The axodines are a group of unicellular

stramenopiles Stramenopile is a clade of organisms 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, and in some they have be ...

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

heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which ...

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'', whic ...

. 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 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. The flagellum is at the ant ...

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

silicoflagellate Dictyochales (Silicoflagellates, or Dictyochophyceae ''sensu stricto'') are a small group of unicellular heterokont algae, found in marine environments. Characteristics In one stage of their life cycle, they produce a siliceous skeleton, compo ...

s, and

Rhizochromulinales Rhizochromulinales is an order of Dictyochophyceae. The order includes the genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biolo ...

. 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 Nucle ...

. 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. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

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

References

{{Taxonbar, from=Q21445632 Actinochrysophyceae Planktology