| American lobster | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Family: | Nephropidae |
| Genus: | Homarus |
| Species: | H. americanus |
| Binomial name | |
| Homarus americanus H. Milne-Edwards, 1837 | |
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| Natural range ofH. americanus (blue) | |
| Synonyms[2] | |
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TheAmerican lobster (Homarus americanus) is aspecies oflobster found on theAtlantic coast ofNorth America, chiefly fromLabrador toNew Jersey. It is also known asAtlantic lobster,Canadian lobster,true lobster,northern lobster,Canadian Reds,[3] orMaine lobster.[4][5] It can reach a body length of 64 cm (25 in), and amass of over 20 kilograms (44 lb), making it not only the heaviestcrustacean in the world, but also the heaviest of all livingarthropod species. Its closest relative is the European lobsterHomarus gammarus, which can be distinguished by its coloration and the lack of spines on the underside of therostrum. American lobsters are usually bluish green to brown with red spines, but several color variations have been observed.
Homarus americanus is distributed along theAtlantic coast ofNorth America, fromLabrador in the north toCape Hatteras,North Carolina, in the south.[6] South ofNew Jersey, the species is uncommon, and landings inDelaware,Maryland,Virginia and North Carolina usually make up less than 0.1% of all landings.[7] Afossilclaw assigned toHomarus americanus was found atNantucket, dating from thePleistocene.[8][9] In 2013, an American lobster was caught at theFarallon Islands off the coast ofCalifornia.[10] It has beenintroduced toNorway[11] and potentiallyIceland.[12]
Homarus americanus commonly reaches 200–610 millimetres (8–24 in) long and weighs 0.45–4.08 kilograms (1–9 lb) in weight, but has been known to weigh as much as 20 kg (44 lb), making this the heaviest crustacean in the world.[13] Together withSagmariasus verreauxi, it is also the longestdecapod crustacean in the world;[2] an average adult is about 230 mm (9 in) long and weighs 680 to 910 g (1.5 to 2 lb). The longest American lobsters have a body (excluding claws) 64 cm (25 in) long.[2] According toGuinness World Records, the heaviestcrustacean ever recorded was an American lobster caught off Nova Scotia, Canada, weighing 20.1 kg (44.4 lb).[13][14]
The closest relative ofH. americanus is the European lobster,Homarus gammarus. The two species are very similar, and can be crossed artificially, althoughhybrids are unlikely to occur in the wild since their ranges do not overlap.[15] The two species can be distinguished by several characteristics:[16]
Theantennae measure about 51 mm (2 in) longand 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.[17] The shorterantennules provide a further sense of smell. By having a pair ofolfactory 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 twourinary bladders, located on either side of the head. Lobsters use scents to communicate what and where they are, and those scents are in theurine. They project long plumes of urine 1–2 meters (3 ft 3 in – 6 ft 7 in) in front of them, and do so when they detect a rival or a potential mate in the area.[18]
The first pair ofpereiopods (legs) is armed with a large, asymmetric pair ofclaws.[2] 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.[16] Whether the crusher claw is on the left side or right side of its body determines whether a lobster is left or right "handed".[19]
The normal coloration ofHomarus 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.[20][6] 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.[21] The lobsters mentioned below thus usually receive media coverage due to their rarity and eye appeal.[22]
| Color | Image | Rarity | Description |
|---|---|---|---|
| Blue |  | 1 in 2 million | Some lobsters become blue as a result of a genetic mutation that causes the lobster to produce an excessive amount of a particular protein.[23] The protein and a redcarotenoid molecule known asastaxanthin combine to form a blue complex known ascrustacyanin, giving the lobster its blue color.[24] While an estimated 1 in 2 million lobsters are blue, they may not be as rare as they are portrayed given how many lobsters are caught in a given year.David Spiegelhalter from theUniversity of Cambridge pointed out that a rough analysis shows that 200 million lobsters are caught in the North Atlantic every year. He stated that if the odds are correct then it would mean 100 of them would be blue. Spiegelhalter concluded that the catches are not all that surprising, and that these lobsters probably turn up most years.[25] In any case, when blue lobsters are caught they are either released back into the sea or placed in local aquariums.[26][27][28] |
| Red (live) |  | 1 in 10 million | Red lobster coloration is the typical result of cooking, which is caused by the chemical astaxanthin reacting with boiling water.[29] The estimated odds of catching a live red lobster are 1 in 10 million.[23][30] Director Bob Bayer from the Lobster Institute at theUniversity of Maine stated in 2016 that "the genetics of red lobsters are not as well understood" when compared to blue lobsters.[31] |
| Yellow or orange |  | 1 in 30 million | Yellow lobsters are the result of an unspecified rare genetic mutation, while orange lobsters are caused by a lack of proteins which help to bond the different pigments.[23][32] Most orange lobsters are described as "calico", with a mixture of orange and black colors present.[32][33] Yellow and orange lobsters are typically placed into aquariums, as predators can easily spot them if they are released back into the wild.[20][34] The odds of catching a yellow lobster stand at 1 in 30 million.[35] |
| Split |  | 1 in 50 million | Several lobsters have been caught that show a different color on the left and right side of the body. According to a researcher at theUniversity of Rhode Island, this split colorization is the result of a genetic condition which causes both sides of the lobster to develop independently.[36] Split-colored lobsters often show sexual characteristicsof both sexes, with exceptions.[37][38] The chance of finding a split-colored lobster is estimated at 1 in 50 million.[23] |
| Iridescent or white (albino) |  | 1 in 100 million | It is estimated that 1 in 100 million lobsters arealbino, entirely lacking in colored pigments.[23][39] "White" lobsters that still have trace colors present in the shell are similarly rare; these are not categorized as albino but rather asleucistic.[40] Neither of these genetic conditions are unique to lobsters. |
Mating only takes place shortly after the female hasmolted and herexoskeleton is still soft.[41] The female releases apheromone which causes the males to become less aggressive and to begincourtship, which involves a courtship dance with claws closed. Eventually, the male insertsspermatophores (sperm packets) into the female's seminal receptacle using his firstpleopods; the female may store the sperm for up to 15 months.[41]
The female releaseseggs through her oviducts, and they pass the seminal receptacle and arefertilized 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.[41] The female cleans the eggs regularly and fans them with water to keep them oxygenated.[42] The largetelolecithal[43] eggs may resemble the segments of araspberry, and a female carrying eggs is said to be "in berry".[41] Since this period lasts 10–11 months, berried females can be found at any time of year.[2] In the waters offNew England, the eggs are typically laid in July or August, and hatch the following May or June.[43] The developingembryo passes through several molts within the egg, before hatching as ametanauplius larva. When the eggs hatch, the female releases them by waving her tail in the water, setting batches of larvae free.[42]
The metanauplius ofH. americanus is 8.5 mm (1⁄3 in) 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 theplanktonic larvae are vulnerable to predation; only 1 in 1,000 is thought to survive to the juvenile stage.[41] To reach the fourth stage – the post-larva – the larva undergoesmetamorphosis, and subsequently shows a much greater resemblance to the adult lobster,[43] is around13 mm (1⁄2 in) long,[41] and swims with itspleopods.[43] At this stage, the lobster's claws are still relatively small so they rely primarily on tail-flip escapes if threatened.[44]
After the next molt, the lobster sinks to the ocean floor and adopts abenthic lifestyle.[42] 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 25–38 mm (1–1.5 in) long, and after six years it may weigh 0.45 kilograms (1 lb).[41] By the time it reaches theminimum 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 incarapace length.[42] If threatened, adult lobsters will generally choose to fight unless they have lost their claws.[44]
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 4–50 m (13–164 ft), but can be found up to 480 m (1,570 ft) below the surface.[2]
The natural diet ofH. americanus is relatively consistent across different habitats. It is dominated bymollusks (especiallymussels,clams andsnails),echinoderms andpolychaetes, although a wide range of other prey items may be eaten, including other crustaceans (such ascrabs),brittle stars,cnidarians and smallfish.[45] It will also feed on dead animals, as well asalgae andeelgrass.[46] Since lobsters sometimes eat their own molted shell, they were thought to be cannibalistic, but this has never been recorded in the wild.[46] Lobsters in Maine have been shown to gain 35–55% of their calories from herring, which is used as bait for lobster traps.[47] Only 6% of lobsters entering lobster traps to feed are caught.
Gaffkaemia orred-tail is an extremely virulent infectious disease of lobsters caused by the bacteriumAerococcus viridans.[48] 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, thehemolymph or blood seen through the thin ventral arthrodial membranes. The red discoloration comes fromastaxanthin, acarotenoid 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.[49]
Limp lobster disease caused by systemic infection by the bacteriumVibrio fluvialis (or similar species) causes lobsters to become lethargic and die.[48][50]
Paramoebiasis is an infectious disease of lobsters caused by infection with the sarcomastigophoran (amoeba)Neoparamoeba pemaquidensis. This organism also causesamoebic gill disease in farmedAtlantic salmon,Salmo salar. Infection occurs throughout the tissues, causinggranuloma-like lesions, especially within the ventral nerve cord, the interstices of thehepatopancreas and the antennal gland. Paramoebiasis is strongly suspected to play a prominent role in the rapid die-off of American lobsters inLong Island Sound that occurred in the summer of 1999.[48]
Excretory calcinosis in American lobsters in Long Island Sound was described in 2002. The disease causes mineralizedcalculi 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.[51][52]
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.[53]
The American lobster wasfirst described byThomas Say in 1817, with atype locality of "Long-branch, part of the coast ofNew Jersey".[2] The name Say chose – "Astacus marinus" – was invalid as ajunior homonym ofAstacus marinus Fabricius, 1775, which is in turn ajunior synonym ofHomarus gammarus.[2] The American lobster was given its currentscientific name ofHomarus americanus byHenri Milne-Edwards in his 1837 workHistoire naturelle des Crustacés ("Natural History of the Crustacea").[2] Thecommon name preferred by theFood and Agriculture Organization is "American lobster", but the species is also known locally as the "northern lobster", "Maine lobster" or simply "lobster".[2]
American lobsters are a popular food.[55] 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.[56] Soft-shells (lobsters that have only recently molted) do not survive more than a few hours out of water. Lobsters are usually cooked alive,[57] which may be illegal in certain areas[58] and which some people consider inhumane.[59][60]
Boiling lobsters has been banned in several jurisdictions, including Switzerland, New Zealand, and parts of Italy.[61] Boiling has been deemed to cause "extreme suffering" in lobsters, who continue to show intense brain activity for 30 to 150 seconds after immersion in boiling water.[61] Slowly raising the water temperature may also cause pain in crustaceans over a longer period of time.[61]
Lobster 'tail' (actually theabdomen) is sometimes served withbeef assurf and turf.[62] Lobsters have a greenish or brownish organ called thetomalley, which, like theliver andpancreas in a human, filters outtoxins from the body.[63] 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 grainy paste texture and greenish appearance.[citation needed]
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.[64] 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.
A 2021 London School of Economics report found strong evidence to suggest that lobsters can experience pain.[61] Dr Jonathan Birch, Principal Investigator on the project, said, "After reviewing over 300 scientific studies, we concluded that cephalopod molluscs and decapod crustaceans should be regarded as sentient, and should therefore be included within the scope of animal welfare law."[65]
Following the report, octopuses, crabs and lobsters are now protected under stronger animal welfare legislation in the UK (under the Animal Welfare (Sentience) Bill).[66]
Most lobsters come from the northeastern coast of North America, with theAtlantic Provinces of Canada and theU.S. state ofMaine being the largest producers. They are caught primarily usinglobster traps, although lobsters are also harvested asbycatch bybottom trawlers, fishermen usinggillnets, 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".[67][68] 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 abuoy 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.[69]
In the United States, the lobster industry isregulated. 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 3.25 inches (83 mm) long, it is too young to be sold and must be released back to the sea. There is also a legal maximum size of 5 in (130 mm) 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.[70]
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.[71]
In Canada, theDepartment of Fisheries and Oceans is responsible for the governance of fisheries under the authority of theFisheries Act.[72] The governance structure also includes various other acts, regulations, orders and policies.[73] American lobster is fished in Canada by lobster licence holders hailing from ports located in provinces on Canada's east coast.[74] Lobster is Canada's most valuable seafood export, worth over CAD$2 billion in 2016.[75]
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.[76]
Currently there is no publishedgenome for the American lobster, although atranscriptome was published in 2016.[77]
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