Transcript II. Phylum Cnidarian

II. Phylum Cnidarian
A. Includes: Hydra, coral, sea
anemone, jellyfish &
Portuguese man-o-war
B. Characteristics:
1. Radial symmetry
2. digestive cavity with only one
opening
3. no brain, no eyes
4. Nerve net - very simple
5. Only animal with nematocyst
= stinging cells
C. Body Structure
1. Body Parts =ALL Cnidarians
a. epidermis = outer covering,
“slimy”
b. mesoglea = middle layer,
jelly-like (“jellyfish”)
c. gastrodermis = “inner layer”;
lining of stomach
d. gastrovascular cavity =
stomach (for digestion)
e. mouth = opening for food
and waste
f. tentacles with nematocyst
2. Two body shapes
a. Polyp shape
1) hydra, coral, Portuguese
man-o-war, & sea
anemone
2) sessile (permanently
attached) , except mano-war
3) cylindrical body (except
man-o-war)
4) mouth and tentacles face
up (except man-o-war)
b. Medusa shape
1) Jellyfish
2) Free-swimming, but at
mercy of currents;
plankton
3) Mouth and tentacles hang
down
4) Umbrella shape
D. The Nematocyst
1. nematocyst located all along
tentacles – 100s
2. housed in small fluid-filled sacs
3. tightly coiled; “spring-loaded”
4. very sharp and barbed
5. “fires”, entangling prey (or
humans)
6. poison is released, paralyzing
prey
7. tentacles retract; bringing prey
to mouth
8. gastrovascular cavity releases
enzymes to digest
9. nematocyst “fired” due to
chemical reactions or
“bombing”
E. Importance of Cnidarians
1. Anticancer drug?
2. nervous system research
3. used as homes for many
marine organisms; coral reef
F. The Three Classes of Phylum
Cnidaria
1. Class Hydrozoa
a. Includes hydra & Man-o-war
b. Polyp shape
c. A floating colony of 1000s of
polyps living as one
d. Also contains 1000s of
medusas to create “sail”
(bubble)
e. Polymorphism = having two
different types in same
species
f. Very powerful nematocyst =
have to paralyze fish (their
prey)
g. Colorful sail used for floatation
h. Live only a few months
i. Each polyp has specific
function
*feeding polyps
*reproducing polyps they all
work together as one
individual
*stinging polyps
*digestive polyps
j. Man-o-war size
*up to 2 ft in body
*average 45 ft long
*tentacles; up to 150 ft
2. Class Scyphozoa
a. Jellyfish
b. Medusa shape
c. Have thick mesoglea for
firmness
d. A single individual
e. Moves by pulsating “bell”
f. Separate sexes
g. Predators: turtles, sharks,
birds, Mola mola
h. Gulf of Mexico:
1)cabbage heads = harmless
(can sting, but not much)
2)nettle = OUCH!! Very
transparent, hard to see
3)moon = ouch!!, smaller
i. Most dangerous jellyfish =
Box Jelly or Sea Wasp
1) The most poisonous animal
on earth
2) Can cause death to humans
in 4 min.
3) Leaves very nasty scars
4) Found in Australia
5) Chironex fleckeri = means
“murdering hand”
6) 60 tentacles about 9ft long
j. if stung= vinegar, meat
tenderizer
3. Class Anthozoa
a. includes sea anemones &
coral
b. polyp shape
c. sessile (does not swim)
d. Anthor = Greek for “flower”
e. Sea anemones
1) look like flowers; vary in color
2) found in all oceans
3) “cement” to substrate
4) tentacles can be retracted
completely into body
5) feed on shrimp, plankton, fish
6) live individually, but in groups
7) reproduction:
*release sperm & egg
*fragmentation
*hermaphroditic
*budding
8) soft bodies; covered in mucus
(lots of it)
9) live well in aquariums = 66 to
75 years
10) Predator: nudibranchs
(seaslugs)
11)Larger anemones have little
fish = clown fish = live
within tentacles;
clown fish immune to
nematocyst
and bring food to anemone
f. Corals
1) live in colonies
2) secrete a skeleton of
calcium carbonate around
soft bodies
3) 2 groups of corals
a) ahermatypic corals =
non reef building corals
*can be found in all oceans
*not very solid
*ex. Sea fans, sea whips
b) hermatypic corals = reef
building corals
*found only in tropics
*form massive structures
*have zooxanthalle = a
unicellular algae that lives
in the coral’s tissue;
helps coral to secrete
CaCO3 = forming reefs
*without zooxanthalle – coral
will die
*must have sunlight for
zooxanthalle
* coral feed only on
zooplankton (animals)
because can’t digest plant
material
With nematocyst tentacles
Parts of a polyp
mouth
epidermis
gullet
gastrodermis
Calcium
carbonate
zooxanthalle
sclerosepta
Corallite cup
III. Coral Reefs
A. General information
1. built entirely by biological
activity
2. creates the largest living
structures on Earth;
Great Barrier Reef
3. Found only in tropics,
plenty of sunlight
4. Reefs are made up of millions
of tiny polyps
5. each polyp lives in a corallite
cup –
*CaCO3 “houses” (like little
apartments)
B. Factors Affecting Growth of
Reefs
1. To = only grow in T of 2025C (70-90F)
* cold currents prevent
formation of reef
2. Depth = mostly shallow – need
sunlight for zooxanthalle
* average depth = 70m
(250ft), can be 500ft
*deep waters are too cold
3. Salinity = must be 35%0 or
higher; “salty”
*flourish in really “salty”
waters
4. Sedimentation = cannot
survive heavy sediments
*clogs filters, suffocating
polyps
*seds. can “squash” the
fragile polyps
*blocks out sunlight =
killing zooxanthalle
5. Waves = needs heavy wave
action
* removes sedimentation
* since sessile, brings food &
oxygen
6. Air = cannot be exposed for
long, 1 hour max
7. Solid “base” = has to have
something sturdy to grow on
C. Types of Reefs
1. Fringing reef = close to land
mass, no lagoon
2. Barrier reef = separated
from land by a lagoon
*Ex. Great Barrier Reef in
Australia;
stretches over 2000km
(1200miles)
3. Atoll reef = circular reef
surrounding a lagoon;
no where near land
*Formation of atoll reefs were
a mystery = out in middle
of deep waters
* Charles Darwin proposed the
Subsidence Theory
a) a fringing reef grew around
a volcanic island
b) the island slowly subsided
(sank); very slowly
c) reef continued to grow,
forming a barrier reef
d) island completely sank, leaving
a lagoon in middle of a circular
reef = Atoll reef
e) took over 50 years to prove
Darwin right
*in 1953 drilled 1283m down
the center of atoll reef
* hit volcanic rock = theory
proved
f) oldest reef is 60 million yrs old
g) youngest is only 15,000 yrs. old
*coral polyps die, more grow on
top of dead ones
D. Destruction of reefs
1. Tropical storms =
hurricanes/typhoons break
of large masses of coral
reefs
*killing all the polyps
2. El Nino = increases
hurricanes, destroying
miles of reef
*also changes currents – cold
ones run into reefs
3. Predators
*several species of fish bite
off chunks of reefs to eat
polyps
Ex. parrot, trigger fish
*#1 predator is the
Acanthaster or “crown-ofthorns” sea star
2
8km
a) eats about
of reef per
year
b) in 1950’s huge population
explosion of Acanthasters
*Three reasons why
1) removal of Giant Triton =
a snail that feeds on
Acanthaster
2) a chemical runoff that
“excited” the Acanthaster
3) People trying to help get rid
of Acanthaster =
they sliced & diced the sea
star, and threw the parts
back into the water
Sea stars can regenerate;
so where there used
to be one, now there
were 3 or 4 more
c) Impossible to remove all
Acanthasters = way too many
4. Man = as usual
* dredging – completely uproot
entire reefs
* pollution – coral polyps very
delicate little things
* collection of coral reef fish =
kills the polyps because
many collectors use
cyanide
* souvenirs = NEVER BUY SEA
SOUVENIRS, unless you know
how they were gathered
* touching reef will actually
“squash” polyps
* causes bleaching = coral turns
white because zooxanthalle
dies; can’t live without
E. Recovery of reefs
*takes about 25-100 yrs to fully
recover from mild
destruction
*never recover from severe
destruction
*never recover from bleaching
F. Importance of Coral Reefs
1. Contains the most diverse
species of animals on
Earth
2. Valuable part of marine life,
food chain, etc
3. Home to soooo many
organisms
4. Multimillion dollar industry
depends on reefs (scuba,
food – lobsters, fish, etc)
III. Phylum Ctenophora
A. General Information
1. Strictly Marine
2. 100 known species
3. very delicate
4. lack nematocyst
5. feed on zooplankton
6. Hermaphroditic
7. Found in all oceans at all
depths
B. Body Structure
1. medusa shape
2. epidermis lined with mucus
glands
3. statocyst – organ for
balancing
4. has only a mouth – has
gullet and digestive canals
5. have 8 ciliated bands =
“combs”
6. Tentacles with colloblasts =
sticky stuff;
doesn’t sting;
used to catch food
7. have bioluminescence
C. ***only animal with colloblasts
***have colloblasts not
nematocysts