How do branchiopods use bristles to sense touch and chemicals?

Branchiopods utilize specialized hairlike processes known as setae to detect environmental stimuli, functioning as their primary organs for touch and taste.1

These bristles are connected to a nerve supply at their base, which allows them to function as follows:

• Mechanoreception (Touch): The setae act as tactile receptors. When these bristles are deflected by contact with solid objects or movement, the physical stimulus is relayed through the connected nerves, providing the animal with sensory information about its surroundings.21
• Chemoreception (Taste): Other setae are specialized for detecting chemical substances. These chemosensory bristles are typically thin-walled and tubular in form, sometimes featuring a small pore at the tip to facilitate the detection of a wide range of chemicals.21

These receptors are particularly abundant on the trunk limbs of certain branchiopods, such as notostracans. This distribution helps the animals effectively sort edible material from inedible debris while they forage in the mud at the bottom of pools.1