American lobster
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| American lobster | ||||||||||||||||||
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 Homarus americanus | ||||||||||||||||||
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| Homarus americanus H. Milne-Edwards, 1837 |
The American lobster is a species of lobster (scientific name Homarus americanus), also known as the northern lobster, or the Maine lobster. They thrive in cold, shallow waters where there are many rocks and other places to hide from predators. Lobsters are solitary and nocturnal.
Found along the coast of North America as far south as North Carolina, they are famously associated with the colder waters around the Canadian Maritimes, Newfoundland and Labrador and Maine, where they can grow to enormous sizes. They commonly range from 20cm to 60cm in length and 0.5kg to 4kg in weight, but have been known to reach lengths of well over 1 meter and weigh as much as 16kg.
The adult lobster's main natural enemy is the codfish, but other enemies include haddock, flounder, and other lobsters. Overfishing of cod in the early 20th century has allowed the lobster population to grow enormously.
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Molting and Mating
Lobsters shed their shells 2-3 times per year while juvenile, but only once a year or less often when fully mature, about 4 to 7 years old. When the lobster gets near its next shedding period, it will start to grow a new shell underneath the current one. The outer shell will become very hard and darken, becoming covered with black marks that look like scratches. (They are now known, very unimaginitively, as hardshells.) The line that runs along the back of the lobster's carapace will begin to split, and the two halves of the shell will fall away. Claws and tail will be pulled out from the old outer shell, as the inner shell is very malleable. The old shell is often eaten for calcium recovery and the leftovers are sometimes buried.
Females can only mate right after molting, but larger females can store sperm for several batches of eggs from a single coupling. All females store the sperm to fertilize eggs later, not at the time of copulation. While getting ready to molt the female will find the den of a suitable male and visit it several times. When finally ready to molt the female will do so in that den. After the molt the male will wait for the shell to start to harden, gently stroking the paper thin new shell with his large antennae. After several minutes male will raise himself on his claws and tail, then use his legs to flip over the female and get on top. The male has a pair of hardened swimmerets, or fins on the bottom, that match a pair of swimmerets on the female which have an opening between them. The sperm, contained in a gelatinous blob called a spermatophore slides down notches in the male's swimmerets into the female. The outside end of the spermatophore hardens to block the hole. The receptacle on the female is part of her shell so she will need to use the sperm before her next molt or lose it. The male dismounts and then may eat the female's shell. The female will then stay in the den for several days while her shell hardens more. Lobsters do not mate for life, contrary to some myths. The female seeks the most alpha male she can find, and the male will mate with as many females as he can.
In the first two weeks after molting, lobsters are very vulnerable, as their shells are so soft they can neither move very fast nor defend themselves with their claws. (At this point, they are ofter referred to as "turds" in the industry.) They will often fall prey to other lobsters, especially egg-bearing females, who become very defensive when carrying their eggs.
Anatomical Features
Antennae
The long antennae are used to feel the area around a lobster, and appear to be more useful than the eyes.
Antennules
The shorter antennules are used for smelling. By having a pair of olefation organs, a lobster can locate the direction a smell is coming from much the same way we can hear the direction a sound comes from. In addition to sensing the presence of a smell, the antennules can judge water speed to improve direction finding.
Eyes
The eyes of these lobsters are different from almost all other animals. Rather than using lenses to focus light on sensitive cells, narrow tapered channels lined with a crystalline material reflect the light on the retinal cells. This same design is proving useful for focusing x-rays and other hard to refract light -- as in the namesake Lobster-ISS x-ray telescope.
Mouth
The lobster's mouth is used for more than eating. For burrowing it can be shaped into a wedge and used to push gravel and sand, and used to carry small rocks away. A lobster can even pull itself around by its mouth, if it has lost both claws and all legs to fighting.
Legs and Claws
The first pair of a lobster's ten legs are the called the claws and are usually used for hunting and fighting, not locomotion. The other eight legs are used for walking.
At first the claws of a lobster are both identical, but with use the lobster will start to favor one over the other. The favored claw will get bigger and be filled with primarily slow-acting muscle tissue which cannot react quickly, but does not tire quickly either. This is the crusher claw. The other claw, the pincher, will develop fast-acting muscle tissue useful for grabbing prey quickly. During lobster to lobster fights, one typical move is claw lock where the two lobsters will grab each other's crusher claw and have a showdown of muscle and shell strength.
Bladder
Lobsters have not one, but two urinary bladders, in the curious location of on either side of the head. Lobsters use scents to communicate who and where they are, and those scents are in the urine as in dogs. But while a dog will just mark places, lobsters have strong muscles to project long (up to 1.5 meters) plumes of urine in front of them and do some when they detect a rival or a potential mate in the area. Lobsters also urinate continually while at the doors of their hiding places to indicate who is inside.
Fighting
Lobsters tend to be solitary animals. The only time they peacefully share a burrow or other enclosed area is for mating. Other times when two lobsters meet, they will size each other up. If one is clearly bigger or stronger, the weaker one will retreat. A well matched pair will move through a ritualized series of aggressive displays until one gives up. These start with whipping antennae at each other, then shoving each other around with their claws, then a claw crushing show of strength called claw lock, and lastly flipping the opponent and trying to kill it. However, at any point before the end a lobster can back-off, admiting defeat, and the victor will usually not progress further. After this the loser lobster will be able to recognize the victor for up to about a week and will immediately back out of a fight.
An exception to this ritual order occurs with egg-bearing females. These lobsters are more solitary than usual, and will skip preliminary steps and go for a kill when possible.
Eggs
Eggs are green, and very small, about 1 mm in diameter. They are carried by the female on the underside of the tail for a period of about one month, whereupon they are released over several days and hatch. The number of eggs carried by a single female can range well into the tens of thousands, but the survival rate is very low, speculated at around 0.1 percent. Older females produce vastly more eggs than younger ones. In one observation (Francis Herrick, in the 1890s) 5-inch (13 cm) females were found to have about 4,000 eggs, while 10 inch (25 cm) ones produced about 50,000 eggs.
Eggs and newly hatched lobsters can by carried very long distances by ocean currents. Within the egg lobsters molt thirty-five times. At the time of hatching, the larva still looks more like a shrimp than a lobster. For several weeks, the larva floats near the surface of the sea, eating and growing. It has small fins that allow some movement, but not real swimming. The final juvenile stage, the postlarva stage, has been called the "superlobster" by some. It is the only time in a lobster's life that it can swim forward, an act which bears some resemblance to Superman flying. At this age the lobster is about 2 cm long. This stage lasts a week or two, during which the lobster will swim during the day, at speeds of up to 20 cm per second -- fast enough to cover 10 km per day. The superlobster will seek a rocky bottom with good hiding places. Without anywhere to hide it quickly falls prey to small fish, such as sculpin and cunner.
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For a lobster to be kept by fishermen in the United States, the carapace must span at least 3 and 1/4 inches (8.255 cm) between the eye socket and the first tail joint. In Maine, there is also a legal maximum of 5 inches (12.7 cm), but in some states, such as Massachusetts, there is none. To protect known breeding females, lobsters that are 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". The maixmum size in Maine ensures that there will be older males to mate with the protected females.
Lifespan
Because lobsters molt, it is extremely difficult to determine lobster's age. However, many lobsters live up to 50 years.
Lobsters as a food
Lobsters are a popular food, commonly boiled or steamed; for either method, they must be alive until they are cooked to avoid food poisoning. They can survive out of water for up to two days if kept refrigerated.
Lobster on its own is very low fat but not suitable for low sodium diets. One common way of serving lobster tail is in surf and turf.
Lobsters have a greenish or brownish organ called the tomalley that performs the functions of the liver and pancreas in a human, i.e. it filters out toxins from the body. Some diners consider it a delicacy, but others avoid it, considering it a toxin source.