The Sea Flea (Nerocilia bivittata) belongs to the arthropod Philum, the crustacean Subphilum, the Malacostracei class and the order of the isopods.
The segmented body is covered by a hard-to-protect exoskeleton. The dimensions can range from 2-3 mm up to 2 centimeters in length.
As all crustaceans will change the armour many times in life during the period of accretion replacing with a new one that then hardens.
The order of the isopods, among the crustaceans, is one of the few orders with species without carapaces and claws.
The sea flea can find it starting from the surface up to fifteen meters deep and as soon as it has opportunity becomes fang of fish with which it meets.