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Arrow worms (Phylum Chaetognatha) are abundant planktonic organisms and important predators in many food webs; yet, the classification and evolutionary relationships among chaetognath species remain poorly understood. A seemingly simple body plan is underlain by subtle variation in morphological details, obscuring the affinities of species within the phylum. Many species achieve near global distributions, spanning the same latitudinal bands in all ocean basins, while others present disjunct ranges, in some cases with the same species apparently found at both poles. To better understand how these complex evolutionary and geographic variables are reflected in the species makeup of chaetognaths, we analyze DNA barcodes of the mitochondrial cytochrome oxidase c subunit I (COI) gene, from 52 specimens of 14 species of chaetognaths collected mainly from the Atlantic Ocean. Barcoding analysis was highly successful at discriminating described species of chaetognaths across the phylum, and revealed little geographical structure. This barcode analysis reveals hitherto unseen genetic variation among species of arrow worms, and provides insight into some species relationships of this enigmatic group.


Originally published in the open access journal PLoS ONE:

This research was partially funded by NOAA's Office of Ocean Exploration (Award No. NA050AR4601079). Funding to APB was provided by MAR-ECO ( Samples collected by Ksenia Kosobokova and kindly contributed by her were supported by the Russian Foundation for Basic Research (Award No. 06-05-65187). The authors gratefully acknowledge the support of the Alfred P. Sloan Foundation. This study is a contribution from the Census of Marine Zooplankton (CMarZ,, an ocean realm field project of the Census of Marine Life ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


Public Library of Science (PLoS)


© 2010 Jennings et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



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