Question

Which animal has three hearts?

Answer 1

Many phyla have circulatory systems for the transport of materials in the body. This system consists of a fluid tissue called blood, which may circulate in tubes called blood vessels or in spaces called sinuses. The force for the circulation of blood is provided by muscular contractile hearts.

Complete Answer-
The circulatory system is of two types – open and closed. The open type found in molluscs. The body cavity of these animals, therefore, remains filled with the blood and is known as haemocoel.
Octopus has three hearts. It belongs to the class Cephalopoda which belongs to the phylum Mollusca. It inhabits the bottom of the sea in a nest made of stones. It is carnivorous and kills the prey with its poisonous saliva. It has a good learning power and can be trained to show manipulative skills. Two branchial hearts of Octopus help to pump the deoxygenated blood to the gills and for the circulation of oxygenated or oxygen-rich blood to the rest of the body, a third systemic heart is used. The blood is bluish in colour due to the presence of copper containing pigment haemocyanin in plasma.
These are also fast swimmers but they prefer to crawl more than swim because during swimming the systemic heart becomes inactive and not able to transport oxygen-rich blood to the whole rest and this makes them exhausted very soon.

Note-
Cephalopods are active predators and most of these are without an outer protective shell. Some of them are invertebrates. The foot and head regions are combined into a bearing eye and 8 to 10 tentacles with numerous suction cups. Some evade the predators by releasing a cloud of black ink-like material. This alters the sensory functions of the predator temporarily.