SYNOPTIC DESCRIPTION OF THE PHYLUM DINOFLAGELLATA (BÜTSCHLI 1885)
| EUKARYA> CHROMALVEOLATA> ALVEOLATAE> DINOFLAGELLATA |
DINOFLAGELLATA LINKS
| Description of the phylum is taken from Taylor (1987; 1990), Lee (1980), Loeblich (1976), Dodge (1973), Sze (1986), Margulis and Schwartz (1988 and 1998), and Sleigh et al. (1984). |
I. SYNONYMS: Dinoflagellates, pyrrhophyta, dinomastigota, dinophyta.
II. NUMBER: >4,000 species known.
III. PHYLUM CHARACTERISTICS:
- A. Structure and Physiology
- Cell Form: Unicellular, with characteristic grooves ( cingulum (text with tooltip) A cingulum (also called a girdle or cinctum) is a groove that circles the dinoflagellate cell and in which lies the ribbon flagellum. and sulcus (text with tooltip) A sulcus is a longitudinal groove (from the cingulum to the posterior end of the dinoflagellate cell and in which lies the trailing whiplash flagellum. ) in some stage of the life history.
- Flagella: Two dissimilar flagella: 1 whiplash (text with tooltip) (1) A whiplash flagellum is a eukaryotic 9+2 flagellum with few or no flagellar hairs or scales. These may be directed anteriorly or posteriorly. (2) A whiplash flagellum is free of hair-like mastigonemes and usually is trailing or posteriorly-directed. and 1 ribbon-like (text with tooltip) The ribbon-like flagellum is a tinsel (with flagellar hairs) flagellum and is flattened. Although it occurs in several groups of microbial eukaryotes, it is characteristic of dinoflagellates where it lies in the cingulum. tinsel flagellum with a paraflagellar rod.
- Cell Covering: A complex pellicle (text with tooltip) A pellicle is a complex outer cellular covering that occurs within the bounds of the plasmalemma. Often synonymous with the term theca, a pellicle defines such groups as the euglenoid-kinetoplastid clade amd the Kingdom Alveolatae. ( theca (text with tooltip) A theca (also called an amphiesma) is the name of the dinoflagellate pellicle (formed by the alveolar structure of the cell covering. Cells may be naked (gymnodinoid) or 'armored'. Armored dinoflagellates have alveoli that contain cellulosic plates. , sometimes called amphiesma) with overlapping plates contained in vesicles; the plates may or may not be cellulosic (text with tooltip) Armored dinoflagellates have cellulosic plates that fill the alveoli. The architecture of the particular plates is conserved within the species such that they can be determined according to the tabulation. The plates have flanges that allow them to overlap adjacent ones. Also, they are perforated with holes that allow for the discharge of trichocysts. .
- Chloroplasts: Chloroplasts brownish or golden: chl a and c (text with tooltip) Chlorophyll C is a variant of Chlorophyll A. and a secondary photosynthetic pigment in the many of the photosynthetic heterokonts and dinoflagellates. ; b carotene and various xanthophylls (text with tooltip) Xanthophyll is an oxygenated carotenoid secondary photosynthetic pigment that occurs in many of the photosynthetic eukaryotes. (including peridinin); thylakoids in stacks of 3’s.
- Food Reserves: Starch and oil.
- Mitochondria: Present with tubular cristae (text with tooltip) Mitochondrial cristae that form as extended saccate structures or tubes are called tubular cristae. .
- Golgi (text with tooltip) Golgi apparatus (also called dictyosome) is an internal membrane system of stacked flattened sacs. They occur in nearly all eukaryotes and are involved in storing and secreting cellular products. : Present.
- Nucleus: Nucleus conspicuous with condensed chromosomes; without histones, called a dinokaryon.
- Centrioles: Absent.
- Inclusions and Ejectile Organelles:
- Trichocysts (text with tooltip) Trichocysts are extrusosomes that also are characteristic of the ciliates and dinoflagellates. They can discharge and serve almost as an organelle equivalent to the nematocyst. However, their particular functions have yet to be defined to my satisfaction. ; some with nematocysts; some with eye spots (text with tooltip) An eyespot is a light-sensitive structure that does not form an image. This can be part of an organelle as in the chloroplast of certain microbial eukaryotes. It can be an elaborate structure that involves a light-sensitive swelling at the base of a flagellum (as in the euglenoids) or it can be a multicellular structure as in planarians. which vary with species; many with food vacuoles.
- B. Mitosis, Meiosis and Life History
- Mitosis: Nuclear membrane is closed (text with tooltip) Mitosis is closed when the segregation of daughter chromosomes occurs within the bounds of the nuclear membrane (the nuclear membrane does not break down). with an extra-nuclear spindle (text with tooltip) Extra-nuclear spindles elaborate outside of a nucleus whose membrane does not break down. The spindle fibers attach to the nuclear envelope and, presumably, to a chromosome attached to the envelope. .
- Meiosis: Occurs but details poorly known; it seems to be similar to mitosis.
- Sexual Reproduction and Life History: Usually isogamous (text with tooltip) Isogamous (adj) describes sexual reproduction in which the gametes are structurally identical. (some are anisogamous (text with tooltip) Anisogamous (adj.) describes sexual reproduction in which the gametes are structurally siimilar, but not identical. or oogamous) with zygotic meiosis (text with tooltip) An organism is said to undergo zygotic meiosis when the zygote is the only diploid cell in the life cycle. Thus, the life history is haplontic (primarily haploid). ; at least 1 group has gametic meiosis (text with tooltip) An organism is said to undergo gametic meiosis when the gametes are the only haploid cells in the life cycle. Thus, the life history is diplontic (primarily diploid). . General Life History of Dinoflagellates.
- C. Ecology: Freshwater and marine; plankters, epiphytes, endosymbionts (text with tooltip) An endosymbiont is a living cell that has become symbiotic within the host cell. Thus, the endosymbiont and the host become interdependent. Mitochondria and chloroplasts (among others) are common endosymbionts. , and parasites; photosynthetic, phagotrophic, or saprobic.
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| By Jack R. Holt. Last revised: 02/19/2012 |
