共查询到20条相似文献,搜索用时 15 毫秒
1.
The invertebrate fauna of many Antarctic ice-free areas, even those close to permanent research stations, can be poorly known.
Here we describe some nematodes from freshwater and saline, marine-derived lakes of the Vestfold Hills, East Antarctica. The
freshwater lakes contained the widespread East Antarctic endemic species, Plectus frigophilus Kirjanova, 1958. The saline lakes were inhabited by two recently described species, Halomonhystera halophila Andrássy, 2006 and Halomonhystera continentalis Andrássy, 2006, and by a new species described in this report, Hypodontolaimus antarcticus sp. n. Originally marine but now brackish Highway Lake contained a nematode fauna with both freshwater and marine-derived
components. The nematode fauna of Antarctica now consists of 54 named species, 22 of which are found in East Antarctica. 相似文献
2.
We evaluated the response of the Antarctic soil nematodes Scottnema lindsayae and Plectus antarcticus to various salts (NaCl, MgSO4, KNO3 and NaCl + MgSO4) and salt concentrations in prepared salt solutions ranging from 0.1 to 3 M, and in saturation paste extracts of soils collected from multiple locations where nematode abundance varied from zero to numerous, and where electrical conductivity ranged from 108 to >12,000 μS/cm. Nematode salt tolerance was salt specific; both nematode species survived in low-experimental concentrations of NaCl and MgSO4, and neither species survived in KNO3 solutions of any concentration. There was no survival of nematodes in the saturation paste extracts of highly saline soils (4,100 μS/cm), while survival was over 80–97% in less saline soils (1,945 μS/cm). A 1:1 dilution of these highly saline saturation paste extracts increased S. lindsayae survival to 80%, while survival of P. antarcticus was not observed until dilutions of greater than 200%. The results complement previous studies demonstrating niche partitioning of S. lindsayae and P. antarcticus across salinity gradients and strengthen interpretations of the physiological mechanisms underlying previously reported spatial correlation between soil salinity and nematodes abundance in the Antarctic Dry Valleys. 相似文献
3.
Eleanor B. Mackay Ian D. Jones Andrew M. Folkard Stephen J. Thackeray 《Hydrobiologia》2011,666(1):85-97
Community structure and diversity patterns of pelagic copepods were investigated for the coastal areas and in the marine lakes
of the Palau islands in the West Pacific. We conducted field surveys during 2004–2007 and collected zooplankton samples from
eight coastal areas and 16 marine lakes. The marine lakes in the islands of Palau are limnologically classified into two types,
meromictic and holomictic lakes. Species diversity indices (Margalef’s species richness d′, Shannon–Wiener index H′, and Simpson’s dominance) were measured at each sampling site. The copepod community structure was analyzed using multivariate
analyses, hierarchical cluster analysis, and non-metric multidimensional scaling (MDS) from the PRIMER package. A total of
36 copepod taxa were identified to the genus or species level from Calanoida, Cyclopoida, Harpacticoida, and Poecilostomatoida.
Multivariate analysis based on the Bray–Curtis similarity index revealed that copepod assemblages could be classified into
three different groups according to their habitat: (I) meromictic lakes, (II) holomictic lakes with an exceptionally shallow
and flat basin (type A holomictic lakes), (III) holomictic lakes with a deep basin (type B holomictic lakes), and all coastal
areas. The meromictic lakes were characterized by markedly decreased species diversity (d′ = 0.15, H′ = 0.41) in which only two brackish-water species, Bestiolina similis and Oithona dissimilis, were dominant. Type A holomictic lakes were characterized by relatively low levels of species diversity (d′ = 1.25, H′ = 1.35). In contrast, type B holomictic lakes were characterized by relatively high levels of species diversity, which was
comparable to that of coastal areas. This result indicated that zooplankton assemblages in the type B holomictic lakes were
closely related to a coastal community. The present study showed that the species diversity of pelagic copepods varies according
to the level of isolation and the local environmental conditions for each marine lake. 相似文献
4.
Environmental influences on regulation of blood plasma/serum components in teleost fishes: a review 总被引:2,自引:0,他引:2
Frank G. Nordlie 《Reviews in Fish Biology and Fisheries》2009,19(4):481-564
Concentrations of both inorganic and organic blood plasma/serum components of teleost fishes were reviewed in seven habitat/life-history
categories. These were: freshwater; inland saline; estuarine and nearshore marine; pelagic and deep-sea; diadromous; southern
cold-water; and northern cold-water. Plasma/serum osmolalities were compared among groups acclimated to/living in fresh and
in salt water. Contributions of inorganic ions and colligative and non-colligative organic molecules were evaluated including
with respect to melting and freezing points, and “antifreeze activity” of plasma/serum in species from cold marine waters.
Possible roles of TMAO in deep-water fishes were reviewed. Discussion also included influences of ambient salinity and temperature
on concentrations of plasma/serum components. Seasonal cycles of blood plasma/serum components were discussed, along with
antifreeze concentrations in other body fluids and tissues of cold-water fishes. Regulatory patterns of plasma/serum osmolalities
were compared among the most euryhaline of teleosts evaluated here. Highest mean values of plasma/serum osmolalities in sea
water were seen in southern cold-water and in pelagic and deep-sea fishes. The southern cold-water group also had the lowest
plasma/serum freezing points among these groups. Comparisons of mean plasma/serum Na+ and Cl− concentrations among fishes from fresh waters did not differ significantly among groups, but species from cold marine waters
showed higher levels than did other groups in marine waters. Plasma/serum osmotic, Na+ and Cl− concentrations of these seven groups of teleosts were compared with those of other fish-like vertebrate groups. Possible
impacts of global warming on regulatory responses of plasma/serum components were discussed. 相似文献
5.
The isolation of obligate halophilic aspergilli from the Dead Sea and the range of salt tolerance of halophilic fungi isolated,
are reported here for the first time. The mycobiota of the Dead Sea isolated in this study, was dominated by Aspergillus and Penicillium species; Cladosporium were found in lesser numbers. All three genera were obtained from the water sample; however, Aspergillus was the only genus obtained from the sediment. There was significant difference in growth of each isolate at different salt
concentrations and intraspecies analysis revealed dissimilarity in response of strains to different salt concentrations in
the growth medium The isolates were euryhaline, with halotolerance up to 20–25% solar salt, Aspergillus and Penicillium species showing a higher level of halotolerance, as compared to that of Cladosporium. Halophilic fungi were found in greater numbers in the sediment sample as compared to that in the water sample. Penicillium and Cladosporium species were exclusively facultative halophiles, while some species of Aspergillus were facultative halophiles. All the obligate halophiles isolated, belonged to the genus Aspergillus and were identified as A. penicillioides and A unguis, the latter being a first record of the species from the Dead Sea. 相似文献
6.
Karin Rengefors Johanna Laybourn‐Parry Ramiro Logares William A. Marshall Gert Hansen 《Journal of phycology》2008,44(3):592-604
The saline lakes of the Vestfold Hills in Antarctica offer a remarkable natural laboratory where the adaptation of planktonic protists to a range of evolving physiochemical conditions can be investigated. This study illustrates how an ancestral marine community has undergone radical simplification leaving a small number of well‐adapted species. Our objective was to investigate the species composition and annual dynamics of dinoflagellate communities in three saline Antarctic lakes. We observed that dinoflagellates occur year‐round despite extremely low PAR during the southern winter, which suggests significant mixotrophic or heterotrophic activity. Only a small number of dominant dinoflagellate species were found in each lake, in contrast to the species‐rich Southern Ocean from which the lake communities are believed to be derived. We verified that the lake species were representatives of the marine polar dinoflagellate community, and not freshwater species. Polarella glacialis Montresor, Procaccini et Stoecker, a bipolar marine species, was for the first time described in a lake habitat and was an important phototrophic component in the higher salinity lakes. In the brackish lakes, we found a new sibling species to the brackish‐water species Scrippsiella hangoei (J. Schiller) J. Larsen, previously observed only in the Baltic Sea. 相似文献
7.
A detailed survey was undertaken of the microbial communities of 16 saline lakes in the Vestfold Hills (Princess Elizabeth
Land, eastern Antarctica), which ranged in salinity from slightly brackish (4–5‰) to hypersaline (maximum: 174‰). Temperatures
at comparable sampling depths in the lakes ranged from −12.2°C to +10.5°C. Ranges in the abundances of bacteria, heterotrophic
nanoflagellates (HNAN) and phototrophic nanoflagellates (PNAN) were 1.40 × 107 l−1–1.58 × 1010 l−1, 4.83 × 104 l−1–1.70 × 107 l−1 and 0–1.02 × 107 l−1, respectively. There was considerable variation across the salinity spectrum, though in the case of bacteria and PNAN significantly
higher concentrations of cells were seen in two of the most saline lakes. The autotrophic ciliate Mesodinium rubrum occurred in all but five of the lakes and was found at salinity levels up to 108‰. Heterotrophic ciliates were generally
scarce. Dinoflagellates, particularly Gonyaulax c.f. tamarensis, Gyrodinium lachryma and Gymnodinium sp., occurred in the majority of the lakes. On the basis of chlorophyll a concentrations, nutrient levels and microplankton concentrations the lakes spanned the spectrum from ultra-oligotrophic to
oligo/mesotrophic. The most saline lakes had much reduced species diversity compared with the less saline environments. Isolation
from the marine environment has led to nutrient depletion, simplification and a truncated trophic structure.
Received: 19 September 1996 / Accepted: 13 January 1997 相似文献
8.
Sorokin DY Tourova TP Abbas B Suhacheva MV Muyzer G 《Extremophiles : life under extreme conditions》2012,16(3):411-417
Four strains of lithotrophic sulfate-reducing bacteria (SRB) have been enriched and isolated from anoxic sediments of hypersaline
chloride–sulfate lakes in the Kulunda Steppe (Altai, Russia) at 2 M NaCl and pH 7.5. According to the 16S rRNA gene sequence
analysis, the isolates were closely related to each other and belonged to the genus Desulfonatronovibrio, which, so far, included only obligately alkaliphilic members found exclusively in soda lakes. The isolates utilized formate,
H2 and pyruvate as electron donors and sulfate, sulfite and thiosulfate as electron acceptors. In contrast to the described
species of the genus Desulfonatronovibrio, the salt lake isolates could only tolerate high pH (up to pH 9.4), while they grow optimally at a neutral pH. They belonged
to the moderate halophiles growing between 0.2 and 2 M NaCl with an optimum at 0.5 M. On the basis of their distinct phenotype
and phylogeny, the described halophilic SRB are proposed to form a novel species within the genus Desulfonatronovibrio, D. halophilus (type strain HTR1T = DSM24312T = UNIQEM U802T). 相似文献
9.
Grazing rates of a calanoid copepod (Paralabidocera antarctica) in a continental Antarctic lake 总被引:1,自引:0,他引:1
The presence of crustaceans in some Antarctic lakes adds a level of complexity to the food webs of these environments. The
grazing pressure of the crustaceans on phytoplankton and other protists, and the role they play in controlling food web structure,
has not yet been examined in any detail. This paper presents the first data on grazing pressure of crustacean zooplankton
in continental Antarctic lakes. In this study the grazing rates of Paralabidocera antarctica in saline Ace Lake, Vestfold Hills, were assessed using a radio-tracer method. Clearance rates ranged from approximately
1 to 8 ml ind.−1 day−1, depending on developmental stage. Due to their high abundance, nauplii exhibited the highest daily carbon ingestion rates.
The population cleared about 3% of the water column per day, accounting for a significant fraction of primary production.
P. antarctica has a considerable impact on the carbon cycle in Ace Lake and, by inference, in the other lakes in which it occurs.
Accepted: 30 October 1999 相似文献
10.
Antarctic lakes are extreme ecosystems with microbially dominated food webs, in which viruses may be important in controlling
community dynamics. A year long investigation of two Antarctic saline lakes (Ace and Pendant Lakes) revealed high concentrations
of virus like particles (VLP) (0.20–1.26 × 108 ml−1), high VLP: bacteria ratios (maximum 70.6) and a seasonal pattern of lysogeny differing from that seen at lower latitudes.
Highest rates of lysogeny (up to 32% in Pendant Lake and 71% in Ace Lake) occurred in winter and spring, with low or no lysogeny
in summer. Rates of virus production (range 0.176–0.823 × 106 viruses ml−1 h−1) were comparable to lower latitude freshwater lakes. In Ace Lake VLP did not correlate with bacterial cell concentration
or bacterial production but correlated positively with primary production, while in Pendant Lake VLP abundance correlated
positively with both bacterial cell numbers and bacterial production but not with primary production. In terms of virus and
bacterial dynamics the two saline Antarctic lakes studied appear distinct from other aquatic ecosystems investigated so far,
in having very high viral to bacterial ratios (VBR) and a very high occurrence of lysogeny in winter. 相似文献
11.
Sepideh Zununi Vahed Haleh Forouhandeh Salar Hassanzadeh Hans-Peter Klenk Mohammad Amin Hejazi Mohammad Saeid Hejazi 《Microbiology》2011,80(6):834-841
Urmia Lake is one of the most permanent hypersaline lakes in the world which is threatened by hypersalinity and serious dryness.
In spite of its importance no paper has been published regarding bacterial community of this lake. Accordingly, the present
study aimed to investigate the halophilic bacteria in the aforementioned lake. In so doing, thirty seven strains were isolated
on six different culture media. The isolated strains were characterized using phenotypic and genotypic methods. Growth of
the strains occurred at 25–35°C, pH 6–9 and 7 to 20% (w/v) NaCl indicating that most of the isolates were moderately halophiles.
Catalase, oxidase and urease activities were found to be positive for the majority of the isolates. Phylogenetic analysis
based on 16S rRNA gene sequences indicated that the isolated bacteria belonged to two major taxa: Gammaproteobacteria (92%, including Salicola [46%], Pseudomonas [13.5%], Marinobacter [11%], Idiomarina [11%], and Halomonas [8%]) and Firmicutes (8%, including Bacillus [5%] and Halobacillus [3%]). In addition, a novel bacterium whose 16S rRNA gene sequence showed almost 98% sequence identity with the taxonomically
troubled DSM 3050T, Halovibrio denitrificans HGD 3T and Halospina denitriflcans HGD 1–3, each, was isolated. 16S rRNA gene similarity levels along with phenotypic characteristics suggest that some of the
isolated strains could be regarded as potential type strain for novel species, on which further studies are recommended. 相似文献
12.
Benthic moss pillars in Antarctic lakes 总被引:2,自引:0,他引:2
Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater
lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter
and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment
and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably
greater than that previously estimated.
Accepted: 11 April 1999 相似文献
13.
Chinese and Mongolian saline lakes: a limnological overview 总被引:8,自引:2,他引:6
W. D. Williams 《Hydrobiologia》1991,210(1-2):39-66
More than half of China's lakes are saline (viz. have salinities > 3 g L−1). Most salt lakes are in northwestern China (Tibet, Qinghai, Sinkiang, Inner Mongolia). Most Mongolian salt lakes are in
the west of that country. Tectonic movements have been of the greatest importance in lake origins, but aeolian activity and
deflation have also played a role. Many salt lakes in Qinghai-Tibet lie at altitudes > 4 000 m.a.s.l.; Aiding Hu (Sinkiang)
lies at −154 m.a.s.l. Again, many lakes are large in area and deep. Small, shallow lakes are also common. Dimictic thermal
patterns prevail in deep lakes, polymictic patterns in shallow ones. The highest salinity recorded is 555 g L−1. The salinity of Qinghai Lake, the largest Chinese salt lake, is 14 g L−1, but mean lake salinity on the northern Tibetan plateau is about an order of magnitude greater. Lop Nor has a salinity of
∼ 5 g L−1. Dominant ions are Na and Cl; Mg, Ca, SO4 and HCO3 + CO3 are important in certain lakes. Most major ions originate by weathering and leaching from rocks. pH values are generally
high (often > 9.0).
There are no bird or fish species confined to salt lakes, though many are associated with lakes of low or moderate salinity.
Artemia occurs widely inland and in coastal salt pans, but is the only major macroinvertebrate of highly saline lakes. In lakes of
only low to moderate salinity, invertebrate communities comprise widespread halotolerant freshwater forms and halophiles,
some regionally endemic. Submerged and emergent macrophytes occur in lakes of low salinity, but phytoplankton species are
more halotolerant. Ctenocladus circinatus, a green alga, is known from a Tibetan salt lake with a salinity of 200 g L−1.
There is a dearth of basic limnological information on Chinese and Mongolian salt lakes. More work in particular is needed
on a variety of geographically widespread lakes to (a) document seasonal physico-chemical events, and (b) compile comprehensive
biological inventories of taxa present. Chinese salt lakes are significant sites for palaeoclimatic research, for conservation
purposes, and for the resolution of several important biological questions (especially of an ecological and biogeographical
sort). They also have important economic values. Unfortunately, the natural existence of many appears to be threatened by
decreased inflows, largely the result of human impact on catchments. 相似文献
14.
Stable Isotope Ratios as a Tool for Assessing Changes in Carbon and Nutrient Sources in Antarctic Terrestrial Ecosystems 总被引:3,自引:0,他引:3
A. H. L. Huiskes H. T. S. Boschker D. Lud T. C. W. Moerdijk-Poortvliet 《Plant Ecology》2006,182(1-2):79-86
Samples of an angiosperm species, nine lichen species and a terrestrial alga, were collected from a variety of Antarctic terrestrial
habitats, and were analysed for C and N stable isotope composition. Collections were made along natural gradients, the marine
gradient, running from the sea coast inland and the moisture gradient, determined by melt water and precipitation runoff,
and running towards the sea coast. Considerable variation in stable isotope ratios was found; δ13C values ranged between −16 and −32‰ and δ15N values between −23 and +23‰ The variation in stable carbon isotope ratios could be attributed in part to species specific
differences, but differences in water availability also played a role, as was shown for the terrestrial alga Prasiola crispa and the lichen species Usnea antarctica. The differences in the isotope ratios of nitrogen could be retraced to the origin of nitrogen: marine or terrestrial. The
nitrogen stable isotope ratios were influenced by both the marine gradient from the sea inland and the melt water and precipitation
flow running in the opposite direction, towards the sea. This was shown for the lichen species Turgidosculum complicatulum and the angiosperm species Deschampsia antarctica. The variation in the C and N stable isotope ratios can be used to determine sources and pathways of N and changes in the
water availability in Antarctic terrestrial ecosystems. Contrary to earlier reports the use of stable N isotope ratios is
possible in this case because of the relative simplicity of the structure of the Antarctic terrestrial ecosystems. 相似文献
15.
The occurrence of the unique autotrophic ciliate Mesodinium rubrum was investigated in a suite of lakes of various salinities situated in the Vestfold Hills oasis, Princess Elizabeth Land (eastern Antarctica). M. rubrum was found to occur in all but the most hypersaline lakes in the survey but was most numerous in the more brackish lakes. Salinity and water column temperature appeared to be the most important factors controlling the occurrence and abundance of this species. Nutrient levels (phosphate and nitrate) did not appear to be important controlling factors, although their influence may have been distorted by the fact that nutrient concentrations were generally higher in the more saline lakes. The widespread occurrence of this species in brackish and saline lakes of the Vestfold Hills provides opportunities to study the ecology and possible physiological and ultrastructural adaptations to living in a high-latitude environment of this ubiquitous and important species in marine microbial food webs. 相似文献
16.
Viruses in the plankton of freshwater and saline Antarctic lakes 总被引:8,自引:1,他引:7
1. Virus‐like particle (VLP) abundances in nine freshwater to saline lakes in the Vestfold Hills, Eastern Antarctica (68° S) were determined in December 1999. In the ultra‐oligotrophic to oligotrophic freshwater lakes, VLP abundances ranged from 1.01 to 3.28 × 106 mL–1 in the top 6 m of the water column. In the saline lakes the range was between 6.76 and 36.5 × 106 mL–1. The lowest value was found in meromictic Ace Lake and the highest value in hypersaline Lake Williams. Virus to bacteria ratios (VBR) were lowest in the freshwater lakes and highest in the saline lakes, with a maximum of 23.4 in the former and 50.3 in the latter. 2. A range of morphologies among VLP was observed, including phages with short (Podoviridae) and long tails, icosahedric viruses of up to 300 nm and star‐like particles of about 80 nm diameter. 3. In these microbially dominated ecosystems there was no correlation between VLP and either bacterial numbers or chlorophyll a. There was a significant correlation between VLP abundances and dissolved organic carbon concentration (r=0.845, P < 0.01). 4. The data suggested that viruses probably attack a spectrum of bacteria and protozoan species. Virus‐like particle numbers in the freshwater lakes were lower than values reported for lower latitude systems. Those in the saline lakes were comparable with abundances reported from other Antarctic lakes, and were higher than most values published for lower latitude lakes and many marine systems. Across the salinity spectrum from freshwater through brackish to hypersaline, VLP concentrations increased roughly in relation to increasing trophy. 5. Given that Antarctic lakes have a plankton almost entirely made up of bacteria and protists, and that VLP abundances are high, it is likely that viruses play a pivotal role in carbon cycling in these extreme ecosystems. 相似文献
17.
Fluctuating hydrochemistry, as a result of extreme hydrological regimes, imposes major physiological constraints on the biota
of ephemeral saline lakes. While the inverse relationship between salinity and zooplankton species richness is well-known
across salinity gradients, few studies have documented closely the response of zooplankton to seasonal changes in salinity.
Weekly sampling during two flood seasons at Sua Pan, an intermittent saline lake in central Botswana demonstrated the importance
of spatial and temporal salinity gradients for crustacean community composition, associated with a decline in species richness,
from 11 to three species. Conductivity ranged between 320 and 125,800 μS cm−1 during seasonal flooding; changing from dominance by
and , Ca2+ and Mg2+, at the beginning of the floods, to NaCl dominated waters as the lake dried out and salinities increased. pH estimates generally
ranged between 8.6 and 10, with maximum values recorded during initial flooding. Crustaceans comprised mainly Branchinella spinosa, Moina belli, Lovenula africana and Limnocythere tudoranceai, all of which occurred across a wide range of salinities, while halotolerant freshwater species (Metadiaptomus transvaalensis, Leptestheria striatochonca and the ostracods Plesiocypridopsis aldabrae, Cypridopsis newtoni and a newly identified Potamocypris species) disappeared above conductivities of 1,500 μS cm−1. A unique crustacean composition in southern Africa was attributed to Sua Pans’ rare chemical composition among southern
African saline lakes; flood waters on Sua Pan contained a higher proportion of Na+ and , and less K+, Mg2+ and than over 80% of records from salt pans elsewhere in southern African. The freshwater species of crustaceans in Sua Pan were
similar to those found in other southern Africa lakes, and these similarities decreased in lakes with higher pH and proportions
of Na, and less SO4 and Mg in their chemical composition. The predominant saline tolerant species on Sua Pan, however, showed a greater similarity
to those in saline lakes in southern and East Africa with higher proportions of and, particularly, Mg2+ in their chemical composition.
Handling editor: J. M. Melack 相似文献
18.
Weathers WW Gerhart KL Hodum PJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):561-572
We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal
metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically
for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98%
of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape
petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with
nestlings of other high-latitude seabirds. Adult lower critical temperature (Tlc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their Tlc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings
attained peak mass. Nestling Tlc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling Tlc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species.
Accepted: 12 July 2000 相似文献
19.
Synopsis The distribution of Sarotherodon mossambicus in south east African estuaries is reviewed. It occurs commonly in closed estuaries and coastal lakes but is absent from open tidal estuaries. When a closed estuary opens to the sea the species usually retreats to the upper reaches. It is euryhaline and eurythermal and can feed on a wide variety of foods but experiments indicate that S. mossambicus avoids areas where current speeds exceed 370 m h–1. It is concluded that the distribution of S. mossambicus in estuarine systems is governed by an interplay of the following factors: salinity stability, water currents, suitable breeding sites, presence of marginal vegetation, marine competitors and marine piscivorous fish. 相似文献
20.
Archaeal microorganisms that grow optimally at Na+ concentrations of 1.7 M, or the equivalent of 10% (w/v) NaCl, and greater are considered to be extreme halophiles. This review
encompasses extremely halophilic archaea and their growth characteristics with respect to the correlation between the extent
of alkaline pH and elevated temperature optima and the extent of salt tolerance. The focus is on poly-extremophiles, i.e.,
taxa growing optimally at a Na+ concentration at or above 1.7 M (approximately 10% w/v NaCl); alkaline pH, at or above 8.5; and elevated temperature optima,
at or above 50°C. So far, only a very few extreme halophiles that are able to grow optimally under alkaline conditions as
well as at elevated temperatures have been isolated. The distribution of extremely halophilic archaea growing optimally at
3.4 M Na+ (approximately 20% w/v NaCl) is bifurcated with respect to pH optima, either they are neutrophilic, with a pHopt of approximately 7, or strongly alkaliphilic, with pHopt at or above 8.5. Amongst these extreme halophiles which have elevated pH optima, only four taxa have an optimum temperature
above 50°C: Haloarcula quadrata (52°C), Haloferax elongans (53°C), Haloferax mediterranei (51°C) and Natronolimnobius
‘aegyptiacus’ (55°C). 相似文献