Associations between jellyfish and other organisms are frequently reported. Neverhteless, few of those records include crabs inhabiting medusae. Lychnorhiza lucerna Haeckel, 1888 were sampled (n = 1988) on the coast of the State of Paraná (25º20'-25º55'S, 48º10'-48º35'W), southern Brazil, from December 1997 to December 2004. Eight percent (166 individuals) of the medusae had one spider crab Libinia ferreirae Brito Capello, 1871 living within its subgenital porticus or on the oral arms. Megalopal stages of the same crab were also found on three jellyfish. All crabs associated with L. lucerna were young and smaller (< 3 cm) than solitary crabs caught on the bottom. Thus, L. ferreirae probably colonizes the jellyfish as a late larva and uses it as a floating nursery before becoming free-living on the ocean bottom as a typical adult crab.
Brachyura; Cnidaria; Crustacea; symbiosis
