What is paxillae?

Paxillae are small, hair-like projections found on the bodies of certain marine animals, particularly in the phylum Echinodermata. They are often found in the arms of starfish and brittle stars, and play a role in their respiratory and feeding systems.

Paxillae are formed by specialized cells called podia, which are able to extend and retract to manipulate food particles and water flow. The paxillae also contain sensory cells that help the animal to detect their surroundings.

In some species, such as the sand dollar, the paxillae are covered in a sticky mucus that traps particles of food and helps the animal to digest them. In others, such as the sea urchin, the paxillae are used for respiration, helping to circulate water over the animal's gills and remove waste products.

Overall, paxillae are an important adaptation for marine animals that need to filter feed or extract oxygen from the water. They provide the animal with a greater surface area for absorption, making it easier to capture food and oxygen efficiently.