Lin Qiuqi, Xiao Xiao, Feng Xuxin, Lei Lamei
Department of Ecology, Jinan University, Guangzhou 510632, PR China.
Department of Ecology, Jinan University, Guangzhou 510632, PR China.
Harmful Algae. 2025 May;145:102847. doi: 10.1016/j.hal.2025.102847. Epub 2025 Mar 29.
Diaphanosoma, so-called 'tropical Daphnia' are widely distributed in warm waterbodies with Microcystis blooms, and are supposed to have high level of tolerance to Microcystis. However, expanding filamentous cyanobacterium, Raphidiopsis raciborskii is increasingly replacing Microcystis, or becoming co-dominant in warm eutrophic waterbodies. Whether previous experience with Microcystis can facilitate adaptation of Diaphanosoma to R. raciborskii or a shift in cyanobacteria assemblage from Microcystis to R. raciborskii will reduce their tolerance to cyanobacteria is debated. We address this question by investigating the performance of fourteen clones from three Diaphanosoma dubium populations differing in cyanobacteria exposure history. They were fed pure diets of cylindrospermopsin-/non-cylindrospermopsin-producing R. raciborskii, microcystin-producing Microcystis aeruginosa and green alga Auxenochlorella pyrenoidosa. The three cyanobacteria all sustained the growth and reproduction of three D. dubium populations, and both somatic and population growth rates increased with dietary PUFA content for each clone, irrespective of manageability and toxicity. Clones with cyanobacteria exposure history have much better performance than those without exposure history on all food types. Moreover, clones with Microcystis exposure history for >40 years, performed better on all food types than clones with R. raciborskii exposure history for <10 years. The results suggest that D. dubium population with much longer bloom exposure history may adapt to being more tolerant of toxic cyanobacteria in the diet. We infer that previous Microcystis exposure experience might facilitate adaptation of D. dubium to R. raciborskii by enhancing their ability to cope with nutritional constraint and toxicity.
透明溞，即所谓的“热带水蚤”，广泛分布于有微囊藻水华的温暖水体中，且被认为对微囊藻具有较高的耐受性。然而，不断扩张的丝状蓝藻拉氏尖头藻正日益取代微囊藻，或在温暖的富营养水体中成为共优势种。此前与微囊藻的接触经历是否能促进透明溞对拉氏尖头藻的适应，或者蓝藻组合从微囊藻向拉氏尖头藻的转变是否会降低它们对蓝藻的耐受性，目前尚无定论。我们通过研究来自三个透明溞种群的14个克隆的表现来解决这个问题，这些种群在蓝藻暴露历史上存在差异。给它们投喂分别由产柱孢藻毒素/不产柱孢藻毒素的拉氏尖头藻、产微囊藻毒素的铜绿微囊藻和绿藻蛋白核小球藻组成的纯食物。这三种蓝藻均能维持三个透明溞种群的生长和繁殖，并且每个克隆的体细胞和种群生长速率均随食物中多不饱和脂肪酸含量的增加而增加，无论其可处理性和毒性如何。有蓝藻暴露历史的克隆在所有食物类型上的表现都比没有暴露历史的克隆要好得多。此外，有超过40年微囊藻暴露历史的克隆在所有食物类型上的表现都比有不到10年拉氏尖头藻暴露历史的克隆要好。结果表明，具有更长水华暴露历史的透明溞种群可能会适应对食物中有毒蓝藻具有更高的耐受性。我们推断，先前的微囊藻暴露经历可能通过增强其应对营养限制和毒性的能力，促进透明溞对拉氏尖头藻的适应。
