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1.
Genetic diversity of Nymphon (Arthropoda: Pycnogonida: Nymphonidae) along the Antarctic Peninsula with a focus on Nymphon australe Hodgson 1902 总被引:1,自引:0,他引:1
Sea spiders are conspicuous, and often abundant, members of the Antarctic benthic community. Nymphonidae (Pycnogonida) in
Southern Ocean waters comprise over 240 species which are often difficult to assign due to their intraspecific ‘highly variable’
morphology. In particular, Nymphon australe, the numerically dominant species in Antarctic waters is known to have a high level of phenotypic variation in external morphology
and is also reported to have a circumpolar distribution. Circumpolarity seems contradictory to the pycnogonid’s brooding lifestyle
and presumably limited dispersal. Here we examine the genetic diversity of several Nymphon species collected in the Antarctic Peninsular region. Concomitantly, we assess the genetic structure of N. australe to gain insight into Nymphon dispersal capacity. Cytochrome c oxidase subunit I (COI) and 16S ribosomal gene data suggest a recent common history and/or recent gene-flow of N. australe populations across nearly 800 km of the Antarctic Peninsula. Furthermore, these data support that the Antarctic Peninsula
region may hold two previously unrecognized species of Nymphon.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
Fluoride in Antarctic marine crustaceans 总被引:2,自引:0,他引:2
The concentration of fluoride in the body parts of a range of Antarctic crustaceans from a variety of habits was examined
with the aim of determining whether fluoride concentration is related to lifestyle or phylogenetic grouping. Euphausiids had
the highest overall fluoride concentrations of a range of Antarctic marine crustaceans examined; levels of up to 5477 μg g−1 were found in the exoskeleton of Euphausia crystallorophias. Copepods had the lowest fluoride levels (0.87 μg g−1 whole-body); some amphipods and mysids also exhibited relatively high fluoride levels. There was no apparent relationship
between the lifestyle of the crustaceans and their fluoride level; benthic and pelagic species exhibited both high and low
fluoride levels. Fluoride was concentrated in the exoskeleton, but not evenly distributed through it; the exoskeleton of the
head, carapace and abdomen contained the highest concentrations of fluoride, followed by the feeding basket and pleopods,
and the eyes. The mouthparts of E.␣superba contained almost 13 000 μg F g−1 dry wt. Antarctic krill tail muscle had low levels of fluoride. After long-term (1 to 5 yr) storage in formalin, fluoride
was almost completely lost from whole euphausiids.
Received: 1 April 1998 / Accepted: 29 July 1998 相似文献
3.
In the marine environment, connectivity is influenced by physical oceanography as well as life history and behavioral traits,
which in combination with historical events such as geology, physical oceanography, and climate, determine population structure.
The Antarctic brittle star Ophionotus victoriae develops via a feeding planktonic larval stage, and therefore has potential for long-distance dispersal throughout its Antarctic/subantarctic
range. To evaluate this hypothesis, phylogeography of this ecologically dominant species was elucidated by sequence analysis
of two mtDNA genes from individuals collected throughout the Antarctic Peninsula and from two subantarctic islands. Counter
to expectations of genetic homogeneity, mtDNA data revealed substantial levels of genetic differentiation as well as diversity.
Although there were some genetically homogeneous populations, such as those throughout Bransfield Strait, we found O. victoriae to have significant population structure throughout much of the Antarctic Peninsula, with evidence of potential cryptic speciation
between the western and eastern Antarctic Peninsula. Furthermore, Antarctic Peninsula populations were genetically distinct
from subantarctic island populations. The low levels of connectivity implied for O. victoriae contrast with those found for many other Antarctic benthic taxa, and suggest a complex interplay between oceanography, recent
climate history, and larval ecology. 相似文献
4.
To better understand the feeding and reproductive ecology of euphausiids (krill) in different ocean environments, lipid classes
and individual lipid components of four different species of euphausiids from Northeast Pacific (temperate species) and Southern
Ocean (Antarctic species) were analyzed in animals from multiple life stages and seasons. The dominant krill species in the
Northeast Pacific Euphausia pacifica and Thysanoessa spinifera, were compared to the two major Antarctic species, Euphausia superba and E. crystallorophias. Analysis comprised total lipid and lipid classes together with individual fatty acid and sterol composition in adults, juveniles,
and larvae. Antarctic krill had much higher lipid content than their temperate relatives (10–50 and 5–20% of dry mass for
Antarctic and temperate species, respectively) with significant seasonal variations observed. Phospholipids were the dominant
lipid class in both temperate krill species, while neutral storage lipids (wax esters and triacylglycerols for E. crystallorophias and E. superba, respectively) were the major lipid class in Antarctic krill and accounted for up to 40% of the total lipid content. Important fatty acids, specifically 16:0, 18:1ω9, 20:5ω3, and 22:6ω3, were detected in all four krill species, with minor
differences between species and seasons. Detailed lipid profiles suggest that krill alter their lipid composition with life
stage and season. In particular, larval Antarctic krill appear to utilize alternate food resources (i.e., sea-ice associated
organisms) during austral winter in contrast to juveniles and adults (i.e., seston and copepods). Lipid dynamics in krill
among krill in both systems appear closely linked to their life cycle and environmental conditions including food availability,
and can provide a more complete comparative ecology of euphausiids in these environmentally distinct systems. 相似文献
5.
Antarctic krill, Euphausia superba Dana, a major component in the southern ocean food web, typically occur in aggregations that range from small, discrete swarms
and schools through to layers and superswarms that extend horizontally for several kilometres. A large Longhurst–Hardy plankton
recorder has been used to obtain high-resolution serial samples from within two layers (up to 4 km in length) that were found
near Elephant Island, north of the Antarctic Peninsula. Krill length, sex and maturity stage, net and acoustic estimates of
number density are shown to vary significantly within these large layers. The variation occurring within a single layer is
comparable with that occurring in a set of 38 swarms sampled contemporaneously with the layers. Thus, unlike a krill swarm,
a whole krill layer may account for a substantial amount of the variation in the local krill population, although individual
parts of the layer cannot be considered in this way. The layers play an important role in the ecology of the krill within
the area. Firstly, these large layers may contain a significant proportion of the biomass within an area. Secondly, the structure
of the layers gives some insight into the ways in which krill swarm formation and dispersal may be occurring.
Received: 28 March 1997 / Accepted: 3 December 1997 相似文献
6.
Mesozooplankton community structure in the vicinity of the Prince Edward Islands (PEIs) was investigated during six surveys
conducted in late austral summer (April/May) from 1996 to 1999. Zooplankton samples were collected by oblique tows using a
Bongo net fitted with 300-μm mesh. Surface temperature, average temperature and chlorophyll a were measured in conjunction with each net tow. The positions of the Sub-Antarctic Front (SAF) and the Antarctic Polar Front
(APF), in relation to the islands, were determined by CTD and/or XBT transects to the west of the islands (upstream). Both
fronts were characterized by a high degree of latitudinal variation. Changes in position of the fronts occurred rapidly, the
SAF moving up to ∼120 km in a 2-week period. Consequently, the oceanographic environment in the vicinity of the PEIs was subject
to a high degree of intra- and inter-survey variation. The positions of the SAF and APF appeared to have a significant impact
on phytoplankton biomass in the vicinity of the PEIs, possibly through the alteration of local oceanographic flow dynamics.
Water retention over the island shelf in 1996, associated with location of the SAF far to the north of the PEIs, corresponded
to enhanced chlorophyll-a concentrations (∼1.54 mg m−3). Conversely, when the fronts were close to the islands, as in 1997 and 1999, higher current velocity limited water retention
and chlorophyll-a concentrations in the inter-island region were relatively low (∼0.4 mg m−3). Cluster analyses showed that, in many instances, there was greater similarity among zooplankton communities from different
surveys than among communities within surveys, indicating that short-term variability exceeded inter-annual variability. The
population structure of the copepod Calanus simillimus indicated that there was inter-annual variation in the timing of the biological season. Differences in the population structure
of species, and consequently their contribution to abundance and biomass, may therefore have been an important contributor
to inter-annual variation in community structure. Evidence is provided of a long-term southward shift in the position of the
SAF. It is postulated that this may affect the PEIs by increasing the proportion of allochthonous energy input, because the
PEIs now lie in the path of the front, altering the tropho-dynamics of the island ecosystem. Lower mesozooplankton biomass
associated with warmer sub-Antarctic water may have important negative consequences for higher trophic levels that depend
on mesozooplankton for food.
Received: 10 June 2000 / Accepted: 22 September 2000 相似文献
7.
The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time
these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained
in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the
majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning.
Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential
for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species
studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced
and relatively isolated.
Received: 27 May 1997 / Accepted: 27 November 1997 相似文献
8.
The phylogenetic relationships of the Antarctic krill Euphausia superba, the key species in the Antarctic food web, and other Antarctic and sub-Antarctic cuphausiids have been investigated using the 16S ribosomal mitochondrial gene. The phylogenetic reconstructions indicated that the Antarctic species form a monophyletic clade separated by the non-Antarctic species. The results revealed a large genetic divergence between the Antarctic (E. superba and E. crystallorophias) and sub-Antarctic species (E. vallentini). The time of separation between these species, estimated from the molecular data, is around 20 million years ago, which is comparable with the geological time of the formation of a circum-Antarctic water circulation and the Antarctic Polar Frontal Zone. The euphausiid molecular phylogeny therefore represents evidence for vicariant speciation. 相似文献
9.
V. Siegel 《Marine Biology》1987,96(4):483-495
10.
Although oysters are commercially very important in Brazil, there is still much dispute about the number of Crassostrea species occurring on the Brazilian coast. The dispute is centered around C. brasiliana, considered by some authors to be a junior synonym of C. rhizophorae. In this paper we compared, by allozyme electrophoresis, sympatric and allopatric populations of the two putative species.
Of the 17 loci analysed, five were diagnostic for the two species in sympatry (gene identity = 0.46 to 0.47), clearly demonstrating
that they are distinct biological species. Heterozygosity (h) levels were high for both species (h = 0.24 to 0.28), and no heterozygote deficiencies were observed in any population (local inbreeding, F
IS
= 0.141; P > 0.70). Levels of population structure in C. rhizophorae along 1300 km of coast were very low (population inbreeding, F
ST
= 0.026; P > 0.15), indicating that the planktonic, planktotrophic larvae of these species are capable of long-range dispersal.
Received: 14 January 1999 / Accepted: 8 December 1999 相似文献
11.
K. Reid 《Marine Biology》2001,138(1):57-62
Antarctic krill Euphausia superba has a central role in the ecosystem of the Southern Ocean and knowledge of its growth rate is central to determining the
factors influencing population dynamics. The length of Antarctic krill in the diet of Antarctic fur seals Arctocephalus gazella at South Georgia revealed a consistent increase in size between ca. 42 and ca. 54 mm over the period October–March, indicating
growth rates much higher than predicted by existing models. Geographical variation in growth rate may result in 2-year-old
krill at South Georgia attaining the same size as 3-year-old krill in the Antarctic Peninsula region. The effect of geographical
variation in growth rate on the population structure of krill has important implications for comparing the fate of individual
cohorts over large scales and in the interpretation of krill life-cycles.
Received: 20 May 2000 / Accepted: 11 August 2000 相似文献
12.
Direct-developing intertidal Lasaea spp. occur in the North Atlantic as both continental margin and oceanic island populations. We conducted a molecular phylogenetic
analysis of representative populations in order to test colonization hypotheses for North Atlantic oceanic islands. Thirty
individuals each were collected in 1995 and 1996 from two continental putative source populations (Florida, Iberia) and two
oceanic island populations (Bermuda, Azores). They were sequenced for a 462 nucleotide portion of the mitochondrial large
ribosomal subunit (16S) gene. No amphi-Atlantic genotypes were detected: Bermudan lineages co-clustered exclusively with Floridian
congeners, and Azorean samples formed an exclusive clade with Iberian haplotypes. Our data indicate that geographical proximity
to continental source populations is a better predictor of phylogenetic relationships in North Atlantic Lasaea spp. than present-day oceanic surface circulation patterns. The phylogenetic trees generated are not consistent with colonization
of oceanic islands by indirect-developing ancestral lineages or by truly trans-oceanic rafting events. However, they are consistent
with predicted topologies resulting from limited (≤ 2000 km), long-distance colonization by rafting (against present-day circulation
patterns in the case of the Azores) and from anthropogenic introductions.
Received: 17 December 1998 / Accepted: 7 June 1999 相似文献
13.
Age and growth of Electrona antarctica (Pisces: Myctophidae), the dominant mesopelagic fish of the Southern Ocean 总被引:1,自引:0,他引:1
Numerically and in biomass, the lanternfish Electrona antarctica is the dominant fish in the vast pelagic region of the Southern Ocean bounded on the north by the Antarctic Convergence and
in the south by the Antarctic continental shelf. It is an important krill predator, and in turn is important in the diets
of flighted and swimming seabirds. Further, it is the southernmost and coldest-dwelling representative of the globally distributed
fish family Myctophidae. The present study was undertaken to estimate the species' growth rate and average life span, to incorporate
the information in a basic energy budget, and to compare the growth of E. antarctica with more northerly confamilials. Fishes were aged using primary growth increments that were resolved on sagittal otoliths
using three sequential techniques: thin-section grinding and polishing, etching, and scanning electron microscopy (SEM). Based
on increment width (0.8 to 1.2 μm), continuity, and previous studies on confamilials, the microincrements were assumed to
be deposited on a daily basis. Montages of SEM photomicrographs were constructed for each sagitta to allow the daily rings
to be counted over the entire life span of 31 individuals representing the entire size range of the species. Results suggest
a larval stage of 30 to 47 d and a maximum life span of 3.5 yr, with females growing faster than males in the last 1.5 yr
of life and reaching a larger maximum size. Construction of a simple energy budget using the best information available suggests
that a surplus of energy is available to support the observed growth rates (0.05 to 0.07 mm d−1). The results of the present study contrast markedly with previous estimates of an 8 to 11 yr maximum age for E. antarctica. These results provide important data addressing the ecology and population dynamics of the pelagic Antarctic ecosystem.
E. antarctica is the end-member species in the continuum of vertically migrating myctophids that extend from the equator to the polar circle.
Its growth rate is consonant with that of all other myctophid species examined using primary growth increments to determine
age. The present study, in conjunction with earlier studies, suggests that growth rates of mesopelagic species are far higher
than previously thought.
Received: 12 September 1997 / Accepted: 25 July 1998 相似文献
14.
An allozyme survey, using starch-gel electrophoresis, was carried out on eight populations of the Antarctic nemertean worm
Parborlasia corrugatus (McIntosh, 1876) collected from locations around the South Orkney Islands, Antarctica. These populations were separated by
distances in the order of tens of kilometres. Genetic variation was estimated over 22 enzyme loci for all populations examined,
giving an observed heterozygosity of 0.142. This was much lower than the expected heterozygosity (H
e
= 0.201), and it was found that there was a significant deficiency of het‐erozygotes across four enzyme loci ( p ≤ 0.01). A more detailed examination of this deficiency of heterozygotes was undertaken for the six populations and six variable
enzyme loci for which the most complete data sets existed. A significant deficiency of heterozygotes was found at the enzyme
locus Odh-1 for four of the six populations examined ( p ≤ 0.01). Mean F
is
(0.240) indicated a significant ( p ≤ 0.01) within-population component of the heterozygote deficiency estimated for the six populations sampled, and this was
mainly due to the␣Ap-1, Odh-1 and Pgm-1 loci. The mean F
st
value (0.036) was also significant ( p ≤ 0.01), indicating a degree of genetic differentiation between populations. The observed levels of genetic differentiation
between populations of P. corrugatus and the significant heterozygote deficiencies were unexpected, because this species has been reported to have a long-lived
planktotrophic larva. It is hypothesised that recruitment of P. corrugatus in the South Orkney Islands originates from genetically distinct populations located in the Weddell Sea and to the west of
the Antarctic Peninsula. Shifts in the relative position of the Weddell Sea Front, Weddell–Scotia Confluence and Scotia Front,
relative to the South Orkney Islands, provide a mechanism for variation in the origin of recruits over time.
Received: 24 July 1997 / Accepted: 31 October 1997 相似文献
15.
Genetic analysis of the marine bryozoans Celleporella hyalina and Electra pilosa using the RAPD technique revealed population structuring corresponding to the contrasting modes of larval dispersal. Samples
of C. hyalina exhibited genetic differentiation over distances as small as 10 m, concordant with the limited dispersal predicted by a simulation
model, based on the short pelagic phase of the lecithotrophic larvae and the local hydrography. In contrast, E. pilosa showed high levels of genetic heterogeneity only over much larger spatial scales, commensurate with its production of comparatively
long-lived planktotrophic larvae. The population differentiation observed between samples of E. pilosa, collected from sites 70 km apart, is reconcilable with coastal water currents and frontal systems that restrict the exchange
of water masses between the two sites. Hydrographic conditions and discontinuous distribution of suitable substrata therefore
are seen to constrain gene flow, creating opportunities for local genetic differentiation despite the high dispersal potential
of pelagic larvae.
Received: 9 August 2000 / Accepted: 18 November 2000 相似文献
16.
Samples of the Antarctic octopus Pareledone turqueti were taken from three locations on the Scotia Ridge in the Southern Ocean. The genetic homogeneity of these populations was
investigated using isozyme electrophoresis. Whilst panmixia appeared to be maintained around South Georgia (F
ST = 0) gene flow between this island and Shag Rocks, an island only 150 km away but separated by great depths, was extremely
limited (F
ST = 0.74). These results are examined with respect to the discontinuous distribution of P. turqueti throughout Antarctica. An estimate of effective population size was also calculated (N
e = 3600).
Received: 7 March 1997 / Accepted: 27 March 1997 相似文献
17.
Allozyme variation was used to investigate the genetic structure of the coral reef fishes Stegastes nigricans, Epinephelus merra and Acanthurus triostegus around New Caledonia. Each species was sampled from each of three sites in the ≃1000 km circumference of the lagoon of New
Caledonia. Allelic variation was recorded for each species at 14, 13 and 17 loci, respectively, and heterozygosity diversity
(H
s) was 0.082, 0.065 and 0.116, respectively. Analysis of genetic differentiation between sites produced inconsistent results
between species, with spatial heterogeneity in two species (S. nigricans, F
st
= 0.038; A. triostegus, F
st = 0.049) and homogeneity in one species (E. merra, F
st = 0.000). Hydrological and climatic data from the lagoon suggest that the eastern and western sides of the lagoon are isolated,
since they lie in water masses of different origin. This may explain the genetic differentiation and restricted gene flow
found at a local scale for S. nigricans and A. triostegus. Homogeneity in populations of E. merra is discussed in relation to its low genetic diversity and its reproductive behaviour.
Received: 23 April 1997 / Accepted: 25 September 1997 相似文献
18.
Vitor H. Paiva Pedro Geraldes Iván Ramírez Ana Meirinho Stefan Garthe Jaime A. Ramos 《Marine Biology》2010,157(6):1385-1399
Many breeding seabird species are central-place foragers and constrained to find productive prey patches within their foraging
ranges. We assessed how different populations of a pelagic seabird species, the Cory’s shearwater Calonectris diomedea, breeding in oceanic and neritic conditions, cope with these constraints in the North Atlantic, during both incubation and
chick-rearing periods. We analysed 237 foraging trips to study the movements and oceanographic characteristics of foraging
habitats of seven different populations of Cory’s shearwaters. Generally, oceanic populations exhibited higher foraging effort,
by travelling more time and to more distant areas, and larger home ranges and feeding areas, than the neritic population (i.e.
breeding on an island within the Portuguese continental platform). On their short trips (i.e. ≤4 days), birds from the different
populations fed mostly in shallower waters around the colony. During long trips (i.e. ≥5 days), feeding areas of both oceanic
and neritic populations were characterized by high concentration values of chlorophyll-a, low sea-surface temperature and shallower habitats, with oceanic populations of the Azores exploiting areas north of the
islands over known seamounts and frontal regions. Birds from other oceanic population (Selvagens) also exploited the African
continental shelf system on their long trips. The home ranges of the different populations overlapped widely, but there was
a general spatial segregation in terms of the core feeding areas at the population level. Core feeding areas and areas of
foraging overlap between different populations should be important to inform conservation management measures, such as the
definition of Marine Important Bird Areas for seabirds over the North Atlantic. 相似文献
19.
Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads
to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate
conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan
waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005)
sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there
was significant, geographically related genetic structure (F
ST = 0.0123, P < 10−5). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates
limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management,
which suggests that measures for POP fisheries conservation should be revisited. 相似文献
20.
Effects of contrasting modes of larval development on the genetic structures of populations of three species of prosobranch gastropods 总被引:1,自引:0,他引:1
M. G. Hoskin 《Marine Biology》1997,127(4):647-656
In south-eastern Australia, the prosobranch gastropods Morula marginalba (Blainville), Cominella lineolata (Lamarck) and Bedeva hanleyi (Angas) have similar fine-scale distributions, but appear to possess very different dispersal capabilities due to contrasting
modes of larval development. M.marginalba produce planktonic larvae, whereas C. lineolata and B. hanleyi undergo direct development in benthic egg capsules and emerge as crawling juveniles. To test for possible effects of contrasting
life histories on levels of genetic variation within and among populations, a survey was conducted of allozyme variation at
six polymorphic loci in 8 to 9 local populations of each species. Collections of snails were made between June 1992 and November
1993. Sampling ranges spanned between 162 and 180 km of coast. Regardless of larval type, proportions of single-locus genotypes
in each collection were consistent with the recruitment of offspring which had been generated through random mating. However,
genotypic diversity was lower in those species that undergo direct development. Loci surveyed in C. lineolata and B. hanleyi were polymorphic (i.e. frequency of most common allele <95%) in fewer populations than those examined for M.␣marginalba (P <0.001) and, where polymorphisms occurred, also possessed significantly fewer alleles (P <0.001). Consequently, average levels of expected heterozygosity were greater in populations of M. marginalba than in those of either of the other species (P <0.001). Genetic variation among populations, expressed as the standardised variance in allele frequencies (F
ST
), was inversely related to expected larval dispersal capability. The nine collections of M. marginalba showed little overall differentiation (F
ST
= 0.017; P <0.001), reflecting the ability of planktonic larvae to interconnect local populations, and so limit divergence due to drift
and natural selection. In contrast, there were high levels of allelic heterogeneity among the nine collections of C. lineolata (F
ST
= 0.523; P <0.001) and eight collections of B. hanleyi (F
ST
= 0.140; P <0.001). These data imply that for species which undergo direct development, local populations are effectively closed and
evolve largely independent of one another.
Received: 3 May 1996 / Accepted: 12 July 1996 相似文献