Question

How many hearts are present in the blood vascular system of Pheretima posthuma?

• A. 6 pairs
• B. 2 pairs
• C. 1 pairs
• D. 4 pairs

Answer 1

The correct option is D 4 pairs

• 4 pairs of the heart are present in the earthworm. The blood vascular system is a closed type. Blood contains haemoglobin dissolved in plasma. There are many types of corpuscles which are colourless and nucleated. There are two longitudinal blood vessels, the dorsal and the ventral running on the dorsal and ventral sides of the gut.
• Another longitudinal vessel, the subneural vessel, runs longitudinally below the nerve cord and splits into two, the two branches running on the lateral side of the stomach, oesophagus and pharynx.
• The dorsal and ventral vessels are connected to each other in segments 7, 9, 12 and 13 by means of paired pulsatile hearts. The hearts in 12${}^{th}$ and 13${}^{th}$ segments are called as lateral oesophageal hearts while the anterior pairs in the 7${}^{th}$ and 9${}^{th}$ segments are called as lateral hearts.
• There are also two pairs of non-pulsatile loops in segments 10 and 11, which connect the supra-oesophageal vessel to the lateral oesophageal vessels.

Therefore, the correct answer is option D.