dcsimg

Description of Cryptomonads

provided by BioPedia
Circumscription: Biflagellated autotrophic, mixotrophic and heterotrophic flagellates, flagella inserting in an anterior groove/channel lines with refractile ejectisomes. Variously coloured photosynthetic compartments, in some taxa at least, formed from secondary symbioses with eukaryotes, the symbiont being located in a membrane-bound compartment and provided with a reduced nucleus (the nucleomorph). Two genera of heterotrophs, one (Goniomonas) possibly primitively so. Ultrastructural identity: Mitochondria cristae flattened, mitochondrion often extensive. Coiled ribbon extrusomes (eiectisomes) associated with flagellar pocket (gullet) and with cell surface. Geometrically positioned plates of fibrous cytoskeletal material underlie the membrane. Plastidic taxa with plastid inside a fold of the nuclear envelope and with nucleomorph where studied. No eyespot. Both flagella with stiff bipartite hairs. Small scales may be attached to cell body. Flagella insert into near parallel basal bodies, usually with multilamellate root structure (rhizostyle) in addition to several microtubular roots. Nuclear division with spindle developing from basal bodies and penetrating the dividing nucleus, the membrane of which completely breaks down. Synapomorphy: Flagellar groove/channel with associated ejectisomes and/or double row of flagellar hairs on both flagella and/or cortical plates.
license
cc-by-nc
author
biopedia
provider
BioPedia
original
visit source
partner site
BioPedia

Algae: Protists with Chloroplasts

provided by EOL authors

The algae are a polyphyletic and paraphyletic group of organisms. They are defined in differing ways, but are usually considered to be the photosynthetic organisms excepting plants. Using the term 'plants' in its most restrictive fashion, the algae are then photosynthetic organisms excepting the sister group to the Charales (i.e. the land plants). Such a definition allows inclusion of photosynthetic prokaryotes such as the cyanobacteria. The definition applied here is that the algae is that artificial subset of the photosynthetic eukaryotes which excludes the sister group to the Charales (land plants).

The algae are the dominating primary producers in aquatic ecosystems, on unstable substrates (muds and sands) and in intertidal marine habitats. Algae are commonly exploited as foodstuffs, food additives, toothpastes, etc.

The ability for eukaryotes to carry out photosynthesis was made possible by one or more symbiotic associations between heterotrophic eukaryotes and photosynthetic prokaryotes (or their descendents). There were several primary symbioses between eukaryotes and blue green algae. In one lineage, the photosynthetic organism lost much of its genetic independence and became functionally and genetically integrated as chloroplasts within the host cell. Modern chloroplasts, also called plastids, are bounded by two or more membranes, and most usually lie free in the cytoplasm, but in some cases they may be located within a fold of the nuclear envelope, or may be associated with the cytoplasm and residual nucleus of a eukaryotic endosybiont. The descendents of some of these primary plastids have gone on to form further associations. At least two types of protists (chloroarachniophytes and cryptomonads) have acquired 'plastids' by forming symbioses with eukaryotic algae. This are referred to as secondary symbioses.

Algae are distinguished on a number of different characteristics. The most important ones are:

  • the colour of the plastids (more correctly the combination of photosynthetic pigments that are present in the plastid)
  • the presence of flagella (and if so how many, how do they insert in the cell and how do they beat)
  • is the cell surrounded by extracellular material? If so, what is that material - organic or inorganic, a continuous wall or a layer of scales)
  • are the cells motile or not?
  • do they occur singly, in colonies, filaments or exhibit differentiation that would allow them to satisfy the criterion of multicellularity?

Algal protists occur in 8 lineages. These are summarised below.

Groups of Algae

ALVEOLATES

Contains some algae, autotrophic dinoflagellates, diverse, Peridinium, Symbiodinium, Ceratium

unicellular, colonial, syncytial; free-living, symbiotic and parasitic

MAJOR PIGMENTS:chlorophylls a and c, some symbionts

CHLORARACHNIOPHYTES

A few genera of amoeboid organisms all with symbiotic algae, Chlorarachnion

syncytial, free-living

MAJOR PIGMENT:Chlorophyll b

CRYPTOMONADS

About 12 genera of flagellates, Cryptomonas

single cells, rarely forming colonies, some are endobiotic

MAJOR PIGMENTS:Chlorophylls a and c, phycobilins

EUGLENIDS

about half of the genera (35) contain members with green chloroplasts, flagellates, Euglena, Trachelomonas

single cells

MAJOR PIGMENT:Chlorophyll b

GLAUCOPHYTES

Several genera of flagellated and non-flagellated protists with similar phycobilin-rich symbionts, e.g. Glaucocystis, Cyanophora

flagellated and non-flagellated cells

MAJOR PIGMENT:Phycobilin

HAPTOPHYTES

Diverse, with many genera, all or all bar one genera with plastids, with naked species and those with scales (coccolithophores)

single cells, some are endosymbionts

MAJOR PIGMENTS:Chlorophylls a and c

RED ALGAE (Rhodophyta)

All species are regarded as algal

free-living and parasitic, single celled, and multicellular

MAJOR PIGMENTS:Phycobilins

STRAMENOPILES

Most but not all stramenopiles are algae, the group includes diatoms, brown algae, synurophytes and other 'chrysophytes'

single celled, colonial and multicellular, free-living and parasitic

MAJOR PIGMENTS:Chlorophylls a and c

VIRIDAEPLANTAE

The green algae, all but a few genera are algal, prasinophytes, chlorophyta (e.g. volvocalean algae, conjugatopohytes, Ulvales, Charales)

single celled, colonial and multicellular, free-living

MAJOR PIGMENT:Chlorophyll b

Genera of algal protists for which no clear ultrastructuralidentityhas been developed (after Patterson, 1999):

  • Adinomonas
  • Archaeosphaerodiniopsis
  • Aurospora
  • Berghiella
  • Bjornbergiella
  • Boekelovia
  • Camptoptyche
  • Chalarodora
  • Chlamydomyxa
  • Copromonas
  • Cyanomastix
  • Dinoasteromonas
  • Dinoceras
  • Glaucocystopsis
  • Goniodinium
  • Heteromastix
  • Hillea
  • Histiophysis
  • Isoselmis
  • Melanodinium
  • Meringosphaera
  • Monodus
  • Nephrodinium
  • Pachydinium
  • Peliainia
  • Petasaria
  • Phialonema
  • Pleuromastix
  • Pseudoactiniscus
  • Strobilomonas
  • Syncrypta
  • Tetragonidium
  • Thaulirens
  • Thaumatodinium
  • Thylakomonas
  • Triangulomonas
license
cc-by-3.0
copyright
David J. Patterson
bibliographic citation
Algae: Protists with Chloroplasts. Authored by David J. Patterson. Tree of Life; accessed August 13, 2013
author
Jennifer Hammock (jhammock)
original
visit source
partner site
EOL authors