Gary Bell/ Oceanwide / Porcupinefish (Diodon nicthemerus) in defensive posture, Port Phillip Bay, Mornington Peninsula, Victoria, Australia

Jack Dykinga / Notch-leaf scorpion-weed (Phacelia crenulata) blooming around Desert agave (Agave desertii) in Glorieta Canyon, Anza-Borrego State Park, California, USA, March 2017. These plants are flowering during...

Eric Baccega / Men from the Mursi tribe decoratively scaring skin, one man scars the arm of another one by lifting the skin with an acacia spine and cutting it with a razor blade, Ethiopia, March 2015.

Jeff Rotman / Orangespine unicornfish (Naso lituratus) profile portrait, Red Sea, Egypt.

D. Parer & E. Parer-Cook / Long-beaked Echidna (Zaglossus bruijni) highland forests of New Guinea

Alex Hyde / Indian moon / Indian luna Moth (Actias selene) close up of defensive spines on caterpillar. Captive.

Rod Williams / North American Porcupine (Erethizon dorsatum). Captive. Endemic to North America. Captive. UK, May.

Georgette Douwma / Black-blotched Porcupinefish / Short-spine Porcupinefish (Diodon liturosus) and a Klein's butterflyfish (Chaetodon kleinii) sheltering in barrel sponge. Komodo National Park, Indonesia.

Steve Nicholls / Skeleton of a Python (Python sp)

Juergen Freund / Spine-cheek anemonefish (Premnas biaculeatus) with baby amongst anemone tentacles, Bali, Indonesia, Indo-pacific.

Alex Hyde / Yellow streaked tenrec {Hemicentetes semispinosum} at night with spines erected in threat display, Maroansetra, Madagascar

Alex Hyde / Grey caterpillar covered in defensive spines, photographed on a white background. Maroantsetra, Northeast Madagascar