The red color of earthworm blood is due to a pigment called hemoglobin. Hemoglobin is an iron-containing protein found in the red blood cells of many organisms, including humans and earthworms. It plays a crucial role in the transportation of oxygen throughout the body.

**Hemoglobin Structure and Function:**
Hemoglobin is composed of four protein chains called globins, each of which is associated with a heme group. The heme group contains iron atoms that bind to oxygen molecules. This binding allows hemoglobin to efficiently transport oxygen from the respiratory organs to the body tissues.

**Why is Earthworm Blood Red?**
The red color of earthworm blood is a result of the iron in the hemoglobin molecule. When oxygen binds to the iron atoms in the heme group, it forms a bright red compound known as oxyhemoglobin. This gives the blood its characteristic red color. When oxygen is released from hemoglobin, it becomes deoxygenated and turns a darker shade of red.

**The Role of Hemoglobin in Earthworms:**
Earthworms rely on hemoglobin to transport oxygen in their blood, just like humans and other animals. However, earthworms have a slightly different circulatory system compared to vertebrates. They have a closed circulatory system, where blood is contained within vessels and does not freely flow through body cavities.

In earthworms, the blood, which is red due to hemoglobin, flows through a dorsal blood vessel and is pumped by the hearts to various body parts. Oxygen is absorbed through the moist skin of the earthworm, and it diffuses into the blood vessels, binding to hemoglobin. The oxygenated blood is then transported to different tissues, where oxygen is released for cellular respiration.

**Conclusion:**
The red color of earthworm blood is attributed to the presence of hemoglobin, an iron-containing protein. Hemoglobin binds to oxygen, allowing it to efficiently transport oxygen throughout the earthworm's body. This pigment is vital for the earthworm's respiration process, ensuring the delivery of oxygen to its tissues.

the earthworm blood colour is red because of containing haemoglobin (red containing oxygeneted pigment )but haemoglobin it does not contain corpuscles in vertebrate but it is found in dissolved plasma