Vampyrellida

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). 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.