Description
There are about 70 marine lakes located throughout the Rock Islands, but the Jellyfish Lake is the famous one. Millions of golden jellyfishes migrate horizontally across the lake daily. Jellyfish Lake is connected to the ocean through fissures and tunnels in the limestone of an ancient Miocene reef. However the lake is sufficiently isolated and the conditions are different enough that the diversity of species in the lake is greatly reduced from the nearby lagoon. The Golden Jellyfish, Mastigias cf. papua etpisoni in this lake has evolved to be substantially different from the close relatives Mastigias papua living in the nearby lagoons, they lost lost most or all of the blue pigmentation, they have a reduction in the number, length and thickness of the terminal clubs, and they are non-stinging, so swimming in that lake is truly magical! Populations of older marine lakes often have medusae with no terminal clubs and when present, the terminal clubs are only about 0.17 of the bell diameter in length. Palau, 7°9'38.833" N 134°22'30.915" E at 0.5m depth
