The periplast is one of three types of cell-covering of three classes of
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
. The
cryptomonad
The cryptomonads (or cryptophytes) are a superclass of algae, most of which have plastids. They are traditionally considered a division of algae among phycologists, under the name of Cryptophyta. They are common in freshwater, and also occur ...
s have the periplast covering. The
have a type called the
amphiesma, and the ''
Euglena
''Euglena'' is a genus of Unicellular organism, single-celled, flagellate eukaryotes. It is the best-known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of '' ...
'' covering is the
pellicle.
Structure
The periplast is a proteinaceous covering. It can be subdivided into an inner periplast and an outer periplast. Both of these components are variable in their composition.
The inner periplast may be formed as a single sheet as in the ''
Chilomonas
''Chilomonas'' is a genus of cryptophytes, including the species '' Chilomonas paramecium''. ''Chilomonas'' is a protozoan (heterotroph). ''Chilomonas'' is golden brown and has two flagella
A flagellum (; : flagella) (Latin for 'whip' or ' ...
paramecium'',
or as multiple plates of varying shape. The outer periplast surrounds the plasma membrane. The inner periplast below the plasma membrane may sometimes as in ''
Komma caudata'' have a hexagonal arrangement of superficial periplast plates, and these are made up of sub-units.
The superficial plates are lined up exactly with the inner plate and are surrounded by crystalline borders with the occasional rosette scale on the surface of the plates. A number of different periplast arrangements have been described in cryptomonads. On the inner periplast part there may be seen intermembrane particles that penetrate the plasma membrane into the protoplasm. These intermembrane particles are larger around the plate boundaries.
The Dinophyceae has a cell covering called the amphiesma–cisternae-like vesicles in a
thecal form structure. Many of the dinoflagellates have thicker thecal plates giving them the name of ''armoured dinoflagellates''. The covering of the
Euglenid
Euglenids or euglenoids are one of the best-known groups of eukaryotic flagellates: single-celled organisms with flagella, or whip-like tails. They are classified in the phylum Euglenophyta, class Euglenida or Euglenoidea. Euglenids are common ...
s is called the
pellicle.
References
{{Reflist
Algal anatomy