Zebra urchin crabs (Zebrida adamsii) spend their lives riding on the backs of sea urchins in the Indo-Pacific region. Females usually stay on a single urchin, while males move from one urchin to another looking for mates. After their eggs hatch, the offspring go through several planktonic larval stages, floating around in the open water, until they reach maturity and settle down onto sea urchins of their own. We saw this one, carrying around a clutch of eggs during a dive in Anilao, Philippines. Read more inour post, Biodiversity from the Muck to the Reef: Scuba Diving Anilao, Philippines.