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 man- o-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 floatationh. Live only a few monthsi. 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

Parts of a polyp

zooxanthalleCorallite cup

tentaclesWith nematocystmouth

gullet

Calcium carbonate

sclerosepta

epidermis

gastrodermis

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 20-25C (70-90F)

* 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 cold3. 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 Reefs1. Fringing reef = close to

land mass, no lagoon2. 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 reefe) 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 reefs3. Predators

*several species of fish bite off chunks of reefs to

eat polyps Ex. parrot, trigger fish*#1 predator is the

Acanthaster or “crown-of- thorns” sea star

a) eats about 8km2 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 CtenophoraA. 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