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Low Metabolic Rate (low + metabolic_rate)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Comparison of routine metabolic rates of the stygobite, Gammarus acherondytes (Amphipoda: Gammaridae) and the stygophile, Gammarus troglophilus

FRESHWATER BIOLOGY, Issue 6 2006
FRANK M. WILHELM
Summary 1. Reduced metabolic rate among cave organisms compared with surface species has long been suggested as an adaptation to food shortage in cave environments. However, comparisons of metabolic rates between species have not often included closely related surface and cave species. By measuring metabolic rate across three seasons and over a range of body sizes, we examined the hypothesis that the routine metabolic rate of Gammarus acherondytes, a federally listed stygobitic amphipod, is lower than that of the closely related stygophilic Gammarus troglophilus. To determine if human activities increased the supply of organic matter to caves, we also examined the relationship between residential development and bacterial contamination in water wells. 2. For G. acherondytes, the slope of the overall relationship between oxygen consumption and body dry mass did not differ from zero and did not vary seasonally, whereas for G. troglophilus it was positive and higher in summer than in winter and spring. These results provide insights into a potential novel metabolic adaptation among stygobites. Higher metabolic rate in young G. acherondytes would allow efficient use of typically transient energy sources and a low metabolic rate at larger body sizes would increase survival through periods of food scarcity. 3. The number of wells with faecal coliform contamination was weakly but positively correlated with the number of residential building permits, indicating that surface land-use changes probably increase the availability of energy in groundwater systems inhabited by G. acherondytes. This may give stygophilic animals, with higher metabolic rates, a competitive advantage in the caves, thus reducing the abundance of stygobites such as G. acherondytes. [source]

Gametophyte morphology and ultrastructure of the extremely deep shade fern, Trichomanes speciosum

NEW PHYTOLOGIST, Issue 1 2001
Kittima Makgomol
Summary ,,The extent to which macro- and micromorphological features might contribute to tolerance of extremely deep shade by Trichomanes speciosum, a member of the filmy ferns (Hymenophyllaceae), is reported here. ,,Confocal laser scanning, transmission and scanning electron microscopy were used to study the ultrastructure of gametophytes and sporophyte leaves. ,,Gametophyte filament cells contain numerous small, spherical or ovoid chloroplasts, whereas sporophyte leaf cells have fewer, slightly larger, disc-shaped chloroplasts. The chloroplast grana of gametophytic cells have fewer thylakoids than sporophyte cells, although grana are not numerous in either. Gametophyte filament cell walls resemble those of sporophyte leaf cells, with two or more layers of electron-opaque material and covered in a thin cuticle. Gemma cell wall ultrastructure does not differ from that of gametophyte filament cells; rhizoid cell walls are thick and several-layered. ,,Neither gametophyte filaments nor sporophyte leaves have chloroplasts of the extreme forms reported for deep shade fern or angiosperm leaves. The success of the fern is attributed to a low metabolic rate and inability of other species to cope with extreme low light. [source]

Relative longevity and field metabolic rate in birds

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2008
A. P. MØLLER
Abstract Metabolism is a defining feature of all living organisms, with the metabolic process resulting in the production of free radicals that can cause permanent damage to DNA and other molecules. Surprisingly, birds, bats and other organisms with high metabolic rates have some of the slowest rates of senescence begging the question whether species with high metabolic rates also have evolved mechanisms to cope with damage induced by metabolism. To test whether species with the highest metabolic rates also lived the longest I determined the relationship between relative longevity (maximum lifespan), after adjusting for annual adult survival rate, body mass and sampling effort, and mass-specific field metabolic rate (FMR) in 35 species of birds. There was a strongly positive relationship between relative longevity and FMR, consistent with the hypothesis. This conclusion was robust to statistical control for effects of potentially confounding variables such as age at first reproduction, latitude and migration distance, and similarity in phenotype among species because of common phylogenetic descent. Therefore, species of birds with high metabolic rates senesce more slowly than species with low metabolic rates. [source]

Sound reasons for silence: why do molluscs not communicate acoustically?

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010
GEERAT J. VERMEIJ
Many adaptively beneficial states of form, behaviour and physiology are absent in large parts of the evolutionary tree of life. Although the causes of these absences can never be fully known, insights into the possibilities and limitations of adaptive evolution can be gained by examining the conditions that would be necessary for the forbidden phenotypes to evolve. Here, the case of acoustic communication in molluscs is considered. The production of sound as a warning to predators or as a means to attract mates is widespread among arthropods and vertebrates, both on land and in water, but is unknown among molluscs, even though many derived clades of gastropods and cephalopods are characterized by internal fertilization and by the evolution of long-distance visual and chemical signalling. Many molluscs possess suitable hard parts , shell, operculum and jaws , for producing sound, but most shell-bearing molluscs lack the agility or aggression necessary to cope with high-activity enemies attracted to an acoustic beacon. Their evolutionary background, arising from the generally passive adaptations of molluscs and other animals with low metabolic rates, prevents selection favouring communication by sound, and indeed favours silence. Several clades of shell-bearing gastropods and cephalopods were identified in which sound production has the greatest potential to arise or to be discovered. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 485,493. [source]