Abstract: Polar zooplankton are particularly sensitive to climate change, and have been used as rapid-responders to indicate climate-induced changes in the fragile Antarctic ecosystem. DNA barcoding provides an alternative approach for rapid zooplankton species identification. Ninety-four specimens belonging to 32 Antarctic zooplankton species were barcoded to construct a comprehensive reference library. An 830 to 1 050 base-pair region of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene was obtained as DNA barcodes. The intraspecific variation of the gene ranged from 0 to 2.6% (p-distance), with an average of 0.67% (SD=0.67%). The distance between species within the same genera ranged from 0.1% (Calanus) to 29.3%, with an average of 15.3% (SD=8.4%). The morphological and genetic similarities between Calanus propinquus and C. simillimus raise new questionsabout the taxonomic status of C. simillimus. With the exception of the two Calanus species, the intraspecific genetic divergence was much smaller than the interspecific divergence among congeneric species, confirming the existence of a barcode gap for Antarctic zooplankton. In addition, species other than Calanus sp. formed a monophyletic group. Therefore, we have confirmed DNA barcoding as an accurate and efficient approach for zooplankton identification in the Antarctic area (except for Hydromedusa, Tunicata, and other gelatinous zooplankton). Indicator vector analysis further confirmed this conclusion. The new primer sets issued here may facilitate the study of Antarctic marine zooplankton species composition by environmental metagenetic analysis.

Key words: Southern Ocean, DNA barcode, Calanus, zooplankton, high-throughput analysis