They resemble prawns in their external appearance but are somewhat larger in size as compared to them. Here we are talking about lobsters. Lobsters comprise a big family of marine crustaceans. They are very popular as sea food and the United States gets the profit of one million every year because of lobsters. Many species of crustaceans are designated with the tag of lobsters but the clawed lobsters are very popular ones. They are relished because of their flavour and texture. They resemble the spiny lobsters as well as the squat lobsters which lack claws. The closest relatives of the clawed lobsters are the reef lobsters and three families of fresh water crayfish. The fossil records suggest that they first appeared during the Cretaceous Period.
Lobsters belong to the phylum Arthropoda and are invertebrates with a well developed protective exoskeleton. They also moult several times in order to attain adulthood and at this time they are on the verge of being killed by the predators. At the time of moulting many species are known to change colour. They have 10 walking legs of which the first pair of legs is modified into claws. Like other arthropods they are also bilaterally symmetrical and often bear unequal and specialised claws like that of the king crab legs. The body is divided into two regions which are cephalothorax and abdomen. The head is fused with the thorax and therefore it is known as cephalothorax. It is covered by a chitinous covering known as carapace. The head is armed with a number of appendages. These appendages include antennae, antennules, mandibles, first and second maxillae and first, second and third maxillipeds. Lobsters prefer to dwell in a muddy environment and therefore they use their antennae as chemoreceptors. The eye bears a reflective structure just above the retina. The abdomen is provided with swimmerets which are composed of uropods and telson.
Their blood is blue coloured because of the presence of haemocyanin pigment which contains copper and the blood resembles that of snails and spiders. They bear a characteristic organ known as hepatopancreas which is green coloured and carries out the function of liver and pancreas. Hepatopancreas is known as tomalley by the chefs. They attain a length of 25-50 centimetres and are known to walk slowly on the seafloor. When disturbed they swim by curling and uncurling their abdomen. They walk at a speed of 5 metres per second. This is termed as caridoid escape reaction. Recent studies have shown that the lobsters do not show decline in fertility with advancing age. This longevity is mainly due to the presence of an enzyme known as telomerase which participates in the DNA repair mechanism in the form of a sequence TTAGGG. This sequence is often referred to as the telomere of DNA. Longevity also allows them to reach impressive sizes. According to the Guinness Book of World Records the largest lobster was caught in Canada and it weighed 20.15 kg.
They are found in marine environments from the shoreline to the continental shelf. They prefer to live singly either under the rocks or in the crevices. They are omnivorous and prey upon molluscs, worms, small crustaceans and some plant material. They are also known to exhibit cannibalism when kept in captivity and are known to eat the moulted skin after each moult. Lobsters are very much relished in soups. Their meat is also dipped in clarified butter and is a very popular delicacy in many parts of the globe. Cooks boil them in steam. They are also grilled and baked. They deserve a special place in literature and history.