There are numerous pairs of forked appendages, which are modified for different functions.
Crustaceans are predominantly aquatic, breathing by means of gills.
A few, such as the fish louse , are parasitic on fish, whales, and other aquatic animals. During reproduction the male transfers sperm to the female, which often carries the fertilized eggs until they hatch. The Macmillan Encyclopedia 2001 2. The Macmillan Encyclopedia 2001 4. The Macmillan Encyclopedia 2001 5.