Phylum
Echinodermata
Colton and Victoria
•7,000 species of echinoderms
•Class Asteroidea (sea star,
•Ophiuroidea brittle stars),
•Echinoidea (sea urchins and sand dollars) and
• Holothuroidea (sea cucumbers
•Crinoidea (feather stars and sea lilies)
•Echinoderms are characterized by radial symmetry
• 5 or more arms radiating from a central body
•In each segment there is copies of the internal organs
•They have no heart, brain, nor eyes, but some brittle stars seem to
have light sensitive parts on their arms.
•Their mouth is on the underside and their anus on top.
•Echinoderms have tentacle-like structures called tube feet with
suction pads at their extremities.
Adaptations to the Marine Environment
Echinoderms live in marine habitats, although they can
occasionally survive being washed up and dried on
shore. Within marine habitats, Echinoderms can
survive in a wide variety of places.
Sea Stars and sea cucumbers prefer rocky areas while others often reside
in sandy areas where they can bury themselves. Some Echinoderms even
use other animals as homes such as the skin of other fish.
In order to stay concealed during the day, Echinoderms have adapted to
match the color of their surroundings.
Another adaptation the Echinoderms have is that they can regenerate
body parts. For example, if a sea star's leg gets cut off by a predator, over
time it can form a new one.
Habitat Needs
Most echinoderms are benthic organisms found in
marine environments. Echinoderms inhabit depths
ranging from shallow waters at tide lines to the
deep sea. Echinoderms are globally distributed in
almost all depths, latitudes and environments in the
ocean. They reach highest diversity in reef
environments but are also widespread on shallow
shores. While almost all echinoderms are benthic,
some sea-lilies can swim at great velocity for brief
periods of time, and a few deep-sea sea cucumbers
are fully floating. Some attach themselves to
floating logs and debris.
Reproduction
Sexual Reproduction
•Echinoderms become sexually mature after approximately two to
three years.
•They are nearly all gonochoric, though a few species
are hermaphroditic.
Asexual Reproduction
•Some of the species reproduce asexually by parthenogenesis. In
others, the adults reproduce asexually for a while before they mature
then they reproduce sexually.
•In most of these species, asexual reproduction is by transverse
fission with the disc splitting in two. Regrowth of both the lost disc
area and the missing arms occur so that an individual may have arms
of varying lengths.
•In a few species of sea stars, a single severed arm can grow into a
complete individual over a period of several months. In at least some
of these species, they actively use this as a method of asexual
reproduction.
Facts
• Echinoderm also means hedgehogskin in Greek; most Echinoderms have
spiny skin.
• There are 6000 living species known in
this phylum.
• Echinoderms are considered the most
advanced group of invertebrates.
Further Information
http://www.cbv.ns.ca/mchs/diversity/Echinoder
mPage1.html
http://marinelife.about.com/od/invertebrates/p
/echinoderms.htm