Question

Match the description of the endoskeleton with the correct echinoderm class.

5 Gently cut the tissue away from the central disk to find the internal structures featured in Figure 31.8. Record your observations and labeled sketch in the space provided. 6 Thoroughly clean your laboratory station and equipment. Return the dry equipment, and discard the sea star as indicated by the instructor Sea star Check Your Understanding 1.1 Variability is seen in the endoskeleton of the different echinoderm classes. Match the description of the endoskeleton with the correct echinoderm class. Asteroidea A. "Test" formed of tightly fused skeletal plates Echinoidea B. Latticework of ossicles: flexible to facilitate movement C. Endoskeleton reduced to isolated ossicles embedded in a muscular body Ophuiroidea D. Stalk of ring-shaped ossicles and branches or cirri Crinoidea E. Flexible arms; appears jointed due to conspicuous plates on outer surface Holothuroidea 1.2 Comparing the location of the madreporite of some echinoderms, the . (Circle the correct answer.) a. madreporite in the sea star is located on the aboral surface on one side of the central disk b. madreporite in the brittle star is located on the oral surface c. madreporite in the sea urchin is located on the aboral surface in the center of the test d. both a and c e. all of the above 1.3 What is the function of the madreporite and the water vascular system? 1.4 What is unique about the respiratory tree in sea cucumbers? 1.5 Echinoderms vary in their anatomy, and differences are seen as the presence or absence of arms. Match the description with the correct echinoderm class. Asteroidea A. Five arms composed of feathery branches or pinnules Echinoidea B. Five arms radiating from a central disk C. No arms present; fused ossicles make up a test Ophuiroidea D. No arms present; tentacles surrounding a mouth Crinoidea E. Five slender arms sharply set off from the central disk Holothuroidea 620 Exploring Biology in the Laboratory

Answer 1

1.1)

A)Echinoidea- Test form of tightly fused skeleton plate

B) Asteroidea- Latticework of ossicles flexible to facilitate movement.

C)Holothuroidea- Endoskeleton reduced to isolated ossicles embedded in a muscular body.

D)Crinoidea- stalk of ring shaped ossicle and branches of cirri.

E)Ophuiroidea - flexible arms, appears jointed due to conspicuous plates on outer surface.

1.2) e. All of the above are correct.

Explaination- The madreporite is located on the aboral (top) surface in sea stars, sand dollars, and sea urchins, but in brittle stars, the madreporite is on the oral (bottom) surface. Sea cucumbers have a madreporite, but it's located inside the body.Madreporite or sieve plate: a small, smooth plate, at the entrance of the sea star's water vascular system, through which the sea star takes in sea water. It's located on the aboral side of the sea star, slightly off the center.

1.3)The madreporite is an essential part of the circulation system in echinoderms. Through this plate, which is also called a sieve plate, the echinoderm draws in seawater and expels water to fuel its vascular system. The madreporite functions like a trap door through which water can move in and out in a controlled manner.The madreporite is a lightcolored calcareous opening used to filter water into the water vascular system of echinoderms. It acts like a pressure-equalizing valve. It is visible as a small red or yellow button-like structure, looking like a small wart, on the aboral surface of the central disk of a sea star or sea urchin. Close up, it is visibly structured, resembling a "madrepore" (stone coral, Scleractinia) colony. From this, it derives its name.

The water vascular system of the sea star consists of a series of seawater-filled ducts that function in locomotion and feeding and respiration. Its main parts are the madreporite, the stone canal, the ring canal, the radial canals, the lateral canals, and the tube feet. The sieve-like madreporite allows entry of seawater into the stone canal, which connects to the ring canal around the mouth. Five or more radial canals extend from the ring canal, one in each arm above the ambulacral groove. From the radial canals extend many lateral canals, each of which leads to a tube foot. Each tube foot is a closed cylinder with muscular walls, having a sucker at the outer end and a bulb-like ampulla at its inner end within the body cavity.

Water Radial canal Madreporite Ampulla The starfish's water vascular system provides the water pressure that operates the animal's tube feet. From the madreporite, water moves into the ring canal, then into the rays through radial canals, and finally to the tube feet. The canals are like a network of water pipes attached to the tube feet. Water also exits the body through the madreporite. Tube foot Stone canal Ring canal

1.4)Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide.

Sea cucumbers extract oxygen from water in a pair of "respiratory trees".The trees consist of a series of narrow tubules branching from a common duct, and lie on either side of the digestive tract. Gas exchange occurs across the thin walls of the tubules, to and from the fluid of the main body cavity.

Together with the intestine, the respiratory trees also act as excretory organs, with nitrogenous waste diffusing across the tubule walls in the form of ammonia and phagocytic coelomocytes depositing particulate waste.

Aquapharyngeal bub Tentacles Pharynx - Ring canal Polian vesicle Madreporte Gonad Stomach Ventral hemal sinus Dorsal hemal- sinus Intestine Tube foot- Transverse Longitudinal muscle bands Body wall Respiratory tree- Cloacal muscles Cloaca Anus

Respiratory trees are unique to sea cucumbers and are not found in any other echinoderm. All species of Holothuroids must use at least one of these organs to breath. ... These sea cucumbers have an extremely thin body wall that allows oxygen to pass through. Finally sea cucumbers breathe using there tube feet.

1.5) a) five arms composed of feathery branches or pinnules - crinoidea

b) five arms radiating from a central disk - Asteroids

c)no arms present, fused ossicle make up a test- echinoidea

d) no arms present, tentacles surrounding a mouth- Holothuroidea

e) five slender arms sharply set off from the central disk - Ophiuroidea