bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Cloning and Hormonal Control in the Ovary of Connexin 31.5 Mrna and Correlation with the Appearance of Oocyte Maturational Competence in Red Seabream
Authors: Choi Cheol Young , Takashima Fumio 
Published: April 2021

ABSTRACT
Gap junctions are aggregates of intercellular channels, composed of the protein connexin (Cx), between adjacent cells. This study examined whether, in the ovary of the red seabream Pagrus major, the connexin gene essential for the production of RNA and protein during the acquisition of oocyte maturational competence is active. Mixed primers for this reaction were designed on the basis of the high sequence homology of selected regions of known connexin genes. Polymerase-chain-reaction-amplified cDNA fragments generated by 3′ and 5′ rapid amplication of cDNA ends were combined to generate full-length cDNA sequences. The resulting 2400 base pair cDNA had an open reading frame encoding a polypeptide containing 275 amino acid residues (31493 Da; Cx31.5). Hydropathicity analysis of the predicted amino acid sequence indicated that red seabream Cx31.5 has four major hydrophobic regions and four major hydrophilic regions indicative of a topology similar to that of known connexins. Typical connexin consensus sequences were also observed in the first and second extracellular loops. During the acquisition of oocyte maturational competence, red seabream Cx31.5 mRNA transcription levels increased after treatment with gonadotropin-II. It is therefore proposed that expression of Cx31.5 contributes to the acquisition of oocyte maturational competence in this species.
Seasonal Changes in Energy and Water use by Verdins, Auriparus Flaviceps
Authors: Webster Marcus D. , Weathers Wesley W. 
Published: April 2021

ABSTRACT
We used the doubly labeled water (DLW) method to measure field metabolic rate (FMR) and water turnover during winter and summer in a very small (6.5 g) insectivorous desert passerine bird, the verdin (Auriparus flaviceps). Concurrently, we monitored weather conditions and used time–activity budget data of free-living birds and laboratory data on resting metabolic rate to construct time–activity laboratory (TAL) estimates of daily energy expenditure (DEE) and to partition the verdins’ energy budget into thermoregulatory, activity and basal components. The FMR of adult verdins was 33.6±0.9 kJ day−1 (mean ± S.E.M.; N=14) in winter and 22.8±0.45 kJ day−1 (N=7) in summer. FMR correlated negatively with the mean standard operative environmental temperature (Tes) prevailing during the measurement period. TAL analysis produced DEE estimates that corresponded on average to within −0.9±2.4 % of our DLW-measured FMR values (range of individual values −18.3 % to +14.3 %). Metabolic expeditures for cold defense were 19.5±2.1 % of DEE in winter (computed assuming substitution of exercise thermogenesis for thermoregulatory costs in active birds). In the summer, thermoregulatory costs amounted to 9.0±0.4 % of DEE for keeping warm and 1.0±0.1 % of DEE for keeping cool in the heat. Activity costs were 21.0±0.5 % of DEE in winter and 17.5±0.1 % of DEE in summer. The water efflux of nonbreeding adult verdins was 3.9±0.2 ml day−1 (624±22 ml kg−1 day−1) in summer (N=5) and 3.4±0.2 ml day−1 (498±26 ml kg−1 day−1) in winter (N=14). The water economy index (WEI; water efflux per unit FMR) of verdins was higher in summer (0.17±0.01 ml kJ−1) than in winter (0.10±0.01 ml kJ−1) and correlated negatively with mean Tes.
Bioconvective Dynamics: Dependence on Organism Behaviour
Authors: Czirók András , Jánosi Imre M. , Kessler John O. 
Published: April 2021

ABSTRACT
Bioconvection occurs when a macroscopic nonuniformity of the concentration of microbial populations is generated and maintained by the directional swimming of the organisms. This study investigated the properties of the patterns near the onset of the instability and later during its evolution into a fully nonlinear convection regime. In suspensions of the bacteria Bacillus subtilis, which tend to swim upwards in a gradient of oxygen concentration that they create by consumption, we discovered that the dominant wavelength at the onset of the instability is determined primarily by the cell density and is influenced only weakly by the fluid depth. This observation contrasts strongly with previous observations on the gravitactic alga Chlamydomonas nivalis, in which the opposite dependence was found. Considerable differences were also found in the long-term evolution of the convection patterns. These results demonstrate the existence of readily distinguishable types of bioconvection systems, even at early stages of the instability. The observed differences are clearly and causally correlated with disparate reasons for upward swimming by these micro-organisms, leading to different geometric distributions of the density of the suspension.
High Environmental Salinity Induces Memory Enhancement and Increases Levels of Brain Angiotensin-Like Peptides in the Crab Chasmagnathus Granulatus
Authors: Delorenzi Alejandro , Dimant Beatriz , Frenkel Lia , Nahmod Victor E. , Nässel Dick R. , Maldonado Héctor 
Published: April 2021

ABSTRACT
Previous work on the brackish-water crab Chasmagnathus granulatus demonstrated that an endogenous peptide similar to angiotensin II plays a significant role in enhancing long-term memory that involves an association between context and an iterative danger stimulus (context-signal memory). The present results show that this memory enhancement could be produced by moving crabs from brackish water to sea water (33.0 ‰) and keeping them there for at least 4 days. The possibility that such a facilitatory effect is due to osmotic stress is ruled out. Coincidentally, the level of angiotensin-II-like peptides in crab brain, measured by radioimmunoassay, increases with the length of exposure to sea water, reaching a significantly different level at the fourth day. The presence of angiotensin-II-like immunoreactive material in neural structures of the supraoesophageal and eyestalk ganglia was confirmed by immunohistochemical analysis. The results are interpreted as supporting the hypothesis that exposure to water of high salinity is an external cue triggering a process mediated by angiotensins that leads to enhanced memory in these crabs.
Morphometric Partitioning of Respiratory Surfaces in Amphioxus (Branchiostoma Lanceolatum Pallas)
Authors: Schmitz Anke , Gemmel Maj , Perry Steven F. 
Published: April 2021

ABSTRACT
The anatomical diffusing factors (ADFs), defined as the ratio of surface area to the thickness of the diffusion barrier, of possible respiratory surfaces of adult amphioxus (Branchiostoma lanceolatum) were evaluated using stereological methods. The ADF is greatest for the lining of the atrium and for the skin covering the segmental muscles. Calculation of the diffusing capacities for O2 revealed that the lining of the atrium makes up nearly 83 % of the entire diffusing capacity (8.86×10−3 μl min−1 mg−1 kPa−1 ) while the skin over the segmental muscles (9 %), the skin over the metapleural fold (4 %) and the gill bars (4 %) are of minor importance. The diffusing capacity of surfaces lying over coelomic cavities makes up 76 % of the whole diffusing capacity, which is consistent with the hypothesis that the coelom may function as a circulatory system for respiratory gases. Muscles have approximately 23 % of the entire diffusing capacity, indicating that they may be self-sufficient for O2 uptake. The diffusing capacity of the blood vessels in the gill bars is only 1 % of the total. Thus, the ‘gills’ lack significant function as respiratory organs in amphioxus (lancelets).
Does a Rigid Body Limit Maneuverability?
Authors: Walker Jeffrey A. 
Published: April 2021

ABSTRACT
Whether a rigid body limits maneuverability depends on how maneuverability is defined. By the current definition, the minimum radius of the turn, a rigid-bodied, spotted boxfish Ostracion meleagris approaches maximum maneuverability, i.e. it can spin around with minimum turning radii near zero. The radius of the minimum space required to turn is an alternative measure of maneuverability. By this definition, O. meleagris is not very maneuverable. The observed space required by O. meleagris to turn is slightly greater than its theoretical minimum but much greater than that of highly flexible fish. Agility, the rate of turning, is related to maneuverability. The median- and pectoral-fin-powered turns of O. meleagris are slow relative to the body- and caudal-fin-powered turns of more flexible fish.
The Optomotor Response and Spatial Resolution of the Visual System in Male Xenos Vesparum (Strepsiptera)
Authors: Pix Waltraud , Zanker Johannes M. , Zeil* Jochen 
Published: April 2021

ABSTRACT
The Strepsiptera are an enigmatic group of parasitic insects whose phylogenetic relationships are hotly debated. Male Strepsiptera have very unusual compound eyes, in which each of a small number of ommatidia possesses a retina of at least 60 retinula cells. We analysed the optomotor response of Xenos vesparum males to determine whether spatial resolution in these eyes is limited by the interommatidial angle or by the higher resolution potentially provided by the extended array of retinula cells within each ommatidium. We find that the optomotor response in Strepsiptera has a typical bandpass characteristic in the temporal domain, with a temporal frequency optimum at 1–3 Hz. As a function of spatial wavelength, the optomotor response is zero at grating periods below 12 ° and reaches its maximum strength at grating periods between 60 ° and 70 °. To identify the combination of interommatidial angles and angular sensitivity functions that would generate such a spatial characteristic, we used motion detection theory to model the spatial tuning function of the strepsipteran optomotor response. We found the best correspondence between the measured response profile and theoretical prediction for an irregular array of sampling distances spaced around 9 ° (half the estimated interommatidial angle) and an angular sensitivity function of approximately 50 °, which corresponds to the angular extent of the retina we estimated at the centre of curvature of the lens. Our behavioural data strongly suggest that, at least for the optomotor response, the resolution of the strepsipteran compound eye is limited by the ommatidial sampling array and not by the array of retinula cells within each ommatidium. We discuss the significance of these results in relation to the functional organisation of strepsipteran compound eyes, their evolution and the role of vision in these insects.
The Membrane Permeability Transition in Liver Mitochondria of the Great Green Goby Zosterisessor Ophiocephalus (Pallas)
Authors: Toninello A. , Salvi M. , Colombo L. 
Published: April 2021

ABSTRACT
Liver mitochondria from the great green goby Zosterisessor ophiocephalus (Pallas) normally exhibit bioenergetic variables (membrane potential 165±7 mV; respiratory control ratio 6.6±0.4; ADP/O ratio 1.85±0.8; means ± s.e.m., N=6) and activities of physiological transport systems (phosphate/proton symporter, adenine nucleotide antiporter, Ca2+ electrophoretic uniporter) comparable with those of rat liver mitochondria. When incubated in the presence of Ca2+ and an inducer agent such as phosphate, these mitochondria undergo a complete collapse of membrane potential accompanied by a large-amplitude swelling of the matrix, influx of sucrose from the incubation medium, release of endogenous Mg2+ and K+ (approximately 90 % of the total) and of preaccumulated Ca2+ and oxidation of endogenous pyridine nucleotides. All these phenomena, which are completely eliminated by cyclosporin A and inhibited with different efficacies by Mg2+ and spermine, demonstrate that the induction of the permeability transition in this type of mitochondria has characteristics similar to those described in rat liver mitochondria. In contrast, the requirement for very high Ca2+ concentrations (greater than 100 μmol l−1 ) for the induction of the permeability transition represents a very important difference that distinguishes this phenomenon in fish and mammalian mitochondria.
Open-Sea Migration of Magnetically Disturbed Sea Turtles
Authors: Papi F. , Luschi P. , Åkesson S. , Capogrossi S. , Hays G. C. 
Published: April 2021

ABSTRACT
Green turtles (Chelonia mydas) that shuttle between their Brazilian feeding grounds and nesting beaches at Ascension Island in the middle of the Atlantic Ocean are a paradigmatic case of long-distance oceanic migrants. It has been suggested that they calculate their position and the direction of their target areas by using the inclination and intensity of the earth’s magnetic field. To test this hypothesis, we tracked, by satellite, green turtles during their postnesting migration from Ascension Island to the Brazilian coast more than 2000 km away. Seven turtles were each fitted with six powerful static magnets attached in such a way as to produce variable artificial fields around the turtle that made reliance on a geomagnetic map impossible. The reconstructed courses were very similar to those of eight turtles without magnets that were tracked over the same period and in the previous year, and no differences between magnetically disrupted and untreated turtles were found as regards navigational performance and course straightness. These findings show that magnetic cues are not essential to turtles making the return trip to the Brazilian coast. The navigational mechanisms used by these turtles remain enigmatic.
The Pacemaker Activity Generating the Intrinsic Myogenic Contraction Of the Dorsal Vessel Of Tenebrio Molitor (Coleoptera)
Authors: Markou T. , Theophilidis G. 
Published: April 2021

ABSTRACT
Combined intracellular and extracellular recordings from various parts of the isolated dorsal vessel of Tenebrio molitor revealed some of the following electrophysiological properties of the heart and the aorta. (i) The wave of depolarization causing forward pulsation of the dorsal vessel was always transmitted from posterior to anterior, with a conduction velocity of 0.014 m s−1 in the heart and 0.001 m s−1 in the aorta when the heart rate was 60 beats min−1. (ii) There was no pacemaker activity in the aorta. (iii) The duration of the compound action potential in the aortic muscle depended on the duration of the pacemaker action potential generated in the heart. (iv) Isolated parts of the heart continued to contract rhythmically for hours, indicating powerful pacemaker activity in individual cardiac segments. (v) There was a direct relationship between action potential duration and the length of the preceding diastolic interval. (vi) The rhythmic wave of depolarization was dependent on the influx of Ca2+. (vii) The recovery of the electrical properties of myocardial cells that had been disrupted by sectioning was rapid. (viii) In hearts sectioned into two halves, the rhythmic pacemaker action potentials recorded simultaneously from the two isolated halves eventually drifted out of phase, but they had the same intrinsic frequency. In the light of these data, we discuss two alternative models for the generation of spontaneous rhythmic pumping movements of the heart and aorta.
Cues by which Portia Fimbriata, An Araneophagic Jumping Spider, Distinguishes Jumping-Spider Prey From Other Prey
Authors: Harland Duane P. , Jackson Robert R. 
Published: April 2021

ABSTRACT
Portia fimbriata from Queensland, Australia, is an araneophagic jumping spider (Salticidae) that includes in its predatory strategy a tactic (cryptic stalking) enabling it to prey effectively on a wide range of salticids from other genera. Optical cues used by P. fimbriata to identify the salticid species on which it most commonly preys, Jacksonoides queenslandicus, were investigated experimentally in the laboratory using odourless lures made from dead prey on which various combinations of features were altered. P. fimbriata adopted cryptic stalking only against intact salticid lures and modified lures on which the large anterior-median eyes were visible. Ordinary stalking was usually adopted when the lure did not have the anterior-median eyes visible. There was no evidence that cues from the legs of prey salticids influence the choice of stalking style of P. fimbriata, but cues from the legs do appear to influence strongly whether a prey is stalked at all. Cues from the cephalothorax and abdomen also influenced the stalking tendency, but to a lesser degree than cues from the legs. An algorithm to describe the perceptual processes of P. fimbriata when visually discriminating between salticid and non-salticid prey is discussed.
Combined Effects of Cold Exposure and Sub-Lethal Intestinal Parasites on Host Morphology and Physiology
Authors: Kristan Deborah M. , Hammond Kimberly A. 
Published: April 2021

ABSTRACT
Multiple, simultaneous demands elicit physiological and morphological responses that may jeopardize an animal’s ability to respond to future challenges, especially when resources are limited. Laboratory mice (Mus musculus) experimentally infected with an intestinal nematode (Heligmosomoides polygyrus) and then exposed to cold showed phenotypic plasticity of morphological and physiological responses. The parasitized mice maintained a similar body mass to the unparasitized mice but had less body fat and showed changes in some organ masses, a greater resting metabolic rate (RMR) and a diminished glucose uptake capacity both at the site of infection and in regions of the small intestine not occupied by parasites. Cold-exposed mice had a greater RMR, less body fat, a greater glucose transport capacity and showed changes in organ masses compared with mice maintained at room temperature. The responses to cold exposure were not affected by parasitism for any dependent variable. The costs of having parasites during simultaneous cold exposure included decreased energy reserves and greater maintenance requirements, which may then decrease the energy available for future expenditures, such as reproduction.
Foraging Energetics and Diving Behavior of Lactating New Zealand Sea Lions,Phocarctos Hookeri
Authors: Costa Daniel P. , Gales Nicholas J. 
Published: April 2021

ABSTRACTThe New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50°30′S, 166°17′E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO2 production) and water turnover were measured using the 18O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0±1.1 % (mean ± S.D.) and mean rate of CO2 production was 0.835±0.114 ml g−1 h−1, which provides an estimated mass-specific field metabolic rate (FMR) of 5.47±0.75 W kg−1. After correction for time on shore, the at-sea FMR was estimated to be 6.65±1.09 W kg−1, a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size.The mean maximum dive depth was 353±164 m, with a mean diving depth of 124±36 m. The mean maximum dive duration was 8.3±1.7 min, with an average duration of 3.4±0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg).Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O2 storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.
Reduced Enzymatic Antioxidative Defense in Deep-Sea Fish
Authors: Janssens Bernadette J. , Childress James J. , Baguet Fernand , Rees Jean-Francois 
Published: April 2021

ABSTRACT
Oxygen, while being an obligate fuel for aerobic life, has been shown to be toxic through its deleterious reactive species, which can cause oxidative stress and lead ultimately to cell and organism death. In marine organisms, reactive oxygen species (ROS), such as the superoxide anion and hydrogen peroxide, are generated within respiring cells and tissues and also by photochemical processes in sea water. Considering both the reduced metabolic rate of nektonic organisms thriving in the deep sea and the physico-chemical conditions of this dark, poorly oxygenated environment, the meso- and bathypelagic waters of the oceans might be considered as refuges against oxidative dangers. This hypothesis prompted us to investigate the activities of the three essential enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX) constitutive of the antioxidative arsenal of cells in the tissues of 16 species of meso- and bathypelagic fishes occurring between the surface and a depth of 1300 m. While enzymatic activities were detected in all tissues from all species, the levels of SOD and GPX decreased in parallel with the exponential reduction in the metabolic activity as estimated by citrate synthase activity. In contrast, CAT was affected neither by the metabolic activity nor by the depth of occurrence of the fishes. High levels of metabolic and antioxidative enzymes were detected in the light organs of bioluminescent species. The adjustment of the activity of SOD and GPX to the decreased metabolic activity associated with deep-sea living suggests that these antioxidative defense mechanisms are used primarily against metabolically produced ROS, whereas the maintenance of CAT activity throughout all depths could be indicative of another role. The possible reasons for the occurrence of such a reduced antioxidative arsenal in deep-sea species are discussed.