Culture Strains of a Chlorarachniophyte, Lotharella globosa

The chlorarachniophytes are a small group of exclusively marine

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

e widely distributed in tropical and temperate waters. They are typically

mixotrophic A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comp ...

, ingesting

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and smaller

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

s as well as conducting

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. Normally they have the form of small

amoeba An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by extending and ret ...

e, with branching cytoplasmic extensions that capture prey and connect the cells together, forming a net. They may also form

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 ...

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, which characteristically have a single subapical flagellum that spirals backwards around the cell body, and walled coccoid cells. The

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s were presumably acquired by ingesting some

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

. They are surrounded by four membranes, the outermost of which is continuous with the

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

, and contain a small

nucleomorph Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. They are thought to be vestiges of primitive red and green algal nuclei that were engulfed by a larger eukaryote. Becaus ...

between the middle two, which is a remnant of the alga's nucleus. This contains a small amount of DNA and divides without forming a

mitotic In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

spindle. The origin of the chloroplasts from green algae is supported by their pigmentation, which includes

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

s ''a'' and ''b'', and by genetic similarities. The only other group of algae that contain nucleomorphs are the

cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterio ...

s, but their chloroplasts seem to be derived from a

red alga Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

. The chlorarachniophytes only include five genera, which show some variation in their life-cycles and may lack one or two of the stages described above. 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 diverse group of amoeboid and amoeboid-like protozoa. The chlorarachniophytes were placed before in the order Rhizochloridales, class

Xanthophyceae Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of heterokont algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamento ...

(e.g., Smith, 1938), as algae, or in order Rhizochloridea, class Xanthomonadina (e.g., Deflandre, 1956), as protozoa. So far sexual reproduction has only been reported in two species; Chlorarachnion reptans and Cryptochlora perforans.

Phylogeny

Based on the work of Hirakawa et al. 2011.

Taxonomy

* Class Chlorarachniophyceae Hibberd & Norris 1984 hlorarachnea Cavalier-Smith 1998; Chlorarachniophyta Hibberd & Norris 1984; Chlorarachnia Cavalier-Smith 1993** Order Minorisida Cavalier-Smith 2017 *** Family Minorisidae Cavalier-Smith 2017 **** Genus '' Minorisa'' Del Campo 2013 ***** Species '' Minorisa minuta'' Del Campo 2013 ** Order Chlorarachniales Ishida & Hara 1996 hlorarachniida Hibberd & Norris 1984*** Family Chlorarachniaceae (Pascher 1939) Ishida & Hara 1996 **** Genus '' Amorphochlora'' Ishida, Yabuki & Ota 2011 ***** Species '' Amorphochlora amoebiformis'' (Ishida & Hara 1996) Ishida, Yabuki & Ota 2011 'Lotharella amoeboformis'' Ishida & Hara 1996**** Genus '' Bigelowiella'' Moestrup 2001 ***** Species '' B. longifila'' Shuhei, Kunihiko & Kenichiro 2007 ***** Species '' B. natans'' Moestrup 2001 **** Genus ''

Chlorarachnion The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally the ...

'' Geitler 1930 ***** Species ''

Chlorarachnion reptans The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally the ...

'' Geitler 1930 **** Genus '' Cryptochlora'' Calderon-Saenz & Schnetter 1987 ***** Species '' Cryptochlora perforans'' Calderon-Saenz & Schnetter 1987 **** Genus '' Gymnochlora'' Ishida, Nakayama & Hara 1996 ***** Species '' G. dimorpha'' Ota 2011 ***** Species '' G. stellata'' Ishida, Nakayama & Hara 1996 **** Genus ''

Lotharella The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally the ...

'' Ishida & Hara 1996 ***** Species '' L. scrobicolata'' Ishida & Hara ***** Species '' L. polymorpha'' Dietz et al. 2003 ***** Species '' L. vacuolata'' Ota & Ishida 2005 ***** Species '' L. oceanica'' Ota 2009 ***** Species '' L. reticulosa'' Ohta 2012 ***** Species '' L. globosa'' (Ishida & Hara 1994) Ishida & Hara 1996 'Chlorarachnion globosum'' Ishida & Hara 1994**** Genus '' Norrisiella'' Ota, Ueda & Ishida 2007 ***** Species '' Norrisiella sphaerica'' Ota, Ueda & Ishida 2007 **** Genus '' Partenskyella'' Ota et al. 2009 ***** Species '' Partenskyella glossopodia'' Ota et al. 2009 File:Chlorarachniophyte, Lotharella globosa, extending a filopodium.png, ''Lotharella globosa'' extending a

filopodium 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 ...

(Fp) through a pore of the cell wall (CW) from a walled amoeboid cell. Py: pyrenoid.
Scale bar = 10µm File:Binary and quaternary cell divisions of a chlorarachniophyte, Lotharella globosa.png, Binary and quaternary cell divisions of ''Lotharella globosa''. Arrowheads indicate the parental cell wall.
Scale bar = 10µm File:Flagellate cell of a chlorarachniophyte, Lotharella globosa, with a single flagellum and plastid.png, Flagellate cell of ''Lotharella globosa'' with a single flagellum (Fl) and plastid (P)
Scale bar = 10µm

References

External links

AlgaeBase: ChlorarachniophytaTree of Life: Chlorarachniophyta
{{Taxonbar, from=Q136146 Filosa Algal taxonomy