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161.
Behavioral aspects of sperm competition in cuttlefish, Sepia officinalis (Sepioidea: Cephalopoda) 总被引:6,自引:0,他引:6
Sexual selection studies in cephalopods indicate that sperm competition is a central feature of their mating systems, yet
this has not been studied experimentally in any detail. In 1998 we staged 20 matings of the cuttlefish, Sepia officinalis L., in the laboratory. Males rapidly initiated mating in the “head-to-head” position, with no apparent courtship. Mating
lasted an average of 10 min (range 7 to 14 min). For the first 6 min (on average 63% of the mating duration), the male flushed
strong jets of water directly at the female's buccal membrane, which sometimes resulted in the expulsion of parts of spermatangia
placed there in recent matings. Then, in a single discrete movement that lasted an average of only 14 s, the male's modified
fourth left arm – the hectocotylus – wrapped around a single large bundle of spermatophores (ca. 150 to 300) and transferred
them to the female's buccal membrane. For the remainder of the mating (average 3 min, range 1.5 to 5.0 min), the hectocotylus
repeatedly broke the spermatophores open, and manipulated them, so that sperm were released and many spermatangia were attached
along the ventral buccal membrane, near the paired seminal receptacles. Approximately 140 spermatangia were attached in rows
3 to 5 deep around the ventral buccal membrane in a single mating; the rest were usually discarded during mating. Histology
revealed that each of the seminal receptacles consists of a series of sperm storage bulbs connected by a central duct, which
leads to a single pore at the surface of the buccal membrane. Baseline data on sperm motility were obtained, but the mechanism
by which sperm enter the seminal receptacle remains unknown. Females seemed to initiate termination of mating, then males
guarded their mates temporarily. These results, combined with other recent laboratory experiments, provide evidence that sperm
competition may be a major feature of the mating system of S. officinalis.
Received: 4 January 1999 / Accepted: 18 May 1999 相似文献
162.
Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers 总被引:1,自引:0,他引:1
A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO3, FeCO3, and Fe(OH)2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO3-, Ca2+, CO3(2-), and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO3 and FeCO3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant. 相似文献
163.
Saiki MK 《Environmental pollution (Barking, Essex : 1987)》1987,47(3):171-186
Analysis of mosquitofish, Gambusia affinis, has proven useful for monitoring contaminant levels in aquatic biota; however, the small size of this species often requires the compositing of several fish to provide sufficient biomass for selenium analysis. Such composites have usually been obtained without considering the length and sex of the individual fish. The present study found significant differences in mean lengths and sex ratios of mosquitofish sampled with small-mesh dip nets from five sites close to each other in the San Joaquin Valley, California. To test the effect of these different sample characteristics, fish from each site were divided by sex into five size classes (<20, 20-30, 31-45, 46-60, and >60mm total length) before analysis for total selenium. Altogether, fish from the San Luis Drain and Kesterson Ponds 2 and 7 contained 65-360 microg g(-1) selenium (dry weight basis), or about 28- to 300-fold more than concentrations in fish of the same length and sex from the Volta Wasteway and Volta Pond 26. Except for females 31-45 mm long from the San Luis Drain that had higher concentrations than either smaller or larger females, selenium concentrations did not differ significantly among size classes. Although concentrations differed between sexes in samples from the San Luis Drain, Kesterson Pond 2, and Volta Pond 26, neither males nor females consistently had the higher concentrations. In the San Luis Drain, 20-30 and 31-45 mm long females had higher concentrations than did males of the same size classes; in Kesterson Pond 2 and Volta Pond 26, however, 20-30 mm long males had higher concentrations than did females of the same size class. Although no consistent patterns were observed, the occasional differences in selenium concentrations in fish of different length and sex indicate that these variables should be considered when surveys and monitoring studies are designed. 相似文献
164.
Knutson AB Klerks PL Levinton JS 《Environmental pollution (Barking, Essex : 1987)》1987,45(4):291-304
The distribution of heavy metal contaminated sediments in Foundry Cove, a freshwater embayment of the Hudson River, was examined twelve years after the discharging of wastes from a battery factory had ceased. Concentrations of Cd, Ni and Co were measured in surficial sediments (top 5 cm) and seven detailed depth profiles. Comparison with earlier surveys showed that metal levels of surficial sediments have been considerably reduced throughout the cove. Evidence suggests that this reduction may be largely due to burial rather than transport of metals out of the cove or a redistribution (via sediment resuspension and redeposition) within the cove. This is suggested by the presence of a peak in metal concentrations at a depth of several centimetres in depositional environments, a calculation showing the loss of waterborne cadmium to be much less than the amount of cadmium lost from the surficial sediment, and the absence of increased pollution in the cleaner parts of the cove. Despite improvement, metal levels remain extremely high, including a persistent 'hot-spot' with levels higher than 10 000 ppm Cd. 相似文献
165.
Electrochemical oxidation of bisphenol A. Application to the removal of bisphenol A using a carbon fiber electrode 总被引:19,自引:0,他引:19
Leachate samples with a high strength of ammonium-nitrogen (NH4+-N) were collected from a local landfill site in Hong Kong. Two experiments were carried out to study (1) the inhibition of microbial activity of activated sludge by NH4+-N and (2) the chemical precipitation of NH4+-N from leachate as a preliminary treatment prior to the activated sludge process. The experimental results demonstrated that the efficiency of COD removal decreased from 97.7% to 78.1%, and the dehydrogenase activity of activated sludge decreased from 9.29 to 4.93 microg TF/mg MLSS, respectively, when the NH4+-N concentration increased from 53 to 800 mg/l. The experiment also demonstrated that the NH4+-N in the leachate can be quickly precipitated as MgNH4PO4 x 6H2O after addition of MgCl2 x 6H2O + Na2HPO4 x 12H2O. The NH4+-N concentration was reduced from 5618 to 112 mg/l within 15 min when a molar ratio of Mg2+:NH+:PO4(3-) = 1:1:1 was used. The optimum pH to reach the minimum solubility of MgNH4PO4 x 6H2O was found to be in the range of 8.5-9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl2 x 6H2O + Na2HPO4 x 12H2O, which may affect microbial activity in the following biological treatment processes. Using two other combinations of chemicals [MgO + 85%H3PO4 and Ca(H2PO4)2 x H2O + MgSO4 x 7H2O] could minimise salinity generation after precipitation, while they were less efficient for NH4+-N removal. 相似文献
166.
Effects of bis(tributyltin)oxide on antipredator behavior in threespine stickleback Gasterosteus aculeatus L. 总被引:1,自引:0,他引:1
Antipredator behavior was used as a parameter to detect effects caused by exposure to the organotin compound bis(tributyltin)oxide (TBTO). Three groups of threespine sticklebacks (Gasterosteus aculeatus L.) were exposed to 3, 9 and 27 ppb TBTO, respectively. A fourth control group was given the same treatment as the other three groups, but no TBTO. Antipredator behavior of the fish was evoked using a dummy heron (Ardea cinerea) bill. TBTO exposure caused significant changes in the spatial position of the fish in the aquarium (P(Loc)), their response to predator attack (P(Res)), recovery time (P(Rec)) and latency time (P(Lat)). Some of the effects were, however, reversible after the exposure was terminated. We suggest that behavior as an indicator of pollution may be used as an ecologically relevant integrative biomarker. 相似文献
167.
The sensitivity of surface waters of Great Britain to acidification predicted from catchment characteristics 总被引:7,自引:0,他引:7
Hornung M Bull KR Cresser M Ullyett J Hall JR Langan S Loveland PJ Wilson MJ 《Environmental pollution (Barking, Essex : 1987)》1995,87(2):207-214
Using a combination of soil, land use and geological information, a map of Great Britain has been derived which indicates the sensitivity of surface waters to acidification. For the geological information, a slightly modified version of an available map was used which indicated the sensitivity of groundwaters to acidification. For soils, 1-km databases of soil information for England and Wales and for Scotland were employed to map the soil sensitivity as determined by buffering capacity. The derived soils map was modified to take account of agricultural liming in arable and managed grassland areas using the ITE Land Classification. The final map of surface water sensitivity was obtained by using a geographic information system overlay procedure which enabled each combination of soil and geology sensitivity to be uniquely defined. The final sensitivity classification was based upon expert knowledge and the experience of a similar sensitivity mapping exercise for Wales. 相似文献
168.
169.
Means to improve the effect of in situ bioremediation of contaminated soil: an overview of novel approaches 总被引:16,自引:0,他引:16
Romantschuk M Sarand I Petänen T Peltola R Jonsson-Vihanne M Koivula T Yrjälä K Haahtela K 《Environmental pollution (Barking, Essex : 1987)》2000,107(2):179-185
Different aspects of bacterial degradation of organic contaminants in soil, and how to improve the efficiency and reproducibility is discussed in this review. Although bioremediation in principle includes the use of any type of organism in improving the condition of a contaminated site, most commonly bacteria are the degraders and other organisms, such as soil animals or plant roots, play a role in dissemination of bacteria and, indirectly, plasmids between bacteria, and in providing nutrients and co-substrates for the bacteria active in the degradation process. There are a number of different procedures that have been tested more-or-less successfully in attempts to improve reliability, cost efficiency and speed of bioremediation. The methods range from minimal intervention, such as mere monitoring of intrinsic bioremediation, through in situ introduction of nutrients and/or bacterial inocula or improvement of physico-chemical conditions, all the way to excavation followed by on site or ex situ composting in its different varieties. In the past the rule has been that more intervention (leading to higher costs) has been more reliable, but novel ideas are continuously tried out, both as a means to come up with new truly functional applications and also as a line of studies in basic soil microbial ecology. Both approaches generate valuable information needed when predicting outcome of remediation activities, evaluating environmental risks, deciding on cleaning-up approaches, etc. The emphasis of this review is to discuss some of the novel methods for which the value has not been clearly shown, but that in our view merit continued studies and efforts to make them work, separately or in combination. 相似文献
170.
Li JT Qiu JW Wang XW Zhong Y Lan CY Shu WS 《Environmental pollution (Barking, Essex : 1987)》2006,143(1):159-165
This study examines cadmium (Cd) contamination in orchard soils and fruit trees in Guangzhou, China, and assesses its potential health risk. Soils and tissues samples of three species of fruit trees were collected from three orchards. The average soil Cd concentration was 1.27, 1.84 and 0.68 mg/kg in orchards I, II, and III, respectively. The carambola (Averrhoa carambola) accumulated exceptionally high concentrations of Cd (7.57, 10.84, 9.01 and 2.15 mg/kg dw in root, twig, leaf and fruit, respectively), being 6.0-24 times and 4.0-10 times the corresponding tissue Cd in the longan (Dimocarpus longan) and wampee (Clausena lansium), respectively. Furthermore, all Cd concentrations (0.04-0.25 mg Cd/kg fw) of the fruits exceeded the tolerance limit of cadmium in foods of PR China (0.03 mg/kg fw). Our results indicate that the carambola tree has high Cd accumulation capacity and might be a Cd accumulator; and its fruit, among the three species of fruits studied, also poses the highest potential health risk to local residents. 相似文献