Homarus Americanus

The American lobster (''Homarus americanus'') is a species of lobster found on the Atlantic coast of North America, chiefly from Labrador to New Jersey. It is also known as Atlantic lobster, Canadian lobster, true lobster, northern lobster, Canadian Reds, or Maine lobster. It can reach a body length of , and a mass of over , making it not only the heaviest crustacean in the world, but also the heaviest of all living arthropod species. Its closest relative is the European lobster ''Homarus gammarus'', which can be distinguished by its coloration and the lack of spines on the underside of the rostrum. American lobsters are usually bluish green to brown with red spines, but several color variations have been observed.

Distribution

''Homarus americanus'' is distributed along the Atlantic coast of North America, from Labrador in the north to Cape Hatteras, North Carolina, in the south. South of New Jersey, the species is uncommon, and landings in Delaware, Maryland, Virginia and North Carolina usually make up less than 0.1% of all landings. A fossil claw assigned to ''Homarus americanus'' was found at Nantucket, dating from the Pleistocene. In 2013, an American lobster was caught at the Farallon Islands off the coast of California. It has been introduced to Norway and potentially Iceland.

Description

''Homarus americanus'' commonly reaches long and weighs in weight, but has been known to weigh as much as , making this the heaviest crustacean in the world. Together with '' Sagmariasus verreauxi'', it is also the longest decapod crustacean in the world; an average adult is about long and weighs . The longest American lobsters have a body (excluding claws) long. According to Guinness World Records, the heaviest crustacean ever recorded was an American lobster caught off Nova Scotia, Canada, weighing .

The closest relative of ''H. americanus'' is the European lobster, ''Homarus gammarus''. The two species are very similar, and can be crossed artificially, although hybrids are unlikely to occur in the wild since their ranges do not overlap. The two species can be distinguished by several characteristics:
*The rostrum of ''H. americanus'' bears one or more spines on the underside, which are lacking in ''H. gammarus''.
*The spines on the claws of ''H. americanus'' are red or red-tipped, while those of ''H. gammarus'' are white or white-tipped.
*The underside of the claw of ''H. americanus'' is orange or red, while that of ''H. gammarus'' is creamy white or very pale red.

Head

The antennae measure about long and split into Y-shaped structures with pointed tips. Each tip exhibits a dense zone of hair tufts staggered in a zigzag arrangement. These hairs are covered with multiple nerve cells that can detect odors. Larger, thicker hairs found along the edges control the flow of water, containing odor molecules, to the inner sensory hairs. The shorter antennules provide a further sense of smell. By having a pair of olfactory organs, a lobster can locate the direction a smell comes from, much the same way humans can hear the direction a sound comes from. In addition to sensing smells, the antennules can judge water speed to improve direction finding.

Lobsters have two urinary bladders, located on either side of the head. Lobsters use scents to communicate what and where they are, and those scents are in the urine. They project long plumes of urine in front of them, and do so when they detect a rival or a potential mate in the area.

Thorax

The first pair of pereiopods (legs) is armed with a large, asymmetric pair of claws. The larger one is the "crusher", and has rounded nodules used for crushing prey; the other is the "cutter" or "gripper", which has sharp inner edges and is used for holding or tearing the prey. Whether the crusher claw is on the left side or right side of its body determines whether a lobster is left or right handed.

Coloration

The normal coloration of ''Homarus americanus'' is bluish green to brown with red spines due to a mixture of yellow, blue, and red pigments that occur naturally in the shell. On rare occasions these colors are distorted due to genetic mutations or conditions creating a spectacle for those who catch them. In 2012 it was reported that there has been an increase in these "rare" catches due to unclear reasons. Social media influence making reporting and sharing more accessible to a drop in predator populations have been suggested as possible reasons. The lobsters mentioned below thus usually receive media coverage due to their rarity and eye appeal.

Life cycle

Mating only takes place shortly after the female has molted and her exoskeleton is still soft. The female releases a pheromone which causes the males to become less aggressive and to begin courtship, which involves a courtship dance with claws closed. Eventually, the male inserts spermatophores (sperm packets) into the female's seminal receptacle using his first pleopods; the female may store the sperm for up to 15 months.

The female releases eggs through her oviducts, and they pass the seminal receptacle and are fertilized by the stored sperm. They are then attached to the female's pleopods (swimmerets) using an adhesive, where they are cared for until they are ready to hatch. The female cleans the eggs regularly and fans them with water to keep them oxygenated. The large telolecithal eggs may resemble the segments of a raspberry, and a female carrying eggs is said to be "in berry". Since this period lasts 10–11 months, berried females can be found at any time of year. In the waters off New England, the eggs are typically laid in July or August, and hatch the following May or June. The developing embryo passes through several molts within the egg, before hatching as a metanauplius larva. When the eggs hatch, the female releases them by waving her tail in the water, setting batches of larvae free.

The metanauplius of ''H. americanus'' is long, transparent, with large eyes and a long spine projecting from its head. It quickly molts, and the next three stages are similar, but larger. These molts take 10–20 days, during which the planktonic larvae are vulnerable to predation; only 1 in 1,000 is thought to survive to the juvenile stage. To reach the fourth stage – the post-larva – the larva undergoes metamorphosis, and subsequently shows a much greater resemblance to the adult lobster, is around long, and swims with its pleopods. At this stage, the lobster's claws are still relatively small so they rely primarily on tail-flip escapes if threatened.

After the next molt, the lobster sinks to the ocean floor and adopts a benthic lifestyle. It molts more and more infrequently, from an initial rate of ten times per year to once every few years. After one year it is around long, and after six years it may weigh . By the time it reaches the minimum landing size, an individual may have molted 25–27 times, and thereafter each molt may signal a 40%–50% increase in weight, and a 14% increase in carapace length. If threatened, adult lobsters will generally choose to fight unless they have lost their claws.

Ecology

The American lobster thrives in cold, shallow waters where there are many rocks and other places to hide from predators. It typically lives at a depth of , but can be found up to below the surface.

Diet

The natural diet of ''H. americanus'' is relatively consistent across different habitats. It is dominated by mollusks (especially mussels), echinoderms and polychaetes, although a wide range of other prey items may be eaten, including other crustaceans, brittle stars and cnidarians. Lobsters in Maine have been shown to gain 35–55% of their calories from herring, which is used as bait for lobster traps. Only 6% of lobsters entering lobster traps to feed are caught.

Diseases

Bacterial

Gaffkaemia or red-tail is an extremely virulent infectious disease of lobsters caused by the bacterium ''Aerococcus viridans''. It only requires a few bacterial cells to cause death of otherwise healthy lobsters. The "red tail" common name refers to a dark orange discoloration of the ventral abdomen of affected lobsters. This is, in fact, the hemolymph or blood seen through the thin ventral arthrodial membranes. The red discoloration comes from astaxanthin, a carotenoid pigment exported to the blood during times of stress. The same sign is also seen in other diseases of lobsters and appears to be a nonspecific stress response, possibly relating to the antioxidant and immunostimulatory properties of the astaxanthin molecule.

Epizootic shell disease is a bacterial infection which causes black lesions on the lobsters' dorsal carapaces, reducing their saleability and sometimes killing the lobsters.

Limp lobster disease caused by systemic infection by the bacterium ''Vibrio fluvialis'' (or similar species) causes lobsters to become lethargic and die.

Parasitic

Paramoebiasis is an infectious disease of lobsters caused by infection with the sarcomastigophoran (amoeba) '' Neoparamoeba pemaquidensis''. This organism also causes amoebic gill disease in farmed Atlantic salmon, ''Salmo salar''. Infection occurs throughout the tissues, causing granuloma-like lesions, especially within the ventral nerve cord, the interstices of the hepatopancreas and the antennal gland. Paramoebiasis is strongly suspected to play a prominent role in the rapid die-off of American lobsters in Long Island Sound that occurred in the summer of 1999.

Environmental

Excretory calcinosis in American lobsters in Long Island Sound was described in 2002. The disease causes mineralized calculi to form in the antennal glands and gills. These cause a loss of surface area around the gills, and the lobster eventually asphyxiates. Several reasons have been proposed for the cause of a recent outbreak of the disease. The most generally attributed factor is an increased duration of warmer temperatures in the bottom of the Long Island Sound.

Plastic pollution is harmful for American lobsters. Consumption of microplastic particles may be deadly to early-stage larvae. For later stage larvae, oxygen consumption rate decreases with high level of microplastic fibers.

Taxonomy

The American lobster was first described by Thomas Say in 1817, with a type locality of " Long-branch, part of the coast of New Jersey". The name Say chose – "''Astacus marinus''" – was invalid as a junior homonym of ''Astacus marinus'' Fabricius, 1775, which is in turn a junior synonym of ''Homarus gammarus''. The American lobster was given its current scientific name of ''Homarus americanus'' by Henri Milne-Edwards in his 1837 work ' (''"Natural History of the Crustacea"''). The common name preferred by the Food and Agriculture Organization is "American lobster", but the species is also known locally as the "northern lobster", "Maine lobster" or simply "lobster".

As food

American lobsters are a popular food. They are commonly boiled or steamed. Hard-shells (lobsters that are several months past their last molt) can survive out of water for up to four or five days if kept refrigerated. Soft-shells (lobsters that have only recently molted) do not survive more than a few hours out of water. Lobsters are usually cooked alive, which may be illegal in certain areas and which some people consider inhumane.

One common way of serving lobster 'tail' (actually the abdomen) is with beef, known as surf and turf. Lobsters have a greenish or brownish organ called the tomalley, which, like the liver and pancreas in a human, filters out toxins from the body. Some diners consider it a delicacy, but others avoid it because they consider it a toxin source; dislike eating innards; or are put off by its texture and appearance, that of a grainy greenish paste.

A set of nutcrackers and a long, thin tool for pulling meat from inaccessible areas are suggested as basics, although more experienced diners can eat the animal with their bare hands or a simple tool (a fork, knife or rock). Eating a lobster can get messy, and most restaurants offer a lobster bib. Meat is generally contained in the larger claws and tails, and stays warm quite a while after being served. There is some meat in the legs and in the arms that connect the large claws to the body. There is also some small amount of meat just below the carapace around the thorax and in the smaller legs.

North American lobster industry

Most lobsters come from the northeastern coast of North America, with the Atlantic Provinces of Canada and the U.S. state of Maine being the largest producers. They are caught primarily using lobster traps, although lobsters are also harvested as bycatch by bottom trawlers, fishermen using gillnets, and by scuba divers in some areas. Maine prohibits scuba divers from catching lobsters; violations are punishable by fines of up to $1000. Maine also prohibits the landing of lobsters caught by bottom trawlers and other "mobile gear". Massachusetts offers scuba divers lobster licenses for a fee, and they are only available to state residents. Rhode Island also requires divers to acquire a permit.

Lobster traps are rectangular cages made of vinyl-coated galvanized steel mesh or wood, with woven mesh entrances. These are baited and lowered to the sea floor. They allow a lobster to enter, but make it difficult for the larger specimens to turn around and exit. This allows the creatures to be captured alive. The traps, sometimes referred to as "pots", have a buoy floating on the surface, and lobstermen check their traps between one and seven days after setting them. The inefficiency of the trapping system has inadvertently prevented the lobster population from being overfished. Lobsters can easily escape the trap, and will defend the trap against other lobsters because it is a source of food. An estimated 10% of lobsters that encounter a trap enter, and of those that enter 6% will be caught.

United States

In the United States, the lobster industry is regulated. Every lobster fisher is required to use a lobster gauge to measure the distance from the lobster's eye socket to the end of its carapace: if the lobster is less than long, it is too young to be sold and must be released back to the sea. There is also a legal maximum size of in Maine, meant to ensure the survival of a healthy breeding stock of adult males, but in parts of some states, such as Massachusetts, there is none. Also, traps must contain an escape hole or "vent", which allows juvenile lobsters and bycatch species to escape. The law in Maine and other states dictates a second large escape hole or "ghost panel" must be installed. This hole is held shut through use of degradable clips made of ferrous metal. Should the trap become lost, the trap eventually opens, allowing the catch to escape.

To protect known breeding females, lobsters caught carrying eggs are to be notched on a tail flipper (second from the right, if the lobster is right-side up and the tail is fully extended). Following this, the female cannot be kept or sold, and is commonly referred to as a "punch-tail" or as "v-notched". This notch remains for two molts of the lobster exoskeleton, providing harvest protection and continued breeding availability for up to five years.

Canada

In Canada, the Department of Fisheries and Oceans is responsible for the governance of fisheries under the authority of th
Fisheries Act
The governance structure also includes various other acts, regulations, orders and policies. American Lobster is fished in Canada by lobster licence holders hailing from ports located in provinces on Canada's east coast. Lobster is Canada's most valuable seafood export, worth over CAD$2 billion in 2016.

Management

American lobster tends to have a stable stock in colder northern waters, but gradually decreases in abundance moving southward. To manage lobster populations, more regulations and restrictions, geared towards achieving sustainable populations, are implemented gradually southward.

Genetics

Currently there is no published genome for the American lobster, although a transcriptome was published in 2016.

See also

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References

Further reading

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External links

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{{Taxonbar, from=Q37668

Crustaceans described in 1837
Commercial crustaceans
Crustaceans of North America
Crustaceans of the Atlantic Ocean
Crustaceans of the United States
Edible crustaceans
Extant Pleistocene first appearances
Least concern biota of North America
Least concern biota of the United States
Natural history of Maine
Pleistocene animals of North America
True lobsters