The axodines are a group of unicellular

stramenopiles The stramenopiles, also called heterokonts, are Protist, protists distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular sur ...

that includes silicoflagellate and rhizochromulinid algae, actinomonad heterotrophic flagellates and actinophryid heliozoa. Alternative classifications treat the dictyochophytes as

heterokont The stramenopiles, also called heterokonts, are protists distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, an ...

algae, or as

Chrysophyceae The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae, or golden algae, are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, '' Prymnesium parvum'', wh ...

. Other overlapping taxonomic concepts include the Actinochrysophyceae, Actinochrysea or Dictyochophyceae ''sensu lato''. The grouping was proposed on the basis of ultrastructural similarities, and is consistent with subsequent molecular comparisons. The Axodine grouping was unusual in breaking with the traditions of botanical and protozoological taxonomy to include the actinophryid heliozoa as part of the lineage that also contained the

pedinellid Pedinellales ( ICN) or Pedinellida (ICZN) is a group of single-celled algae found in both marine environments and freshwater. These are found in both freshwater and marine environments, and most genera are sessile, attached by posterior stalks. ...

algae along with colorless relatives such as ''Actinomonas'', Pteridomonas, and ''Ciliophrys''; the axodines further included the

silicoflagellate The silicoflagellates (order Dictyochales) are a small group of unicellular photosynthetic protists, or algae, belonging to the supergroup of eukaryotes known as Stramenopiles. They behave as plankton and are present in oceanic waters. They a ...

s, and

Rhizochromulinales Rhizochromulinales is an order of Dictyochophyceae. The order includes the genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and f ...

. This followed a growing consensus that the actinophryid heliozoa were not related to other types of heliozoa.Smith, R. McK. & Patterson, D. J. 1986. Analyses of heliozoan inter-relationships: an example of the potentials and limitations of the ultrastructural approaches to the study of protistan phylogeny. Proc. R. Soc. Lond. 227:325 - 366.

Characteristics

The name points to a character that is deemed to be synapomorphic for the group: that is the microtubular arrays that extend from the surface of the

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 Nucleu ...

. Many flagellated forms have a single emergent flagellum, that lacks the root structure found in related chrysophytes. The silicoflagellate Dictyocha fibula.png, Siliceous skeleton of the dictyochid flagellate, ''Dictyocha fibula'' Actinophrys sol (phase contrast microscopy).jpg, ''Actinophrys sol'', living heliozoon Actinomonas mirabilis, flagellate.jpg, ''Actinomonas'' - heterotrophic flagellate with single flagellum and stiff arms Ciliophrys DIC.jpg, ''Ciliophrys infusionum'', living flagellate

Classification and history

The traditional botanical treatment of the group follows

Order Dictyochales

The most notable group is the

s, marine plankton that form siliceous skeletons and are well known as fossils.

Order Pedinellales

Most other axodines form a group variously called the pedinellids.

Order Rhizochromulinales

In addition to the silicoflagellates and actinodines, the marine amoeboid '' Rhizochromulina marina'' is included here based on the structure of its

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s. It is considered closer to the latter group than the former.

References

{{Taxonbar, from=Q21445632 Actinochrysophyceae Planktology