Alex Mustard / 2020VISION / Detail of Plumose anemone (Metridium senile) in its retracted state at slack water when it is not feeding. Plymouth Sound, Devon, England, UK, English Channel, July

Rolf Nussbaumer / Portrait of Ornate Box Turtle (Terrapene ornata) with head retracted into shell. Sinton, Corpus Christi, Coastal Bend, Texas Coast, USA

Jim Brandenburg / Western Box Turtle (Terrapene ornata) retracted in shell, South Dakota

David Shale / Anthomastus - octocoral with polyps retracted. Collected from coral sea mount near Dragon vent field on SW Indian Ridge, Indian Ocean.

David Shale / Anthomastus - octocoral with polyps retracted. Collected from coral sea mount near Dragon vent field on SW Indian Ridge, Indian Ocean.

David Shale / Anthomastus - octocoral with polyps retracted. Collected from coral sea mount near Dragon vent field on SW Indian Ridge, Indian Ocean.

David Shale / Anthomastus - octocoral with polyps retracted. Collected from coral sea mount near Dragon vent field on SW Indian Ridge, Indian Ocean.

Jeff Rotman / Stony Coral (Scleractinia) with polyps retracted. Papua New Guinea, Bismarck Sea.

Alex Mustard / 2020VISION / Comb jelly / Sea gooseberry (Pleurobrachia pileus) in open water. The feathery tentacles are used for capturing prey and can be extended behind the jellyfish or completely retracted. Loch Carron, Ross...

Jan Hamrsky / Darner Dragonfly (Aeshna) nymph; sequence with its specialised mouthparts retracted and extended. Europe, August.

Brent Stephenson / Pacific Reef Egret (Egretta sacra) walking across a beach with its neck retracted. Kaikoura, Canterbury, New Zealand, December.

Juergen Freund / Four True clownfish / Clown anemonefish(Amphiprion percula) in their mostly-retracted anemone. North Raja Ampat, West Papua, Indonesia.

Tony Phelps / Burrowing Scorpion (Opistophthalmus macer) retracted into burrow. De Hoop Nature Reserve, Western Cape, South Africa, January.

Georgette Douwma / Crinoid or Featherstar (Crinoidea sp.) with most of its arms retracted, on coral reef; the blue organism in the foreground is a sea-squirt (sessile form). Rinca, Komodo National Park, Indonesia, Octob...

Edwin Giesbers / Grey Heron (Ardea cinerea), neck retracted to reduce heat loss in snow. The Netherlands, January.

Edwin Giesbers / Grey Heron (Ardea cinerea), neck retracted to reduce heat loss in snow. The Netherlands, January.

Edwin Giesbers / Grey Heron (Ardea cinerea), neck retracted and standing on leg to reduce heat loss in snow. The Netherlands, January.

Edwin Giesbers / Grey Heron (Ardea cinerea), neck retracted and standing on one leg to reduce heat loss in snow. The Netherlands, January.

Edwin Giesbers / Grey Heron (Ardea cinerea), neck retracted and standing on one leg to reduce heat loss in snow. The Netherlands, January.

Stephen Dalton / Green Hydra (Hydra viridis) with tentacles retracted. UK, November.

Pete Oxford / Saddleback Galapagos Tortoise (Chelonoidis nigra hoodensis) retracted in shell, base of Sierra Negra, Isabella Island, Galapagos Islands, Ecuador

Edwin Giesbers / Head portrait of Caspian / Stripe necked terrapin (Mauremys caspica) with head retracted into shell, Lesbos, Greece

Wild Wonders of Europe / Radisics / Hermann's tortoise (Testudo hermanni) with head retracted into shell, near Meteora, Greece, October 2008

Juan Carlos Munoz / Grey seal {Halichoerus grypus} close up of front flipper showing retracted claws, Donna Nook, Licolnshire, UK

Juan Carlos Munoz / Grey seal {Halichoerus grypus} close up of front flipper showing retracted claws, Donna Nook, Licolnshire, UK

Tony Phelps / Common padloper / Parrot-beaked tortoise (Homopus arealotus) adult female with head and legs retracted into shell, Little Karoo, South Africa

GEORGETTE DOUWMA / Close up of Mushroom coral (Heliofungia actiniformis) with polyps partially retracted. Bunaken, Sulawesi, Indonesia.

Jeff Rotman / Gorgonia Coral (Gorgonacea sp.) with retracted polyps. Papua New Guinea.

Dan Burton / Snakelocks anemone retracted and closed (Anemonia viridis) Cornwall, UK

Michael Hutchinson / Cheetah (Acinonyx jubatus), hind feet (resting across another cheetah) showing pads and characterictic non-retracted claws, Kenya

David Shale / Sea Pen (Pennatulid), with partially retracted polyps, deep sea Atlantic ocean

Rob Tilley / Snapping turtle with head retracted {Chelydra serpentina} MA, USA

Chris Newbert / Leather Coral (Sarcophyton trocheliophorum) colony with polyps retracted, surrounded by schooling Pygmy Sweeper (Parapriacanthus ransonneti), sponges and soft coral, Red Sea

Mark Moffett / Tarantula (Theraphosidae) underside with retracted fangs can be seen at top of frame, Chile

Mark Moffett / Slug Caterpillar (Setora fletcheri) spines loaded with toxins are retracted when the animal is undisturbed, Tam Dao National Park, Vietnam, sequence 1 of 2

GEORGETTE DOUWMA / Red coral with polyps retracted {Corallium rubrum} Mediterranean

Chris Shields / Illustration of Dragonfly (Aeshnidae sp.) nymph - showing clasping mouthparts in extended and retracted positions.

Juergen Freund / Closed sea anemone, tentacles retracted {Tealia lofotensis} Canadian Pacific. Sequence