Question

The clitellum of Pheretima is present in the segment
a. 12, 13 and 14
b. 13, 14 and 15
c. 14, 15 and 16
d. 15, 16 and 17

Answer 1

Hint: Earthworms are the terrestrial invertebrates that are found on the upper layer of the moist soil which are mostly reddish-brown. The clitellum is a part of an Earthworm’s anatomy. They are most commonly found in the Phylum Annelida.

Complete step by step answer:
Let’s discuss the above options and find the correct answer:
- 12, 13, and 14: The stomach of the earthworm extends from segment 9 to segment 14. They use decaying leaves mixed with organic matter which is present in the soil. The calciferous gland which is present in the stomach helps to neutralize the humic acid present in humus.
- 13, 14, and 15: The stomach continues up to segment 14 and from segment 15 onwards the intestine originates and it continues till the last segment of the body.
- 14, 15, and 16: The `segment 14 to segment 16 is covered by an important dark brown coloured glandular tissue known as clitellum. The clitellum is the identifying character of the worms. The clitellum is the reproductive part of the clitellates. The clitellum is mostly found in the sexually mature earthworms.
- 15, 16, and 17: The segments from 15 to the last segments of the body continue in the intestine. The characteristics of the intestine are that from segment 23 to segment 25 there is a presence of a dorsal wall known as typhlosole.
Hence, the correct option is C.

Note: The clitellum is found mostly in the mature earthworms and when it is orange in colour then male or female earthworms are ready for mating. The clitellum helps in the secretion of viscous fluids and it also helps in the production of mucus.