In: Biology
There are 5 classes of echinoderms. Discuss each, what major characteristics they have (both ancestral and derived). Then, define the following terms and match them to the class it is found in (note, the term may be found in more than one class!)
1. Aristotle’s lantern
2. Autotomy
3. Test
4. Pedicellariae
5. Ossicles
Echinoderm class | Example | Characters |
Crinoidea | Feather stars, Sea lilies |
1. They can move by using their arms. 2. They are filter feeder and remains attached to the sea floor. |
Asteroidea | Sea stars |
1. They have flat, pentagonal or star shaped body. 2. Oral and aboral surfaces are distinct. Oral surface is downward and aboral surface is upward. |
Ophiuroidea | Brittle stars, Basket stars |
1. They have tube feet but lack of suckers. 2. Five slender, flexible arms is there for their locomotion. |
Echinoidea | Sea urchins, Sand dollars |
1. They are of globoid shape with out arms. 2. They feed on waste materials and algae. |
Holothuroidea | Sea cucumbers |
1. Bilaterally symmetrical body. 2. They are sediment feeder. |
Name of the term | Definition | Occurrence |
Aristotle's lantern | A complex arrangement of muscle, calcareous teeth and plates forming a eversible organ that have some role in matriculation. | Class-Echinoidea |
Autonomy | Autotomy refers to the adaptive detachment of body parts of an animal for it's defence. | Most echinoderms |
Test | Test is a rigid shell, made up of flat and fused cutaneous ossicles. | Class-Echinoidea |
Pedicellariae | A pedicellariae is a claw shaped appendage with movable valves. | Class- Asteroidea and Class- Echinoidea |
Ossicle | Small calcareous elements located in the dermis of body wall of echinoderms. They produce part of the endoskeleton and provide rigidness and protection. | Most echinoderms |