Cockroach

Introduction

Cockroaches are insects that crawl on surfaces that are not exposed to sunlight. Most species of cockroaches are as big as a thumbnail. The most common cockroaches found in India are glossy, brownish-black in color. They also have a pair of wings and three pairs of legs used to crawl on surfaces. They have a pair of antennas. These are scavenging, and like all pests, feed on anything, even rotting things. There are about 30 species of cockroaches that have been found in association with human habitats.

The cockroach is a word derived from the Spanish word, Cucaracha. However, the scientific name of cockroaches is derived from the Latin word, Blatta. The meaning of Blatta is “the insects that reject the light.” Cockroaches usually seem to inhabit damp, cold, and dark places. Cockroaches belong to the superorder called Dictyoptera. Which also include termites and mantids. The only word for cockroach was Blattoria. These are extreme organisms that can survive even harsh climatic conditions of Arctic frost or Tropical heat. 

One of the most prominent features that set the modern cockroaches apart were parts of the digestive system. The ancestors of the new cockroaches did not have internal Ovipositors. All the species of cockroaches have the symbionts called Blatt-bacterium present inside their gut to aid digestion. 

Body Structure of  Cockroach

The body parts include the legs, antennas, eyes, mouth, salivary glands, antennae, brain, heart, gastric, and digestive system. Cockroach is an arthropod which has a tube within a tube type of body plan. It has a complete alimentary canal with mouth and anus. Cockroaches are placed under the Blattodea order. 

These are omnivorous creatures that feed on food sources, like starch in book lining, fruits, leather, dead skin, paper, bread, and waste products. Another species of cockroach that can digest wood, called Panesthia Cribrate.

Here we will discuss only the digestive system of cockroach.

Alimentary canal in cockroach

1) Foregut

1. a)  Mouth
2. b)  Pharynx
3. c)  Oesophagus
4. d)  Crop
5. e)  Gizzard

2) Midgut

1. a) Secretory Part
2. b) Absorptive Part

3) Hindgut

1. a) Ileum
2. b) Colon
3. c) Rectum

1) Foregut

The digestive system takes in food with the help of the mouth, which is at the apex of the digestive system. The mouth leads into the short tube-like structure called the pharynx.

 A short tube is attached to the pharynx called the oesophagus. 

The oesophagus performs the task of transferring food into the sac-like organ called the crop. 

The crop stores food and empties it into the gizzard. The gizzard helps grind the food into smaller particles with the help of six internal teeth.

2) Midgut

The midgut consists of two main secretory and absorptive parts. The junction of the foregut and midgut has the Hepatic caeca, which is composed of 6 to 8 ring-like, tubular structures.

Another important structure is present at the end of the midgut to remove the excess products present; this is called Malpighian tubules. 

They are shaped like fine tubules. All these parts together are called the mesenteron.

3) Hindgut

The hindgut has parts similar to the ileum, colon, and rectum of other organisms. This part of the digestive system excretes the faeces out through the anus. All of these comprise the hindgut of the cockroach.

Like all living organisms, digestion in a cockroach is nothing different. Digestion is the process of breaking down food by enzymes and gastric juices, the simple food components are absorbed and later on assimilation is done . 

When food enters the mouth of a cockroach, it is treated by gastric juices and enzymes secreted by gastric caeca. Other essential parts of the digestive system are the salivary glands, hepatic caeca, and mesenteric glands, which work the liver of the body.

4) Digestive Glands

Three glands secrete the body’s liver digestive enzymes. These three are as follows:

•     The salivary glands
•     Inner lining of the midgut
•     Hepatic caeca

The salivary glands are present in the thoracic cavity. These are flat and like reservoirs. Each gland consists of two lobes. The reservoirs or storage areas of the salivary glands are extended into ducts that reach the hypo-pharynx through the pharynx.

Functions of the digestive system

The whole gut of cockroaches is divided into different parts that perform various functions. These functions range from a wide array of ingestion, assimilation, storage, extraction and excretion. The food that is ingested is digested in order of steps:

•     The food intake is mixed with saliva in the buccal cavity; it is then passed on to the storage organ called a crop
•     The food is then transferred to the gizzard where cuticular teeth crush it. The hair-like cushion only permits finer particles to pass on to the gizzards
•     Inside the gizzards, the food is mixed with the digestive juices secreted by the inner lining of the midgut and the hepatic caeca. The hepatic caeca absorb glucose
•     After the absorption of nutrients, the excreta are passed on to the hindgut to be excreted out of the body

Conclusion

The digestive system of this arthropod is not very complex. They comprise a very basic structure that helps the insect to ingest food that it takes in and extracts nutrients that are needed by the cockroach to survive. The main parts of the whole system are summed up into three essential parts. However, complex secretions like invertase, amylase, maltase, β-glucosidase. This makes the digestive system of the cockroach so unique.