Question

Sea Slugs
by Melissa Ambrovitz

1 Imagine eating a purple grape and turning purple! If you were a sea slug, that’s exactly what would happen. Actually, sea slugs gravitate towards foods such as sea anemones, hydroids, sponges, and jellyfish, but if one of the morsels they devour happens to be purple, or some other color, the slug will automatically change to that hue.
2 Sea slugs store the pigments from their food in specialized cells called chromatophores. Changes in the shapes and sizes of the cells cause the sea slugs to change color. Camouflaged, the slug can crawl around on its favorite food without being detected by enemies.
3 Sea slugs also have other ways of protecting themselves. Many species secrete a slimy mucus that smells and tastes horrible; in these cases, the slugs’ bright coloration warns enemies that the slug would not be fun to eat.
4 A subgroup of sea slugs called eolids has yet another defense. They eat and store special stinging cells found in jellyfish, hydroids, and sea anemones. These stinging cells pass safely through the slug’s stomach and are stored in the colorful needlelike spikes on its back. Here the cells work just as well for the slug as they did for the original owner. When a passing animal touches one of the stinging cells, a thin thread containing poison shoots out like a harpoon. Among the few predators that dare to eat eolids are some starfish and parasitic worms—if they can find the sea slug hiding on its food.
A bluish or purple sea slug with bright orange spines hanging in clusters from its body and forming a fringe behind its head.
The sea slug’s bright colors warn predators of the toxins concealed in its spines.
5 So if you ever go looking for colorful sea slugs in the shallow ocean waters where they live, remember to watch out for poisonous stingers and evil-smelling mucus. And be prepared to look very carefully, or you won’t see them at all!
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Melissa Ambrovitz, “Sea Slugs”; Cricket Media Inc.


The word gravitate in paragraph 1 features the Latin root -grav-. Using your knowledge of the root, choose the meaning of the word gravitate as it is used in paragraph 1.
A. produce mucus to aid movement, or “make move easily”
B. be pulled toward something, as if “drawn by a great weight”
C. hide from enemies for protection, as if “made invisible”
D. change rapidly and frequently, or “transform one’s nature”

Answer 1

B. be pulled toward something, as if “drawn by a great weight”

Explanation: The Latin root -grav- means heavy or weight (as in gravity), so "gravitate" here means sea slugs are naturally drawn or attracted to those foods.