Who knew the gelatinous bags of goo known as jellyfish could have such a complex history?
The video below shows millions of golden jellyfish thriving in the evolutionary wonderment that is Jellyfish Lake.
The lake is one of many in Palau, an island nation located about 500 miles east of the Philippines.
Pamela S. Turner writes in a National Wildlife Federation (NWF) article that five lakes each contain a jellyfish "varying from its neighbors and their common ancestor in a dramatic example of the origin of species ... If Darwin had stepped ashore in Palau instead of the Galapagos, the icon of evolution might be not Darwin's finches, but Darwin's jellyfishes."
An estimated 12,000 years ago, sea levels rose following the end of the last ice age, and jellyfish became trapped in the lake. For the jellies in Jellyfish Lake, Turner writes that they quickly diverged from the spotted jellyfish, their common ancestor.
Rumor has it that the jellyfish adapted to their new conditions by losing their sting due to a lack of predators. But Laura Martin of the Coral Reef Research Foundation clarifies to NWF that although their sting is barely felt by humans, "The lake jellyfish do have stingers, and they do use them to prey on zooplankton." The jellyfish survive in large part on algae-like organisms which live in their tissues.
How does this isolated species pass the time? Quite actively, it turns out.
According to National Geographic, the golden jellyfish engage in a daily migration which follows the arc of the sun.
Around 6 a.m., the jellies swim toward the light shining from the eastern sky -- they stop short of reaching the eastern shore, where the anemones, their main predator awaits. The Coral Reef Research Foundation in Palau notes, "These anemones are likely responsible for the evolution of the remarkable, daily migration of the golden jellies."
Instead of venturing on, the jellies know to stop at the shadows cast by the trees along the shoreline. Midday the jellies rest, and then they reverse direction, heading west as the sun sinks below the horizon.
Soaking up the rays is crucial for survival. National Geographic explains, "Solar rays nourish essential, algae-like organisms called zooxanthellae, which live symbiotically in the jellies' tissues and provide their hosts with energy as a byproduct of their photosynthesis."
Not only do the jellyfish benefit from the migration, but the lake itself relies on the jellies to mix up the nutrients and small organisms in the water, taking on the role of the sea.
At night, PBS writes that the jellyfish swim to a lower depth, where the algae population is sustained by the nitrogen-rich water.
Unfortunately, Jellyfish Lake is as sensitive to humans and outside influences as other delicate marine regions. Turner reports that back in 1999, the local jellyfish perished, possibly due to overheating by El Nino and La Nina.
Then in 2003, an invasive anemone was found in the lake, reports the Coral Reef Research Foundation. The new anemone is now quickly spreading, throwing the lake's future ecology into unpredictable disarray. The Foundation writes, "Mangrove root and shallow water communities that were once dominated by algae or diverse assemblages of invertebrates are now dominated by invasive anemones."
At a World Conservation Union meeting in 2007, researchers said it was nearly certain the anemone was introduced by tourists. Former Palau President Tommy E. Remengesau said, "Invasive species, marine or terrestrial, represent one of, if not the most, dangerous threat to our islands."
Learn about how you can help protect the oceans by visiting the Ocean Conservancy's website.
View a film by Sarosh Jacob, shot on a "Canon 5D Mark II, Sigma 15mm Fisheye Lens and Aquatica Housing," with Radiohead's "Nude" song:
Check out some of our favorite jellyfish photos below: