Feast on this.

Krill are a vital part of the Antarctic food web (see SW 11/14/05). The shrimplike crustacean--or animal with an external skeleton, segmented body, and paired, jointed legs--is the primary food source for many Antarctic species, including Emperor penguins. To help the public learn about Antarctic krill, scientists at Woods Hole Oceanographic Institution (WHOI) have asked you to create an educational pamphlet. Where do you stag? Begin your Web hunt (below) by diving under the ice in your "Exploration Vessel." Then, gather information to complete your "Research Notes" below.

Exploration Vessel

Dive 1: www.aad.gov.au/default.asp?casid=1456

Dive 2: www.whoi.edu/oceanus/viewArticle.do?id=4778

Research Notes

1. On Dive 1, you find out that there are approximately --species of krill in the world's oceans. To make sure that you don't research the wrong species, you learn the Antarctic krill's scientific name, which is--.

2. You also learn that an adult Antarctic krill can grow to approximately 6 centimeters long and can weigh approximately--. These animals may be tiny, but they are abundant. A female krill can lay up to--eggs at a time!

3. Scientists have seen swarms, or--, of krill in the ocean stretching for many kilometers in every direction. Several thousands of these animals may reside within each--of water. The krills' bodies make the water look reddish in color.

4. To learn about the krill's life cycle, you consult WHOI scientists. Their instructions: Take Dive 2 in the Exploration Vessel and pay special attention to the article sections starting from the one titled "A Krill's Life." You plunge into your research. Immediately, you learn that the Antarctic krill can live for--to--years.

5. A krill begins its life as a--. Sometimes, it can sink to ocean depths of-- --or more before hatching. Then, it hatches into a larva, or an animal in an immature stage of development, called a--. The krill must go through many larval stages with different names before it finally becomes an--.

6. During the larva's development, it has to swim from the ocean depths up to--waters to reach its food source--phytoplankton and zooplankton. But when austral winter, or winter in the Southern Hemisphere, arrives, finding food becomes tricky. Pack ice covers the ocean. So larval krill congregate in, or just underneath, the pack ice to feast on the phytoplankton, ice algae, and micro-zooplankton trapped in the ice's pitted underside.

7. The under-ice buffet can provide krill with enough food to survive the winter. But it is not enough to provide the larva with enough energy to continue its growing process. Amazingly, krill larvae can delay their own development for a period of time. Another survival tactic: They can endure starvation by digesting some of the carbon and nitrogen in their own--and--.

Take It Further:

Create an illustrated pamphlet to educate your classmates about Antarctic krill.

ANSWERS

1.85; Euphausia superba

2. 1 gram; 10,000

3. schools; cubic meter

4. seven, eight

5. fertilized egg; 500 meters; nauplius; adult

6. surface

7. exoskeletons, muscles