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

Shane Gross / Arrow crab (Stenorhynchus seticornis) on coral. Eleuthera, Bahamas.

Pascal Kobeh / Yellowline arrow crab (Stenorhynchus seticornis / lanceolatus), Canary Islands

Alex Mustard / Neck crab (Podochela sp.) lives cryptically on a deepwater sea fan (Iciligorgia nodulifera). East End, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Constantinos Petrinos / Hairless orangutan crab (Oncinopus sp. / Achaeus japonicus) Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Hairless orangutan crab (Oncinopus sp. / Achaeus japonicus) Lembeh Strait, North Sulawesi, Indonesia.

Sue Daly / Sponge spider crab (Inachus) in a Snakelocks anemone (Anemonia viridis), Sark, British Channel Islands, UK, September.

Sue Daly / Sponge spider crab (Inachus) in a Snakelocks anemone (Anemonia viridis), Sark, British Channel Islands, UK, September.

Sue Daly / Sponge spider crab (Inachus) in a Snakelocks anemone (Anemonia viridis), Sark, British Channel Islands, UK, September.

SCOTLAND: The Big Picture / Common spider crab (Macropodia rostrata) on maerl, South Arran Marine Protected Area, Isle of Arran, Scotland, UK, August.

SCOTLAND: The Big Picture / Common spider crab (Macropodia rostrata) on maerl, South Arran Marine Protected Area, Isle of Arran, Scotland, UK, August.

Alex Mustard / Xeno crab (Xenocarcinus tuberculatus) climbs up a whip coral. Sangeang Island, Sumbawa, Indonesia. Flores Sea.