Abstract
ABSTRACT Many dinoflagellate groups have been overlooked because of their small size compared with their larger counterparts; consequently, little is known about their diversity, distribution, and contribution to the planktonic community. Ansanella is a recently described genus of small marine planktonic dinoflagellates belonging to the order Suessiales. In this study, morphological observations together with molecular SSU and LSU rDNA analyses of clonal strains from the Catalan coast (NW Mediterranean Sea) allowed the identification of A. cf. natalensis and a newly reported species, Ansanella catalana. The cells of A. catalana are oval and 9.6–15.5 μm long; the cell surface is covered with amphiesmal vesicles arranged in 10–13 latitudinal rows; the episome has an apical furrow complex with a single elongated apical vesicle; a type E eyespot is also present. This newly identified species can be distinguished from congeneric species by morphological details of the cell surface, the presence of mucocysts and an extrusome type not previously reported in dinoflagellates. The characterization of this structure could provide insights into extrusome evolution in dinoflagellates. Metabarcoding analysis of plankton and sediment samples from the Catalan coast revealed a wide distribution of Ansanella and the remarkable contribution of this genus to the dinoflagellate communities from three different coastal habitats. Highlights Members of Ansanella genus are widespread along the Catalan coast. A new species of the genus Ansanella (Dinophyceae) is described. A new type of extrusome was observed.
Highlights
Dinoflagellates are a diverse group of protists differing from one another in several of their morphological fea tures, such as their tabulation and the types of their internal organelles, including extrusomes and eyespots
The strains closely related to A. natalensis were examined under light microscopy and their morphology agreed with that described in previous studies of the species, including the cell size and number of pyrenoids (Dawut et al, 2018), and with the species referred to in this work as A. cf. natalensis
Ansanella catalana shows the typical characters of the Suessiaceae family: a type E eyespot, an apical structure formed by an elongated apical vesicle (EAV), and amphiesmal vesicles (AVs) organized in > 7 latitudinal rows (Moestrup et al, 2009b)
Summary
Dinoflagellates are a diverse group of protists differing from one another in several of their morphological fea tures, such as their tabulation and the types of their internal organelles, including extrusomes and eyespots. ~2500 species of dinoflagellates have been described to date (Hoppenrath et al, 2009; Gómez, 2012), the true species diversity is difficult to estimate (Hoppenrath, 2017). Dinoflagellates are still largely identified based on light microscopy observations, but this method is not suffi cient to achieve species discrimination within some groups. This is the case for the smallest spe cies (< 20 μm), especially those that are delicate, naked, or thin-walled, which are often overlooked. The massive sequencing of environmental samples con ducted during the last two decades around the world has clearly shown that the richness of dinoflagellates has been considerably underestimated, with the largest deficits occurring for species < 20 μm in size
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