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Jenny
137317.  Sun Jan 21, 2007 10:09 pm Reply with quote

All information in the following posts is gleaned from: The Secret Life of Lobsters, by Trevor Corson, pub. Harper Perennial 2005, ISBN 0060555580

Lobsters, like insects, are arthropods. Their sub-phylum is called Crustacea, because they have a shell. However, their nervous system is very like that of insects, and Maine lobster fishermen call them ‘bugs’. 150 million year-old fossil lobsters are so similar to today’s lobsters that if one was served for dinner you wouldn’t notice the difference.

The best-known lobster is Homarus americanus, but there are about fifty species. Try, for example, the hunchback locust lobster, the velvet fan lobster, the regal slipper lobster, the marbled mitten lobster, the musical furry lobster, the unicorn lobster, the buffalo blunt-horn lobster, the African spear lobster, the Arabian whip lobster and the rough Spanish lobster. With melted butter.


Last edited by Jenny on Sun Jan 21, 2007 10:28 pm; edited 1 time in total

 
Jenny
137318.  Sun Jan 21, 2007 10:13 pm Reply with quote

American lobsters are greenish-brown, and European lobsters blackish-blue, but whatever their shell colour, all lobsters turn red when boiled because protein molecules in the shell bend during cooking into shapes that absorb different wavelengths of light and end up reflecting red. Proteins from the shell of the European Homarus gammarus can be grown into brilliant blue crystals, and sometimes a genetic mutation or a lack of calcium in the diet can make American lobsters grow blue. There are genetic mutations of yellow, white, calico and even red in living lobsters, and (rarely) half and half, with a straight line down the middle of the back dividing the colours.

 
Jenny
137319.  Sun Jan 21, 2007 10:14 pm Reply with quote

The name lobster originated from the Old English loppestre, probably related to loppe, meaning spider. By the 17th century, the word had become an insult. Calling someone a lobster was like calling him a rogue, and Americans used lobsterbacks as an insult for British soldiers for more reasons than just their red coats. Two hundred years later, the insult meant somebody was a fool.

The original derivation probably goes back to the Latin locusta though. Pliny the Elder’s first century Natural History described how lobsters, when surprised, seemed to ‘disappear with a single leap or bound as a locust or grasshopper might do’, and so he called them locustae, locusts of the sea.

 
Jenny
137320.  Sun Jan 21, 2007 10:14 pm Reply with quote

Now, lobsters are a luxury item, but early New England settlers considered them junk food. William Bradford, leader of a group of early settlers, reported shame at having to serve lobster to guests instead of more respectable food. In those days of plenty, storms blew hundreds onto the beach, where farmers used them for animal feed or fertilizer. Fishermen still ate lobster though, because most fish they caught were too valuable to eat but lobster was cheap.

 
Jenny
137321.  Sun Jan 21, 2007 10:17 pm Reply with quote

Lobsters’ eyes can detect motion under low-light conditions but don’t discern much detail. However, unlike most eyes, which use lenses to refract light, lobster eyes have no lens. Instead, each eye has a grid of around thirteen thousand square ducts, open at the top, with a crystalline lining that reflects light onto retinal cells. Space scientists are using this as the basis for the design of a new X-ray-vision space telescope called Lobster-ISS because it will be mounted on the International Space Station. The angles of the mirrors inside lobster eyes are just shallow enough to redirect X-ray signals without absorbing them.

 
Jenny
137322.  Sun Jan 21, 2007 10:17 pm Reply with quote

Lobsters have sensitive touch receptors – two long antennae and thousands of minute hairs that protrude through the shells of their claws and legs, which detect the movement of water currents around them. They use their gills to draw water from around their body into the gill chambers and then expel it forward either side of the head, up to seven body lengths in front. They can also use their mouthparts to direct water to their own faces. Like houseflies, lobsters also taste with their feet.

 
Jenny
137323.  Sun Jan 21, 2007 10:19 pm Reply with quote

A lobster’s most acute sense is its sense of smell. A smaller pair of two-pronged antennae, called antennules, contains hundreds of chemical receptors that give lobsters most of their hunting and socializing skills. A lobster’s brain consists of several nerve ganglions strung together, and nearly half of their volume is dedicated to processing the signals from the antennules. Lobsters use their sense of smell to identify each other as individuals as well as to pick up pheromonal signals and track down food.

American lobsters’ bladders are in their heads, and they urinate directly in front of their faces. This stream of urine mixes with the current from the gill chambers and is carried ahead of the lobster. Thus, lobsters literally have pissing competitions. They send messages like ‘Remember me? I beat you up last night,’ or, ‘Want to have sex? I’m about to get undressed,’ by peeing in each other’s faces. The urine of a dominant male lobster exudes a level of confidence that is deeply attractive to female lobsters.

 
Jenny
137324.  Sun Jan 21, 2007 10:21 pm Reply with quote

A lobster’s shell is its exoskeleton. To grow, a lobster must shed its shell, risking predation while a new shell grows. Lobsters do this 25 times in the first five years of life, gaining up to 15% in body length and 50% in volume each time. After this, moulting is usually only twice a year. Adult lobsters moult no more than annually, and less as they grow larger. It is, however, hard to tell the age of a lobster, as they are invertebrates and thus have no internal skeleton to keep a record of growth.

The outer layer of the shell is a mixture of proteins, lipids and calcium salts. Underneath is a mixed layer of protein and chitin (the same chitin that forms the exoskeletons of insects and some arachnids, like scorpions). The third layer has a stiff calcified outer portion and a softer inner portion. Under this is a membrane, and finally the lobster’s skin.

To prevent a continual cycle of moulting and shell regrowth, glands in lobsters’ eyestalks release a hormone that inhibits moulting. The hormone is controlled by factors such as water temperature and day length. Cutting off a lobster’s eyes causes it to moult almost immediately (as well as bump into things a lot).

Before moulting, the lobster’s skin cells enlarge and secrete the beginning of a new shell under the old one, and calcium accumulates in reservoirs called gastroliths on either side of the stomach. During moulting, the lobster pumps seawater into its shell and distributes it around its body so that hydrostatic pressure forces the old shell away from the new one.

When the lining membrane bursts, the lobster is helpless for twenty minutes, and then must detach itself from its old shell. This is easier said than done. It must lose the mass of muscle in its great claws, or it cannot pull them through the shell around its wrists. Because the teeth inside its stomach that grind its food are part of the exoskeleton, the lobster must pull out the lining of its throat, stomach and anus before it can be free of the old shell. Not all lobsters survive moulting.

After this stage, the lobster digests its gastroliths in order to recycle some of the calcium from its old shell into the new one. This calcium goes to harden the tips of the legs and the cutting edges of the mouthparts, without which the lobster cannot feed. It pumps itself full of water again, to expand to a larger size than that contained by the old shell, and then eats its old shell as another source of calcium.

Over the next few days, these minerals are secreted into the new shell. When the new shell starts to thicken, the lobster shrinks back to its actual size, to give itself room to grow into the new shell.

 
Jenny
137325.  Sun Jan 21, 2007 10:22 pm Reply with quote

What do lobsters do before they mate? They get undressed.

The reproductive cycle begins when the female sheds her old shell. This enables her to mate between moults and carry the eggs until they hatch before she sheds her shell again. She has to do this, because the eggs are attached to the shell and would be lost if shed before hatching.

Most of the time, male and female lobsters are hostile to each other. If they detect each other’s scents in the water with their antennules, they will attack. However, when female lobsters shed their shells they release a sex pheromone that male lobsters find strangely arousing. In fact, as smell and taste underwater are both ways of detecting chemical molecules, the male lobster could be said to taste the female as much as smell her during this time.

In the Middle Ages, natural scientists were very puzzled by the fact that the male lobster has no penis. Later scientists took a long time (and many strange theories involving things like collapsible penises) to discover how lobsters fertilized their eggs. Things were complicated by the discovery that the female lobster has no vagina.

In 1895 a 250-page treatise called The American Lobster, its Habits and Development, by Francis Herrick, explained that a female lobster has a tiny pouch at the base of her tail, where she can store a male lobster’s sperm until she is ready to extrude her eggs. In the same position on his tail, the male lobster has a pair of hardened swimmerets with grooves along the inside edge. Herrick dissected lobster testes and discovered that male lobsters package their sperm into gelatinous capsules called spermatophores. Using their swimmerets to prop open the female’s receptacle, they ejaculate these packets down the grooves and into the pouch. The last spermatophore hardens into a plug to block the opening, to prevent another male’s sperm packages from entering.

However, despite the lack of a traditional penis-and-vagina, lobster sex involves the missionary position. After the moulting female’s new shell has hardened just enough for the male lobster to handle her, he mounts her from behind and uses his walking legs to rotate her body to face him. They fan each other with their swimmerets, and then after about fifteen minutes of this foreplay the male ejaculates his spermatophores into her seminal receptacle. This part of the act of mating takes about eight seconds. So not that different to some humans, really.

 
Jenny
137326.  Sun Jan 21, 2007 10:23 pm Reply with quote

The love drug released by the moulting female lobster can even give the male lobster the patience to withstand rejection. If he keeps his courtship up for long enough, he can often persuade the female to let him mount her. The reverse happens too. When the male isn’t interested, the female sometimes sidles up and tries to slip under him. This doesn’t usually succeed, but the love drug is strong enough to restrain him from violence.

Pouring water from a tank in which a female lobster has moulted is enough to encourage hard-shelled male and female lobsters to have sex rather than fight each other. However, if two male lobsters are put in the tank they become more antagonistic than ever. No gay lobsters have been observed.

The dominant males wait in their shelters, pissing out of the doorway at any females who come calling. The female approaches the male before she is ready to moult, and pisses back at him, her sex pheromones persuading him to cease his aggression and focus on the luuurve. He stands on tiptoe, fanning her urine around his home with his swimmerets, rather like lighting scented candles. The most dominant males are the most likely to be chosen – an evolutionary tactic that not only secures good genes for the offspring, but also secures good protection for the female during her time of vulnerability after shedding her shell. However, sadly for feminist lobsters, the way a male shows his dominance is to beat up and bully not only the other males but also the females.

The tactic of mating only when the female has moulted also confers evolutionary advantages on the male. The female’s previous hard shell acted like a chastity belt and would not have admitted any other male’s sperm, so he is assured that his sperm will fertilize her eggs. The male acts protectively towards the female until her shell hardens – about two weeks – and then they resume their previous antagonistic relationship.

In controlled environments, females time their moults sequentially, so that as one male-female pair splits up, another female is ready to move into the male’s hiding place and mate with him. It appears that the female’s PMS (pre-moult-syndrome) is timed by olfactory signals from the male-female pairs.

 
Jenny
137327.  Sun Jan 21, 2007 10:23 pm Reply with quote

As females age, they become more adept at mating and at making eggs, and unlike human females older and larger female lobsters produce more eggs than younger – around fifty thousand at a time. It used to be thought that because mating occurs during moulting and large females moult less often than small females, the less frequent spawning cancelled out the advantage of the extra eggs. However, later research showed that older females have larger seminal receptacles that effectively function as a sperm bank, so that from one mating an older female can produce and fertilize two batches of eggs without moulting or mating again, so they only need a mate once every four or five years in order to outbreed their younger rivals.

Lobster eggs develop for nine or ten months inside the female’s ovaries. Then she finds a secluded spot, lies on her back, folds her tail to create a pouch, and squirts the eggs out through a pair of ducts. At the same time, she opens her seminal receptacle, and fertilizes the eggs she has stored since mating. She attaches the eggs to the underside of her tail with adhesive from glands on her swimmerets, and carries them around for another ten months’ development before they hatch, when she releases them.

 
Jenny
137328.  Sun Jan 21, 2007 10:24 pm Reply with quote

Lobsters are ambidextrous as hatchlings, and their two claws are identical. During their first couple of years of life, they start to favour one or the other for crushing and the other for grasping and cutting. They develop two types of muscle fibres – fast fibres that contract rapidly but tire quickly, and slow fibres that contract more slowly but more strongly and for longer. As handedness develops, the seizing claw fills with fast muscle and the crushing claw with slow, and so it becomes bulkier.

When lobsters fight, they first shove each other with their claws and then grasp each other’s crushing claws and squeeze. After fifteen or twenty seconds, the weaker lobster will usually try and retreat, and the winner releases it. A losing lobster may be spared if it grovels enough, but might still be hacked to death.

If squeezing isn’t enough to settle the matter, the claws are used to attack the other’s antennae, legs, claws or eyes. A lobster gripped by another lobster can jettison its own limb by using a special muscle at its base. This is a protective mechanism, because lobsters’ blood flows through their body cavities rather than through veins, so a leak in their shells can cause it to bleed to death unless it is sealed off. Also, although lobsters are not usually cannibals, the scent of an injured lobster’s blood can drive other lobsters to kill and eat it. Fortunately, lobsters can regenerate legs, antennae and claws, though not eyes – although sometimes other appendages can appear in the eye’s place.


Last edited by Jenny on Sun Jan 21, 2007 10:29 pm; edited 1 time in total

 
Jenny
137329.  Sun Jan 21, 2007 10:24 pm Reply with quote

Lobsters prefer to be sheltered and somewhat dark, and they choose homes the way people choose jeans, but there are often dominance struggles in which one lobster will oust another from a particularly desirable hole. Young lobsters tend to choose tighter-fitting holes, and older lobsters choose a more relaxed fit, and will leave the younger lobsters alone unless they feel the neighbourhood is getting crowded, in which case they will unceremoniously turf the youngsters out. However, if a neighbourhood gets really crowded, the older lobsters will leave to seek out a less populated area and leave the young lobsters to fight over the small, crowded homes. Rather like New York City, in fact.


Last edited by Jenny on Sun Jan 21, 2007 10:30 pm; edited 1 time in total

 
Jenny
137330.  Sun Jan 21, 2007 10:24 pm Reply with quote

Lobster fishing has thrived in the Gulf of Maine in the last century or so, largely because of the overfishing of cod, the main predator of young lobsters in the past. Many laws govern lobstering in the State of Maine, home of the world’s largest lobster fishing industry. Fishermen and scientists have co-operated to preserve the stocks in recent years, by mandating minimum and maximum sizes of catch, and the preservation of egg-laying females. Lobsters take seven years to reach sexual maturity, so the size regulations preserve immature lobsters and protect the breeding stock. Breeding females have a notch cut out of their tail flippers, which makes them illegal to sell even if they are not carrying eggs when caught.

 
Jenny
137331.  Sun Jan 21, 2007 10:25 pm Reply with quote

Lobster meat is a healthy food, if it is served without melted butter. It is nearly fat free, and has fewer calories and less cholesterol than animal or poultry meat. It contains vitamins A, B12, and E, calcium, zinc and phosphorous, and is high in desirable omega-3 fatty acids, although it is relatively high in sodium. The lobster’s combined liver and pancreas, called the tomalley and easily recognized from its greenish colour, is not usually eaten, because it filters toxins so that lobster meat is not affected by other kind of shellfish blight and does not transmit diseases.

Dead lobster meat generates toxins quickly, and it is not safe to eat, but Animal welfare groups have long campaigned against the boiling of live lobsters. Although lobster nervous systems have been well studied, there is no clear answer to the question of whether lobsters feel pain. Lobsters have stress receptors but no identifiable pain receptors. They do not act pained at the loss of a limb or when wounds are inflicted. When a lobster is dropped into a steaming pot, its movements are no different to escape responses in any threatening situation. The nervous system does not seem to be more sophisticated than that of an insect.

When various methods of boiling lobster were tested, putting it straight into boiling water resulted in the shortest time of killing it. Chilling the lobster in the freezer first reduced the time of activity to no more than twenty seconds. For non-vegetarians, this is humane compared to the deaths of many other animals.

 

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