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Length Data (length + data)
Selected AbstractsAbnormalities in sexual development of the amphipod Gammarus pulex (L.) found below sewage treatment worksENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Melanie Yvette Gross Abstract Increasing numbers of widely used industrial, agricultural, and natural chemicals are known to elicit endocrine-disrupting effects in a wide range of vertebrate and invertebrate species. The objective of this study was to determine whether the sexual development of the freshwater crustacean Gammarus pulex (L.) was affected below sewage treatment works (STW) previously known to contain endocrine-disrupting chemicals in their effluent. The gonadal structure, external sexual characteristics, and size of gammarids from exposed sites were compared to those of gammarids from a reference site. No significant difference was found in the gonadal structure of males collected below two STW. However, a highly significant number of females collected from a site known to elicit high estrogenic responses in vertebrates displayed an abnormal structure of oocytes in vitellogenesis. Body size was significantly shorter and male/female size differential was significantly reduced below one of the STW. Analysis of gnathopod and genital papillae length data suggests that different allometric relationships of these organs to body size exist between sample sites. [source] Small fish, big fish, red fish, blue fish: size-biased extinction risk of the world's freshwater and marine fishesGLOBAL ECOLOGY, Issue 6 2007Julian D. Olden ABSTRACT Aim, In light of the current biodiversity crisis, there is a need to identify and protect species at greatest risk of extinction. Ecological theory and global-scale analyses of bird and mammal faunas suggest that small-bodied species are less vulnerable to extinction, yet this hypothesis remains untested for the largest group of vertebrates, fish. Here, we compare body-size distributions of freshwater and marine fishes under different levels of global extinction risk (i.e. listed as vulnerable, endangered or critically endangered according to the IUCN Red List of Threatened Species) from different major sources of threat (habitat loss/degradation, human harvesting, invasive species and pollution). Location, Global, freshwater and marine. Methods, We collated maximum body length data for 22,800 freshwater and marine fishes and compared body-size frequency distributions after controlling for phylogeny. Results, We found that large-bodied marine fishes are under greater threat of global extinction, whereas both small- and large-bodied freshwater species are more likely to be at risk. Our results support the notion that commercial fishing activities disproportionately threaten large-bodied marine and freshwater species, whereas habitat degradation and loss threaten smaller-bodied marine fishes. Main conclusions, Our study provides compelling evidence that global fish extinction risk does not universally scale with body size. Given the central role of body size for trophic position and the functioning of food webs, human activities may have strikingly different effects on community organization and food web structure in freshwater and marine systems. [source] Thermal anomaly around the Nojima Fault as detected by fission-track analysis of Ogura 500 m borehole samplesISLAND ARC, Issue 3-4 2001Takahiro Tagami Abstract To better understand heat generation and transfer along earthquake faults, this paper presents preliminary zircon fission-track (FT) length data from the Nojima Fault, Awaji Island, Japan, which was activated during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake). Samples were collected of Cretaceous granitic rocks from the Ogura 500 m borehole as well as at outcrops adjacent to the borehole site. The Nojima Fault plane was drilled at a depth of 389.4 m (borehole apparent depth). Fission-track lengths in zircons from localities > 60 m distance from the fault plane, as well as those from outcrops, are characterized by the mean values of ,10,11 ,m and unimodal distributions with positive skewness, which show no signs of an appreciable reduction in FT length. In contrast, those from nearby the fault at depths show significantly reduced mean track lengths of ,6,8 ,m and distributions having a peak around 6,7 ,m with rather negative skewness. In conjunction with other geological constraints, these results are best interpreted by a recent thermal anomaly around the fault, which is attributable to heat transfer via focused fluids from the deep interior of the crust and/or heat dispersion via fluids associated with frictional heating by fault motion. [source] Bifocal soft contact lenses as a possible myopia control treatment: a case report involving identical twinsCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 4 2008Thomas A Aller OD Background:, Several studies have suggested that bifocal and progressive spectacles can reduce progression of myopia in esophoric children. This study compared myopic progression with bifocal (BSCL) and single vision soft contact lenses (SVSCL) in identical twins with near point esophoria. Methods:, Two 12-year-old myopic girls were randomly assigned to wear either BSCL or SVSCL for one year using a double-masked design. Both twins then wore BSCLs for another year. Ocular measurements included cycloplegic and manifest refractions, corneal curvature and axial length. Distance and near phorias were measured through distance corrections and near associated phorias, with both types of contact lenses. Results:, Through their SVSCLs, both children exhibited near associated esophorias, which were neutralised by the BSCLs. The child wearing SVSCLs over the first year showed significant myopic progression, increasing -1.19 D (binocular average), while the child wearing BSCLs showed no progression (+0.13 D). The latter child showed limited progression (-0.28 D) over the second year, while switching from SVSCLs to BSCLs arrested progression in the other child (+0.44 D after one year). Axial length data were consistent with the refractive findings; the child exhibiting more myopia at the end of the first 12 months of the study had longer eyes (by 0.64 mm) than her sister, although their corneas also had steepened more (by 0.44 D compared to 0.18 D). The children showed similar, small increases in eye size over the second year when both wore BSCLs (binocular averages: 0.05, 0.09 mm, respectively). Conclusion:, The apparent inhibitory effect of BSCLs on myopic progression reported in this twin study argues for further study of their efficacy as a control treatment for myopes with near esophoria. [source] New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative methodOIKOS, Issue 12 2009Jordi Peig Body condition is assumed to influence an animal's health and fitness. Various non-destructive methods based on body mass and a measure of body length have been used as condition indices (CIs), but the dominant method amongst ecologists is currently the calculation of residuals from an ordinary least squares (OLS) regression of body mass against length. Recent studies of energy reserves in small mammals and starlings claimed to validate this method, although we argue that they did not include the most appropriate tests since they compared the CI with the absolute size of energy reserves. We present a novel CI (the ,scaled mass index') based on the central principle of scaling, with important methodological, biological and conceptual advantages. Through a reanalysis of data from small mammals, starlings and snakes, we show that the scaled mass index is a better indicator of the relative size of energy reserves and other body components than OLS residuals, performing better in all seven species and in 19 out of 20 analyses. We also present an empirical and theoretical comparison of the scaled mass index and OLS residuals as CIs. We argue that the scaled mass index is a useful new tool for ecologists. [source] | ||||||||||