In crustacea excretion is by

Options

A. Malpighian tubules
B. Kidneys
C. Nephridia
D. Antennary/green glands.

Answer

### Step-by-Step Solution:

1. **Understanding Crustacea**: Crustacea is a large class of arthropods that includes crabs, lobsters, shrimp, and other similar organisms. They are primarily aquatic and have a segmented body, exoskeleton, and jointed limbs.

2. **Excretion in Crustacea**: The process of excretion in Crustacea involves the removal of waste products from the body. This is crucial for maintaining homeostasis and overall health.

3. **Excretory Organs**: In Crustacea, excretion is primarily carried out by specialized glands. The main excretory structures are:
- **Antennary Glands**: Also known as green glands, these are located at the base of the antennae. They play a significant role in the excretion of waste products.
- **Rena (or Green Glands)**: These glands are responsible for filtering waste from the blood and excreting it into the surrounding water.

4. **Function of Green Glands**: The green glands filter out metabolic wastes and excess salts from the hemolymph (the fluid equivalent to blood in invertebrates). The waste is then excreted through a duct into the environment.

5. **Process of Excretion**: After the digestion of food, any undigested material is also expelled from the body. The green glands help in removing these waste materials, ensuring that the organism remains healthy and free from toxic buildup.

### Final Answer:
In Crustacea, excretion is primarily carried out by the **antennary glands**, also known as **green glands**.

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