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American lobster, Homarus americanus
American lobster, Homarus americanus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Infraorder: Astacidea
Family: Nephropidae
Dana, 1852
Genera [1]

Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans.

Though several groups of crustaceans are known as "lobsters," the clawed lobsters are most often associated with the name. They are also revered for their flavor and texture. 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 lobsters and the three families of freshwater crayfish.

The fossil record of clawed lobsters extends back at least to the Valanginian Age of the Cretaceous.[2]

EvolutionEdit

Lobsters were more diverse in the Cretaceous period (53 species) than in the Tertiary (16 or 18 species), which has been postulated to have been caused by mass extinction at the K–T boundary. However, diversity rebounded in the Eocene, and it may be that the lower Tertiary diversity was mainly due to lobsters abandoning shelf depths in the late Eocene/early Oligocene, as fossils of deep-dwelling lobsters are rare. It is nevertheless clear that shelf-dwelling lobsters were more diverse during the Cretaceous.[3]

Description Edit

"Lobster claw" redirects here. For the species of flowering plants, see Lobster-claw.
File:Homar1.jpg

Lobsters are invertebrates, with a hard protective exoskeleton. Like most arthropods, lobsters must molt in order to grow, which leaves them vulnerable. During the molting process, several species change color. Lobsters have 10 walking legs; the front three pairs bear claws, the first of which are larger than the others.[4] Although, like most other arthropods, lobsters are largely bilaterally symmetrical, they often possess unequal, specialized claws, like the king crab.

Lobster anatomy includes the cephalothorax which fuses the head and the thorax, both of which are covered by the chitinous carapace and the abdomen. The lobster's head bears antennae, antennules, mandibles, the first and second maxillae, and the first, second, and third maxillipeds. Because lobsters live in a murky environment at the bottom of the ocean, they mostly use their antennae as sensors. The lobster eye has a reflective structure above a convex retina. In contrast, most complex eyes use refractive ray concentrators (lenses) and a concave retina.[5] The abdomen includes swimmerets and its tail is composed of uropods and the telson.

Lobsters, like snails and spiders, have blue blood due to the presence of haemocyanin, which contains copper.[6] (In contrast, mammals and many other animals have red blood from iron-rich haemoglobin.) Lobsters possess a green hepatopancreas, called the tomalley by chefs, which functions as the animal's liver and pancreas.[7]

In general, lobsters are Template:Convert/-Template:Convert/test/A long and move by slowly walking on the sea floor. However, when they flee, they swim backwards quickly by curling and uncurling their abdomen. A speed of Template:Convert/m/sTemplate:Convert/test/A has been recorded.[8] This is known as the caridoid escape reaction.

Navigation Edit

It is thought that lobsters may use magnetic orientation to navigate

EcologyEdit

Lobsters are found in all oceans. They live on rocky, sandy, or muddy bottoms from the shoreline to beyond the edge of the continental shelf. They generally live singly in crevices or in burrows under rocks.

Lobsters are omnivores, and typically eat live prey such as fish, mollusks, other crustaceans, worms, and some plant life. They scavenge if necessary, and may resort to cannibalism in captivity; however, this has not been observed in the wild. Although lobster skin has been found in lobster stomachs, this is because lobsters eat their shed skin after molting.[9]

SpeciesEdit

File:Metanephrops japonicus edit.jpg
File:Nephropsis rosea.jpg

This list contains all extant species in the family Nephropidae:[3]

References Edit

  1. Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong et al. (2009). A classification of living and fossil genera of decapod crustaceans. Raffles Bulletin of Zoology Suppl. 21: 1–109.
  2. Dale Tshudy, W. Steven Donaldson, Christopher Collom, Rodney M. Feldmann & Carrie E. Schweitzer (2005). Hoploparia albertaensis, a new species of clawed lobster (Nephropidae) from the Late Coniacean, shallow-marine Bad Heart Formation of northwestern Alberta, Canada. Journal of Paleontology 79 (5): 961–968.
  3. 3.0 3.1 Dale Tshudy (2003). Clawed lobster (Nephropidae) diversity through time. Journal of Crustacean Biology 23: 178–186.
  4. Carlos Robles (2007). "Lobsters" Mark W. Denny & Steven Dean Gaines Encyclopedia of tidepools and rocky shores, 333–335, University of California Press.
  5. M. F. Land (1976). Superposition images are formed by reflection in the eyes of some oceanic decapod Crustacea. Nature 263: 764–765.
  6. Copper for life - Vital copper. Association for Science Education.
  7. Shona Mcsheehy & Zoltán Mester (2004). Arsenic speciation in marine certified reference materials. Journal of Analytical Atomic Spectrometry 19: 373–380.
  8. The American lobster — frequently asked questions. St. Lawrence Observatory, Fisheries and Oceans Canada.
  9. Homarus americanus, Atlantic lobster. MarineBio.org. URL accessed on December 27, 2006.

External links Edit

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Wikimedia Commons has media related to:
[[Commons: Category:Nephropidae

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