Question

The animal with haemocoel is
A. Hydra
B. Leucosolenia
C. Centipede
D. Earthworm

Answer 1

Hint: Haemocoel is the body cavity present in many invertebrates such as arthropods and molluscs. Haemocoel helps in the circulation of blood which is known as haemolymph.

Complete answer:
• Mammals including humans have a well-developed circulatory system. The circulatory system in mammals is called a closed circulatory system in which the blood is supplied to different body organs via blood vessels.
• Invertebrates like arthropods and molluscs do not have a well developed circulatory system like mammals. Instead they have a body cavity that is filled with blood. The body cavity is known as haemocoel and the blood is known as haemolymph. Haemocoel is present between different body organs in such a way that the body organs are suspended within this cavity.
• As the body organs are suspended in haemocoel, the haemolymph while flowing through the haemocoel continuously washes these organs providing nutrients to them i.e. the body organs are in direct contact with hemolymph. Such type of circulation is known as open circulation and the system is known as an open circulatory system.
• Haemocoel is found in the organisms belonging to Phylum Arthropoda and Mollusca.
• Hydra does not contain haemocoel as it belongs to Phylum Cnidaria.
• Leucosolenia belongs to Phylum Porifera, hence does not contain haemocoel.
• Haemocoel is also absent in earthworms, as it belongs to Phylum Annelida.
• Haemocoel is present in Centipede, as it belongs to Phylum Arthropoda.

Hence, the correct answer is option (C).

Note: Haemocoel is a body cavity present in the animals belonging to Phylum Arthropoda and Phylum Mollusca. Centipede shows haemocoel as it is an arthropod. Centipede has an elongated and segmented body with 15 to 177 pairs of legs. Due to the presence of large numbers of legs, it is commonly called ‘hundred legger’.