Photosynthetic Protists - Dinoflagellates
Description:
The general characteristics of dinoflagellates are as follows −
Habits and Habitats
Most are marine but also occur in fresh water.
Some grow in large number in the sea and make the water look red and cause the phenomenon of "red tide".
Some show bioluminescence i.e. it emits light.
Reserved food is stored in the form of starch and oils.
Structure
Unicellular motile and biflagellated.
Cells are generally covered by rigid coat called theca or lorica.
Dinoflagellates are known as armoured dinoflagellates due to the presence of sculptured plates.
The two flagella are different. One transverse and the other longitudinal.
The nucleus is larger and has been named as mesokaryon.
Chromosomes do not have histone or RNA.
Reproduction
Asexual reproduction occurs through cell division.
Sexual reproduction has been reported in some dinoflagellates.
The life cycle involves zygotic meiosis.
Economic importance
Some dinoflagellates are poisonous to vertebrates.
When they are present in large numbers they produce the toxin called saxitoxin into sea which kills fishes and other aquatic animals.
Shell fish consumes dinoflagellates but the poison does not harm them.
If this fish is consumed by man it causes severe illness called paralytic shell fish poisoning (PSP) it may be fatal.