Muscle fiber types and functional demands in feeding mechanisms of fishes

Profiles of muscle fiber types and pharyngeal jaw dentition vary in accordance with trophic demands and skeletal organization in teleost fishes. Carnivorous, omnivorous, and molluscivorous members of the ecologically analogous Cichlidae and Centrarchidae were compared in terms of their pharyngeal jaw anatomy and branchial muscle histochemistry. The two families differed greatly in patterns of tooth form, wear, and replacement. Four muscle fiber type patterns were discoverd: (1) single fiber, (2) zoned, (3) mosaic, and (4) zoned-mosaic. Multiple fiber type muscles were more prevalent in fishes that masticate tough foods with their pharyngeal jaws. Such muscles were also more prevalent in cichlids than in centrarchids. It appears that muscles with multiple fiber types in lower vertebrates are, as a rule, compartmentalized, whereas in higher vertebrates, multiple fiber type muscles are a musaic matrix. The occurrence of mosaic patterns in some fish branchial muscles, however, suggests that mosaic muscles are initially single fiber type muscles exposed to complex functional demands, such as food preparation. Furthermore, it is plausible that the evolutionary replacement of the lower vertebrate zoning pattern by the higher vertebrate mosaic matrix is directly related to the effects of gravity, a force more influential on terrestrial than on aquatic organisms.     

The dispersion of arctic breeding birds according to snow-free patch dimensions during the spring thaw in the north-eastern Taimyr Peninsula,Russia

 The dispersion of passerines, ptarmigan Lagopus mutus and waders in relation to available snow-free patches is described after spring arrival but prior to the main thaw at Pronchishcheva Lake, north-eastern Taimyr, in June 1991. The numbers of ptarmigan and passerines were proportional to patch perimeter but disproportionately more birds occurred on smaller patches. In contrast, wader numbers were proportional to patch area but disproportionately more occurred along the perimeters of large patches. These patterns are discussed in relation to risk of predation and food availability. We speculate that the predation risk is higher in small patches for uniformly coloured birds but may be lower for white and pied species. The availability of overwintering plants, fresh plant growth and insects is thought to be highest at the perimeters of snow-free patches. Received: 19 November 1993/Accepted: 4 September 1995     

Comparison of leaf morphology among submersed species of Myriophyllum (Haloragaceae) from different habitats and geographical distributions

An image analysis system was used to calculate the surface area and volume of the submerged leaves of seven species of Myriophyllum. We separated the species into two categories based on their distribution and habitat differences and compared their surface area, volume, dry mass, specific leaf area, and surface to volume ratios. The geographic location and habitat of the species explained the greatest percentage of total variance for these variables when compared by analysis of variance. A leaf shape analysis was performed by regressing surface area with volume for each species. Interspecific comparisons of leaf shape were made using analysis of covariance. Fundamental interspecific differences in submerged leaf shape, associated with differences in their geographic distributions and habitats, are explained as adaptations for different nutrient uptake regimes.     

Chemical modification of mitochondria: I. Specific labeling by 2,4-dinitro-5-(bromo-[2-14C]acetoxyethoxy) phenol

The uncoupler dinitrobromoacetoxyethoxyphenol (DNBP) has been synthesized and found to label rapidly and specifically a small number of cysteine residues in rat liver mitochondria. The labeling reaction was essentially complete in a few minutes. Only eight of the mitochondrial polypeptide bands, of MW 97, 58, 52, 43, 30, 26, 22, 13 × 10³, respectively, as separated by SDS gel electrophoresis, were found to carry the radioactive label. In each case, the label which survived acid hydrolysis was covalently bound to cysteine residues through alkylation reaction. Under the present experimental conditions, only 0.45 mole of the label was covalently bound to mitochondrial protein per mole of cytochrome aa₃ and only 1 out of about 650 sulfhydryl groups was so labeled. Consideration of the specificity of the labeling and the observed time-dependence of DNBP-stimulated respiration suggests that the labeled protein molecules are either at or very close to the mitochondrial coupling sites and probably play an important role in the primary energy transduction process.     

Nanoscale structure of type I collagen fibrils: Quantitative measurement of D-spacing

This article details a quantitative method to measure the D-periodic spacing of type I collagen fibrils using atomic force microscopy coupled with analysis using a two-dimensional fast fourier transform approach. Instrument calibration, data sampling and data analysis are discussed and comparisons of the data to the complementary methods of electron microscopy and X-ray scattering are made. Examples of the application of this new approach to the analysis of type I collagen morphology in disease models of estrogen depletion and osteogenesis imperfecta (OI) are provided. We demonstrate that it is the D-spacing distribution, not the D-spacing mean, that showed statistically significant differences in estrogen depletion associated with early stage osteoporosis and OI. The ability to quantitatively characterize nanoscale morphological features of type I collagen fibrils will provide important structural information regarding type I collagen in many research areas, including tissue aging and disease, tissue engineering, and gene knockout studies. Furthermore, we also envision potential clinical applications including evaluation of tissue collagen integrity under the impact of diseases or drug treatments.     

Enzyme-linked immunosorbent assay of antigens from Candida albicans circulating in infected mice and rabbits: The role of mannan

Various antisera raised either to antigens ofCandida albicans or to sub-lethal infections of blastospores (convalescent sera) were tested for their efficacy in diagnosing systemic disease in artifically infected animals. Globulin from convalescent serum, when conjugated with alkaline phosphatase and used in enzyme-linked immunosorbent assays (ELISA), was the only antiserum type which detected circulatingCandida-related antigen in the serum of infected animals. Conjugates made from anti-mannan, anti-blastospore or antimycelial globulin did not detect antigen. Mannan did not appear to be related to an antigen produced in sera of experimentally infected mice. The significance of these results in the diagnosis of systemic candidosis is discussed.     

Knowledge-based models for predicting species occurrence in arable conditions

This paper explores the potential of rule-based habitat models to predict the occurrence of some common species in arable conditions. Models were developed for 10 arable plant species, 7 Hemiptera species, 8 carabid species and for 5 bird species whose ecology was sufficiently known. Rule sets linking species occurrence to environmental variables were produced using available literature and expert knowledge about ecological requirements of the selected species. Environmental variables described the nature and condition of habitats at various scales, ranging from vegetation quadrat to the landscape in a 1 km radius of species sampling sites. The performance of the 34 models developed was assessed in two areas of England. Results show the rule-based habitat models developed for arable plants and birds were not very successful with Cohen's k values often <0.4 for plants and very close to 0 for all bird species. Conversely, rule-based models performed surprisingly well for carabids and Hemiptera with k values on average >0.4. This suggests that ecological knowledge on these invertebrate species is more complete than we expected. The effect of species prevalence on model performance and the potential application of knowledge-based habitat models in the context of biodiversity assessment are discussed.