Question

In which animal, blood is red but blood corpuscles are absent?
A. Cockroach
B. Earthworm
C. Birds
D. Bedbug

Answer 1

Hint: Blood is a form of liquid that runs in the body of mostly all the organisms but in some animals, it is not particularly red in colour as the red colour of blood is due to the presence of RBCs.

Complete answer:
In earthworm, the blood vascular system is a closed type one. The colour of the earthworm’s blood is red in colour and haemoglobin is found to be dissolved in the plasma of blood. RBCs (red blood cells) are absent in them. For the circulation of blood, they have three major blood vessels namely: aortic arches, dorsal blood vessels, and ventral blood vessels. Earthworms have coelomic fluid which is alkaline in nature, colourless fluid containing water, also some proteins and corpuscles. Haemoglobin is not present in coelomic fluid. It is found to be dissolved in the plasma of blood providing the red colour to the blood.
Earthworms have modified external fertilization. Earthworms are hermaphrodite means they have both male and female reproductive organs. They cannot reproduce alone. For the successful reproduction to occur, they must mate in pairs with another earthworm. Each hermaphroditic earthworm exchanges their sperm with one another after the process of coupling, a cocoon is made by the earthworm externally to their clitellum.
Hence, the correct answer is Option (B).

Note: Flatworms, nematodes, cnidarians do not have a circulatory system and that’s why they do not have blood. They have no lining or fluid in their body cavity. Ants and other insects have a type of liquid inside their body that helps them to move the nutrients around.