Question

Which of the following structures in Pheretima is correctly matched with its function?
A. Clitellum – Secretes cocoon
B. Gizzard – Absorbs digested food
C. Setae – Defense against predators
D. Typhlosole – Storage of extra nutrients

Answer 1

Hint: Pheretima is the genus name of the Earthworm. The earthworm is a member of the phylum Annelida of the order Oligochaeta. The earthworm is a farmer friend. Also, the earthworm is a hermaphrodite organism.

Complete answer: Let us look at all the options that are given to us one by one.
Statement A: Clitellum – Secretes cocoon –
The 14th, 15th, and the 16th segment of the earthworm are known as the Clitellum. All the other segments have about 200-250 pores of integumentary nephridia but the clitellar segments have 2000-2500 pores of integumentary nephridia. These are known as the jungle of nephridia. The clitellum forms the clitellar fluid which develops into the cocoon.
Statement B: Gizzard – Absorbs digested food –
The 8th segment has a gizzard. It has cuticular rings and extra circular muscle bands that crush the food.
Statement C: Setae – Defense against predators –
Setae are made up of the chitin that is present over the septa embedded in the longitudinal muscles. Setae are not found in the first, last, and the clitellum region. The arrangement of the setae on the body of an earthworm is known as the perichaetus arrangement. Setae help in the locomotion in earthworms along with the contraction and relaxation of the circular and the longitudinal muscles.
Statement D: Typhlosole – Storage of extra nutrients –
Typhlosole is the finger-like projections that are found in the 27th to 52nd segments. Typhlosole helps to increase the surface area for the absorption of the nutrients.
Thus, based on the above information we can conclude that the Clitellum-secretes cocoon is correctly matched with its function with respect to the various structures in Pheretima.
Hence, the correct answer is option (A).

Note: The clitellum part forms a liquid known as the clitellar fluid. When the clitellar fluid dries it forms the clitellar sac in which the eggs are dropped. The mucus and the albumin protein of the epidermal cells provide the stickiness to the eggs. Due to the shifting of the earthworm’s body backward, the clitellar sac reaches the spermathecal region where the sperm and the ova fuse to fertilize and form the cocoon. This cocoon passes out from the earthworm’s body into the soil where the eggs develop and form the earthworms.