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1.
A group of killer whales was sighted in open leads well inside Antarctic sea ice during August 1995. This was the first winter
sighting of killer whales in Antarctic waters since 1955, and contradicts the view that all killer whales migrate north prior
to the winter. A small calf was observed, providing the first evidence of a cetacean species breeding in Antarctic waters.
Several potential prey species were also present. The sighting highlights the importance of lead and polynya systems to marine
mammals, which probably use them to disperse within the winter sea-ice zone.
Received: 23 April 1996 / Accepted: 25 August 1996 相似文献
2.
A new species of Oweniidae from the Ross Sea (Antarctica) is described and compared with the remaining species of the genus
Myriochele from the Antarctic seas. The authors also discuss the difficulty of detecting the shape of uncini (considered as an important
diagnostic character) by optical microscopy; they propose a key to Antarctic Oweniidae based on characters easier to observe
than uncini.
Received: 14 October 1997 / Accepted: 16 December 1997 相似文献
3.
Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18
were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of
Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine,
where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were
found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of
the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to
have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final
host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic
fish species provides important insights into the different habitat use and trophic relationship of their fish hosts.
Received: 11 September 1997 / Accepted: 12 January 1998 相似文献
4.
The present paper describes latitudinal and vertical changes in the composition, abundance and diversity of copepods in the
Indian sector of the Antarctic Ocean, during the end of austral summer along a transect on 66°30′E between 43 and 62°S, within
three layers (600–0, 200–0, 100–0 m). Highest copepod densities were noted in the central part of the transect, between the
Antarctic Divergence and the Antarctic Convergence, with a maximum in the Antarctic Divergence zone, particularly in the upper
levels of the water column. A total number of 80 copepod species were identified over the entire survey area. The south end
and the central part of the transect comprised a small number of species. North of the Antarctic Convergence, this number
increased markedly with the progressive disappearence of those species characteristic of Antarctic waters and their replacement
by temperate and subtropical species. Generally, small copepods, particularly Oithona similis, Oithona frigida and Ctenocalanus citer, dominated in numbers in both Antarctic and sub-Antarctic areas. The contribution of large species to total copepod numbers
was much lower, with Calanus simillimus in the central part of the transect, Pleuromamma borealis in the subtropical zone and Calanus propinquus in the southern part. Correspondence analysis showed a marked latitudinal gradient in population structure with four groups
of samples and species corresponding to four latitudinal zones. Community structure (species richness, relative dominance
index, evenness, Shannon species diversity index) and species abundance patterns (as rank-frequency diagrams) suggested that
the maturity and species richness increased gradually from south to north. A low diversity index and evenness were observed
in the area of the Antarctic Divergence, whereas the convergence zone showed high diversity and evenness. Conversely, the
frontal zone showed high diversity and evenness. Distribution appeared unrelated to chlorophyll concentrations and on the
large scale was related to the hydrologic characteristics.
Received: 8 May 1996 / Accepted: 27 August 1996 相似文献
5.
Christensenia gen. nov., C. blocki sp. nov., is described from Signy Island, South Orkney Islands, maritime Antarctic. The new species is identical with specimens
that Stephenson (1932) determined as Marionina georgiana (Michaelsen, 1888), but differs from the type material of M. georgiana. The species M. georgiana (Michaelsen, 1888) is also placed in the new genus Christensenia, the main characteristics of which are: possession of sigmoid setae, and the presence of large numbers of small, hyaline,
stick-like, anucleate lymphocytes. No other types of lymphocyte are observed. Oesophageal appendages and intestinal diverticulae
are absent. Dorsal vessel originates in the clitellar region; blood is colourless. The anteseptal part of the nephridium consists
of the funnel and a few canals, with the efferent duct arising postero-ventrally. Spermathecae are without diverticulae, entally
connecting with the oesophagus. The known distribution of the genus is currently limited to terrestrial habitats in the sub-
and maritime Antarctic.
Received: 24 June 1996 / Accepted: 20 October 1996 相似文献
6.
7.
The diet of the Antarctic fur seal Arctocephalus gazella at Harmony Point, Nelson Island, South Shetland Islands 总被引:1,自引:0,他引:1
The diet of non-breeding male Antarctic fur seals (Arctocephalus gazella) was investigated at Harmony Point, Nelson Island, South Shetland Islands, by the analysis of 18 and 33 scats collected during
February 1996 and 1997 respectively. Overall, fish were the most frequent prey (74.5%) and predominated by mass (54.4%), whereas
krill predominated by number (94.2%). This coincides well with the pattern observed in 1997, but in 1996 krill was the most
important prey by number and mass (50.2%). The importance of the remaining taxa represented in the samples (octopods, hyperiids
and bivalves) was negligible. Among fish, myctophids represented 85.2% of the fish mass, with Gymnoscopelus nicholsi and Electrona antarctica being the main prey. These two species predominated in 1997, whereas the channichthyid Cryodraco antarcticus and the nototheniid Gobionotothen gibberifrons were dominant in 1996. The importance of the myctophids as prey of the Antarctic fur seal is discussed.
Received: 7 October 1997 / Accepted: 24 May 1998 相似文献
8.
Twenty-two stations in the intertidal and shallow sublittoral of Bjornoya (74 °N, 19 °E) were studied in August 1994 revealing
a large and diverse standing crop of macro-algae (16 species) and littoral macrofauna (at least 17 species). In most places
the biomass of littoral macroorganisms exceeded 100 g ww/m2. In the shallow sublittoral, between 2 and 20 m, 45 animal taxa and 23 algae species were collected. Littoral coarse sand
meiofauna was dominated by Turbellaria, while, on algae, Halacaridae and Harpacticoida predominated. Meiofauna densities ranged
from 0 to 169 ind./10 cm2 and biomass from 0 to 0.4 g dw/m2. The abundance of littoral species and their zoogeographic origin resemble that of Spitsbergen more than that of the northern
Scandinavian coast, although both are of equal distance from Bjornoya. The first record of the boreal bivalve Mytilus edulis from the island is presented. Another striking feature was the presence of the arctic amphipod Gammarus setosus and the absence of its boreal sibling species G.oceanicus.
Received: 19 March 1996 / Accepted: 1 December 1996 相似文献
9.
The formation of resting spores in diatoms is a common phenomenon in neritic environments. Here we report on resting spores
of the genus Chaetoceros associated with a layer of increased chlorophyll fluorescence, at a depth of more than 200 m, north of Brabant Island and
in Wilhelmina Bay, southeast coast of the Gerlache Strait (64°41.0′S, 62°0.5′W). Six species of Chaetoceros were identified by the morphology and size of the resting spores. Given that Chaetoceros spp., both in vegetative cells and as resting spores, are commonly found in Antarctic coastal surface waters, their location
at depth could represent the pelagic “waiting” or “seeding” populations mentioned for other environments.
Received: 25 November 1996 / Accepted: 16 November 1997 相似文献
10.
Parasite communities are the product of acquisitions and losses of parasite species during the evolutionary history of their
host. When comparing the parasite communities of different host species to assess the role of ecological variables as determinants
of parasite species richness, a correction must be made for the possible phylogenetic inheritance of parasites from ancestral
hosts independent of host ecology. We performed a comparative analysis of the metazoan ectoparasite communities on the heads
and gills of 111 species of marine fish. The influences of host body size, host schooling behaviour and water temperature
were tested after controlling for both sampling and phylogenetic effects. Overall, water temperature correlated positively
with both parasite species richness and abundance, whereas fish size only correlated with parasite abundance. The correlation
across all fish species between water temperature and parasite species richness was dependent on an outlier point. The results,
however, generally held when fish from different biogeographical areas (Pacific and Atlantic) were analysed separately. In
all analyses, parasite species richness always correlated strongly with parasite abundance. There was no evidence that schooling
fish taxa harboured richer or more abundant ectoparasite communities than their non-schooling sister taxa, possibly because
of the small number of contrasts available for that test. Overall, whereas both water temperature and host size affect the
number of parasite individuals that can be harboured by a fish, only temperature appears important as a determinant of ectoparasite
community richness.
Received: 30 May 1996 / Accepted: 23 October 1996 相似文献
11.
Two species of the genus Oswaldella Stechow, 1919 new to science (Oswaldella crassa sp. nov. and O.␣curiosa sp. nov.) were studied. Both species are described and figured; their systematic position amongst the remaining species of
the genus is discussed. The material originates from the Bransfield Strait area (Antarctica) and was collected during the
United States Antarctic Research Program with R.V. Eltanin. A comparative table listing the main features of the known species of Oswaldella is presented. Finally, a general survey of geographical and bathymetrical distribution of the known species of Oswaldella is given.
Received: 8 October 1997 / Accepted: 2 February 1998 相似文献
12.
An in situ transmission electron microscopic study of biomass samples concentrated from oligotrophic lake water revealed
a variety of virus-infected microbial cells and many free viruses and virus-like particles. The most abundant group of microorganisms
in screened and filtered water-column samples were 2 μm or less in diameter, and included representatives of several oligotrophic
genera, Prosthecomicrobium, Ancyclobacter, Caulobacter and Hyphomicrobium. Among the prokaryotic host cells, which included both heterotrophs and autotrophs, on the basis of electron microscope observations,
approximately 17% were infected with bacteriophage or bore adherent phage particles on their surfaces. Several bacterial morphotypes
were observed among the prokaryotic hosts. Water samples passed through a 20-μm Nitex screen allowed us to concentrate and
examine the larger host cells as well, including several species of single-celled algae and two amoeba species. The infected
algal cells included those Chlorella-like in appearance, photosynthetic flagellates and others that could not be positively identified. About one-third of the
eukaryotic cells were infected by viruses that were larger (150–200 nm) and structurally more complex than bacteriophages
(50–60 nm). None of the viruses have been isolated, but when 0.2 μm filtrate from a biomass sample was spotted onto lawns
of four representative heterotrophs and a Chlorella, the clearing observed was taken as evidence of lysis. Cyanobacterial lawns showed no plaques. Thin sections of two amoeba
showed food vacuoles containing what appeared to be virus particles of a type seen in certain prokaryotic and eukaryotic cells
in the biomass.
Received: 26 January 1996 / Received revision: 10 July 1996 / Accepted: 5 August 1996 相似文献
13.
The bivalve Lissarca notorcadensis is one of the most abundant species in Antarctic waters and has colonised the entire Antarctic shelf and Scotia Sea Islands.
Its brooding reproduction, low dispersal capabilities and epizoic lifestyle predict limited gene flow between geographically
isolated populations. Relationships between specimens from seven regions in the Southern Ocean and outgroups were assessed
with nuclear 28S rDNA and mitochondrial cytochrome oxidase subunit I (COI) genes. The 28S dataset indicate that while Lissarca appears to be a monophyletic genus, there is polyphyly between the Limopsidae and Philobryidae. Thirteen CO1 haplotypes were
found, mostly unique to the sample regions, and two distinct lineages were distinguished. Specimens from the Weddell and Ross
Sea form one lineage while individuals from the banks and islands of the Scotia Sea form the other. Within each lineage, further
vicariance was observed forming six regionally isolated groups. Our results provide initial evidence for reproductively isolated
populations of L. notorcadensis. The islands of the Scotia Sea appear to act as centres of speciation in the Southern Ocean. 相似文献
14.
The diet of Cape petrel Daption capense was investigated at Laurie Island, South Orkney Islands (60°46′S, 44°42′W), Antarctica, in the period January–February 1996. Stomach contents of adults and regurgitate of chicks were sampled during
the post-hatching period. The analysis showed that during the whole sampling period Antarctic krill and fish represented the
predominant preys in terms of frequency of occurrence, forming nearly 35.8% and 64% by mass, respectively. The species Electrona antarctica was the most frequent fish prey. Amphipods were present in lower numbers and cephalopods were detected in the diet, but in
a very small proportion. Diet composition in terms of frequency of occurrence, mass and number is compared with results of
previous studies.
Received: 27 September 1996 / Accepted: 22 February 1997 相似文献
15.
S. Gollasch 《Polar Biology》1997,18(3):223-226
Ostracod samples were taken from coastal waters of the South Shetland Islands (King George and Elephant) northeast of the
Antarctic Peninsula. The population structure of the planktonic ostracods in the upper 200-m water column is described. In
total 77 samples were taken quantitatively by RMT-1 hauls predominantly containing Alacia hettacra, A. belgicae and Metaconchoecia isocheira. The dominance of A2, A1 and adult stages supports Kock's conclusion of an upward-directed ontogenetic migration.
Received: 19 December 1996 / Accepted: 24 March 1997 相似文献
16.
Electric membrane properties and motor behaviour of two Antarctic and two middle-latitude species of Euplotes were compared. Membrane potential fluctuations and whole-cell currents were measured using the whole cell clamp. The electrical
properties of both of the Antarctic species between themselves and of both of the middle-latitude species are nearly identical.
Furthermore, after warming up to 22°C, the Antarctic species grown at 4°C show the same pattern of spontaneous potential fluctuations,
induced potential oscillations and membrane currents as the middle-latitude species grown and measured at 22°C. After cooling
down to 4°C, the middle-latitude species grown at 22°C show the same electrical properties as the Antarctic species grown
and measured at 4°C. The congruence of the temperature-dependent electrical properties in Euplotes species from completely different habitats is presumably based on a universal mechanism of temperature dependence of ionic
conductances, indicating the close physiological relationship among the species.
Received: 29 October 1997 / Accepted: 20 April 1998 相似文献
17.
Stable isotopes prove shell growth bands in the Antarctic bivalve Laternula elliptica to be formed annually 总被引:1,自引:0,他引:1
Growth marks in calcareous shells or skeleton parts of benthic invertebrates are often assumed to be formed annually and
hence are used for ageing purposes. For some Antarctic species this assumption has been validated by tagging experiments or
direct monitoring of growth throughout the year. Here we use the record of stable isotope ratios (δ18O and δ13C) deposited in shell carbonate of Laternula elliptica from King George Island to demonstrate that shell growth bands are formed annually in this species.
Received: 16 July 1995 / Accepted: 27 October 1996 相似文献
18.
M. E. Forster W. Davison M. Axelsson L. Sundin C. E. Franklin S. Gieseg 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):345-352
Two species of Antarctic fish were stressed by moving them from seawater at −1 °C to seawater at 10 °C and holding them for
a period of 10 min. The active cryopelagic species Pagothenia borchgrevinki maintained heart rate while in the benthic species Trematomus bernacchii there was an increase in heart rate. Blood pressure did not change in either species. Both species released catecholamines
into the circulation as a consequence of the stress. P. borchgrevinki released the greater amounts, having mean plasma concentrations of 177 ± 54 nmol · l−1 noradrenaline and 263 ± 131 nmol · l−1 adrenaline at 10 min. Plasma noradrenaline concentrations rose to 47 ± 14 nmol · l−1 and adrenaline to 73 ± 28 nmol · l−1 in T. bernacchii. Blood from P. borchgrevinki was tonometered in the presence of isoprenaline. A fall in extracellular pH suggests the presence of a Na+/H+ antiporter on the red cell membrane, the first demonstration of this in an Antarctic fish. Treatment with the β-adrenergic
antagonist drug sotalol inhibited swelling of red blood cells taken from temperature-stressed P. borchgrevinki, suggesting that the antiporter responds to endogenous catecholamines.
Accepted: 22 January 1998 相似文献
19.
S. Víllora-Moreno 《Polar Biology》1998,19(5):336-341
A new species of marine tardigrade is described coming from the muddy sediment of the Antarctic deep sea. Angursa antarctica sp. nov. is characterized by the presence of balloon-shaped primary clavae, long lateral cirri, long cephalic cirri, spines
on legs I, hemispherical capsule-shaped papillae on legs IV, and short external peduncles. Geographical distribution of the
genus Angursa extends to Antarctic waters, suggesting a cosmopolitan distribution for this bathyal and abyssal genus. A table comparing
the main differentiating characteristics of the species of Angursa is presented.
Received: 25 July 1997 / Accepted: 9 November 1997 相似文献
20.
A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal
structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal
roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging
to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14
g –
1soil in A. farnesiana and from 60% – 73% and 5 – 15 g –
1 soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the
Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata,
G. pustulatum, G. fasciculatum,
G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were
negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along
with soil moisture negatively influenced root colonization.
Received: 16 May 1995 / Accepted: 7 February 1996 相似文献