Jane Burton / Axolotl {Siredon / Ambystoma mexicanum} albino, captive.

Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Ross Hoddinott / Close-up of backlit Porcelain fungus (Oudemansiella mucida) showing gills, Golith Falls, Bodin, Cornwall, UK. September.

Ross Hoddinott / Close-up of the gills of a group of small mushrooms (unidentified), north Cornwall, UK. November 2017.

Jeff Rotman / Head and gills of juvenile Scalloped hammerhead shark (Sphyrna Lewini), Kane'ohe Bay, Hawaii, Pacific Ocean.

Alex Hyde / Porcelain fungus (Oudemansiella mucida) gills. Peak District National Park, Derbyshire, UK. October.

Jeff Rotman / Symbiotic emperor shrimp (Periclimenes imperator / Zenopontonia rex) living in the gills of a spanish nudibranch (Hexabranchus sanguineus) Red Sea, Egypt

Alex Mustard / Two Whale sharks (Rhincodon typus) feeding on fish eggs at the surface, Isla Mujeres, Quintana Roo, Yucatan Peninsula, Mexico, Caribbean Sea.

Alex Mustard / Basking shark (Cetorhinus maximus) rear view of shark feeding at the surface on plankton, Cairns Of Coll, Isle of Coll, Inner Hebrides, Scotland, UK, North East Atlantic Ocean, June

Alex Mustard / Basking shark (Cetorhinus maximus) feeding at the surface on plankton, Cairns Of Coll, Isle of Coll, Inner Hebrides, Scotland, UK, North East Atlantic Ocean, June

Ross Hoddinott / Fungus (Mycena sp.) gills backlit, seen from low angle. Dartmoor, Devon, UK. 'Wild Woods' category, British Wildlife Photography Awards (BWPA) competition 2012.

Jeff Rotman / Spotted eagle ray (Aetobatus narinari), underside, Natal Coast, South Africa.