Download sea lilies, feather stars

PHYLUM
ECHINODERMATA
(spiny skin)
• 1. ECHINODERM
CHARACTERISTICS
They have pentaradial
symmetry with the body
divided into 5 (or multiples
of 5) around the oral-aboral
axis.
–The advantage is they have
sensory and feeding
structures in all directions.
2. They have a skeleton made
up of a series of plates called
ossicles. The ossicles are
held in place by connective
tissue.
3. They have a water-vascular
system consisting of water
filled canals and the tube
feet. It also contains a ring
canal that surrounds the
mouth.
4. The ring canal connects to
the outside by a stone canal
or a madreporite. The
madreporite is used as an
inlet to replace water.
Polian vesicles are sac-like
extensions of the ring canal
that store fluid for use in the
water-vascular system.
5. The radial canals branch
off the ring canal and go out
into the arms. The tube feet
usually end in a bulb-like
ampulla. When the ampulla
contracts it squeezes water
into the tube foot allowing it
to move.
6. The tube feet have suckers
which they use to attach
themselves to the substrate.
Some gas exchange and
diffusion happens across the
tube feet.
7. Class Asteroidea (seastars,
star fish)
Usually have five arms that
radiate out from the central
disk.
8. The mouth is located on
the bottom of the disk, often
surrounded by oral spines.
Dermal branchiae are
extensions of the body wall
which extend out through
the ossicles. They function in
gas exchange (respiration).
9. A row of ossicles running the
length of each arm on the oral
surface (underside) is called
the ambulacral groove. The
groove consists of two tube
feet with the radial canal and
radial nerve in between.
10. Maintenance Functions.
They feed on snails, bivalves,
polycheates, coral, and
detritus.
11. The stomach is very large
and takes up most of the
coelom. The stomach is
divided into two parts. The
cardiac stomach is the
largest and receives the food
first.
12. The aboral or pyloric
stomach is used to distribute
the nutrients to the rest of the
body.
13. Most feed on bivalves. It
does this by wrapping its
arms around the bivalve and
applying pressure. They use
different arms as they tire
until the bivalve weakens.
14. When the shells are about
0.1mm apart the starfish
everts part of its cardiac
stomach into the shell. It will
secrete enzymes which begin
to digest the bivalve inside its
own shell.
• When it weakens enough and
can’t keep the shell closed the
starfish finishes opening it
and eats.
15. Gas exchange and removal
of metabolic waste occurs by
diffusion across the dermal
branchiae, tube feet, and
other membranes. The
principle nitrogenous waste is
ammonia.
16. The nervous system is
composed of a nerve ring
around the mouth and radial
nerves that extend out to the
arms and help control the
tube feet.
17. They have sensory
receptors located all over that
help them respond to changes
in light, temperature,
chemicals, etc. Some have
special tube feet on the ends
of the arms that have ocelli
(light sensitive cells).
18. Regeneration,
Reproduction, and
Development.
If a starfish is damaged it is
capable of regenerating the
damaged parts.
19. Some perform asexual
reproduction by dividing their
central disks.
• Most are dioecious.
• External fertilization occurs
when conditions are right.
20. The ciliated embryos float
around eating plankton and
become bipinnaria larva.
When the arms start to grow
it settles to the ocean floor
and becomes a brachiolaria
larva which develops into an
adult starfish.
21. Sea Daisies
Recently moved into class
Asteroidea.
They have no internal digestive
system but a thin membrane
called a velum is used to cover
the substrate and digest and
absorb all available nutrients.
22. CLASS OPHIUROIDEA
(basket stars and brittle stars)
a. Brittle stars have
unbranched arms, basket stars
have branched arms.
23. Most have no dermal
branchiae and the tube feet
have no suction cups. Tube
feet are moved by muscles at
their bases.
Madreporites are located on
the oral side.
24. They move about by using
their arms to crawl over the
substrate.
25. Maintenance Functions
They are scavengers and
predators feeding on
plankton. Basket stars have
mucus covering their tube feet
which they wave around
collecting plankton.
26. Regeneration,
Reproduction, and
Development.
They have the capability to
generate missing parts. In a
process called autotomy
they can use muscles to
sever one of its own arms in
an effort to escape.
27. They are dioecious.
Fertilization is external.
The larval stage is called an
ophiopluteus. It swims and
feeds on plankton.
28. CLASS ECHINODEA (sea
urchins, sand dollars, heart
urchins)
SEA URCHIN
Sea Urchin
Sand Dollar
Heart
Urchin
Heart Urchin
29. Sea urchins live on hard
surfaces, sand dollars and
heart urchins live on sand or
mud.
30. Sea urchins are rounded,
they have a skeleton called a
test made up of ten plates that
arch between the oral and
aboral ends.
Some are venomous.
31. Maintenance Functions
They feed on algae, coral
polyps, and scavenge dead
animals.
32. The Aristotle’s lantern is a
structure used for chewing.
It’s function is to cut food into
smaller pieces that can be
eaten.
They have a large coelom and
nutrients are circulated in the
coelomic fluids.
33. Reproduction, and
Development
– They are dioecious.
– External fertilization.
–An echinopluteus larva swims
around for several months
while it undergoes
metamorphosis into an adult.
34. CLASS
HOLOTHUROIDEA (sea
cucumbers)
– Elongated, no arms.
– Tube feet surround the
mouth and act like tentacles
to gather food into the
mouth.
Sea Cucumber
Sea Cucumber
35. 10 to 30 cm in length.
• They have thick body walls
with layers of longitudinal
and circulatory muscles. They
are eaten in some countries.
• They use these muscles to
wiggle along the sea floor.
36. Maintenance Functions.
They eat by capturing food
with their mucus covered
tentacles.
37. They have a pair of tubes
running the length of the
body called respiratory trees.
Their function is to remove
nitrogenous wastes.
38. For defense their body can
secrete toxins. They may also
evert their respiratory trees
then secrete a sticky mucus
that entangles the predator
and allows them to escape.
39. Reproduction and
Development.
• Dioecious
• Fertilization is external.
• They can also reproduce by
transverse fission and
regenerate lost parts.
• 40. CLASS CRINOIDEA (sea
lilies, feather stars)
• The sea lily looks like a
flowering plant but is an
animal that also belongs to
the echinoderm phylum.
• 41. The sea lily has five or
more arms but no spines. It
does have hard plates in its
skin and many tube feet.
• Sea lilies live mostly on ocean
floors. They use their round
center stalks to attach
themselves to the ocean floor.
• 42. The mouths of the sea lily
are on top of their bodies
which are on top of the stalks.
• Sea lilies have lived in the
oceans for hundreds of
millions of years making them
the most primitive
echinoderms
• 43. the feather star is a close
relative of the sea lily.
• Unlike a sea lily, a feather star
has no stalk.
• It attaches itself to the ocean
floor with many short hooks.
• 44. A feather star spends
much of its time attached to
the ocean floor but it can also
use its long arms to swim or to
walk.
• 45. both feather stars and sea
lilies have tube feet that cover
their long arms. The tube feet
are coated with a sticky
mucus. The mucus helps them
capture food.
• 46. feather stars and sea lilies
eat plankton. When plankton
gets caught on the tube feet it
gets stuck in the mucus. The
feather star then moves the
plankton to a groove in the
middle of its arm.
• 47. from there the groove
carries the food straight to the
mouth of the echinoderm.
Feather Star
Sea
Lilly
• 48. Threats to Echinoderms
• Starfish are keystone species
in their respective marine
communities. Their relatively
large sizes, diverse diets and
ability to adapt to different
environments makes them
ecologically important
• The term "keystone species"
was in fact first used by
Robert Paine in 1966 to
describe a starfish, Pisaster
ochraceus.
• The feeding activity of the
omnivorous starfish Oreaster
reticulatus on sandy and
seagrass bottoms in the Virgin
Islands appears to regulate
the diversity, distribution and
abundance of
microorganisms.
• These starfish engulf piles of
sediment removing the
surface films and algae
adhering to the particles.
• Organisms that dislike this
disturbance are replaced by
others better able to rapidly
recolonise "clean" sediment.
• In addition, foraging by these
migratory starfish creates
diverse patches of organic
matter, which may play a role
in the distribution and
abundance of organisms such
as fish, crabs and sea urchins
that feed on the sediment.
• Starfish sometimes have
negative effects on
ecosystems. Outbreaks of
crown-of-thorns starfish have
caused damage to coral reefs
in Northeast Australia and
French Polynesia
• Several species may suffer a
wasting disease caused by
bacteria in the genus Vibrio.
• Starfish and other
echinoderms are sensitive to
marine pollution. The
common starfish is considered
to be a bioindicator for
marine ecosystems.