glissomonadida glissomonadida the glissomonads are a group of bacterivorous gliding flagellated protists that compose the order glissomonadida, in the amoeboflagellate phylum cercozoa. they comprise a vast, largely undescribed diversity of soil and freshwater organisms. they are the sister group to cercomonads; the two orders form a solid clade of gliding soil-dwelling flagellates called pediglissa. glissomonadida the glissomonad orciraptor agilis attacking an actinotaenium cell. scientific classification domain: eukaryota clade: diaphoretickes clade: sar phylum: cercozoa class: sarcomonadea subclass: pediglissa order: glissomonadidahowe, bass, vickerman, chao & cavalier-smith, 2009 emend. hess & melkonian, 2013 suborders & families allapsina allapsidae sandonina bodomorphidae dujardinidae proleptomonadidae sandonidae pansomonadina acinetactidae agitatidae aurigamonadidae viridiraptoridae incertae sedis: saccharomycomorphidae morphology external appearance glissomonads are zooflagellates that aren't strongly amoeboid, and are only covered by a plasma membrane. their common ancestor is thought to be a biflagellate, with a short anterior flagellum and a long posterior flagellum, that glided on the substrate by moving their posterior flagellum. in gliding descendants, the cell's posterior zone is usually rounded, giving the cell an ovoid shape. some species may temporarily extend a protoplasmic tail, that unlike most cercomonads doesn't trail along the posterior flagellum. at least two genera, orciraptor and viridiraptor, are capable of transforming into a distinctly amoeboid state attached to the surface. the group also includes descendants that have lost their gliding, mainly proleptomonas. this genus has another exception to the group: an anterior flagellum that is longer than the posterior, while the posterior is adherent to the cell and not used for gliding. internal structure most species lack obvious morphological specializations: there is no cytopharynx, deep flagellar groove, or pocket evident. apart from proleptomonas, which is exceptionally elongated and has a modified cytoskeleton, the nucleus is usually anterior and attached to the kinetid (= flagellar apparatus) through well-developed fibrous roots. there are typically two posterior and one anterior microtubular centriolar roots. a contractile vacuole is usually seen in the cell's posterior area. the mitochondria have tubular cristae. there is a microbody attached to the posterior side of the nucleus, except in proleptomonas. the golgi apparatus is usually seen associated with the nucleus, which doesn't happen in all cercozoans. both flagella have the same thickness and are simple, without a paraxonemal rod, hairs or scales, sometimes acronematic (= with an acroneme). unlike in cercomonads, the ciliary transition zone has a dense transverse plate at the distal end. the anterior flagellum beats like a cilium towards the left, as seen in cercomonads, and is sometimes reduced to a short stub without an axoneme. ecology and behavior glissomonads are heterotrophic aerobic organisms that almost exclusively inhabit soil or freshwater, where they feed on bacteria. sexual reproduction is unknown. cysts are present in the group, and have smooth walls. phylogeny the cladogram below depicts the evolutionary relationships between most of the glissomonad families: glissomonadida sandonidae dujardinidae bodomorphidae saccharomycomorphidae proleptomonadidae clade z clade u allapsidae group te viridiraptoridae clade y cercomonadida classification the current classification is: family saccharomycomorphidae feng, he, jiang, zhang & yu, 2021 suborder allapsina cavalier-smith, 2018 family allapsidae howe, bass, vickerman, chao & cavalier-smith, 2009 allapsa howe, bass, vickerman, chao & cavalier-smith, 2009 allantion sandon, 1924 teretomonas howe, bass, vickerman, chao & cavalier-smith, 2009 suborder sandonina cavalier-smith, 2018 family dujardinidae cavalier-smith & howe, 2011 dujardina cavalier-smith & howe, 2011 family bodomorphidae hollande, 1952 bodomorpha hollande, 1942 family sandonidae howe, bass, vickerman, chao & cavalier-smith, 2009 flectomonas howe, bass, vickerman, chao & cavalier-smith, 2009 mollimonas howe & cavalier-smith, 2011 neoheteromita howe, bass, vickerman, chao & cavalier-smith, 2009 sandona howe, bass, vickerman, chao & cavalier-smith, 2009 family proleptomonadidae howe, bass, vickerman, chao & cavalier-smith, 2009 proleptomonas woodcock, 1916 suborder pansomonadina vickerman, 2005 stat. nov. cavalier-smith, 2018 family viridiraptoridae hess & melkonian, 2013 viridiraptor hess & melkonian, 2013 orciraptor hess & melkonian, 2013 family agitatidae cavalier-smith & bass, 2009 agitata cavalier-smith & bass, 2009 family acinetactidae stokes, 1886 acinetactis stokes, 1886 family aurigamonadidae cavalier-smith, 2011 aurigamonas vickerman, 2005