Final answer:
Acorn worms have a larval stage called 'nauplius' which is aquatic and has head appendages for swimming. This larva is different from the adult stage and has specific characteristics and behaviors. It is mainly a predator, scavenger, or filter feeder.
Step-by-step explanation:
Acorn worms have a unique larval stage called 'nauplius'. This larval stage is mainly aquatic and has head appendages for swimming. It is different from the other stages of the acorn worm's life cycle, such as the adult stage. The larva of the acorn worm is mainly a predator, scavenger, or filter feeder, and it has two pairs of antennae and claws for hunting.