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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
D. Kim T. Okamoto T. Oda K. Tachibana K.S. Lee A. Ishimatsu Y. Matsuyama T. Honjo T. Muramatsu 《Marine Biology》2001,139(4):625-632
Although the ichthyotoxic mechanism of Chattonella marina is still unknown, several lines of evidence suggest that the reactive oxygen species (ROS), such as superoxide anion (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH), produced by C. marina are involved in the mortality of fish exposed to this flagellate. Recently, we found that the cell-free supernatant prepared from C. marina, which is considered to contain the glycocalyx, showed NADPH-dependent O2- generation. In this study, we prepared antiserum against the crude glycocalyx of C. marina. Using indirect immunofluorescence, it was confirmed that the antiserum specifically reacted with C. marina cells. In addition to C. marina, the antiserum also reacted with other raphidophycean flagellates such as Heterosigma akashiwo, Olisthodiscus luteus, and Fibrocapsa japonica, whereas no reactivity was observed against six other flagellate species tested. These results suggest that raphidophycean flagellates have common epitopes recognized by the antiserum. Interestingly, immunohistochemical analysis of paraformaldehyde-fixed gill lamellae from yellowtail exposed to C. marina revealed that the antiserum stained the surface of gill lamellae, while no such staining pattern was observed in control gill lamellae. These results suggest that the glycocalyx may be discharged when C. marina cells are inhaled into the fishes' mouths and then come into contact with the gill surface. Based on the present results, together with our previous findings, we propose that continuous accumulation of the discharged glycocalyx on the gill surface occurs during C. marina exposure, which may be responsible for the ROS-mediated severe gill tissue damage leading to fish death. 相似文献
963.
We determined the nuclear 18S rRNA sequences for 41 species of octocorals and used these to address the validity of the historical
ordinal divisions and the current subordinal divisions within the subclass Octocorallia. We also explored the phylogenetic
affinities of the species Dendrobrachia paucispina, which was originally classified in the order Antipatharia (subclass Ceriantipatharia) although polyp structure indicates
it belongs in the subclass Octocorallia. Trees constructed using maximum likelihood techniques are incongruent with the current
and historical taxonomy of the Octocorallia. There appeared to be three major clades of octocorals. The first clade included
most, but not all, pennatulaceans as a monophyletic group. The second clade contained 21 species, representing all major octocoral
groups other than pennatulaceans. The third clade contained members from three suborders of the Alcyonacea and one member
of the Pennatulacea. These data could not be used to distinguish the branching order of the three major clades. The species
D. paucispina had a close affinity with the genera Corallium and Paragorgia (Alcyonacea: Scleraxonia), although its morphology suggests it is more similar to the genus Chrysogorgia (Alcyonacea: Calcaxonia). The morphological character of dimorphism (the presence of both autozooids and siphonozooids within
a single colony) corresponded loosely with the topology of the most likely trees, and a single origin of dimorphism could
not be rejected. Despite sampling from the majority of families within the Octocorallia, many of the relationships within
this group remain ambiguous.
Received: 16 June 2000 / Accepted: 14 September 2000 相似文献
964.
A distinct smell of dimethylsulfide (DMS) was noted at the edge of the intertidal mudflat of Marennes-Oléron Bay, at the
French Atlantic coast, where dense populations of the marine flatworm Convoluta roscoffensis Graff (Platyhelminthes: Turbellaria) were present. DMS is the cleavage product of dimethylsulfoniopropionate (DMSP). DMSP
was shown to be present in high amounts in sediment containing the flatworm as well as in axenic cultures of the symbiotic
alga Tetraselmis sp. that was isolated from the flatworm. In untreated sediment samples containing C. roscoffensis the concentration of DMS was as high as ∼55 μmol l−1 sediment, and in samples that were fixed with glutaraldehyde the concentration of DMS was even three orders of magnitude
higher (∼66 mmol l−1 sediment). This rapid cleavage of DMSP to DMS in fixed samples was unexpected. Pure DMSP was stable in glutaraldehyde, and
it was therefore concluded that a DMSP-lyase was responsible for cleavage in the field samples. The isolated symbiotic alga,
Tetraselmis sp., did not show DMSP-lyase activity, indicating that DMSP-lyase may have been present in the flatworm, although the role
of bacteria could not be excluded. The Chl a-specific DMSP content of C. roscoffensis (∼200 mmol g−1) was much higher than that of Tetraselmis sp. (∼30 mmol g−1). Possibly, DMSP was not only present in the symbiotic alga, but was also incorporated in the body tissue of the flatworm.
It remains unclear what the function of DMSP is in C. roscoffensis. In Tetraselmis sp., but not in C. roscoffensis, DMSP increased with increasing salinity. It was concluded that salinity probably does not play an important role in the
dynamics of DMSP and DMS in sediment containing C. roscoffensis.
Received: 21 January 2000 / Accepted: 29 August 2000 相似文献
965.
Noninvasive Stress and Reproductive Measures of Social and Ecological Pressures in Free-Ranging African Elephants 总被引:7,自引:0,他引:7
Abstract: The African elephant ( Loxodonta africana ) experienced a poaching-related 60% population decline between 1979 and 1988 that was inordinately concentrated on adults. This, coupled with political pressures to delist the elephant, has created a need for noninvasive physiological measures that can quantify the long-term effects of past mortality patterns of this long-lived species. We collected fresh fecal samples from 16 female elephants in three different groups over 23 months at Tarangire National Park, Tanzania, and analyzed them for fecal progesterone and cortisol metabolites. Social and ecological measures were collected concurrently. Fecal progesterone metabolite measures corresponded significantly with stage of gestation, and appear to be able to confirm pregnancy in female elephants from as early as 3 months of gestation. We found that progesterone metabolite concentrations were significantly lower during the dry season than during the wet season after controlling for stage of gestation. Fecal cortisol metabolite concentrations showed the opposite seasonal pattern, being significantly higher in the dry season and inversely correlated with rainfall across seasons. Fecal cortisol metabolite concentrations also increased with group size and were correlated positively with dominance rank in the largest group. Our results suggest that measures of progesterone and cortisol metabolites in feces provide indices of reproductive function and physiological stress that can quantify both natural and human disturbances in African elephants. These measures are ideally suited for monitoring the long-term effects of social disruption from poaching and a variety of other management concerns. 相似文献
966.
A Systematic Test of an Enterprise Strategy for Community-Based Biodiversity Conservation 总被引:6,自引:0,他引:6
N. Salafsky H. Cauley G. Balachander B. Cordes J. Parks C. Margoluis S. Bhatt C. Encarnacion D. Russell R. Margoluis 《Conservation biology》2001,15(6):1585-1595
Abstract: A commonly held belief is that if people can benefit financially from enterprises that depend on nearby forests, reefs, and other natural habitats, then they will take action to conserve and sustainably use them. The Biodiversity Conservation Network brought together conservation and development organizations and local communities to systematically test this hypothesis across 39 conservation project sites in Asia and the Pacific. Each project implemented one or more community-based enterprises such as setting up an ecotourism lodge, distilling essential oils from wild plant roots, producing jams and jellies from forest fruits, harvesting timber, or collecting marine samples to test for pharmaceutical compounds. Each project team collected the biological, enterprise, and social data necessary to test the network's hypothesis. We present the results of this test. We found that a community-based enterprise strategy can lead to conservation, but only under limited conditions and never on its own. We summarize the specific conditions under which an enterprise strategy will and will not work in a decision chart that can be used by project managers to determine whether this strategy might make sense at their site. We also found that an enterprise strategy can be subsidized and still create a net gain that pays for conservation. Based on our experiences, we recommend developing "learning portfolios" that combine action and research to test other conservation strategies. 相似文献
967.
968.
Uptake of Chromium by Trees: Prospects for Phytoremediation 总被引:3,自引:0,他引:3
969.
970.