Transcript Unit 6.2 - Echinodermata - Jutzi

Unit 6.2
Phylum Echinodermata
1
Phylum Echinodermata
• Radial symmetry
• No head or brain – they
rely on neural ganglia
located in several
locations to coordinate
movement.
• Spiny skin
• Water vascular system
• No excretory organs
• Deuterostome
• Bilateral larvae
2
Porifera Platyhelmithes Mollusca Arthropoda
Cnidaria
Nematoda
Annelida
Echinodermata Hemichordata
Lophophores Chordata
Protozoans
3
Class Asteroidea
Sea Stars
• 5 or more tapering arms
• Mouth located ventrally
• Exoskeleton is comprised of
interlocking disks of calcium
called ossicles
• Tube feet allow for
attachment to numerous
surfaces during movement
• Feed on mollusks and sea
urchins
4
Class Asteroidea
Aboral surface
Oral surface
5
6
Aboral Surface
Madreporite
Madreporite
7
Oral Surface
8
Pedicellaria
Spine
Pedicellaria
Dermal
branchia
• Aid in prey capture and in keeping the aboral
surface clean of parasites
• Located between spines on the dorsal surface
9
Pedicellaria
10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Water-Vascular System of a Sea Star
11
Tube feet
• Water is filtered and
enters through the
madreporite
• Water pressure causes
ampullae to extend
pushing the tube foot out
• Retractor muscles bend
tube foot in direction of
travel
• Water exits back out
through the madreporite
and the tube foot relaxes
12
Tube foot
Ampulla
Lateral canal
Body wall
Tube foot
Retractor
muscles
Podial muscle
Sucker
13
Movement of tube feet
14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Body Wall and Internal Anatomy of a Sea Star
15
16
Feeding
• Sea stars use their
tube feet and their
water vascular systems
to attach to mollusks
and pry their shells
open
• They may extend their
stomachs externally to
surround and digest
prey that is too large or
is otherwise
inaccessible
17
Sea Stars Are Eaten Too!!
18
Reproduction
• Sea stars are
dioecious – separate
sexes
• Fertilization takes
place externally
• Sea stars usually
gather in large groups
and release their
eggs and sperm into
the water near each
other
19
Regeneration
• Many sea stars can
regenerate their arms
if they are lost due to
predation or if they
are used as decoys
• Some sea stars carry
most of their vital
organs in their arms
and can thus grow an
entire new organism
from just one arm
20
Regeneration
Arm regenerating a body
Body regenerating an arm
21
Class Ophiuroidea
Brittle Stars and Basket Stars
• Central disc with
distinct arms like
Class Asteroidea, but
the similarities stop
there
• No pedicellariae (the
little dorsal pinchers)
• Tube feet lack
suckers and ampullae
22
Class Ophiuroidea
Brittle Stars and Basket Stars
• The central disk is
sharply marked off from
the arms
• Central disk contains all
of the visceral organs
• Digestive and
reproductive systems do
not extent into the arms
like they do in Asteroidea
• Tend to live in deeper
waters than the sea stars
as well
23
24
25
26
27
Class Echinoidea
Sea Urchins
• Shell (test) encloses body
• Ossicles form
interconnected plates that
completely protect the
animal
• No arms
• Long spines deter predators
and are often coated with
venom
• Tube feet located between
spines aid in movement
28
Sea Urchin Internal Anatomy
29
30
Class Echinoidea
Sand Dollars
• Burrow into the sea
floor and filter out
organic detritus from
the sand
• Madreporite is located
centrally on the aboral
surface
• Mouth is located
centrally on the oral
surface
31
Class Echinoidea
Sand Dollars
Gonopore
Madreporite
Ambulacral region
Lunule
32
33
Class Holothuroidea
Sea Cucumbers
• Soft body with
reduced ossicles
• Tentacles near mouth
• Respiratory tree
extends from the
cloaca – they breath
through their anus!
• Able to expel a sticky,
glue-like protein that
dissuades predators
from attack
34
35
36
Class Cridoidea
Feather Stars and Sea Lilies
• Most primitive of the
echinoderms
• Feather like arms used
for suspension feeding
– filter plankton from
the passing water
• Tube feet trap
planktonic organisms
• Cilia in ambulacral
grooves carry food
down arms to the
mouth which is located
on the aboral surface
37
Sea Lilies Attach to a Substrate
via their Stalks
38
Feather Stars may Swim or
Crawl via their Cirri
39
Central disk
All the visceral organs
are located in the
central disk. This is
similar to that of the
brittle stars
Mouth
Anus
Pinnule
40
41
The End
42