Description

A typical American lobster is 12 inches (30 cm) long and weighs about 2 pounds (0.9 kg). Some grow to more than 3 feet (90 cm) long and weigh more than 40 pounds (18 kg). Spiny lobsters are about the same size as American lobsters. Lobsters can live as long as 100 years.

Lobsters belong to a group of animals called crustaceans. Like other crustaceans, lobsters have a rigid structure called a carapace, or shell, that encloses the soft parts of the body. The carapace may be any of various colors, usually mottled with numerous markings. It is usually dark green in American lobsters and brownish in spiny lobsters. Spiny lobsters have numerous spiny projections on their shells. Lobster shells turn red after they have been cooked.

In days of old, knights wore suits of armor to protect themselves in battle. Lobsters have a natural protective shell of their own, made of a material called chitin (KY tihn).

Like a suit of armor, a lobster’s exoskeleton is made of not one, but many, solid pieces. Some of the pieces are permanently attached to one another and do not move. Others are connected by a flexible material, which lets a lobster move freely.

The exoskeleton of an American lobster is made of 21 different pieces. The head has 6 pieces, the thorax (middle part) 8 pieces, and the tail, 7 pieces. The thickest part of a lobster’s shell—on its back—is called the carapace (KAR uh pays). You can think of it as a shield.

Because lobsters are invertebrates, their shell is their body’s only structural support. A lobster’s muscles are attached to its outer skeleton (shell) as ours are to our internal skeleton. Without its shell, a lobster could not move.

An unjointed shell covers the head and forepart of the body. In the head region the lobster has a pair of compound eyes at the ends of jointed movable stalks, and two pairs of sensory antennae (feelers). Five pairs of legs grow under the forepart of the body. In the American lobster, the first pair has evolved into large, pincer-like claws used to crush prey.

The abdomen is covered by six overlapping shell rings that are joined together. A pair of fringed paddles, called swimmerets, is attached to each of the first five rings. A fan-shaped tail is attached to the last ring. In common usage, the entire abdomen is called lobster tail. Usually this is the only part of a spiny lobster that is eaten. In American lobsters, there is considerable meat in the enlarged claws as well as in the tail.

Lobsters look like they might be hollow, but that is not the case.

Lobsters have the same major internal body structures as humans. Lobsters have a heart that pumps blood around its body and a brain that connects to a nervous system. For eating, digesting, and eliminating food, the lobster has a mouth, stomach, intestines, and anus. Lobsters also have sex organs for reproducing.

While lobsters share similarities with vertebrates, they are much more similar in structure to other invertebrates, especially insects. Like insects, lobsters have an open circulatory system. Animals with such a system lack blood vessels in some areas of their bodies. Blood flows directly into these areas and delivers oxygen and nutrients to the organs and tissues.

If you see an animal walking on the sea floor, and it has a jointed tail, two long antennae, two short antennae, lots of legs, and dark eyes that are on stalks, it is likely to be a lobster.

You can count the number of segments in its tail. A lobster’s tail is made of seven distinct pieces, including the fanlike tip.

Another way to identify a lobster is by the number of its legs. Lobsters have five pairs of legs. Clawed lobsters, such as the American lobster, have front legs that end in large claws. The next two sets of legs have smaller pincers on their tips. Both clawed and clawless lobsters have delicate, leglike limbs under their abdomen that are used for swimming. These limbs are called swimmerets.

Lobsters are known as decapods. “Deca” is a Greek word that means 10, and “pod” is a Greek word that means foot. In addition to the lobster, other 10-footed crustaceans include shrimp and crayfish.