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Cheetahs (Acinonyx jubatus) are a textbook example of how habitat loss, human-wildlife conflicts and historic bottlenecks depleted genetic variability, both genome-wide and at the major histocompatibility complex (MHC), which plays an integral role in the adaptive immune response. However, free-ranging Namibian cheetahs show no signs of impaired immunocompetence or health. This contradicts theoretical expectations and poses the question whether the manner by which MHC diversity is judged needs to be revised. Here, we show that free-ranging Namibian cheetahs still harbour MHC alleles that are divergent enough to cover several functionally distinct MHC supertypes and thus are probably capable of binding and presenting a relatively broad range of antigens to T-cells. We detected a similar pattern in three other free-ranging, strongly bottlenecked cat species, supporting the hypothesis that species with a low MHC allelic diversity might be able to retain functional diversity not within but across loci. Moreover, the allelic composition influences the level of MHC class I and class II expression which also might play a significant role in pathogen defence. Thus, our study indicates that the evolutionary role of MHC diversity goes beyond counting the remaining number of MHC alleles and offers an explanation as to how cat species might have avoided impaired immuno-competence, despite showing low MHC allelic diversity. Although the low MHC diversity currently seems to be sufficient to ensure the health of free-ranging cheetahs, it is currently unknown whether it can provide sufficient protection from future threats through emerging new pathogens. [ABSTRACT FROM AUTHOR]

Host defense peptides act on the forefront of innate immunity, thus playing a central role in the survival of animals and plants. Despite vast morphological changes in species through evolutionary history, all animals examined to date share common features in their innate immune defense strategies, hereunder expression of host defense peptides (HDPs). Most studies on HDPs have focused on humans, domestic and laboratory animals. More than a thousand different sequences have been identified, yet data on HDPs in wild-living animals are sparse. The biological functions of HDPs include broad-spectrum antimicrobial activity and immunomodulation. Natural selection and coevolutionary host-pathogen arms race theory suggest that the extent and specificity of the microbial load influences the spectrum and potency of HDPs in different species. Individuals of extant species—that have lived for an extended period in evolutionary history amid populations with intact processes of natural selection—likely possess the most powerful and well-adapted “natural antibiotics”. Research on the evolutionary history of the innate defense system and the host in context of the consequences of challenges as well as the efficacy of the innate immune system under natural conditions is therefore of immediate interest. This review focuses on evolutionary aspects of immunophysiology, with emphasis on innate effector molecules. Studies on host defense in wild-living animals may significantly enhance our understanding of inborn immune mechanisms, and help identify molecules that may assist us to cope better with the increasing microbial challenges that likely follow from the continuous amplification of biodiversity levels on Earth. [ABSTRACT FROM AUTHOR]

Dispersal has a significant impact on lifetime reproductive success, and is often more prevalent in one sex than the other. In group-living mammals, dispersal is normally male-biased and in theory this sexual bias could be a response by males to female mate preferences, competition for access to females or resources, or the result of males avoiding inbreeding. There is a lack of studies on social mammals that simultaneously assess these factors and measure the fitness consequences of male dispersal decisions. Here we show that male-biased dispersal in the spotted hyaena (Crocuta crocuta) most probably results from an adaptive response by males to simple female mate-choice rules that have evolved to avoid inbreeding. Microsatellite profiling revealed that females preferred sires that were born into or immigrated into the female’s group after the female was born. Furthermore, young females preferred short-tenured sires and older females preferred longer-tenured sires. Males responded to these female mate preferences by initiating their reproductive careers in groups containing the highest number of young females. As a consequence, 11% of males started their reproductive career in their natal group and 89% of males dispersed. Males that started reproduction in groups containing the highest number of young females had a higher long-term reproductive success than males that did not. The female mate-choice rules ensured that females effectively avoided inbreeding without the need to discriminate directly against close kin or males born in their own group, or to favour immigrant males. The extent of male dispersal as a response to such female mate preferences depends on the demographic structure of breeding groups, rather than the genetic relatedness between females and males. [ABSTRACT FROM AUTHOR]

We investigated the temperature dependence of some physiological parameters of common eelpout (Zoarces viviparus) from different locations (North Sea, Baltic Sea and Norwegian Sea) on acclimation temperature (3 °C and 12 °C) and acute temperature variation. The lethal limit of 12 °C-acclimated eelpout was determined as the critical thermal maximum [loss of equilibrium (LE) and onset of muscular spasms (OS)] and it was found to be 26.6 °C for LE and 28.8 °C for OS for all populations. However, these parameters do not have any relevant ecological interpretation. We therefore investigated the effect of gradually increased water temperature on standard metabolic rate (measured as resting oxygen consumption Mo2) and critical oxygen concentration ([O2]c) of eelpouts. Acclimation to low temperature (3 °C) resulted in partial compensation of Mo2, paralleled by a decrease of activation energy for Mo2 (from 82 kJ mol–1 at 12 °C to about 50 kJ mol–1 at 3 °C) in North Sea and Baltic Sea eelpouts. At the same time, Norwegian eelpout showed no acclimation of oxygen demand to warm temperature (12 °C) at all. The scope for eelpout aerobic metabolism shrank considerably with increased acclimation temperature, as [O2]c approached water oxygen concentrations. At 22.5±1 °C the [O2]c reached air saturation, which is equivalent to the upper critical temperature (TcII) and at this temperature the aerobic scope for the metabolism completely disappeared. In line with previous insight, the comparative analysis of the temperature dependence of Mo2 of Z. viviparus from different populations suggests that a pejus (sub-critical) temperature for this species is about 13–15 °C. In conclusion, the capacity to adjust aerobic metabolism relates to thermal tolerance and the bio-geographical distribution of the species. Global warming would thus be likely to cause a shift in the distribution of this species to the North. [ABSTRACT FROM AUTHOR]

In vivo diffusion-weighted magnetic resonance imaging (MRI) was used to determine the effects of an osmotic challenge (1% NaCl) to a freshwater fish, the common carp ( Cyprinus carpio). The imaged region covered organs such as the swimbladder, the liver, the kidney, the intestine, the spinal cord, and muscle tissue. A striking difference between salt-treated and control fish was found in the liver. The apparent diffusion coefficient value of livers from control fish was (0.39±0.16) 10−9 m2/s and of salt-treated fish was (1.23±0.14) 10−9 m2/s, which points to an increase in extracellular water content. These results were partially confirmed by a decrease in dry/wet weight ratio of the liver tissue. We also found increased levels of stress proteins in liver tissue. The Q factor of the applied radiofrequency coil dropped dramatically when we performed experiments with salt-exposed fish, indicating an increased conductivity resulting from the increased ion concentration and osmolarity of the fish. The data on plasma osmolarity of salt-exposed fish confirm a significant osmolarity increase upon salt exposure (from 334 to 430 mOsm/kg) and exceeded the osmolarity of the salt water (324 mOsm/kg), indicating that carp tend to cope with an increased salinity by increasing the internal osmolarity (hyperosmotic regulation). These data demonstrate that diffusion-weighted MRI might be a useful and noninvasive tool in the study of osmotic challenges of aquatic organisms. [ABSTRACT FROM AUTHOR]

A culture of juvenile Sepia officinalis L. was kept during summer 1985 in the aquaria of the 'Station Marine', Wimereux, France. During the first four months of juvenile development, oxygen consumption under increasing hypoxia was measured with a closed respirometer. The experiments revealed a high regulatory capacity of juvenile S. officinalis. The critical oxygen concentrations were calculated and their ontogenetical evolution was studied. The critical oxygen concentration increased with increasing development. A linear relationship emerged between the critical oxygen concentration and the logarithm of the wet weight [CO (mg O l)=-0.393+0.893×log( W)]. The decreasing regulatory capacity of growing S. officinalis is most probably related to adaptations to a changing ecological environment during development. Another possibility is a physiological change, most probably related to the shift from embryonic to adult hemocyanin. [ABSTRACT FROM AUTHOR]

The article discusses the method of semiquantitative detection of intracellular stress proteins found in carp fish using the immunoblot technique. Stress proteins are heat shock proteins or chaperonins divided according to their molecular weight. They are considered useful biomarkers for monitoring pollution because they can withstand any environmental stress. Carp fishes were placed in an aquarium with filtered tap water for two weeks. They were then induced with heat shock proteins, but only the white muscle of the fish was used. Immunoblotting was interfered by supernatan matrix. It was concluded that immunoblotting is a suitable method for detection and determination of stress proteins.

Identifying how dominance within and between the sexes is established is pivotal to understanding sexual selection and sexual conflict. In many species, members of one sex dominate those of the other in one-on-one interactions. Whether this results from a disparity in intrinsic attributes, such as strength and aggressiveness, or in extrinsic factors, such as social support, is currently unknown. We assessed the effects of both mechanisms on dominance in the spotted hyaena (Crocuta crocuta), a species where sexual size dimorphism is low and females often dominate males. We found that individuals with greater potential social support dominated one-on-one interactions in all social contexts, irrespective of their body mass and sex. Female dominance emerged from a disparity in social support in favour of females. This disparity was a direct consequence of male-biased dispersal and the disruptive effect of dispersal on social bonds. Accordingly, the degree of female dominance varied with the demographic and kin structure of the social groups, ranging from male and female co-dominance to complete female dominance. Our study shows that social support can drive sex-biased dominance and provides empirical evidence that a sex-role-defining trait can emerge without the direct effect of sex.