title: Heterokont Predator Develorapax marinus gen. et sp. nov. - A Model of the Ochrophyte Ancestor.
abstract: Heterotrophic lineages of Heterokonta (or stramenopiles), in contrast to a single monophyletic group of autotrophs, Ochrophyta, form several clades that independently branch off the heterokont stem lineage. The nearest neighbors of Ochrophyta in the phylogenetic tree appear to be almost exclusively bacterivorous, whereas the hypothesis of plastid acquisition by the ancestors of the ochrophyte lineage suggests an ability to engulf eukaryotic alga. In line with this hypothesis, the heterotrophic predator at the base of the ochrophyte lineage may be regarded as a model for the ochrophyte ancestor. Here, we present a new genus and species of marine free-living heterotrophic heterokont Develorapax marinus, which falls into an isolated heterokont cluster, along with the marine flagellate Developayella elegans, and is able to engulf eukaryotic cells. Together with environmental sequences D. marinus and D. elegans form a class-level clade Developea nom. nov. represented by species adapted to different environmental conditions and with a wide geographical distribution. The position of Developea among Heterokonta in large-scale phylogenetic tree is discussed. We propose that members of the Developea clade represent a model for transition from bacterivory to a predatory feeding mode by selection for larger prey. Presumably, such transition in the grazing strategy is possible in the presence of bacterial biofilms or aggregates expected in eutrophic environment, and has likely occurred in the ochrophyte ancestor.
authors.affiliation: Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State UniversityMoscow, Russia; Kharkevich Institute for Information Transmission Problems, Russian Academy of SciencesMoscow, Russia; Institute of Animal Physiology, Biochemistry and NutritionKaluga, Russia.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Aleoshin
authors.affiliation: Institute for the Biology of Inland Waters, Russian Academy of Sciences Borok, Russia.
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Mylnikov
authors.affiliation: Institute of Gene Pool of Plants and Animals, Uzbek Academy of SciencesTashkent, Uzbekistan; National University of UzbekistanTashkent, Uzbekistan.
authors.forename: Gulnara S
authors.initials: GS
authors.lastname: Mirzaeva
authors.affiliation: Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State UniversityMoscow, Russia; Kharkevich Institute for Information Transmission Problems, Russian Academy of SciencesMoscow, Russia.
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Mikhailov
authors.affiliation: Zoological Institute, Russian Academy of SciencesSt. Petersburg, Russia; St. Petersburg State UniversitySt. Petersburg, Russia.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Karpov
keywords: Develorapax marinus; molecular phylogeny; ochrophyte ancestor; prey size; ultrastructure