Presentation on theme: "Dinoflagellates. Introduction Dinoflagellates are unicellular, flagellated protists –The first modern dinoflagellate was described by Baker in 1753 –The."— Presentation transcript:
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
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
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 Karina brevis
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 Sulcus
Structure There are three basic cell extensions: –Lists –Horns –Spines Horns
Cell Biology The cytoplasm of dinoflagellates contains typical eukaryotic organelles Dinoflagellates may also contain one or several distinctive organelles –pusule –eyespot –ocellus –chloroplasts
Cell Biology The dinoflagellate nucleus is unusual: –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.
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. Ceratium furca
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
Pfiesteria piscicida life cycle
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. Phytoplankton bloom in near Svalbard in Barents Sea, Aug 13, 2002
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) mixotrophic dinoflagellate Ceratium furca
Ecology Some dinoflagellates are predators and feed on bacteria, phytoplankton and smaller dinoflagellates Some target larger prey, such as copepods, crustaceans and fish Ingestion of cryptophytes by G. galatheanum, brightfield (movie)
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 Symbiodinium microadriaticum
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
Oblique Coral, Vadoo Diving Paradise, Maldives, Feb 1997 Oblique Coral, Vadoo Diving Paradise, Maldives, Dec 1997 Oblique Coral, Vadoo Diving Paradise, Maldives, Mar 1999
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. Blue crab cardiac tissue infected with Hematodinium spp.
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. Model of circadian rhythm
Significance Primary Producers –Important primary producers in both marine (particularly on-shore) and freshwater environments
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
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 Florida Red Tide Bloom of Gymnodinium breve
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.
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
Pfiesteria piscicida lesions on crab and fish
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.
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
Every coastal state has reported major blooms Blooms may be responsible for more than $1 billion in losses during the last two decades
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 flowing out to sea and associated phytoplankton bloom offshore. Brazil, 2000.