Excretory organs of anamniotes.

Options

A. Metanephric kidneys
B. Mesonephric kidneys
C. Pronephric kidneys
D. Anephric kidneys

Answer

### Step-by-Step Solution

1. **Definition of Anamniotes**:
- Anamniotes are a group of organisms, including fishes and amphibians, that lay their eggs in water. They are characterized by the absence of an amniotic cavity, which is a fluid-filled sac that surrounds the embryo in amniotes (like reptiles, birds, and mammals).

2. **Excretory Organs in Anamniotes**:
- The primary excretory organs in anamniotes are mesonephric kidneys. These kidneys are responsible for the excretion of waste products and the regulation of water and electrolyte balance.

3. **Development of Mesonephric Kidneys**:
- Mesonephric kidneys develop from the pronephric kidneys, which are the most basic type of kidney found in early embryos. As the organism matures, the pronephric kidneys degrade, and mesonephric kidneys take over as the functional excretory organs.

4. **Structure of Mesonephric Kidneys**:
- Mesonephric kidneys are also referred to as opisthonephric kidneys. They are associated with a mesonephric duct, which is derived from the pronephric duct. This structure is crucial for the transport of urine from the kidneys to the excretory system.

5. **Conclusion**:
- Therefore, the correct answer to the question regarding the excretory organs of anamniotes is **mesonephric kidneys**. The other options, such as metanephric kidneys, pronephric kidneys, and anephric kidneys, do not apply to anamniotes.

### Final Answer:
The excretory organs of anamniotes are **mesonephric kidneys**.

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