Question

Brown colour of earthworm is due to
A. Melanin
B. Porphyrin
C. Haemoglobin
D. Both A and B

Answer 1

Hint: Earthworm is a terrestrial invertebrate that belongs to phylum Annelida. Their body is characterised by concentric tubes construction. They have external segments called annuli along with the corresponding internal segment. These segments are covered with Setae which helps in the movement of the earthworm.

Complete Answer:
- As invertebrates, earthworms do not have the true skeleton system. They have a hydrostatic skeleton system that has a fluid filled coelom chamber. Earthworms are usually reddish brown in colour. Their dorsal surface is darker compared to the ventral side.
- The dorsal surface has a dark median mid dorsal line due to the dorsal blood vessel along the longitudinal axis of the body.
- Earthworms are dark brown in colour due to the presence of porphyrin pigment. It protects their body from the harmful UV rays of the sun. Porphyrin is scattered across the circular muscles of the earthworm.

Therefore the correct answer is option (B) Porphyrin.

Additional information: Earthworms do not have specialized respiratory systems. They respire through their skin. They have an internal median fold of intestine or dorsal wall which increases the surface area of the intestine which inurn helps in the absorption of more nutrients.

Note: Earthworms do not have RBCs but they have a blood pigment called haemocyanin that helps to circulate the oxygen throughout the body similar to haemoglobin. Haemocyanin is reddish blue in color when oxygenated and colorless without oxygen content.