Anatomy: All crustaceans have bilaterally symmetrical bodies covered with a chitinous exoskeleton. The exoskeleton must be periodically molted when the animal undergoes metamorphosis Adult crustaceans have segmented bodies and jointed legs; head, thorax, abdomen The head bears two pairs of antennae, one median eye and two lateral eyes, and three pairs of biting mouthparts. Crustacean appendages have extensive adaptation for tasks such as swimming, sensory reception, and walking.
Reproductive: Both Sexual and asexual The sexes are normally, but not always, seperate in crustaceans Majority of the individual barnacles have both male and female reproductive organs. In some groups when males are present they are much smaller than the hermaphrodities. Those males are called "DWARL's" which they attach themselves to the interior of the mantle cavity of the large individuals and fertilize their eggs.
Nervous System: have a brain, or supraesophageal ganglion, connected to ta ventral nerve cord of ganglia, or nerve centres. Also, compound eyes which are very similar to those of flies and other insects. Median eyes are to found in crustaceans, particularyly in the nauplius larvae. Setae is also present in crustaceans. Some setae are tactile, detecting contact and movement when near. Other setae are used in association with statocysts. -Paired organs
Respiratory System: Gas exchange takes place through the entire thin integument. the inner wall of the carapace, facing the trunk, is often rich in blood vessels and may in many groups be the only respiratory organ. Gills when present are formed by modifications of parts of appendages, more than likely the epipodites. as an adaption to aerial respiration, the branchial chambers are greatly enlarged in cetain land crabs and serve as lungs.
Circulatory System: If they have no heart, their blood is being kept in motion by either a blood pump or rhythmic movements of the body, gut, or appendages. If a heart is present their, it lies in a sinus(pericardium), with which it communicates by paired valvular openings(ostia) The heart is a long tube the extends almost the entire length of the trunk
Digestive System: They have a gut which is usually direct in passage through the body. The foregut shows the greatest range and structure. The junction between the mill and the midgut is guarded by a filter of setae -allow a blockage until particules have been degraded into a sufficiently small size. The midgut also usually has one or more pouches(diverticula) which ar einvolved in various digestive processes.