Aconchulinida

The vampyrellids (order Vampyrellida, class Vampyrellidea), colloquially known as vampire amoebae, are a group of free-living predatory amoebae classified as part of the lineage Endomyxa. They are distinguished from other groups of amoebae by their irregular cell shape with propensity to fuse and split like plasmodial organisms, and their life cycle with a digestive cyst stage that digests the gathered food. They appear worldwide in marine, brackish, freshwater and soil habitats. They are important predators of an enormous variety of microscopic organisms, from algae to fungi and animals. They are also known as aconchulinid amoebae (order Aconchulinida).

==Cell morphology and movement== Vampyrellids are traditionally considered filose amoebae, i.e. they generate slender pseudopodia (filopodia). They are naked, devoid of external structures such as scales, cell coats or a glycocalyx, although there may be a temporary mucilage coat in the trophozoite stage. The trophozoites vary greatly in shape, size and color between species, but can be grouped into three cell states or 'morphotypes': isodiametric, expanded, and 'filoflabellate'. Isodiametric (spherical) morphotype, common in algivorous Vampyrella and Lateromyxa, with radiating filopodia. Some species float in the water column, resembling heliozoa in shape. Others crawl on the surface by concentrating stiff filopodia at the anterior region of the cell, attaching them to the surface, retracting and moving them towards the posterior region. Expanded morphotype, the most common, bound to the surface, with a variety of shapes (for example, either fan-shaped or branched in Leptophrys; with large, hyaline lamellae with thread-like filopodia in Sericomyxa; highly branched or reticulate, in Platyreta and Thalassomyxa). Filoflabellate morphotype, only found in Placopus, with flattened elliptical, spherical or fan-shaped cells that exhibit a clear separation between the granuloplasmic cell hump and the hyaloplasmic lamellae, sometimes called 'lamellipodia'. There are numerous filopodia on the ventral side of the cell. Some of these trophozoites resemble amoebozoans such as vannellids, except for the presence of filopodia. They move by rolling over the filopodia that are anchored to the substrate. thumb|center|upright=2.5|The three distinct morphotypes of vampyrellid amoebae ==Life cycle== thumb|Motile cell after feeding (J), early (K) and mature (L) digestive cysts, cyst with daughter cells after internal plasmotomy (M) thumb|Large, bulky Plasmodium (life cycle)|plasmodium of [[Vampyrella lateritia]] thumb|upright=0.8|Vampyrella lateritia resting cyst with four envelopes ===Nutrition stages=== All known vampyrellids are heterotrophic amoebae with a free-living (non-parasitic) life cycle that lacks flagellate stages, except for Lateromyxa gallica, and is characterized by an alternation between mobile and immobile cellular stages: The mobile, amoeboid cells, called 'trophozoites' or 'swarmers' in old literature. Their main activity is to disperse, search and gather food through phagocytosis. The immobile but highly metabolically active 'digestive cyst' stage, that appears after the feeding. In some species it is called a 'resting phase', but it is different from a true resting cyst (or spore) that is metabollically inactive to survive adverse conditions. To reach this stage, the trophozoite retracts its filopodia, secretes a layered cell wall, and strongly attaches itself to the substrate or floats freely. Either a central main vacuole or multiple separate vacuoles appear to digest the food. The cytoplasm color may change to a bright red, orange or yellow color, or remain colorless. When the digestive phase is finished, one or multiple trophozoites hatch from the cyst through holes in the cell wall.