Sergio Hanquet / Arrow crab (Sternorhynchus lanceolatus). Tenerife, Canary Islands.

Alex Mustard / Commensal emperor shrimp (Periclimenes imperator) moves across the colourful red patterned surface of its host Candycane sea cucumber (Thelenota rubralineata). Misool, Raja Ampat, West Papua, Indonesi...

Alex Mustard / Reef lizardifsh (Synodus variegatus) at a cleaning station, being cleaned by Holthuis anemone shrimps (Ancylomenes holthuisi). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Fabio Pupin / Red swamp crayfish (Procambarus clarcki), invasive species, captive, Italy, July.

John Chan / Crenulated fiddler crab (Uca crenulata) waving its major claw at another crab, part of a courtship display, Southern California, USA, June.

John Chan / Crenulated fiddler crab (Uca crenulata) feeding on detritus, Southern California, USA, June.

John Shaw / Sally lightfoot crabs (Grapsus grapsus) on the beach at Puerto Egas, Santiago Island, Galapagos, May.

Shane Gross / Bubble coral shrimp (Vir philippinensis) on Bubble coral (Plerogyra sp). Anilao, Philippines.

Andy Rouse / Sally lightfoot crab, (Grapsus grapsus), feeding on marine iguana parasites and dead skin, Galapagos

Georgette Douwma / Boxer Crab (Lybia tessellata) with sea anemones in its claws for defense. Lembeh Strait, North Sulawesi, Indonesia.

Nick Hawkins / European green crab (Carcinus maenas), an invasive species in North America, Kejimkujik Seaside National Park, Nova Scotia, Canada. July.

SCOTLAND: The Big Picture / Close up of a Long clawed squat lobster (Munida rugosa) in Loch Carron, January 2016.

Steven David Miller / Sand bubble patterns created by Sand bubbler crabs (Scopimera inflata), Cape Hillsborough National Park, Queensland, Australia. September.

Juergen Freund / Wide-angle timelapse of Sand bubbler crabs (Dotillidae) feeding, filtering detritus and plankton from sand and discarding the processed sand as pellets, which cover the beach, Wet Tropics World Herita...

Juergen Freund / Sand bubbler crabs (Dotillidae) feeding, filtering detritus and plankton from sand and discarding the processed sand as pellets, which cover the beach, Wet Tropics World Heritage Area, Cape Tribulatio...

Juergen Freund / Sand bubbler crab (Dotillidae) feeding, filtering detritus and plankton from sand and discarding the processed sand as pellets, which cover the beach, Wet Tropics World Heritage Area, Cape Tribulation...

Remi Masson / European crayfish (Astacus astacus) in a lake. Alps, Switzerland, July.

David Fleetham / Cleaner wrasse (Labroides dimidiatus) eating parasites off Coral grouper (Cephalopholis miniata) with Shrimp (Lysmata amboinensis) Mabul Island, Malaysia.

Nick Upton / Common prawns (Palaemon serratus) and a Rock goby (Gobius paganellus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Rock goby (Gobius paganellus) stealing food from a scavenging Common prawn (Palaemon serratus) in a rockpool, Cornwall, England, UK, September.

Sue Daly / Common lobster (Homarus gammarus) shovelling gravel out of a hole, Sark, British Channel Islands, UK, August.

Sue Daly / Long legged spider crab (Macropodia) walking across the seabed, Sark, British Channel Islands, UK, June.

Doc White / California sea otter (Enhydra lutris) feeding on Northern kelp crab, Monterey Bay, California, USA, Eastern Pacific Ocean, May

Jeff Rotman / Hauling in dragger net filled with Haddock (Melanogrammus aeglefinus), Pollock (Pollachius), Dogfish (Squalidae) and Lobster (Nephropidae) Georges Bank off Massachusetts, New England, USA, May 2015. M...

Adrian Davies / Blackback land crab (Gecarcinus lateralis) dragging leaf into burrow, Barbados.

Juergen Freund / Mud crab (Scylla serrata) in shallow sandy water. Split level with island and thatched house on stilts. Moromahu Island, Wakatobi, South Sulawesi, Indonesia. Second Place in the Portfolio Award of the...

Alex Mustard / Portrait of Sally lightfoot crab (Grapsus grapsus) on a beach. San Cristobal Island, Galapagos Islands, Ecuador. Tropical East Pacific Ocean.

Tui De Roy / Dead Sally-lightfoot crab (Grapsus grapsus) washed up in surf, Puerto Egas, James Bay, Santiago Island, Galapagos, Ecuador, May.

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

Pascal Kobeh / Aggregation of thousands of Spider crabs (Leptomithrax gaimardii) for moulting, South Australia Basin, Australia. Pacific Ocean.

Pascal Kobeh / Aggregation of thousands of Spider crabs (Leptomithrax gaimardii) for moulting, South Australia Basin, Australia. Pacific Ocean.

Visuals Unlimited / Deep-sea Hermit Crab outside a shell (Pagurus curacaoensis)

Alex Mustard / Emperor shrimp (Periclimenes imperator / Zenopontonia rex) hitchhiking on large t-bar nudibranch (Ceratosoma trilobatum) The shrimp gains food source and protection on the toxic seaslug. Bitung, North...

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

Alex Mustard,Alex Mustard / A portrait of a small Candy stripe shrimp (Lebbeus grandimanus) in front of its host pink anemone (out of focus because of the magnification). Browning Wall, Browning Pass, Port Hardy, Vancouver Islan...

Cheryl-Samantha Owen / Fishing for West coast rock lobster (Jasus lalandii) aboard the James Archer (Oceana fisheries). Crew haul up lobster trap. Saldanha Bay and St. Helena Bay, Western Cape, South Africa.

Cheryl-Samantha Owen / West coast rock lobster (Jasus lalandii) captive at Two Oceans Aquarium, Cape Town, South Africa.

Cheryl-Samantha Owen / West coast rock lobster (Jasus lalandii) commercial fishing boat (James Archer) leaves the Saldhana Bay harbour before the break of dawn. The lights of the town and the lighthouse flash on the horizon...

Cheryl-Samantha Owen / A hoop net with West coast rock lobster (Jasus lalandii) being pulled up in sea kayak for recreational fishing. Kommetjie, Western Cape, South Africa

Cheryl-Samantha Owen / West Coast Rock Lobster (Jasus lalandii) observed by diver. Kalk Bay, Atlantic Ocean, False Bay, Valsebaai, Western Cape, South Africa

Cheryl-Samantha Owen / The crew of the James Archer, Oceana fisheries, throws baited lobster traps into the ocean to catch West coast rock lobster (Jasus lalandii). View from cabin window, Saldanha Bay and St. Helena Bay, W...

Cheryl-Samantha Owen / Recreational fishing in a sea kayak for West coast rock lobster (Jasus lalandii). Hoop net or trap is lowered onto the sea floor or kelp bed with a pouch of bait (sardines or pilchards) attached. Kom...

Cheryl-Samantha Owen / Crew of the James Archer (Oceana fisheries) pull up a lobster trap during West coast rock lobster (Jasus lalandii) fishing, Saldanha Bay and St. Helena Bay, Western Cape, South Africa.

Franco Banfi / Crab covered in algae, Golfo Nuevo, Peninsula Valdes UNESCO Natural World Heritage Site, Chubut, Patagonia, Argentina, Atlantic Ocean, October

David Shale / Deepsea Orange ghost lobster (Decopoda, Thalassinidae) from coral seamount in the Indian Ocean, December 2011

Juergen Freund / Land Hermit crab using a plastic bottle cap as its home. Kavieng, Papua New Guinea, June 2010

Juergen Freund / Hermit crab with shell covered in soft coral (Heteroxenia fuscescens) Lembeh Strait, North Sulawesi, Indonesia

David Shale / Decapod {Systellaspis sp} from midwater catch 195-498m, Mid-Atlantic Ridge, North Atlantic Ocean

Juan Carlos Munoz / Crab walking over beach leaving tracks in the wet sand, Floreana Island, Galapagos, January

Solvin Zankl / Anomuran larva of a Hermit crab, Atlantic ocean

Solvin Zankl / Deepsea planktonic megalopa stage of crab development, Atlantic ocean.

Solvin Zankl / Deepsea marine larva of decapod crustacean {Sergestes sp} Atlantic ocean. Second place in Underwater categroy of the GDT 2011 competition

Jeff Rotman / Symbiotic shrimp on basal disc of sea anemone, Red Sea

Pascal Kobeh / Atlantic / Common rock crab (Cancer irroratus) on the reef in the middle of green sea urchins (Strongylocentrotus droebachiensis) Gulf of Saint Lawrence, Canada

Pascal Kobeh / Atlantic rock crab or common rock crab (Cancer irroratus) on the reef, Gulf of Saint Lawrence, Canada.

Pascal Kobeh / Two Atlantic / American lobsters (Homarus americanus) fighting, Gulf of Saint Lawrence, Canada

Pascal Kobeh / Atlantic / American lobster (Homarus americanus) Gulf of Saint Lawrence, Canada

Pascal Kobeh / Atlantic / American lobster (Homarus americanus) with a Grey seal (Halichoerus grypus ) swimming in the background, Gulf of Saint Lawrence, Canada

Pascal Kobeh / Red spotted coral crab (Trapezia rufopunctata) hidden in a hard coral (Pocillopora sp.) New Caledonia, Pacific Ocean.

Pascal Kobeh / Coleman's bubble coral shrimp (Vir colemani) with its eggs in a bubble-coral (Plerogyra sinuoasa) where it is protected, New Caledonia, Pacific Ocean Completed Review

Nigel Cattlin / Sand bubbler crab (Scopimera sp) on sand at low tide, Andaman Sea. Near Krabi, Krabi Province, Thailand.

Nigel Cattlin / Bubbler crab (Scopimera sp) with balls of sand and escape hole forming pattern in sand. Andaman Sea at low tide, near Krabi, Krabi Province, Thailand.

Nigel Cattlin / Balls of sand and escape holes forming pattern in sand, created by Bubbler crab (Scopimera sp). Andaman Sea at low tide, near Krabi, Krabi Province, Thailand.

Nick Upton / Young Edible crab (Cancer pagurus) and a Rock goby (Gobius paganellus) side by side in a rock pool, looking towards the camera, The Gower, Wales, UK, August.

Alex Mustard / Portrait of Morgan's coral hermit crab (Paguritta morgani) looking out of its burrow in a hard coral colony. These hermit crabs are sedentary, remaining in their burrows, rather than carrying arou...

Alex Mustard / Box crab (Calappa sp.) female emerging from the sand and shakes her body to release her tiny young. Dauin, Dauin Marine Protected Area, Dumaguete, Negros, Philippines. Bohol Sea, tropical west Pacific...

Alex Mustard / Sleepy sponge crab (Dromia dormia) climbing over a rock, carrying its sea squirt (Didemnum molle) disguise, with brittlestar. Anilao, Batangas marine protected area, Luzon, Philippines. Verde Island P...

Alex Mustard / Pair of Emperor shrimp (Zenopontonia rex / Periclimenes imperator) female is the larger one, hitch a ride on a large nudibranch (Tambja luteolineata) and pick food from the seabed with their claws. Bi...

Alex Mustard / West Indian spider crab (Mithrax spinosissimus) shelter in a giant barrel sponge (Xestospongia muta) on a coral reef. Jardines de la Reina, Gardens of the Queen National Park, Cuba. Caribbean Sea.

Georgette Douwma / Kaleidoscopic image of Hingebeak shrimp (Rhynchocinetes durbanensis). Bali, Indonesia.

Franco Banfi / Red king crab (Paralithodes camtschaticus) on sand. Vrangel Bay, Primorsky Krai, Russia. August.

Sergio Hanquet / Sally lightfoot crab (Percnon gibbesi). Tenerife, Canary Islands.

Sergio Hanquet / Sally lightfoot crab (Percnon gibbesi). Tenerife, Canary Islands.

Sergio Hanquet / Sally lightfoot crab (Percnon gibbesi). Tenerife, Canary Islands.

Sergio Hanquet / Shrimp (Trachycaris restricta), close up. Tenerife, Canary Islands.

Sergio Hanquet / Shrimp (Trachycaris restricta), close up. Tenerife, Canary Islands.

Sergio Hanquet / Rock lobster (Scyllarides latus). El Hierro, Canary Islands.

Sergio Hanquet / Rock lobster (Scyllarides latus). El Hierro, Canary Islands.

Sergio Hanquet / Rock lobster (Scyllarides latus). El Hierro, Canary Islands.

Sergio Hanquet / Rock lobster (Scyllarides latus). El Hierro, Canary Islands.

Sergio Hanquet / Red-backed cleaner shrimp (Lysmata grabhami) on sandy sea floor. Tenerife, Canary Islands.

Sergio Hanquet / Red-backed cleaner shrimp (Lysmata grabhami), view from above. Tenerife, Canary Islands.

Sergio Hanquet / Red-backed cleaner shrimp (Lysmata grabhami) head, close up. Tenerife, Canary Islands.

Sergio Hanquet / Red-backed cleaner shrimp (Lysmata grabhami). Tenerife, Canary Islands.

Sergio Hanquet / Red-backed cleaner shrimp (Lysmata grabhami). Tenerife, Canary Islands.

Sergio Hanquet / Sally lightfoot crab (Percnon gibbesi) group. Tenerife, Canary Islands.

Sergio Hanquet / Arrow crab (Sternorhynchus lanceolatus) portrait. Tenerife, Canary Islands.

Sergio Hanquet / Arrow crab (Sternorhynchus lanceolatus), close up. Tenerife, Canary Islands.

Sergio Hanquet / Small European locust lobster (Scyllarus arctus), Tenerife, Canary Islands.

Sergio Hanquet / Small European locust / Lesser slipper lobster (Scyllarus arctus), Tenerife, Canary Islands.

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

David Hall / Yellow prawn-goby (Cryptocentrus cinctus) and Snapping shrimp (Alpheus sp). Mutualistic symbiosis with goby as watchdog and shrimp maintaining burrow. Komodo, Indonesia.

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

David Hall / Arcfin shrimpgoby (Amblyeleotris arcupinna) and Snapping shrimp (Alpheus sp), blind shrimp maintaining contact with goby via antenna. Mutualism with shrimp maintaining burrow and goby acting as lookou...

David Hall / Anemone hermit crab (Dardanus pedunculatus) carrying Anemones (Calliactis polypus) on shell. Mutualism in which anemones are transported to new feeding opportunities whilst providing camouflage and de...

David Hall / Haig's porcelain crab (Porcellanella haigae) living commensally on Sea pen (Pennatulacea) Crab recently emerged from exoskeleton. Pantar, Alor Archipelago, Indonesia.