Arthropods and Echinoderms Chapter 7

Review What Invertebrates have we learned about so far? Porifera – sponges Cnidaria – jellyfishes, sea anemones, coral Ctenophora – comb jellies Molluscs – snails, bivalves, octopuses, squid, cuttlefish

Objectives 1.Explain the basic characteristics of arthropods 2.Differences between copepods, barnacles, krill, and decapods 3.Explain the body structure of echinoderms

There are a lot of them! Largest phylum on earth 1,000,000 + species and several million undiscovered 3 out of every 4 animals on earth are arthropods The largest group are the __________? Insects!

Arthropod Characteristics Exoskeleton: – Tough, non-living external skeleton – Made of chitin – Protection, support, flexibility Segmented, bilaterally symmetrical body

Marine Arthropods Majority of marine arthropods are crustaceans Barnacles, shrimps, lobsters, crabs, and a variety of others

Crustaceans: Copepods Use mouth parts to capture food zooplankton Large antennae used to swim

Crustaceans: Barnacles Filter feeders Usually attached to surfaces (whales and crabs and rocks) Bodies enclosed by heavy plates Use cirri to sweep the water and feed

Crustaceans: Krill Most numerous animals on earth Exceed total human weight on the planet Major piece of the marine food chain

Crustaceans: Decapods (10 legs) Largest group of crustaceans (10,000 species) Includes shrimp, lobsters, crabs Largest crustaceans in size 14 lb Alaskan King Crab

Echinoderms Sea stars, sea urchins, sea cucumbers, and others Radially symmetrical – No head! Have an endoskeleton – Skeleton secreted within tissues (like ours) Water vascular system – Network of water filled canals

Tube Feet Tube feet are muscular extensions of water canals Used for attachment, locomotion, reception of chemical and mechanical stimuli, and eating.

Sea Urchins Round, rigid shell Movable spines Sucker-tipped tube feet – Breathe through these via gas exchange—no gills or lungs – Use to pass prey down back to mouth Mouth on bottom and anus on top

Sea Urchins Aristotle’s lantern – Jaws in the mouth – 5 teeth, self-sharpening – Able to dig holes in stones to use as hideaway Behavior can signal poor water quality – Lack of movement and drooping spines High intensity grazers – They love algae and kelp Sea Otters help protect kelp forests from destruction Sea Urchin Sex

Sand Dollar Adapted to live in sandy bottoms Deposit feeders Is this one dead or alive?

Sand Dollar Have tube feet Adapted to living in soft bottoms by having flattened bodies and short spines Has a less developed Aristotle’s Lantern – Feed on small particles – 5 doves Chews food for up to 15 minutes before swallowing – Takes up to two days to digest

Sunflower starfish 24 arms – Juveniles start with 5 Fast! 40 inches per minute 15,000 tube feet Up to 1m (39 in) across Can swallow an entire urchin, digest it, and expel its test (skeleton)

Video Footage of CA Coast