Dinoflagellates - Dinophyta
All dinoflagellates have two flagella and they are quite mobile. The first flagellum is placed in the transverse groove on the one side of the cell and the wave-motion of this flagellum drives the cell forward. The second flagellum arises from a longitudinal groove, which is connected with transverse groove and the flagellum here drives the cell in spirals. The most of the dinoflagellates are autotrophic, but there exist some species without chloroplast and so have a heterotrophic way of life.
The cells of the dinoflagellates can be naked (the genera Gymnodinium) or they have a cell wall. The cell wall is composed of a network of plates of cellulose. The number and arrangement of these plates is used to distinguish the genera. The cell nucleus is big and easy to observe.
The cell reproduces by dividing. Beside there can be sexual reproducing.
A lot of the species form cysts. The cyst is formed inside the cell wall, which eventually breaks to release it. The cysts are surrounded by a thick wall and contain abundant food reserves. In temperate and northern regions the cysts specific of Ceratium usually appear in late summer and they sink rapidly to the bottom and remain there until next spring when they germinate. In marine deposits fossil remains of dinoflagellate cysts are relatively common and can be valuable stratigrafic markers in oil exploration.
Some of the marine species produce toxic substances. Special known is the diarhoea poison (DSP) accumulating in the mussels grazing on dinoflagellates, ex. Dinophysis. Some dinoflagellates are known to be the organisms involved in red tides, which are caused by rapid increases of dinoflagellate population sufficient to colour the sea water a dull red-brown.
- Dinoflagellates
- Fresh water
- Ceratium
- Peridinium
- Sea water
- Ceratium
- Dinophysis
- Gymnodinium
- Phalacroma
- Prorocentrum
- Protoperidinium