A comparison of the response to induced exercise in red- and white-blooded Antarctic fishes

The physiological responses to forced exercise were studied in yellowbelly and marbled rockcod (Notothenia coriiceps and N. rossii), and the haemoglobinless icefish (Chaenocephalus aceratus), from blood samples obtained via indwelling catheters. The maximal exertion tolerable by N. coriiceps was 3–5 min, although N. rossii was not fully exhausted by this effort, and it proved difficult to elicit sustained maximal activity in C. aceratus. Arterial O₂ tension reflected the relative degree of exhaustion, showing a significant fall in the case of N. coriiceps, little change in N. rossii, and even a rise in C. aceratus as a result of hyperventilation. Such changes in the red-blooded species were not caused by altered O₂ carrying capacity, as there was no change in haematocrit. In Notothenia spp. the decrease in arterial pH was better correlated with a rise in arterial CO₂ tension than with blood lactate concentration, which is reflected in a modest net metabolic acid load. In contrast, the icefish showed an attenuated hypercapnia and a more pronounced lactacidosis, but an insignificant net metabolic acid load. Disturbance in ionoregulation following exercise was limited to an elevated [Cl⁻] in Notothenia, while circulating catecholamine levels remained unusually low in all specimens. The response to stress appears to reflect lifestyle and/or endemic speciation, rather than specific adaptations to the stenothermal environment. Accepted: 9 August 1996     

Plasma osmolarity, glucose concentration and erythrocyte responses of two Antarctic nototheniid fishes to acute and chronic thermal change

Haematocrit, haemoglobin concentration, plasma osmolarity and plasma glucose concentration of the Antarctic nototheniid fishes Pagothenia borchgrevinki and Trematomus bernacchii were monitored during 24 h periods of exposure to 3 and 6° C. The same haematological variables were also measured in P. borchgrevinki following a 5–6 week period of 4° C acclimation. The first plasma glucose measurements in acutely thermally‐stressed Antarctic nototheniids revealed a delayed hyperglycaemia which related well to the relatively slow stress‐related elevation of plasma cortisol in these species. Plasma osmolarity of both species was unchanged by acute 3° C exposure, but exhibited a delayed and transient increase during acute exposure to 6° C. Haematocrit was unaltered in T. bernacchii during the acute temperature increases but was elevated in the relatively active P. borchgrevinki . Following 5–6 weeks of warm‐acclimation (4° C) the plasma glucose concentration, haematocrit and haemoglobin concentration of P. borchgrevinki were not significantly different from fish at −1° C, but plasma osmolarity decreased toward the level found in temperate‐water teleosts.     

Mean corpuscular volume (MCV) as a measure of condition in birds

Haematological parameters, particularly haematocrit, are frequently used in assessing condition in birds. Mean corpuscular volume (MCV) overcomes some of the drawbacks associated with measuring haematocrits and therefore should be a better condition index. We investigated the relationship between these blood parameters and the breeding performances of great skuas Catharacta skua . As predicted from activity budgets of the sexes, male MCVs were significantly positively correlated with hatch date and the MCVs of both sexes were negatively correlated with the number of chicks fledged. No correlations existed between these breeding parameters and haematocrit. Since males provision females and chicks, they probably influence breeding performance via foraging abilities, whereas in females nutritional investment may be more important. This is the first study of a free-living/nondomesticated vertebrate population in which these kinds of relationship have been demonstrated and we conclude that MCV is a useful measure of condition.     

The role of adrenaline as a modulator of cardiac performance in two Antarctic fishes

The present work was performed to test the hypothesis that Antarctic teleosts rely mostly on cholinergic inhibition for autonomic modulation of the heart. The effects of adrenaline on the inotropic properties on paced, isometrically contracting muscle strips were examined in two distinct Antarctic teleosts, the haemoglobinless icefish Chaenocephalus aceratus and the red-blooded Notothenia coriiceps. All tissues examined revealed a negative force-frequency relationship. Under baseline conditions C. aceratus contracted with a force twice as great as that of N. coriiceps. While the degree to which ventricular tissues responded to adrenaline varied between species, adrenergic stimulation significantly increases myocyte contraction force in this group of fishes. Contraction and relaxation times were not significantly affected by adrenaline concentration while absolute rates of contraction were. Adrenergic stimulation does not enable tissues to achieve higher contraction frequencies, but is shown to be a potent modulator of contraction force.     

Neural network detected in a presumed vestigial trait: ultrastructure of the salmonid adipose fin

A wide variety of rudimentary and apparently non-functional traits have persisted over extended evolutionary time. Recent evidence has shown that some of these traits may be maintained as a result of developmental constraints or neutral energetic cost, but for others their true function was not recognized. The adipose fin is small, fleshy, non-rayed and located between the dorsal and caudal fins on eight orders of basal teleosts and has traditionally been regarded as vestigial without clear function. We describe here the ultrastructure of the adipose fin and for the first time, to our knowledge, present evidence of extensive nervous tissue, as well as an unusual subdermal complex of interconnected astrocyte-like cells equipped with primary cilia. The fin contains neither adipose tissue nor fin rays. Many fusiform actinotrichia, comprising dense striated macrofibrils, support the free edge and connect with collagen cables that link the two sides. These results are consistent with a recent hypothesis that the adipose fin may act as a precaudal flow sensor, where its removal can be detrimental to swimming efficiency in turbulent water. Our findings provide insight to the broader themes of function versus constraints in evolutionary biology and may have significance for fisheries science, as the adipose fin is routinely removed from millions of salmonids each year.     

Thin-blooded Antarctic fishes: a rheological comparison of the haemoglobin-free icefishes Chionodraco kathleenae and Cryodraco antarcticus with a red-blooded nototheniid, Pagothenia bernacchii

The icefishes (family Channichthyidae) comprise a unique group of teleost fishes endemic to Antarctic and sub-antarctic seas. All members of the family totally lack haemoglobin. Haematological parameters and viscosity were determined for blood from 11 specimens of two channichthyid species (Chionodraco kathleenae Regan, 1914; Cryodraco antarcticus Dollo, 1900), and 14 specimens of a red-blood Antarctic nototheniid species (Pagothenia bernacchii (Boulenger, 1902)), captured near the Italian research station at Terra Nova Bay, Ross Sea, Antarctica. Channichthyid blood contained only a small number of non-pigmented cells (10 000-40 000 cells μI^?1, depending on species) in contrast to nototheniid blood (360 000-450 000 cells μI^?1 in unstressed specimens). Blood viscosity was measured by cone plate viscometry over a range of shear rates (11.3-450s ^?1), at six temperatures between – 1.8°C and + 15°C. At the ambient Antarctic seawater temperature of – 1.8° C, and at low shear rate (22.5 s^?1), the viscosity of channichthyid blood was relatively low (3.99 ± 0.40 cP) compared with blood taken from unstressed P. bernacchii, which was about 25% more viscous (4.91 ± 0.59 cP). The viscosity of channichthyid blood was almost independent of shear rate, approximating an ideal Newtonian fluid, while the viscosity of nototheniid blood was much more dependent upon both shear rate and temperature, increasing sharply at low shear rates and low temperatures. Viscosity of nototheniid blood varied with haematocrit, which was in turn strongly influenced by stress. Blood samples taken from P. bernacchii under moderate stress induced by handling during acute caudal venepuncture had haematocrit values in the range 15–20% and viscosities of 8-l0cP, while undisturbed specimens sampled through a venous cannula yielded haematocrits of 8–10%. The viscosity of nototheniid plasma did not differ significantly from that of channichthyid whole blood or channichthyid plasma. The higher viscosity of nototheniid blood is attributable to cell content, and in stressed specimens possibly also to adrenergic swelling of erythrocytes. The absence of erythrocytes in channichthyid blood avoids the great increases in viscosity which are induced in corpusculate blood by sub-zero seawater temperatures.     

Use of erythrocyte indicators of health and condition in vertebrate ecophysiology: a review and appraisal

We review evidence for and against the use of erythrocyte indicators of health status and condition, parasite infection level and physiological stress in free‐living vertebrates. The use of indicators that are measured directly from the blood, such as haemoglobin concentration, haematocrit and erythrocyte sedimentation rate, and parameters that are calculated from multiple measured metrics, such as mean cell volume, mean cell haemoglobin content or mean cell haemoglobin concentration is evaluated. The evidence for or against the use of any given metric is equivocal when the relevant research is considered in total, although there is sometimes strong support for using a particular metric in a particular taxon. Possibly the usefulness of these metrics is taxon, environment or condition specific. Alternatively, in an uncontrolled environment where multiple factors are influencing a metric, its response to environmental change will sometimes, but not always, be predictable. We suggest that (i) researchers should validate a metricfres utility before use, (ii) multiple metrics should be used to construct an overall erythrocyte profile for an individual or population, (iii) there is a need for researchers to compile reference ranges for free‐living species, and (iv) some metrics which are useful under controlled, clinical conditions may not have the same utility or applicability for free‐living vertebrates. Erythrocyte metrics provide useful information about health and condition that can be meaningfully interpreted in free‐living vertebrates, but their use requires careful forethought about confounding factors.     

The concentration of glutathione in human erythrocytes is a heritable trait

Glutathione (GSH) is a ubiquitous, redox-active, small molecule that is critical to cellular and organism health. In red blood cells (RBCs), the influence of the environment (e.g., diet and lifestyle) on GSH levels has been demonstrated in numerous studies. However, it remains unknown if levels of GSH are determined principally by environmental factors or if there is a genetic component, i.e., heritability. To investigate this we conducted a twin study. Twin studies are performed by comparing the similarity in phenotypes between mono- and dizygotic twin pairs. We determined the heritability of GSH, as well as its oxidation product glutathione disulfide (GSSG), the sum of GSH equivalents (tGSH), and the status of the GSSG/2GSH couple (marker of oxidation status, E_hc) in RBCs. In our study population we found that the estimated heritability for the intracellular concentration of GSH in RBCs was 57 %; for GSSG it was 51 %, tGSH 63 %, and E_hc 70 %. We conclude that a major portion of the phenotype of these traits is controlled genetically. We anticipate that these heritabilities will also be reflected in other cell types. The discovery that genetics plays a major role in the innate levels of redox-active species in RBCs is paradigm shifting and opens new avenues of research in the field of redox biology. Inherited RBC antioxidant levels may be important disease modifiers. By identifying the relative contributions of genes and the environment to antioxidant variation between individuals, new therapeutic strategies can be developed. Understanding the genetic determinants of these inherited traits may allow personalized approaches to relevant therapies.     

Reduced alpha adrenergic mediated contraction of renal preglomerular blood vessels as a function of gender and aging

As human males age, a decline in baroreflex-mediated elevation of blood pressure occurs due, at least in part, to a reduction in alpha-1 adrenergic vasoconstrictor function. Alpha adrenergic constriction is mediated by guanosine triphosphate binding Protein (G Protein) coupled signaling pathways. Alpha-1 A/C, B, and D adrenergic receptor expressions, measured by GeneChip array, are not reduced during aging in renal blood vessels of male or female rats. Alpha-1 A GeneChip expression is greater, at all ages studied, in females than in males. Prazosin binding by alpha-1 adrenergic receptors is greater in young adult female rats than in young adult male rats; however, it is reduced with aging in both male and female rats. G alpha q GeneChip expression declines while expression of adrenergic receptor kinase (GRK2) and tyrosine phosphatases (TyrP) increase with aging in male rats. The declines in alpha-1 adrenergic receptor binding and G alpha q expression and also the increases in GRK2 and TyrP expression likely relate to the age-related decline of vasoconstriction in male rats. The information that the expression of alpha-1 A adrenergic receptors is greater in female rats and (GRK2) expression does not increase during aging could relate to the gender differences in vasoconstrictor function with aging. Gene therapy to ameliorate the age-related decline in renal function could possibly reduce the need for renal dialysis. Signaling pathways such as those reviewed herein may provide an outline of the molecular pathways needed to move toward successful renal gene therapy for aging individuals.     

Advances in understanding the impacts of global warming on marine fishes farmed offshore: Sparus aurata as a case study

Monitoring variations in proteins involved in metabolic processes, oxidative stress responses, cell signalling and protein homeostasis is a powerful tool for developing hypotheses of how environmental variations affect marine organisms' physiology and biology. According to the oxygen- and capacity-limited thermal tolerance hypothesis, thermal acclimation mechanisms such as adjusting the activities of enzymes of intermediary metabolism and of antioxidant defence mechanisms, inducing heat shock proteins (Hsps) or activating mitogen-activated protein kinases may all shift tolerance windows. Few studies have, however, investigated the molecular, biochemical and organismal responses by fishes to seasonal temperature variations in the field to link these to laboratory findings. Investigation of the impacts of global warming on fishes farmed offsore, in the open sea, can provide a stepping stone towards understanding effects on wild populations because they experience similar environmental fluctuations. Over the last 30 years, farming of the gilthead sea bream Sparus aurata (Linnaeus 1758) has become widespread along the Mediterranean coastline, rendering this species a useful case study. Based on available information, the prevailing seasonal temperature variations expose the species to the upper and lower limits of its thermal range. Evidence for this includes oxygen restriction, reduced feeding, reduced responsiveness to environmental stimuli, plus a range of molecular and biochemical indicators that change across the thermal range. Additionally, close relationships between biochemical pathways and seasonal patterns of metabolism indicate a connection between energy demand and metabolic processes on the one hand, and cellular stress responses such as oxidative stress, inflammation and autophagy on the other. Understanding physiological responses to temperature fluctuations in fishes farmed offshore can provide crucial background information for the conservation and successful management of aquaculture resources in the face of global change.     

Parallel swims as a means of intra- and interspecific assessment in stream fishes

Synopsis Several North American minnow species are known to engage in the action pattern parallel swimming, an activity that allows males competing for nests or nesting sites an opportunity to assess each other. These agonistic displays have been hypothesized to occur only between males of similar size. We provide evidence to support this hypothesis for two minnow species and a sucker species. Competition is strong both intra- and interspecifically for nest sites and we document the occurrence of interspecific parallel swims between three species.     

Age‐related changes in mean corpuscular volumes in patients without anaemia: An analysis of large‐volume data from a single institute

Although the mean corpuscular volume (MCV) has been associated with various diseases, these associations in relation to the age‐related trends in MCV remain unclear. Therefore, we used a dataset with over one million values to identify the relationship between ageing and MCV changes. All laboratory data obtained between November 1998 and November 2019 at Chungbuk National University Hospital were retrospectively collected. After excluding cases with missing values for individual complete blood count parameters, outlier MCV values, and ages less than 1 year and more than 88 years, 977,335 MCV values were obtained from 309,393 patients. Principal component analysis of blood components with ages and analysis of the median value changes for each blood component across decade‐wise age groups were conducted to identify relationships between ageing and changes in blood components. The median values of MCV showed gradual increments with age. The linear relationship for patients aged 1–25 years had a larger slope than that for patients aged 26–88 years. For MCV, the equation for patients aged 1–25 years was 0.40*(age) + 81.24 in females and 0.45*(age) + 79.58 in males. The equation for patients aged 26–90 years was 0.04*(age) + 88.97 in females and 0.06*age + 88.30 in males. Among patients aged >40 years, the MCV value was higher in men than in women. Analysis of a large dataset showed that the MCV gradually increased with age and the linear relationship differed between patients aged 1–25 and 26–88 years.     

Behavioural relevance of polarization sensitivity as a target detection mechanism in cephalopods and fishes

Aquatic habitats are rich in polarized patterns that could provide valuable information about the environment to an animal with a visual system sensitive to polarization of light. Both cephalopods and fishes have been shown to behaviourally respond to polarized light cues, suggesting that polarization sensitivity (PS) may play a role in improving target detection and/or navigation/orientation. However, while there is general agreement concerning the presence of PS in cephalopods and some fish species, its functional significance remains uncertain. Testing the role of PS in predator or prey detection seems an excellent paradigm with which to study the contribution of PS to the sensory assets of both groups, because such behaviours are critical to survival. We developed a novel experimental set-up to deliver computer-generated, controllable, polarized stimuli to free-swimming cephalopods and fishes with which we tested the behavioural relevance of PS using stimuli that evoke innate responses (such as an escape response from a looming stimulus and a pursuing behaviour of a small prey-like stimulus). We report consistent responses of cephalopods to looming stimuli presented in polarization and luminance contrast; however, none of the fishes tested responded to either the looming or the prey-like stimuli when presented in polarization contrast.     

Changing patterns of growth in a changing planet: How a shift in phenology affects critical life‐history traits in annual fishes

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Development of the scales in Lepisosteus as a model for scale formation in fossil fishes

The living holostean fish Lepisosteus and the closely related Atractosteus offer a unique opportunity to study the development and homology of the ganoine-covered scales typical of early groups of actinopterygian fishes. Unlike the living chondrostean Polypterus , the scales of lepisosteids lack dentine and thus the role of the dentine, epidermis and mesodermal mesenchyme can be compared. Formation of the 'preganoine' is shown for the first time in Lepisosteus. Initial results show that in Lepisosteus ganoine is formed on the inner surface of a cell layer, apparently mesenchymal in origin, proliferating deep to the epidermal basement membrane. If this is correct ganoine in Lepisosteus is mesodermal and its formation has changed significantly from the pattern in the closely related fossil Semionotidae where dentine is present and is presumably involved in ganoine formation. The canals of Williamson in early fossil fishes were formed by migrating cells that played a major role in bone morphogenesis. The Lepisosteidae offer a unique opportunity to study these cells in a living vertebrate.     

Peroxide-triggered erythrocytes haemolysis as a model for the study of oxidative damage in marine fishes

The haemolysis of sea bass Dicentrarchus labrax red blood cells (RBC) was initiated by tert -butyl-hydroperoxide (t-BHP). The onset of the haemolytic process was accelerated by increasing t-BHP concentration. This process was preceded by a drop in the RBC glutathione content followed by the production of lipid peroxidation products. Also t-BHP induced DNA fragmentation in RBC nuclei as measured by COMET assay. The addition of the antioxidant Trolox C® dose-dependently delayed the onset of both lipid peroxidation and haemolysis, and protected GSH stores against t-BHP-induced depletion. DNA fragmentation was also pre-vented by Trolox C®. These results indicate that t-BHP induces haemolysis in sea bass RBC through the induction of oxidative stress. Such a simple model could prove useful for both fundamental and applied studies on marine fish antioxidant mechanisms.     

Strip counts as a means of determining densities and habitat utilization patterns in lake fishes

Synopsis The strip count method of determining fish densities was investigated for a small lake in a series of inshore sites that differed in their physical and biological characteristics and in the communities of fishes present. Overall total numbers of fish, number of species, ratio of commonest to total species, and 2nd commonest to total species, were investigated. Counts were made during time of the feeding peaks.Repeatability of the method was tested by series of five traverses at 10-minute intervals and was good both for total numbers of fish and ratio of commonest species to total fish. However, it varied with the habitat type, being excellent for small semi-isolated weedy sites, good for gravel-bottom sites, but only fair in open sandy bays where the strip was laid in the middle of an extensive area of homogeneous habitat.Series of comparative counts made (a) between morning and afternoon on the same day and, (b) between successive mornings, to determine how constant populations were between these time intervals, proved to be within the same general range but were significantly different by the Mann Whitney U test at the = 0.05 level.In small lakes the strip count method proves to have considerable potential in the study of habitat specializations, taxocene structures, and relative abundances.     

Jetski-based plankton towing as a new method of sampling larval fishes in shallow marine habitats

I tested jetski-based plankton towing as a new method of sampling larval fishes in a shallow marine environment in warm temperate South Africa. Larval fishes were collected by towing a stainless-steel ring net behind a three-man jetski. The sampling technique was designed and tested to overcome problematic sampling of shallow sandy beach surf zones and the adjacent, shallow nearshore immediately seaward of the surf zone (behind the breaker line) with the same type of equipment. The composition, density, stage of development, estuary association, and length frequency of larval fish catches obtained by the new sampling method in the surf zone and in the adjacent shallow nearshore were compared. The success of the technique was evaluated by determining the extent of replication of known trends observed in other surf studies in the same climatic region of South Africa using either a seine or pushnet. Preflexion and postflexion larval fishes were collected. Larvae of the family Sparidae dominated the catches. Trends in catch composition, estuary association, and length frequency of the larvae were similar to those found in other studies of warm temperate South African surf zones. Density of larvae varied depending on the type of equipment used, although these results are tentative given the subjectivity of calculation of the water volume sampled and the extent of nursery use by larvae in the habitats sampled in each study. Increased towing times are recommended. Jetski-based plankton towing is a useful alternative technique for sampling larval fishes in shallow habitats and can easily be applied in surf zones, shallow nearshore areas, and estuaries. The technique greatly increases sampling agility in previously problematic sampling areas.     

The Utility of the Swine Model to Assess Biological Rhythms and Their Characteristics during Different Stages of Residence in a Simulated Intensive Care Unit: A Pilot Study

The purpose of this pilot study was to explore the utility of the mammalian swine model under simulated intensive care unit (sICU) conditions and mechanical ventilation (MV) for assessment of the trajectory of circadian rhythms of sedation requirement, core body temperature (CBT), pulmonary mechanics (PM) and gas exchange (GE). Data were collected prospectively with an observational time-series design to describe and compare circadian rhythms of selected study variables in four swine mechanically ventilated for up to seven consecutive days. We derived the circadian (total variance explained by rhythms of τ between 20 and 28?h)/ultradian (total variance explained by rhythms of τ between 1 and <20?h) bandpower ratio to assess the robustness of circadian rhythms, and compare findings between the early (first 3 days) and late (subsequent days) sICU stay. All pigs exhibited statistically significant circadian rhythms (τ between 20 and 28?h) in CBT, respiratory rate and peripheral oxygen saturation, but circadian rhythms were detected less frequently for sedation requirement, spontaneous minute volume, arterial oxygen tension, arterial carbon dioxide tension and arterial pH. Sedation did not appear to mask the circadian rhythms of CBT, PM and GE. Individual subject observations were more informative than group data, and provided preliminary evidence that (a) circadian rhythms of multiple variables are lost or desynchronized in mechanically ventilated subjects, (b) robustness of circadian rhythm varies with subject morbidity and (c) healthier pigs develop more robust circadian rhythm profiles over time in the sICU. Comparison of biological rhythm profiles among sICU subjects with similar severity of illness is needed to determine if the results of this pilot study are reproducible. Identification of consistent patterns may provide insight into subject morbidity and timing of such therapeutic interventions as weaning from MV.     

Cover as a simple predictor of biomass for two shrubs in Tibet

Knowledge of the quantitative relationship between plant cover and its corresponding biomass for shrubs is not well known, especially for those on the Tibetan Plateau. Based on investigations of 35 sites, 90 plots and 95 standard individuals for two typical shrub species (Rhododendron nivale Hook. f. and Sophora moorcroftiana (Benth.) Baker) across Tibet, we developed allometric models for biomass estimation from measurements of crown diameter and/or height. We found that the parameters of crown projection area (CPA), height and their product (volume) were all significantly (p < 0.01) correlated with dry mass of different organs for both species at individual level. The CPA rather than volume best predicted aboveground dry mass. This is because that the bulk density declined significantly with increasing plant height, leading to the inappropriateness for plant height itself being employed as a parameter in biomass estimation, especially for shrubs in smaller size groups. At community level, cover was tightly correlated with the aboveground, belowground and total biomass (R² = 0.97–0.99). Therefore, biomass for the two shrubs can be simply estimated by measuring plant cover, which enables rapid estimation of shrubland carbon stock at large scales by using satellite data and repeated experiments over time. This non-destructive method using cover to estimate shrub biomass can be applied not only in arid ecosystems but also in alpine or subalpine environment.