Lobsters: Characteristics, Colors, Behavior

Home | Category: Crustaceans (Crabs, Lobsters and Shrimp)


Durer drawing of a lobster
There are two main types of lobsters: 1) those with large claws, like the American lobster; and 2) spiny-type lobsters without big claws. Spiny-type lobsters including the Caribbean spiny lobster; Rock lobsters or crayfish, associated with Australia, are similar to these. Spiny lobsters are generally found in tropical oceans while lobsters with claws are found in colder seas.

Lobsters go through larval stage. Superlobster is a term sometimes used to describe thumb-nail-size larvae just before they advance to the adult stage. The look like lobsters but can swim like fish. It is the only time in their lives that lobsters can swim forward. Their primary goal is to find a crevice to hide in. After that goal is achieved the lobster spends the next several years hiding there.

The largest lobster on record is an American lobster trapped off Nova Scotia in 1977. It weighed 44 pounds and 6 ounces and was 3½ feet (over a meter) long. 37.4 pounds: The largest lobster ever caught in the U.S. weighed 17 kilograms (37.4) pounds. The lobster, named “Big George”, was caught off Cape Cod. These days it is unusual to catch one that weighs more than three pounds. Occasionally you get bright blue American lobsters due to a genetic defect.

Lobsters are opportunistic feeders, feeding on whatever prey is most available, so their diet varies regionally. Larvae and postlarvae are carnivorous and eat zooplankton (tiny floating animals) during their first year. Adults are omnivorous, feeding on crabs, mollusks, worms, sea urchins, sea stars, fish, and macroalgae. In general, a variety of bottom-dwelling species feed on lobster, including fish, sharks, rays, skates, octopuses, and crabs. Young lobsters are especially vulnerable to predators. Large, hard-shelled lobsters may be immune to predators (except humans)..

New species of lobster have been discovered in the ocean. One is pink and fuzzy. Lobsters have not been raised on aquaculture farms because the cost of getting them to marketable size is too high.

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Lobster Physical Characteristics

lobster diagram, source: state of Maine

A lobster's body is divided into twenty-one segments: six segments from the head region, eight make up the thorax (mid-section), and seven comprise the abdomen (often called the tail). As members of the order Decapoda (meaning "ten feet"), lobsters have ten legs. Five pairs of jointed legs extend from the thorax region. The first pair of these legs extends towards the head and may have claws (chela) on the end.

Lobsters are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature) and heterothermic (have a body temperature that fluctuates with the surrounding environment). They can reach enormous sizes like that mentioned above in part because they never stop growing. Humans produce an enzyme named telomerase in the early stages of life that aids in growth; lobsters never stop producing this enzyme. That means that the biggest lobsters ever are also the oldest. The reason even that lobsters don’t get even larger is partly explained by the amount of energy needed to molt (See Below) becomes too great and molting stops. [Source: Jesse Elop, A-Z Animals, April 7, 2023]

Lobsters can walk slowly forward but move more quickly backwards with jet propulsion and quick movements of its tail. At night lobster search for food while fish that are active during the day sleep in some of the caves occupied by lobsters.

Lobsters have compound eyes that move about on stalks and long antennae that sense water movements. The antennae, claws and body are covered by thousands of sensory hairs that are used to find food and detect predators. Using high speed video, dyes and lasers, scientists discovered that hairs trap “odor plumes,” and by moving their antennae lobsters collect a wide variety of data based on the “odor plumes.” The Navy is trying the technique as a possible way to detect mines and explosives in the sea.

Three stomachs make up the digestive system, which is within the cephalothorax (the head and thorax). The first stomach (forgut) grinds food into small particles with grinding teeth. The second stomach (midgut) has glands to digest particles. The glands are the green portion of the lobster eaten by some humans (called the "tomalley"). The third stomach (hindgut) receives non-absorbed particles which are passed to the retum and anus. /=\

Lobster Molting

Lobsters periodically molt — shed their shells — to make way for their growing bodies. It can take several weeks to grow a new shell and this is when the lobsters are most vulnerable. If a lobster loses a limb. A new one grows back. Molting of lobsters can be an arduous task.

When a lobster is ready to molt, its body absorbs the mineral salts that had hardened its shell, drawing the salts further into its skin. When the shell softens, the lobster is able to break it and slide out. The lobster takes in more water and thus swells in size.

ancient lobster claw rhyton
The new shell is already covering its body but takes a few days to harden. During this period the lobster stays in seclusion to avoid predators. Each time a lobster molts its body can grow 10-15 percent in size. Newly hatched lobsters molt for the first time within the first week, and three more times within the first month. [Source: Don Lydon, Animal Diversity Web (ADW)]

The lobster exoskeleton includes teeth in the stomach to grind food, This is ripped out before the shell come free. Sometimes lobsters can not successfully shed their shells and die. Lobsters often eat voraciously after they molt, often devouring their own recently vacated shells. Eating their shell replenishes lost calcium and helps harden their new shell. Lobsters molt about 20 to 25 times over a period of 5 to 8 years between the time they hatch and when they are able to reproduce.

Lobster Behavior

Lobsters are nocturnal (active at night), motile (move around as opposed to being stationary), sedentary (remain in the same area), solitary, territorial (defend an area within the home range), and have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). [Source: Don Lydon, Animal Diversity Web (ADW) /=]

Lobsters generally live alone and are very territorial. They spends most of the day inside their burrow and only leave it if food is nearby. At night they wander the ocean floor, and may venture into the intertidal zone when tides are high. If a predator approaches, it quickly retreats back into the safe cover of its burrow.

Lobsters rarely interact with each other. According to Animal Diversity Web: Studies show that when introduced into a community, lobsters have a social hierarchy. This social system plays a role when mating season comes along. A male who has a higher status among its neighbors will have a secured shelter and will be able to mate with multiple females. A theory as to the mechanisms that maintain this social hierarchy is that the lobsters recognize each other by the chemicals they excrete. A lobster has been show to recognize another lobster with which it has met before for up to two weeks. Lydon, Animal Diversity Web (ADW) /=]

Lobsters communicate with touch and chemicals usually detected by smelling. They also employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species) and sense using chemicals usually detected with smelling or smelling-like senses. Their eyes can only detect motion in dim light. The second segment of the head has anntenules with delicate hairs that have more than 400 types of chemoreceptors. The lobsters can detect other species, potential mates, prey and predators with the receptors.

A Norwegian study found that lobsters most likely do not feel pain when they are dropped in hot water. Other studies have turned up no evidence of anything resembling pain receptors. The lobster nervous system is said about as complex as that of a fruit fly. Studies by Robert Elwood of Queen's University Belfast with crabs and prawns disputes these claims; he has found that crustaceans do feel pain and are more complex than are given credit for.

Lobster Reproduction and Development

Usually, lobsters mate after the females molt. Males deposit sperm in the soft-shelled females. The female stores the sperm internally for up to a year. Females can have 5,000 to more than 100,000 eggs, depending on their size. The eggs are fertilized as females release them on the underside of their tails, where they carry the eggs for nine to 11 months. Egg-bearing females move inshore to hatch their eggs during late spring or early summer.

Females reach sexual maturity at about five years of age. They employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating). Mating must occur within 48 hours after the female molts, and the process usually lasts about a minute. The female spawn her eggs between one month and two years after mating, at which time they become fertilized by sperm that has been stored. An 18 centimeter lobster lays about 3,000 eggs and a 45 centimeter one lays around 75,000 eggs. After spawning, females secretes a glue and fastens their eggs to their swimmerets (fringed paddles that hang from abdomen) and carry them for up to 12 months.

Describing lobster sex Trevor Corson, author of a book about lobsters, told U.S. News and World Report, “The female sprays urine into the male’s apartment, basically drugging him into submission. Then she move in with him and get PMS — premolting syndrome. She gets irritable, shoves a lot of gravel around the place. He is understanding and tender; he waits until she molts, until her legs can stand, then he turns her on her back and mounts her. The female has a seminal receptacle, a kind of fanny pac. the male guides his swimmerets own into the pouch. Then he rolls some sperm packets into a plug for her seminal receptacle so no other males can get there.”

Female carry the eggs underneath her tail for about 10 to 11 months until they hatch. The pelagic (free-swimming) larvae look nothing like adults when the eggs hatch. The larvae molt three times in 15 an 18 days. Only about 1/10 of one percent of the young survive after four weeks, mainly due to predation. After molting a fourth time they resemble adults and settle to the bottom. When they are one year old they have molted 14 to 17 times and are five to 7.5 centimeters (two to three inches) long. They reach adulthood around the age of five.

range of lobster and lobster-like animals: red: American and European lobsters; yellow: spiny lobsters

Lobsters go through exceptional growth during their lifetime. When they first hatch, a lobster weighs less than one tenth of a gram. By the time they are full adults, they can reach a weight of up to 10 kilograms. This growth is an increase of 100,000 times. Lobsters achieve this growth by going through periods called molts.

American Lobsters

American lobsters (Scientific name: Homarus americanus) are large crustaceans with 10 legs, two of which are large, strong claws. Live ones in the sea are not red like the cooked ones in restaurants and grocery stores. Most are either olive-green or greenish-brown. Some have orange, reddish, dark green, or black speckles and bluish colors in the joints of their appendages. American lobsters can live a long time. It’s difficult to determine their exact age because they shed their hard shell when they molt, leaving no evidence of age. But scientists believe some American lobsters may live to be 100 years old.[Source: Don Lydon, Animal Diversity Web (ADW) /=]

American lobsters are found in the northwest Atlantic Ocean from Labrador to Cape Hatteras. They’re most abundant in coastal waters from Maine through New Jersey, and are also common offshore to depths of 700 meters (2,300 feet) from Maine through North Carolina. They live on the ocean floor and thrive in a variety of habitats as long as there is a burrow or crevice for cover. Coastal lobsters like rocky areas where they can readily find shelter, although they’re sometimes found in mud bottoms where they can burrow. Offshore populations are most abundant along the edge of the continental shelf near underwater canyons. [Source: NOAA]

Near the coast, small lobsters do not travel much, but larger ones may travel extensively. Offshore lobsters migrate during the spring anywhere from 80 to 300 kilometers (50 to 190) miles. Young lobsters seem to prefer settling in areas with cobble. There is still a lot about lobsters that remains a mystery. For example, there have been record harvests of American lobster in the Gulf of Maine but empty traps in further southern around Cape Cod. No one knows why. Some think it is related to overfishing of fish such as cod, haddock and hake that feed on lobsters.

American Lobster Characteristics and Behavior

The American lobster is the largest species of lobster. Although it reach lengths over a meter and weigh more than 20 kilograms (44 pounds), the lobsters caught commercially are generally no more than 25 centimeters (10 inches) in length and weighs about 0.5 kilograms (one pound)

American lobsters waiting to be purchased

One claw is a big-toothed crusher claw for pulverizing shells, and the other is a finer-edged ripper claw, resembling a steak knife, for tearing soft flesh. Male and female lobsters can be distinguished by the first pair of swimmerets (pleopods) on the upper portion of the underside of the tail. The male swimmerets are larger and more rigid. The female swimmerets are softer, smaller, and have rounded edges.

American Lobsters are solitary. Individuals stay among the rocks during the day to avoid predators (mainly cod) and venture out at night in search for food. They do most of their feeding at night. They usually scavenge, feed on dead animals and root up and crush mollusks, but are capable of capturing more fast-moving prey and do occasionally feed on plant material. Their diet includes clams, crabs, snails, small fish, algae and plants such as eelgrass. Since lobsters sometimes eat their own molted shell they have been described as cannibalistic, Although real cannibalism has never been recorded in the wild, lobsters have been observed eating each other in captivity. /=\

They are primarily carnivores (mainly eat meat or animal parts) piscivores (eat mainly eats fish), eats non-insect arthropods molluscivores (mainly eat mollusks), scavenger omnivores (eats a variety of things, including plants and animals), Animal foods include fish carrion mollusks aquatic crustaceans. Among the plant foods they eat are algae macroalgae

Blue and Yellow Lobsters

Some lobsters become blue as a result of a genetic mutation that causes the crustacean to produce an excessive amount of a particular protein. The protein and a red carotenoid molecule known as astaxanthin combine to form a blue complex known as crustacyanin, giving the lobster its blue color. There is an estimated 1 in 2 million chance of this occurring. David Spiegelhalter from the University of Cambridge calculated these odds based on the fact that roughly 200 million lobsters are caught in the North Atlantic every year and around 100 or 200 of them are blue. [Source: Wikipedia]

The estimated odds of catching a live red lobster are 1 in 10 million. In 2016, Bob Bayer, director of the Lobster Institute at the University of Maine, said that "the genetics of red lobsters are not as well understood" when compared to blue lobsters. Yellow lobsters are the result of an unspecified rare genetic mutation. Orange lobsters are caused by a lack of proteins which help to bond the different pigments. Most orange lobsters are described as "calico", nad have a mixture of orange and black colors. The odds of catching a yellow lobster are calculated to be 1 in 30 million.

Several lobsters have been caught that were one color on one side of their body and a different color on the other side. According to a researcher at the University of Rhode Island, this split colorization is the result of a genetic condition which causes both sides of the lobster to develop independently. Split-colored lobsters often show sexual characteristics of both sexes, with exceptions. The chance of finding one is estimated at 1 in 50 million. Albino white lobsters are the rarest of all. It is estimated that 1 in 100 million lobsters are albino, meaning they lack all colored pigments. "White" lobsters that still have trace colors present in the shell are similarly rare; these are not categorized as albino but rather as leucistic. Neither of these genetic conditions are unique to lobsters.

Humans, Lobsters and Conservation

American lobster is listed as having No special status on the International Union for Conservation of Nature (IUCN) Red List and the Convention on the International Trade in Endangered Species (CITES).

According to Animal Diversity Web: Although this species is not Endangered, conservation efforts have been implemented to preserve lobster populations from overfishing. Laws regulate the size of lobsters taken, which increases the number of females reaching sexual maturity and reproducing before being harvested.

Other regulations include limiting the number of traps set, limits on lobstering licenses, and times of the year when lobsters are harvested. Another volunteer program implemented is cutting a "V" notch in the tail when a female carrying eggs is trapped. She is returned to the sea and if caught again is not supposed to be harvested since she is a known egg producer. [Source: Don Lydon, Animal Diversity Web (ADW)]

Scientists, managers, and fishermen are concerned about the habitat conditions for American lobster in inshore Southern New England waters, particularly in Long Island Sound. Scientists believe that a combination of warmer water temperatures, hypoxia (low dissolved oxygen levels), and other stress factors resulted in lobster die-offs in western Long Island Sound in late 1999 and in 2002. If these conditions continue, future die-offs are possible. Researchers also believe that increased water temperatures in Southern New England may be driving lobsters to cooler offshore waters and disrupting the settlement of larvae in traditional coastal areas..

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023

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