Pedia News


Crustaceans are members of the phylum Arthropoda, which includes their terrestrial relatives the insects and spiders. Crabs, lobsters, and shrimp are all members of the crustacean subphylum.

Arthropods are invertebrate animals with a particular set of shared characteristics inherited from their common ancestor. These creatures have bilateral symmetry, segmented bodies, 6 or more jointed limbs, and most often a hard, chitinous external covering called an exoskeleton that is replaced during molts throughout the creature’s life.
This hard exoskeleton is limiting, and in order to grow, all arthropods need to shed a current skeleton in favor of a new and larger one. The stiff exoskeleton is supported by movable jointed legs, and different functions, such as the rear walking legs and forward grabbing and crushing claws of crabs.

Although we mostly associate them with the Chesapeake Bay, blue crabs range all along the Atlantic coast from Canada to Argentina. Blue crabs live in a wide variety of habitats throughout their lives. These crabs have a high tolerance for changes in both water temperature and salinity, so they can survive almost anywhere in the bay.
Crabs are meat-eaters that feed by predation and scavenging. If you can find it on the ocean floor, they eat it, including fish, clams, oysters, mussels, snails, worms, insects, and even each other.
Habitat loss and increased nutrient loading have been the greatest threats to blue crabs. Reducing nutrient runoff from suburban lawns, farms, and other areas and maintaining healthy stream and river sheds, as well as healthy seagrass beds, have been important for a healthy Chesapeake Bay and recovering blue crab populations there.
Compared with the blue crab, the American lobster comes from colder, deeper water areas but is just as prized as a source of food. Lobsters are also in the arthropod order Decapoda, which includes about 10,000 species of shrimp, crabs, crayfish, and lobsters.
The chitinous exoskeleton of these creatures is typically dark and turns red when the creatures are boiled for dinner. Lobsters are omnivores and eat fish, bivalves, and other crustaceans as well as some plant life and even their own molted shells.
As adults, male lobsters will molt about once each year, and females will molt once every 2 years. Lobsters can only grow through these moltings. Sometimes they eat their own hard shells after molting, which replaces body calcium and helps the soft shell harden. With each molt, a lobster can gain 15% in length and 40% in weight.
Lobsters are so important to the stable ecological processes of the oceans because they scavenge all types of dead animals and their parts. They are also efficient predators that are active at night. Their biology is still poorly known, so zoologists continue to focus their studies on lobster ecology and reproduction.