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Possible Physiological (possible + physiological)
Selected AbstractsThe geography of body size , challenges of the interspecific approachGLOBAL ECOLOGY, Issue 6 2007Shai Meiri ABSTRACT Recent compilations of large-scale data bases on the geographical distributions and body sizes of animals, coupled with developments in spatial statistics, have led to renewed interest in the geographical distribution of animal body sizes and the interspecific version of Bergmann's rule. Standard practice seems to be an examination of mean body sizes within higher taxa on gridded maps, with little regard to species richness or phylogeny. However, because the frequency distribution of body sizes is typically highly skewed, average size within grid cells may differ significantly between species-rich and species-poor cells even when the median and modal sizes remain constant. Species richness influences body size patterns because species are not added to communities at random in relation to their size: areas of low diversity are characterized by a higher range of body sizes than is expected by chance. Finally, a consideration of phylogenetic structure within taxa is necessary to elucidate whether patterns in the geography of size result from turnover between or within intermediate taxonomic levels. We suggest that the highest and lowest quantiles of body size distribution be mapped in order to expose possible physiological or ecological limitations on body size. [source] The evolution of reproductive and genomic diversity in ray-finned fishes: insights from phylogeny and comparative analysisJOURNAL OF FISH BIOLOGY, Issue 1 2006J. E. Mank Collectively, ray-finned fishes (Actinopterygii) display far more diversity in many reproductive and genomic features than any other major vertebrate group. Recent large-scale comparative phylogenetic analyses have begun to reveal the evolutionary patterns and putative causes for much of this diversity. Several such recent studies have offered clues to how different reproductive syndromes evolved in these fishes, as well as possible physiological and genomic triggers. In many cases, repeated independent origins of complex reproductive strategies have been uncovered, probably reflecting convergent selection operating on common suites of underlying genes and hormonal controls. For example, phylogenetic analyses have uncovered multiple origins and predominant transitional pathways in the evolution of alternative male reproductive tactics, modes of parental care and mechanisms of sex determination. They have also shown that sexual selection in these fishes is repeatedly associated with particular reproductive strategies. Collectively, studies on reproductive and genomic diversity across the Actinopterygii illustrate both the strengths and the limitations of comparative phylogenetic approaches on large taxonomic scales. [source] Cold adaptation in Arctic and Antarctic fungiNEW PHYTOLOGIST, Issue 2 2001Clare H. Robinson Summary Growth and activity at low temperatures and possible physiological and ecological mechanisms underlying survival of fungi isolated from the cold Arctic and Antarctic are reviewed here. Physiological mechanisms conferring cold tolerance in fungi are complex; they include increases in intracellular trehalose and polyol concentrations and unsaturated membrane lipids as well as secretion of antifreeze proteins and enzymes active at low temperatures. A combination of these mechanisms is necessary for the psychrotroph or psychrophile to function. Ecological mechanisms for survival might include cold avoidance; fungal spores may germinate annually in spring and summer, so avoiding the coldest months. Whether spores survive over winter or are dispersed from elsewhere is unknown. There are also few data on persistence of basidiomycete vs microfungal mycelia and on the relationship between low temperatures and the predominance of sterile mycelia in tundra soils. Acclimation of mycelia is a physiological adaptation to subzero temperatures; however, the extent to which this occurs in the natural environment is unclear. Melanin in dark septate hyphae, which predominate in polar soils, could protect hyphae from extreme temperatures and play a significant role in their persistence from year to year. [source] Protein and amino acid nutrition and metabolism in fish: current knowledge and future needsAQUACULTURE RESEARCH, Issue 3 2010Sadasivam J Kaushik Abstract Optimising the amino acid supply in tune with the requirements and improving protein utilization for body protein growth with limited impacts on the environment in terms of nutrient loads is a generic imperative in all animal production systems. With the continued high annual growth rate reported for global aquaculture, our commitments should be to make sure that this growth is indeed reflected in provision of protein of high biological value for humans. The limited availability of fish meal has led to some concerted efforts in fish meal replacement, analysing all possible physiological or metabolic consequences. The rising costs of plant feedstuffs make it necessary to strengthen our basic knowledge on amino acid availability and utilization. Regulation of muscle protein accretion has great significance with strong practical implications. In fish, despite low muscle protein synthesis rates, the efficiency of protein deposition appears to be high. Exploratory studies on amino acid flux, inter-organ distribution and particularly of muscle protein synthesis, growth and degradation and the underlying mechanisms as affected by dietary factors are warranted. Research on specific signalling pathways involved in protein synthesis and degradation have been initiated in order to elucidate the reasons for high dietary protein/amino acid supply required and their utilization. [source] | |||||||||||||