In some groups of animals, the body cavity is reduced and filled with blood, thus it is called haemocoel.
It is found where the hemolymph circulates.
The animals belonging to phylum Arthropoda and Mollusca have haemocoel.
The haemocoel can act as a hydrostatic skeleton.
It functions as the circulatory system in insects.
Function:
Insects do not have arrangement of blood vessel as found in mammals.
So, instead of these blood vessels, insects have a cavity which is full of insect blood.
This insect blood is known as hemolymph.
Their organs are suspended in this cavity which means that the organs do not have a particular supply of blood but these organs are suspended in the blood and receives the nutrients as the blood washed around the organs.