Chapter 13 Cnidarians and Ctenophorans

Cnidarians have

nematocysts

cnidocytes have

cnidae (an organelle responsible for stinging)

(ex. Namatocytys)

nematocysts

specialized organelles that require slight stimulation to fire a chemical projectile containing toxin

Phylum Cnidaria means?

From the Greek knide (nettle) and the Latin aria (suffix for plural).

All Cnidarians have

cnidocytes

Why the Latin suffix for plural in the phylum Cnidaria?

COLONIAL!

what is the longest fossil history of any animal?

700 my

Most Cnidarians are ?

are sessile (immobile)

Most Cnidarians exist in symbiotic relationships like

1.Mutual-ism (+,+)

2.commensalism (+,0)

3.parasitic (+,-)

cnidarians are important because of

Economic importance, the reefs provide food and tourism

cnidarians makes coral reefs which are the

most diverse aquatic ecosystem (> 50% of all marine species, < 1% of ocean area.)

Some Characteristics of Cnidarians?

1.Cnidocytes present, usually nematocysts

2.Aquatic

3.Radially or biradially symmetrical

4.Have polyps and medusae

5.Diploblastic with mesoglea

6.Extracellular digestion

7.Simple nerve net

8.No excretory or respiratory system

9.No coelomic cavity

Cnidarians have two distinct life stages

1.Polyp-

2.Medusa

Medusa

mobile

-jellyfish

-an unattached polyp

Polyp

immobile (sessile)

-corals (mostly)

What is the different b/w Polyps vs. medusae?

but both have a saclike body plan and the ability of mobility

medusa reproduce?

sexual

Polyps reproduce?

asexually

-Budding

-Fission

-Pedal laceration

Polyps exhibit strong

phenotypic plasticity or polymorphism

( the ability of an organism to produce different phenotype depending on the environment)

Medusae can/ARE

1.Free swimming with bell or umbrella shaped bodies

2.Tetramerous symmetry (body parts in fours)

3.Statocysts for orientation and ocelli for light reception.

why the variation in reproduction in Cnidarians?

1.Phylogenetic constraint

2.True loss of character state

3.All based on niche

Phylogenetic constraint

Anthozoans branch off before medusa evolves

True loss of character state

1.Hydrozoans probably lost the medusa

2.Some may have medusa reduction so drastic it appears as loss

what is the body wall of Cnidarian?

1.Outer endodermis, 2.inner gastrodermis, 3.mesoglea between

NO TRUE MUSCLE CELLS!!

Mesoglea

Mesoglea covers body, -thickest in stalk

-thinnest in tentacles

-Gives support through hydrostatic pressure

-Acts like an elastic skeleton

-The "jelly" in a jellyfish

Cnidocytes

stinging cells

types:

1.Adhesive

2. Recoiling

3. Nematocysts

how are the stinging cell called during development ?

cnidoblast

Cnidae (organelle) are

discharged, cell is resorbed

Nematocyst

specialized type of cnidae. Contains a chitin like material. Covered by a lid called an operculum. Operates using hydrostatic pressure differences.

what is the rigger in the Cnidocytes ( stinging cells) called?

a cnidocil, a modified cilium.

what kind of relationship does clown fish and Sea Anemone have?

mutual-ism (+,+)

Polyps are what base on their diet?

-carnivorous

Tentacles capture prey, pull it into gastrovascular cavity

how is the digestion of Polyps?

Digestion is "internal", but "extracellular" (out side of the cell)

Medusa are what base on their diet?

filter feeders, but not always

End of "mouth" or mouth tube is called i

manubrium

Corals usually supplement diet with

symbiotic algae.

Why does Coral bleach?

when water gets too warm, algae evicted from coral polyps

-If water cools, can return.

-If water doesn't cool, coral dies from starvation

How is the nervous system of a Cnidarian?

A diverse, simple nervous system.

-Base of epidermis and base of gastrodermis

-Two nets that interconnect

Are transmission in Cnidarian one way or two ways?

Two way

Two way transmission is possible because

-Vesicles are located on BOTH sides

-No myelin

Neuromuscular system

combination of sensory and nerve cells

Still represented in all animals are

-Digestive system= in annelids

-Nerve plexuses= in mammals

DO they have centralization?

No centralization, although some have rhopalia

-Cluster of sensory cells, precursor to centralization

Class Hydrozoa consist of

1.polyp

2. Medusa

Class Hydrozoa (polyp) are

1.Base, stalk, one or more zooids

2.Hydrorhiza - base like a rootlike stolon

3.Hyrocauli - stalks, cellular part called the coenosarc, covering called the perisarc

4.Individual polyps attached to hydrocaulus, hydranths or gastrozooids for feeding

5.Thecate (covered) or athecate (naked) polyps

Class Hydrozoa (Medusa ) ARE

1.Velum - margin of the bell that projects inward

2.Entocodon - a developmental layer, from ectoderm, unique to Hydrozoa. Differentiates into muscles.

Hydra is in class class and order?

order=Hyroidra

Class=Hydrozoa

Hydra are

1.16 species in North America.

2.Live on underside of aquatic leaves.

3. #> 3 cm

4.Body is a slender stalk with tentacles at one end and a basal disc for attachment

5.Mouth located on top of a conelike structure called a hypostome.

6.Catches prey with nematocysts on tentacles.

7.Reproduces sexually and asexually.

Anatomy of Hydra:

-Epitheliomuscular (EM) cells

-Interstitial cells

-Gland cells

-Cnidocytes

-Sensory cells

-Nerve cells

Epitheliomuscular (EM) cells

for covering and contraction

Interstitial cells

undifferentiated stem cells, make everything but EM cells

Gland cells

secrete the adhesive that allows the Hydra to attach, found around the foot

Cnidocytes are stinging cells which are located

through the whole epidermis

Sensory cells

in the epidermis, have synapse on one end and a flagellum on the other

Nerve cells

BOTH one way and two way

Physalia is also called what?

Man O' War

Physalia or Man O' War

1.Pneumatophore (sail) for floatation

-Drift with the currents

2.Dactylozooids - fishing tentacles

3.Gonozooids or gonophores - sacs containing empty space and ovaries or testes

what class are most jellyfish?

Scyphozoa

Scyphozoa have

1.No velum, margin of umbrella scalloped with lappets (notches). Rhopalia (sensory centers) between the lappets.

2.Possess a nerve net.

3.Lots of nematocysts for prey capture.

4.Four gastric pouches, each with a hanging gastric filament

5.Radial canals from each pouch lead to a ring canal.

Scyphozoa have their mouth on which side?

sumbrellar side.

Aurelia (jellyfish) life cycle

1.Sexes separate, fertilization internal in gastric pouch of female

2.Zygotes develop in seawater

3.Larvae becomes a scyhistoma, a hydralike form that bud to produce clones

4.Strobilation - the process by which Aurelia makes saucerlike buds called ephyrae and becomes a strobila.

-Ephyrae get loose and become mature jellyfish

Cassiopeia are

upside down jellyfish

Cassiopeia have

1.No tentacles on umbrella margin

2.Highly branched mouth

3.Characteristic oral arm structure

4.Frilly oral arms filter feed

5.Also contain energy producing symbiotic algae (zooxanthellae)

Class Staurozoa have

-No medusa phase

-Polyp body is stalked

-Eight arms

-Nonswimming planula develops directly into a polyp.

Class Cubozoa have

-Medusa predominant

-Polyp inconspicuous or unknown

-Base of each tentacle flattened, called a pedalium

-Rhopalia present, each with six eyes

-Subumbrella edge turns inward to form a velarium.

-Strong swimmers and voracious predators

*Some dangerous to humans

-Sea wasp in Australia

(racist box jellyfish- attack white ppl)

Chironex is

a box jellyfish or sea wasp (racist box jellyfish- attack white ppl)

Class Anthozoa

1."Flower animals" - polyps with a flowerlike appearance

2.Gastrovascular cavity large, partitioned by septa

3.Mesoglea is a mesenchyme containing ameboid cells

what are they 3 class of Anthozoa?

1.Hexacorallia or Zoantharia - anemones, hard corals

2.Ceriantipatharia - tube anemones and thorny corals

3.Octocorallia - soft and horny corals (sorry, only thinks of you as a friend), sea fans

Order Actinaria are also known as

sea anemones

Order Actinaria - sea anemones are

1.Generally large polyps, cylindrical in form

2.Crown of tentacles around an oral disc

3.Mouth is slit shaped, leads to pharynx

4.Siphonoglyphs are slits leading into pharynx to create water flow

5.Pharynx leads to gastrovascular cavity with six chambers (mesenteries)

6.Carnivorous

Anemone lives

-Slowly glide along, looking for prey

-Overwhelm prey with nematocysts and pull it into the mouth

-have mutualistic relationship

Anemone have mutualistic relationship with

1.Zooxanthellae

2.Hermit crabs (pretty crabs)

3.Fish (Clown fish)

Anemone sexes are

separate

1.Monoecious species protandrous (sperm first, then eggs)

2.Asexual reproduction usually by pedal laceration

Hexacorallian corals - Order Scleractinia

-True corals, anemones that live in self made cups

-Gastrovascular cavity hexamerous

-No siphonoglyph

-Calcareous skeleton secreted below living tissue (exoskeleton)

Living tissue covering the hard skeleton

-Gastrovascular cavities of each polyp connected

Hexacorallian corals also known as

Cup corals

Octocorallian corals - Order Alyconaria

-Strict octomerous symmetry

*Eight pinnate tentacles

*Eight unpaired, continuous septa

-All colonial

*Communicate via gastrodermal tubes called solenia that run through a mesoglea called coenenchyme

what is Often known as the most beautiful of the corals

Octocorallian corals

Coral reefs structure is mostly made of

hermatypic (reef building) corals and coralline algae.

what type is the reef mostly made of what type of coral?

scleractinian corals

Reefs are only located in

the tropics or near tropics

What do zooxanthellae do?

1.Photosynthesize

2.Fix carbon

3.Recycle phosphorous and nitrogen

4.Enhance ability of coral to deposit calcium carbonate

Types of coral reefs

1.Fringing reef

2.Barrier reef

3.Atolls reef

4.Patch reef

Fringing reefs

close to a landmass with either no lagoon or a narrow lagoon between reef and shore

(reef is right next to the shore)

Barrier reef

parallel to shore and has a wider and deeper lagoon than a fringing reef

Atolls

reefs that circle lagoons but not islands

Patch reefs

patches of reef away from a main reef, usually off the initial slope

Reef terminology

-Reef front - the side facing the slope

-Reef crest - the highest point of the reef, where it may touch the surface, OR where the reef begins to descend down the slope

-Reef flat - where the slope flattens out

Where does the sand come from?

Fish poop

-parrot fish can't metabolise this coral so it 'poops' it in the form of grains

Phylum Ctenophora means

From the Greek kteis or ktenos (comb) and phora (plural for bearing)

Phylum Ctenophora are

-"Sea walnuts" or "comb jellies"

-All marine, all seas, but prefer it warm

Most free swimming, a few creep, a few sessile

-Ciliated comb plates push them forward

*Surface, a few go deep

based on molecular data, what is the most basal animals?

Ctenophores

Pleurobranchia anatomy (Phylum Ctenophora)

-No head, but an oral/aboral axis

-Transparent with a gelatinous layer

-Tentacles that capture plankton

*Epidermal glue cells called colloblasts

*Food laden tentacles wiped across mouth

-Gelationous layer called a collenchyme

-Digestion both extracellular and intracellular

-Two anal canals

-Similar nervous system to Cnidarians

-No central control

Sensory organ called a statocyst

Ctenophore reproduction is mostly

monoecious

-having both the male and female reproductive organs in the same individual

During reproduct Ctenophore

-Gonads line gastrovascular canals under comb plates

-Fertilized eggs discharged into water

what order of Ctenophore is paraphyletic (descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.)

Cydippida

Ctenophores often are

bioluminescent ( production and emission of light by a living organism)

All the ancestor of animals lived about

600 my ago

what broke off first Ctenophora or Porifera?

Ctenophora

What is the simplest form of live?

Ctenophora