The Phylum Echinodermata is a phylum that consists of marine animals. They are found at varying ocean depths - from the top to the deep abyss. Some examples of them are starfish, brittle stars, sand dollars, sea cucumbers, and many more. Echinodermata move, live, and respire in almost all the same ways. Most live towards the bottom of the ocean, and use things like the herbal system to respire. Although there are some differences, they evolved closely together.
Brittle Stars, similar to starfish, are part of the Phylum Echinodermata. The gas exchange inside of a brittle star occur through sacs called bursae (lined cilia). There are approximately 10 bursae in a brittle star. Water flows through them by the muscle contractions or cilia. Also, the Hemal System, a series of sinuses and vessels, transport oxygen through the sea creature. The brittle star has a very unique way of respiring, however it is similar to animals in the same phylum.
Starfish/Sea Stars are probably the most well known type of Echinodermata today. It has a different way of respiring than others. It occurs through the tube feet, and through the dots on the body surface called papillae. They reach through the muscular body wall and then to the water they are in. Oxygen from the water goes into and through the starfishes' body by the fluid in the main body cavity. Like the Brittle Stars, the Hemal System (a series of sinuses and vessels) may and usually does play a role in a starfish's respiration.
Sea Cucumbers are also part of the Phylum Echinodermata. Sea cucumbers basically breathe through their anus. They extract oxygen from water through a pair of respiratory trees (also act as execratory organs too), which are located in their anus, therefore making them breathe through there all the time. The gas exchange occurs through the walls of the tubules, from and to the fluid of the main body cavity. As we can observe, the sea cucumbers most likely have the most strange and unique way of breathing, than any other sea creature or animal.