In fishes ammonia is mainly excreted by :-

Options

A. Kidney
B. Liver
C. Large intestine
D. Gill surface

Answer

To solve the question "In fishes ammonia is mainly excreted by:", we can follow these steps:

### Step 1: Understand the nature of ammonia
Ammonia is a nitrogenous waste product that is highly toxic. It needs to be excreted quickly to prevent harm to the organism.

### Step 2: Identify the excretion method in fishes
Fishes are classified as ammonotelic organisms, which means they primarily excrete ammonia directly into the surrounding water. This is because they live in an aquatic environment where water is abundant, allowing for the dilution of ammonia.

### Step 3: Determine the organ responsible for ammonia excretion in fishes
In fishes, the primary organ responsible for the excretion of ammonia is the gills. The gills are specialized structures that allow for gas exchange and also facilitate the removal of ammonia from the blood into the water.

### Step 4: Review the options provided
The options given are:
- A) Kidney
- B) Liver
- C) Large intestine
- D) Gill surface

Since we established that fishes excrete ammonia primarily through their gills, the correct answer is **D) Gill surface**.

### Final Answer
In fishes, ammonia is mainly excreted by the **gill surface**.

---