How do the trunk limbs of branchiopods help them feed?

The trunk limbs of branchiopods are essential structures that facilitate feeding through a coordinated series of movements. In most species, these limbs act together to filter, scrape, or otherwise collect food particles from the environment.1

Once gathered, the limbs transport these particles into a ventral food groove, which directs the food toward the animal's mouth. While the primitive branchiopod limb functions as a multipurpose flap for locomotion, respiration, and feeding, many species utilize these flattened, paddlelike appendages specifically for filter feeding.12

The limbs are capable of complex movement due to intrinsic musculature that allows different parts of the limb to move relative to one another, while extrinsic muscles at the base of the limbs control the movement of the entire structure. In some specialized groups, such as the infraorders Onychopoda and Haplopoda, the trunk limbs have evolved away from filter feeding and are instead specialized for grasping prey.12