Sea animals without a heart are extremely rare, as a heart is a vital organ for pumping blood and providing oxygen to the body. However, there are some sea creatures that have evolved unique adaptations to survive in oxygen-deprived environments or have alternative mechanisms for circulating fluids.
Sea Sponge
Sponges are simple multicellular organisms that lack a circulatory system altogether. They rely on the constant flow of water through their bodies to obtain oxygen and nutrients and to remove waste.
Sea Cucumber
Sea cucumbers are echinoderms that can regenerate lost body parts and have a unique water vascular system. While they possess a rudimentary heart, it is not the main organ responsible for circulating fluids. Instead, the water vascular system, consisting of a network of fluid-filled canals, helps distribute nutrients, gases, and waste throughout their bodies.
Sea Star
Like sea cucumbers, sea stars (also known as starfish) are echinoderms with a water vascular system. They have a simple circulatory system that uses seawater to transport nutrients, gases, and waste. However, they lack a traditional centralised heart.
Sea Anemone
Sea anemones are marine animals that belong to the same phylum as jellyfish and corals. They lack a circulatory system and do not have a heart. They obtain oxygen and nutrients through the diffusion of gases and the absorption of dissolved organic matter from the surrounding water.
These animals may not have a conventional heart, they have adapted alternative mechanisms to survive and perform vital functions in their respective marine environments.