Dinoflagellates

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Dinoflagellates
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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

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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

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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
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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
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Structure

• There are three basic cell extensions
• Lists
• Horns
• Spines

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Cell Biology

• The cytoplasm of dinoflagellates contains typical
  eukaryotic organelles
• Dinoflagellates may also contain one or several
  distinctive organelles
• pusule
• eyespot
• ocellus
• chloroplasts

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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.
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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
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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

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Pfiesteria piscicida life cycle
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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
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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
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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)
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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
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• 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

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Oblique Coral, Vadoo Diving Paradise, Maldives,
Feb 1997
Oblique Coral, Vadoo Diving Paradise, Maldives,
Dec 1997
Oblique Coral, Vadoo Diving Paradise, Maldives,
Mar 1999
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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.
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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
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Noctiluca spp.
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Significance

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

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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

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• 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.

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• 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

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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.

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• 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

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

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• 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.
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Sources

• http//www.nmnh.si.edu/botany/projects/dinoflag/in
  dex.htm
• http//www.ucmp.berkeley.edu/protista/dinoflagella
  ta.html
• http//www.geo.ucalgary.ca/macrae/palynology/dino
  flagellates/dinoflagellates.html
• http//en.wikipedia.org/wiki/Dinoflagellates
• http//visibleearth.nasa.gov/
• http//www.searay.50megs.com/hematod.html
• http//coral.s5.com/
• http//www.eeb.uconn.edu/Courses/EEB290/Lecture26.
  pdf
• http//www.emedicine.com/emerg/topic100.htm
• http//www.habhrca.noaa.gov/
• http//www.habhrca.noaa.gov/habfacts.html
• http//ioc.unesco.org/hab/intro.htm
• http//www.sustainablefishery.org/index.html
• http//geo.ucalgary.ca/macrae/Dinoflag_spindles.g
  if
• http//www.lochness.co.uk/exhibition/dinoflagellat
  es.html