The Heliomonadida (formerly Dimorphida) are a small group of

heliozoa Heliozoa, commonly known as sun-animalcules, are microbial eukaryotes (protists) with stiff arms ( axopodia) radiating from their spherical bodies, which are responsible for their common name. The axopodia are microtubule-supported projections fro ...

n amoeboids that are unusual in possessing

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

throughout their life cycle.

Classification

Genetic studies place them among the

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

, a group including various other

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

s that form

filose pseudopodia Filopodia (singular filopodium) are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Within the lamellipodium, actin ribs are known as ''microspikes'', and when they extend beyond the lame ...

. This order has recently been placed into the new

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

of naked

filose Filose can refer to a few things: *Filose, describing members of the Filosa subphylum of Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead ...

cercozoan Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major euk ...

s called

Granofilosea Granofilosea is a class of cercozoans in the subphylum Filosa. Three groups that were traditionally considered heliozoans belong here: the Heliomonadida, Desmothoracida and Gymnosphaerida, which were recently grouped into the new class of Gran ...

. There are two genera in this

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

: * ''

Heliomorpha ''Heliomorpha'' is a genus of Cercozoa, placed in its own family, Heliomorphidae. It used to be known as "''Dimorpha''", but that name was a junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differ ...

'', a tiny organism found in freshwater * the larger '' Tetradimorpha'', which is distinguished by having four rather than two flagella.

Morphology

Bundles of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

s, typically in square array, arise from a body near the flagellar bases and support the numerous axopods that project from the cell surface. Dimorphids have a single

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

, and

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

with tubular cristae.

References

{{Taxonbar, from=Q5705752 Granofilosea Cercozoa orders Amoeboids Taxa named by Thomas Cavalier-Smith