Octopus: Instead of one or two hearts, octopuses have three hearts. Two of the hearts perform the same function, while the third evolved for a different reason.
Squid: Like octopuses, squids also evolved three hearts. Its systemic heart pumps blood around its body, while its two branchial hearts pump oxygen through its gills.
Hagfish: ranks highly among the animals that have multiple hearts in terms of its sheer bizarreness. An eel-shaped, slimy fish, the hagfish is the only known extant animal to possess a skull.
Unlike most mollusks, cuttlefish possess a closed circulatory system. Like squids and octopuses, cuttlefish have three hearts. Their hearts operate similarly to their fellow cephalopods.
Earthworm: Last amongst the animals that have multiple hearts, earthworms don’t actually have a heart. Instead, they have a heart-like system called an aortic arch.