title: A Cryptic Marine Ciliate Feeds on Progametes of Noctiluca scintillans.
abstract: The dinoflagellate Noctiluca scintillans (Noctiluca) has the ability to reproduce sexually, which may help to increase or restore its population size during periods of blooms or environmental stress. Here, we documented for the first time a marine ciliate Strombidium sp. that feeds on Noctiluca's progametes undergoing stages 5 to 9 of nuclear division. This ciliate frequently swam on or around gametogenic and some vegetative Noctiluca cells. The ciliates associated with gametogenic cells had significantly lower swimming speed and changed direction more frequently than those associated with vegetative cells, which overall increased their time spent around the food patches (progametes). This trophic interaction constitutes an upside-down predator-prey link, in which ciliates within the typical size range of Noctiluca prey, become the predators. Based on the phylogenetic tree (maximum-likelihood), there are 14 environmental clones similar to Strombidium sp. found in other coastal waters, where Noctiluca presence or blooms have been reported. This novel predator-prey relationship could therefore be common in other Noctiluca habitats. Additional studies are needed to assess the magnitude of its impacts on Noctiluca population dynamics and plankton bloom succession.
authors.affiliation: Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region.
authors.forename: Kit Yu Karen
authors.initials: KYK
authors.lastname: Chan
authors.affiliation: Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region; Institute of Hydrobiology, Jinan University, Guangzhou, China.
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Shen
authors.affiliation: Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region.
authors.forename: Shunyan
authors.initials: S
authors.lastname: Cheung
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Landry
authors.affiliation: Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region. Electronic address: liub@ust.hk.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Liu
mesh_terms: D016798:Ciliophora / Q000145:classification / Q000502:physiology*; D004141:Dinoflagellida / Q000502:physiology*; D020387:Food Chain; D010802:Phylogeny; D016053:RNA, Protozoan / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics
chemical_list: D016053:RNA, Protozoan; D012337:RNA, Ribosomal, 18S
keywords: Noctiluca; Strombidium sp.; feeding behavior; progametes; swimming pattern