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Heterosigma akashiwo in central California waters

机译：加利福尼亚中部水域的异种赤足

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Heterosigma akashiwo (Hada) gives rise to red tides along the Atlantic and Pacific coasts and is known to produce brevetoxins. This investigation establishes baseline information showing the presence of H. akashiwo along the central California coast based on water samples collected from the Santa Cruz pier in Monterey Bay (on the open coast) and the Berkeley pier in San Francisco Bay. Light and electron microscopy as well as two species-specific DNA probe methods based on cell homogenates preparations were employed to detect H. akashiwo during the 2001-2002 field study. The DNA probe methods consisted of a sandwich hybridization assay (SHA), which targets ribosomal RNA (rRNA), and an end-point polymerase chain reaction (PCR) assay, which targets internal transcribed spacer (ITS) sequences of rRNA genes. The SHA was used to provide semi-quantitative data showing the intermittent presence of the species during a 13-month period in Monterey Bay. Samples that showed a variety of responses in the SHA (negative as well as the highest) were then subjected to the PCR assay in an attempt to confirm species identification using an independent DNA probe method that employs cell homogenates; samples included those from Monterey Bay and one from a red tide event in San Francisco Bay. SHA and PCR assays agreed on the presence or absence of H. akashiwo. Gene products from two field samples positive for H. akashiwo by PCR were cloned and sequenced and found to be identical to those of that species in GenBank. When the same samples were viewed by light microscopy, however, H. akashiwo cells were only seen in the sample with the highest abundance of that species, as evidenced by SHA. It was extremely difficult to recognize naturally occurring H. akashiwo using light microscopy in field samples that had been preserved with Lugol's iodine, including samples that gave positive results by cell homogenate methods. Results of this study indicate that H. akashiwo is present along the open California coast and could easily be missed in routine phytoplankton surveys. Despite its presence, H. akashiwo does not appear to routinely bloom with sufficient densities to cause harmful outbreaks of the frequency and severity documented in some other coastal environments. Molecular identification techniques may be the preferred approach over light microscopy when there is a need to rapidly screen many samples for fragile, harmful species and those that are otherwise problematic to identify based on their gross morphology alone.
机译：杂种赤足鱼（哈达）在大西洋和太平洋沿岸引起红潮，并已知会产生短毒素。这项调查基于从蒙特雷湾（在开阔海岸）的圣克鲁斯码头和旧金山湾的伯克利码头收集的水样，建立了显示加利福尼亚中部海岸沿岸赤藻的基线信息。在2001-2002年的田间研究中，采用光镜和电子显微镜以及两种基于细胞匀浆制剂的物种特异性DNA探针方法来检测akashiwo。 DNA探针方法包括靶向核糖体RNA（rRNA）的三明治杂交检测（SHA）和靶向rRNA基因内部转录间隔区（ITS）序列的终点聚合酶链反应（PCR）检测。 SHA被用来提供半定量数据，该数据显示了该物种在蒙特雷湾13个月内的间歇性存在。然后，对在SHA中显示出多种响应（阴性和最高）的样品进行PCR分析，以尝试使用采用细胞匀浆的独立DNA探针方法来确认物种鉴定。样本包括来自蒙特雷湾的样本和来自旧金山湾的赤潮事件的样本。 SHA和PCR分析一致同意是否存在akashiwo。克隆和测序了来自两个对PCR呈阳性的田野麻疹的田间样品的基因产物，并进行了测序，发现与GenBank中该物种的基因产物相同。然而，当通过光学显微镜观察相同的样品时，如在SHA中所证明的那样，仅在具有该物种最高丰度的样品中看到了赤霞鱼细胞。使用光学显微镜在用Lugol碘保存的野外样品（包括通过细胞匀浆方法产生阳性结果的样品）中使用光学显微镜识别天然存在的H. akashiwo极为困难。这项研究的结果表明，裸露的H. akashiwo存在于加利福尼亚州的开阔海岸上，在常规的浮游植物调查中很容易被遗漏。尽管有其存在，但赤潮H.似乎并没有以足够的密度进行例行开花，以致在其他沿海环境中记录的频率和严重程度造成有害的爆发。当需要快速筛查许多样品中的易碎，有害物质以及仅凭其总体形态难以鉴定的样品时，分子鉴定技术可能是光学显微镜的首选方法。

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