Science in Antarctica

A sign on the wall reads "Antarctic Petting Zoo: Feel free to pick up, fondle, kiss, cuddle, etc." In the big blue tank beneath the sign lurk, wiggle, wave, and slither five different species of sea star, several sea urchins, a sea anemone with its tendrils waving, a greenish lump called a nudibranch, a sea spider, and an isopod (something that scientist Mary Sewell says is comparable to the potato bugs or pill bugs we see on land). The sign tells visitors they are free to use the nearby net to scoop up critters.

The sea stars in the petting tank range from a huge white, fleshy creature that must measure a good foot across, to a smaller, deep red version called Odontaster validus, the species that Mary and the research team she is a part of are studying. The sea stars feel sandpapery to the touch, but also flexible, like a full water balloon.

In the cold waters of McMurdo Sound, a research team from the University of Southern California, including Donal Manahan (the PI, or Project Investigator), Mary Sewell, Adam Marsh, Doug Pace, and Heather Long, is collecting hundreds of these sea stars in order to study the development of sea star embryos and larvae--from the fertilization of the eggs all the way up to the point where the eggs hatch and microscopic sea star larvae emerge.

After divers collect them from the ocean floor, the sea stars are kept in huge, long, shallow tanks, painted a deep sky blue, so it almost looks as if you are gazing into a sky full of bright red stars.

Soon after, each sea star is injected with a hormone that causes the females to let go their eggs and the males to let go sperm (one female starfish released a million eggs!). The eggs and sperm are then mixed in a laboratory beaker, and then the scientists wait for the eggs to become fertilized. Or, Mary and Heather will collect only the eggs for special study. The growing embryos are kept in tanks with mixers to keep the water moving. Mary shows me one such tank that is full of what look like floating bits of dust. "These are our babies," she says. They have passed the early cell-division stage and are now in a stage called gastrulation, the stage during which the digestive tract is formed.

With a pipette Mary sucks up a drop of seawater from another tank and squirts the water, which containins newly fertilized eggs, onto a microscope slide and slips it under a microscope lens. On the slide I see several circles outlined in black (the fertilized eggs) and within the eggs, cells just beginning to divide. Like humans, starfish too start out as just one minute cell. The starfish cells will keep dividing and developing until the embryo hatches and a starfish larva emerges. Like caterpillars, which become butterflies, and pollywogs, which turn into frogs, starfish larvae don't look anything like the animals they eventually become. Instead of the graceful stars we know and love, they look like bizarre beetles.

It's the metabolism of the larvae and embryos that Manahan and his crew are most interested in. "We want to understand their survival at a time when there is no food and there will be no food until Christmas," Manahan says. It's not until late December when phytoplankton (tiny, one-celled plants) in the Ross Sea bloom, providing food for many different animals. How do the starfish embryos and larvae survive with no food? To understand that the scientists are measuring anything that has to do with metabolism--how the embryos and larvae use energy. They measure protein synthesis, nutrient uptake, and even how much oxygen a microscopic starfish embryo uses.

"It's one of the great mysteries of life," Manahan says. "How are we made?" He picks up a vile of tiny orange starfish eggs and shakes it. "The eggs in here are the same size as a human egg, the same size as a whale egg. How does one become a whale and one become...a mouse? How does one become a six-foot human and one become a sea star?"

For more information on the sea star scientists and their work click HERE.

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