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 http://www.earthlife.net/inverts/crustacea.html

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

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.

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

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 http://movingspaceproductions.com/view.php?video=Daz8nkh-pWM&feature=youtube_gdata_player&title=Molting+horseshoe+crab serc.si.edu

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