Anisonemia is a clade of single-celled belonging to the phylum Euglenozoa, relatives of the Euglenophyceae algae. They are , with two flagella for locomotion. Anisonemia includes various species and a group of primary protists known as Aphagea.
Description
Members of Anisonemia are unicellular
,
that have
flagella for movement. Species of this lineage have two flagella arising from the anterior region of the cell, unlike their relatives,
Peranemida and
Euglenophyceae, where only one flagellum is emmergent. They move through a
gliding motion, where the posterior flagellum is fully in contact with the substrate and the anterior flagellum beats through its whole length in front of the cell, carrying it forward.
Evolution
Anisonemia is a
monophyletic group, or
clade, of
that contains several
species and a clade that has evolved toward primary
osmotrophy, named
Aphagea. Anisonemia belongs to the
Euglenida, a diverse group of flagellates that also contains the
Euglenophyceae.
Together with other flagellates, they compose the phylum
Euglenozoa.
In particular, Anisonemia, Euglenophyceae and the phagotrophic Peranemida form a
clade known as
Spirocuta, distinguished by a greater number of pellicle strips than other euglenids. These strips allow the cells to actively deform their shape, a unique characteristic known as
metaboly.
The following cladogram depicts the evolutionary relationships of Anisonemia:
Classification
Anisonemia was first described by American protozoologist Thomas Cavalier-Smith in 2016, on the basis of
phylogenetic analysis. He proposed it as a subclass of the obsolete class Peranemea, which is
paraphyletic with respect to
Euglenophyceae, containing
Peranemida in addition to Anisonemia. To date, it is the most diverse
clade within
Spirocuta. It contains two orders, differentiated by their modes of locomotion:
Anisonemida,
that perform a
gliding motion with their anterior flagellum, and
Natomonadida, which move by swimming. In turn, Natomonadida comprises two suborders: the phagotrophic
Metanemina and the completely
osmotrophic Rhabdomonadina,
better known as Aphagea.
Later revisions to the classification of
ignored this taxon,
until phylogenetic studies of the 2020s supported its
monophyly. In some studies, it is referred to as Anisonemea.
The composition of Anisonemia is the following:
