Bellwork: 11/19/2013 Many students seemed to mix up Porifera & Cnidaria Make sure to avoid that on the next unit since it includes: Echinoderms Bivalves Cephalopods Gastropods Mollusks Crustaceans

Echinoderms

Phylum Echindermata Share common features with chordates Radial Symmetry Usually slow moving or sessile Possess a thick calcium plate endoskeleton surrounded by a thin skin layer Possess a unique Water Vascular System, which continues throughout animal and extends into extensions called Tube Feet. - Functions for locomotion, feeding, & gas exchange.

Water vascular system A separate coelom is used with interconnecting fluid filled tubes and canals A ring canal circles the mouth and gives off 5 radial canals The radial canal is exposed and runs along the ambulacral groove Phylum Echinodermata

Water Vascular System Phylum Echinodermata

Tube Feet The ampullae is a small ball that sits above the tube foot Contraction and expansion of the ampulla accomplishes movement Phylum Echinodermata

Sea Stars Usually have 5 (or multiple of 5) arms radiating from central disk Tube feet located underneath each arm used for locomotion & grasping prey. Operate by hydraulic principles.

Echinoderms Skeleton Have an internal skeleton of calcium carbonate Ossicles vary in size and structure and are manufactured by specialized cells Phylum Echinodermata

Anatomy of a Sea Star B: Ambulacral Groove F: Arm E C A

Fig. 22.2b

Feeding Feed on mollusks by pulling shells apart and extending stomach outside the mouth into the bivalve. The bivalve is digested within it's shell. The sea star than re-ingests its stomach

Reproduction Can reproduce sexually by releasing sperm and egg. They are NOT hemaphrodites Can reproduce by regeneration

Regeneration Many species autotomize, leaving predators with a nutritious souvenir while they escape Most spp. can regenerate from fragments that include the disk Phylum Echinodermata

Sea Stars

Brittle Stars Distinct central disks with long tube-like arms Lack suckers Move by serpentine motion of their arms

Brittle Stars vs Sea Star Movement Sea Stars use their tube feet to crawl across the sea floor Brittle Stars use one of their legs as a lead and pull themselves across the sea floor Sea star locomotion Brittle Star Locomotion

Brittle Star

Sea urchins & sand dollars Lack arms, but possess tube feet Many species of urchins possess poisonous spines used for defense

Sand Dollar Sea Urchin

Sea Cucumbers Soft body with reduced structure Tentacles near mouth Respiratory tree

Sea Cucumbers Are elongated along oral-anal axis Lack spines and have reduced endoskeleton. Do possess tube feet and water vascular system Expels its insides as a defense mechanism

Sea Cucumber

Echinoderm Lab: Groups of 4 or less

Station #1 – Sand-Sifting Sea Star Flip the sea star onto its dorsal side & observe: Draw or describe how the sea star flips itself back over. What sensory cells are involved in keeping the sea star upright? Place the sea star upside down the dissection microscope.

Station #1 – Sand-Sifting Sea Star 3) Observe, sketch, and label the following regions: center of the sea star, middle of an arm, terminal end of the arm. Label if present in each sketch: Mouth Tube feet Abulacral groove Spines Sensory Tentacles

Station #2 – Tube Feet Prepared Slide Observe & sketch the prepared slide on both the low & medium objectives. Describe the shape/texture of the ectoderm on the tube feet. Why are the tube feet hollow? What is the name of the tissue that the tube feet are connected to? Why does this tissue appear to have empty pockets. Aside from locomotion & feeding, what other job do tube feet perform? What feature of the tube feet allows this to be possible?

Station #3 – Amputated Arm & Cross-section Examine the cross-section under the dissection microscope. Sketch the cross-section Label the following: Digestive gland/pore Ambulacral groove Tube feet Ampulla Water vascular pore

Station #4 – Brittle/Serpent Sea Star Remove the brittle star/serpent sea star from the container & place it on the table. How does it move? How does a sea star move in comparison? What are the advantages & disadvantages of both types of movement? Observe & sketch the central disk of the brittle/serpent sea star.

Station #4 – Brittle/Serpent Sea Star 3. Observe & sketch the amputated brittle sea star leg under the dissection microscope & the cross-section under the standard microscope. How is this arm different than the arms of a standard sea star?

Station #5 – Sea Urchin Using your finger, gently poke one of the spines on the sea urchin. What is its response? What receptors are involved in this detection? Using the urchin with shorter spines, gently flip the urchin over. How does it flip itself over? Is this a faster or slower process than with the sea star? Why do sea urchins have tube feet that are much longer than those found on any other echinoderm?

Station #5 – Sea Urchin Observe the long-spined urchin. What are the white spots on the dorsal portion of the animal? What is the green (orange?, red?, sorry…I’m not sure what color it is) anatomical feature found in the very center of the dorsal side?

Station #6 – Sea Cucumber Observe & sketch the sea cucumber under the dissection microscope. Label the tube feet, respiratory tree, and tentacles. Describe the texture of this animal in comparison to the other echinoderms. While considering the relatively low number of tube feet found on this organism in comparison to other echinoderms, what functions would the sea cucumber lack & what additional anatomical feature(s) can be found to address these deficiencies?