Malacostraca
Malacostraca is a large and diverse class of crustaceans, comprising over 40,000 species. They are found in nearly all aquatic habitats, including freshwater, marine, and terrestrial environments. This class is characterized by a segmented body with a distinct head, thorax, and abdomen, and a well-developed exoskeleton. Malacostracans include many familiar crustaceans such as crabs, lobsters, shrimps, and krill.
Common Names
Malacostracans are commonly known by their specific group names, such as crabs, lobsters, shrimps, crayfish, and krill. However, the term malacostracan itself is not widely used in everyday language.
Characteristics
Malacostracans share several key characteristics:
- Segmented body: Their body is divided into three distinct regions: head, thorax, and abdomen.
- Exoskeleton: They have a hard, external skeleton made of chitin, which provides protection and support.
- Appendages: They have a pair of antennae on their head, and various other appendages on their thorax and abdomen, adapted for locomotion, feeding, and sensory functions.
- Gills: Most malacostracans have gills, which are specialized organs used for breathing underwater.
- Molting: Like other crustaceans, they shed their exoskeletons periodically to grow.
Environments
Malacostracans have adapted to a wide range of aquatic environments, including:
- Marine: The majority of malacostracans are found in marine environments, from shallow coastal waters to deep ocean trenches.
- Freshwater: Some species are found in freshwater lakes, rivers, and streams.
- Terrestrial: A few species, like the land crabs, have adapted to live on land, but still require access to water for reproduction.
References
For more information on Malacostraca, please refer to these reliable sources: