Animals without Alimentary Canal but Possessing Digestion

Digestion is a process that breaks down complex food molecules into simpler ones that can be absorbed and utilized by the body. While most animals have an alimentary canal, which is a tube-like structure that runs from the mouth to the anus, there are some animals that do not have this structure but still possess digestion.

Examples of Animals without Alimentary Canal

1. Flatworms - Flatworms, also known as Platyhelminthes, are a phylum of animals that do not have an alimentary canal. Instead, they have a mouth that leads to a gastrovascular cavity, which acts as both a mouth and a stomach. The cavity has only one opening that serves as both the mouth and the anus.

2. Cnidarians - Cnidarians, such as jellyfish and corals, have a simple digestive system that consists of a gastrovascular cavity. Like flatworms, they have a mouth that leads to the cavity, which has only one opening that serves as both the mouth and the anus.

3. Porifera - Porifera, also known as sponges, have a simple digestive system that consists of collar cells, which are specialized cells that filter food particles from the water. The food is then digested within the cells.

How They Digest Food Without Alimentary Canal

Animals without an alimentary canal use various mechanisms to digest food.

1. Gastrovascular cavity - The gastrovascular cavity of flatworms and cnidarians is lined with cells that secrete digestive enzymes. The enzymes break down the food into simpler molecules that can be absorbed by the cells lining the cavity.

2. Collar cells - The collar cells of porifera filter food particles from the water and digest them within the cells.

3. Extracellular digestion - Some animals, such as sea urchins, use extracellular digestion, where digestive enzymes are secreted outside the body to break down food particles. The broken-down food is then absorbed by the cells.

Conclusion

While most animals have an alimentary canal, there are some animals that possess digestion without this structure. Flatworms, cnidarians, and porifera have developed unique mechanisms to digest food without the need for an alimentary canal.

Jelly fish is a coelenterate and lack alimentary canal but posses digestion...