Staghorn Hermit Crabs
These crabs have adorned themselves with hydrocoral, providing them with a mobile home that grows as they do. When a hermit crab of the genus Manucomplanus is young, infant hydrocoral of the species Janaria mirabilis settle on their shell. As the hydrocoral grows, it secretes a chemical that dissolves the crab's shell, and also spreads to cover the entire back of the crab. The crab can retreat to be completely inside the coral, and covers the entrance with the large claw seen at center. Their relationship is symbiotic: the hydroids with their stinging cells protect the crab from predators, while the crab moves the coral to new locations. The hydrocoral are filter feeders, but also host symbiotic zooxanthellae, tiny creatures that produce food from sunlight for themselves and the hydrocoral. Crabs usually mate in a close embrace just after the female has shed her shell. It's a perilous but exciting time. Because the hydrocorals have dissolved their shells, these hermit crabs might not shed their shells. This pair was definitely eyeing one another; but it seemed impolite for me to stick around and investigate this mystery. I found them off the Isla Ángel de la Guardia in the Sea of Cortez.
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