Question

Cockroach has
(a) Two types of eyes
(b) One type of eyes
(c) Three types of eyes
(d) None of the above

Answer 1

Hint: Cockroach which uses its two large compound eyes to visualize the environment actually has more than one type of eye. This kind of eye arrangement is observed in other arthropods as well.

Complete step by step answer:
- Cockroaches (Periplaneta) have two types of eyes, the simple and compound eyes. They have three simple eyes known as ocelli on their forehead and two large, sessile, black, kidney-shaped structures located on the dorsolateral sides of the head capsule.
- The group of ommatidia together constitutes compound eyes. Each compound eye is covered externally by a transparent cuticle divided into hexagonal compartments called corneal facets. A single corneal facet and all components under it is known as ommatidium.
- An eye of the cockroach contains around 2000 ommatidia.

So, the correct answer is ‘Two types of eyes’.

Additional Information:
- The ommatidium is a convex shaped lens. Under the corneal facet covering, corneagen cells or lenticular cells exist which secrete the lens. A transparent crystalline cone exists below the corneagen cells which function as a second lens. Four of the vitrellae or cone cells surround it.
- The crystalline cone is secreted by vitrellae. In contact with this cone is the rhabdome which is a spindle-shaped refractive body. The rhabdome is secreted by reticular cells.
- Ommatidia are responsible for producing mosaic vision.

Note:
- Cockroaches cannot see in red light but can visualize in green light.
- All receptors except photoreceptors of the cockroach are situated in the epidermis of the integument and are modified epidermal cells called sensilla.
- Ommatidia are also present in insects, millipedes, and crustaceans.