1. Phylum Arthropoda, Subphylum Crustacea
The majority of marine arthropods are crustaceans (subphylum Crustacea)
Crustaceans are distinguished from other Arthropods by their possession of a pair of biramous (two-parted) limbs, and by a nauplius larval stage
Includes barnacles, shrimp, krill, crabs, lobsters, and copepods
Looks like 2 limbs stuck together; including 2 antennae

3. Phylum Arthropoda, Subphylum Crustacea
Crustaceans are specialized for life in the water
Most possess gills to obtain oxygen
Chitinous exoskeleton reinforced with CaCO3
Two pairs of antennae

4. Barnacles are crustaceans!
Free-living barnacles are attached to the substratum by cement glands that form from the base of the first pair of antennae; in effect, the animal is fixed upside down by means of its forehead. Inside the carapace, the animal lies on its back, with its limbs projecting upwards.

5. The wonderful world of crustaceans!
Amphipods have a curved body that is flattened sideways
Isopods are dorsoventrally flattened
Shrimps, lobsters and crabs are decapods; all have ten legs made up of 5 pairs of appendages 1
2-5

6. Molting Arthropods must molt, or shed, their exoskeleton as they grow
Most arthropods are small because the rigid exoskeleton puts limitations on their size
Softshell crab, ecdysis
afcd.gov.hk
serc.si.edu
serc.si.edu

8. Other Marine Arthropods
Other than crustaceans, there are relatively few marine Arthropods
Horseshoe crabs are not crustaceans, and belong to subphylum Chelicerata
Largely extinct; only five living species
Horseshoe-shaped carapace* that encloses a body with six pairs of legs
*shield-like structure that covers anterior portion of Arthropods
“Thigh mouth”, appendages that are mouth at one end, and locomotion/swimming appendages at other
Include extinct sea scorpions