Vertebrate blood cell volume increases with temperature: implications for aerobic activity

Thermomechanical properties of bat and human red blood cells-Implications for hibernation

Hibernation is a widespread and highly efficient mechanism to save energy in mammals. However, one major challenge of hibernation is maintaining blood circulation at low body temperatures, which strongly depends on the viscoelastic properties of red blood cells (RBCs). Here, we examined at physiologically relevant timescales the thermomechanical properties of hundreds of thousands of individual RBCs from the hibernating common noctule bat (Nyctalus noctula), the nonhibernating Egyptian fruit bat (Rousettus aegyptiacus), and humans (Homo sapiens). We exposed RBCs to temperatures encountered during normothermia and hibernation and found a significant increase in elasticity and viscosity with decreasing temperatures. Our data demonstrate that temperature adjustment of RBCs is mainly driven by membrane properties and not the cytosol while viscous dissipation in the membrane of both bat species exceeds the one in humans by a factor of 15. Finally, our results show that RBCs from both bat species reveal a transition to a more viscous-like state when temperature decreases. This process on a minute timescale has an effect size that is comparable with fluctuations in RBC viscoelasticity over the course of the year, implying that environmental factors, such as diets, have a lower impact on the capability of RBCs to respond to different temperatures than general physical properties of the cell membrane. In summary, our findings suggest membrane viscoelasticity as a promising target for identifying mechanisms that could be manipulated to ensure blood circulation at low body temperatures in humans, which may be one first step toward safe synthetic torpor in medicine and space flight.

Multiple morphophysiological responses of a tropical frog to urbanization conform to the pace-of-life syndrome

The Pace-of-Life syndrome proposes that behavioural, physiological and immune characteristics vary along a slow-fast gradient. Urbanization poses several physiological challenges to organisms. However, little is known about how the health status of frogs is affected by urbanization in the Tropics, which have a faster and more recent urbanization than the northern hemisphere. Here, we analysed a suite of physiological variables that reflect whole organism health, reproduction, metabolic and circulatory physiology and leukocyte responses in Leptodactylus podicipinus. Specifically, we tested how leukocyte profile, erythrocyte morphometrics and germ cell density, as well as somatic indices and erythrocyte nuclear abnormalities differ throughout the adult life span between urban and rural populations. We used Phenotypic Trajectory Analysis to test the effect of age and site on each of the multivariate data sets; and a Generalised Linear Model to test the effect of site and age on nuclear abnormalities. Somatic indices, erythrocyte nuclear abnormalities, erythrocyte morphometrics and leukocyte profile differed between populations, but less so for germ cell density. We found a large effect of site on nuclear abnormalities, with urban frogs having twice as many abnormalities as rural frogs. Our results suggest that urban frogs have a faster pace of life, but the response of phenotypic compartments is not fully concerted.

Evolution of metabolic scaling among the tetrapod: Effect of phylogeny, the geologic time of class formation and uniformity of species within a class

The metabolic scaling in the animal has been discussed for over 90 years, but no consensus has been reached. Our analysis of 2,126 species of vertebrates reveals a significant allometric exponent heterogeneity. We show that classes of terrestrial vertebrates exhibit the evolution of metabolic scaling. Both the allometric coefficient "a" and the allometric exponent "b" change naturally, but differently depending on the geological time of group formation. The allometric coefficient "a" shows the measure of the evolutionary development of systems that forms resting metabolism in animals. Endothermic classes, such as birds and mammals, have a metabolic rate that is in an order of magnitude higher than that in ectothermic classes, including amphibians and reptiles. In the terrestrial vertebrate phylogeny, we find that the metabolic scaling is characterized by three main allometric exponent values: b = 3/4 (mammals), b > 3/4 (ectotherms, such as amphibians and reptiles), and b < 3/4 (birds). The heterogeneity of the allometric exponent is a natural phenomenon associated with the general evolution of vertebrates. The scaling factor decreases depending on both the external design and the size (birds vs mammals) of the animal. The metabolic rate and uniformity of species within a class increase as the geological start date of formation of the class approaches the present time. The higher the mass-specific standard metabolic rate in the class, the slower metabolic rate grows with increasing body size in this class. Our results lay the groundwork for further exploration of the evolutionary and ecological aspects of the development of metabolic scaling in animals. This article is protected by copyright. All rights reserved.

The evolution of red blood cell shape in fishes

The size and shape of red blood cells (RBCs) provide key information on life-history strategies in vertebrates. However, little is known about how RBC shape evolved in response to environmental factors, body size and the role of evolutionary rate. Here, we analysed RBC morphometrics in a set of Teleostei (bony fishes) and Elasmobranchii (sharks and rays) species testing the hypothesis that phylogenetic relationship explains species occupation of morphospace. We collected data on cell and nucleus area and volume, nucleus:cytoplasm ratio and shape factor for 65 species belonging to 28 orders. Then, we built phylomorphospaces separately for bony fish and sharks and rays. To test whether phylogenetic relationships predicted phenotypic similarity, we calculated multivariate phylogenetic signal. We also estimated the evolutionary rate of RBC shape for each node and tip using ridge regression. Finally, we tested whether habitat and body size influenced RBC shape using a PGLS. We found a significant phylogenetic signal in RBC shape for bony fish, but not sharks and rays. Saltwater teleost species were more clustered than freshwater ones in the phylomorphospace, suggesting clade disparity. Accordingly, the rate of evolution was highly heterogeneous, with significant decrease in Acanthopterygii. Neither habitat nor body size influenced RBC shape. In conclusion, RBC shape seems to have evolved in fishes in response to multiple selective pressures independent of life-history characters.

What determines the basal rate of metabolism?

The basal rate of metabolism (BMR) is the most reported estimate of energy expenditure in endotherms. Its principal determinant is body mass, but it also correlates with a variety of behavioral not determine basal rate, they are byproducts of the mechanisms that are its determinate. In mammals, mass-independent basal rate increases with muscle mass when it is&gt;40% of body mass. Then basal rates in mammals are≥100% of the values expected from mass. Mammals with muscle masses&lt;30% of body mass have lower basal rates, a diminished capacity to regulate body temperature, and often a reduced level of activity. At muscle masses&lt;42% of body mass, birds have body temperatures and basal rates higher than mammals with the same muscle mass. Their high basal rates derive from a high blood flow and mitochondrial density in their pectoral muscles. These factors also occur in the flight muscles of bats. Oxygen transport to the pectoral muscles of birds is facilitated by an increase in heart mass and hematocrit. This arrangement avoids transporting a large muscle mass to fuel flight, thereby reducing the cost of flight. Pectoral muscle masses&lt;9% of body mass correlate with a flightless condition in kiwis, rails, and ducks. Some fruit pigeons have basal rates as low as kiwis, while remaining volant. The mass-independent basal rates of endotherms principally reflect changes of muscle activity and mass. An increase in muscle mass may have contributed to the evolution of endothermy.

Response to formal comment on Myhrvold (2016) submitted by Griebeler and Werner (2017)

Griebeler and Werner offer a formal comment on Myhrvold, 2016 defending the conclusions of Werner and Griebeler, 2014. Although the comment criticizes several aspects of methodology in Myhrvold, 2016, all three papers concur on a key conclusion: the metabolism of extant endotherms and ectotherms cannot be reliably classified using growth-rate allometry, because the growth rates of extant endotherms and ectotherms overlap. A key point of disagreement is that the 2014 paper concluded that despite this general case, one can nevertheless classify dinosaurs as ectotherms from their growth rate allometry. The 2014 conclusion is based on two factors: the assertion (made without any supporting arguments) that the comparison with dinosaurs must be restricted only to extant sauropsids, ignoring other vertebrate groups, and that extant sauropsid endotherm and ectotherm growth rates in a data set studied in the 2014 work do not overlap. The Griebeler and Werner formal comment presents their first arguments in support of the restriction proposition. In this response I show that this restriction is unsupported by established principles of phylogenetic comparison. In addition, I show that the data set studied in their 2014 work does show overlap, and that this is visible in one of its figures. I explain how either point effectively invalidates the conclusion of their 2014 paper. I also address the other methodological criticisms of Myhrvold 2016, and find them unsupported.

Search for conserved amino acid residues of the α-crystallin proteins of vertebrates

[Formula: see text]-crystallin is the major eye lens protein and a member of the small heat-shock protein (sHsp) family. [Formula: see text]-crystallins have been shown to support lens clarity by preventing the aggregation of lens proteins. We performed the bioinformatics analysis of [Formula: see text]-crystallin sequences from vertebrates to find conserved amino acid residues as the three-dimensional (3D) structure of [Formula: see text]-crystallin is not identified yet. We are the first who demonstrated that the N-terminal region is conservative along with the central domain for vertebrate organisms. We have found that there is correlation between the conserved and structured regions. Moreover, amyloidogenic regions also correspond to the structured regions. We analyzed the amino acid composition of [Formula: see text]-crystallin A and B chains. Analyzing the occurrence of each individual amino acid residue, we have found that such amino acid residues as leucine, serine, lysine, proline, phenylalanine, histidine, isoleucine, glutamic acid, and valine change their content simultaneously in A and B chains in different classes of vertebrates. Aromatic amino acids occur more often in [Formula: see text]-crystallins from vertebrates than on the average in proteins among 17 animal proteomes. We obtained that the identity between A and B chains in the mammalian group is 0.35, which is lower than the published 0.60.

Inside the Redbox: applications of haematology in wildlife monitoring and ecosystem health assessment

Blood analyses have great potential in studies of ecology, ecotoxicology and veterinary science in wild vertebrates based on advances in human and domestic animal medicine. The major caveat for field researchers, however, is that the 'rules' for human or domestic animal haematology do not always apply to wildlife. The present overview shows the strengths and limitations of blood analyses in wild vertebrates, and proposes a standardisation of pre-analytical procedures plus some suggestions for a more systematic examination of blood smears to increase the diagnostic value of blood data. By discussing the common problems that field researchers face with blood variables, we also aim to highlight common ground enabling new researchers in the field to accurately collect blood samples and interpret and place their haematological findings into the overall picture of an ecological or eco-toxicological study. Besides showing the practicality and ecological relevance of simple blood variables, this study illustrates the suitability of blood samples for the application of cutting-edge analytical procedures for expanding the current repertoire of diagnostic tools in wildlife monitoring and ecosystem health assessment.