Animals Without Hearts
Starfish (Asteroidea) The starfish belongs to the class Asteroidea. As the name shows, the starfish is shaped like a star. They can also be called asteroids, though not because of any resemblance with actual asteroids. There are around 1,900 species found in oceans worldwide.
Coral (Cnidaria) The coral is of the Cnidaria phylum and the Anthozoa subphylum, inhabiting tropical oceans.They are known to form colonies and also get hard skeletons from calcium carbonate. Similar to starfish, corals don’t circulate blood. It rather circulates fluid, which doesn’t require a heart.
Portuguese Man o’ War (Physalia physalis) The Portuguese man o’ war is also simply known as the man-of-war, living both in the Atlantic Ocean and the Indian ocean. It belongs to the genus Physalia, the only species within. The genus itself falls under the family Physallidae, the only genus within.
Sand Dollar (Clypeasteroida) The sand dollar goes by other names like the sea cookie and the snapper biscuit. It belongs to the order Clypeasteroida, which is described as having varying levels of flat. They are related to sea urchins. Sand dollars live at the bottom of the ocean and burrow into the soil. They also don’t need a heart and use vascular systems.
Sea Urchin (Echinoidea) The relative of sand dollars is also an animal with no heart. It falls under the class Echinoidea comprising 950 species. The sea urchin is found in every ocean, living on the sea bed. It is described as having spiny shells.
Flatworm (Platyhelminthes) The flatworm is the common term for the phylum Platyhelminthes, all of which are invertebrates. It is described as having a flat, soft body, which explains the name. There are 4,500 species. Flatworms don’t have respiratory or circulatory systems, which is where the flat structure helps.
Sea Cucumber (Holothuroidea) The sea cucumber is under the Holothuroidea class, a group of aquatic animals that are described as having leathery skin and a long body like an actual cucumber. There are around 1,717 species spread around the world. They can be eaten by humans.
Sea Lilies (Crinoidea) The sea lily is also termed the crinoid, comprising the class Crinoidea Crinoids are under the same Echinodermata phylum as starfish, sea urchins, and brittle stars. Crinoids were numerous but have now reduced to around 500 species.
Sea Anemone (Actinaria) The sea anemone is an order of marine animals called Actiniaria. The common name is from a beautiful terrestrial plant known as the Anemone. It falls under the order Cnidaria and is related to corals and jellyfish. It lives under a rock.