(1/4478) Environmental occurrence, analysis, and toxicology of toxaphene compounds.
Toxaphene production, in quantities similar to those of polychlorinated biphenyls, has resulted in high toxaphene levels in fish from the Great Lakes and in Arctic marine mammals (up to 10 and 16 microg g-1 lipid). Because of the large variabiliity in total toxaphene data, few reliable conclusions can be drawn about trends or geographic differences in toxaphene concentrations. New developments in mass spectrometric detection using either negative chemical ionization or electron impact modes as well as in multidimensional gas chromatography recently have led researchers to suggest congener-specific approaches. Recently, several nomenclature systems have been developed for toxaphene compounds. Although all systems have specific advantages and limitations, it is suggested that an international body such as the International Union of Pure and Applied Chemistry make an attempt to obtain uniformity in the literature. Toxicologic information on individual chlorobornanes is scarce, but some reports have recently appeared. Neurotoxic effects of toxaphene exposure such as those on behavior and learning have been reported. Technical toxaphene and some individual congeners were found to be weakly estrogenic in in vitro test systems; no evidence for endocrine effects in vivo has been reported. In vitro studies show technical toxaphene and toxaphene congeners to be mutagenic. However, in vivo studies have not shown genotoxicity; therefore, a nongenotoxic mechanism is proposed. Nevertheless, toxaphene is believed to present a potential carcinogenic risk to humans. Until now, only Germany has established a legal tolerance level for toxaphene--0.1 mg kg-1 wet weight for fish. (+info)
(2/4478) Richness of Colchic vegetation: comparison between refugia of south-western and East Asia.
BACKGROUND: The Colchis is one of the species-rich refugia and a centre of biological diversity in western Eurasia. We analysed patterns of richness, endemism and invasions in relation to taxonomy (family membership), life form, certain habitats in the Colchis, and compared them to patterns found for Japan. RESULTS: We found that in the Colchis perennials are significantly over-represented in endemic species, and that they typically occur on limestone soils and in alpine tall herbaceous vegetation. The Asteraceae produce significantly large number of both endemic and alien species, whereas the Poaceae are over-represented in alien species but under-represented in endemics. Likewise, the Apiaceae are over-represented in endemics, whereas the Euphorbiaceae are over-represented in alien species. Similar patterns have been found in Yakushima, Japan. The Morisita-Horn index of similarity between these two sites was 0.83 (based on family size). Although the flora of Adjara comprised of fewer families than the flora of Yakushima, the largest families are richer in species in the flora of Adjara than in the flora of Yakushima. CONCLUSIONS: Floristic analysis of refugia of western Eurasia and their comparison with geographically distant areas can provide useful data for plant ecological and evolutionary studies. Potentially, such studies can produce testable hypotheses on plant migrations and on their historical geography. For example, the data presented in this study indicate that more severe conditions in the Pleistocene and geographical isolation of the Colchis may be responsible for the higher relative importance of adaptive radiation in the shaping of its modern flora. (+info)
(3/4478) Patterns in abundance and diversity of faecally dispersed parasites of tiger in Tadoba National Park, central India.
BACKGROUND: Importance of parasites in ecological and evolutionary interactions is being increasingly recognized. However, ecological data on parasites of important host species is still scanty. We analyze the patterns seen in the faecal parasites of tigers in the Tadoba National Park, India, and speculate on the factors and processes shaping the parasite community and the possible implications for tiger ecology. RESULTS: The prevalence and intensities were high and the parasite community was dominated by indirect life cycle parasites. Across all genera of parasites variance scaled with the square of the mean and there was a significant positive correlation between prevalence and abundance. There was no significant association between different types of parasites. CONCLUSIONS: The 70 samples analyzed formed 14 distinct clusters. If we assume each of the clusters to represent individual tigers that were sampled repeatedly and that resident tigers are more likely to be sampled repeatedly, the presumed transient tigers had significantly greater parasite loads than the presumed resident ones. (+info)
(4/4478) The diversity of microorganisms associated with Acromyrmex leafcutter ants.
BACKGROUND: Molecular biological techniques are dramatically changing our view of microbial diversity in almost any environment that has so far been investigated. This study presents a systematic survey of the microbial diversity associated with a population of Acromyrmex leafcutter ants. In contrast to previous studies on social insects, which targeted specific groups of symbionts occurring in the gut (termites, Tetraponera ants) or in specialised cells (Camponotus ants) the objective of our present study was to do a total screening of all possible micro-organisms that can be found inside the bodies of these leafcutter ants. RESULTS: We amplified, cloned and sequenced SSU rRNA encoding gene fragments from 9 microbial groups known to have insect-associated representatives, and show that: (1) representatives of 5 out of 9 tested groups are present, (2) mostly several strains per group are present, adding up to a total of 33 different taxa. We present the microbial taxa associated with Acromymex ants in a phylogenetic context (using sequences from GenBank) to assess and illustrate to which known microorganisms they are closely related. The observed microbial diversity is discussed in the light of present knowledge on the evolutionary history of Acromyrmex leafcutter ants and their known mutualistic and parasitic symbionts. CONCLUSIONS: The major merits of the screening approach documented here is its high sensitivity and specificity, which allowed us to identify several microorganisms that are promising candidates for further study of their interactions with Acromyrmex leafcutter ants or their gardens. (+info)
(5/4478) A new neuroprotective pinusolide derivative from the leaves of Biota orientalis.
A new pinusolide derivative, 15-methoxypinusolidic acid (1), and another new isopimarane diterpene, ent-isopimara-15-en-3 alpha,8 alpha-diol (2) with three known diterpenes, lambertianic acid (3), isopimara-8(9),15-dien-18-oic acid (4) and isopimara-7(8),15-dien-3 beta,18-diol (5) were isolated from the 90% MeOH fraction of Biota orientalis (L.) ENDL. (Cupressaceae) leaves. Chemical structures of 1-5 were elucidated by analyses of their spectral data, including the two-dimensional (2D) NMR technique. Compound 1 showed significant protective activity against glutamate-induced neurotoxicity in primary cultures of rat cortical cells. (+info)
(6/4478) Biodiversity of nematode assemblages from the region of the Clarion-Clipperton Fracture Zone, an area of commercial mining interest.
BACKGROUND: The possibility for commercial mining of deep-sea manganese nodules is currently under exploration in the abyssal Clarion-Clipperton Fracture Zone. Nematodes have potential for biomonitoring of the impact of commercial activity but the natural biodiversity is unknown. We investigate the feasibility of nematodes as biomonitoring organisms and give information about their natural biodiversity. RESULTS: The taxonomic composition (at family to genus level) of the nematode fauna in the abyssal Pacific is similar, but not identical to, the North Atlantic. Given the immature state of marine nematode taxonomy, it is not possible to comment on the commonality or otherwise of species between oceans. The between basin differences do not appear to be directly linked to current ecological factors. The abyssal Pacific region (including the Fracture Zone) could be divided into two biodiversity subregions that conform to variations in the linked factors of flux to the benthos and of sedimentary characteristics. Richer biodiversity is associated with areas of known phytodetritus input and higher organic-carbon flux. Despite high reported sample diversity, estimated regional diversity is less than 400 species. CONCLUSION: The estimated regional diversity of the CCFZ is a tractable figure for biomonitoring of commercial activities in this region using marine nematodes, despite the immature taxonomy (i.e. most marine species have not been described) of the group. However, nematode ecology is in dire need of further study. (+info)
(7/4478) Complexity in natural microbial ecosystems: the Guerrero Negro experience.
The goal of this project is to describe and understand the organismal composition, structure, and physiology of microbial ecosystems from hypersaline environments. One collection of such ecosystems occurs at North America's largest saltworks, the Exportadora de Sal, in Guerrero Negro, Baja California Sur. There, seawater flows through a series of evaporative basins with an increase in salinity until saturation is reached and halite crystallization begins. Several of these ponds are lined with thick (10 cm) microbial mats that have received some biological study. To determine the nature and extent of diversity of the microbial organisms that constitute these ecosystems, we are conducting a phylogenetic analysis using molecular approaches, based on cloning and sequencing of small subunit (SSU) rRNA genes (16S for Bacteria and Archaea, 18S for Eukarya). In addition, we report preliminary results on the microbial composition of a laminated community that occurs in a crystallized gypsum-halite matrix in near-saturated salt water. Exposure of the interior of these large (kilogram) wet, endoevaporite crystals reveals a multitude of colors: layers of yellow, green, pink, and purple microbiota. To date, analyses of these two environments indicate the ubiquitous dominance of uncultured organisms of phylogenetic kinds not generally thought to be associated with hypersaline environments. (+info)
(8/4478) Viral influence on aquatic bacterial communities.
Bacterial viruses, or bacteriophages, have numerous roles in marine systems. Although they are now considered important agents of mortality of bacteria, a second possible role of regulating bacterial community composition is less well known. The effect on community composition derives from the presumed species-specificity and density-dependence of infection. Although models have described the "kill the winner" hypothesis of such control, there are few observational or experimental demonstrations of this effect in complex natural communities. We report here on some experiments that demonstrate that viruses can influence community composition in natural marine communities. Although the effect is subtle over the time frame suitable for field experiments (days), the cumulative effect over months or years would be substantial. Other virus roles, such as in genetic exchange or microbial evolution, have the potential to be extremely important, but we know very little about them. (+info)