What is the item required to summon the boss Duke Fishron in the game Terraria?

In the game Terraria, the item required to summon the boss Duke Fishron is the Truffle Worm. This rare critter can be found in the underground Mushroom Biome after defeating Plantera. Once caught, the Truffle Worm must be used as bait for Fishing in an Ocean biome, specifically in the space above the surface. Using any other type of bait will cause the worm to flee, so it is essential to release it into the water with the appropriate fishing rod equipped. Duke Fishron will then be summoned, ready for a challenging battle against this ferocious aquatic boss.