Lobsters are invertebrates, members of the Class Crustacea of the Phylum Arthropoda. Lobsters, along with other organisms without backbones (such as crab, shrimp, crayfish, water fleas, copepods, barnacles, and wood lice), are commonly called crustaceans (from a Latin word meaning hard shell).

The lobster’s body has 19 parts, each covered by a section of its hard shell. The shell is thin and soft where the parts join, so the lobster can bend its body and move about.

Lobsters breathe through gills located beneath the shell on both sides of its thorax (center part).

Lobsters have two pairs of antennae on their head. Their eyes are compound eyes, consisting of hundreds of lenses joined together on the ends of a pair of slender, jointed organs called “stalks.” They keep their antennae and eye stalks moving constantly to search for food and to watch for enemies.

The lobster’s “brain” is about the size of a grasshopper’s. It is unlikely that the lobster’s nervous system is sophisticated enough to sense pain as we know it. Like all arthropods, the nervous system of a lobster is very primitive, containing far fewer nerve cells than human nervous systems. The nerve cells are grouped in clusters called ganglia. A lobster has no cerebral cortex, the area of the human brain that gives the perception of pain.

Lobsters are cannibalistic. Very territorial, when they encounter one another, they become aggressive and fight, using their claws as weapons, until one backs away. They generally hide in a burrow by day and prowl the ocean floor by night, covering a mile or more and foraging for up to 100 different kinds of animals (and some plants).

Lobster blood usually has very little color, although when exposed to air it turns pinkish or red. When cooked, however, it becomes white and “sweats” out of the meat. It is the white substance that you find along the inside of the shell when you crack it open.

A male lobster is called a cock and a female a hen or chicken (when it weighs about one pound). A one-clawed lobster is called a cull. If it has no claws, it’s called a pistol.

If a lobster loses a claw or an eye, it is usually able to grow another, although the new one is usually smaller. One of the most extraordinary abilities that lobsters possess is called reflex amputation. The lobster will throw or release an appendage when stimulated by shock, fear or injury. It will later regenerate this part.

All lobsters do not have the heavy (“crusher”) claw on the same side. Those having it on the right are considered “right-handed,” and the others are “left-handed.”

Adult lobsters cannot swim forward. Lobsters can swim forward only during the end of their juvenile stage.

Lobsters that are legal to catch are usually between 5 and 8 years old. They generally measure between 3 1/4 and 5 inches along the carapace from behind the eye to the top of the tail.

5,800 licensed fishermen who collectively haul about 3 million traps up and down the Maine coast each year. Lobster is Maine’s most lucrative fishery. It has been managed by the state for more than 100 years and is one of the most regulated fisheries in the world. Only a set number of fishing licenses is available, and each fisherman is restricted to 800 traps a year.

The largest lobster ever caught in Maine measured 36 in. from nose to tail. The largest ever caught weighed just over 44 pounds; it was caught in 1977, off Nova Scotia and had a total length of 3.5 feet.