''Microheliella'' () is a monotypic genus of

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s containing the sole species ''M. maris'', first described in 2012. It has a variety of unusual morphological characteristics which make its broader classification difficult. These include a

centrosome In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progre ...

with two concentric granular shells and

axopodia A pseudopod or pseudopodium (: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and ...

much simpler in structure than in visually similar protists (other '

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

').

Etymology

The generic name ''Microheliella'', as well as the names of the family Microheliellidae and order Microhelida, derive , referring to the small cell size and the authors' wishes to retain the original informal name 'microheliozoan' given to this organism prior to its formal description. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''maris'' refers to seawater, its natural habitat.

Taxonomy

The genus ''Microheliella'' was described from an organism discovered contaminating a

culture Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...

of the amoeba ''

Cochliopodium ''Cochliopodium'' is a Himatismenida genus. It has been found in eyewash stations. It includes: * ''C. actinophorum'' (Auerbach 1856) Page 1976 * ?''C. ambiguum'' Penard 1904 * ''C. arabianum'' Tekle, Gorfu & Anderson 2015 * ''C. barki'' Kudrya ...

'' from the Ebro Delta,

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

, collected in 2003 by Alexey Smirnov. This organism was subsequently transferred into a pure culture through serial dilution and maintained at

Oxford Oxford () is a City status in the United Kingdom, cathedral city and non-metropolitan district in Oxfordshire, England, of which it is the county town. The city is home to the University of Oxford, the List of oldest universities in continuou ...

for nine years in a

growth medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differe ...

of 50% artificial seawater, with naturally occurring bacteria as its food. Initially it was given the informal name 'marine microheliozoan', and a phylogenetic analysis using 18S and 28S rRNA sequences placed it close to

centrohelid The centrohelids or centroheliozoa are a large group of heliozoan protists. They include both mobile and sessile forms, found in freshwater and marine environments, especially at some depth. Characteristics Individuals are unicellular and spher ...

s. Later, the same organism was examined under

electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

and its

Hsp90 Hsp90 (heat shock protein 90) is a chaperone (protein), chaperone protein that assists other proteins to protein folding, fold properly, stabilizes proteins against heat stress, and aids in protein degradation. It also stabilizes a number of ...

gene was sequenced. Combining the newly obtained morphological and genetic data, it was formally described by

Thomas Cavalier-Smith Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford. His research has led to discov ...

and Ema E. Chao in 2012 as the novel species ''Microheliella maris''. Its

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

culture, CCAP 1945/1, is kept in the Culture Collection of Algae and Protozoa at

Oban Oban ( ; meaning ''The Little Bay'') is a resort town within the Argyll and Bute council area of Scotland. Despite its small size, it is the largest town between Helensburgh and Fort William, Highland, Fort William. During the tourist seaso ...

, in Scotland. To accommodate this genus, the monotypic family Microheliellidae and order Microhelida were created, and classified as part of the phylum

Cryptista Cryptista is a clade of alga-like eukaryotes. It is most likely related to Archaeplastida which includes plants and many algae, within the larger group Diaphoretickes. Other characteristic features of cryptophyte mtDNAs include large syntenic ...

in accordance to phylogenetic analyses. Later, phylogenomic analyses demonstrated its position as the sister clade to all Cryptista, in a clade known as

Pancryptista Pancryptista is a clade that includes the Cryptista as well as the ''Microheliella''. Phylogenomic analyses from 2022 suggest the ''Microheliella'' is sister to the Cryptista, forming the clade called Pancryptista, which would be sister to the ...

Evolution

Recent phylogenomic analyses suggest the microhelida are sister to the

, forming a clade called

, which would be sister to the

Archaeplastida The Archaeplastida (or kingdom Plantae '' sensu lato'' "in a broad sense"; pronounced ) are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group glaucophytes. It als ...

. A 2025 paper recovered ''Microheliella'' as a member of Endohelia.

References

{{Taxonbar, from1=Q25369568, from2=Q64895907, from3=Q92029245, from4=Q24048474 Cryptista genera