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321.
322.
The Channel of Santa Cruz is a mangrove area in northeastern Brasil 40 km north of Recife. Until 1991 a chlor-alkali factory
discharged large amounts of mercury into the main tributary of the channel, the Rio Botafogo. The objective of this study
was to assess the potential of the mangrove oyster Crassostrea rhizophorae as a bioindicator for mercury in this area and to examine the influence of condition on mercury concentrations in the oysters.
The investigation was carried out in the late rainy season (July to September) 1993, in the rainy season (April to June) 1994
and in the dry season (November/December) 1994. At 11 stations in the channel, mangrove oysters, surface sediments and suspended
matter were sampled, representing different compartments of the system. The distribution of mercury in the Channel of Santa
Cruz exhibited for all compartments the same distinct spatial pattern with maxima in the Rio Botafogo. Seasonal variations
were small and revealed no clear tendencies. In addition, mangrove oysters were transplanted from more contaminated stations
to less contaminated stations and vice versa. These experiments were designed to study the oysters' capability to adjust their
mercury concentrations to a changing bioavailability of mercury. The transplantation experiments suggest that the oysters
are capable to adjust to changing ambient mercury availability within a few months. The transplantation experiments also revealed
the importance of condition changes on the mercury concentration of the oysters. This factor should not be ignored during
pollution studies. However, condition had apparently no strong influence on the spatial or seasonal mercury variations of
the oysters. The mangrove oyster is a suitable bioindicator for long-term changes in mercury availability.
Received: 20 August 1997 / Accepted: 15 January 1998 相似文献
323.
Wolf U. Blanckenhorn James W. A. Grant Daphne J. Fairbairn 《Behavioral ecology and sociobiology》1998,42(1):63-70
The monopolization of resources plays an important theoretical role in the literature on competition for food and mates.
We used 12 groups of male water striders (Aquariusremigis) to: (1) test the general prediction that monopolization of both food and mates decreases as the temporal clumping of resources
increases, (2) compare the efficiency of two indices of resource monopolization, coefficient of variation and Q (Ruzzante et al. 1996), and (3) quantitatively assess the resource queue model of Blanckenhorn and Caraco (1992). Each group
of six males competed for both food items and mates released from the upstream end of a laboratory stream. The mean inter-arrival
time for resource units (food or females) was 10 min, with four levels of temporal clumping (variance in inter-arrival time:
0, 25, 50 or 320 min2). As predicted, the monopolization of both food and mates decreased as the temporal clumping of resource arrival increased,
although monopolization was greater for food than for mates. Q detected the difference in monopolization of food and mates, whereas the coefficient of variation did not, because Q is independent of mean resource abundance. The resource queue model successfully predicted monopolization of both resource
types, explaining 89% and 76% of variation in the proportion of food and mates acquired by the six males. The success of the
model suggests that the scaling of handling time to the variance in resource inter-arrival time should play an important role
in any general theory of resource monopolization.
Received: 28 February 1997 / Accepted after revision: 26 September 1997 相似文献
324.
Bushcricket song structure and predation by the acoustically orienting parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) 总被引:2,自引:0,他引:2
Gerlind U. C. Lehmann Klaus-Gerhard Heller 《Behavioral ecology and sociobiology》1998,43(4-5):239-245
Males of most bushcricket species produce acoustic advertisement signals to attract females for mating. These signals can
also increase conspicuousness to predators. In the genus Poecilimon (Orthoptera: Phaneropterinae) males are attacked by the parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) which locates males by their calls. In Greece T.leonidei parasitizes several Poecilimon species with different song structures: we examined whether host choice is related to song structure by comparing parasitism
rates in two closely related Poecilimon species. One of these species produces monosyllabic songs, the songs of the other species being polysyllabic. The tachinid
fly parasitized the polysyllabic species to a greater extent. We demonstrate in a field-experiment that this preference for
the polysyllabic species does not depend on local adaptations of the fly. The most probable explanation for the preference
of the fly for the polysyllabic singing species seems to be better detection of longer songs. This result is discussed in
the context of male song evolution.
Received: 4 November 1997 / Accepted after revision: 22 March 1998 相似文献
325.
326.
327.
Johannes H. P. Hackstein Peter Langer Jörg Rosenberg 《Environmental monitoring and assessment》1996,42(1-2):39-56
It has been assumed that the feeding habits of animals predispose the composition of the microbial biota living in their intestinal tracts. Here we show that in arthropods and vertebrates the presence of methanogenic bacteria requires a quality of the host that is under phylogenetic rather than dietary constraint: competence for intestinal methanogenic bacteria is a primitive-shared character among reptiles, birds, and mammals, and a shared-derived trait of millipedes, termites, cockroaches and scarab beetles. The presence of methanogenic bacteria seems to be a prerequisite for the evolution of anatomic specializations of the intestinal tract such as hindguts, caeca or rumina, and it is likely that it also has consequences for the reproductive strategies of the animals.Methanogenic animals contribute to atmospheric methane by their breath and faeces. Because the status as either methane-producer or non-producer is shared by most species belonging to a higher taxonomic unit, it is possible to calculate methane emissions that are characteristic for whole taxa. In combination with ecological field data on the biomass it is possible to arive at estimates concerning the global contributions by animals.The demonstration of a genetic basis for the symbiosis between methanogens and animals will allow new approaches for the reduction of methane emission by domestic animals. 相似文献
328.
Methylotrophic bacteria inhabit the surface of plant organs, but the interaction between these microbes and their host cells is largely unknown. Protonemata (gametophytes) of the moss Funaria hygrometrica were cultivated in vitro under axenic conditions and the growth of the protonemal filaments recorded. In the presence of methylobacteria (different strains of Methylobacterium), average cell length and the number of cells per filament were both enhanced. We tested the hypothesis that auxin (indole-3-acetic acid, IAA), secreted by the epiphytic bacteria and taken up by the plant cells, may in part be responsible for this promotion of protonema development. The antiauxin parachlorophenoxyisobutyric acid (PCIB) was used as a tool to analyze the role of IAA and methylobacteria in the regulation of cell growth. In the presence of PCIB, cell elongation and protonema differentiation were both inhibited. This effect was compensated for by the addition of different Methylobacterium strains to the culture medium. Biosynthesis and secretion of IAA by methylobacteria maintained in liquid culture was documented via a colorimetric assay and thin layer chromatography. Our results support the hypothesis that the development of Funaria protonemata is promoted by beneficial phytohormone-producing methylobacteria, which can be classified as phytosymbionts. 相似文献
329.
Sugumar G Chrisolite B Velayutham P Selvan A Ramesh U 《Journal of environmental biology / Academy of Environmental Biology, India》2008,29(3):387-391
Theprevalence and seasonal variation of bacterial indicators of faecal pollution such as total coliform bacteria, faecal coliform bacteria, Escherichia coli and faecal streptococci were investigated in samples of water and beach sand from the four fish landing centres of Thoothukudi. Further the samples were screened for Salmonella to study the reliability of faecal indicator bacteria as an index of human pathogenic bacteria. Total coliform bacteria, faecal coliform bacteria and Escherichia coli were isolated from all four landing centres from undetectable to the maximum detectable level of over Most Probable Number 140 throughout the year with no obvious seasonal variation. Faecal streptococci were also detected in most samples. There was no discernable relationship between faecal indicators and physical parameters. The relationship between faecal indicators and Salmonella was not significant (p > 0.05). The results showed that the coastal waters along Thoothukudi is polluted and presents a potential risk to public for recreational and fishing activities. 相似文献
330.
Kurnaz A Kucukomeroglu B Damla N Cevik U 《Journal of environmental radioactivity》2011,102(4):393-399
The activity concentrations and absorbed gamma dose rates due to primordial radionuclides and 137Cs have been ascertained in 222 soil samples in 18 counties of the Trabzon province of Turkey using a HPGe detector. The mean activity concentrations of 238U, 232Th, 40K and 137Cs in soil samples were 41, 35, 437 and 21 Bq kg−1, respectively. Based on the measured concentrations of these radionuclides, the mean absorbed gamma dose in air was calculated as 59 nGy h−1 and hence, the mean annual effective dose due to terrestrial gamma radiation was calculated as 72 μSv y−1. In addition, outdoor in situ gamma dose rate (D) measurements were performed in the same 222 locations using a portable NaI detector and the annual effective dose was calculated to be 66 μSv y−1 from these results. The results presented in this study are compared with other parts of Turkey. Radiological maps of the Trabzon province were composed using the results obtained from the study. 相似文献