Final answer:
The colossal squid is the world's largest mollusk, reaching lengths of up to 50 feet. It differs from the Humboldt squid, which can grow up to 7 feet long and is known for its group hunting behavior and ability to live in deep ocean zones.
Step-by-step explanation:
The world's largest mollusk is the colossal squid. On average, a colossal squid measures around 14 feet in length, but some individuals can grow to be almost 50 feet long, making them one of the largest invertebrates. In contrast to the massive size of the colossal squid, the smallest mollusks are microscopic snails.
The colossal squid should not be confused with the Humboldt squid, which is another large marine invertebrate found in the Pacific Ocean. The Humboldt squid can grow up to 7 feet long and is known for its aggressive behavior and hunting in packs of up to 1,000 or more. They live at depths between 600 and 2,000 feet, in the oxygen-minimum zone, and have been observed moving north from their traditional habitat near South America to as far as Alaska.