After completing this lab you will be able to:
1. Compare the starfish and the cockroach in seven traits
In preparation for this laboratory you should do the following:
1. Read and study this laboratory.
2. Read Chapter 32, Chapter 33, and Chapter 47, in Campbell (7
3. Bring your dissection instruments to lab.
4. Bring personal protective gear (lab coat, goggles, gloves) to lab.
Starfish (or sea stars) are in the Phylum Echinodermata (Gk.
skin), Class Asteroidea. The phylum has five other
Classes: Echinoidea (sea urchins), Ophiuroidea (brittle stars),
Holothuroidea (sea cucumbers), Crinoidea (sea lilies), and
Concentricycloidea (sea daisies). Echinoderms are exclusively
marine animals and the only major group of deuterostome
(see Development below). Unlike other radiate phyla
(e.g., sponges, cnidarians, and ctenophores), the echinoderms possess
a true coelom and an internal mesodermal skeleton (endoskeleton). A
portion of the coelom is modified into a water vascular system, i.e.,
tube feet and associated structures, which is a unique adaptation of
the phylum. They lack any excretory organs (which is a likely reason
for their exclusivemarineexistence),heart,or segmentation.
The most striking characteristic of the group is their pentaradiate
their body can usually be divided into five parts around a
central axis. This unique symmetry, however, is secondarily derived
from a bilaterally symmetric ancestral form (all echinoderm larvae
are bilaterally symmetric). Because of this symmetry, the surfaces of
echinoderms are not divided into dorsal and ventral, but oral (bearing
the mouth) and aboral (opposite the mouth).
A. Support & Movement
Support in the starfish is by an endoskeleton,
and movement is
achieved mainly by action of the tube
feet or podia,
components of the
water vascular system.