黄河口邻近水域中华哲水蚤现场食物组成的分子生物学检测

PCR-Based in situ Dietary Analysis of Calanus sinicus Brodsky in Yellow River Estuary and Adjacent Waters

浮游桡足类是海洋初级生产力和高级营养级之间能量传递的重要中介,对自然海区桡足类食物组成的研究是深入了解其在海洋食物网所处生态地位的关键。然而,由于研究方法的局限,目前很难获取桡足类准确的现场摄食信息。本文用分子生物学方法研究了黄河口邻近水域中华哲水蚤的现场食物组成,对现场采集固定的中华哲水蚤样品进行清洗、去除附肢、镜检等处理,研磨匀浆后提取总基因组DNA。基于对以此DNA为模板扩增出的非桡足类核糖体小亚基基因(non-copepod 18SrDNA)序列的分析,本文共检测出属于8个门的中华哲水蚤的潜在食物种类。研究结果表明,PCR的分子生物学技术在桡足类摄食研究中具有强大的效用,同时,诸多潜在食物类群的发现也意味着利用分子生物学方法对桡足类及其它海洋生物现场食物组成进行深入系统研究,将有利于揭示海洋生态系统结构与功能的真实状态,促进海洋生态系统物质循环和能量流动的研究。

Marine pelagic copepods are conventionally considered as the key linkage between primary production and higher trophie levels in the marine food web. Information on the natural diets of copepods in situ has pivotal impact on the understanding of the structure and function of the marine food web and yet remains obscure. Here we report, using an 18S rDNA-based molecular approach, on natural diets of Calanus sinicus in Yellow River estuary and adjacent waters. The incubation-free analysis showed that diets of C. sinicus were diverse, including organisms from 8 phyla, many of which were never suspected to be prey of copepods. Most of the sequences （52%） were of jellyfish （Ctenophora and Hydrozoa） and substantial amount （16%） originated from Syndiniales, the parasitic lineage of dinoflagellates. In contrast to the previous studies, the proportion of diatoms was relatively small （12%）. The remaining sequences belonged to green algae （Chlorophyta）, cryptophytes （Cryptophyta）, non-Syndiniales dinoflagellates （Dinophyceae）, molluscs （Mollusca） and potential parasites （Ichthyosporea）. We show that C. sinicus feeds diversely but likely prefer particular species of jellyfish larvae, and demonstrate the power of PCR-based molecular method to uncover the in situ diet of copepods, which would not be found through traditional methods. Moreover, the discovery of new probable prey species highlights that a systematic analysis is needed for informed feeding experiment on this copepod to understand its true trophic interactions in the pelagic ecosystem.