首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
    
  相似文献   

2.
    
  相似文献   

3.
    
We identified and investigated the potential toxicity of oceanic Pseudo‐nitzschia species from Ocean Station Papa (OSP), located in a high‐nitrate, low‐chlorophyll (HNLC) region of the northeast (NE) subarctic Pacific Ocean. Despite their relatively low abundances in the indigenous phytoplankton assemblage, Pseudo‐nitzschia species richness is high. The morphometric characteristics of five oceanic Pseudo‐nitzschia isolates from at least four species are described using SEM and TEM. The species identified are Pseudo‐nitzschia dolorosa Lundholm et Moestrup, P. granii Hasle, P. heimii Manguin, and P. cf. turgidula (Hust.) Hasle. Additional support for the taxonomic classifications based on frustule morphology is provided through the sequencing of the internal transcribed spacer 1 (ITS1) rDNA. Pseudo‐nitzschia species identification was also assessed by the construction of ITS1 clone libraries and using automated ribosomal intergenic spacer analysis (ARISA) for environmental samples collected during the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES), conducted in close proximity to OSP in July of 2002. Based on ITS1 sequences, the presence of P. granii, P. heimii, P. cf. turgidula, and at least five other putative, unidentified Pseudo‐nitzschia ITS1 variants was confirmed within iron‐enriched phytoplankton assemblages at OSP. None of the oceanic isolates produced detectable levels of particulate domoic acid (DA) when in prolonged stationary phase due to silicic acid starvation. The lack of detectable concentrations of DA suggests that either these strains produce very little or no toxin, or that the physiological conditions required to promote particulate DA production were not met and thus differ from their coastal, toxigenic congeners.  相似文献   

4.
    
Very little information is available on the genetic structure of populations of phytoplankton species. Here we report the characterization of six polymorphic microsatellite loci in the marine diatom, Pseudo‐nitzschia pungens, using clones (between 87 and 213 per locus) isolated from spring blooms in the North Sea. The number of alleles per locus ranged from five to 19 and observed heterozygosities ranged from 0.55 to 0.86.  相似文献   

5.
    
We used a multistrain approach to study the intra‐ and interspecific variability of the growth rates of three Pseudo‐nitzschia species – P. australis, P. fraudulenta, and P. pungens – and of their domoic acid (DA) production. We carried out mating and batch experiments to investigate the respective effects of strain age and cell size, and thus the influence of their life cycle on the physiology of these species. The cell size – life cycle relationship was characteristic of each species. The influence of age and cell size on the intraspecific variability of growth rates suggests that these characteristics should be considered cautiously for the strains used in physiological studies on Pseudo‐nitzschia species. The results from all three species do not support the hypothesis of a decrease in DA production with time since isolation from natural populations. In P. australis, the cellular DA content was rather a function of cell size. More particularly, cells at the gametangia stage of their life cycle contained up to six times more DA than smaller or larger cells incapable of sexual reproduction. These findings reveal a link between P. australis life cycle and cell toxicity. This suggest that life cycle dynamics in Pseudo‐nitzschia natural populations may influence bloom toxicity.  相似文献   

6.
    
The toxigenic diatom Pseudo‐nitzschia cuspidata, isolated from the U.S. Pacific Northwest, was examined in unialgal batch cultures to evaluate domoic acid (DA) toxicity and growth as a function of light, N substrate, and growth phase. Experiments conducted at saturating (120 μmol photons · m?2 · s?1) and subsaturating (40 μmol photons · m?2 · s?1) photosynthetic photon flux density (PPFD), demonstrate that P. cuspidata grows significantly faster at the higher PPFD on all three N substrates tested [nitrate (NO3?), ammonium (NH4+), and urea], but neither cellular toxicity nor exponential growth rates were strongly associated with one N source over the other at high PPFD. However, at the lower PPFD, the exponential growth rates were approximately halved, and the cells were significantly more toxic regardless of N substrate. Urea supported significantly faster growth rates, and cellular toxicity varied as a function of N substrate with NO3?‐supported cells being significantly more toxic than both NH4+‐ and urea‐supported cells at the low PPFD. Kinetic uptake parameters were determined for another member of the P. pseudodelicatissima complex, P. fryxelliana. After growth of these cells on NO3? they exhibited maximum specific uptake rates (Vmax) of 22.7, 29.9, 8.98 × 10?3 · h?1, half‐saturation constants (Ks) of 1.34, 2.14, 0.28 μg‐at N · L?1, and affinity values (α) of 17.0, 14.7, 32.5 × 10?3 · h?1/(μg‐at N · L?1) for NO3?, NH4+ and urea, respectively. These labo‐ratory results demonstrate the capability of P. cuspidata to grow and produce DA on both oxidized and reduced N substrates during both exponential and stationary growth phases, and the uptake kinetic results for the pseudo‐cryptic species, P. fryxelliana suggest that reduced N sources from coastal runoff could be important for maintenance of these small pennate diatoms in U.S. west coast blooms, especially during times of low ambient N concentrations.  相似文献   

7.
    
A nonaxenic isolate of the potentially toxic diatom Pseudo‐nitzschia australis (Frenguelli) from Irish waters was tested in two separate batch culture experiments. When grown under a low irradiance (～12 μmol photons·m ? 2·s ? 1 1 Received 20 March 2001. Accepted 21 August 2002.
; 16:8‐h light:dark cycle) for up to 40 days, the culture produced only trace amounts of the neurotoxin domoic acid (DA) during late stationary phase. Growth at a higher irradiance (～115 μmol photons·m ? 2·s ? 1 1 Received 20 March 2001. Accepted 21 August 2002.
; 12:12‐h light:dark cycle) resulted in DA production starting during late exponential phase and reaching a maximum concentration of 26 pg DA·cell ? 1 1 Received 20 March 2001. Accepted 21 August 2002.
during late stationary phase. Liquid chromatography coupled to mass spectrometry was used to confirm the identity of DA in the culture. Irradiance and photoperiod could be important factors that contribute directly or indirectly to the control of DA production in P. australis. This is the first record of a DA‐producing diatom in Irish waters, and results indicate P. australis may have been the source of DA that has recently contaminated shellfisheries in this area.  相似文献   

8.
    
Considering the lack of knowledge on genetic variation on members of the freshwater red algal of the order Batrachospermales in tropical regions, phylogeographic patterns in Sirodotia populations were investigated using two mitochondrial regions: the cox2‐3 spacer and partial cox1 gene (barcode). Individuals identified as Sirodotia delicatula were analyzed from 14 stream segments across its distribution in Brazil. Phylogenetic analyses based on the ribulose‐1,5‐bisphosphate carboxylase/oxygenase large sub‐unit gene showed three clades, one representing S. delicatula, from all locations in southeastern Brazil and other regions from Brazil. The remaining samples formed two clades, which were highly divergent and distantly positioned from those of S. delicatula: 2.5–2.7% and 3.4–3.7%. This level of variation would warrant the species split of these taxa from mid‐western Brazil. A total of eight cox2‐3 spacer and nine cox1 haplotypes were observed among the 122 individuals studied. One location had two cox2‐3 haplotypes and three locations had two cox1 haplotypes; all others had a single dominant haplotype each. The existence of high intraspecific genetic variation among individuals of distinct locations (several haplotypes), but little variation within a location seems to be a pattern for the Batrachospermales. Haplotype networks showed low variation among the haplotypes from southeastern Brazil (10 locations with divergence of 0.3–1.1% for cox2‐3, 0.1–0.3% for cox1) and high variation among the haplotypes from the mid‐west region (four locations, 4.0–9.3% for cox2‐3, 6.2–8.4% for cox1). Thus, the present data clearly suggest the existence of cryptic species in Sirodotia in Brazil.  相似文献   

9.
    
Salinity varies widely in coastal areas that often have a high abundance of Pseudo‐nitzschia H. Peragallo. Pseudo‐nitzschia is abundant in Louisiana waters, and high cellular domoic acid has been observed in natural samples but no human illness has been reported. To assess the threat of amnesic shellfish poisoning (ASP), we examined the effect of salinity on Pseudo‐nitzschia occurrence in the field and growth in the laboratory with special emphasis on the salinity range where oysters are harvested (10–20 psu). In Louisiana coastal waters, Pseudo‐nitzschia spp. occurred over a salinity range of 1 to >35 psu, but they occurred more frequently at higher rather than lower salinities. Seven species were identified, including toxigenic species occurring at low salinities. In culture studies, seven clones of three species grew over a salinity range of 15 to 40 psu, some grew at salinities down to 6.25 psu, and most grew at salinities up to 45 psu. Tolerance of low salinities decreased from Pseudo‐nitzschia delicatissima (Cleve) Heiden to P. multiseries (Hasle) Hasle to P. pseudodelicatissima (Hasle) Hasle emend. Lundholm, Hasle et Moestrup. In conclusion, although Pseudo‐nitzschia was more prevalent in the field and grew better in the laboratory at higher salinities, it grew and has been observed at low salinities. Therefore, the probability of ASP from consumption of oysters harvested from the low salinity estuaries of the northern Gulf of Mexico is low but not zero; animal mortality events from toxin vectors other than oysters at higher salinity on the shelf are more likely.  相似文献   

10.
    
Sexual reproduction is documented for the first time in field populations of the pennate diatoms Pseudo‐nitzschia australis Freng. and P. pungens (Grunow ex Cleve) Hasle (var. cingulata Villac and hybrids between var. cingulata and var. pungens). A bloom dominated by these species began on June 26, 2006, along Kalaloch Beach, Washington, USA, coincident with a drop in the Si(OH)4:NO3 ratio to below two. Multimodal size distributions were detected for both species, and synchronous auxosporulation occurred within the smallest size class during a 3‐week window. Auxospores and initial cells created a new class of large cells, and cells in the intermediate size classes increased in abundance during auxosporulation. Mating cells of both species were attached to colonies of surf‐zone diatoms. Paired gametangia, gametes, zygotes, auxospores, and large initial cells were found. Auxosporulation began first for P. pungens (June 30), apparently once a critical, high cell concentration was reached, followed by P. australis (July 5), when the total Pseudo‐nitzschia cell concentration reached 929,000 cells · L?1. Low frequencies of auxosporulation occurred throughout the bloom but increased 4‐fold for P. australis and 3‐fold for P. pungens when macronutrients were reduced to low levels on July 11. A 2‐year life cycle was estimated for P. australis and 3 years for P. pungens, both with annual auxosporulation. Domoic acid (DA) in razor clams reached a maximum of 38 μg DA · g?1 on July 18. A significant relationship existed between the percent of cells within the new size range and DA concentrations in razor clams on the same beach.  相似文献   

11.
    
  相似文献   

12.
    
The Synura petersenii species complex represents a common, cosmopolitan and highly diverse taxon of autotrophic freshwater flagellates. In this paper, we describe and characterize four new species (S. borealis, S. heteropora, S. hibernica and S. laticarina) that have been identified during our extensive sampling of freshwater habitats in 15 European countries. Morphometric analyses of siliceous scales led to the significant phenotypic differentiation of all four newly described species, and their separation from other related species of the S. petersenii complex. Two of these newly described species (S. hibernica and S. borealis) can be clearly distinguished by characteristic large colonies consisting of elongated, lanceolate-shaped cells. Development of strongly elongated, narrow cells in S. hibernica could be explained by the adaptation of this species to oligotrophic conditions. Though morphologically distinct, S. borealis possesses an exceptionally high degree of genetic diversity, possibly indicating recent speciation and evolutionary diversification within this taxon. Three of the four newly described species exhibit restricted biogeographic distribution. The evolutionarily related S. borealis and S. laticarina occur only in Northern Europe, and seem to be adapted to colder areas. The most remarkable distribution pattern was observed for S. hibernica, which has a geographic distribution that is restricted to western Ireland.  相似文献   

13.
    
This study examined how light and temperature interact to influence growth rates, chl a, and photosynthetic efficiency of the oceanic pennate diatom Pseudo‐nitzschia granii Hasle, isolated from the northeast subarctic Pacific. Growth rates were modulated by both light and temperature, although for each irradiance tested, the growth rate was always the greatest at ～14°C. Chl a per cell was affected primarily by temperature, except at the maximum chl a per cell (at 10°C) where the effects of light were noticeable. At both ends of the temperature gradient, cells displayed evidence of chlorosis even at low light intensities. Chl fluorescence data suggested that cells at 8°C were significantly more efficient in their photosynthetic processes than cells at 20°C, despite having comparable concentrations of chl. Cells at low temperature showed photosynthetic characteristics similar to high‐irradiance‐adapted cells. The decline of growth rates beyond the optimum growth temperature coincided with the cell's inability to accumulate chl in response to increasing temperature. The decline in photosynthetic ability at 20°C was likely due to a combination of high‐temperature stress on cellular membranes and a decline in chl. Our results highlight the important interactions between light and temperature and the need to incorporate these interactions into the development of phytoplankton models for the subarctic Pacific.  相似文献   

14.
    
Several coastal countries including France have experienced serious and increasing problems related to Pseudo‐nitzschia toxic blooms. These toxic blooms occur in estuarine and coastal waters potentially subject to fluctuations in salinity. In this study, we document for the first time the viability, growth, photosynthetic efficiency, and toxin production of two strains of Pseudo‐nitzschia australis grown under conditions with sudden salinity changes. Following salinity variation, the two strains survived over a restricted salinity range of 30–35, with favorable physiological responses, as the growth, effective quantum yield and toxin content were high compared to the other conditions. In addition, high cellular quotas of domoic acid (DA) were observed at a salinity of 40 for the strain IFR‐PAU‐16.1 in comparison with the other strain IFR‐PAU‐16.2 where the cell DA content was directly released into the medium. On the other hand, the osmotic stress imposed at lower salinities, 20 and 10, resulted in cell lysis and a sudden DA leakage in the medium. Intra‐specific variability was observed in growth and toxin production, with the strain IFR‐PAU‐16.1 apparently able to withstand higher salinities than the strain IFR‐PAU‐16.2. On the whole, DA does not appear to act as an osmolyte in response to sudden salinity changes. Since most of the shellfish harvesting areas of bivalve molluscs in France are located in areas where the salinity generally varies between 30 and 35, Pseudo‐nitzschia australis blooms might potentially impact public health and commercial shellfish resources in these places.  相似文献   

15.
    
The pigment composition of 18 species (51 strains) of the pennate diatom Pseudo‐nitzschia was examined using HPLC. The carotenoid composition was typical for diatoms, with fucoxanthin (the major xanthophyll), diadinoxanthin, diatoxanthin, and β,β‐carotene. However, a diverse array of chl c pigments was observed in the studied strains. All Pseudo‐nitzschia strains contained chl a and chl c2, traces of Mg‐2,4‐divinyl phaeoporphyrin a5 monomethyl ester (MgDVP), and traces of a chl c2–like pigment originally found in the haptophyte Pavlova gyrans. The distribution of chl c1 and chl c3 was variable among species (present in seven and 14 species, respectively). Based on chl c distribution, three major pigment types were defined: type 1 (chl c1 + c2, four species: P. australis, P. brasiliana, P. multiseries, and P. seriata), type 2 (chl c1 + c2 + c3, three species: P. fraudulenta, P. multistriata, and P. pungens), and type 3 (chl c2 + c3, 11 species: P. arenysensis, P. calliantha, P. cuspidata, P. decipiens, P. delicatissima, P. galaxiae, P. mannii, P. pseudodelicatissima, P. subcurvata, P. cf. subpacifica, and a novel Pseudo‐nitzschia species). Type 1 and 2 species also shared the absence of a particular morphological character, the central nodule in the raphe, with the only exception of P. fraudulenta. The implications of such pigment diversity in chemotaxonomy, HAB monitoring, ecology, and phylogeny of Pseudo‐nitzschia species are discussed.  相似文献   

16.
    
Lobophora is a common tropical to temperate genus of brown algae found in a plethora of habitats including shallow and deep‐water coral reefs, rocky shores, mangroves, seagrass beds, and rhodoliths beds. Recent molecular studies have revealed that Lobophora species diversity has been severely underestimated. Current estimates of the species numbers range from 100 to 140 species with a suggested center of diversity in the Central Indo‐Pacific. This study used three molecular markers (cox3, rbcL, psbA), different single‐marker species delimitation methods (GMYC, ABGD, PTP), and morphological evidence to evaluate Lobophora species diversity in the Western Atlantic and the Eastern Pacific oceans. Cox3 provided the greatest number of primary species hypotheses(PSH), followed by rbcL and then psbA. GMYC species delimitation analysis was the most conservative across all three markers, followed by PTP, and then ABGD. The most informative diagnostic morphological characters were thallus thickness and number of cell layers in both the medulla and the dorsal/ventral cortices. Following a consensus approach, 14 distinct Lobophora species were identified in the Western Atlantic and five in the Eastern Pacific. Eight new species from these two oceans were herein described: L. adpressa sp. nov., L. cocoensis sp. nov., L. colombiana sp. nov., L. crispata sp. nov., L. delicata sp. nov., L. dispersa sp. nov., L. panamensis sp. nov., and L. tortugensis sp. nov. This study showed that the best approach to confidently identify Lobophora species is to analyze DNA sequences (preferably cox3 and rbcL) followed by comparative morphological and geographical assessment.  相似文献   

17.
    
Several species of the diatom Pseudo‐nitzschia produce the neurotoxin domoic acid (DA). Consumption of fish and shellfish that have accumulated this potent excitotoxin has resulted in severe illness and even death in humans, marine mammals, and seabirds. Pseudo‐nitzschia pungens (Grunow ex Cleve) Hasle is a cosmopolitan diatom commonly occurring in the waters of the Pacific Northwest (PNW) and the eastern North Atlantic, including the North Sea. However, genetic and physiological relationships among populations throughout this large geographic distribution have not been assessed. Population genetic parameters (e.g., Hardy–Weinberg equilibrium, linkage equilibrium, FST) calculated for P. pungens collected from the Juan de Fuca eddy region in the PNW indicated the presence of two distinct groups that were more divergent from each other than either was from a P. pungens sample from the North Sea. Geographic heterogeneity was also detected within each of the two PNW groups. These results suggested that the populations of P. pungens recently mixed in the Juan de Fuca eddy region (a seasonally retentive feature off the coasts of Washington State, USA, and Vancouver Island, Canada) but did not exchange genetic material by sexual reproduction. Alternatively, these two groups may be cryptic (morphologically identical, but reproductively isolated) species. Identifying cryptic diversity in Pseudo‐nitzschia is important for bloom prediction and aiding the identification of molecular markers that can be used for rapid detection assay development.  相似文献   

18.
    
The genetic structure of phytoplankton populations is largely unknown. In this study we developed nine polymorphic microsatellite markers for the domoic acid–producing marine diatom Pseudo‐nitzschia multiseries (Hasle) Hasle. We then used them in the genotyping of 25 physiologically diverse field isolates and six of their descendants: 22 field isolates originated from eastern Canadian waters, two from European waters, and one from Russian waters. The numbers of alleles per locus ranged from three to seven and the observed heterozygosities from 0.39 to 0.70. A substantial degree of genetic variation was observed within the field isolates, with 23 different genotypes detected. The Russian isolate was the most genetically distinct, although there was also evidence of genetic differentiation at a more local scale. Mating experiments demonstrated that alleles were inherited in a Mendelian manner. Pseudo‐nitzschia multiseries primer pairs were tested on DNA from four congeners: P. calliantha Lundholm, Moestrup et Hasle; P. fraudulenta (P. T. Cleve) Hasle; P. pungens (Grunow ex P. T. Cleve) Hasle; and P. seriata (P. T. Cleve) H. Peragallo. Cross‐reactivity was only observed in P. pungens. Our results are a first step in understanding the genetic variation present at the Pseudo‐nitzschia“species” level and in determining the true biogeographic extent of Pseudo‐nitzschia species.  相似文献   

19.
    
Blooms of the toxin‐producing diatom Pseudo‐nitzschia commonly occur in Monterey Bay, California, resulting in sea lion mortality events. The links between strandings of California sea lions suffering from domoic acid (DA) toxicity, toxic cell numbers, and their associated DA concentration in Monterey Bay and in sea lion feces were examined from 2004 to 2007. While Pseudo‐nitzschia toxic cells and DA concentrations were detectable in the water column most of the time, they were often at low levels. A total of 82 California sea lions were found stranded in the Bay between 2004 and 2007 with acute or chronic signs associated with DA poisoning. The highest number with detectable DA in feces occurred in April 2007 and corresponded with the presence of a highly toxic bloom in the Bay. Higher DA levels occurred in feces from sea lions stranding with acute toxicosis and lower concentrations in feces of sea lions exhibiting signs of chronic DA poisoning or not exhibiting any neurologic signs. Results indicated that sea lions are likely exposed to varying levels of DA through their prey throughout the year, often at sublethal doses that may contribute to a continued increase in the development of chronic neurologic sequelae.  相似文献   

20.
    
A flow cytometer coupled to a scanning monochromator and a fluorescence microscope were used to characterize the fluorescence spectrum of Pseudo‐nitzschia multiseries (Hasle) Hasle, a pennate diatom that produces the neurotoxin domoic acid, a lethal amnesic. In this research, we characterize the fluorescence spectrum of P. multiseries in vivo over the wavelength range of 360 to 850 nm and show that this diatom autofluoresces blue when excited with UV light (350–365 nm). The autofluorescence characterization of Pseudo‐nitzschia may provide new methods for rapid in situ monitoring of diatom populations and reiterates the usefulness of flow cytometry in the analysis and study of marine phytoplankton.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号