Ciguatera Dinoflagellate
(Gambierdiscus toxicus)
Domain: Eukaryota
Kingdom: chromalveolata
Phylum: Dinoflagellata
Class: Dinophyceae
Order: Goyaulacales
Family: Goniodomataceae
Genus: Gambeirdiscus
Species: G.toxicus
Author: Adachi and Fukuyo, 1979
Gambierdiscus
toxicus is an armoured marine benthic and toxic
dinoflagellate that is known for affecting tropical reef ecosystem. It was first
discovered in Gambier Islands of French Polynesia and since this toxin
producing dinoflagellate is in discoid shape it is termed as Gambierdiscus toxicus. They are
distributed in reef areas of Pacific and Indian Oceans especially in the tide
pools and lagoons. G.toxicus is a photosynthetic cell with yellow to golden- brown
chloroplasts. This cell varies from oval to ellipsoidal shape with crescent
shape nucleus. The cell is anterio-posteriorly compressed with smooth surface
and numerous dense pores. Cell length ranges from 24-60µm in length and 42-140 µm in transdiameter. They grow as epiphytes (Plant
that grows on another plant) in macroalgae and dead corals. Each strain of G.toxicus prefers different algae
example Hawaiian strain prefers red algae (Spyridia
filamentosa). These microscopic cells reproduce asexually by binary
fission.
Controlling factors of G. toxicus distribution
 |
| Scanning electron microscopic picture of Gambierdiscus toxicus |
The distribution of G.toxicus is restricted by the following
factors. Water temperature that ranges from 25°C-29°C promotes the growth of G.toxicus. Macrophytes(Algae) and
biofilms acts as good substrate for G.toxicus to attach. Water with low to
moderate turbidity and stable salinity of 33 ppt creates a suitable condition
for G.toxicus to multiply. It prefers
only low light intensity for growth (Ten percent of incident ray is enough for
this dinoflagellate to bloom) and it shades itself under substrate(Macro algae) in high
light environment. All the above environmental factors also promote coral reef formation.
The density of the G.toxicus is
associated with physio-chemical parameters of coral reef ecosystem. Hence, both
coral reef and G.toxicus overlaps, this yields a way for this
toxic dinoflagellate to enter in the food chain of coral reef fishes. But, in
some cases these cells also exist in macrophyte abundant area where the reef is
completely absent (NE Coast of Australia).
G.toxicus vs human
They are known for
producing toxins such as cigua toxin, maitotoxin and gambeir toxin that
accumulates in the fish and transfers from one fish (Herbivores) to another
(carnivores) through a process called bio magnification. It also changes the behavior and suppresses the immunity of fish that leads disease proliferation.
It affects around 400 species of fish especially, fishes belonging to
scombridae including high commercial value fishes such as Tuna and Seer fish. It
causes ciguatera (Ciguatera Fish poisoning) to humans who consumed the affected
fishes. Symptoms includes Nausea, vomiting, muscle pain, numbness, tingling and
one of the peculiar symptoms of this disease is cold allodynia (cold Burning
sensation). The people in contact with cold substance feel burning sensation.
The toxin is odour less, tasteless and heat resistant; so it doesn't detoxify
while cooking.
Acknowledgement
Pictures and information were collected from the following links
Acknowledgement
Pictures and information were collected from the following links
https://www.e-education.psu.edu/earth103/node/718
