Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) massing on coastal rocks, the morning after spawning, Christmas Island, Indian Ocean, Australian Territory

Shane Gross / Yet-to-be-described red cave shrimp scavenges on a dead, unidentified crab in a blue hole in The Bahamas. To avoid competition, the shrimp rises off the bottom to feed.

Nick Upton / Blind albino cave crabs / Squat lobsters (Munidopsis polymorpha), a species endemic to Lanzarote, grazing on submerged rocks in a lava tube flooded with seawater, Jameos del Agua, Lanzarote, Canary Is...

Nick Upton / Blind albino cave crab / Squat lobster (Munidopsis polymorpha), a species endemic to Lanzarote, grazing on rocks at the water's edge in a lava tube flooded with seawater, Jameos del Agua, Lanzarot...

Emanuele Biggi / Cave crab (Cerberusa caeca), Fast Lane Cave, Gunung Mulu National Park, Borneo, Sarawak, Malaysia.

Emanuele Biggi / Freshwater crab (Arachnothelphusa rhadamanthysi), an endemic species that lives in a single stream full of guano that exits from the Gomantong cave. Borneo, Sabah, Malaysia.

Chien Lee / Giant Crab Spider (Sparassidae) hides on the underside of a dead leaf during the day, Bau, Fairy Cave, Sarawak, Borneo, Malaysia

Chien Lee / Giant Crab Spider (Sparassidae) in a limestone cave, Gunung Mulu National Park, Malaysia

Chien Lee / Cave Crab (Cerberusa tipula) endemic to the limestone caves of Gunung Mulu National Park, Malaysia

Wild Wonders of Europe / Relanzón / Blind crab (Munidopsis polymorpha) endemic to the Jameos del Agua cave, Lanzarote, Canary Islands, Spain, March 2009

Angelo Gandolfi / Aboriginal rock art of a crab, Mount Borradaile, Arnhem Land, Northern Territory, Australia

Phil Chapman / Cave crab {Cerberusa tipula} Sarawak, Borneo, Indonesia

Albert Lleal / Blind Albino Cave Crab (Munidopsis polymorpha) endemic to some lava tubes, Jameos del Agua, Lanzarote Island, Canary Islands, Spain

Ingo Arndt / Photographer Ingo Arndt in cave with Christmas Island Red Crab (Gecarcoidea natalis) group, Christmas Island, Indian Ocean, Territory of Australia

Phil Chapman / White cave crab {Crustacea} Mulu caves, Sarawak, Indonesia Janibusan cave

Shane Gross / Channel clinging crab (Mithrax spinosissimus) hiding in cave, Eleuthera Island, Bahamas, North Atlantic Ocean.

Ch'ien Lee / Cave Crab (Stygothelphusa cranbrooki), endemic to a single limestone cave, Sarawak, Borneo, Malaysia

Franco Banfi / Hermit crab (Dardanus calidus) Mitigliano Cave, Punta Campanella Marine Protected Area, Amalfi Coast, Italy, Tyrrhenian Sea, Mediterranean.