title: Cyst-Theca Relationship and Phylogenetic Position of Impagidinium caspienense Incubated from Caspian Sea Surface Sediments: Relation to Gonyaulax baltica and Evidence for Heterospory within Gonyaulacoid Dinoflagellates.
abstract: We investigate the cyst-theca relationship of Impagidinium caspienense. Through an incubation experiment, we succeeded in examining the motile stage. Additional molecular analysis of single-cyst PCR (LSU and SSU rDNA) reveal that the cyst is related to the species Gonyaulax baltica Ellegaard et al. (). The ability of this species to belong to two types of cyst-based genera (spiniferate and impagidinioid) suggests that environmental (particularly salinity) and not genetic factors explain the formation of both morphotypes by G. baltica, which provides evidence for heterospory in this species. The affiliation to G. baltica demonstrates that I. caspienense is not endemic to the Caspian Sea. The phylogenetic position of several other gonyaulacoid species is also documented: Impagidinium pallidum, Ataxiodinium choane, Pyxidinopsis psilata, Spiniferites belerius, and Spiniferites ramosus. The LSU and SSU rDNA based phylogenies suggest that the genera Impagidinium and Spiniferites are not monophyletic, and that P. psilata and A. choane are close to Gonyaulax verior and Gonyaulax polygramma, respectively. In addition, this study accentuates the importance of cyst morphology in the classification of the Gonyaulacales.
authors.affiliation: Ifremer, LER BO, Station de Biologie Marine, Place de la Croix, BP40537, Concarneau Cedex, F-29185, France.
authors.forename: Kenneth N
authors.identifier: 0000-0003-2005-9483
authors.initials: KN
authors.lastname: Mertens
authors.affiliation: Institute for East China Sea Research (ECSER), 1-14, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Takano
authors.affiliation: Third Institute of Oceanography, SOA, Xiamen, 361005, China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Gu
authors.affiliation: Inland Waters Aquaculture Research Center, Iranian Fisheries Science Institute, Agricultural Research Education and Extension Organization (AREEO), 66, Anzali, Iran.
authors.forename: Siamak
authors.initials: S
authors.lastname: Bagheri
authors.affiliation: School of Earth and Ocean Sciences, University of Victoria, OEASB A405, P.O. Box 1700 STN CSC, Victoria, BC, V8W 2Y2, Canada.
authors.forename: Vera
authors.initials: V
authors.lastname: Pospelova
authors.affiliation: Department of Physical Sciences, MacEwan University, Edmonton, AB, T5J 4S2, Canada.|School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, United Kingdom.
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Pieńkowski
authors.affiliation: Institute for the Environment, Brunel University London, Uxbridge, UB8 3PH, United Kingdom.
authors.forename: Suzanne A G
authors.initials: SAG
authors.lastname: Leroy
authors.affiliation: Institute for East China Sea Research (ECSER), 1-14, Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsuoka
mesh_terms: D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004141:Dinoflagellida / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D019015:Geologic Sediments / Q000469:parasitology*; D008124:Locomotion; D008853:Microscopy; D009792:Oceans and Seas; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012335:RNA, Ribosomal / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; C065096:RNA, ribosomal, 26S
keywords: 
  Ataxiodinium choane
  ; 
  Impagidinium pallidum
  ; 
  Pyxidinopsis psilata
  ; 
  Spiniferites belerius
  ; 
  Spiniferites ramosus
  ; Baltic Sea; salinity