Question

In which group of animals, coelom is filled with blood?
A) Arthropoda
B) Annelida
C) Nematoda
D) Echinodermata

Answer 1

Hint: This is the largest phylum of the animal kingdom.

Complete answer:
In Arthropoda, the coelom is filled with blood. The coelom is the space between the body wall and the gut wall lined by mesoderm on both sides. A true coelom known as schizocoelom is present in Arthropoda filled with blood.

Additional Information:
A series of internal spaces present inside the body is termed as a body cavity. On the other hand, the coelom is the true body cavity referred to as a large space between the outer body wall and the inner gut wall (wall of digestive tube) filled by fluid. The visceral organs are present in coelom and are lined by mesoderm on all sides. The absence or presence of coelom in body is a very important classifying feature of animals and on this basis, they can be divided as:

Fig: Diagrammatic representation of coelom

- Coelomates: The animals in which true body cavity or coelom is present between the body wall and the gut wall are called coelomates. Example: annelids, mollusks, arthropods, echinoderms, hemichordates, and chordates.
- Pseudocoelomate: In this type of animal, the body cavity known as pseudocoelom (pseudo-false, coelom-body cavity)is not completely lined by mesoderm. In between the ectoderm and endoderm, the mesoderm is present as scattered pouches . Example: Aschelminthes.
- Acoelomates: Those animals in which the true body cavity or coelom is absent are acoelomates. Example: sponges, coelenterates, ctenophores, and platyhelminthes.

So, the correct answer is ‘Arthropoda’.

Note:
- This type of coelom is called hemocoel and the cavity is called hemocoel.
- Arthropods have an open circulatory system.