Monterey Bay Aquarium Research Institute
Marine Botany

KINGDOM: Protista

DIVISON: Heterokontophyta

CLASS: Phaeophyceae

ORDER: Fucales

FAMILY: Cystoseiraceae

GENUS: Stephanocystis (was known as Cystoseira)

SPECIES: osmundacea

The kingdom protista contains a variety of different organisms, ranging from animal-like to fungi-like. These organisms have all been included to the same taxonomic kingdom for their simple construction, and most are unicellular species. Algae used to be classified with plants because they have chlorophyll a, they are plantlike and photosynthetic. But they have since been moved to Protista because of their simple construction, the broad range of photosynthetic pigments they use, the lack of protective tissue surrounding their "naked" gametes, and their highly varied life histories.The algae are considered primitive photosynthetic organisms based on their reproduction and simplistic construction. Algae have been found in the fossil record as early as 590 million years ago for macroscopic algae, and 1900 million years ago for microscopic algae.

Motile cells are heterokonts; their two flagella are of unequal length and differing morphologies. The brown algae are placed into one class: Phaeophyceae. Their distinguishing characteristics are outlined within the class.

The class Phaeophyceae contains 265 genera and over 2000 species, of which 99% are marine organisms. The brown algae are distinguished by a suite of characteristics including the following:
Photosynthetic pigments: chlorophyll a and c, beta carotene, violaxanthin, and fucoxanthin.
Food reserves: laminaran, a soluble polysaccharide, and mannitol, a sugar-alcohol.
Cell construction: cellulose fibers bound with alginic acid form cell walls, cells uninucleate.
Chemistry: presence of soluble extract, fucoidans, which are sulfated polysaccharides.
Reproduction: most are haplobiontic, except the diplontic, oogamous Fucales

diplontic, oogamous life history, with unique sperm morphology (anterior flagellum is shorter and pleuronematic).
Cell construction: chloroplasts lack pyrenoids.

Sargassaceae (was thought previously to be Cystoseiraceae)
Contains as many as 17 genera.
Cell construction: single apical cell terminates each axis; three-sided apical cell (thought to be a more primitive, ancestral trait).
Reproduction: formation of one ova per oogonium.

Characterized by highly differentiated basal and apical regions; presence of catenate pneumatocysts.

Characterized by chains of pneumatocysts on terminal apical fronds and bipinnate branching of basal blades.

Last updated: Mar. 16, 2015