Presentation is loading. Please wait.

Presentation is loading. Please wait.


Similar presentations

Presentation on theme: "Dinoflagellates."— Presentation transcript:

1 Dinoflagellates

2 Introduction Dinoflagellates are unicellular, flagellated protists
The first modern dinoflagellate was described by Baker in 1753 The dinoflagellates were first defined by Otto Bütschli in 1885 as the flagellate order Dinoflagellida. Botanists treated them as a division of algae, named Pyrrhophyta after the bioluminescent forms. They have also been called the Dinophyta or Dinoflagellata Over 2000 species Traditionally classified as algae Most are microscopic, but a few reach a diameter of up to 2mm The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. About half of all dinoflagellates are photosynthetic, and these make up the largest group of algae aside from the diatoms. Some species, called zooxanthellae, are endosymbionts of marine animals and protozoa, and play an important part in the biology of coral reefs. Other dinoflagellates are colorless predators on other protozoa, and a few forms are parasitic.

3 Evolution Dinoflagellates are considered to be among the most primitive of the eukaryotic group, the fossil record of the group may extend into the Precambrian period Dinoflagellates are thought to have evolved from an early eukaryotic ancestral stock following the evolution of repeated DNA Combine primitive characteristics of prokaryotes and advanced eukaryotic features Diversity of dinoflagellate species from Triassic to Quaternary. A: Total number of species per time interval; B: Grouped by family (According to classification of Fensome et al., 1994)

4 Structure All dinoflagellates are surrounded by a complex covering called the amphiesma In most dinoflagellates, this covering consists of cellulose plates referred to as “armor” Others are “naked” Gonyaulax polyedra All are surrounded by a complex covering called the amphiesma, which consists of outer and inner continuous membranes, and between which lie a series of flattened vesicles. In armored forms, these vesicles contain the thecal plates, cellulose plates that are the "armor". This armor may be lacking (the cells are "naked"), and some species shed their theca under certain environmental conditions. Armored dinoflagellates have two major plate regions composed of two to 100 individual plates. The edges of the plates overlap, sliding apart as the cell increases in size and allowing the cell to expand. The plates come in many varied shapes, from spherical forms like Peridinium to elongate horn-like forms such as Ceratium. In addition, some species have ridges or crests -- especially members of the Dinophysiales, such as the one shown at right. In some, the crests may be hollow and house cyanobacteria which provide fixed nitrogen to the host. This is most common in nitrogen-poor waters. Gonyaulax polyedra is armored Karina brevis is naked Karina brevis

5 Structure Dinoflagellates have two dissimilar flagella
The transverse flagellum lies in a groove called the cingulum and provides forward motion and spin The longitudinal flagellum lies in a groove called the sulcus and trails behind providing some propulsive force, but acting mainly as a rudder Cingulum Most dinoflagellates are unicellular forms with two dissimilar flagella. One of these extends towards the posterior, called the longitudinal flagellum, while the other forms a lateral circle, called the transverse flagellum. In many forms these are set into grooves, called the sulcus and cingulum. The transverse flagellum provides most of the force propelling the cell, and often imparts to it a distinctive whirling motion, which is what gives the name dinoflagellate refers to (Greek dinos, whirling). he combined action of these two flagella may cause the dinoflagellate to slowly turn on its axis as it moves through the water, and this is where the group gets its name. Sulcus

6 Structure There are three basic cell extensions: Lists Horns Spines
Lists are a result of the theca having ridges. Horns are basically multiple forms of body elongation and the spines result from narrow thecal extensions. All three of the cell extensions increase surface area and volume but the true function of horns and spines is unknown.

7 Cell Biology The cytoplasm of dinoflagellates contains typical eukaryotic organelles Dinoflagellates may also contain one or several distinctive organelles pusule eyespot ocellus chloroplasts -pusule which has been suggested may function in osmoregulation, waste disposal, flotation or nutrition. -Light sensitive organelles, the eyespot and more complex ocellus. -Chloroplasts bounded by three rather than the usual two membranes, which has led to suggestions that the chloroplasts in dinoflagellates were originally symbiotic algae. -The nucleus which is large and contains a prominent nucleolus

8 Cell Biology The dinoflagellate nucleus is unusual: N
Most dinoflagellates are distinguished by a dinokaryon, a special eukaryotic nucleus containing fibrillar chromosomes that remain condensed during the cell cycle and a unique external mitotic spindle. In most dinoflagellates, the nucleus is dinokaryotic throughout the entire life cycle. N Peridinium spp.

9 Cell Biology Chloroplasts:
bound by three membranes and contain chlorophylls a and c and fucoxanthin, as well as other accessory pigments a few have chloroplasts with different pigmentation and structure, some with a nucleus dinoflagellate chloroplasts may be remnants of diatoms ingested by a heterotrophic flagellate, which may have been the ancestor of modern dinoflagellates. The chloroplasts in most photosynthetic dinoflagellates are bound by three membranes, suggesting they were probably derived from some ingested alga, and contain chlorophylls a and c and fucoxanthin, as well as various other accessory pigments. However, a few have chloroplasts with different pigmentation and structure, some of which retain a nucleus. This suggests that chloroplasts were incorporated by several endosymbiotic events involving already colored or secondarily colorless forms. The discovery of plastids in Apicomplexa have led some to suggest they were inherited from an ancestor common to the two groups, but none of the more basal lines have them. Ceratium furca

10 Life Cycle Most dinoflagellates are haploid and reproduce primarily by asexual cell division (mitosis) sexual reproduction also occurs through fusion of two individuals to form a zygote may remain mobile in typical dinoflagellate form may form a resting cyst, which later undergoes meiosis to produce new haploid cells

11 Pfiesteria piscicida life cycle
more complex life cycles occur, especially among parasitic and symbiotic species Pfiesteria piscicida has a complex life cycle that includes at least 24 flagellated, amoeboid, and encysted stages or forms. Pfiesteria piscicida life cycle

12 Ecology In addition to living in the open ocean, dinoflagellates colonize tidal pools, sediments, sea-ice environments and freshwater ecosystems The distribution of dinocysts may follow patterns based on latitude, temperature, salinity, water depth and ocean circulation systems. Svalbard sits north of Norway, between the Barents and Greenland Seas, right on the edge of the Arctic Circle. In this true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image acquired August 13, 2002, by the Terra satellite, Svalbard is mostly cloud free, though snow covers much of its surface. The clouds that obscure so much of the region leave enough of the south clear to show a large phytoplankton bloom glowing turquoise against the deep blue-black of the Barents Sea. Phytoplankton are microscopic marine organisms that feed off of nutrient-rich cold waters to survive. The striking turquoise color is caused by sunlight reflecting off of chlorophyll in the phytoplankton, which (like terrestrial plants) use the process of photosynthesis to create carbohydrates from carbon dioxide and water. These phytoplankton blooms are quite common all over the world, and can appear very quickly. Phytoplankton bloom in near Svalbard in Barents Sea, Aug 13, 2002

13 Ecology Many dinoflagellates are heterotrophs and have evolved various mechanisms to ingest prey Some are autotrophs Many species are capable of both heterotrophy and photosynthesis (mixotrophic) Fluorescent microspheres (first picture) are ingested by ciliate prey (second picture). Ciliates are in turn phagocytized by the mixotrophic dinoflagellate Ceratium furca (third picture). mixotrophic dinoflagellate Ceratium furca

14 Ecology Some dinoflagellates are predators and feed on bacteria, phytoplankton and smaller dinoflagellates Some target larger prey, such as copepods, crustaceans and fish More recently, a particularly dangerous toxic dinoflagellate called Pfiesteria piscicida is reported to be a carnivorous, ambush predator. During blooms, it stuns fish with its toxin and then feeds on the prey’s body fluids. Ingestion of cryptophytes by G. galatheanum, brightfield (movie)

15 Ecology Some dinoflagellate species, called zooxanthellae, are endosymbionts of marine animals and protozoa lack characteristic armor and flagella, appear as spherical,golden-brown globules in their host cells All of the brownish colored spheres are individual dinoflagellates – inside digestive tract of stony coral Symbiodinium microadriaticum

16 These play an important part in the biology of coral reefs
provide nutrients for coral accelerate skeletal formation (calcification) give coral its color receive shelter in return Coral bleaching occurs when reef-building corals lose their endosymbiotic dinoflagellates oral reefs are the result of a most intricate and subtle relationship between the coral polyp and the minute single-celled algae which live symbiotically within the cells of the polyp. The coloring of the coral colony is a result of the enclosed zooxanthellae (Gymnodium = Symbiodinium protists) from the group of the dinoflagellates, e.g. S.microadriaticum. These algae belong to a group of unicellular brown plants known as dinoflagellates. Like land plants, the zooxanthellae are able to use the process of photosynthesis to capture the sun's energy and use it to make their own organic food from CO2, inorganic nutrients, and water. Doing so, these algae fulfill life-supporting function and aid indirectly in the calcium-carbonate precipitation. Thus, it is essential that scleractinian corals be exposed to light in order to guarantee their long-term survival. Symbiosis is a close association of two species. Both species live closely together. In the case of corals the algae lives inside the coral host (endosymbiosis - endosymbionts). In certain aspects, it is even a mutualistic bond as both species derive benefit from this association). These zooxanthellae are minute, spherical unicellular algae, are already acquired during the planulae stage and proliferate as the coral colony grows (if algae are isolated from host and cultured on their own, they transform into typical biflagellate, motile dinos). Algae can be expelled from host under stressful conditions such as seen in recent coral bleaching event. Likewise, are the corals able to re-incorporate them back into their tissue. Since algae also reside in the gastrodermis of the coral host, incorporation or "infected" of these algae is still somewhat unclear but probably occurs through ingestion. Whether more species of algae acts as the symbiont to all corals (as well as other hosts) or a single species is not clear, although there is evidence of different genetic strains in different hosts. Reef-building corals precipitate up to 6 tons CaCO3/(km2/day). By night, a polyp captures plankton with its tentacles. By day, the zooxanthellae photosynthesize. The polyp benefits from the photosynthate (product of photosynthesis), while the alga benefits from the nitrogenous wastes of the polyp. All reef-building corals are zooxanthellate, but not all zooxanthellate corals are reef builders. Non-zooxanthellate corals are not reef builders (ahermatypic). Other marine invertebrates that harbor zooxanthellae include Tridacna (giant clam), nudibranchs, Cassiopeia jellyfish, sponges, anemones, etc. However, zooxanthellae aid in skeletal excretion by removing phosphorus as a metabolic waste product from coral as dissolved phosphate may inhibit calcification, this may benefit growth of coral skeleton. Being autotrophic, zooxanthellae also remove respirative CO2 from the coral host, thus enhancing coral calcification.      1. Photosynthesis reaction: 6CO2 + 6H2O ® C6H12O6 + 6O2      2. Hydrocarbonate reaction: CO2 + H2O ® H2CO3 ® H+ + HCO3-      3. Calcification reaction: Ca++ + 2HCO3- ® Ca(HCO3)2 ® CaCO3 + H2O + CO2      4. Removal of CO2 through photosynthesis will enhance calcium carbonate precipitation. Nearly 90% of the carbon fixed by zooxanthellae is released to the coral host primarily as glycerol, glucose, and alanine. Nitrogen and phosphorous derived from captured plankton are shared between symbiont and host (Gladfelter, 1985). Global episodes of coral bleaching, where reef-building corals lose their endosymbiotic dinoflagellates and/or algal pigments during summertime elevation of seawater temperature, are recurring with increasing frequency and severity. ymbiotic dinoflagellates maintained in culture and within the host are susceptible to thermal stress (3–5). Likewise, photosynthetically active radiation (PAR) and UV radiation may act in concert with elevated temperatures to elicit a bleaching response (6, 7), yet the underlying biochemical causes for these phenomena remain obscure. Numerous components of the photosynthetic pathway are known to be susceptible to damage by elevated temperature, especially at points within photosystem II (PSII)

17 Various types of fish live on this beautiful and healthy coral (patch reef).
Fish populations reduced, but the coral is still appears healthy. Oblique coral is dead, the lower portion of the body is covered with sand. Oblique Coral, Vadoo Diving Paradise, Maldives, Feb 1997 Oblique Coral, Vadoo Diving Paradise, Maldives, Dec 1997 Oblique Coral, Vadoo Diving Paradise, Maldives, Mar 1999

18 Ecology Dinoflagellate infections have been reported for a wide range of host organisms including sarcodines, ciliates, free living dinoflagellates, various invertebrates, and a few vertebrates. Some dinoflagellates parasitize other parasitic dinoflagellates. "A stained tissue section of blue crab tissue infected with the parasitic dinoflagellate Hematodinium sp. The pink tissue is cardiac muscle. The large round structure is host defense in action. Host hemocytes are encapsulating what is presumed to be parasites in order to wall them off. The numerous round cells are Hematodinium sp. parasites. Note their darkly staining clumped chromatin which is a common characteristic of Hematodinium spp. Hematodinium sp. proliferates within the hemolymph and overwhelms the host's defense. Prevalence of Hematodinium sp. infections in blue crabs is seasonal. The seasonal infection cycle and apparent salinity and temperature requirements for infections indicate that environmental factors influence the parasite's ability to proliferate within crab hemolymph. Additionally, host factors such as size influence the prevalence of infections.The prevalence and intensity of Hematodinium sp. in blue crabs are seasonal and peak in late autumn and early winter in Maryland coastal bays. Blue crab cardiac tissue infected with Hematodinium spp.

19 Ecology The Dinoflagellata are sometimes called Pyrrhophyta (fire plants) because some species are capable of bioluminescence. Bioluminescent dinoflagellates begin to glow as it gets dark, and brighten considerably when agitated. The expression of bioluminescence is controlled by an internal biological rhythm. The Dinoflagellata are sometimes called Pyrrhophyta , meaning "fire plants". This is because some species are capable of bioluminescence, in which chemicals made by the organism produce light in a chemical reaction. The dinoflagellates begin to glow as it gets dark, but will brighten considerably when agitated, such as in the wake of a ship. The phenomenon was first noted in the genus Noctiluca, which resulted in its name ("night light"), but the reaction is now known to occur in several marine species. The chemical reaction itself occurs when the compound luciferin (a substrate chemically similar to a chlorophyll precursor), is oxidized by the enzyme luciferase in the presence of ATP and oxygen. This reaction and similar ones occur in a number of unrelated organisms, both prokaryotic and eukaryotic. The environment acts as a synchronizing agent. Entrainment is the process by which a periodic environmental signal causes circadian rhythm to remain synchronized with the environmental factor - “Re-sets the clock.” Model of circadian rhythm

20 noctiluca Noctiluca spp.

21 Significance Primary Producers
Important primary producers in both marine (particularly on-shore) and freshwater environments

22 Significance Harmful Algal Blooms
occur when a dinoflagellate species multiplies until it dominates the phytoplankton community - high concentrations cause the water to become discolored often called "red tides" but can also appear green, yellow, or brown, depending on the type of dinoflagellate involved considered harmful because dinoflagellates produce potent toxins blooms can kill fish and other marine organisms, poison people who eat contaminated shellfish, and cause respiratory distress in susceptible people

23 Florida Red Tide Bloom of Gymnodinium breve
Fish kill caused by Ceratium furca and Prorocentrum micans. 60 tons of lobster and 1500 tons of fish washed up on shore on West African west coast, Mar 1994.

24 Types of dinoflagellate related illnesses (human):
Diarrhetic Shellfish Poisoning (DSP): considered by some scientists to be the most common and globally widespread phytoplankton related seafood illness. Neurotoxic Shellfish Poisoning (NSP): gastrointestinal and neurological symptoms from eating shellfish that have fed on toxic Karenia brevis dinoflagellates Paralytic Shellfish Poisoning (PSP): PSP syndrome is life-threatening and can result in respiratory arrest within 24 hours of consuming shellfish laced with toxins from feeding on Alexandrium spp. Ciguatera fish poisoning (CFP): Ciguatera fish poisoning is caused by biotoxins produced by dinoflagellates that grow on seaweeds and other surfaces in coral reef communities.

25 Pfiesteria piscicida normally exists in non-toxic forms, feeding on algae and bacteria in the water and in sediments of tidal rivers and estuaries becomes toxic in the presence of fish, particularly schooling fish, triggered by their secretions or excrement in the water Pfiesteria cells shift forms and emit a toxin that stuns the fish, emits other toxins that break down fish skin tissue, causing bleeding sores As fish are incapacitated, the Pfiesteria cells feed on their tissues and blood implicated as a cause of major fish kills at many sites along the North Carolina coast Preliminary evidence suggests that exposure to waters where toxic forms of Pfiesteria are active may cause memory loss, confusion, and a variety of other symptoms including respiratory, skin, and gastro-intestinal problems. It has been shown that similar human health effects can be caused by exposure to Pfiesteria toxins in a laboratory setting. To date, other Pfiesteria-like organisms have not been shown to cause human illness. The Centers for Disease Control and Prevention, in cooperation with state health departments in Delaware, Florida, Georgia, Maryland, North Carolina, South Carolina, and Virginia, have established a surveillance system to collect reports of human illness thought to be related to exposure to Pfiesteria and Pfiesteria-like organisms in estuarine waters. This and other ongoing research efforts are expected to further delineate the nature, extent, and duration of any Pfiesteria-related human health effects.

26 Pfiesteria piscicida lesions on crab and fish

27 Nessie's Diet of Deadly Dinoflagellates
The Loch Ness Exploration Program has uncovered an exciting new theory to explain sightings of the famous Nessie monster. Professor Arnold Stryker (33) of the International Marine Biology and Oceanographic Diversity Research Project (on secondment to the Loch Ness Exploration Program) has located an ancient organism called Pfiesteria at 8 different points in the loch. "I did not expect to find this creature in such concentrations - it is a revolutionary discovery." Pfiesteria is part of a group of pre-historic organisms called dinoflagellates. Dr. Gunter Fishlin PhD (44) said "our Loch Ness Exploration Program has been looking for evidence of unknown creatures living in Loch Ness. We now believe that, while firm evidence of a large dinosaur living beneath the waves still eludes us, we have at least established the presence of dinoflagellates. Pfesteria is a peculiar organism. It groups together with its fellows to form large clumps of slime. This slime actually displays "ambush-predator" qualities by attacking fish. As schools of fish build up in an area Pfiesteria starts secreting toxins which overcome them. The fish die from suffocation as their nervous system collapses and their skin tissue starts to break down under the impact of the toxin. The interesting link for Loch Ness researches investigating the possibility of a large plesiosaur living in the depths is Pfiesteria's effects on humans. Dr. Fishlin explains "many eye-witnesses have come forward with accounts of their sightings of the Loch Ness monster, some of which include references to feelings of "lost time" that thy cannot explain. The toxins given off by Pfiesteria are hallucinogenic and research elsewhere has shown that a feeling of lost time is a common side effect. Are humans around Loch Ness at risk from "the cells from hell"? Professor Stryker doesn't think so: "as long as people are aware of its dangers and avoid parts of the loch where they see large clumps of algae-like slime, they should be safe.

28 Ciguatera poisoning subtropical and tropical marine finfish accumulate naturally occurring dinoflagellate toxins through their diet most common nonbacterial, fish-borne poisoning in the United States ciguatera poisoning in humans usually involves a combination of gastrointestinal, neurological, and cardiovascular disorders Ciguatera poisoning is the most common nonbacterial, fish-borne poisoning in the United States. It is caused by consumption of reef fish that feed on certain dinoflagellates (ie, algae) associated with coral reef systems. At least 5 types of ciguatoxin have been identified and are noted to accumulate in larger and older fish higher up the food chain. Ciguatera poisoning has been a significant concern in tropical areas for centuries and generally is believed to be confined to coral reef fish in water between the latitudes of 35 degrees N and 35 degrees S. In the modern era of world travel and rapid transportation, many warm-water fish are available commercially in markets throughout the world, and cases of ciguatera poisoning may be seen in any location. Pathophysiology: Gambierdiscus toxicus is the dinoflagellate most notably responsible for production of ciguatoxin, although other species have been identified more recently. Over 400 species of fish have been implicated in ciguatera poisoning, starting with herbivores and then climbing up the food chain to the larger carnivorous fish. Species of fish most frequently implicated include groupers, amberjack, red snappers, eel, sea bass, barracuda, and Spanish mackerel. Fish larger than 2 kg contain significant amounts of toxin and readily produce toxic effects when ingested. Although not completely reliable, an immunoassay and mouse biologic assay are available for detection of ciguatoxin in affected fish. Ciguatoxin and other similar toxins are heat stable and lipid soluble; they are unaffected by temperature, gastric acid, or cooking method. Presence of toxin does not affect odor, color, or taste of the fish. Ciguatoxin produces toxic effects by activation of voltage-dependent sodium channels, resulting in hyperexcitability, decreased conduction, and prolonged refractoriness. Effects are most pronounced on neuronal, cardiac, and GI tissues.

29 Every coastal state has reported major blooms
Blooms may be responsible for more than $1 billion in losses during the last two decades

30 What causes HABs? Marine transportation may have contributed to the global HAB expansion by transporting toxic species in ballast water aquaculture activities may be related to HAB expansion Increased nutrient loads to coastal waters may stimulate HAB species populations to initiate a bloom A large sediment plume can be seen flowing down the western edge of Lagoa dos Patos and out to sea through the inlet by Rio Grande in southernmost Brazil. Phytoplankton blooms seen offshore my be partly supported by nutrients contained in the turbid runoff. Also visible in this SeaWiFS image are Lagoa Mirim, Lagoa Mangueira, and Laguna Negra (in Uruguay). A large sediment plume flowing out to sea and associated phytoplankton bloom offshore. Brazil, 2000.


32 Sources

Download ppt "Dinoflagellates."

Similar presentations

Ads by Google