Phylum Arthropoda jointed foot

1. Phylum Arthropoda�jointed foot� Things that creep around on the ocean bottom (some don�t really creep!); also crustaceans and other stuff

2. General Characteristics The largest phylum of animals on earth � three out of four animals on earth are arthropods Include marine barnacles, shrimp and lobsters as well as all insects Have a segmented body Bilateral symmetry Jointed appendages Hard exoskeleton made of chiton Tough and non-living Covers all parts of the animal Shed when the animal grows � called molting Limits size of the animal because it becomes too heavy in large animal to allow movement

3. Feeding and Digestion Because of the mandibles and specialized legs, arthropods have the ability to eat almost anything Fill all niches of ecology � carnivores, filter feeders, herbivores and parasites Many marine species use their mouthparts or legs to filter the water Parasitic crustaceans have their appendages specialized for sticking onto another organism The mouth of these organism have the first real teeth like structures made of chiton They have a two chambered stomach connected to digestive glands which release enzymes to aide in digestion Digestion is extracellular and waste is sent out through the anus

4. Respiration Arthropods use gills that resemble feathers located just under their exoskeleton Movement of the mouthparts keeps water moving in a steady stream over the gills Land crabs also have gills for respiration � the gills are kept wet with body fluids and air is passed over the moistened gills for oxygen absorption

5. Behavior and Response Crustacean have a small and simple brain Most members of this phylum have well defined sense organs Compound eyes � a bundle of light sensitive units grouped together at the end of a stalk like antennae Sense of smell � very sensitive to chemicals in water Very complex communication is possible between members through movement Used for courtship and territory protection

6. Reproduction Separate male and female individuals Internal fertilization occurs Females can store sperm for long periods of time before they use it to fertilize their eggs Females tend to carry the eggs until they hatch The young are larvae that are plankton-like and very rarely resemble the adults

7. Class Trilobites Oldest class from which the rest of the phylum evolved Lived in all the ancient seas. Is now the most common fossil. Distinguishes the areas that were occupied by the organism All members of this class are now extinct

8. Class Crustaceans Specialized for life in the ocean � all members have gills for respiration and appendages specialized for swimming Over 35,000 species exist Generally characterized by a hard exoskeleton, two pairs of antennae and mouth parts called mandibles Have two pair of antennae that are specialize for sensing the environment The mandibles are generally short, heavy and specialized for feeding Vary in size between microscopic plankton to large lobsters Main body plan is a head, thorax (area behind the head) and abdomen (the tail end of the animal)

9. Class Crustaceans Barnacles are part of this class even though they look like mollusks The legs that stick out of the volcano shaped exoskeleton capture plankton to eat Shrimp, lobsters and crabs belong to a group called decapods have 10 legs Prized for food Two pairs of the legs are often specialized into claws for feeding purposes Tend to be scavengers

11. Other Arthropods Horseshoe crabs � still the same after thousands of years and called living fossils Sea Spiders � resemble land spiders, most common in cold waters and huge Insects � have only three pairs of legs as adults, not aquatic but worth mentioning Largest and most diverse on earth Can live at the sea�s edge scavenging on seaweed and barnacles