Bioenergetics of Arctic marine poikilothermic animals

The yearly energy balance has been calculated for the first time for the polar species Arctic flounder Liopsetta glacialis at temperatures of its habitat. Despite the lower rates of the constructive metabolism, the energy metabolic rate during the somatic growth and gonad development was higher compared to warmwater species of flatfishes, so that the K ₂ coefficient was higher in all age groups. Functional relationships between constructive metabolism and energy metabolism in poikilothermic animals have been demonstrated.     

Equation of state and life span of poikilothermic animals

An equation of state of a living organism that corresponds to the Kleiber's empirical dependence has been found using the conditions of entropy and energy balance. Life span of animals has been calculated using the equation obtained and it was found to depend inversely on metabolism intensity.     

The rate of development in poikilothermic animals calculated in astronomical and relative time units

• 1.1.|The problem of comparing the rate of development of various species of poikilothermic animals, using the astronomical time units and relative units of development duration (in the unit of τ₀ — the duration of one mitotic cycle in the period of synchronous cleavage divisions) is considered, a number of fish and amphibian species is taken by example.
• 2.2.|A dimensionless criterion of the relative rate of development (CRR) is proposed. In closely related animal species and genera in the early development CCR = 1, and only later on do some species begin to develop faster than the others, as it takes them less time (measured in a lesser number of τ₀) to pass the identical developmental periods (τ_n).
• 3.3.|In more distant animal groups the same name but not identical developmental periods have different relative duration from the early stages of development, due to gastrulation beginning at different stages of the blastulation, i.e. as a result of heterochronies.

     

The notion of ecological optimum and the determination of this optimum in freshwater poikilothermic animals

The notion of ecological optimum is discussed as related to aquatic poikilothermic animals. Publications on the analysis of the influence of thermal factor on vital functions of invertebrates with the subsequent statement of the general pattern of optimal environmental factors are reviewed. It is concluded that the optimum includes not simply the range of the factor's values on the tolerance curve or the dose of the factor providing for the most favourable life conditions, but the oscillations of the factor within the optimum range, i.e., the astatic optimum, as termed by Prof. A.S. Konstantinov. It is shown, by the example of the influence on organisms and populations of zooplankton of stepwise changes of temperature, increased doses of mineral phosphorus, and low-power laser radiation, that to determine the optimum of an environmental factor it is important to use not only its absolute values and the parameters of cyclic changes, but also the presence or absence of stepwise changes, also determining the direction of the dynamics and the duration of influence of the "dose", as well as the presence and character of the after-effects (inertial action) of the factor on organisms. It is suggested to introduce more detailed and concrete definitions to distinguish between the "static" and then "dynamic" optimum. The former includes the range of optimum values of the factor on the tolerance scale and the "dose" of every factor matching the organism's requirements and providing for the maximum favourable life conditions. The latter includes optimum parameters of cyclic changes (frequency and amplitude) of the factor, along with determining their position in the range of optimum values (at its lower, middle, or upper part), the presence or absence of stimulating effects of stepwise changes of the factor, including the duration of influence of some "dose" of the factor and the order of alteration of the higher and the lower values (dynamics direction), as well as the presence or absence and the character of after-effects (inertial action) of the factor on the organism.     

Mechanisms of cold pain

Avoidance of cold pain is an important survival mechanism. Intriguingly, whilst cooling can cause numbness, damage sensing mechanisms still seem to operate at low temperatures, and pain can be perceived from cooled damaged tissue. Recent studies have identified two cold-activated transient receptor potential (TRP) channels present in sensory neurons as transducers of cold stimuli. TRPM8 seems to mediate responses to cooling whilst TRPA1 is activated, possibly indirectly, by more extreme cold conditions. The existence of cold-responsive neurons that do not express these channels suggests that other transducers of cold stimuli remain to be discovered. Subsequent action potential electrogenesis and probably propagation from sensory neurons innervating cold tissues depends upon the presence of Na(v)1.8, the sole voltage-gated sodium channel that fails to inactivate at low temperatures. This may explain the remarkable specificity of Na(v)1.8 expression in nociceptive neurons, where it plays an important role in pain pathways.     

Mechanisms of salinity tolerance in plants

The mechanisms of salt stress response and tolerance have eluded definition despite reasonable success in defining their physiological manifestations. In this review, we consider the integrated salt metabolism of plants, essentially as a problem in meganutrient physiology. Two critical aspects of cellular and organismal metabolism are given particular attention—those involved in the control and integration of Na⁺ acquisition and allocation in plants and those involved in readjustment of other aspects of metabolism, especially those involving carbon as a resource.     

Mechanisms of temporary adhesion in benthic animals

Adhesive systems are ubiquitous in benthic animals and play a key role in diverse functions such as locomotion, food capture, mating, burrow building, and defence. For benthic animals that release adhesives, surface and material properties and external morphology have received little attention compared to the biochemical content of the adhesives. We address temporary adhesion of benthic animals from the following three structural levels: (a) the biochemical content of the adhesive secretions, (b) the micro‐ and mesoscopic surface geometry and material properties of the adhesive organs, and (c) the macroscopic external morphology of the adhesive organs. We show that temporary adhesion of benthic animals is affected by three structural levels: the adhesive secretions provide binding to the substratum at a molecular scale, whereas surface geometry and external morphology increase the contact area with the irregular and unpredictable profile of the substratum from micro‐ to macroscales. The biochemical content of the adhesive secretions differs between abiotic and biotic substrata. The biochemistry of the adhesives suitable for biotic substrata differentiates further according to whether adhesion must be activated quickly (e.g. as a defensive mechanism) or more slowly (e.g. during adhesion of parasites). De‐adhesion is controlled by additional secretions, enzymes, or mechanically. Due to deformability, the adhesive organs achieve intimate contact by adapting their surface profile to the roughness of the substratum. Surface projections, namely cilia, cuticular villi, papillae, and papulae increase the contact area or penetrate through the secreted adhesive to provide direct contact with the substratum. We expect that the same three structural levels investigated here will also affect the performance of artificial adhesive systems.     

线虫耐寒性研究进展

对于分布在温带和寒带的线虫,它们只有战胜冬季寒冷的挑战,才能有利于种群的存在与发展。因此,耐寒性是线虫生物学研究中不可忽视的内容。综述了关于线虫在低温胁迫下的耐寒性测定方法、耐寒对策及耐寒机制等方面的研究进展。线虫的耐寒性和昆虫一样,可通过过冷却点和低温存活率两种指标进行评价,但在具体的实验方法上,线虫耐寒性研究有其不同之处。线虫的耐寒对策和耐寒机制具有多样化。耐寒对策主要有耐冻和避冻,二者能共同渗透于线虫的耐寒过程中。耐寒机制包括特殊发育阶段的形成、低温驯化作用、低分子量抗冻物质的聚集、以及高分子量抗冻蛋白和热休克蛋白的产生,等等。此外,还强调应从多个角度研究线虫的耐寒性,如寒冷敏感型线虫的研究、寄生线虫的耐寒对策研究以及交叉胁迫的研究。     

Improved cold tolerance in glucagon-treated rats

In glucagon-treated rats (50 μg/100g, twice a day, 4 wks, sc) (GTR), the weights of liver and interscapular brown adipose tissue (BAT), and the level of plasma glucagon increased as compared with those in the vehicle-treated controls (VC). Mitochondria of BAT were markedly developed in size and cristae. Cold tolerance as assessed by the rate of fall in colonic temperature at ?5 °C was improved. Elevations of colonic temperatures by noradrenaline (40 μg/100g, im) were significantly enhanced in GTR. After cold exposure, blood free fatty acids (FFA) and plasma glucagon levels increased, but blood glucose and β-hydroxybutyrate levels were not changed in VC. Both blood FFA and β-hydroxybutyrate levels increased and blood glucose level decreased, but plasma glucagon levels was not affected by cold exposure in GTR. These results suggest that glucagon is involved in cold acclimation by means of enhanced nonshivering thermogenesis, possibly due to an activation of BAT as well as increased production and utilization of ketone bodies in the liver.     

Rapid evolution of cold tolerance in stickleback

Climate change is predicted to lead to increased average temperatures and greater intensity and frequency of high and low temperature extremes, but the evolutionary consequences for biological communities are not well understood. Studies of adaptive evolution of temperature tolerance have typically involved correlative analyses of natural populations or artificial selection experiments in the laboratory. Field experiments are required to provide estimates of the timing and strength of natural selection, enhance understanding of the genetics of adaptation and yield insights into the mechanisms driving evolutionary change. Here, we report the experimental evolution of cold tolerance in natural populations of threespine stickleback fish (Gasterosteus aculeatus). We show that freshwater sticklebacks are able to tolerate lower minimum temperatures than marine sticklebacks and that this difference is heritable. We transplanted marine sticklebacks to freshwater ponds and measured the rate of evolution after three generations in this environment. Cold tolerance evolved at a rate of 0.63 haldanes to a value 2.5°C lower than that of the ancestral population, matching values found in wild freshwater populations. Our results suggest that cold tolerance is under strong selection and that marine sticklebacks carry sufficient genetic variation to adapt to changes in temperature over remarkably short time scales.     

Mechanisms of oral tolerance revisited

Oral tolerance induction is thought to depend on special antigen presenting cells in the gut. A new report in the previous issue of Arthritis Research & Therapy supports this idea by demonstrating that indoleamine 2,3-dioxygenase-expressing dendritic cells in Peyer's patches from orally tolerized mice suppress T-cell responses via the generation of CD4+CD25+ regulatory T cells. This finding provides novel input into the mechanisms of oral tolerance that could further facilitate its use for the treatment of autoimmunity and chronic inflammatory reactions.