The affiliation of Hexasterias problematica and Halodinium verrucatum sp. nov. to ciliate cysts based on molecular phylogeny and cyst wall composition
|Author(s)||Gurdebeke Pieter R.1, Mertens Kenneth2, Takano Yoshihito3, Yamaguchi Aika4, Bogus Kara5, 6, Dunthorn Micah7, Matsuoka Kazumi3, Vrielinck Henk8, Louwye Stephen1|
|Affiliation(s)||1 : Univ Ghent, Dept Geol, Krijgslaan 281, B-9000 Ghent, Belgium.
2 : Ifremer, Stn Biol Marine, LER BO, Pl Croix,BP40537, F-29185 Concarneau, France.
3 : Inst East China Sea Res ECSER, 1-14 Bunkyo Machi, Nagasaki 8528521, Japan.
4 : Kobe Univ, Res Ctr Inland Seas, Kobe, Hyogo 6578501, Japan.
5 : Univ Nottingham, Sch Geog, Ctr Environm Geochem, Nottingham NG7 2RD, England.
6 : Texas A&M Univ, Int Ocean Discovery Program, College Stn, TX 77845 USA.
7 : Univ Kaiserslautern, Dept Ecol, Erwin Schrodinger St, D-67663 Kaiserslautern, Germany.
8 : Univ Ghent, Dept Solid State Sci, Krijgslaan 281,S1, B-9000 Ghent, Belgium.
|Source||European Journal Of Protistology (0932-4739) (Elsevier Gmbh, Urban & Fischer Verlag), 2018-10 , Vol. 66 , P. 115-135|
|WOS© Times Cited||16|
|Keyword(s)||Acritarch, Ciliate cyst, FTIR, LSU-SSU rDNA, Prostomatida, Taxonomy|
Species in the genera Hexasterias and Halodinium have been recorded over the last decades as acritarchs in palynological and/or plankton studies. In paleoenvironmental studies, these resting stages are often interpreted as indicators of freshwater input. The biological affinity of these genera has never been definitely established. Here, a new species, Halodinium verrucatum sp. nov., is described and molecular evidence (single specimen SSU and LSU rDNA sequencing) reveals that both this new species and Hexasterias problematica, collected from sediment samples in the Skagerrak and Baltic Sea, are resting stages of prorodontid ciliates. Additionally, infrared spectroscopic analysis (micro-FTIR) of Hexasterias problematica and Halodinium spp. specimens indicates a carbohydrate-based composition of the cyst wall with evidence for nitrogen-containing functional groups. A similar composition is recorded for tintinnid loricae, which further supports the placement of Hexasterias and Halodinium as ciliate cysts, and the composition is consistent with the heterotrophic nature of ciliates. The morphologically similar species Radiosperma corbiferum has a comparable composition, suggesting a similar ciliate affinity and indicating the utility of micro-FTIR in understanding acritarch affinity. Hexasterias problematica typically occurs in coastal waters from temperate to arctic regions. Halodinium verrucatum sp. nov. is observed in temperate estuarine sediments in the northern hemisphere.