The first arctic strain of Rhizochromulina: Morphology, ultrastructure, and position in the evolutionary tree of the order Rhizochromulinales (Heterokontophyta, Dictyochophyceae)
•The first report of Rhizhochromulina sp. from the Arctic region.•Amoeboid cells of Rhizochromulina sp. B44 form meroplasmodia.•Mechanical stimulation triggers amoeba-to-flagellate transition in Rhizochromulina sp. B44. Rhizochromulina marina is a unicellular amoeboid alga capable of forming flagell...
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Veröffentlicht in: | European journal of protistology 2024-02, Vol.92, p.126050-126050, Article 126050 |
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Sprache: | eng |
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Zusammenfassung: | •The first report of Rhizhochromulina sp. from the Arctic region.•Amoeboid cells of Rhizochromulina sp. B44 form meroplasmodia.•Mechanical stimulation triggers amoeba-to-flagellate transition in Rhizochromulina sp. B44.
Rhizochromulina marina is a unicellular amoeboid alga capable of forming flagellate cells; it is a single validly named species in the genus. Besides, there are numerous environmental sequences and undescribed strains designated as Rhizochromulina sp. or R. marina. The biogeography of the genus is understudied: rhizochromulines from the Indian, Southern, and Arctic Oceans are unknown. Here, we present the description of Rhizochromulina sp. B44, which was for the first time isolated from an arctic habitat. Biofilms of this microalga grow at the bottom of a culture vessel, where neighbouring amoeboid cells form associations through a common network of pseudopodia, i.e. meroplasmodia. Pseudopodia branch, anastomose mainly during meroplasmodia formation, and are supported by microtubules that arise from the perinuclear zone. Actin filaments are localized in the cytoplasm and can be revealed only near the bases of pseudopodia. We succeeded in inducing the transformation of amoeboid cells into flagellates using a prolonged agitation of cultures. Morphological and molecular analyses revealed that the studied strain is most closely related to the type strain of R. marina. At the same time, 18S rDNA sequences of early branching-off rhizochromulinids differ significantly from Rhizochromulina sp. B44, suggesting a high divergence at the genus level. |
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ISSN: | 0932-4739 1618-0429 |
DOI: | 10.1016/j.ejop.2023.126050 |