Glaucophyte

Glaucophyte

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Glaucophyte

The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater microscopic algae.^[1] Together with the red algae and Viridiplantae (green algae and land plants) they form the Archaeplastida. However, the relationships between the red algae, green algae and glaucophytes are unclear,^[2] in large part due to limited study of the glaucophytes.

There are only 13 species of glaucophytes known, none of which are particularly common in nature.^[1]

The chloroplasts of glaucophytes are known as cyanelles. Unlike other eukaryotic plastids they have a peptidoglycan layer which is believed to be a relic of the endosymbiotic origin of plastids from cyanobacteria.^[1] Glaucophytes contain the photosynthetic pigment chlorophyll a.^[1] Along with red algae^[1] and cyanobacteria they harvest light via phycobilisomes, structures consisting largely of phycobiliproteins. The green algae and land plants have lost that pigment.

The glaucophytes are of obvious interest to biologists studying the development of chloroplasts: if the hypothesis that primary chloroplasts had a single origin is correct, glaucophytes are closely related to both green plants and red algae, and may be similar to the original alga type from which all of these developed.

Glaucophytes have mitochondria with flat cristae, and undergo open mitosis without centrioles. Motile forms have two unequal flagella, which may have fine hairs and are anchored by a multilayered system of microtubules, both of which are similar to forms found in some green algae.

The three main genera included are:

Glaucocystis is non-motile, though it retains very short vestigial flagella, and has a cellulose wall.
Cyanophora is motile and lacks a cell wall.
Gloeochaete has both motile and non-motile stages, and has a cell wall that does not appear to be composed of cellulose.