Difference Between Coelom and Haemocoel

Coelom vs Haemocoel

As Coelom and Haemocoel are being two types of body cavities found in different class of animals there exist some difference between coelom and haemocoel. This article defines coelom and haemocoel briefly, and analyses the key differences between both. Most multicellular animals possess body cavities that are filled with fluids that surround their organs. These cavities have various functions. The body cavity inside the body is commonly called coelom. Not all the organisms possess coelom. The organisms that have coelom are called coelomates, whereas the organisms which do not possess coelom is called acoelomates (Porifera and Platyhelminthes). True coelom is lined by mesoderm. The organisms that have body cavity that are not mesodermal is called pseudocoelom. Haemocoel is a type of primary body cavity found in some organisms that are called haemocoelomates.

What is Coelom?

Coelom is a true perivisceral cavity that develops within the mesoderm during the embryonic development of triploblastic animals. Coelom separates mesoderm into two parts; one part is in contact with the ectoderm while the other part is in contact with endoderm. Coelomic cavity contains a fluid called coelomic fluid, which is secreted by peritoneum, a layer of mesodermal cells. Not all the animals have this true coelom. Animals who possess true coelom is known as coelomate animals.

Difference Between Coelom and Haemocoel

What is a Haemocoel?

Hoemocoel is a type of primary body cavity found in arthropods and mollusks. It is filled with blood or haemolymph. Haemolymph is composed of haemocytes and colorless plasma. Two types of haemocytes are proleucoeytes and phagocytes. Haemolymph in haemocoelis mainly used as a source of distributing and collecting nutrients and metabolic wastes and it functions as a lymph tissue. All the internal organs are surrounded by haemocoel. Two horizontal septa called diaphragm and ventral diaphragm separate haemocoel into three blood sinuses namely; pericardial sinus, perivisceral sinus and perineural sinus.

What is the difference between Coelom and Haemocoel?

• True coelom can be found in echinoderms and chordates while haemocoel is a type of primary body cavity found in arthropods and mollusks.

• The fluid inside the coelom is called coelomic fluid, whereas the fluid inside the haemocoel is called haemocoelomic fluid.

• The organisms that have coelom are called coelomates, and the organisms that have haemocoel are called haemocoelomates.


Images By: Jlesk (CC BY-SA 3.0)

Further Reading:

  1. Difference Between Coelom and Pseudocoelom