Question

The excretory organs of the prawn are -
(a)Malpighian tubules
(b)Nephridia
(c)Kidneys
(d)Green glands

Answer 1

Prawns are a type of aquatic crustaceans that have a particular type of excretory system that is different from land species due to the environment they live in. They are ammonotelic, i.e., their main excretory product is ammonia, hence they require the organs that carry out the correct mechanism.

Complete answer:
- Prawns (or shrimp) are aquatic crustaceans. They are ammonotelic; their excretory products include chiefly ammonia-based compounds, urea, and uric acid.
- The excretory system of prawn consists of mainly four organs - 1. A pair of green or antennary glands, 2. A pair of lateral ducts, 3. An unpaired renal or nephro peritoneal sac, 4. The integument.
- The green glands are called so as they are green in color and antennary glands because they are located at the base of the second antennae.
- The green glands excrete ammonia, urea, and some amino acids, while the other nitrogenous compounds and uric acids are excreted by other parts.
- They are located in the coxa of the antenna. They have three parts: 1. End sac - a small bean-shaped sac that contains a central blood lacuna. It consists of two layers; the inner layer has excretory epithelial cells and the outer layer has small blood lacunae. 2. Labyrinth - It is connected to the end sac by a pore. It contains a number of excretory tubules and each tubule is lined by a single epithelium layer meant for excretory function. 3. Bladder - It is made of a single layer of excretory epithelial cells and it connects to the exterior through a ureter.

Additional Information:
- Malpighian tubules are the excretory systems found mainly in arthropods.
- Nephridia are excretory systems found in invertebrates such as annelids, arthropods, and molluscs.
- Kidneys are excretory systems found in vertebrates.

So, the correct answer is ‘green glands’.

Note: - The prawn also carries out osmoregulation with the help of green glands. Hence, it passes out a large amount of water with urine to maintain osmoregulation.
- Crustaceans have two different excretory organs - the green glands or the maxillary glands and both have different locations. However, their basic structure remains the same.