Question
Biology Question on earthworm
Photoreceptors of earthworm occur on
A
clitellum
B
many eyes
C
dorsal surface
D
lateral sides.
Answer
dorsal surface
Explanation
Solution
Photo-receptors restricted only to dorsal surface, are more numerous on prostomium and peristomium of earthworm and gradually reduce in number towards posterior end of body. They are totally absent in clitellum. Each photoreceptor consists of a single ovoid cell, with a nucleus and clear cytoplasm containing a network of neurofibrillae and a small transparent L-shaped lens or optic organelle or phaosome, made up of a hyaline substance. Photoreceptors enable worms to judge the intensity and duration of light.