Question

How many pairs of spiracles are present in the thorax region of cockroaches?

Answer 1

A spiracle or stigma is the opening in the exoskeletons of insects and some more derived spiders to allow air to enter the trachea.

Complete Answer:
Spiracle- A spiracle is an organ for respiration in insects. It is an opening found on the endoskeleton of an insect and is usually paired and present on the thorax and abdomen.
Cockroaches come in the class Insecta of phylum Arthropoda. They have long antennae, legs and a flat extension of the upper body that covers the head. They are nocturnal omnivores and are considered as pests and vectors for several diseases.
In cockroaches, the respiratory organ is the tracheal system. It has two important parts:
Spiracles: When air enters into the respiratory organs through external openings, spiracles act as muscular valves opening way to the internal respiratory system. Cockroaches have 10 pairs of spiracles in their body. Their opening is regulated by spiracles. Air is drawn in when sphincters open and when they close, air does not enter.
Trachea: The trachea is a tubular structure for conducting the air. Networks of trachea work together for respiration in cockroaches. Trachea is further divided into fine tubules called tracheoles which have tracheal fluid at their tips.
Oxygen enters through spiracles and through trachea, reaches the tracheal fluid. The tracheal tip is connected to the body tissues and CO2 diffuses into the tracheal fluid due to partial pressure difference. Oxygen diffuses into the tissues. Carbon dioxide moves through the trachea and is released out of the spiracle.
A total of 10 spiracles are present in cockroaches. The abdominal region has 8 pairs and thoracic has 2 pairs of spiracles. Hence, the correct option is option B, ‘2’.

Hence the correct option is option D, ‘Public preference for organic vegetables’.

Note: The function of spiracles is linked to respiration, helping oxygen to reach internal respiratory organs, such as lungs in whales and tracheae in insects.Spiracles, along with trachea and tracheoles make up the respiratory system of cockroaches.