Cockroach: Respiratory, Excretory, Nervous System and Sense Organs, Practice Problems and FAQ’s

Have you ever wondered!

Why do cockroaches always come out at night? Why are they always present in dark spaces?

The answer to all these questions is that cockroaches have compound eyes. These are the specialised sense organs that help in the nocturnal vision. The compound eyes create mosaic vision. Moreover, they are a food source of many predators and due to this they hide during the day in night places. They come in search of food in the night.

Let’s understand more about the some major organ systems in cockroaches which make them adapt easily to their environment. 

Table of Contents

• Respiratory System
• Excretory System
• Nervous System
• Sense Organs
• Practice Problems of Cockroaches
• FAQs of Cockroaches

Respiratory System

The respiratory system of cockroaches consists of spiracles and trachea.

Spiracles

Spiracles are openings on the lateral sides of the body through which air enters and reaches the tracheal tubes. There are ten pairs of spiracles in which two pairs are thoracic spiracles and eight pairs are abdominal spiracles. Thoracic spiracles are present in the mesothorax and metathorax. Sphincters regulate the opening of spiracles. 

Structure of Spiracle

Each spiracle is surrounded by a peritreme, an annular sclerite. Spiracle leads to a chamber called the atrium. Atrium possesses a valve and filtering apparatus. 

Trachea

Trachea arises from the atrium. Tracheal tubes divide repeatedly and form tracheoles. Tracheoles are fine tubes that enter into cells and deliver oxygen.

Respiration

Expansion of the abdomen draws air into the trachea through spiracles and contraction of the abdomen expels air. Transportation of gases takes place mainly through diffusion. Air passes through tracheal tubes. Oxygen present in the air dissolves in the fluid present in the tracheoles. Majority of carbon dioxide diffuses out of the cells into the hemolymph and finally goes out through the cuticle.

Excretory System

In cockroaches, excretion occurs through malpighian tubules.

Malpighian Tubules 

Malpighian tubules are lined by glandular cells and ciliated cells. These are 100 – 150 yellow coloured thin filamentous structures present at the junctions of midgut and hindgut. They convert nitrogenous wastes into uric acid and are released into the hindgut. From hindgut, waste materials are passed out through anus. Water, bicarbonates and salts are reabsorbed by the cells of the malpighian tubules and then transferred to the haemolymph. Cockroaches are uricotelic organisms hence they excrete nitrogen in the form of uric acid.

Accessory excretory organs

Accessory excretory organs also help in excretion. It includes fat bodies, nephrocytes and urecose glands.

Nervous System

The nervous system of cockroaches consists of the brain, ventral nerve cord and ganglia.

Brain

The brain of a cockroach consists of three fused ganglia. It is represented by the supraesophageal ganglion. 

Major Ganglia in Head

Ganglia present in the head are of two types as follows:

• Supraesophageal Ganglion - It is the ganglion present in the head region. They supply nerves to the antennae and compound eyes. 
• Subesophageal Ganglion - It lies in the head below the oesophagus. They supply nerves to legs and wings. 

Circumesophageal Commissures 

It connects both ganglions. Nerve ring is formed by the two ganglions and the circumesophageal commissures. 

Nerve Cord

Double ventral nerve cord is present in cockroaches. It extends throughout the body. Ganglia are segmented.

Ganglia

Cockroach consists of ten ganglia. They are linked by paired connections. Head possesses one subesophageal ganglion. Thorax possesses three thoracic ganglia. Abdomen possess six abdominal ganglia.

Sense Organs

Four types of sense organs are present in cockroaches. These are antenna, maxillary palps and labial palps, anal cerci and compound eyes.

Antenna

Antenna is used for taste, smell and touch sensations. They possess three types of receptors as follows:

• Gustatory receptors - They are used for taste.
• Olfactory receptors - They are used for smell.
• Tactile receptors - They are used for touch sensation. 

Maxillary Palps and Labial Palps

These structures are used to taste the food.

Anal Cerci

They possess auditory or hearing receptors. They help to respond to air or earth-borne vibrations.

Compound Eyes

Compound eyes are present at the dorsal side of the head. Each eye has 2000 functional units known as ommatidia. Many ommatidia form several images of objects. This creates mosaic vision that has more sensitivity and less resolution. They help in nocturnal vision.

Practice Problems of Cockroach

Q1. Identify the number of pairs of spiracles seen in the respiratory system of cockroaches.

• Eight pairs - abdominal and two pairs - thoracic and 
• Eight pairs - thoracic and two pairs - abdominal
• Six pairs - thoracic and four pairs - abdominal
• Seven pairs - thoracic and three pairs - abdominal

Solution: The respiratory system of cockroaches contains ten pairs of spiracles in which two pairs are present in the thoracic region and eight pairs are present in the abdominal region. Thoracic spiracles are present in the mesothorax and metathorax. Hence, the correct option is a.

Q2. Which structure in a cockroach is responsible for the conversion of nitrogenous wastes into uric acid?

• Antenna
• Ganglia
• Malpighian tubules
• Anal cerci

Solution: In cockroaches, excretion occurs through malpighian tubules. Malpighian tubules convert nitrogenous wastes into uric acid and are released into the hindgut. From hindgut, waste materials are passed out through anus. Hence, the correct option is c.

Q3. In cockroaches, which sensory organ is used to detect the stimulus of touch?

• Anal cerci
• Maxillary palps
• Compound eyes
• Antenna

Solution: Antenna is a specialised sensory organ that is used to detect the stimulus of touch. This is because it has tactile receptors. Moreover, antennae also possess gustatory and olfactory receptors that help to respond to taste and smell, respectively. Hence, the correct option is d.

Q4. Cockroach excrete wastes through which mode of excretion?

• Uricotelic
• Ureotelic
• Ammonotelic
• Aminotelic

Solution: Cockroaches are uricotelic organisms hence they excrete nitrogen in the form of uric acid. Malpighian tubules convert nitrogenous wastes into uric acid and are released into the hindgut. From hindgut, waste materials are passed out through anus. Hence, the correct option is a.

FAQs of Cockroach

Question 1. What are the different types of sense organs present in the cockroach?

Answer. In cockroaches, four different types of sense organs are present. These are enlisted below:

• Antenna - It is used to taste, smell and touch.
• Maxillary palps and labial palps - These structures are used to taste the food.
• Anal cerci - Anal cerci have auditory receptors and therefore, they are used to detect air or earth-borne vibrations.
• Compound eyes - These are the specialised structures that have a characteristic of nocturnal vision.

Question 2. What are malpighian tubules?

Answer. Malpighian tubules are 100 – 150 yellow coloured thin filamentous structures present at the junctions of midgut and hindgut. They convert nitrogenous wastes into uric acid and are released into the hindgut. Malpighian tubules are lined by glandular cells and ciliated cells. 

Question 3. Discuss the brain of a cockroach?

Answer. The cockroach's brain is made up of three fused ganglia. It is represented by the supraesophageal ganglion. There are two types of ganglia in the head: the supraesophageal ganglion and the subesophageal ganglion. The supraesophageal ganglion in the head supplies nerves to the antennae and compound eyes. The subesophageal ganglion is located in the head below the oesophagus. They supply nerves to the legs and wings.

Question 4. What is the tracheal system in cockroaches?

Answer. Trachea arises from the atrium. Tracheal tubes divide repeatedly and form tracheoles. Tracheoles are fine tubes that enter into cells and deliver oxygen.

Related Topics to Respiratory system of cockroach in Biology

• Morphology of Cockroach
• Digestive system of cockroach
• Reproductive system of cockroach
• Connective Tissues
• Connective Tissue Blood
• Connective Tissue Bone
• Connective Tissue Cartilage

NCERT Class 11 Biology Chapters