Phylum Arthropoda

“jointed feet”

Basic Info• Largest of all Phyla

• Include:– Insects– Arachnids– Crustaceans

Characteristics

• Segmented Body with Appendages on each segment

• Dorsal heart and ventral nervous system

• Covered by a hard exoskeleton– Less prone to

dehydration– Made of chitin– Molts periodically

due to growthMolting of a black crab

Common CrustaceansTrue Crabs• Five visible pairs of legs• Abdomen folded under

cephalothorax

7-11 crab, found wedged in rocks

A’ama, black crab

Box crabs

Female Male

Hermit Crabs• Salvage empty

shells for homes• Protect soft

abdomens

Some hermit crabs work cooperatively with other organisms (sea anemones attached above)

Common Hawaii tidepool hermit crab

Lobsters• Abdomen with

swimmerets

Spiny lobster

Slipper lobsterHawaiian lobster

Barnacles• “curl footed”, to capture

food• Larvae cements its head

down• Grow armor plates to

protect body

Symbiosis with Arthropods

Working together, pom pom crab and sea anemones, teddy bear crab with anemones, cleaner shrimp with eel

Best of friends, goby and the blind shrimp. Shrimp digs the hole, and the goby becomes the shrimps “eyes” for defense and gets leftover food.

Sponge crab uses sponge for self defense and sponge gets to move to new food.