Define amplexus.

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Amplexus**: Amplexus is a term used to describe a specific mating behavior observed in frogs, particularly in male frogs.

2. **Origin of the Term**: The word "Amplexus" is derived from "amplexary pads," which are specialized structures found on the first index finger of male frogs.

3. **Function of Amplexary Pads**: These pads secrete a sticky substance that helps the male frog to grasp the female frog during the mating process.

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