apusomonadida apusomonadida the apusomonads (order apusomonadida) are a group of protozoan zooflagellates that glide on surfaces, and mostly consume prokaryotes. they are of particular evolutionary interest because they appear to be the sister group to the opisthokonts, the clade that includes both animals and fungi. together with the breviatea, these form the obazoa clade. apusomonadida podomonas kaiyoae sem image scientific classification domain: eukaryota clade: amorphea clade: obazoa order: apusomonadidakarpov & mylnikov, 1989 genera "amastigomonas" apusomonas catacumbia cavaliersmithia chelonemonas karpovia manchomonas multimonas podomonas singekia thecamonas diversity 28 species characteristics and morphology apusomonads are small gliding heterotrophic biflagellates (= with two flagella) that possess a proboscis, formed partly or entirely by the anterior flagellum surrounded by a membranous sleeve. there is a pellicle under the dorsal cell membrane that extends into the proboscis sleeve and into a skirt that covers the sides of the cell. apusomonads present two different cell plans: derived cell plan, represented by apusomonas, with a round cell body and a mastigophore, a projection of the cell containing both basal bodies at its end. "amastigomonas-like" cell plan, with an oval or oblong cell that generally forms pseudopodia from the ventral surface, with no mastigophore, and the proboscis comprising solely the flagellum and the sleeve. these characteristics are considered 'primitive' or 'ancestral' in comparison with apusomonas. organisms with this body plan, although historically assigned to the same genus amastigomonas, are a paraphyletic group from which apusomonas has evolved. evolutionary relationships external relationships and importance the apusomonads are the sister group to opisthokonta, the lineage that includes animals, fungi and an array of related protists. because of this, apusomonads occupy an important phylogenetic position to understand eukaryotic evolution. they retain ancestral characteristics, such as the biflagellate body plan, which in opisthokonts evolves into a uniflagellate plan. apusomonads are vital to understanding multicellularity. genes involved in multicellularity have been found in the apusomonad thecamonas, such as adhesion proteins, calcium-signaling genes and types of sodium channels characteristic of animals. the genome of the strain "amastigomonas sp." presents the integrin-mediated adhesion machinery, the primary cell-matrix adhesion mechanism seen in metazoa (animals). amorphea amoebozoa obazoa breviatea apusomonadida opisthokonta holozoa ichthyosporea pluriformea tunicaraptor filozoa filasterea choanozoa choanoflagellata metazoa holomycota fungi nucleariae internal relationships apusomonads are a poorly and narrowly studied group. currently, the diversity of described apusomonads consists of the round apusomonas and a wide array of "amastigomonas-type" organisms that have been reclassified into the genera thecamonas, manchomonas, podomonas, multimonas, chelonemonas and, most recently, catacumbia, cavaliersmithia, karpovia, mylnikovia and singekia. the relationships between these genera are depicted by the cladogram below. apusomonadida manchomonas apusomonas karpovia singekia chelonemonas thecamonas cavaliersmithia catacumbia mylnikovia multimonas podomonas classification the current classification of apusomonadida does not utilize the rank of family to divide the different genera. however, the group itself is an order-level taxon, and is sometimes included in the monotypic class thecomonadea. there are 10 recognized genera, as well as the "amastigomonas-like" archetype that includes primitive forms not yet transferred to new genera. "amastigomonas" de saedeleer 1931 a. caudata mylnikov 1989 a. debruynei de saedeleer 1931 a. marisrubri mylnikov & mylnikov 2012 apusomonas alexeieff 1924 a. australiensis ekelund & patterson 1997 a. proboscidea alexeieff 1924 catacumbia torruella, galindo et al. 2022 c. lutetiensis torruella, galindo et al. 2022 cavaliersmithia torruella, galindo et al. 2022 c. chaoae torruella, galindo et al. 2022 karpovia torruella, galindo et al. 2022 k. croatica torruella, galindo et al. 2022 manchomonas cavalier-smith 2010 manchomonas bermudensis (molina & nerad 1991) cavalier-smith 2010 multimonas cavalier-smith 2010 m. koreensis heiss et al. 2015 m. marina (mylnikov 1989) cavalier-smith 2010 m. media cavalier-smith 2010 mylnikovia torruella, galindo et al. 2022 m. oxoniensis (cavalier-smith 2010) torruella, galindo et al. 2022 podomonas cavalier-smith 2010 p. capensis cavalier-smith 2010 p. gigantea (mylnikov 1999) p. griebenis (mylnikov 1999) p. kaiyoae yabuki in yabuki, tame & mizuno 2022 p. klosteris (arndt & mylnikov 1999) cavalier-smith 2010 p. magna cavalier-smith 2010 singekia torruella, galindo et al. 2022 s. franciliensis torruella, galindo et al. 2022 s. montserratensis torruella, galindo et al. 2022 thecamonadinae larsen & patterson 1990 chelonemonas heiss et al. 2015 c. dolani torruella, galindo et al. 2022 c. geobuk heiss et al. 2015 c. masanensis heiss et al. 2015 thecamonas larsen & patterson 1990 t. filosa larsen & patterson 1990 t. muscula (mylnikov 1999) cavalier-smith 2010 t. mutabilis (griessmann 1913) larsen & patterson 1990 t. trahens larsen & patterson 1990