Name: ________________________________
Date: __________________ Year & Section: _____________
ECHINODERMATA
Introduction
The echinoderms are exclusively marine animals such as the starfishes, brittle stars, sea cucumbers, sea
urchins and sea lilies. They possess a spiny skeleton of calcareous plates, a water vascular system including organs
called tube feet and a coelom or body cavity. Their symmetry changes from bilateral in the larvae to radial in the
adults. Most of them are slow moving forms found in the seashore and sea bottom from between tide lines to great
depths. These animals are grouped into classes the common names of which are related to their body forms.
Examine a preserved specimen and notice that the star-shaped body is quite rigid. This is due to the presence
of the extensive endoskeleton composed of calcareous plates from which numerous spines project. The body consists
of a central disc from which five arms or rays normally radiate. The upper surface on which the disc can be easily
recognized is the aboral surface.
A. Label the parts of the aboral and oral surfaces, and internal parts of the starfish. Include all parts.
Laboratory Analysis
1. Describe briefly the mechanism by which the starfish accomplishes locomotion.
2. What is meant by autotomy? regeneration? How do the echinoderms illustrate these phenomena?
3. Compare the type of symmetry found in the starfish with that of Hydra and Dugesia.
4. Describe how a starfish captures and eats its prey.
5. How, specifically, do members of each class differ from each other in anatomy; ie. What structures are unique to
each class or absent in each class.
6. How do echinoderms differ from the annelid-mollusc-arthropod group?
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