Question

Photoreceptors of Earthworm occur on

• A. Clitellum
• B. Anal segment
• C. Dorsal surface
• D. Lateral sides

Answer 1

Answer: (C)

Dorsal surface

Earthworms do not have eyes they do have specialized photosensitive cells called "light cells of Hess". These photoreceptor cells have a central intracellular cavity (phaosome) filled with microvilli. As well as the microvilli, there are several sensory cilia in the phaosome which are structurally independent of the microvilli. The photoreceptors are distributed in most parts of the epidermis but are more concentrated on the back and sides of the worm. Hence, photoreceptors are present on the dorsal surface.

So the correct answer is 'Dorsal surface'.