| Microheliella | |
|---|---|
 | |
| Differential interference contrast image of a living cell ofM. maris showing axopodia (arrows), tinyvacuole (V) andcentrosome (C). Scale bar: 10 μm. | |
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | CAM |
| Clade: | Pancryptista |
| Order: | Microhelida Cavalier-Smith 2012 |
| Family: | Microheliellidae Cavalier-Smith & Chao 2012 |
| Genus: | Microheliella Cavalier-Smith & Chao 2012 |
| Species: | M. maris |
| Binomial name | |
| Microheliella maris Cavalier-Smith & Chao 2012 | |
Microheliella (from Greek micro 'small' and helios 'sun') is a monotypic genus ofprotists containing the sole speciesM. maris, first described in 2012. It has a variety of unusual morphological characteristics which make its broader classification difficult. These include acentrosome with two concentric granular shells andaxopodia much simpler in structure than in visually similar protists (other 'heliozoa').[1]
Thegeneric nameMicroheliella, as well as the names of the family Microheliellidae and order Microhelida, derive from Greek micro 'small' and helios 'sun', 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. Thespecific epithetmaris refers to seawater, its natural habitat.[1]
The genusMicroheliella was described from an organism discovered contaminating aculture of the amoebaCochliopodium from theEbro Delta,Spain, collected in 2003 by Alexey Smirnov. This organism was subsequently transferred into a pure culture throughserial dilution and maintained atOxford for nine years in agrowth medium of 50% artificial seawater, with naturally occurring bacteria as its food. Initially it was given the informal name 'marine microheliozoan', and a phylogenetic analysis using18S and28S rRNA sequences placed it close tocentrohelids.[2] Later, the same organism was examined underelectron microscopy and itsHsp90 gene was sequenced. Combining the newly obtained morphological and genetic data, it was formally described byThomas Cavalier-Smith and Ema E. Chao in 2012 as the novel speciesMicroheliella maris. Itstype culture, CCAP 1945/1, is kept in the Culture Collection of Algae and Protozoa atOban, in Scotland.[1]
To accommodate this genus, the monotypic family Microheliellidae and order Microhelida were created, and classified as part of the phylumCryptista in accordance to phylogenetic analyses.[1] Later, phylogenomic analyses demonstrated its position as the sister clade to all Cryptista, in a clade known asPancryptista.[3]
Recentphylogenomic analyses suggest the microhelida are sister to theCryptista, forming a clade calledPancryptista, which would be sister to theArchaeplastida.[4][3]