共查询到20条相似文献,搜索用时 311 毫秒
1.
The genetic population structure of the precominant zooplankter, the copepod Calanus finmarchicus (Gunnerus), was examined to determine whether genetically distinct populations exist in the Gulf of Maine. C. finmarchicus was sampled in three regions of the Gulf of Maine (Great South Channel, spring 1989; northern Gulf of Maine, winter 1990; Great South Channel and Georges Bank, spring 1990). Copepods from seven locations in the Great South Channel, five in the northern Gulf of Maine and four on or near Georges Bank were assayed for allozyme variation and mitochondrial DNA variation of amplified 16S rRNA and cytochrome b genes. Restriction fragment length polymorphism (RFLP) analyses of both mitochondrial DNA genes revealed no variation among any of the individuals assayed. Analysis of five polymorphic allozyme loci revealed that genetic variation among the three geographic regions was low, and genetic identities were high between all locations (I>0.97). Most of the genetic variation was among locations regardless of region. Chi-square tests were used to examine genetic similarity between specific pairs of locations within and between regions. In the northern Gulf of Maine, genetic homogeneity occurred over larger spatial scales (hundreds of km) than in either the Great South Channel or Georges Bank (tens of km). Only copepods from the Bay of Fundy and Nova Scotian Shelf locations were genetically distinct from Wilkinson Basin copepods at two loci. Copepod populations from the northern locations may have been partially isolated or they may represent immigrant populations (e.g., from the Gulf of St. Lawrence). Several pairs of locations were genetically distinct at one or more loci in the two southern regions. Differences between locations in these regions may represent distinct populations advected into the areas at different times or from different sources (e.g., genetic variation may represent a mixture of genetically distinct northern and southern copepod populations). These results suggest extensive gene flow among populations of C. finmarchicus in the Gulf of Maine with some evidence of genetic population subdivision near the Gulf's northeastern and southern boundaries. 相似文献
2.
The pelagic copepod Calanus pacificus ranges nearly continuously across temperate-boreal regions of the North Pacific Ocean and is currently divided into three
subspecies—C. pacificus oceanicus, C. pacificus californicus, C. pacificus pacificus—based on subtle morphological differences and geographic location. The relation between geography and genetic differentiation
was examined for 398 C. pacificus individuals sampled from six widely distributed locations across the North Pacific, including an open ocean site and coastal
sites on both sides of the North Pacific basin. For each individual copepod, the DNA sequence was determined for a 421-bp
region of the mitochondrial coxI gene (mtCOI). A total of sixty-three different mtCOI sequences, or haplotypes, were detected,
with a sequence divergence between haplotypes of 0.2–3.1%. The number and distribution of haplotypes varied with sampling
location; 12 haplotypes were distributed across multiple sampling locations, and 51 occurred at only one location. Five genetically
distinct populations were detected based on F
ST values. Haplotype minimum spanning networks, nucleotide divergence and F
ST values indicated that individuals from coastal sites in the North Pacific Ocean were more closely related to each other than
to individuals from the open ocean site at Station P. These results provide genetic support for the designation of two subspecies—a
coastal subspecies that consists of what is currently referred to as C. p. pacificus and C. p. californicus and an open ocean subspecies C. p. oceanicus. This work also indicates that planktonic copepods with potentially high dispersal capacity can develop genetically structured
populations in the absence of obvious geographic barriers between proximate locales within an ocean basin. 相似文献
3.
The pelagic copepod Calanus pacificus ranges nearly continuously across temperate-boreal regions of the North Pacific Ocean and is currently divided into three
subspecies—C. pacificus oceanicus, C. pacificus californicus, C. pacificus pacificus—based on subtle morphological differences and geographic location. The relation between geography and genetic differentiation
was examined for 398 C. pacificus individuals sampled from six widely distributed locations across the North Pacific, including an open ocean site and coastal
sites on both sides of the North Pacific basin. For each individual copepod, the DNA sequence was determined for a 421-bp
region of the mitochondrial coxI gene (mtCOI). A total of sixty-three different mtCOI sequences, or haplotypes, were detected,
with a sequence divergence between haplotypes of 0.2–3.1%. The number and distribution of haplotypes varied with sampling
location; 12 haplotypes were distributed across multiple sampling locations, and 51 occurred at only one location. Five genetically
distinct populations were detected based on F
ST values. Haplotype minimum spanning networks, nucleotide divergence and F
ST values indicated that individuals from coastal sites in the North Pacific Ocean were more closely related to each other than
to individuals from the open ocean site at Station P. These results provide genetic support for the designation of two subspecies—a
coastal subspecies that consists of what is currently referred to as C. p. pacificus and C. p. californicus and an open ocean subspecies C. p. oceanicus. This work also indicates that planktonic copepods with potentially high dispersal capacity can develop genetically structured
populations in the absence of obvious geographic barriers between proximate locales within an ocean basin. 相似文献
4.
Jeffrey N. Schinske Giacomo Bernardi David K. Jacobs Eric J. Routman 《Marine Biology》2010,157(1):123-134
We compared morphology and sequenced nuclear and mitochondrial genes from 11 populations of a previously genetically unstudied
“Baja California disjunct” species, the diamond turbot (Hypsopsetta guttulata). This species exhibits very limited adult movement and restriction to soft-bottom habitats but has a moderately long pelagic
larval duration. Therefore, if pelagic larval duration is correlated with gene flow between Gulf of California and Pacific
populations, we expect a reduced level of genetic and morphological differentiation. However, if adult habitat and ecology
have more effect on gene flow, we expect the populations in the two bodies of water to be more highly differentiated. We used
logistic regression to compare morphological features and phylogenetic and population genetic analyses to compare nucleotide
sequence data. Gulf of California H. guttulata are different from Pacific populations in morphology and both mitochondrial and nuclear gene sequences. MtDNA shows reciprocal
monophyly, and nuclear sequences from the Gulf of California formed a monophyletic group. Population genetic analyses also
suggest further population subdivision within the Pacific and within the Gulf of California. We argue that adult ecology has
a significant effect on migration rates among populations in the Pacific Ocean and the Gulf of California. 相似文献
5.
The genetic structure of Patagonian toothfish populations in the Atlantic and western Indian Ocean Sectors of the Southern Ocean (SO) were analysed using partial sequences of the mitochondrial 12S rRNA gene and seven microsatellite loci. Both haplotype frequency data (F
ST>0.906, P<0.01) and microsatellite genotype frequency data (F
ST=0.0141–0.0338, P<0.05) indicated that populations of toothfish from around the Falkland Islands were genetically distinct from those at South Georgia (eastern Atlantic Sector SO), around Bouvet Island (western Atlantic Sector SO) and the Ob Seamount (western Indian Ocean Sector of the SO). Genetic differentiation between these populations is thought to result from hydrographic isolation, as the sites are separated by two, full-depth, ocean-fronts and topographic isolation, as samples are separated by deep water. The South Georgia, Bouvet and Ob Seamount samples were characterised by an identical haplotype. However, microsatellite genotype frequencies showed genetic differentiation between South Georgia samples and those obtained from around Bouvet Island and nearby seamounts (F
ST=0.0037, P<0.05). These areas are separated by large geographic distance and water in excess of 3,000 m deep, below the distributional range of toothfish (<2,200 m). No significant genetic differentiation was detected between samples around Bouvet Island and the Ob Seamount although comparisons may have been influenced by low sample size. These localities are linked by topographic features, including both ridges and seamounts, that may act as oceanic “stepping stones” for migration between these populations. As for other species of deep-sea fish, Patagonian toothfish populations are genetically structured at the regional and sub-regional scales. 相似文献
6.
To determine the genetic population structure of blue crabs (Callinectes sapidus Rathbun), electrophoretic allozyme analysis was performed on 750 individuals collected from 16 nearshore locations ranging from New York to Texas, USA. Twenty enzymes and non-enzymatic proteins coded by 31 presumptive loci were examined. Twenty-two loci were either monomorphic or polymorphic at less than theP
95 level; alleles for these polymorphic loci were geographically dispersed. Allele frequencies for three of the remaining polymorphic loci were homogeneous over all populations, as were levels of polymorphism and heterozygosity. Phenograms generated by the UPGMA (unweighted pair-group method using arithmetic averages) and distance Wagner methods exhibited no geographic pattern in the clustering of populations. Estimates ofN
em (effective number of migrants per generation between populations) indicated substantial gene flow, with aalues sufficiently high to infer panmixia between all blue crab populations from New York to Texas. However, despite this high level of gene flow, two striking patterns of geographic differentiation occurred: genetic patchiness and clinal variation. Allele frequencies atEST-2, GP-1, IDHP-2, DPEP-1, DPEP-2, andTPEP exhibited genetic patchiness on local and range-wide geographic scales, and allele frequencies atEST-2 varied temporally. Genetic patchiness in blue crabs is likely to be the result of the pre-settlement formation and subsequent settlement of genetically heterogeneous patches of larvae; allele frequencies of those larval patches may then be further modified through ontogeny by localized selection. In the Atlantic Ocean, a regional latitudinal cline ofEST-2 allele frequencies was superimposed on the range-wide genetic patchiness exhibited by that locus. This pattern against a background of high gene flow is highly likely to be maintained by selection. In estuaries along the Atlantic Ocean coast, a combination of low adult long-distance migration and a high retention rate of locally spawned larvae could serve to segregate populations and allow for the development of the geographic cline inEST-2. The Gulf of Mexico showed no apparent cline, perhaps due to long-distance migration of females in some regions of the Gulf, or to masking by genetic patchiness. These results emphasize the importance of both ecological and evolutionary time scales and structuring mechanisms in determining genetic population structure. 相似文献
7.
White shrimp (Litopenaeus
vannamei) population genetic structure from the eastern Pacific was determined by restriction fragment length polymorphism analysis
of the mitochondrial DNA control region. Four localities were surveyed with four endonucleases (Alu I, Taq I, Spe I, Ssp I) yielding 48 composite haplotypes. White shrimp showed high average within-locality haplotype (0.823) and nucleotide (5.41%)
diversities and also high average nucleotide divergence between all pairs of localities (0.73%). A mismatch analysis of pairwise
differences between haplotypes indicated that white shrimp does not fit the sudden population expansion model. An analysis
of molecular variance showed significant geographic variation in the frequencies of haplotypes (ΦST=0.1382, P<0.0001). Population differentiation may be maintained by a combination of physical, oceanographic, and biological factors
acting as barriers to gene flow among localities. Because of its high polymorphism, the control region might be useful as
a genetic marker for monitoring genetic diversity in aquaculture stocks. 相似文献
8.
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida,
were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment
of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite
allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular
variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites
and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and
northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida
Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant
for both microsatellites (Φ
CT = 0.016, P = 0.009) and mtDNA (Φ
CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic
heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly
less (P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly
less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective
population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability
between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality
of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups
have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood
analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups,
with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and
the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic
events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity
among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically
distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf. 相似文献
9.
To investigate feeding variation between populations of an apex oceanic predator, stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) have been compared in skin of female and immature male sperm whales (Physeter macrocephalus) from the northern Gulf of Mexico (GoM) and the Gulf of California (GC). Whale sexes were determined genetically. The δ13C and δ15N values from squid muscle were used from the GC, and from inshore and offshore sites in the GoM. We documented contrastingly
lower δ13C and δ15N from whales and squid of the GoM compared with those from the GC. While this difference may be associated with variation
in trophic position, geographic variation in biochemical cycling influenced significantly the contrasting isotope values between
gulfs. Within the northern GoM, the highly distinct δ15N values of neritic squid versus mesopelagic squid provide further evidence of habitat specificity in δ15N. 相似文献
10.
E. García-Machado A. Robainas G. Espinosa M. Oliva J. Páez N. Verdecia M. Monnerot 《Marine Biology》2001,138(4):701-707
We investigated the genetic diversity among populations of the shrimp Farfantepenaeus notialis, the most abundant penaeid species around Cuba. A total of 25 allozyme loci were analyzed in samples of shrimps from seven
localities at the south central platform of the island (Ana María Gulf). Samples from three of these localities and from Batabanó
Gulf and Guacanayabo Gulf at the south west and south east platforms of the island, respectively, were also characterized
at the mtDNA level through sequence variation of a 2027 bp segment including part of the COI and COIII genes. Of the 25 allozyme
loci studied 9 were polymorphic: Akp2, Akp3, AmyB, Est3, Gdh, GP7, and Per1, 2 and 3. In contrast to mtDNA, the pattern of allozyme variation among localities revealed strong population structuring
at Ana María Gulf, with significant F
st in all pairwise comparisons. The magnitude of F
st estimates as well as the grouping pattern obtained by a UPGMA analysis based on a distance matrix indicated that the level
of differentiation was concordant with the geographical position of the localities and the hydrographic regime. Homogeneity
of mtDNA suggested that differentiation of allozyme loci might be due to more recent events rather than historical isolation
of the sampled populations. Ana María and Guacanayabo Gulf populations were differentiated by mtDNA from Batabanó Gulf, at
the southwestern end of the island. The analysis showed three restriction site differences among them, suggesting genetic
isolation of the two regions. The present results also suggest that an artificial introduction of larvae from Tunas de Zaza
into Batabanó Gulf, in an effort to repopulate this fishing region, may have been ineffective.
Received: 13 December 1999 / Accepted: 2 October 2000 相似文献
11.
In a previous study on the kuruma shrimp Penaeus japonicus from the South China Sea, we detected high genetic divergence between two morphologically similar varieties (I and II) with
distinct color banding patterns on the carapace, indicating the occurrence of cryptic species. In the present study, we clarify
the geographical distribution of the two varieties in the western Pacific by investigating the genetic differentiation of
the shrimp from ten localities. Two Mediterranean populations are also included for comparison. Based on the mitochondrial
DNA sequence data, the shrimps are separated into two distinct clades representing the two varieties. Variety I comprises
populations from Japan and China (including Taiwan), while variety II consists of populations from Southeast Asia (Vietnam,
Singapore and the Philippines), Australia and the Mediterranean. Population differentiation is evident in variety II, as supported
by restriction profiles of two mitochondrial markers and analysis of two microsatellite loci. The Australian population is
genetically diverged from the others, whereas the Southeast Asian and Mediterranean populations show a close genetic relationship.
Variety I does not occur in these three localities, while a small proportion of variety II is found along the northern coast
of the South China Sea and Taiwan, which constitute the sympatric zone of the two varieties. The present study reveals high
genetic diversity of P. japonicus. Further studies on the genetic structure of this species complex, particularly the populations in the Indian Ocean and Mediterranean,
are needed not only to understand the evolutionary history of the shrimp, but also to improve the knowledge-based fishery
management and aquaculture development programs of this important biological resource. 相似文献
12.
Allelic variation at eight nuclear-encoded microsatellites was assayed among 967 red drum (Sciaenops ocellatus) sampled from four consecutive cohorts at seven geographic localities (=28 samples total) in the northern Gulf of Mexico (Gulf). Number of alleles per microsatellite ranged from 6 to 21; average direct-count heterozygosity values per sample (-SE) ranged from 0.560ǂ.018 to 0.903ǂ.009. Tests of Hardy-Weinberg equilibrium revealed significant departures from expected genotype proportions at one microsatellite, which was omitted from further analysis. Tests of genotypic equilibrium indicated that genotypes between pairs of microsatellites were randomly associated. Homogeneity tests of allele distributions across cohorts within localities were non-significant following correction for multiple tests executed simultaneously, and results from molecular analysis of variance indicated that the genetic variance component attributable to variation among cohorts did not differ significantly from zero. Homogeneity tests of allele distributions among localities (cohorts pooled) revealed significant differences both before and after correction for multiple tests. Neighbor-joining clustering of a pairwise matrix of values (an unbiased estimator of FST), spatial autocorrelations, and regression analysis revealed a pattern of isolation by distance, where genetic divergence among geographic samples increases with geographic distance between sample localities. The pattern and degree of temporal and spatial divergence in the nuclear-encoded microsatellites paralleled almost exactly those of mitochondrial (mt) DNA, as determined in a prior study. Stability of both microsatellite and mtDNA allele distributions within localities indicates that the small but significant genetic divergence among geographic samples represents true signal and that overlapping populations of red drum in the northern Gulf may be influenced by independent population dynamics. The degree of genetic divergence in microsatellites and mtDNA is virtually identical, indicating that genetic effective size of microsatellites and mtDNA in red drum are the same. This, in turn, suggests either that gene flow in red drum in the northern Gulf could be biased sexually or that red drum populations may not be in equilibrium between genetic drift and migration. If a sexual bias exists, the observation that divergence in mtDNA is considerably less than 4 times that of microsatellites could suggest female-mediated dispersal and/or male philopatry. The observed isolation-by-distance effect indicates a practical limit to dispersal. Approximate estimates of geographic neighborhood size suggest the limit is in the range 700-900 km. Although the genetic studies of red drum indicate significant genetic divergence across the northern Gulf, the genetic differences do not delimit specific populations or stocks with fixed geographic boundaries. 相似文献
13.
Population genetics of Crassostrea ariakensis in Asia inferred from microsatellite markers 总被引:1,自引:0,他引:1
Jie Xiao Jan F. Cordes Haiyan Wang Ximing Guo Kimberly S. Reece 《Marine Biology》2010,157(8):1767-1781
Crassostrea ariakensis is an important aquacultured oyster species in Asia, its native region. During the past decade, consideration was given to
introducing C. ariakensis into Chesapeake Bay, in the United States, to help revive the declining native oyster industry and bolster the local ecosystem.
Little is known about the ecology and biology of this species in Asia due to confusion with nomenclature and difficulty in
accurately identifying the species of wild populations in their natural environment. Even less research has been done on the
population genetics of native populations of C. ariakensis in Asia. We examined the magnitude and pattern of genetic differentiation among 10 wild populations of C. ariakensis from its confirmed distribution range using eight polymorphic microsatellite markers. Results showed a small but significant
global θ
ST (0.018), indicating genetic heterogeneity among populations. Eight genetically distinct populations were further distinguished
based on population pairwise θ
ST comparisons, including one in Japan, four in China, and three populations along the coast of South Korea. A significant positive
association was detected between genetic and geographic distances among populations, suggesting a genetic pattern of isolation
by distance. This research represents a novel observation on wild genetic population structuring in a coastal bivalve species
along the coast of the northwest Pacific. 相似文献
14.
Kate L. Winters Lynne van Herwerden J. Howard Choat D. R. Robertson 《Marine Biology》2010,157(8):1679-1691
Phylogenetic, phylogeographic, population genetic and coalescence analyses were combined to examine the recent evolutionary
history of the widespread Indo-Pacific parrotfish, Scarus psittacus, over a geographic range spanning three marine biogeographic realms. We sequenced 164 individuals from 12 locations spanning
17,000 km, from 55oE to 143oW, using 322 base pairs of mitochondrial control region (D-loop). S. psittacus displayed high haplotype (h = 0.83–0.98), but low nucleotide (<1%) diversity. Most (>83%) genetic variation was within populations. AMOVA revealed significant
partitioning and identified five geographic groups. These included one central population and four populations peripheral
to the centre. The central population occupied reefs from Western Australia to Tahiti and represented the central Indo-Pacific
biogeographic realm. Cocos Keeling was distinct from central and western Indo-Pacific biogeographic realms occupying a position
intermediate to these. Peripheral populations (Hawaii, Marquesas) represented the eastern Indo-Pacific biogeographic realm,
while Seychelles represented the western Indo-Pacific biogeographic realm. All but the central population expanded (<163 kya).
Whilst all populations experienced major sea level and SST changes associated with Pleistocene glaciation cycles, the genetic
structure of the central population was relatively homogenous unlike the remaining genetically distinctive populations. 相似文献
15.
Mitochondrial DNA and electronic tracking reveal population structure of Atlantic bluefin tuna (Thunnus thynnus) 总被引:1,自引:0,他引:1
Population subdivision was examined in Atlantic bluefin tuna (Thunnus thynnus) through sequencing of the control region of the mitochondrial genome. A total of 178 samples from the spawning grounds in
the Gulf of Mexico, Bahamas and Mediterranean Sea were analyzed. Among the samples from these locations were 36 electronically
tagged bluefin tuna that were tagged in the North Atlantic and subsequently traveled to one of these known spawning grounds
during the spawning season. Bluefin tuna populations from the Gulf of Mexico and the Mediterranean Sea were found to be genetically
distinct based on Φst, and sequence nearest neighbor analyses, showing that these two major spawning areas support independent stocks. Sequence
nearest neighbor analysis indicated significant population subdivision among the Gulf of Mexico, western Mediterranean and
eastern Mediterranean Sea. However, it was not possible to find significant pairwise differences between any sampling areas
when using all samples. If only samples that had a high likelihood of assignment to a specific spawning site were used (young
of the year, spawning adults), the differentiation increased among all sampling areas and the Western Mediterranean Sea was
distinct from the Eastern Mediterranean Sea and the Gulf of Mexico. It was not possible to distinguish samples from the Bahamas
from those collected at any of the other sampling sites. These data support tagging results that suggested distinctness of
the Gulf of Mexico, Eastern and Western Mediterranean Sea spawning areas. This level of stock differentiation is only possible
if Atlantic bluefin tuna show strong natal homing to individual spawning grounds. 相似文献
16.
Spatial and temporal genetic heterogeneity in the sequences of nuclear protein-coding genes were investigated in populations of the blue crab, Callinectes sapidus. Haplotype frequencies of these novel markers were determined for adult crabs collected along 300 km in the northern Gulf of Mexico in two different years (2010 and 2011), as well as for megalopal recruits collected in 2010. Tests of genetic differentiation among all locations and between locations spanning known genetic breaks in other species were conducted. In addition, samples from distant locations within the range of C. sapidus were used to assess genetic divergence on a broader geographic scale. Significant between-year differences were found for adults at one location and near significant spatial differentiation was found across northern Gulf of Mexico locations in 2010. These results suggest that although the large population sizes and meroplanktonic life history of blue crabs promote widespread gene flow on a regional scale, genetic composition can change over just one year. Substantial divergence between the northern Gulf of Mexico and Venezuela suggests the possibility that temporal shifts in haplotype frequencies could result from variation in the rate of immigration from genetically distinct source populations. The possible effects of the Deepwater Horizon Oil Spill and attendant fisheries closures during the sampling phase of this study are also considered. 相似文献
17.
Expression of foreign genes in primary cultured cells of the blue shrimp Penaeus stylirostris 总被引:1,自引:0,他引:1
The ability to introduce and express foreign genes can greatly facilitate in vitro studies of the molecular biology of an
organism. We report here the first use of modified retroviral vectors to achieve foreign gene expression in primary cultured
cells from the Oka organ and ovary of the blue shrimp Penaeus stylirostris (Litopenaeus) stylirostris (Holthuis 1980). Of the heterologous promoters tested, the Moloney murine leukemia virus and Rous sarcoma virus
promoters mediated the highest levels of reporter gene expression. Firefly luciferase and Escherichia coliβ-galactosidase were successfully used as reporter genes in cultured cells from both Oka organ and ovary. These in vitro systems
can be exploited for the study of shrimp cellular biology and regulation of gene expression.
Received: 16 January 2000 / Accepted: 21 June 2000 相似文献
18.
C. S. McFadden R. K. Grosberg B. B. Cameron D. P. Karlton D. Secord 《Marine Biology》1997,128(1):127-139
Along the temperate Pacific coast of North America, the actiniarian sea anemone Anthopleura elegantissima exhibits two discrete life-history phenotypes. Although both forms sexually produce planula larvae, the clonal morph can
also asexually propagate by fission, whereas the solitary morph does not. Whether the two forms constitute one or two species
has long been contested. Hand originally designated the two forms as conspecifics, whereas Francis – on the basis of differences
in microhabitat, biogeographic range and phenotypic frequencies – argued that the two forms constituted a sibling-species
pair. From the results of an electrophoretic survey in which they pooled allelic frequencies across several geographic locations,
Smith and Potts subsequently argued that the two forms were not genetically differentiated, and therefore represented a single
species. We re-examined the relationship between the forms electrophoretically, substantially extending the geographic range
and doubling the sample sizes beyond those used by Smith and Potts, and not pooling allelic frequencies in our analyses. Our
analysis of patterns of genetic variation at ten highly polymorphic allozyme loci shows that although no fixed genetic differences
distinguish the two forms, there are significant differences in allele frequencies between clonal and solitary A.␣elegantissima at every site we sampled throughout their range of sympatry (over 1000 km); within each form, however, there is little detectable
genetic differentiation among populations. We therefore conclude that the two forms represent recently reproductively isolated
taxa, and propose that the clonal form retain the binomial A. elegantissima (Brandt, 1835), whereas the solitary form be described and named a new species, Anthopleura sp.
Received: 28 August 1996 / Accepted: 25 September 1996 相似文献
19.
Vermilion snapper (Rhomboplites aurorubens) were collected from four sites off the Atlantic coast of the USA and one site in the Gulf of Mexico to evaluate effective
population size and genetic stock structure. Previous studies had suggested geographic variation in the ratio of males to
females, so this population characteristic was explored in conjunction with the genetic analysis. Sex ratio varied greatly
among the five sample sites; males comprised 57% of samples in the Gulf of Mexico, while within the South Atlantic Bight they
comprised between 36% (Morehead City, North Carolina) and 53% (Carolina Beach, North Carolina) of samples. No clear geographic
trends in the sex ratio emerged; instead, it was found to vary with fish length, the percentage of males decreasing with increasing
size. Allelic variation assessed at seven dinucleotide microsatellite loci was large; gene diversities ranged from 0.43 to
0.95 and allelic counts from 7 to 39. Estimates of the effective population size ranged from 24 500 (based on the infinite-alleles
model) to 150 500 (based on the stepwise-mutation model). There was evidence for excess homozygosity within samples: estimates
of F
IS
(the correlation of alleles within individuals) ranged from 0.01 to 0.03 among the seven loci, and three estimates were significantly
greater than zero. Differentiation among localities was very weak, as estimates of F
ST
(the correlation of alleles within populations) were on the order of 0.001 to 0.002 and genetic distance estimates between
localities were not related to geographic distances. This suggested that vermilion snapper in the South Atlantic Bight (Cape
Hatteras, North Carolina to Cape Canaveral, Florida) and Gulf of Mexico are likely to consist of one genetic stock. Despite
the overall homogeneity, there were indications of a temporally dynamic local structure that would bear further examination.
Received: 6 July 1998 / Accepted: 9 February 1999 相似文献
20.
M. A. Todaro J. W. Fleeger Y. P. Hu A. W. Hrincevich D. W. Foltz 《Marine Biology》1996,125(4):735-742
Many meiofaunal species are reported to be cosmopolitan, but due to uncertainties of identification, the affiliation of specimens from geographically distant areas to the same species-taxon is problematic. In this study, we examined morphological and molecular variation in samples of Xenotrichula intermedia Remane (Gastrotricha: Chaetonotida) from the Mediterranean Sea, the northwestern Atlantic and the northern Gulf of Mexico. Univariate analysis of 16 morphological traits was unable to detect differences among populations, except for the length of the pharynx, which was significantly shorter in the Gulf of Mexico specimens. Canonical discriminant analysis separated the Gulf of Mexico specimens from the other two populations, with pharynx length contributing about half of the total discrimination. Molecular analysis based on restriction-fragment length polymorphisms (RFLPs) in a 710-base pair polymerase chain-reaction (PCR) produet representing roughly half of the mitochondrial cytochrome oxidase I (COI) gene detected four haplotypes: one each from the Mediterranean and the Gulf of Mexico populations and two coexisting within the Atlantic population. The estimated nucleotide-sequence divergence calculated for each pairwise combination of haplotypes (based on the proportion of shared fragments) ranged from 5.3 to 11.5%. The high genetic divergence and the inability to clearly separate populations based on morphology suggest that individuals characterized by different haplotypes are genetically isolated sibling species. 相似文献