Ceratium
| Ceratium | |
|---|---|
 |
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| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | SAR |
| (unranked): | Alveolata |
| Phylum: | Dinoflagellata |
| Class: | Dinophyceae |
| Order: | Gonyaulacales |
| Family: | Ceratiaceae |
| Genus: | Ceratium |
| Species | |
The genus Ceratium includes species of freshwater and marine dinoflagellates. Most species of Ceratium are unicellular organisms that are characterized by their armored plates, two flagella, and horns. Species of Ceratium are found worldwide and are of concern due to their blooms.
The genus was originally published in 1793 by Shrank, F. von Paula. The taxonomy of Ceratium varies among several sources. One source states the taxonomy as: Kingdom Chromista, Phylum Miozoa, Class Dinophyceae, Order Gonyaulacales, and Family Ceratiaceae. Another source lists the taxonomy as Kingdom Protozoa, Phylum Dinoflagellata, Class Dinophyceae, Order Gonyaulacales, and Family Ceratiaceae. The taxonomic information listed on the right includes Kingdom Chromalveolate. Thus, sources disagree on the higher levels of classification, but agree on lower levels.
Ceratium species belong to the group of dinoflagellates known as dinophysiales, meaning they contain armored plates. They contain a pellicle, which is a shell, that is made from the cell membrane and vesicles; vesicles are composed of cross-linked cellulose, forming the plates. The pellicle divides into two structures known as the epicone and hypocone that lie above and below the transverse groove, the cingulum, respectively. Two rows of plates surround the epicone and hypocone in a particular pattern that may be inherited by offspring. These patterns may be used to identify groups of dinoflagellates or even species of Ceratium.
The plates contain expanded horns, which is a characteristic feature of Ceratium species. Species tend to have different shaped horns depending whether they are freshwater or marine species. Their morphology depends on the temperature and salinity of the surrounding environment. Species can be identified based on the shape of their horns. For instance, the species Ceratium tripos has horns that are U-shaped.
Species of Ceratium contain two flagella of different lengths that are orientated in the transverse and longitudinal positions. The transverse flagellum is structurally complex and wraps around the cingulum. The movement of the flagellum is described as "wave-like" and allows the organism to spin as it swims. The longitudinal flagellum extends from a groove known as the sulcus, and this flagellum is simpler in structure than the transverse flagellum. The movement of this flagellum pulls the organism forward, but ultimately its movement is controlled by the viscosity of the water.
Species of Ceratium have other structures called chromatophores, which contain red, brown, and yellow pigments used for photosynthesis.
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