The flagellated haploid cells can laterally fuse and form a diploid zygote that can remain motile. Under unfavorable conditions, however, some dinoflagellate zygotes enlarge and thicken the hypnozygote stage , lose motility and produce red bodies within the cell.
This diploid form, called a cyst or dinocyst , settles to the bottom of the water column and is a "resting stage" in the dinoflagellate's life cycle. The cyst can have a tough coating of a substance called sporopollenin, or it may be embedded with calcium carbonate or silica. The cysts emerge, or germinate, in a motile stage upon encountering favorable environmental conditions, with another round of division, this time by meiosis , again resulting in a haploid cell.
This type of life cycle strategy is termed haplontic. M any dinoflagellates are photosynthetic and are among the major primary producers of the phytoplankton along with diatoms. Dinoflagellates are generally described as C 3 plants , although some species may resemble C 4 plants under certain conditions, and dinoflagellates, in general, may show some characteristics of both types. The difference between these types is whether or not three or four carbon sugars are produced and the enzymes used to fix CO 2.
Chloroplasts are membrane bound organelles found within photosynthetic organisms that are the primary sites of light harvesting and photosynthesis, and contain most of the photosynthetic pigments.
The chloroplasts found in red and green algae are known to have evolved from a symbiosis between a cyanobacterium and a eukaryotic cell more than one billion years ago. The primary light absorbing pigments in most plant chloroplasts are the chlorophylls.
Dinoflagellates have both chlorophyll a chl- a and chlorophyll c chl- c whereas most plants and green algae contain mostly clorophyll a and, to a lesser degree chl- b. Chlorophylls d and e also exist in algae, the former mainly in some red algae. While some other organisms besides dinoflagellates contain chl- c , this pigment suggests a larger evolutionary disparity between dinoflagellates and most other "phytoplankton.
In the case of chl- b , more common in green algae, the spectrum is shifted towards the longer wavelengths into the green spectrum. Chl- c lacks as great a peak in the red spectrum as chl- a , and it might be surmised that having chl- b would be more advantageous to dinoflagellates, since less competition for light is the primary reason to harbor various pigments. However, it is the coupling of chlorophylls with peridinin, a broad band light harvesting pigment, that gives dinoflagellates a distinct advantage over other phytoplankton.
Chlorophylls are the pigments largely responsible for green coloration in plants. The primary absorption peaks are at nm and nm, and nm and nm for chl- a and chl- c , respectively, corresponding to the blue and red areas of the spectrum. Because dinoflagellate chloroplasts are unusually contained by three membranes, as opposed to a normal one or two, it is believed that they likely have evolved a tertiary endosymbiosis with a plasmid that contains the additional photosynthetic pigment complex of peridinin Morden and Sherwood The orange-red peridinin pigment absorbs very broadly, with a maximum at around nm and another small shoulder at nm.
The combined units of carotenoid-chlorophyll-protein complexes PCP complex consisting mainly of peridinin, chlorophyll a , and one of 12 to 20 proteins, form multiple complexes where, interestingly, the interaction of chlorophyll with the peridinin protein shifts the absorption peaks of chl- a upwards about 10nm. Other pigments are used indirectly as accessory pigments. Some have oxidative abilities and are used in the electron transport chains that are part of both the light and dark reactions of photosynthesis.
Some even have duplicate functions, adding other levels of function to the photosynthetic cell. For example, fucoxanthin can be present as an accessory pigment in peridinin-containing species, while in some others, it may replace peridinin. Fucoxanthin is a common carotenoid primarily in diatoms and dinoflagellates.
Carotenoids are accessory pigments that are responsible for predominantly yellow and orange coloration and absorb primarily between nm and nm. Their color is usually masked by the presence of chlorophyll, but in dinoflagellates chlorophylls play second fiddle to peridinin.
Carotenoids are composed of carotenes and carotenols xanthophylls. Carotenes have numerous secondary functions, but may be most important to zooxanthellae by acting as antioxidants. Xanthophylls consist of oxygenated carotenes such as neoxanthin, violaxanthin and lutein, all of which provide characteristic coloration through absorption, either functionally or incidentally.
Fucoxanthin is a yellow-green pigment with primary absorption around nm that is characteristic of dinoflagellates. Also important in dinoflagellates are the xanthophylls dinoxanthin and diadinoxanthin, which play roles in preventing photooxidative damage to the photosynthetic apparatus.
Also unusual for eukaryotes is that dinoflagellates show distinct circadian rhythms, most notably by the daily migration of the chloroplasts within the cells. Perhaps of most interest to aquarists, unarmored marine dinoflagellates of many species are the marine symbionts known as zooxanthellae that take up residence within the gastrodermis of most hermatypic reef building coral polyps.
However, dinoflagellates have similar symbiotic roles with other marine invertebrates including sea anemones, radiolarians , sponges, foraminiferans , turbellarians , jellyfish, clams, and other groups. Much of the golden or brown color of corals is due to the zooxanthellae, and in particular their xanthophyll content and composition. The degree to which this color contributes to the corals' overall color depends on many factors, including genetics heritable phenotype , pigment density, algal cell density, and production of animal-associated fluorescing proteins.
Nonetheless, symbioses with corals have enabled coral reefs to develop, since the partnership potentially allows the calcification rate of corals to outpace natural degrading and eroding processes. Not all dinoflagellates are autotrophic , however, and some do not photosynthesize at all. They can also exist by several variably heterotrophic strategies including species that are phagotrophic ingesting whole cells , saprophytic feeding on decaying matter , parasitic feeding directly on other organisms , and mutualistic living in mutually beneficial symbioses.
Herbivory is possible in many species, and some species have potent cellulolytic enzymes to degrade plant cell walls. Phagotrophic species may attach to the surface of their prey and then develop rhizopodia that envelop the cell. Dinoflagellate species are known to feed on eggs particularly copepod eggs , unicellular and filamentous algae, bacteria, and other microorganisms.
P erhaps the most infamous aspect of dinoflagellates is the ability of some species to produce toxins. Blooms of toxin-producing dinoflagellates are called "red tides" and these often-seasonal events make news. Dinoflagellates are also responsible for ciguatera and other shellfish poisonings. Harmful dinoflagellate blooms produced by between toxic species, are very similar to blooms of non-toxic species and likely occur by competitive exclusion.
However, all toxic species are photosynthetic, exist in estuarine or neritic coastal water overlying the continental shelf areas, and produce water- or lipid-soluble toxins. They can be problematic, for some of the rapidly blooming species produce potent neurotoxins called saxitoxins and related toxins.
These toxins accumulate in suspension feeders such as edible mussels and clams, and can also accumulate or kill fish or other animals, including man, that eat these shellfish. The onset of symptoms, called paralytic shellfish poisoning, can occur almost immediately upon ingestion.
If inhaled, death can occur within minutes, and while there is no antidote, the toxin is inactivated by strong bases.
Ironically, saxitoxin and tetradotoxin in miniscule amounts is part of the "dangerous pleasure" of eating fugu, a sashimi of various pufferfishes. Both poisons are found and both act in a similar fashion by blocking sodium channels. Other dinoflagellate species can produce brevetoxins that cause symptoms similar to those of neurotoxic shellfish poisoning. Massive fish kills along the Gulf Coast have been caused by brevetoxin-producing dinoflagellate species, and aerosolization of seaspray during red tides can cause sickness in those living on or visiting coastlines.
The most common marine toxin disease is ciguatera, a neurologic gastrointestinal and cardiovascular impairment caused by the accumulation of dinoflagellate-produced ciguatoxin in contaminated fish. The higher the trophic level of the fish, the more concentrated the ciguatoxin, and barracuda, eels, groupers, snappers and jacks are notorious for causing cases of ciguatera in humans after being eaten.
A more recent and frightening discovery in of a toxic dinoflagellate can be found in Pfiesteria piscicida. This species has been responsible for massive fish kills along the Atlantic coast of the United States and produces at least one very potent neurotoxin. The blooms, occurring mainly in estuarine habitats, are short-lived, often lasting only a few hours.
What makes Pfiesteria so intriguing is that there are at least 24 forms in its life cycle, including normal non-toxic photosynthesizing forms, toxic and non-toxic cyst forms, and a predatory form. One toxin produced by a cyst stage stuns fish, facilitating attachment of the dinoflagellate. The same toxin causes tissue necrosis and open sores. Another toxin affects fish respiration.
Then, the dinoflagellate adopts a micropredatory role and feeds on the dissolving tissue. B esides the precautions that should be taken for toxic dinoflagellates which are certainly potentially present in marine aquaria, and the obvious interest in symbiotic species such as zooxanthellae, aquarists are probably well-familiar with reports or experiences of a brown, slimy, snotty algae that traps gas bubbles and covers the surfaces of live rock, tank walls, and even corals.
A web photo of the appearance of this material can be found here. Such periodic blooms are often reported in the spring, and seem to correlate with deaths of fish and especially with lethargy or paralysis and death of herbivorous snails.
These are covered extensively by Sprung and Delbeek , along with methods of eradication. Such cases may indeed be blooms of toxic dinoflagellates. There are, however, other toxic microalgae, other slimy snotty algae, and other algae that trap gas bubbles. The gas bubbles are likely oxygen being produced by photosynthesis, and of the many mat or film-forming microorganisms, photosynthetic protists, algae, and cyanobacteria can all appear very similar. Cyanobacteria, in particular, are also well known for producing toxins.
Did you know that you have a Circadian rhythm too? During the dinoflagellate daytime cycle the only action taking place is photosynthesis. Interestingly enough their Circadian cycle can be modified over time several days by providing light at night and keeping them in a dark area during the day. Over time several days to a week they will adapt to their new light cycle. Bioluminescence is probably what PyroDinos are best known for.
Bioluminescence is the production of light by a living organism and occurs only at night, in the dark, when these Dinos are gently agitated and physically moved. Many other organisms produce bioluminescence. Some examples are fireflies, some mushrooms and bacteria. When you see bioluminescence in a complex organism like an Angler fish it is most likely from a symbiotic bacteria that is living within that organism.
Bioluminescence is caused by a chemical reaction between a light emitting molecule and an enzyme that are generically referred to as luciferin and luciferase. During and throughout the dinoflagellate nighttime cycle these light producing molecules are produced. Am Nat 95 — Jacobson DM The ecology and feeding biology of thecate heterotrophic dinoflagellates. J Phycol 22 — Jacobson DM, Andersen RA The discovery of mixotrophy in photosynthetic species of Dinophysis Dinophyceae : light and electron microscopical observations of food vacuoles in Dinophysis acuminata, D.
Phycologia 33 — Jacobson DM, Anderson DM Widespread phagocytosis of ciliates and other protists by marine mixotrophic and heterotrophic thecate dinoflagellates. J Phycol 32 — Mar Ecol Prog Ser : — Jeong HJ a Predation effects of the calanoid copepod Acartia tonsa on a population of the heterotrophic dinoflagellate Protoperidinium cf.
Jeong HJ b Predation by the heterotrophic dinoflagellate Protoperidinium cf. Jeong HJ The interactions between microzooplanktonic grazers and dinoflagellates causing red tides in the open coastal waters off southern California.
Available on microfilm from University of Michigan, Accession Number Jeong HJ The ecological roles of heterotrophic dinoflagellates in marine planktonic community. J Eukaryot Microbiol 46 : — J Eukaryot Microbiol 48 — J Eukaryot Microb 50 — J Shellfish Res 23 — Aquat Microb Ecol 36 — J Eukaryot Microbiol 51 — Aquat Microb Ecol 41 — Aquat Microb Ecol 40 — Aquat Microb Ecol 38 — Aquat Microb Ecol 44 — J Eukaryot Microbiol 54 — J Eukaryot Microbiol 55 — Feeding in western Korean water.
Aquat Microb Ecol 59 — Theoret Popul Biol 66 — Kamiyama T, Arima S Feeding characteristics of two tintinnid ciliate species on phytoplankton including harmful species: effects of prey size on ingestion rates and selectivity. J Eukaryot Microbiol 57 — Relationships between the occurrence of Prorocentrum minimum red tide and environmental conditions. Bull Plankt Soc Japan Hiroshima 37 — Koski M, Riser CW Post-bloom feeding of Calanus finmarchicus copepodites: selection for autotrophic versus heterotrophic prey.
Mar Biol Res 2 — Larsen J An ultrastructural study of Amphidinium poecilochroum Dinophyceae , a phagotrophic dinoflagellate feeding on small species of cryptophytes. Phycologia 27 — Lee CW Growth and grazing rates of the heterotrophic dinoflagellate Oxyrrhis marina and the ciliate Stormbidinopsis sp. Lee SH Feeding by mixotrophic red-tide algae on photosynthetic picoeukaryotes.
Aquat Microb Ecol 15 — Lessard EJ Oceanic heterotrophic dinoflagellates: distribution, abundance and role as microzooplankton. Thesis, University of Rhode Island, Kingstown, p. Lessard EJ, Swift E Species-specific grazing rates of heterotrophic dinoflagellates in oceanic waters, measured with a dual-label radioisotope technique.
Mar Biol 87 — J Phycol 36 — J Phycol 43 — McFadden GI Primary and secondary endosymbiosis and the origin of plastids. J Phycol 37 — Physiol Plant 69 :1—8. Harmful algae 5 — Nakamura Y, Yamazaki Y, Hiromi J Growth and grazing of a heterotrophic dinoflagellate, Gyrodinium dominans , feeding on a red tide flagellate, Chattonella antiqua. Mar Ecol Prog Ser 82 — Naustvoll L-J Growth and grazing by the thecate heterotrophic dinoflagellate Diplopsalis lenticula Diplopsalidaceae, Dinophyceae.
Phycologia 37 :1—9. Naustvoll L-J Prey size spectra and food preferences in thecate heterotrophic dinoflagellates. Nygaard K, Tobiesen A Bacterivory in algae: a survival strategy during nutrient limitation. Limnol Oceanogr 38 — Aquat Microb Ecol 45 — Mar Micropaleontol 62 — Scura ED, Jerde C Various species of phytoplankton as food for larval northern anchovy, Engraulis mordax , and relative nutritional values of the dinoflagellate Gymnodinuim splendens and Gonyaulax polyedra.
Fish Bull 75 — Ant van Leeuwenh 81 — Siano R, Montresor M Morphology, ultrastructure and feeding behaviour of Protoperidinium vorax sp. Dinophyceae, Peridiniales. Eur J Phycol 40 — Skovgaard A a Engulfment of Ceratium spp. Dinophyceae by the thecate photosynthetic dinoflagellate Fragilidium subglobosum.
Phycologia 35 — Skovgaard A b Mixotrophy in Fragilidium subglobosum Dinophyceae : growth and grazing responses as functions of light intensity. Skovgaard A Role of chloroplast retention in a marine dinoflagellate. Skovgaard A A phagotrophically derivable growth factor in the plastidic dinoflagellate Gyrodinium resplendens Dinophyceae.
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