How do bacterial toxins kill mosquito larvae?

• A. They create ulcers in the gut, or digestive system, of mosquito larvae.
• B. They paralyze the larvae by nerve damage.
• C. They cause immediate death upon contact.
• D. They destroy the exoskeleton.

Answer: (A)

Bacterial toxins used against mosquito larvae act by being ingested and then harming the gut. When larvae feed, they swallow the toxin crystals, which are activated in the gut and disrupt the intestinal cells. This damage, often described as gut ulcers or severe tissue injury, prevents proper digestion and nutrient absorption, leading to starvation and death of the larvae. This mechanism relies on ingestion and gut damage, not nerve paralysis, immediate contact kill, or destruction of the exoskeleton, which is why this option best fits how these toxins work.