Lobster

Lobsters are a type of decapod crustacean classified under the family Nephropidae (also called Homaridae). They have elongated bodies and strong, muscular tails, and they typically inhabit crevices or burrows on the ocean floor. Of their five pairs of legs, three have claws, with the front pair being noticeably larger than the rest. Highly valued as seafood, lobsters are a major economic resource, often ranking among the most profitable catches in the coastal regions where they are found.

Key commercial species include two species from the genus *Homarus* in the northern Atlantic Ocean, the smaller *Nephrops norvegicus* (known as true scampi, Norway lobster, or langoustine), and several smaller species in the genus *Metanephrops*, commonly called Pacific scampi.

**Distinction**

While other crustacean groups include "lobster" in their names, the term by itself usually refers to the clawed lobsters of Nephropidae. These clawed lobsters are not closely related to spiny or slipper lobsters (which lack claws) or to squat lobsters. Their closest living relatives are reef lobsters and three families of freshwater crayfish. In the United States, only the *Homarus* species—*H. gammarus* (European lobster) and *H. americanus* (American lobster)—can be sold simply as "lobster" without qualification. In cooking, "lobster" in North America almost always means the American lobster, while in Great Britain it refers to the European lobster. Other species, whether clawed (like the Norway lobster) or not (like the spiny lobster), require qualified names. In the Caribbean, *Panulirus argus* is formally called the spiny lobster but is often just called "lobster" informally. In other English-speaking regions, the unqualified term is rarely used.

**Description**

**Body**

Lobsters are invertebrates with a hard exoskeleton that they must shed to grow, a process that leaves them vulnerable. During molting, several species change color. They have eight walking legs, with the front three pairs bearing claws, the first of which are larger. These front pincers are considered legs, placing lobsters in the order Decapoda ("ten-footed"). Though mostly bilaterally symmetrical, some genera have unequal, specialized claws. The body has two main parts: the cephalothorax (fused head and thorax, covered by a chitinous carapace) and the abdomen. The head has antennae, antennules, mandibles, two pairs of maxillae, and usually stalked compound eyes. Because lobsters live in murky seafloor environments, they rely mainly on their antennae as sensors. Their eyes have a reflective structure above a convex retina, unlike most complex eyes that use lenses and a concave retina. The thorax contains maxillipeds (mouthparts) and pereiopods (used for walking and gathering food). The abdomen has pleopods (swimmerets) for swimming and a tail fan made of uropods and the telson. Lobsters have blue blood due to copper-containing hemocyanin, unlike the red, iron-rich blood of vertebrates. They also have a green hepatopancreas (called tomalley in cooking) that functions as both liver and pancreas. Nephropidae lobsters resemble other related groups but differ from freshwater crayfish by lacking a joint between the last two thorax segments, and from reef lobsters (Enoplometopidae) by having full claws on the first three leg pairs. Distinctions from fossil families like Chilenophoberidae are based on carapace groove patterns. Analysis of their neural genes shows an extraordinary development of chemosensory machinery, including a wide diversification of ligand-gated ion channels and secretory molecules.

**Longevity**

In the wild, lobsters may live 45 to 50 years, though age is hard to determine and is usually estimated from size. Newer techniques may improve accuracy. Research suggests lobsters do not slow down, weaken, or lose fertility with age; older lobsters may even be more fertile. This longevity may be linked to telomerase, an enzyme that repairs DNA telomeres. Unlike most vertebrates, which express telomerase only during embryonic stages, lobsters produce it as adults in most tissues. However, longevity is limited by size: molting requires energy, and larger lobsters need more. About 10 to 15% die from exhaustion during molting, and in older lobsters, molting stops, leading to exoskeleton degradation or collapse and death. Lobsters grow throughout life, adding new muscle cells at each molt, which allows them to reach impressive sizes. The largest lobster ever caught, according to Guinness World Records, weighed 20.15 kilograms (44.4 lb) and was found in Nova Scotia, Canada.

**Ecology**

Lobsters are found in all oceans, on rocky, sandy, or muddy bottoms from the shoreline to beyond the continental shelf edge, depending largely on their size and age. Smaller, younger lobsters are typically found in shallower, more sheltered areas.