University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT, 06340, USA.
Harmful Algae. 2019 Apr;84:181-187. doi: 10.1016/j.hal.2019.04.006. Epub 2019 Apr 18.
Dinoflagellate paralytic shellfish toxin (PST) production is mediated by several abiotic and biotic factors. This study compared the relative importance of nitrogen source and concentration, prey alarm cues and grazer presence on toxin production of the marine dinoflagellate Alexandrium catenella (Group I, strain BF-5). In separate assays run under either nutrient-replete (F/2 medium) or nutrient-depleted (filtered seawater) conditions, PST production of A. catenella was measured as a function of varying concentrations of added nitrogen sources (ammonium and urea), alarm cues from lysed conspecific (A. catenella Group I strains) and interspecific (the diatom, Thalassiosira weissflogii, and the green flagellate, Tetraselmis sp.) algae, and the presence of a grazer (the copepod Acartia hudsonica). Results showed that addition of ammonium or urea did not increase PST production. Unexpectedly, interspecific alarm cues increased toxin production but conspecific ones did not. Grazer presence dramatically induced PST production in A. catenella, irrespective of nutrient conditions, and this effect was an order of magnitude greater than any of the other variables tested. These results corroborate previous studies on grazer-induced PST production, and support the hypothesis that grazer-induced toxin production is not an experimental artifact, but rather a prey defense mechanism.
甲藻麻痹性贝类毒素（PST）的产生受多种非生物和生物因素的影响。本研究比较了氮源和浓度、猎物警报信号和摄食者存在对海洋甲藻亚历山大藻（I 组，BF-5 株）产毒的相对重要性。在分别进行的富营养（F/2 培养基）和贫营养（过滤海水）条件下的实验中，测定了添加不同浓度氮源（铵盐和尿素）、来自裂解同种（I 组亚历山大藻）和异源（硅藻塔玛亚历山大藻和绿藻四鞭藻）藻类的警报信号以及摄食者（桡足类桡足类 Hudsonica）存在对亚历山大藻 PST 产生的影响。结果表明，添加铵盐或尿素不会增加 PST 的产生。出乎意料的是，异源警报信号增加了毒素的产生，但同种警报信号没有。摄食者的存在显著诱导了亚历山大藻 PST 的产生，而与营养条件无关，这种效应比其他测试变量的任何一个都大一个数量级。这些结果与之前关于摄食者诱导 PST 产生的研究结果一致，并支持了这样一种假设，即摄食者诱导的毒素产生不是实验假象，而是一种猎物防御机制。
