Ross Hoddinott / Small pearl-bordered fritillary (Boloria selene) butterfly on oxeye daisy (Leucanthemum vulgare), Marsland mouth, North Devon, UK. May 2017.

Ross Hoddinott / Small pearl-bordered fritillary (Boloria selene), Marsland mouth, Cornwall/Devon, UK. May 2017.

Ross Hoddinott / Two small pearl-bordered fritillary butterflies (Boloria selene) resting on bluebell, Marsland mouth, North Devon, UK. May 2017.

Ross Hoddinott / Small pearl-bordered fritillary butterfly (Boloria selene), Marsland mouth, Cornwall, UK. JUne 2016.

Sebastian Kennerknecht / Snowy Plover (Charadrius nivosus) biologist, Ben Pearl, picking up chick from mud flat in salt pond, Eden Landing Ecological Reserve, Union City, Bay Area, California

Wim van den Heever / Pearl-Spotted Owl (Glaucidium perlatum) perched on a branch. Okavango Delta Botswana

Alex Mustard / Group of predators hunting together, in an example of 'Nuclear foraging'. The Moray eel (Gymnothorax javanicus) flushes out prey, and is followed by a Napolean wrasse (Cheilinus undulatus) and a Bluef...

Juan Manuel Borrero / Pearl cichlid (Geophagus brasiliensis) captive, occurs in Brazil and Uruguay.

Richard Du Toit / Pearlspotted Owl (Glaucidium perlatum) on branch, Kgalagadi, South Africa

David Woodfall / Small Pearl bordered fritillary butterfly (Boloria selene) in grass, Radnorshire Wildlife Trust Nature Reserve, Wales, UK, June.

Linda Pitkin / 2020VISION / Freshwater pearl mussels (Margaritifera margaritifera) on river bed, Ennerdale Valley, Lake District NP, Cumbria, England, UK, October 2011

Juergen Freund / Cultured Golden South Sea pearls of the Pearl oyster (Pinctada maxima) Jewelmer pearls, Philippines

Juergen Freund / Aerial view of coral cays and white sand bars surrounding Bugsuk Island, Farm 1 of Jewelmer pearl farm. This private island has been highly protected since the 1970's and is in pristine environmental...

Juergen Freund / Aerial view of coral cays and white sand bars surrounding Bugsuk Island, Farm 1 of Jewelmer pearl farm. This private island has been highly protected since the 1970's and is in pristine environmental...

Juergen Freund / Jewelmer Pearlfarm, Golden south sea pearl oysters (Pinctada maxima) are prepared with plastic wedges to have nuclei inserted for the creation of cultured pearls, Palawan, Philippines, May 2009

Juergen Freund / Newly harvested cultured Golden South Sea pearls of Oyster (Pinctada maxima) displayed, Palawan, Philippines, May 2009

Juergen Freund / Goldlip pearl oyster (Pinctada maxima) opened, with cultured Golden South Sea pearl on beach, Jewelmer Pearlfarm, Palawan, Philippines, May 2009

Juergen Freund / Baby Pearl oysters (Pinctada maxima) at Jewelmer Pearlfarm, two months spats (2 mm in size) and three months (10mm in size) Palawan, Philippines, May 2009

Juergen Freund / Newly harvested cultured Golden South Sea pearls of Oyster (Pinctada maxima) displayed in oyster shell on beach, Palawan, Philippines, May 2009

Juergen Freund / Five newly harvested cultured Golden South Sea pearls of Oyster (Pinctada maxima) displayed, Palawan, Philippines, May 2009

Juergen Freund / Newly harvested cultured Golden South Sea pearl of Oyster (Pinctada maxima), Palawan, Philippines, May 2009

Juergen Freund / Newly harvested cultured Golden South Sea pearls of Oyster (Pinctada maxima) displayed in hand, Palawan, Philippines, May 2009

Juergen Freund / Newly harvested cultured Golden South Sea pearls of Oyster (Pinctada maxima) displayed in oyster shell, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm workers clean each pearl oyster regularly taking off barnacles and anything that grows on the shell, Philippines, April 2010

Juergen Freund / Jewelmer Pearlfarm, Pearl oyster (Pinctada maxima) in hanging cage, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, newly cleaned Pearl oysters (Pinctada maxima) hanging in nets from rafts waiting to be relocated to open sea, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, cleaned Pearl oysters (Pinctada maxima) in hanging cage in the open sea, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, cleaned Pearl oysters (Pinctada maxima) in hanging cages, being relocated to the open sea, Palawan, Philippines, May 2009

Juergen Freund / Women sorting cultured Golden South Sea Jewelmer pearls in Manila, Philippines, April 2010

Juergen Freund / Jewelmer Pearlfarm, cleaned Pearl oysters (Pinctada maxima) in hanging nets, being relocated to the open sea, Palawan, Philippines, May 2009

Juergen Freund / Almost perfect cultured pearl extracted from Golden South Sea Pearl oyster (Pinctada maxima) oyster will then be reused, Palawan, Philippines, May 2009

Juergen Freund / Sorting of cultured Golden South Sea pearls at Jewelmer pearls, Manila, Philippines, April 2010

Juergen Freund / Jewelmer Pearlfarm, expert technician extracts nearly perfect culutred pearl from golden South Sea Pearl oyster (Pinctada maxima) oyster will then be reused, Palawan, Philippines, May 2009

Juergen Freund / Pearl held in hand at Jewelmer Pearlfarm - golden South Sea Pearl from pearl oyster (Pinctada maxima) Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, Goldlip pearl oyster (Pinctada maxima) with golden pearl on beach, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, Golden South Sea Pearl oysters (Pinctada maxima) laid out on trays waiting to have nucleus inserted to initiate cultured pearl growth, Palawan, Philippines, May 2009

Juergen Freund / Jewelmer Pearlfarm, newly cleaned Pearl oysters (Pinctada maxima) hanging in nets from rafts waiting to be relocated to open sea, Palawan, Philippines, May 2009

Claudio Contreras / Pink abalone (Haliotis corrugata) shell detail, Guadalupe Island Biosphere Reserve, off the coast of Baja California, Mexico, January

Claudio Contreras / Pink abalone (Haliotis corrugata) shell detail, Guadalupe Island Biosphere Reserve, off the coast of Baja California, Mexico, January

Claudio Contreras / Pink abalone (Haliotis corrugata) shell detail, Guadalupe Island Biosphere Reserve, off the coast of Baja California, Mexico, January

David Kjaer / Pearl-bordered Fritillary butterfly (Boloria euphrosyne) at rest on Bracken with wings open, Bentley Wood, Wiltshire, England, UK

David Kjaer / Pearl-bordered Fritillary butterfly (Boloria euphrosyne) at rest on Bracken with wings closed, Bentley Wood, Wiltshire, England, UK

Ross Hoddinott / Small pearl-bordered fritillary {Boloria selene}, Marsland mouth, Cornwall / Devon, UK.

Ross Hoddinott / Small pearl bordered fritllary (Boloria selene) on Pyramidal orchid (Anacamptis pyramidalis) UK

GEORGETTE DOUWMA / Abalone (Mother of Pearl), Haliotidae family. Close up of shell.

Dong Lei / Spotted dove (Spilopelia chinensis) roosting in tree, half moon in sky. Mount Luoji Nature Reserve, Sichuan Province, China. May.

Heather Angel / Malachite sunbird (Nectarinia famosa) male perching on King protea (Protea cynaroides) whilst foraging for nectar. Pearl Mountain Reserve, South Africa, August.

Heather Angel / Malachite sunbird (Nectarinia famosa) male nectaring on King protea (Protea cynaroides). Pearl Mountain Reserve, South Africa, August.

Heather Angel / Mother of pearl (Pleuroptya ruralis) moth nectaring on Ragwort (Jacobaea vulgaris) at night. Surrey, England, UK. July.

Staffan Widstrand / Spotted dove (Spilopelia chinensis) Keoladeo Ghana National Park, Bharatpur, Rajasthan, India

Ross Hoddinott / Small pearl-bordered fritillary (Boloria selene) butterfly resring on English bluebell, Marsland mouth, North Devon, UK. May.

Shane Gross / A pearl from a queen conch (Lobatus gigas) in the hand of a conch fisherman on Harbour Island, Bahamas.

Paul Hobson / Pearl-bordered fritillary (Boloria euphrosyne) butterfly basking on Bracken (Pteridium aquilinum) frond. North Wales, UK. June.

Paul Hobson / Pearl-bordered fritillary (Boloria euphrosyne) resting on Bracken (Pteridium aquilinum) frond. North Wales, UK. June.

Paul Hobson / Small Pearl-bordered fritillary (Boloria selene) butterfly resting on frond. Wyre Forest, Worcestershire, England, UK.

Paul Hobson / Small Pearl-bordered fritillary adult, wings open, on bracken, Boloria selene, Wyre Forest

David Woodfall / Small Pearl bordered fritillary butterfly (Boloria silene) Dare Valley Country Park, Rhondda Cynon Taf, Wales, UK, May.

Will Watson / Alleyway between buildings in Chefchaouen, known as The Blue Pearl of Morocco, Chefchaouen Province, Morocco. April 2018.

Magnus Lundgren / Wild Wonders of China / Indo-Pacific humpback dolphin (Sousa chinensis) porpoising, with fishing net damage around throat, Pearl River Estuary, Lantau Island, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Indo-Pacific humpback dolphin (Sousa chinensis) with fishing net damage around throat, Pearl River Estuary, Lantau Island, Hong Kong, China.

Staffan Widstrand / Wild Wonders of China / Oriental turtle dove (Streptopelia chinensis), flying, Yangxian Biosphere Reserve, Shaanxi, China

Staffan Widstrand / Wild Wonders of China / Oriental turtle dove (Streptopelia chinensis), flying, Yangxian Biosphere Reserve, Shaanxi, China

Staffan Widstrand / Wild Wonders of China / Oriental turtle doves (Streptopelia chinensis), male in courtship display to female, Yangxian Biosphere Reserve, Shaanxi, China

Staffan Widstrand / Wild Wonders of China / Oriental turtle dove (Streptopelia chinensis) perched on branch, Yangxian Biosphere Reserve, Shaanxi, China

Staffan Widstrand / Wild Wonders of China / Oriental turtle dove (Streptopelia chinensis), walking on grass in Yangxian Biosphere Reserve, Shaanxi, China, April.

Remi Masson / Freshwater pearl mussel (Margaritifera margaritifera) on riverbed, Morvan Regional Nature Park, France, August. Endangered species.

Ashley Cooper / The Perlan building in Reykjavik, Icleand. The structure was designed around 5 huge water tanks that hold geothermally heated water. This hot water is used to provide heating for nearby buildings. Se...

Ashley Cooper / The Perlan building, Reykjavik, Icleand. The structure was designed around 5 huge water tanks that hold geothermally heated water used to provide heating. September 2010.

Ross Hoddinott / Small pearl-bordered fritillary (Boloria selene) butterfly resting on English bluebell, (Hyacinthoides non-scripta) Marsland mouth, North Devon, UK. May.

David Fleetham / Female Pearl oyster shrimp (Conchodytes meleagrinae) in a Black lipped pearl oyster (Pinctada margaritifera) Hawaii.

Alex Mustard / Giant moray (Gymnothorax javanicus), Honeycomb moray (Gymnothorax favagineus) and Undulated moray (Gymnothorax undulatus) eels, four emerging from hole in coral reef. North Male Atoll, Maldives. India...

Walter Soestbergen/ BIA / Small Pearl-bordered Fritillary (Boloria selene) butterflies, Netherlands

Linda Pitkin / Bluefin trevally (Caranx melampygus) mixed-species foraging and hunting behaviour, with Giant moray (Gymnothorax javanicus). Shark Reef to Jolande, Ras Mohammed National Park, Egypt, Red Sea.

Georgette Douwma / Giant moray eel (Gymnothorax javanicus). Ambon, Indonesia.

Ernie Janes / Pearly everlasting (Anaphalis sp) flowers in garden.

Georgette Douwma / Giant moray eel (Gymnothorax javaniucus) hunting over coral reef, Red Sea, Egypt. January.

Michel Roggo / Waterfalls at Pearl Shoals, Jiuzhaigou National Park, Jiuzhaigou Valley Scenic and Historic Interest Area UNESCO World Heritage Site, Sichuan, China. May 2013 . Photographed for The Freshwater Project

Michel Roggo / Waterfalls at Pearl Shoals, Jiuzhaigou National Park, Jiuzhaigou Valley Scenic and Historic Interest Area UNESCO World Heritage Site, Sichuan, China. May 2013 . Photographed for The Freshwater Project

Michel Roggo / Pearl Shoals, Jiuzhaigou National Park, Jiuzhaigou Valley Scenic and Historic Interest Area UNESCO World Heritage Site, Sichuan, China. May 2013 . Photographed for The Freshwater Project

Jussi Murtosaari / Freshwater pearl mussel (Margaritifera margaritifera), is an endangered species of freshwater mussel, Finland, March.

Jussi Murtosaari / Pearl-bordered fritillary (Boloria euphrosyne) feeding from Wild Rosemary (Rhododendron tomentosum), Finland, June.

Jussi Murtosaari / Freshwater pearl mussel (Margaritifera margaritifera) pearls, Finland, March.

Lorraine Bennery / Small pearl-bordered fritillary butterfly (Clossiana / Boloria selene), Vosges Balloons Regional Park, France, June.

Ross Hoddinott / Small pearl-bordered fritillary butterfly (Boloria selene), Marsland mouth, Cornwall, UK. JUne 2016.

Paul Bertner / Blue Mother-of-pearl (Protogoniomorpha temora) caterpillar, Udzungwa Mountains National Park, Tanzania

Sebastian Kennerknecht / Snowy Plover (Charadrius nivosus) biologists, Karine Tokatlian and Ben Pearl, collecting oystershells to spread in salt pond, which snowy plovers can use for camouflage, Eden Landing Ecological Reserv...

Sebastian Kennerknecht / Snowy Plover (Charadrius nivosus) biologist, Ben Pearl, spreading oystershells in salt pond, which snowy plovers can use for camouflage, Eden Landing Ecological Reserve, Union City, Bay Area, Californ...

Dong Lei / Pearly everlasting (Anaphalis sp) and Iris (Iris decora) flowers, Mount Makalu, Mount Qomolangma National Park, Dingjie County, Tibet, China. May

Hanne & Jens Eriksen / Spotted dove (Spilopelia chinensis) on branch, Thailand, February

Alex Hyde / Small pearl-bordered fritillary (Boloria selene) Nordtirol, Austrian Alps, July.

Andy Sands / Pearl-bordered fritillary (Boloria euphrosyne) roosting on Bracken frond, Hampshire, England, UK, May

Andy Sands / Pearl-bordered Fritillary (Boloria euphrosyne) Roosting on Bluebell flower, Hampshire, England, UK, May

Doug Wechsler / Pearl crescent butterfly (Phyciodes tharos) on goldenrod, Philadelphia, USA September