoda, Anomura, Hippoidea): Interleg Coordination
Authors: Faulkes Zen , Paul Dorothy H.
Published: April 2021

Sand crabs (Decapoda, Anomura, Hippoidea) are highly specialised for digging into sand using their thoracic legs. Using video-recording and electromyography, we examined the digging leg movements of three species of sand crabs belonging to two families: Blepharipoda occidentalis (Albuneidae), Lepidopa californica (Albuneidae) and Emerita analoga (Hippidae). The digging patterns of all three species are similar. The ipsilateral legs 2 and 3 are tightly coupled and shovel sand forward from underneath the animal, whereas the movements of leg 4 are more variable, apparently stirring up sand and providing the purchase for rearward descent into the sand. The digging patterns of B. occidentalis and L. californica resemble each other more than either resembles that of E. analoga. In the albuneids, leg 4 cycles at the same frequency as legs 2 and 3, and both albuneid species switch gait from bilateral alternation to synchrony midway through digging. In E. analoga, right and left legs 2 and 3 always alternate. Legs 4 can cycle at about twice the frequency of legs 2 and 3, and they tend to move in bilateral synchrony during high-frequency leg movements (e.g. at the start of digging); their bilateral coupling becomes variable during low-frequency movements. Sand crab digging may have originated as a modified form of walking, but this behavioural innovation subsequently diverged in the sand crab superfamily.
Effects of Inhibition of Nitric Oxide Synthesis and Of Hypercapnia on Blood Pressure and Brain Blood Flow in The Turtle
Authors: Söderström Veronica , Nilsson Göran E. , Lutz Peter L.
Published: April 2021

In the mammalian brain, nitric oxide (NO) is responsible for a vasodilatory tonus as well as the elevation of cerebral blood flow (CBF) induced by hypercapnia. There have been few comparative studies of cerebral vasoregulation in lower vertebrates. Using epi-illumination microscopy in vivo to observe CBF velocity on the brain surface (cerebral cortex), we show that turtles (Trachemys scripta) exposed to hypercapnia (inspired ) displayed a 62 % increase in CBF velocity, while systemic blood pressure remains constant. Exposing turtles to a of 14.9 kPa caused an additional increase in CBF velocity, to 104 % above control values, as well as a 30 % increase in systemic blood pressure. The elevated CBF velocity during hypercapnia could not be blocked by a systemic injection of the NO synthase (NOS) inhibitor NG-nitro-L-arginine (L-NA). However, L-NA injection caused a temporary stop in CBF as well as a persistent increase in systemic blood pressure, suggesting that there is a NO tonus that is attenuated by the NOS inhibitor and that CBF is strongly dependent on this tonus, although compensatory mechanisms exist. Thus, although the cerebrovascular reaction to hypercapnia appeared to be NO-independent, the results suggest that there is a NO-dependent vasodilatory tonus affecting both cerebral and systemic blood circulation in this species
Innate Preferences for Flower Features in the Hawkmoth Macroglossum Stellatarum
Authors: Kelber Almut
Published: April 2021

The diurnal hawkmoth Macroglossum stellatarum is known to feed from a variety of flower species of almost all colours, forms and sizes. A newly eclosed imago, however, has to find its first flower by means of an innate flower template. This study investigates which visual flower features are represented in this template and their relative importance. Newly eclosed imagines were tested for their innate preferences, using artificial flowers made out of coloured paper or projected onto a screen through interference filters. The moths were found to have a strong preference for 440 nm and a weaker preference for 540 nm. The attractiveness of a colour increases with light intensity. The background colour, as well as the spectral composition of the ambient illumination, influences the choice behaviour. Blue paper disks against a yellowish background are chosen much more often than the same disks against a bluish background. Similarly, under ultraviolet-rich illumination, the preference for 540 nm is much more pronounced than under yellowish illumination. Disks of approximately 32 mm in diameter are preferred to smaller and larger ones, and a sectored pattern is more attractive than a ring pattern. Pattern preferences are less pronounced with coloured than with black-and-white patterns. Tests using combinations of two parameters reveal that size is more important than colour and that colour is more important than pattern.
Nervous Control of Male Sexual Drive in The Hermaphroditic Snail Lymnaea Stagnalis
Authors: De Boer P. A. C. M. , Jansen R. F. , Koene J. M. , Maat A. Ter
Published: April 2021

We studied the role of the prostate gland in determining the level of male sexual drive in the hermaphroditic pond snail Lymnaea stagnalis. Male sexual drive is high after a period of social isolation and decreases after copulation as a male. A positive correlation exists between the level of male sexual drive and the volume of the prostate gland. Like male sexual drive, the volume of the prostate gland increases during a period of social isolation and decreases after copulation as a male. Behavioural experiments demonstrated that animals with a lesion of the nerve that innervates the prostate gland (NP1) have a lower level of male sexual drive after social isolation than control animals. However, lesion of NP1 did not affect the increase in the volume of the prostate gland caused by social isolation. Extracellular recordings from NP1 in a semi-intact preparation show a change in firing pattern during an experimentally induced increase in prostate gland volume. The results indicate that NP1 serves as a nervous pathway for the male sexual drive. We propose a simple motivational model for male sexual behaviour in L. stagnalis in which the volume of the prostate gland sets the level of male sexual drive.
Sodium/Proton Antiporter In The Euryhaline Crab Carcinus Maenas: Molecular Cloning, Expression And Tissue Distribution
Authors: Towle David W. , Rushton Mary E. , Heidysch Doris , Magnani Jason J. , Rose Melanie J. , Amstutz Alice , Jordan Mark K. , Shearer Darcy W. , Wu Wen-Shu
Published: April 2021

Gill epithelial cells of euryhaline crustaceans demonstrate net inward transport of sodium ions, possibly via apical Na+/H+ antiporters, Na+/K+/2Cl− cotransporters or Na+ channels working in series with the basolateral Na++K+-ATPase. We have identified and sequenced the cDNA coding for a crustacean Na+/H+ antiporter, starting with mRNA isolated from gills of the euryhaline green shore crab Carcinus maenas. The complete 2595-base-pair cDNA includes an open reading frame coding for a 673-amino-acid protein. A search of GenBank revealed more than 20 high-scoring matches, all Na+/H+ antiporter sequences from mammalian, amphibian, teleost and nematode species. Injection of Xenopus laevis oocytes with cRNA transcribed from the cloned crab sequence substantially enhanced Na+-dependent H+ efflux from the oocytes. Analysis of crab tissue antiporter mRNA levels by semi-quantitative reverse transcription–polymerase chain reaction revealed that posterior and anterior gills of Carcinus maenas expressed this antiporter the most strongly, followed in decreasing order by skeletal muscle, hepatopancreas, hypodermis and heart. Hydropathy and transmembrane α-helix analysis suggested a 10-helix membrane-spanning topology of the antiporter protein. It is clear from this study that Carcinus maenas gills vigorously transcribe a gene coding for a Na+/H+ antiporter. Whether these gills also express a gene coding for an epithelial Na+ channel or Na+/K+/2Cl− cotransporter remains to be demonstrated.
Balancing Hypoxia and Hypothermia in Cold-Submerged Frogs
Authors: Tattersall G. J. , Boutilier R. G.
Published: April 2021

Many animals respond to hypoxic stress by selecting cooler environments, the so-called ‘behavioural hypothermia’ response. Amphibians overwintering in ice-covered ponds and lakes offer an ecologically relevant test of this response since they must choose between the confounding metabolic effects of profound hypothermia or hypoxia; thermal and chemical conditions can vary from 0 °C and normoxic at the ice–water interface to 4 °C and markedly hypoxic at depths of 2–4 m. To mimic such environmental conditions, we constructed an experimental chamber that enabled continuous electronic surveillance of an animal’s movement along a thermal gradient. When Rana temporaria pre-acclimated to 3.5 °C were placed in a normoxic thermal gradient ranging from 0.8 to 8 °C, they invariably favoured the warmer end of the chamber. Upon exposure to hypoxia, however, their preferred temperature shifted from a median of 6.8 °C ( 1 mmHg=0.133 kPa) to 1.9 °C . Metabolic rate measurements from animals exposed simultaneously to acute changes in water temperature and suggest that movement to colder conditions in hypoxia effects the greatest metabolic savings and prolongs the onset of a plasma lactacidosis.
An Auditory Interneurone Tuned to the Male Song Frequency In The Duetting Bushcricket Ancistrura Nigrovittata (Orthoptera, Phaneropteridae)
Authors: Stumpner A.
Published: April 2021

An auditory interneurone (AN1) of the bushcricket Ancistrura nigrovittata is described; it has a soma and dendrites in the prothoracic ganglion, an ascending axon and axon collaterals in the protocerebrum. As judged from morphological and physiological similarity, it is probably homologous to AN1 described in Tettigonia viridissima and to AN1 described in Gryllus bimaculatus. The occurrence and physiology of AN1 are not sex-specific. It receives predominant excitation between 12 and 16 kHz (male song frequency) and inhibition at lower frequencies and more strongly at higher frequencies. It shows optimum-type intensity/response curves. Frequency tuning and intensity-dependence compare well with female behaviour. Lesion experiments demonstrate that AN1 receives excitation and frequency-dependent inhibition from the soma-contralateral ear and inhibition from the soma-ipsilateral ear. The latter contributes to the clear left–right difference in its responses. AN1 does not obviously discriminate between temporal patterns of different behavioural effectivity. Its spiking, however, is coupled to the temporal pattern. It is hypothesized that AN1 may be involved in frequency processing by female A. nigrovittata.
The Changes in Power Requirements and Muscle Efficiency During Elevated Force Production in the Fruit Fly Drosophila Melanogaster
Authors: Lehmann Fritz-Olaf , Dickinson Michael H.
Published: April 2021

The limits of flight performance have been estimated in tethered Drosophila melanogaster by modulating power requirements in a ‘virtual reality’ flight arena. At peak capacity, the flight muscles can sustain a mechanical power output of nearly 80 W kg−1 muscle mass at 24 °C, which is sufficient to generate forces of approximately 150 % of the animal’s weight. The increase in flight force above that required to support body weight is accompanied by a rise in wing velocity, brought about by an increase in stroke amplitude and a decrease in stroke frequency. Inertial costs, although greater than either profile or induced power, would be minimal with even modest amounts of elastic storage, and total mechanical power energy should be equivalent to aerodynamic power alone. Because of the large profile drag expected at low Reynolds numbers, the profile power was approximately twice the induced power at all levels of force generation. Thus, it is the cost of overcoming drag, and not the production of lift, that is the primary requirement for flight in Drosophila melanogaster. By comparing the estimated mechanical power output with respirometrically measured total power input, we determined that muscle efficiency rises with increasing force production to a maximum of 10 %. This change in efficiency may reflect either increased crossbridge activation or a favorable strain regime during the production of peak forces.
Variability of leg Kinematics in Free-Walking Crayfish, Procambarus Clarkii, and Related Inter-Joint Coordination
Authors: Jamon Marc , Clarac François
Published: April 2021

The inter-joint coordination in leg 4 of the crayfish Procambarus clarkii was investigated while they travelled freely along straight paths. Video analysis of the kinematics of the leg’s three-dimensional motion, combined with a statistical method based on conjugate cross-correlation functions, showed stable inter-joint coordination in the leg kinematics. In particular, the inter-joint coordination involved a strong movement in the distal mero-carpopodite (M-C) joint occurring between the movements of the proximal thoraco-coxopodite and coxo-basal joints; thus, the leg extended during the swing phase and flexed during the stance phase. This synchronisation was mainly independent of global changes in the locomotor pattern induced by variation in speed or contralateral inter-leg coupling which occurred during free walking. The main changes in inter-joint coordination were found to be related to the appearance of a biphasic flexion/extension movement during each stroke of the step cycle when the leg retracted far backwards. This movement was observed more frequently in large animals and was therefore possibly related to changes in postural control. The functional role of this distal M-C joint movement in the leg motion is discussed.
Power Output From a Flight Muscle of the Bumblebee Bombus Terrestris: II. Characterization of the Parameters Affecting Power Output
Authors: Josephson Robert K.
Published: April 2021

Length–tension relationships and work output were investigated in the intact, dorso-ventral flight muscle of the bumblebee Bombus terrestris. The muscle is an asynchronous muscle. Like other asynchronous flight muscles, it has high resting stiffness and produces relatively low active force in response to tetanic stimulation. The muscle shows shortening deactivation and stretch activation, properties that result in delayed force changes in response to step changes in length, a phase lag between force and length during imposed sinusoidal strain and, under appropriate conditions, positive work output during oscillatory length change. Work loops were used to quantify work output by the muscle during imposed sinusoidal oscillation. The curves relating net work per cycle with muscle length, oscillatory strain and oscillatory frequency were all roughly bell-shaped. The work–length curve was narrow. The optimum strain for net work per cycle was approximately 3 %, which is probably somewhat greater than the strain experienced by the muscle in an intact, flying bumblebee. The optimum frequency for net work output per cycle was 63 Hz (30 °C). The optimum frequency for power output was 73 Hz, which agrees well with the normal wing stroke frequency if allowance is made for the elevated temperature (approximately 40 °C) in the thorax of a flying bumblebee. The optimal strain for work output was not strongly dependent on oscillation frequency. Resilience (that is the work output during shortening/work input during lengthening) for unstimulated muscle and dynamic stiffness (=Δstress/Δstrain) for both stimulated and unstimulated muscles were determined using the strain (3 %) and oscillation frequency (64 Hz) which maximized work output in stimulated muscles. Unstimulated muscle is a good energy storage device. Its resilience increased with increasing muscle length (and increasing resting force) to reach values of over 90 %. The dynamic stiffness of both stimulated and unstimulated muscles increased with muscle length, but the increase was relatively greater in unstimulated muscle, and at long muscle lengths the stiffness of unstimulated muscle exceeded that of stimulated muscle. Effectively, dynamic stiffness is reduced by stimulation! This is taken as indicating that part of the stiffness in an unstimulated muscle reflects structures, possibly attached cross bridges, whose properties change upon stimulation.
Power Output From a Flight Muscle of the Bumblebee Bombus Terrestris :III. Power During Simulated Flight
Authors: Josephson Robert K.
Published: April 2021

The work loop approach was used to measure mechanical power output from an asynchronous flight muscle, the dorso-ventral muscle of the bumblebee Bombus terrestris. Measurements were made at the optimum muscle length for work output at 30 °C and at a muscle temperature (40 °C) and oscillatory frequency (141–173 Hz, depending on the size of the animal) characteristic of free flight. Oscillatory strain amplitude was adjusted to maximize power output. There was much preparation-to-preparation variability in power output. Power output in the muscles with the highest values was slightly greater than 100W kg−1. It is argued that there are many experimental factors which might reduce measured power output below that in the living bumblebee, and no obvious factors which might lead to overestimates of muscle power. The conclusion is that flight muscle in the intact bumblebee can produce at least 100 W kg−1.