Question

VFDF is produced by
A. Lyngbya
B. Microcystis
C. Aulosira
D. Tolypothrix

Answer 1

Hint: VFDF is a very fast death factor.
Anatoxin is a neurotoxic cyanobacterial toxin.
Cyanobacterial blooms cause very fast deaths in animals.
The causing agents were known as very fast death factors.
It was the first cyanobacterial toxin which was chemically and functionally defined in 1972.

Complete answer:
Anatoxin is also known as Very Fast Death Factor (VFDF)
It is a secondary, bicyclic amine alkaloid and cyanotoxin having neurotoxicity.
Symptoms of anatoxin exposure include
1. Loss of coordination
2. Muscular fasciculations
3. Convulsions
4. Death by respiratory paralysis.
Its mode of action is through the nicotinic acetylcholine receptor Due to its high toxicity and presence in drinking water poses a threat to animals, including human beings.
Anatoxin is not to be confused with guanitoxin which is also a potent cyanotoxin.
It has a similar mechanism of action to that of anatoxin but is structurally unrelated.
Lyngbya: It is a neurotoxin.
It causes severe overstimulation of respiratory muscles.
This ultimately can result in death.
Microcystis: It is a genus of freshwater cyanobacteria.
It is also neurotoxic in nature.
Aulosira: It is a species of cyanobacteria found in a variety of environmental neeches.
Tolypothrix: It is a genus of cyanobacteria that occurs in small tufts which are either floating in torpid water or attached to plants and rocks.

So, the correct option is option A. lyngbya.

Note: Anatoxin is unstable in water and other natural conditions, and in the presence of UV light undergoes photodegradation, being converted to the non-toxic products dihydro anatoxin and epoxy anatoxin.
The photodegradation of anatoxin is dependent on pH and sunlight intensity but independent of oxygen, indicating that the degradation by light is not achieved through the process of photo-oxidation.