Tony Wu / Humpback whale (Megaptera novaeangliae) adult female at rest. The tubercles on the whale's head are clearly visible, as are the barnacles (Coronula diadema), whale lice (Cyamus boopis), and hairs on t...

David Fleetham / Humpback whale (Megaptera novaeangliae), close up on tubercles on underside of chin. Hawaii.

David Fleetham / Humpback whale (Megaptera novaeangliae) spyhopping, close up on tubercles on underside of chin. Hawaii.

Magnus Lundgren / Wild Wonders of China / Short-legged horned toad (Megophrys brachykolos) held in human hand, showing white tubercles, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Moth caterpillar, tubercles with urticating hairs. Wuliangshan Nature Reserve, Jingdong, Yunnan Province, China.

Magnus Lundgren / Wild Wonders of China / Moth caterpillar on leaf, tubercles with urticating hairs. Wuliangshan Nature Reserve, Jingdong, Yunnan Province, China.

Magnus Lundgren / Wild Wonders of China / Moth caterpillar on leaf, tubercles with urticating hairs. Wuliangshan Nature Reserve, Jingdong, Yunnan Province, China.

Joao Burini / Close-up on the skin tubercles of a Treefrog (Scinax littoralis) with copper iridescence visible. Tapirai, Sao Paulo, Brazil. South-east Atlantic forest.

Tony Wu / Nudibranch (Cadlinella ornatissima), yellow with pink tipped tubercles and white rhinophores. Japan. March.

David Fleetham / Tubercles on the top of the head of a humpback whale (Megaptera novaeangliae), Hawaii. ^^^ Each protuberance contains at least one stiff hair whose purpose is not known, though they may provide the wh...

Tony Wu / Humpback whale (Megaptera novaeangliae) with tubercles on the whale's head clearly visible, they contain a hair follicle, and may be for used for sensory purposes, Vava'u, Tonga, South Pacific

Tony Wu / Humpback whale (Megaptera novaeangliae) large male spyhopping in the early morning, Vava'u, Tonga, South Pacific The single hairs in the whale's tubercles are visible, as are hairs on the front of the...