Crustaceans | Crustacea
Crustaceans are large group of anthropods that are typically free-living in freshwater or marine environments. However, there are some land-dwelling crustaceans, such as woodlice, and non-mobile creatures, such as barnacles. Crustaceans have a segmented body with three distinct parts: the head, thorax, and abdomen and symmetrical legs. They also usually have eyes on stalks, antennae, and an exoskeleton that they molt in order to grow. The fossil record of crustaceans dates back to 540 million years ago, during the Cambrian period, with some species of crustaceans appearing evolutionarily unchanged since the Jurassic period.
The diet of a crustacean depends on its size as well as species. Small terrestrial species typically eat matter from decaying organic matter. Parasitic crustaceans eat blood and skin materials from their host animal. Small aquatic crustaceans eat microscopic organisms, algae, and plankton while larger crustaceans eat snails, plants, and eggs of other marine life.
Crustaceans breath oxygen and use the same respiratory system as fish by breathing oxygen through their gills. Gills are very similar to lungs, but the difference is that gills pull the oxygen from water and not air as lungs do.
Some crustacean species live in freshwater, while most prefer salt water and live in the ocean. Most crustacean species tend to live close to the shore. Specifically, woodlice and crabs live on land while prawns and shrimp in open water.
