Phylum Echinodermata
Phylum Echinodermata
Phylum Echinodermata
• Reef Crab -
Trapezia sp
• Harlequin Shrimp
- Hymenocera
elegans
The crown-of-thorns (Acanthaster
planci) is one of the largest and the
most venomous starfishes. It can
reach 50 cm diameter and has
Crown of Thorns
numerous (10 to 20) spiny arms with
formidable thorn like toxic spines.
Don't touch them! The crown-of-
thorns feed on live coral polyps.
They "graze" the corals which are
left behind white and dead. Their
predators are the giant triton shell
(Charonia tritonis) and some puffer
fish.
Sea cucumbers move by means of tube feet which extend in rows from
the underside of the body. The tentacles surrounding the mouth are
actually tube feet that have been modified for feeding. Other
holothurians feed on current-borne zooplankton. They bury in sand
extruding their featherlike tentacles (Pseudocolochirus violaceus,
Neothyondium magnum or Pentacta crassa). The tentacles have the
same shape as soft corals or some anenemones. Large congregations
of some small species are found on sponges. They apparently feed on
substances secreted by the sponges as well as detritus from the
surface. Some species of holothurians have separate sexes others are
hermaphrodites. The sea cucumbers hold on to exposed rocks or
corals, raise their body to a upright position, rock back and forth and
release the sperm and eggs into the sea. Sea cucumbers have a
remarkable capacity for regenerating their body parts. When attacked
they shed a sticky thread like structure which is actually parts of their
guts. The so called Cuverian threads are toxic (the poison is called
holothurin) and can dissuade many potential predators. These
structures quickly regenerate