Some lobsters cannot see at all. Deep-sea lobsters, which live in deep and dark places in the ocean, are completely blind. Other lobsters, however, have two working eyes that sit on top of short, movable stalks. Under a microscope, you can see that a lobster’s eyes have anywhere from dozens to thousands of tiny lenses. Eyes like these are called compound eyes.

Imagine a dome covered in tiles. This is what the surface of a compound eye looks like. Each tile is a lens. If you could count all the tiles, you’d find that some kinds of lobsters can have as many as about 10,000 lenses.

Compound eyes are good at detecting motion. They are also good at gathering light under dim conditions. This is important, because lobsters live underwater, where it can be dark.

A lobster has gills at the base of its walking legs. Can you imagine breathing from your hips? Gills are feathery, blood-filled organs that extract oxygen from seawater. The blood from the gills travels to other parts of the lobster’s body, delivering oxygen along the way. Our lungs and circulatory system perform a similar task. A lobster must keep water moving across its gills—in the same way that humans must keep breathing—to maintain a steady supply of oxygen.

Not all crustaceans, however, have gills. Very small crustaceans with very thin “crusts” absorb oxygen directly through their shell. And, some land-living crabs breathe air with lungs instead of using gills to absorb oxygen from water.

Lobsters are not finicky eaters. They eat animals, such as fish or shellfish, as well as plants. Crowded into a tank, they may even snack on each other.

American lobsters are capable of catching small fish with their claws. They also hunt snails, sea urchins, and clams, crushing them with their claws.

Besides hunting live prey, lobsters scavenge the sea floor for dead and rotting animal carcasses, also known as carrion. Deep-sea lobsters, in fact, feed on the carcasses of whales, fish, and other dead animals. On land, large birds called vultures break down and recycle the nutrients of the dead creatures they eat. In the ocean, lobsters play this important role in recycling the sea’s nutrients.

If you look closely at a lobster, you can see that one of its claws is larger than the other. The larger, heavier claw has thick teeth for crushing prey. The smaller claw is like a steak knife. It has sharp teeth the lobster uses to seize and slice its food.

Not all lobsters have the larger claw on the same side. A lobster is “left-handed” or “right-handed” depending on which side has the larger claw.

A newly hatched American lobster has thousands of brothers and sisters. A female lobster can lay nearly 100,000 eggs at a time.

Unlike many other animals that lay eggs, a female American lobster does not deposit her eggs in a nest. She carries her eggs, holding them under her body attached to her swimmerets for 10 or 11 months. A sticky substance covering the eggs glues them together. When the eggs are ready to hatch, a female shakes her swimmerets, opening the tiny eggshells.

As a general rule, animals that reproduce in such large numbers do so because most of their offspring die young. Life is very dangerous for young lobsters. All sorts of fish, octopuses, and sea birds feed on young lobsters. So, although a lobster may begin life with many siblings, by the time it is an adult, most of them will have perished.

A newly hatched lobster looks like a see-through flea with huge black eyes. It is not a miniature version of an adult lobster. It first goes through a free-swimming stage. It is known as a larva (LAHR vuh) in that stage, and it is about 1⁄3 of an inch (0.8 centimeter) long. A larval lobster has a soft body and delicate, featherlike limbs. It propels itself by moving these limbs in a rapid rowing motion.

A newborn lobster spends its first two or three weeks of life swimming at the surface, feeding on tiny floating organisms.

During this time, it molts often. Each time it molts, the lobster becomes more like an adult lobster, growing a hard shell, jointed legs, and long antennae. By the time a lobster settles on the sea floor, it is ready to begin its life as a bottom-dweller.

Although an American lobster’s claws are formidable weapons, lobsters are shy and try to avoid conflict. Still, claws are often a necessary defense against a hungry octopus or codfish.

Another defense many kinds of lobster have is the ability to lose a limb. Lobsters and many other crustaceans can voluntarily detach a limb that has been grabbed by a predator. When a lobster loses a limb, it can sometimes grow another in a process called regeneration.

Spiny lobsters have developed a unique and interesting defense. Octopuses like to eat spiny lobsters. Moray eels like to eat octopuses. So, spiny lobsters sometimes share a den with a moray eel. If an octopus tries to prey upon a spiny lobster, its “bodyguard,” the eel, attacks and eats the octopus.

Lobsters belong to the class Crustacea of the phylum Arthropoda. The American lobster is Homarus americanus. There are several genera of spiny lobsters, including Palinurus, Panulirus, and Jasus.