Echinodermsare radiallysymmetrical animals that are only discovered in the sea (there are noneon land also or in fresh water). Echinoderms expect "spiny skin" in Greek.Many kind of, yet not all, echinoderms have spiny skin. There are over 6,000 species.Echinoderms normally have actually 5 appenderas (arms or rays), but there are someexceptions.

Radialsymmeattempt implies that the body is a hub, like a bicycle wheel, and tentacles arespokes coming out of it (think of a starfish). As larvae, echinoderms arebilaterally symmetrical. As they mature, they become radially symmetrical. Mostadult echinoderms live on the bottom of the ocean floor. Many kind of echinoderms havesuckers on the ends of their feet that are used to capture and organize prey, andto hold onto rocks in a swift current.

HowDo Sea Stars Move?Each sea star hadthousands of tiny feet on the bottom of each ray. These are tube feet, orpodia. These tiny feet can be filled through sea water. The vascular system of thesea star is likewise filled with sea water. By moving water from the vasculardevice into the tiny feet, the sea star have the right to make a foot move by broadening it.This is just how sea stars relocate about. Muscles within the feet are provided to retractthem. Each ray of a sea star has a light sensitive organ called an eyespot.Though it have the right to not check out virtually and we perform, sea stars have the right to detect light andits basic direction. They have actually some concept of wbelow they are going.

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Procedure (Abdental Surface):

Obtaina preserved starfish and rinse off any type of preservative via water.

Placethe starfish in the dissecting pan through its dorsal or aboral(top) surconfront upward.

Observethe starfish and also determineits symmeattempt.

Locatethe centraldisc in the center of the starfish. Count and record the number oranches or rays the starfish has actually.

Locatethe little, round difficult plate referred to as the madreporite on optimal of themain disc. Water enters with this right into the water vascular device. Labelthe centraldisc, arms, and madreporite on Figure 1.

Feelthe upper surconfront of the starfish for spines. These spines safeguard the starfishand are part of their interior skeleton. Label these on number 1.

Lookat the reminder of each arm and find the eyespot. Label this on Figure1.

Figure 1 -Aboral Surface


Procedure (Oral Surface):

7.Turn the starfish over to its ventral or oralsurface (underside).

8.Locate the mouth in the facility of themain disc. Find the ring of dental spines surrounding themouth. Label these on figure 2.

9.Find the groove that exoften tends dvery own the underside of each arm. Thisis dubbed the ambulacralgroove. Label this on figure 2.

10.Feel the countless, soft tube feet inside each groove.These are part of the water vascular system &assist in activity and also feeding. Label these on Figure 2.

Figure 2 - Oral Surface


Procedure (Internalanatomy):

With the starfish"s abdental surface dealing with you, cut off the reminder of a ray. Cut alengthy lines a, b, and c (Figure 3) and then remove this flap of skin.

Figure 3 - Cuts in Arm


Inside each arm, situate 2 lengthy digestive glands dubbed the pyloric caeca. These make enzymes to digest food in the stomach. Label these in Figure 4. Cut a circular flap of skin from the central disc. (You will certainly have to also reduced around the madreporite in order to rerelocate this flap.) Observe the stomach under the central disc. Label this on Figure 4. Remove the pyloric caeca from the dissected ray. Find the gonads (testes or ovaries) underneath. These may be little if the starfish is NOT in breeding seakid. Label these on figure 4. Rerelocate these to see the rest of the water vascular system. Cut off the tip of a ray to observe the parts of the tube feet. Find the zipper-like ridge that exhas a tendency the length of the ray. The tube feet are attached to these. Locate the bulb-choose optimal of a tube foot dubbed the ampulla. This sac works prefer the optimal of an eyedropper to create suction. The bottom of the tube foot is a sucker. Label these in Figure 4. Embedded in the soft body wall are skeletal plates referred to as ossicles. Locate these and label them in Figure 4.

Figure 4 - Starfish Digestive &Reabundant Systems


Running down the center of each arm is a lateral canal to which tube feet are attached. Label this in Figure 5. In the main disc the five lateral canals attach to a circular canal dubbed the ring canal. Find this canal & label it on figure 5. A brief, canal referred to as the rock canal leads from the ring canal to the madreporite wright here water enters. Find this canal & label the stone canal & madreporite on Figure 5. Draw an arrowhead on Figure 5 tracing the course that water takes as soon as it enters & moves via the starfish.

Figure 5 - Water Vascular System



1. What form ofsymmeattempt did your starfish have?

2. What is the top surfaceof the starfish called?

3. What is the lowersurchallenge of the starfish called?

4. On which surconfront are these components of a starfish visible:

a.Mouth -

b.Madreporite -

c.Suckers -

d.Oral spines -

e. Eyespots -

d. Ambulcaral groove -

5. In words, map thepath water takes via the water vascular system.



6. What part of thetube foot creates suction to open up clams whenever before the starfish feeds?

7. Why carry out the gonadsperiodically appear larger?

8. What kind ofskeleton, endoskeleton or exoskeleton, does the starfish have?

9. What bony platesmake up its skeleton?


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What is theattribute of the pyloric caeca?

11. whereis the stomach of a starfish located? What can the starfish carry out via its stomachonce feeding on clams & oysters?