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1.
The effects of dissolved Pb, Cd and Hg on growth and survivalof adult Biomphalaria glabrata Say. uninfected and infectedwith Schistosoma mansoni Sambon, were examined. Pb at concentrationsfrom 0.25–100 µM, Cd from 0.075–0.25 µMand Hg from 0.25–1 µM significantly reduced growthand survival of normal snails. With each metal the effects increasedwith increasing concentration. The LC 25 at 2 wks exposure was82 ± 19, 0.22 ± 0.04 and 0.94 ± 0.13 µM(x ± S.E.) for Pb, Cd and Hg, respectively. Snails exposedto heavy metals continued to be reproductively active, but theegg production was highly variable and no significant effectof heavy metal exposure was demonstrated. Infection also decreasedsurvival and growth of snail hosts and infected individualsexposed to heavy metals displayed the greatest mortality. TheLC 25 for infected snails at 2 wks exposure was 8 ± 3,0.9 ± 0.02 and 0.29 ± 0.08 for Pb, Cd and Hg respectively.A significant interaction between heavy metal exposure and infectionwas apparent. Infected snails were not reproductively active.Cercarial shedding by infected snails was significantly reducedin the presence of heavy metals and by 6 wks shedding had ceasedat the highest metal concentrations. (Received 20 May 1996; accepted 31 July 1996)  相似文献   

2.
Growth (assessed from intermolt period and molt increment) andmetabolism (oxygen consumption) of the post-larva of Euphausiapacifica from the southern Japan Sea were determined at sevengraded temperatures ranging from 1 to 25°C. The intermoltperiod shortened progressively as temperature increased from1 to 20°C, but an effect of temperature on molt-to-moltgrowth increment was not seen. Oxygen consumption rates wereaccelerated by the increase in temperature up to 20°C. Beyond20°C, E.pacifica exhibited reduced oxygen consumption anddied within 1 day without molting. After removing the effectof body size, the relationships between growth rate and temperature,and between oxygen consumption rate and temperature, were established.The carbon budget was calculated as a function of temperature.Because of differential effects of temperature on growth andmetabolism, the net growth efficiency [K2 growthx100/(growth+metabolism)]changed with temperature. The optimum temperature at which E.pacificaattained the maximum K2 was 11.4°C, which was derived fromcalculation of cumulative carbon invested in growth and metabolismin this animal. In an alternative method, the optimum temperaturewas obtained mathematically by solving a set of differentialequations. The biological and ecological significance of theoptimum temperature which leads to the maximum K2 is discussed.  相似文献   

3.
Experiments with photoperiods ranging from 2 to 24 h confirmthat 8 h light per day is optimal for Lunularia: there is nogrowth in the dark or in continuous light, which causes therapid onset of dormancy. Short-day cycles intercalated amonga series of continuous light cycles promote growth; in cycleslonger than 24 h very long dark periods are detrimental. Withvery short photoperiods (5 min) red light promotes growth moreeffectively than white light at higher intensity; far-red actsas dark. The growth effects of red and far-red light breaks(3 min) depended on the time of application; red light inhibitedin the middle but promoted at the beginning of the 16-h darkperiod of a short day; far-red light had the opposite effect;in each case red and far-red effects were reversible by theother wavelength. Blue light gave the same response as red includingthe reversibility of far-red effects and vice versa. Surprisingly,significant effects of 5 min red, blue, and far-red irradiationwere also found in the middle of the main high-intensity white-lightperiod, red and blue promoting growth, far-red reducing it;again there was ready reversibility of the effects. Growth promoters of higher plants are generally inhibitory toLunularia or have little effect; among growth retardants TIBA,Phosphon D, and CCC gave a slight promotion of growth. EDTApromoted growth (cell numbers) very significantly while 8-hydroxyquinolinewas initially inhibitory, but had a marked latent promotingeffect when subsequently washed from the thalli.  相似文献   

4.
Cadmium, copper and lead were examined in whole snails fromthe Lower Nelson River system. Concentrations of the three metalswere significantly correlated with each other. Lead was accumulatedleast, while copper was present in the greatest concentrations.Significant interspecific differences were found for copper.Total body burdens increased with snail size and weight, butconcentrations per unit dry weight decreased with size and weightin some species. Metal concentrations in snails were not significantlycorrelated with metal content of the sediments. In Gyraulus,copper and lead concentrations were correlated with levels ofthese metals in the host macrophytes. Seasonal differences inmetal concentration appeared to be related to differences inage structure of the populations. (Received 5 September 1991; accepted 30 October 1991)  相似文献   

5.
The effect of body size on the oxygen consumption and metabolicrate of Cerithidea (Cerithideopsilla) cingulata (Gmelin, 1790)andCerithium coralium Kiener, 1841 was studied at a constant temperatureof 25°C. An exponential relationship has been observed inboth animals. Oxygen consumption showed a positive linear correlationwith a ‘b’ value of 0.6518 in C. cingulata and 0.7667in C. coralium. A negative linear correlation was obtained forthe metabolic rate with a (b-1) value of –0.3482 in C.cingulata and –0.2333 in C. coralium.  相似文献   

6.
Population density and daily rate of growth in relation to waterchemistry in the prosobranch gastropods Bithynia graeca andViviparus contectus were studied in the artificial Lake Kerkiniand in the marshes of Strymonas River upstream of its entryto Lake Kerkini (Serres Macedonia, N. Greece) respectively.PO4-Pconcentration proved to be the most significant hydro-logicalparameter for the density and the rate of daily growth in B.graeca. The water variable which proved to be significant forthe density of V. contectus was dissolved oxygen.B. graeca iscapable of true tissue-degrowth (40% loss of tissue dry mass)with low mortality rate during winter. (Received 24 March 1994; accepted 9 January 1995)  相似文献   

7.
After growing barley (Hordeum vulgare L.) in nutrient solutionscontaining EDTA, uptake of the nutrient metals was determinedat three harvests and concentrations of the various chemicalspecies of each metal in the growth solutions was modelled bycomputer simulation. Complexation with EDTA had different effectson the uptake of the ions Fe3+, Mn2+, Cu2+, and Zn2+. At thehighest EDTA level (EDTA/Fe=2/l) the plants were chlorotic andgrowth was inhibited. This is attributed to a deficiency inZn rather than in Fe. The critical level of free Zn2+ requiredin nutrient solutions for healthy growth was found to be approximately10–1010–10 mol dm–3, which is consistent withthat found by earlier workers for other plant species. Barleytolerated much lower levels of the free ions of copper and ironwithout exhibiting any obvious adverse effects. Key words: EDTA, micronutrients, trace metals, computer simulation, deficiencies, absorption, iron, manganese, copper, zinc  相似文献   

8.
This paper examines the biology and ecology of Helix lucorumL. which lives in mainland Greece, as well as its growth andsecondary production. A demographic study revealed that (a)3 cohorts exist at any time during the year (when adults ofall generations belong to the same cohort) (b) egg-laying andhatching occur during the months of July and August respectively,(c) the most rapid growth takes place during spring. Study ofH. lucorum genitalia in relation to age showed that the snailsaxe sexually mature 3 years after hatching, when the largestdiameter of their shell (D) is equal to or greater than 35 mm Von Bertallanffy's method suggests that Helix lucorum may liveup to 14 years or more in order to reach its possible maximumsize (48.80 mm) The study of relative growth of D in relation to Ps (peristomesurface) of Helix lucorum shows that D grows faster than Pswhen D12.50 mm; juveniles change their growth rate when theirD arrives at 22.05 mm, and growth becomes slower when adultsarrive at 36.27 mm Annual secondary production calculated by the size frequencymethod gave a mean annual density of 3.39 individuals per m2,a mean annual crop (biomass) of 4.04 g-m–2 and an annualproduction (P) of 5.02 g · m–2. The annual turnoverratio (P//b) is equal to 1.24 (Received 23 June 1987;  相似文献   

9.
Growth (assessed from intermolt period and molt increment) andmetabolism (oxygen consumption) of juvenile and adult Thysanoessalongipes from central Japan Sea were determined at eight differenttemperatures ranging from 0 to 14°C. The intermolt periodshortened progressively as temperature increased from 0 to 14°C.The molt increment was not assessed satisfactorily in the rearingexperiments, and therefore this was estimated from the naturalgrowth curve and habitat temperature, combined with laboratory-obtainedintermolt data. Oxygen consumption rates increased exponentiallyfrom 0 to 8°C and then leveled off. From these results,the growth was expressed as a function of temperature and bodysize and metabolism as a function of temperature. Because ofthe differential effects of temperature on growth and metabolism,the net growth efficiency [NGE: 100 x growth/(growth + metabolism)]changed with temperature. The temperature at which T. longipesattained maximum NGE varied from 0 to 8°C, depending onthe body length of specimens of 5, 10, 15 and 20 mm. The presentresults are compared with our previous data on Euphausia pacificain relation to the body composition and habitat usage of thesetwo trophically important species in the food web of the JapanSea.  相似文献   

10.
Cellana grata is a high-zoned, exposed-shore limpet with a lifespanof 3 years. Patclloida pygmaeais a low-zoned, sheltered-shorelimpet with a lifespan of I year. C. grata migrates up-shorein winter, but occurs lower on the shore in summer. This migrationis synchronized with variations in algal availability high onthe shore; such variations are, however, themselves relatedto seasonal changes in wave height. P. pygmaea is restrictedto the low shore, year round. The movements upwards in winterand downwards in summer are still evident. Algal species richnessincreased from September to reach a peak between December andMarch, and to abruptly diminish between May and June. The encrustingalgae Brachytrichia maculans, Hildenbrandia prototypus, Lithothamnionsp. and Ralfsia vcrrucosa were present year round. The timingof juvenile recruitment of C. grata and P. pygmaea was fromOctober to July and February to October, respectively. Temperaturemay be important in enhancing juvenile survival by affectingthe seasonal pattern of algal occurrence on the shore. Seasonalfluctuations in the rate of growth were recorded for both specieswith the time of fastest growth of C. grata and P. pygmaea occurringbetween October and March and September and February, respectively.Mortality of both species occurred mainly in summer. Summerheat, predation and intra-specific competition for food appearto be the major causes of death. (Received 1 December 1992; accepted 5 May 1993)  相似文献   

11.
Barley (Hordeum vulgare L.) plants were grown in nutrient solutionscontaining the chelating agent, DTPA. The experiments replicatedthose reported in the preceding paper in which EDTA was thechelating agent used. The concentrations of all the chemicalspecies of metals were stimulated using the program NUTRIENT.The concentrations of DTPA used were chosen to give a similarrange of complexation as used in the EDTA experiments. The effectof complexation by DTPA on the uptakes of the metal ions Fe3+,Mn2+, Cu2+, and Zn2+ and on plant growth were sufficiently differentfrom those with EDTA to indicate some dependence on the natureof the chelating agent used. The biggest difference betweenthe EDTA and DTPA experiments occurred in the solutions containingthe largest concentrations of these reagents. With DTPA, chlorosiswas seen only in the early stages; otherwise the plants showednormal growth. A simple chemical model for metal uptake is discussed. Key words: DTPA, EDTA, micronutrients, trace metals, computer simulation, plants, absorption, iron, manganese, copper, zinc  相似文献   

12.
该实验选取处于生长期的油松(Pinus tabulaeformis)幼苗,研究土壤Cu、Cd胁迫条件下,美味牛肝菌(Boletus edulis)单独接种、红绒盖牛肝菌(Xerocomus chrysenteron)与美味牛肝菌混合接种处理,对油松幼苗的生长和重金属积累分布状况的影响,探讨不同接种对油松抗性的影响。研究发现,菌根接种不仅促进寄主油松的生长发育和生物量积累,而且显著降低油松体内的重金属积累浓度,减少重金属由根部向植物茎叶部分的转运。与单一接种相比,混合接种可以更加有效地缓解重金属对寄主的生物毒性,减少土壤中重金属元素向油松体内的转运。这种优势在高浓度的重金属胁迫环境下尤为明显。该实验中,在3 mg·kg-1 Cd胁迫下,混合菌根油松的茎叶和根部Cd浓度仅为未接种对照的59.1%和70.7%,比单一菌根降低了11.3%和18.1%,而混合菌根植物的茎叶和根部生物量干重则分别为未接种对照的1.14和1.20倍,单一菌根为未接种对照的1.18和1.17倍。在400 mg·kg-1Cu胁迫下,混合菌根植物茎叶和根部的干重分别是未接种植株的1.01和1.09倍,而混合菌根植物茎叶和根部的Cu浓度仅为未接种植株的61.8%和79.6%,比Boletus edulis菌根植物的Cu积累浓度下降了0.7%和3.8%。  相似文献   

13.
  1. MH was found to suppress the growth and respiration of E. colias well as the IAA-induced growth of Avena coleoptile sections.
  2. These suppressions could be reversed more or less strikinglyby the addition of a trace of heavy metals such as Co, Mn, Ni,Zn, Cu, or Mo.
  3. The reversal could also be achieved by cysteine,thioglycollate,or fumarate, the latter two substances being,however, lesseffective.
  4. The inhibition of the growth of E.coli by MH was completelyrelieved by the addition of IAA. Conversely,the inhibitionof the microbial growth by high concentrationsof IAA couldbe relieved by the addition of MH.
  5. It was inferredthat MH may block certain heavy metal-catalyzedprocess, inwhich some thiol substance and IAA are participating,probablyby combining with the heavy metal.
(Received June 23, 1960; )  相似文献   

14.
To obtainHylocomium splendens (Hedw.) BSG. that varied in metal(K, Mg, Ca and Zn) content, moss samples were collected fromsix sites around a zinc contaminated area of Latvia; metal contentswere artificially lowered by branch excision. The first fullyexpanded annual segment (mature segments), together with theunexpanded segment (juvenile segment) were grown in the laboratorywith watering from below. The contents of K, Mg, Ca and Zn innew growth were correlated with initial contents in the juvenile+maturesegments. However, the concentrations of these metals in thenew growth were generally not correlated with those in the pre-experimentalsegments. The excision of branches from the mature segment favouredsubsequent branch development in the young juvenile segmentover further growth of the already expanded mature segment,but less new growth was observed when branches were excised. Hylocomium splendens ; growth; metal uptake; metal translocation  相似文献   

15.
The consumption of adult euphausiids was estimated for the sevenmost abundant fish species found on the continental shelf offsouthwestern Vancouver Island, British Columbia, Canada. Empiricaldata on fish feeding rates, diets and biomass were used to estimateeuphausiid consumption in August for each year from 1985 to1997. The fish community in August was estimated to consumean average 297 kt of euphausiids (124 t km–2). Pacifichake (Merluccius productus) and Pacific herring (Clupea harengus)accounted for 60% and 30%, respectively, of the total euphausiidsconsumed by fish. The total estimated consumption of euphausiidsper tonne of fish averaged 0.93, and there was no significanttrend in the time series. In addition, there was no significantrelationship between the total fish community consumption oreuphausiids consumed per tonne of fish and euphausiid biomass,and there was no change in the fraction of euphausiids in thediet of small or large Pacific hake. Thus, it appears that predationpressure from the pelagic fish community was relatively constantand not responsible for the apparent fivefold decline in adulteuphausiid biomass observed in the 1990s.  相似文献   

16.
For a single seed population of each of four species of grainlegume positive linear relationships were shown between temperatureand rate of germination for different fractions (G) of eachpopulation, from a base temperature, Tb(G), at which germinationrate is zero, to an optimum temperature, To(G) at which germinationrate is maximal. At constant temperatures warmer than To(G)there were negative relations (probably linear) between temperatureand rate of germination to the maximum temperature for germination,Tm(G), Within each population Tb(G) did not differ, but it didvary between species, viz.0.0?C, 0.25?C, 4.and 8.5?C for chickpea(Cicer arietinum L.), lentil (Lens culinaris Medic.), soyabean(Glycine max [ Merr.) and cowpea (Vigna unguiculata [L.] Walp.),respectively. In contrast, To(G) varied both within each populationand also between the four species: 80% of seeds in each populationhad To(G) values within the range 31.8?C to 33.8 ?C, 24.0?Cto 24.4?C, 34.0?C to 34.5?C and 33.2?C to >40?C, respectively.Values of Tm(G) were much more vanable: the 80% population rangewas 48 .0?C to 60.8?C for chickpea, 31.8?C to 34.4?C for lentiland 46.8?C to 55.2?C for soyabean; reliable estimates couldnot be made for cowpea, but the results suggest higher and morevariable values of Tm(G) than in the other three species. Atsub-optimal temperatures the distribution of thermal time forthe different fractions of each population was normal, exceptfor lentil where it was log-normal. A single equation is proposedto describe the influence of sub-optimal temperatures on ratesof germination for whole seed populations. At supra-optimaltemperatures, variation in thermal time for the different fractionsof each population was only slight. The implications of thesefindings for the adaptation of grain legume crops to differentenvironments, and for the screening of germplasm, are discussed. Key words: Seed germination rate, temperature, grain legumes  相似文献   

17.
On sheltered rocky beaches in Hong Kong, Linatella caudata preysupon the lower-littoral and sub-littoral fringe fauna. Ascidiantests are cut with the radula, while the proboscis is insertedbetween the parted shell valves of bivalves. The salivary glandssecrete sulphuric acid that is not used in prey penetration,as in the Cassidae, but is more likely used in digestion ordefence. In preference experiments, prey were chosen in the sequence:Barbatia virescens (Bivalvia: Arcidae) > Styela plicata (Ascidiacea)/Saccostreacucullata (Bivalvia: Ostreidae) > Lunella coronata (Gastropoda:Turbinidae) > Balanus amphitrite (Crustacea: Cirripedia).52% of all attacks were upon Barbatia Lunella and Balanus wereattacked rarely. Prey preferences by individual gastropods werealso demonstrated. Calibration plots of total weight against wet and dry tissueweight of prey (Barbatia virescens) and, finally, the predatorwere obtained and used in estimations of consumption. On average,an adult Linatella caudata (10-15g) consumed three B. virescens.week–1 The mean weight of B. virescens flesh consumed.week–1 ranged between 0. 208–0.412g dry weight prey.gdry weight predator–1, i.e., a mean of 28.2% of the predator'body weight.week–1 or 4%.day–1. Such a figure accordswell with estimates of consumption obtained for other adultpredatory gastropods from Hong Kong. (Received 4 September 1989; accepted 5 December 1989)  相似文献   

18.
Data are presented on population and individual parameters fora population of Cerastoderma glaucum Bruguière livingin a small, almost closed mixohaline lagoon in southern England.The bivalve occupies two discrete niches, a benthic one anda semi-pelagic one, where juveniles are suspended in the floatingalga Chaetomorpha linum Kutz. During the study year (1972) therewas no growth in the benthic population. This was shown to bean unusual occurrence by comparing growth data obtained by severaldifferent techniques, including the microscopic examinationof shell growth lines. Reproductive condition followed the monocyclicpattern already established for this species in northern localities,with spawning taking place in May. Ash content, water contentand calorific content all varied in correspondence with thelevel of starvation, which proceeded with insignificant mortalityuntil body weight was reduced to about a quarter of that atthe beginning of the year. At this point calorific values aslow as 3.5 kcal/g were measured. Possible causes for the anomalousnegative production are considered. The most likely factor responsiblewould appear to be the high production of the alga Chaetomorphalinum which would effectively compete out the phytoplanktonfood of the Cerastoderma population. * Present address: Institut für Physiologische Chemie,Abt. Zellbiochemie, Universität Hamburg. Martinistrasse52, 2000 Hamburg 20, F.R.G. (Received 6 November 1978;  相似文献   

19.
The expolinear equation for crop growth (Goudriaan and MonteithAnnalsof Botany66: 695–701, 1990) was fitted to measurementsof above ground dry weight made on two cultivars of each ofthree species, faba bean (Vicia fabaL.), peas (Pisum sativumL.)and lentils (Lens culinarsMedic.), each grown at three densitiesat the University of Reading, UK in 1992 and 1993. The expolinearequation fitted the data well but required frequent samplingto obtain good estimates of the parameters. The equation hasthree parameters,Rmthe maximum relative growth rate,Cma maximumcrop growth rate, andtbthe time at which the crop effectivelyreaches a linear phase of growth.Rmdid not differ between densities,cultivars or species but differed between years.Cmincreasedwith increased density and was lower for lentils than for fababeans or peas.tbdecreased with increased density for faba beanbut not for the other species. Incorporating an extinction coefficientfor solar radiation and the maximum fraction of radiation interceptedenabled reasonably accurate time courses of leaf area indexto be derived, as suggested by Goudriaan (1994. In: MontiethJL, Scott RK, Unsworth MH, eds.Resource capture by crops. Nottingham:Nottingham University Press, 99–110).Copyright 1998 Annalsof Botany Company Expolinear equation, grain legumes, crop growth rate, crop density, relative growth rate, growth modelling, faba bean,Vicia fabaL., peas,Pisum sativumL., lentils,Lens culinarsMedic.  相似文献   

20.
The absorption spectrum of intact cels of Rhodotorula mucilaginosaexhibits three absorption peaks for carotenoids and a Soretband for cytochrome(s). The difference spectrum between thereduced and oxidized states indicates there are components ofcytochrome b, c(c1) and a+a3. However, the respiratory aspectof this strain differs significantly from that of baker's yeast,Saccharomyces cerevisiae. The respiratory capacity is strikinglyenhanced in the transition from the lag to the logarithmic phaseof growth, and is accompanied with a special increase in cytochromeoxidase. Addition of TMPD (plus ascorbate) in the presence ofglucose barely affects oxygen consumption of the cells duringthis period, whereas it markedly affects consumption in oldercells. Sodium azide slightly inhibits respiration in the courseof growth, except during this limited transitional period. Azide-insensitiverespiration is also seen in the mitochondrial fraction preparedfrom cells grown to the stationary state. A similar situationis found with antimycin A. Morphological investigations were carried out electron-microscopicallyon the cells of different growth stages. (Received September 16, 1969; )  相似文献   

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