TY - JOUR

T1 - The Long-time Orphan Protist Meringosphaera mediterranea Lohmann, 1902 [1903] is a Centrohelid Heliozoan

AU - Zlatogursky, Vasily V

AU - Shɨshkin, Yegor

AU - Drachko, Daria

AU - Burki, Fabien

N1 - Publisher Copyright: © 2021 International Society of Protistologists.

PY - 2021/9

Y1 - 2021/9

N2 - Meringosphaera is an enigmatic marine protist without clear phylogenetic affiliation, but it has long been suggested to be a chrysophytes-related autotroph. Microscopy-based reports indicate that it has a worldwide distribution, but no sequence data exists so far. We obtained the first 18S rDNA sequence for M. mediterranea (identified using light and electron microscopy) from the west coast of Sweden. Observations of living cells revealed granulated axopodia and up to 6 globular photosynthesizing bodies about 2 μm in diameter, the nature of which requires further investigation. The ultrastructure of barbed undulating spine-scales and patternless plate-scales with a central thickening is in agreement with previous reports. Molecular phylogenetic analysis placed M. mediterranea inside the NC5 environmental clade of Centroplasthelida (Haptista) along with additional environmental sequences, together closely related to Choanocystidae. This placement is supported by similar scales in Meringosphaera and Choanocystidae. We searched the Tara Oceans 18S-V9 metabarcoding dataset which revealed four OTUs with 94.8-98.2% similarity, with oceanic distribution similar to that based on morphological observations. The current taxonomic position and species composition of the genus are discussed. The planktonic lifestyle of M. mediterranea contradicts the view of some authors that centrohelids enter the plankton only temporarily.

AB - Meringosphaera is an enigmatic marine protist without clear phylogenetic affiliation, but it has long been suggested to be a chrysophytes-related autotroph. Microscopy-based reports indicate that it has a worldwide distribution, but no sequence data exists so far. We obtained the first 18S rDNA sequence for M. mediterranea (identified using light and electron microscopy) from the west coast of Sweden. Observations of living cells revealed granulated axopodia and up to 6 globular photosynthesizing bodies about 2 μm in diameter, the nature of which requires further investigation. The ultrastructure of barbed undulating spine-scales and patternless plate-scales with a central thickening is in agreement with previous reports. Molecular phylogenetic analysis placed M. mediterranea inside the NC5 environmental clade of Centroplasthelida (Haptista) along with additional environmental sequences, together closely related to Choanocystidae. This placement is supported by similar scales in Meringosphaera and Choanocystidae. We searched the Tara Oceans 18S-V9 metabarcoding dataset which revealed four OTUs with 94.8-98.2% similarity, with oceanic distribution similar to that based on morphological observations. The current taxonomic position and species composition of the genus are discussed. The planktonic lifestyle of M. mediterranea contradicts the view of some authors that centrohelids enter the plankton only temporarily.

KW - centrohelids

KW - external skeleton

KW - heliozoa

KW - protists

KW - systematics

KW - ultrastructure

KW - Aquatic Organisms/classification

KW - Sweden

KW - Phylogeny

KW - Microscopy, Electron

KW - Eukaryota/classification

KW - RNA, Ribosomal, 18S/genetics

KW - SPECIES COMPOSITION

KW - NANOPLANKTON

KW - PACIFIC

KW - CLASSIFICATION

KW - SP. NOV.

KW - EMPHASIS

KW - SCALE-BEARING

KW - DIVERSITY

KW - COASTAL WATERS

KW - PHYTOPLANKTON

UR - https://www.mendeley.com/catalogue/9c750b38-33f1-31ff-9c8f-6bb9ff151e15/

UR - http://www.scopus.com/inward/record.url?scp=85109598171&partnerID=8YFLogxK

U2 - 10.1111/jeu.12860

DO - 10.1111/jeu.12860

M3 - Article

C2 - 34048133

VL - 68

SP - e12860

JO - Journal of Eukaryotic Microbiology

JF - Journal of Eukaryotic Microbiology

SN - 1066-5234

IS - 5

M1 - e12860

ER -