Ryo O. Gotoh, Yuni Nakauchi, Anna Funahashi, Haruka Kanematsu, Kazuya Okuizumi
We have promoted “Palau Research Project” collaborating with Kamo Aquarium for more than 10 years. There are approximately 70 marine lakes formed by the rising of ancient coral reefs in Palau Islands. In marine lakes completely isolated from outer lagoons, tidal changes have also occurred, because seawaters can soak through minute pores on limestone surrounding marine lakes. However, marine organisms cannot go into and come out the marine lakes. So far, our evolutionary genetic studies clearly showed in fish (Apogonidae and Atherinidae) and mussels (Mytilidae) that peculiar evolution have occurred between marine lake and outer lagoon populations, and among different marine lake populations (Gotoh et al, 2009; 2011; Goto et al, 2011; Hanzawa et al, 2012).
On the other hand, Dawson and Jacobs (2001) reported that three different biological species of moon jellyfishes are distributed in Palau: Aurelia sp. 3 and Aurelia sp.6 inhabits outer lagoons and Aurelia sp. 4 inhabits marine lakes. We also collected the species from Palau and confirmed that the species are enough differentiated genetically and morphologically. Our comparative observation of Aurelia sp. 4 and Aurelia sp.3 clearly showed that Aurelia sp. 4 has specific morphological and ethological characters adapted to environmental conditions of calm marine lakes. We further analyzed genetic population structures in Aurelia sp. 4 and clarified that peculiar genetic differentiation has occurred among different marine lake populations.