Question

Fishermen, in certain parts of the world follow a practice of beating the roots of tree along riverbanks in a manner that transfers the extract of the roots into water. This practice paralyzes fishes and makes them easy prey. The most acceptable reason for this observation is:

• A. Rotenone is released from the roots of the plants that blocks the Electron Transport Chain
• B. Heavy metal toxicity of the fishes
• C. Inhibition of dopamine synthesis
• D. Inhibition of GABA-a neurotransmitter- synthesis

Hint:

Rotenone is highly toxic to fish and insects because it easily crosses cell membranes due to its lipophilic nature. However, it is poorly absorbed by the mammalian digestive tract, making it useful as a selective piscicide.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Certain plant species produce natural secondary metabolites as defense mechanisms. When released into aquatic environments, these compounds can act as potent piscicides (fish poisons) by disrupting mitochondrial respiration.

Step 2: Detailed Explanation:
- Plants belonging to the Fabaceae family (such as Derris and Lonchocarpus species) contain high concentrations of the odorless, lipophilic compound rotenone in their roots.
- Traditional fishermen beat these roots in water to release rotenone.
- Rotenone is rapidly absorbed through the gills of fish.
- At the cellular level, rotenone is a potent inhibitor of Complex I (NADH:ubiquinone oxidoreductase) in the mitochondrial electron transport chain.
- It blocks the transfer of electrons from iron-sulfur centers to ubiquinone, preventing ATP synthesis. This deprives cells of energy and paralyzes the fish, allowing them to float to the surface for easy harvesting.

Step 3: Final Answer:
The practice releases Rotenone, which blocks the mitochondrial Electron Transport Chain in fish.