The crustacean body is protected by the hard exoskeleton. The shell around each somite can be divided into a dorsal tergum, ventral sternum and a lateral pleuron. Various parts of the exoskeleton may be fused together
So, the correct answer is 'Pleuron'



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The correct answer is option 'A', Pleuron.

The word "tergum" refers to the back or dorsal part of an organism. In the context of this question, it is specifically referring to the dorsal part of an insect. The tergum is joined on the sides by structures known as pleura.

The pleura are the lateral plates or segments that are located on either side of the tergum. They are often referred to as the "side walls" of the insect's body. The pleuron is made up of a hardened exoskeleton, similar to the tergum, and provides support and protection for the internal organs of the insect.

The pleuron is connected to the tergum through a flexible joint, allowing for movement and flexibility in the insect's body. This joint allows the insect to bend and flex its body, enabling it to carry out various movements such as walking, flying, and feeding.

Furthermore, the pleuron also serves as an attachment site for muscles. Muscles are responsible for the movement of the insect's body parts, and they are attached to the exoskeleton. The pleuron provides a stable anchor point for these muscles, allowing them to exert force and produce movement.

Other structures such as the sternum and alimentary canal are not directly joined to the tergum. The sternum is located on the ventral side of the insect's body and serves as the protective covering for the ventral nerve cord and other internal organs. The alimentary canal, on the other hand, is the digestive system of the insect and runs longitudinally through the body, but it does not directly connect to the tergum.

In conclusion, the tergum is joined on the sides by the pleuron, which serves as a lateral plate or segment and provides support, protection, and attachment sites for muscles in the insect's body.