Jellies – often commonly called jellyfish, although they are not really fish at all – are among the most interesting creatures in the ocean. Scientists have had a lot of time to learn about them; they have existed on earth for more than 650 million years, outdating both dinosaurs and sharks. That’s pretty good for an animal that has no bones, no brain, no real eyes, no heart, and a body that is composed of 95 percent water.
And yet, there they are, existing in some form in every ocean in the world, warm to cold, top to bottom, with over a thousand species that range in size from mere centimeters to one that’s eight feet in diameter with tentacles half the length of a football field. Sometimes deadly and sometimes not, the sting of one particular jelly – the box jelly – kills more people each year than any other marine creature.
With their ethereal and other worldly appearance, these floating apparitions are popular animals at zoos and aquariums. At the Indianapolis Zoo, visitors are often mesmerized by the moon jellies that call the Oceans building home. Named for their saucer-shaped, semi-transparent bodies, moon jellies range from eight to 20 inches wide and can deliver a mild and non-fatal sting.
Among the many fascinating aspects of this animal is the way in which it reproduces, which is a complicated affair. There are four stages of development:
· Medusa (another name for a free-swimming jelly or an adult with tentacles hanging down, and the stage most people associate with jellies);
· Planulae (this is where males and females reproduce and form very small larvae);
· Polyps (formed when planulae settle to the bottom of the ocean on rocks and shells and form polyps that look like tiny sea anemone;
· Ephyrae (formed when each polyp “bud offs” and creates hundreds of baby jellies called ephyrae, which then quickly grow into medusa).
Although the jellies have this elaborate system for making little jellies, and they do it in quantity, the survival rate for moon jellies (and most all jellies) is very low. There are many predators in the ocean that like to eat the little 1-3 centimeter-long ephyrae, and their lifespans are very short. Here at the Zoo, the aquarists estimate the growth to be at least one inch a month, and they’re ready for the exhibit tank at about six months of age. The lifespan of most species of jellies is a few months to a year, but moon jellies in human care can live for a year or more, with luck.
The aquarists at the Indianapolis Zoo have been working for years to increase their success rate for moon jelly reproduction, with a goal of being able to bring enough ephyrae to maturity so they can go on exhibit and make the Zoo self-sufficient in terms of animals needed. Getting the water temperature, water movement, food, lighting, and many other factors just right are what make it all succeed.
In 2012, for the first time, there are two moon jellies on exhibit that came from successful breeding at the Zoo, joining adults that have come from other zoos. The goal of the aquarists is to grow enough moon jellies to not only populate their own exhibit, but also to share with other aquariums, something they expect to achieve in late 2012 or early 2013.
The conservation story surrounding jellies is somewhat the reverse of animals that are endangered due to small population. Jellies in the ocean are reproducing at sometimes alarming rates*, possibly due to factors such as warming seas, organic pollution as a food source, and overfishing/habitat loss for fishes that either predate on jellies or take up space in the ocean environment. More jellies feeding on more and more of the oceans’ zooplankton means less food for other marine creatures, which means disruptions in the whole ocean ecosystem.
Connections to the Indianapolis Prize
Three of the 29 nominees for the 2012 Indianapolis Prize have the health of the oceans among their primary concerns. Dr. Carl Safina, founder of Blue Ocean Institute, an organization that brings science, art and literature together to inspire a closer bond with nature, especially the sea. One of the best-known and respected scientists in the world, Safina was a finalist for the Indianapolis Prize in 2010 and was again nominated for the 2012 Prize.
A second Prize nominee for 2012 is Dr. P. Dee Boersma of the University of Washington, Seattle, Center for Penguins as Ocean Sentinels. Since the 1970s, Dr. Boersma has studied and documented impact of global warming on penguins, and successfully stopped harmful harvesting and development through penguin colonies. Steve Amstrup, of Polar Bears International, is concerned with the effects of global warming on the dwindling populations of the world’s largest marine mammal.
Honoring those who work to conserve the natural world, including the oceans, the biennial Indianapolis Prize includes an unrestricted grant of $100,000 and the Lilly Medal to the winner, along with unprecedented recognition of the vital work done by heroes of conservation throughout the world.Learn more about the Oceans exhibit at the Indianapolis Zoo.
*There are a few freshwater jelly species that are endangered.