Gary Bell/ Oceanwide / Whitemouth Moray (Gymnothorax meleagris) being cleaned by Cleaner Wrasse (Labroides sp) juvenile, Christmas Island, Australia

Shane Gross / Pelagic thresher shark (Alopias pelagicus) cleaned by a Bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

Shane Gross / Pelagic thresher shark (Alopias pelagicus) being cleaned by a bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

Tony Wu / Asian sheepshead wrasse (Semicossyphus reticulatus), male in white breeding colouration. Niigata Prefecture, Honshu, Japan. June.

David Fleetham / Cleaner wrasse (Labroides dimidiatus) swimming alongside Golden damsel (Amblyglyphidodon aureus) looking for parasites, Fiji, Pacific Ocean.

Alex Mustard / Harlequin sweetlips (Plectorhinchus chaetodonoides) cleaned by a pair of bluestreak cleaner wrasse (Labroides dimidiatus). South Atoll, Tubbataha Atolls, Tubbataha Reefs Natural Park, Palawan, Philipp...

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...

Alex Mustard / Yellowhead wrasse (Halichoeres garnoti) male performing a courtship dance to attract females, East End, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Roberto Rinaldi / Yellow fan coral / Seafan (Paramuricea clavata) amongst mass of invasive algae (Caulerpa taxifolia) with Rainbow wrasse fish (Coris julis), Strait of Messina, Southern Italy

Juergen Freund / Yellowtail fusilier (Caesio cuning) being cleaned by a Bluestreak cleaner wrasse (Labroides dimidiatus) Papua New Guinea.

Alex Mustard / Napoleon wrasse (Cheilinus undulatus) on a coral reef. Ras Mohammed National Park, Sinai, Egypt. Red Sea

Alex Mustard / Bluestreak cleaner wrasse (Labroides dimidiatus) cleans among the sharp teeth of a predatory roving coral grouper (Plectropomus pessuliferus) beneath an overhang on a coral reef. Ras Mohammed National...