bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogenous excretion in the terrestrial carnivorous crab Geograpsus grayi: site and mechanism of excretion
Authors: Varley D. G. , Greenaway Peter 
Published: April 2021

ABSTRACT
The rate and mechanism of nitrogen excretion were examined in Geograpsus grayi. This species excretes waste nitrogen as gaseous NH3 in periodic bursts. The mean concentration of total ammonia ([NH3]+[NH4+]) in the primary urine during bursts of excretion (1.72 mmol l−1) was similar to that of haemolymph (2.07 mmol l−1) but was significantly lower (P&lt;0.005) than that of branchial fluid (80.6 mmol l−1).
The effects of ion exchange inhibitors on the apical membrane of the gill epithelium in Geograpsus grayi were examined. The presence of an amiloride-sensitive Na+/NH4+ exchanger was confirmed and a SITS-sensitive Cl− influx suggested Cl−/HCO3− exchange.
Thus, the site of nitrogenous excretion in this species is the branchial chamber, which is also the site of reprocessing of urine for ion regulation in other terrestrial crabs. Gaseous ammonia excretion is achieved by volatilisation of NH3 from the branchial fluid. High partial pressures of ammonia in the branchial fluid are produced by apical Na+/NH4+ exchange and elevation of the pH.
Cardiovascular adaptations enhance tolerance of environmental hypoxia in the crab Cancer magister
Authors: Airriess C. N. , McMahon B. R. 
Published: April 2021

ABSTRACT
Unrestrained crabs instrumented with probes for ultrasonic measurement of arterial haemolymph flow were subjected to 6 h of hypoxic exposure. During this interval, the inhalant O2 partial pressure was reduced in steps from 18 to 3 kPa. Measurement of haemolymph flow through all arteries leaving the heart allowed direct calculation of cardiac output, stroke volume and the distribution of cardiac output for both non-stressed and hypoxic animals.
Resting levels of cardiac output were low compared with previously reported values for this and other species of decapod crustaceans. During exposure to the most severe level of hypoxia tested, haemolymph flow through the anterior arteries decreased while flow through the posterior aorta and sternal artery increased by 55 % and 27 % respectively. Cardiac output increased from a control value of 9.8±1.6 to 11.9±1.2 ml kg−1 min−1 despite a decrease in heart-beat frequency. Scaphognathite beat frequency increased from 82.1±4.3 min−1 to more than 120 min−1 after 90 min of hypoxic exposure and remained at this level for the duration of the exposure period.
The decrease in haemolymph flow, via the anterior arteries, to the antero-dorsal region of the animal concurrent with an increase in flow to the posterior and antero-ventral regions, via the posterior aorta and sternal artery, implicates an active mechanism for redistribution of haemolymph flow during hypoxic exposure. The high rate of scaphognathite pumping, presumably to maximise O2 uptake during experimental hypoxia, was probably made possible by an increased blood supply to these organs, which are perfused by downstream branches of the sternal artery.
The effects of myomodulin and structurally related neuropeptides on skeletal neuromuscular transmission in the locust
Authors: Evans Peter D. 
Published: April 2021

ABSTRACTThe modulatory actions of myomodulin A on tension generated in the extensor-tibiae muscle of the locust hindleg by stimulation of the slow excitatory motoneurone (SETi) depend upon the frequency of stimulation. Myomodulin A has no consistent effect on the tension induced by the fast extensor motoneurone (FETi) or upon the myogenic rhythm present in the extensor. The effects of a range of structurally related neuropeptides have also been assessed. At low frequencies of SETi stimulation (1 Hz and below), the predominant modulatory effects are increases in the amplitude, contraction rate and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), these effects are superimposed upon an increase of maintained tension. The modulatory actions of myomodulin-like peptides show some similarities to and some differences from the modulatory actions of octopamine, proctolin and FMRFamide-like neuropeptides in this preparation, but are likely to be mediated via a distinct set of receptors. The results of the present study, taken together with the localization of myomodulin-like immunoreactivity in specific sets of neurones in the locust nervous system, suggest the presence of a novel modulatory system in insects that uses myomodulin-like neuropeptides. It also indicates that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.
Tunas as small as 207mm fork length can elevate muscle temperatures significantly above ambient water temperature
Authors: Dickson Kathryn A. 
Published: April 2021

ABSTRACT
Tunas (family Scombridae) maintain muscle temperatures (Tm) elevated significantly above ambient water temperature (Ta) by using vascular counter-current heat exchangers (retia mirabilia) to conserve metabolic heat generated by continuous contraction of red muscle fibers. Previous work has documented endothermy and both behavioral and physiological thermoregulation in tunas, but only individuals greater than approximately 1 kg body mass had been studied. The purpose of this study was to measure Tm and to examine heat exchanger morphology in smaller fish in order to determine the minimum size at which tunas can elevate Tm significantly above Ta. Measurements of Tm made immediately after capture in field-caught and laboratory-raised tunas (Euthynnus lineatus, Auxis thazard, A. rochei and Thunnus albacares) spanning a size range of 15.5–667mm fork length (FL) show that tunas 207mm FL (162.3g) and larger can elevate red muscle temperature by at least 3.0°C above Ta. E. lineatus, A. thazard and A. rochei of this size possess blood vessels serving the red muscle that are arranged as both lateral and central heat exchangers; the smallest tuna with evidence of a rete was a 108.5mm FL E. lineatus. In the ectothermic scombrid Scomberomorus sierra (108.7–132.0mm FL), Tm was elevated 0.2–0.5°C above Ta, and the greatest Tm elevation reported in any ectothermic species is only 2.7°C. Taken together, these data provide evidence that tunas greater than207mm FL are endothermic.
Circadian locomotor activity and its entrainment by food in the crayfish Procambarus clarki
Authors: De Miguel Francisco Fernández , Aréchiga Hugo 
Published: April 2021

ABSTRACT
The aim of our experiments has been to study the effect of light and food in the locomotor activity rhythm of the crayfish Procambarus clarki. Experiments were carried out under light:dark (LD) cycles of 12 h:12 h, under continuous darkness (DD) and under continuous light (LL). Under LD cycles, two peaks of activity were observed during the night phase of the cycle, while resting was characteristic of the day phase. Under DD or LL, it was possible to follow a free-running rhythm with a periodicity of 22.3±0.84 h in DD and 24.8±0.27 h in LL, typical of circadian rhythms of nocturnal species.
A single delivery of food in the day phase of the LD cycle resulted in an outburst of locomotor activity that lasted for several hours. In the ensuing days, an activity peak appeared in phase with the time of food delivery. The food-related activity peak could be followed for up to 2 weeks without food reinforcement. Under DD and LL, food induced an activity rhythm in previously arrhythmic animals. Here the period was longer than 24 h in DD (26.2±0.12 h) and shorter in LL (22.5±0.46 h). Together, these results strongly suggest that light and food may play a role entraining a locomotor activity rhythm in crayfish.
The relationship between oxygen uptake and ion loss in fish from diverse habitats
Authors: Gonzalez Richard J. , McDonald D. G. 
Published: April 2021

ABSTRACT
A recent examination of the relationship between O2 uptake and diffusive sodium loss in a freshwater fish showed that Na+ losses after exhaustive exercise exceeded those expected on the basis of , probably due to distortion of the paracellular tight junctions (the primary site of diffusive ion loss) and/or glomerular-type filtration caused by increased lamellar pressure. In the present study, an examination of this relationship in nine species of fish from diverse habitats supports this model. Under routine conditions, the rate of Na+ loss per unit of O2 consumed (termed the ion/gas ratio or IGR) was similar in all the species tested, averaging 61.6 pmol Na+ nmol−1 O2. After exhaustive exercise, the degree to which the IGR of each species increased relative to its routine levels (post-exercise IGR/routine IGR) was exponentially related to the relative rise in , i.e. greater rates of O2 uptake led to even greater ion losses. Further analysis revealed that, although naturally active species had the lowest proportionate increase in , by virtue of their high routine rates, they had the highest post-exercise rates of O2 uptake. In fact, there was an inverse correlation between post-exercise IGR and , i.e. species with low values lost more Na+ per mole of O2 taken up than did species with high ones. Thus, naturally active species, such as the common and golden shiner, were able to achieve higher rates of O2 uptake while avoiding high rates of ion loss. Surprisingly, species such as banded sunfish, yellow perch and smallmouth bass did not limit ion loss associated with exercise despite their apparent ability to do so. They demonstrated a strong ability to limit ion losses caused by a brief osmotic shock and by exposure to soft water (both of which distort tight junctions).
The Orientation of the E-Vector of Linearly Polarized Light Does not Affect the Behaviour of the Pigeon Columba Livia
Authors: Coemans M. A. J. M. , Vos Hzn J. J. , Nuboer J. F. W. 
Published: April 2021

ABSTRACT
Orientation with reference to the time-compensated sun-azimuth compass has been established for the homing pigeon Columba livia. Previous qualitative studies claim that pigeons are sensitive to the orientation of a polarizer and it has been suggested that these animals are able to use sky-light polarization as an indirect reference to the sun’s position when the latter is shielded from view. We report experiments which were undertaken to quantify the sensitivity of the homing pigeon to the orientation of linearly polarized light. The results of our initial experiments suggested that the animals responded to secondary cues. Further experiments were carried out to avoid such artefacts. Under circumstances where secondary cues were rigorously avoided, we were, however, not able to demonstrate any directional response that was caused by the E-vector orientation of the illumination. These results throw doubt on the suggested polarization-sensitivity of birds in general.
Flight Physiology of Neotropical Butterflies: Allometry of Airspeeds During Natural Free Flight
Authors: Dudley Robert , Srygley Robert B. 
Published: April 2021

ABSTRACTAirspeed measurements during natural free flight were made on a total of 270 neotropical butterflies representing 62 species. Morphological data were obtained from the same individuals for which airspeeds had been determined. Flight speed was positively correlated with body mass, thoracic mass and wing loading. Controlling for body mass, higher wing loadings were correlated with increased flight speed. Flight speed and wing aspect ratio were negatively correlated. No consistent correlations were found between airspeed and wing length, wing area or body length. Released butterflies and butterflies encountered in natural free flight did not differ substantially in flight speed allometry. The observed scaling of flight speeds was similar to that derived for a much smaller sample of butterflies flying in an insectary, although absolute values of flight speed were approximately three times higher in natural flight and correlation coefficients of allometric regressions were typically lower. These results suggest that butterfly airspeeds under natural conditions can reasonably be predicted from morphological measurements, and that studying flight in enclosed spaces preserves the allometry of flight speeds.
Bicuculline/Baclofen-Insensitive Gaba Response in Crustacean Neurones in Culture
Authors: Jackel C. , Krenz W.-D. , Nagy F. 
Published: April 2021

ABSTRACT
Neurones were dissociated from thoracic ganglia of embryonic and adult lobsters and kept in primary culture. When y-aminobutyric acid (GABA) was applied by pressure ejection, depolarizing or hyperpolarizing responses were produced, depending on the membrane potential. They were accompanied by an increase in membrane conductance. When they were present, action potential firing was inhibited.
The pharmacological profile and ionic mechanism of GABA-evoked current were investigated under voltage-clamp with the whole-cell patch-clamp technique. The reversal potential of GABA-evoked current depended on the intracellular and extracellular Cl− concentration but not on extracellular Na+ and K+. Blockade of Ca2+ channels by Mn2+ was also without effect. The GABA-evoked current was mimicked by application of the GABAA agonists muscimol and isoguvacine with an order of potency muscimol&gt;GABA&gt;isoguvacine. cis-4-aminocrotonic acid (CACA), a folded and conformationally restricted GABA analogue, supposed to be diagnostic for the vertebrate GABAC receptor, also induced a bicuculline-resistant chloride current, although with a potency about 10 times lower than that of GABA. The GABA-evoked current was largely blocked by picrotoxin, but was insensitive to the GABAA antagonists bicuculline, bicuculline methiodide and SR 95531 at concentrations of up to 100 μmol l−1. Diazepam and phenobarbital did not exert modulatory effects. The GABAB antagonist phaclophen did not affect the GABA-induced current, while the GABAB agonists baclophen and 3-aminopropylphosphonic acid (3-APA) never evoked any response.
Our results suggest that lobster thoracic neurones in culture express a chloride-conducting GABA-receptor channel which conforms to neither the GABAA nor the GABAB types of vertebrates but shows a pharmacology close to that of the novel GABAC receptor described in the vertebrate retina.
Detection of Airborne Sound by a Cockroach ‘Vibration Detector’: A Possible Missing Link in Insect Auditory Evolution
Authors: Shaw S. R. 
Published: April 2021

ABSTRACTExtracellular recordings from nerve 5 in metathoracic legs of Periplaneta americana disclose a sense organ that is extremely responsive to vibration but also detects sound (best response near 1.8 kHz) with a sensitivity similar to some insect auditory organs. The energy required from an auditory signal for a criterion response is similar or even smaller than for an optimal vibratory input. Responses originate in the subgenual organs (SGO) in the proximal tibiae, and cross-modal adaptation indicates that the same cells respond to both vibration and sound. Sound is picked up directly on some internal structure, not via sound-induced substratum vibration. Adaptation at different frequencies discloses no frequency-selectivity in the SGO. The nerve response is a burst of synchronized impulses at a frequency, fR, of approximately 300 Hz, that is practically invariant both with sound intensity and within the burst, suggesting that fR might represent some underlying resonance phenomenon, either of the SGO or of air in the tracheal system. The latter possibility is ruled out by observations made while the tracheae are perfused with He–O2. Similar responses can be recorded from the pro-and mesothoracic legs. Although Periplaneta is thought to be deaf and appears to ignore loud tones presented to the home colony, a more sensitive assay detects small leg movements in response to sound, confirming the presence of a functional auditory sense. The SGO is suspended from an expansion of the leg trachea, which may function to enhance sensitivity to vibration. This linkage preadapts the SGO to detect airborne sound transmitted in the tracheal system, and contact vibration may also stimulate the system in part by deforming the tracheae. It is proposed that auditory organs of crickets evolved from an ancestral SGO that already possessed dual responsiveness by subsequently developing effective vibration-isolating filters.
Hindlimb Kinematics During Terrestrial Locomotion In A Salamander (Dicamptodon Tenebrosus)
Authors: Ashley-Ross Miriam A. 
Published: April 2021

ABSTRACT
A quantitative study of hindlimb kinematics during terrestrial locomotion in a non-specialized salamander was undertaken to allow comparisons with limb movements in other groups of tetrapods. Five Dicamptodon tenebrosus were videotaped at 200 fields s−1 walking on a treadmill. Coordinates of marker points on the salamander’s midline, pelvic girdle and left hindlimb were digitized through at least three strides at both a walk (0.77 SVL s−1, where SVL is snout–vent length) and a trot (2.90 SVL s−1). Marker coordinates were used to compute kinematic variables summarizing trunk flexion, pelvic girdle rotation, femoral protraction/retraction and knee flexion/extension. The stride is characterized by uninterrupted trunk and pelvic girdle oscillation, femoral retraction throughout stance phase, and knee flexion in early stance followed by extension. Mean angular excursions are: trunk, 66°; pelvic girdle, 38.5°; pelvic girdle–femur, 106°; and knee, 65°. The hindlimb and pelvic girdle also show a complicated pattern of lateral movement related to knee flexion/extension and periods of support by the contralateral hindlimb during the step cycle. Dicamptodon shares the following features of the hindlimb step cycle with other tetrapod taxa: rotation of the pelvic girdle through a 30–40° arc, femoral retraction beginning simultaneously with and persisting throughout stance phase, flexion of the knee in early stance, and extension of the knee in late stance.
Haemolymph and Tissue Titres of Achetakinins in the House Cricket Acheta Domesticus: Effect of Starvation and Dehydration
Authors: Chung Jum Sook , Goldsworthy Graham J. , Coast Geoffrey M. 
Published: April 2021

ABSTRACT
Achetakinin-like immunoreactive material in tissues and haemolymph of adult male crickets was quantified by radioimmunoassay. Achetakinin-like material was found in the brain, suboesophageal ganglia and the thoracic and abdominal ganglia, but the largest amount was within the retrocerebral complex. A Ca2+-dependent release of achetakinin-like immunoreactive material was demonstrated from retrocerebral complexes incubated in vitro in saline containing a high concentration of K+. The concentration of achetakinin-like material in haemolymph from fed crickets was estimated to be 2.8 nmol l−1 and increased more than 10-fold in insects starved for 48 h without access to water. The presence of achetakinin-like material in haemolymph suggests that these peptides are released in vivo and function as circulating neurohormones.
Urea Transport By Hepatocytes And Red Blood Cells Of Selected Elasmobranch And Teleost Fishes
Authors: Walsh Patrick J. , Wood Chris M. , Perry Steve F. , Thomas Serge 
Published: April 2021

ABSTRACT
Although urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. This study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (Scyliorhinus canicula), Atlantic stingray (Dasyatis sabina), turbot (Scopthalmus maximus), redfish (Scianops ocellatus), gulf toadfish (Opsanus beta) and oyster toadfish (Opsanus tau). Urea appeared to be passively distributed in both tissues (i.e. there was no difference between plasma and tissue urea concentrations). Additionally, a number of in vitro experiments examining [14C]urea flux were performed. In red blood cells from all species except redfish, urea transport occurred via simple passive diffusion, but redfish red blood cells showed a small (25%) phloretin-sensitive uptake component. In hepatocytes of the two elasmobranch species (dogfish and stingray), urea efflux was also by simple passive diffusion. However, urea efflux in toadfish (both O. beta and O. tau) hepatocytes exhibited a marked phloretin-sensitivity, and O. beta hepatocytes were used in further experiments with other inhibitors and treatments. Urea transport in O. beta had a relatively high specificity for urea compared with the urea analogues acetamide, thiourea and N-methylurea, was unaffected by phloridzin and extracellular Na+ removal, and was not inhibited by physiological levels of glucose (0.5–10 mmol l−1). A phloretin-sensitive glucose transport, that was not inhibited by physiological levels of urea, was discovered in O. beta hepatocytes. The results are discussed in terms of patterns of species distribution and similarities between urea and glucose transport.
Buccalin-Like and Myomodulin-Like Peptides in the Stomatogastric Ganglion of the Crab Cancer Borealis
Authors: Christie Andrew E. , Hall Cassandra , Oshinsky Michael , Marder Eve 
Published: April 2021

ABSTRACT
The buccalins and myomodulins are families of peptides originally isolated and purified from the accessory radula closer (ARC) nerve–muscle system of the marine mollusc Aplysia californica (Cropper et al. 1987a,b, 1988). In A. californica, the buccalin family consists of 19 related peptides (buccalins A–S), each of which exhibits a homologous carboxyl terminal sequence, Phe-X-Gly-Gly-X-NH2 (Cropper et al. 1988; Miller et al. 1993a). A cDNA clone encoding a buccalin precursor polypeptide has recently been isolated (Miller et al. 1993a). This buccalin gene appears to be present as a single copy in the A. californica genome. The precursor peptide predicted from this gene encodes all 19 buccalin-like molecules, several in multiple copies.
Ion Transport in the Intestine of Anguilla Anguilla: Gradients and Translocators
Authors: Marvão P. , Emílio M. G. , Ferreira K. Gil , Fernandes P. L. , Ferreira H. Gil 
Published: April 2021

ABSTRACT
The transport of Na+, K+ and Cl− across the isolated epithelium of the eel intestine was studied using a combination of four experimental strategies: short-circuiting, measurements of intracellular potentials and ion concentrations, application of a variety of transport inhibitors and measurement of unidirectional fluxes with radioactive tracers. When short-circuited, the system performs a net transport of Cl− and Na+ towards the blood side, with a stoichiometry approaching 2, and a much smaller net transport of K+ towards the lumen. The system is totally driven by the sodium pump located in the basolateral barrier and the main coupling between the fluxes of the three ions is through the operation of a furosemide-sensitive transporter in the apical barrier, probably a 2Cl−/Na+/K+ symporter. The inhibitory effect of DIDS and picrylsulphonic acid on the short-circuit current, when added to the serosal side, suggests the presence of a sodium-dependent anionic shuttle located in the basolateral membrane. The short-circuit current is inhibited by H25, a non-specific inhibitor of the K+/Cl− symport, added to the serosal side. This effect occurs after a delay of at least 5 min and may result from the diffusion of the drug to the apical barrier, where it blocks the 2Cl−/Na+/K+ symport with much higher affinity.