Question

Classify the following organisms based on the absence/presence of true coelom (i.e., acoelomate, pseudocoelomate and coelomate) - Spongilla, sea anemone, Planaria, Liver fluke, Wuchereria, Ascaris, Nereis, earthworm, scorpion, birds, fishes, horse.

Answer 1

Coelom:

1. One of the distinguishing characteristics of metazoans is the coelom.
2. The real coelom is a bodily cavity created by the three germinal layers during embryo development.
3. Mesodermal epithelium cells border the coelom.
4. One of the criteria for classifying animals is the presence or lack of coelom.

Acoelomates:

1. An acoelomate is an animal that lacks a bodily cavity.
2. Acoelomates, unlike coelomates, lack a fluid-filled space between the body wall and the digestive tract.
3. The coelom is not present.
4. Mesoderm has entirely taken over the blastocoel.
5. Porifera, Coelenterata, and Flatworms are examples (Platyhelminthes). Only spongocoel or coelenteron are present.

Pseudocoelomates:

1. The Aschelminthes, which are closely connected to the Platyhelminthes, is a defunct phylum of pseudocoelomate and other similar animals that are no longer regarded as closely related and have been promoted to their phyla.
   True coelom does not exist. Mesodermal cells partially fill the blastocoel.
2. Mesoderm lines the body cavity only towards the body wall; mesoderm does not line the gut.
3. e.g- Roundworms(Aschelminthes).

Coelomates:

1. Animals with a real coelom are called coelomates.
2. Mesoderm lines the coelom on both sides, towards the body wall and the stomach.
3. Eueoelomate condition refers to the presence of a coelomic cavity lined with coelomic epithelium.
4. For instance, Arthropoda.
   

Acoelomate	Spongilla Sea anemone Planaria Liver fluke
Pseudocoelomate	Wuchereria Ascaris
Coelomate	Nereis Scorpion Earthworm Birds, Fishes and Horse