Morphological and Phylogenetic Characterisation of Prorocentrum spinulentum, sp. nov. (Prorocentrales, Dinophyceae), a Small Spiny Species from the North Atlantic

Abstract

Prorocentrum comprises dinophytes with several unique traits, including the presence of two large thecal plates and apical insertion of flagella. Species delimitation for many small and similar planktonic species is challenging, as SEM analyses and DNA sequence information of type material are rarely available. Based on a strain from the North Atlantic Prorocentrum spinulentum, sp. nov. is described here. Cells were small (9.0–12.8 µm long, 8.5–11.9 µm deep), oval to almost round in lateral view and moderately compressed. The ovoid nucleus was in median or slightly sub-median position on the cells ventral side. The plate surface appeared spiny in light microscopy with thecal pores visible in empty thecae. Electron microscopy revealed plates densely covered by relatively long spines and two size classes of thecal pores. The periflagellar area consisted of 8 platelets, and there was a prominent wing (ca. 1 µm wide and long) on platelet 1. The new species is distinct in DNA trees and embedded in the Prorocentrum shikokuense species group. It differs from the protologues of other small species of Prorocentrum by the unique combination of cell size and shape, the presence of long spines on the thecal plate surface and scattered thecal pores. The thorough morphological description of this species, representing a previously uncharacterised lineage within Prorocentrum, increases and improves our knowledge of the diversity within this important group of planktonic organisms.

Discovery of Prevalent Ciliophora, Discoba, and Copepoda Protists in Deep Sea Water by In Situ Nucleotide Extraction

“…The Prorocentrum species are known as dinoflagellates that can produce toxins in coastal zones [41]. Prorocentrum spinulentum protists are tiny (9-12 um) and oval in shape [42]. As far as we know, they have not been reported in the deep ocean yet.…”

Mucus-Trap-Assisted Feeding Is a Common Strategy of the Small Mixoplanktonic Prorocentrum pervagatum and P. cordatum (Prorocentrales, Dinophyceae)

“…Several new species within this group have also been recently described, including P. pervagatum Tillmann, Hoppenrath and Gottschling (=P. criophilum Gourvil and Gutiérrez-Rodríguez) [12], P. spinulentum Tillmann, Gottschling and Hoppenrath [10], and P. thermophilum F. Gómez, Tangcheng Li, Hu. Zhang & Senje Lin [13].…”

“…The species P. cf. balticum form a distinct clade in rRNA sequence phylogenies which is embedded within a larger cluster of several small planktonic Prorocentrum [ 9 , 10 ]. This cluster of species include P. cordatum and taxa of the P. shikokuense group [ 10 , 11 ], which are both widely distributed and can be numerically abundant.…”

“…balticum form a distinct clade in rRNA sequence phylogenies which is embedded within a larger cluster of several small planktonic Prorocentrum [ 9 , 10 ]. This cluster of species include P. cordatum and taxa of the P. shikokuense group [ 10 , 11 ], which are both widely distributed and can be numerically abundant. Several new species within this group have also been recently described, including P. pervagatum Tillmann, Hoppenrath and Gottschling (= P. criophilum Gourvil and Gutiérrez-Rodríguez) [ 12 ], P. spinulentum Tillmann, Gottschling and Hoppenrath [ 10 ], and P. thermophilum F. Gómez, Tangcheng Li, Hu.…”

“…This cluster of species include P. cordatum and taxa of the P. shikokuense group [ 10 , 11 ], which are both widely distributed and can be numerically abundant. Several new species within this group have also been recently described, including P. pervagatum Tillmann, Hoppenrath and Gottschling (= P. criophilum Gourvil and Gutiérrez-Rodríguez) [ 12 ], P. spinulentum Tillmann, Gottschling and Hoppenrath [ 10 ], and P. thermophilum F. Gómez, Tangcheng Li, Hu. Zhang & Senje Lin [ 13 ].…”