''Haematococcus lacustris'' is a freshwater species of green algae
Chlorophyta
Chlorophyta is a division of green algae informally called chlorophytes.
Description
Chlorophytes are eukaryotic organisms composed of cells with a variety of coverings or walls, and usually a single green chloroplast in each cell. They are ...
from the family
Haematococcaceae. This species is well known for its high content of the strong antioxidant
astaxanthin
Astaxanthin is a keto- carotenoid within a group of chemical compounds known as carotenoids or terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups.
It is a lipid-solu ...
, which is important in aquaculture, and cosmetics. The high amount of astaxanthin is present in the resting cells, which are produced and rapidly accumulated when the environmental conditions become unfavorable for normal cell growth. Examples of such conditions include bright light, high salinity, and low availability of nutrients. ''Haematococcus lacustris'' is usually found in temperate regions around the world. Their resting cysts are often responsible for the blood-red colour seen in the bottom of dried out rock pools and bird baths. This colour is caused by astaxanthin which is believed to protect the resting cysts from the detrimental effect of UV-radiation, when exposed to direct sunlight.
Description
In its vegetative state, ''Haematococcus lacustris'' consists of motile, spherical to ellipsoid cells, (8–)10–30(–51) μm wide and (10–)15–50(–63) μm long, embedded in a broad expanded
cell wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
. The cell wall is attached to the
protoplast
Protoplast (), is a biology, biological term coined by Johannes von Hanstein, Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by stripping the cell wall from plant, bacterium, bacterial, or f ...
via fine threads of
cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
. Two flagella are present. The
chloroplast
A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...
is parietal and has several
pyrenoid
Pyrenoids are sub-cellular phase-separated micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., & Raven, J. A. (2005). CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. ''An ...
s and an anterior
eyespot.
Contractile vacuole
A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole.
Overview
The contrac ...
s are numerous and scattered throughout the cytoplasm.
When deprived of
fixed nitrogen
Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiologically in chemical industries. Biological nitrogen fixation or ''diazotrophy'' is catalyzed by enz ...
, ''Haematococcus lacustris'' produces
carotenoid
Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...
pigments (particularly astaxanthin) giving the cytoplasm a deep red color. In unfavorable conditions, the cells lose their flagella and become immobile