Nuptial pad

A nuptial pad (also known as thumb pad, or nuptial excrescence^[1]) is a secondary sex characteristic present on some mature male frogs and salamanders.^[2][3][4][5] Triggered by androgen hormones, this breeding gland (a type of mucous gland) appears as a spiked epithelial swelling on the forearm and prepollex that aids with grip, which is used primarily by males to grasp (or clasp) females during amplexus.^[6] They can also be used in male–male combat in some species.^[6]

Nuptial pad (arrow) on thumb of Pelophylax esculentus

Historical background

Austrian biologist Paul Kammerer experimented on midwife toads' nuptial pads.^[7] He used the offspring's apparent enlargening from generation-to-generation as evidence of Lamarckian evolution.^[8]

Examples

Many amphibian species manifest nuptial pads for use in amplexus, an example being the rough-skinned newt, Taricha granulosa.^[9]

See also

• Amplexus – Type of mating behavior exhibited by some externally fertilizing species
• Humeral spine