Question

The lateral hearts in earthworm are situated in
a. segments 7 and 9
b. segments 6 and 8
c. segments 8 and 10
d. segments 6 and 11

Answer 1

Hint: Earthworm falls under the phylum Annelida and of kingdom Animalia. Some common species of earthworm are Pheretima posthuma and Lumbricus. Earthworm is a terrestrial animal of deep brown and reddish brown colour.

Complete answer:
Pheretima exhibits the close type of blood vascular system. It comprises heart and blood vessels. In earthworms, there are four pairs of tubular hearts. These hearts are enlarged, thick walled pulsatile and provided with valves.

The anterior pair of two hearts known as lateral hearts. These lateral hearts lie in the 7 and 9 segments. They connect the dorsal blood vessel with the ventral blood vessel.

The two posterior pairs of hearts are called latero-esophageal hearts are situated in the 12 and 13 segments. They are thick, muscular and contractile vertical vessels. Anterior loops are a pair of thin walled, non pulsatile vessels without valves in each 10 and 11 segments.

Blood vessels are well organized vessels which run all along the body of earthworms. There are two types of blood vessels found in earthworm:
- Dorsal blood vessel: It is the largest blood vessel. It has valves which prevent the backflow of blood and it receives blood from various parts of the body.
- Ventral blood vessel: It also extends from one end to the other end of the body. It does not have any valve and flow of blood is from anterior to the posterior end of the body. It is the main distributing blood vessel.

Hence, the correct answer is option (A).

Note: From the above solution we came to know that the circulatory system is closed type and blood is red in earthworms and it contains leukocytes. The haemoglobin is dissolved in the blood plasma.