Nuptial pad

A nuptial pad (also known as thumb pad, or nuptial excrescence) is a secondary sex characteristic present on some mature male frogs and salamanders. Triggered by androgen hormones, this breeding gland (a type of mucus gland) appears as a spiked epithelial swelling on the forearm and prepollex that aids with grip, used primarily by males to grasp (or clasp) females during amplexus. They can also be used in male-male combat in some species.

Austrian biologist Paul Kammerer experimented on midwife toads' nuptial pads. He used the offsprings' apparent enlargening from generation-to-generation as evidence of Lamarckian evolution.

Many amphibian species manifest nuptial pads for use in amplexus, an example being the rough-skinned newt, Taricha granulosa.

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