Phylum Arthropoda - Class Crustacea
There are about 42,000 species of Crustacea, including many of the most familiar arthropods such as the crabs and the lobsters. Crustacea is the only group of arthropods that is primarily marine, though there are many fresh water species also. There are some semi-terrestrial species, but these are not, in general, well adapted for life on land, in contrast with other members of the phylum Arthropoda, most notably insects, which have been very successful on land.
Crustaceans are :
- only group of arthropods that is primarily marine
- primitive
- highly segmented animals, each segment bearing a pair of limbs
- head
- five pairs of appendages
- two pairs of antennae
- a pair of mandibles
- two pairs of maxillae
- thorax
- series of limb bearing segments
- may have become fused with the head
- abdomen
- may or may not have appendages
- appendages
- typically biramous, that is having two branches, but may become secondarily uniramous
- calcified cuticle
Some major subclasses of Crustaceans
- Subclass: Branchiopoda--fairy shrimp, brine shrimp
- Subclass: Copepoda--copepods
- Subclass: Cirripedia--barnacles
- Subclass: Malacostaca
- Order: Stomatopoda--mantis shrimp
Order: Euphausiacea--krill
Order: Decapoda--shrimps, lobsters, crabs