Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) and Humming Frog (Chiasmocleis royi) together, Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a commensal relationship. The tara...

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) adult, walking over Humming Frog (Chiasmocleis royi) without preying on it. Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a com...

Tui De Roy / Galapagos Lava Lizard (Microlophus albemarlensis) on Marine Iguana (Amblyrhynchus cristatus), Punta Espinosa, Fernandina Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Lava Lizard (Microlophus albemarlensis) on Marine Iguana (Amblyrhynchus cristatus), Punta Espinosa, Fernandina Island, Galapagos Islands, Ecuador

Tony Wu / Humpback whale (Megaptera novaeangliae) adult female at rest. The tubercles on the whale's head are clearly visible, as are the barnacles (Coronula diadema), whale lice (Cyamus boopis), and hairs on t...

Franco Banfi / Devilray (Mobula tarapacana) swimming near the surface with remoras, Ambrosio dive site, Santa Maria Island, Azores, Portugal, Atlantic Ocean

Pete Oxford / Whale Shark (Rhincodon typus) and Golden Trevally (Gnathanodon speciosus) school, Cenderawasih Bay, West Papua, Indonesia

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...

Staffan Widstrand / Wild Wonders of China / Crested myna starlings (Arcidotheres cristatellus) sitting on domestic waterbuffaloes (Bubalus domesticus), Poyang Ho Lake, Jiangxi province, China

Staffan Widstrand / Wild Wonders of China / Crested myna starlings (Arcidotheres cristatellus) sitting on domestic waterbuffaloes (Bubalus domesticus), Poyang Ho Lake, Jiangxi province, China

Georgette Douwma / Green turtle (Chelonia mydas) with two large remoras (Echeneis naucrates) attached to its carapace, at rest on artificial reef. Mabul, Malaysia.

Roland Seitre / Blackish cinclodes (Cinclode fuligineux) on beach with Southern Elephant-Seal (Mirounga leonina). This species feeds on dead skin of the seal. Falklands Islands.

Alex Mustard / Oceanic whitetip shark (Carcharhinus longimanus) accompanied by pilotfish (Naucrates ductor) as it cruises beneath the surface of the Red Sea, close to Little Brother Island. The Brothers Islands, Egy...

Gabriel Rojo / Marsh deer (Blastocerus dichotomus) male with Cattle tyrant (Machetornis rixosus) on back, Ibera Marshes, Corrientes Province, Argentina.

Constantinos Petrinos / Peacock-tail anemone shrimp (Periclimenes brevicarpalis) living commensally with the Branching Sea Anemone (Actinodendron glomeratum). Lembeh Strait, North Sulawesi, Indonesia.

Tim Fitzharris / Whale Shark (Rhincodon typus) eating with attendant Remoras (Remora remora), Philippines

Flip Nicklin / Humpback Whale (Megaptera novaeangliae) group gulp feeding, Auke Bay, Juneau, Alaska

Norbert Wu / Oceanic White-tip Shark (Carcharhinus longimanus) with Pilot Fish (Naucrates ductor), Bahamas, Caribbean

David Shale / Deepsea benthic Sea cucumber (Peniagone sp) with commensal polynoid polychaete, from mid atlantic ridge, depth approx 2600m, June 2010

Doug Perrine / Oceanic whitetip shark (Carcharhinus longimanus) with pilot fish (Naucrates ductor) Kona Coast, Hawaii, Central Pacific Ocean

Rolf Nussbaumer / Yellow wood sorrel {Oxalis dillenii} growing in bark of Mesquite tree, Texas, USA.

Sergio Hanquet / Gulfweed crab (Planes minutus), epibiont on Loggerhead turtle (Caretta caretta). Tenerife, Canary Islands.

David Hall / Brooks urchin shrimp (Allopontonia brooki), commensal among the venomous spines of Variable sea urchin (Asthenosoma varium). On sea floor, Komodo, Indonesia.

David Hall / Mozambique ghostgoby (Pleurosicya mossambica) living commensally with Sea pen (Pennatulacea). Komodo, Indonesia; November, 2006

David Hall / Swimmer crab (Lissocarcinus laevis) living commensally with Anemone (Actinodendridae). Pantar, Alor Archipelago, Indonesia.

David Hall / Soft coral ghostgoby (Pleurosicya boldinghi) swimming through Soft coral (Dendronephthya). Shrimp and benthic Comb-jellies (Ctenophora) present, all commensal. Pantar, Alor Archipelago, Indonesia.

David Hall / Banded tozeuma shrimp (Tozeuma armatum) on Black coral (Antipatharia). Komodo, Indonesia.

David Hall / Ghostgoby (Pleurosicya boldinghi) commensal on Soft coral (Dendronephthya sp). Pantar, Alor Archipelago, Indonesia.

David Hall / Decorator crab (Majidae) covered with hydroid polyps, providing camouflage and defensive sting. On Soft coral (Alcyonacea). Pantar, Alor Archipelago, Indonesia; November, 2006

Doug Perrine / Humpback whale (Megaptera novaeangliae) calf with Remora fish (Echeneidae) on underside. Vava'u, Kingdom of Tonga, South Pacific.

Gary Bell/ Oceanwide / Doughboy Scallop (Chlamys asperrima) covered with sponge, Yorke Peninsula, South Australia, Australia

Gary Bell/ Oceanwide / Doughboy Scallop (Chlamys asperrima) covered with sponge, Yorke Peninsula, South Australia, Australia

Gary Bell/ Oceanwide / Nudibranch (Ceratosoma sp) with commensal Emperor Shrimp (Periclimenes imperator), Philippines

Gary Bell/ Oceanwide / Nudibranch (Ceratosoma sp) with commensal Emperor Shrimp (Periclimenes imperator), Philippines

Gary Bell/ Oceanwide / Tyron's Risbecia (Risbecia tryoni) with commensal Emperor Shrimp (Periclimenes imperator), Milne Bay, Papua New Guinea

Gary Bell/ Oceanwide / Tyron's Risbecia (Risbecia tryoni) with commensal Emperor Shrimp (Periclimenes imperator), Milne Bay, Papua New Guinea

Doug Perrine / Dugong or Sea cow (Dugong dugon) feeding on seagrass with commensal juvenile Golden trevally (Gnathanodon speciosus) Calauit Island, off Busuanga, Calamian Islands, Palawan, Philippines.

Doug Perrine / Dugong or Sea cow (Dugong dugon) feeding on seagrass with commensal juvenile Golden trevally (Gnathanodon speciosus) Calauit Island, off Busuanga, Calamian Islands, Palawan, Philippines.

Marie Read / Avian feeding frenzy with a flock of White Pelicans (Pelecanus erythrorhynchos) swimming along a channel chasing school of fish. A mixed flock of long-legged waders, including Great Egrets (Ardea alba...

Georgette Douwma / Blackspotted puffer (Arothron nigropuctatus) with a juvenile cleaner wrasse. North Sulawesi, Indonesia.

David Fleetham / Imperial shrimp (Periclimenes imperator / Zenopontonia rex), two on Sea cucumber (Holothuroidea). Wakaya, Fiji.

David Fleetham / Wire coral goby (Bryaninops yongei) with polyps extended on Wire coral (Cirrhipathes sp). Hawaii.

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) young and Humming Frog (Chiasmocleis royi) together, Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a commensal relationship. Th...

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) young and Humming Frog (Chiasmocleis royi) together, Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a commensal relationship. Th...

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) and Humming Frog (Chiasmocleis royi) together, Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a commensal relationship. The tara...

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) adult, walking over Humming Frog (Chiasmocleis royi) without preying on it. Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a com...

Emanuele Biggi / Peruvian Tarantula (Pamphobeteus sp.) adult, walking over Humming Frog (Chiasmocleis royi) without preying on it. Los Amigos Biological Station, Madre de Dios, Amazonia, Peru. These species have a com...

David Fleetham / Lemon shark (Negaprion brevirostris) underwater with Remoras (Echeneididae), motion blurred image. West End, Grand Bahama, Bahamas.

David Fleetham / Oceanic whitetip shark (Carcharhinus longimanus) with Pilot fish (Naucrates ductor) and Remora (Echeneididae). In open ocean several miles off The Big Island / Hawaii, Hawaii.

David Fleetham / Green sea turtle (Chelonia mydas) followed closely by Spotted unicorn fish (Naso brevirostris) which feeds on turtle feces, Hawaii.

Agustin Esmoris / Southern Right Whale (Eubalaena australis) surfacing, showing callosites covered with barnacles and lice, Chubut, Argentina

Paul Bertner / Yellow-spotted Amazon River Turtle (Podocnemis unifilis) with butterfly, Sani Lodge, Ecuador

Juergen & Christine Sohns / Hippopotamus (Hippopotamus amphibius) with East African Serrated Mud Turtles (Pelusios sinuatus) on back, Sabi-sands Game Reserve, South Africa

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak, Borneo.

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak. Borneo.

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak. Borneo.

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak. Borneo.

Emanuele Biggi / Land crab (Geosesarma sp) raiding Pitcher plant (Nepenthes ampullaria) Bako Natioanl Park, Borneo Malaysia

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak. Borneo.

Emanuele Biggi / Land crab (Geosesarma sp.) which raids Pitcher plant (Nepenthes ampullaria) for prey, Sarawak. Borneo.

Franco Banfi / Emperor shrimp (Periclemenes imperator) on Sea cucumber (Thelenota ananas), Tubbataha Natural Park, UNESCO Natural World Heritage Site, Sulu Sea, Cagayancillo, Palawan, Philippines. April.

Tui De Roy / Galapagos Lava Lizard (Microlophus albemarlensis) on Marine Iguana (Amblyrhynchus cristatus), Punta Espinosa, Fernandina Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Lava Lizard (Microlophus albemarlensis) on Marine Iguana (Amblyrhynchus cristatus), Punta Espinosa, Fernandina Island, Galapagos Islands, Ecuador

Constantinos Petrinos / Peacock-tail anemone shrimp (Periclimenes brevicarpalis) living commensally with the Branching Sea Anemone (Actinodendron glomeratum). Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Peacock-tail anemone shrimp (Periclimenes brevicarpalis) living commensally with the Branching Sea Anemone (Actinodendron glomeratum). Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Emperor shrimp (Periclimenes imperator / Zenopontonia rex) with parasitic Isopod (Bopyridae) and living commensally with Leopard Sea Cucumber (Bohadschia argus) Lembeh Strait, North Sulawesi, Indonesi...

Nick Upton / Scarce fungus weevil (Platyrhinus resinosus) walking on a mossy tree stump with phoretic mites attached, woodland, Nottinghamshire UK, June.

Gabriel Rojo / Marsh deer (Blastocerus dichotomus) male with Cattle tyrant (Machetornis rixosus) Ibera Marshes, Corrientes Province, Argentina

Linda Pitkin / Emperor shrimp (Periclimenes imperator / Zenopontonia rex), commensal with Amberfish Sea cucumber (Thelenota anax) Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Commensal emperor shrimp (Periclimenes imperator / Zenopontonia rex) hitching a ride on a Nudibranch (Risbecia tryoni). Lembeh Strait, North Sulawesi, Indonesia.

Alex Mustard / RF - Emperor shrimp (Periclimenes imperator / Zenopontonia rex) exploring alien-looking landscape of host sea cucumber (Bohadschia argus). Emperor shrimps are commensals on many hosts, including sever...

Chris Mattison / Sexton beetle (Nicrophorus investigator) on a dead mouse. Drumnadrochit, Inverness, Scotland, UK, August. (The mites that can be seen are using the beetle to carry them to food; they do not parasitise...

Richard Du Toit / Burchell's Zebra (Equus burchellii) and Cattle Egret (Bubulcus ibis), Rietvlei Nature Reserve, South Africa

Jordi Chias / Pearlfish (Carapus acus) outside of host Sea cucumber (Stichopus regalis) at night. These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain....

Jordi Chias / Pearlfish (Carapus acus) outside of host Sea cucumber (Stichopus regalis) at night. These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain....

Jordi Chias / Pearlfish (Carapus acus) reversing into anus of Sea cucumber (Stichopus regalis). These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain. Me...

Jordi Chias / Pearlfish (Carapus acus) in anus of Sea cucumber (Stichopus regalis). These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain. Mediterranean...

Jordi Chias / Pearlfish (Carapus acus) in anus of Sea cucumber (Stichopus regalis). These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain. Mediterranean...

Jordi Chias / Pearlfish (Carapus acus) in anus of Sea cucumber (Stichopus regalis). These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain. Mediterranean...

Jordi Chias / Pearlfish (Carapus acus) outside of host Sea cucumber (Stichopus regalis) at night. These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain....

Jordi Chias / Pearlfish (Carapus acus) outside of host Sea cucumber (Stichopus regalis) at night. These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain....

Jordi Chias / Pearlfish (Carapus acus) outside of host Sea cucumber (Stichopus regalis) at night. These species have a commensal relationship, with the fish living in the gut of the sea cucumber. Catalonia, Spain....

Cyril Ruoso / Great plains narrowmouth toad (Gastrophryne olivacea) and Tarantula (Aphonopelma sp) sharing shelter under a rock, South Texas, USA, April.

Richard Du Toit / Cattle Egret (Bubulcus ibis) trio taking flight from Burchell's Zebras (Equus burchellii), Rietvlei Nature Reserve, South Africa

Richard Du Toit / Cattle Egret (Bubulcus ibis) on Burchell's Zebra (Equus burchellii), Rietvlei Nature Reserve, South Africa

Chien Lee / Lantern Fly (Pyrops whiteheadi) with Four-clawed Gecko (Gehyra mutilata) waiting below for the fly to excrete honeydew, Sabah, Borneo, Malaysia

Alex Hyde / European wild rabbit (Oryctolagus cuniculus) with an Atlantic puffin (Fratercula arctica) in the background. Puffins will often use old rabbit burrows as a nesting site. Isle of Lunga, Treshnish Isles...

Pascal Kobeh / Blackspotted stingray (Taeniurops meyeni) with a remora (Echeneis naucrates) attached to its belly swimming in the open water with a diver in the background. Ari Atoll, Maldives, Indian Ocean.

Pascal Kobeh / Honeycomb moray (Gymnothorax favagineus) cleaned by Common cleanerfish (Labroides dimidiatus) Maldives. Indian Ocean.

Michel Poinsignon / European Rabbit (Oryctolagus cuniculus) with a Puffin (Fratercula arctica) in the background. Puffins will often use old rabbit burrows as a nesting site, Isle of Lunga, Treshnish Isles, Inner Hebride...

Hiroya Minakuchi / African Elephant (Loxodonta africana) herd with Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Hiroya Minakuchi / African Elephant (Loxodonta africana) herd with Cattle Egrets (Bubulcus ibis), Amboseli National Park, Kenya

Cheryl-Samantha Owen / Three Cattle egrets (Bubulcus ibis) sitting on the back of an African elephant (Loxodonta africana) whilst watching for prey the elephant flushes out of the grass. Amboseli National Park, Kenya.

Franco Banfi / Devilray (Mobula tarapacana) swimming near the surface with remoras, Ambrosio dive site, Santa Maria Island, Azores, Portugal, Atlantic Ocean

Franco Banfi / Devilrays (Mobula tarapacana) swimming near the surface with remoras Ambrosio dive site, Santa Maria Island, Azores, Portugal, Atlantic Ocean

Franco Banfi / Devilray (Mobula tarapacana) near surface, with remoras, Ambrosio dive site, Santa Maria Island, Azores, Portugal, Atlantic Ocean