Lobster

Clawed lobsters comprise a family Nephropidae, sometimes also Homaridae of large marine crustaceans. Lobsters are economically important as seafood, forming the basis of a global industry that nets more than US 1 billion annually.

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.

The oldest known lobster fossil, Palinurus palaceosi, was discovered in Chiapas, Mexico in 1995. It has been dated at 110 million years old, 20 million years older than previously known specimens. 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.

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 two adapted to claws. 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 consists of 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 atop 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.