Lobster
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![]() American lobster, Homarus americanus
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Lobsters are large crustaceans that live in the sea. The form the family of Nephorpidae, which is sometimes also called Homaridae. Lobsters are an economically important type of seafood.
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[edit] Biology
Several different groups of crustaceans are known as lobsters. When people talk about lobsters, they mean cawed lobsters most of the time, such as the genus Homarus. Clawed lobsters are not closely related to spiny lobsters or slipper lobsters, which have no claws (chelae), or squat lobsters. The closest relatives of clawed lobsters are the reef lobster Enoplometopus and the three families of freshwater crayfish.
Smaller varieties are sometimes called "lobsterettes". Lobsters are invertebrates, and have a tough exoskeleton, which protects them. Like most arthropods, lobsters must shed it in order to grow.This is called molting. It leaves them vulnerable during this time. During the molting process, several species may experience a change in color.
Lobsters live on rocky, sandy, or muddy bottoms from the shoreline to beyond the edge of the continental shelf. They generally live alone in crevices or in burrows under rocks.
Lobsters typically eat live food, consisting of fish, mollusks, other crustaceans, worms, and some plant life. Occasionally, they will scavenge if necessary, and may resort to cannibalism in captivity; however, this has not been observed in the wild. Lobster skin in the stomachs of lobsters has been found before, although this is because lobsters will eat their shed skin after molting [1]. Lobsters grow throughout their lives and it is not unusual for a lobster to live for more than 100 years [2]. They can thus reach impressive sizes. According to the Guinness World Records, the largest lobster was caught in Nova Scotia, Canada and weighed 20.14 kg (44.4 lb).
Being arthropods, lobsters are largely bilaterally symmetrical; clawed lobsters often possess unequal, specialized claws, like the king crab. A freshly caught lobster will have a claw that is full and fleshy, not atrophied. The anatomy of the lobster includes the cephalothorax which is the head fused with the thorax, both of which are covered by the carapace, of chitinous composition, and the abdomen. The lobster's head consists of antennae, antennules, mandibles, the first and second maxillae, and the first, second, and third maxillipeds. Because a lobster lives in a murky environment at the bottom of the ocean, its vision is poor and it mostly uses its antennae as sensors. Studies have shown that the lobster eye is formed with a reflective structure atop a convex retina. In contrast, most complex eyes use refractive ray concentrators (lenses) and a concave retina [3]. The abdomen of the lobster includes swimmerets and its tail is composed of uropods and the telson.
In general, lobsters move slowly by walking on the bottom of the sea floor. However, when they are in danger and need to flee, they swim backwards quickly by curling and uncurling their abdomen. A speed of 5 meters per second has been recorded.
[edit] Symbion
In December 1995, the parasitic Symbion pandora, the only member of its phylum, was discovered attached to the feeding appendages of a Norway lobster. Since then, at least two other species of Symbion have been discovered, on the American lobster (Homarus americanus) and the European lobster (Homarus gammarus).
[edit] References
- ↑ Homarus americanus, Atlantic lobster. Retrieved on December 27, 2006.
- ↑ David Foster Wallace (2005). Consider the Lobster and Other Essays, Little, Brown & Company. ISBN 0-31-615611-6.
- ↑ Land, M. F. (1976). Superposition images are formed by reflection in the eyes of some oceanic decapod Crustacea. Nature 263: 764-765.
[edit] External links
- Lipke Holthuis. Marine Lobsters of the World. Food and Agriculture Organization.
- Lobster Liberation