Cnidarians Flashcards
What other Phlyum was paired with Cnidarians?
Ctenaphoras
(In phylum Coelenterata with Cnidarians but no longer classified as that
Give examples of Cnidarians.
(3 given examples in the slides)
Jellyfish, sea anemones, corals
Two forms of locomotion exhibited by Cnidarians.
(still and moveing)
Sessile and Free-swimming
What type of nutrition do they require?
(prey or predators)
Predators.
What type of organization do they have?
(Higher than porifera).
Tissue level organization
Skeleton may be made of what?
(3 things)
Hydrostatic, Calcium carbonate, chitin
What is the phlyum named after?
Its iconic cells cnidocytes or cnidae present in cnidocytes.
Habitat of cnidarians?
Marine & freshwater
Type of organization
Tissue level organisation
Type of symmetry for ctenophores?
Like ctenophores: Radial or biradial
Type of gut for ctenophores and cnidarians?
(complete or incomplete?)
Incomplete gut
Where does extracellular digestion occur?
Gastrocavity or gastrodermal cells
Two sense organs present in cnidaria
Statocyst and ocelli
What type of coelom?
Acoelomate (do not have one)
What are to two life forms of cnidarians?
Polyp and medusa
Describe the polyp form.
Tubular, sessile, mouth leads to gastrovascular cavity, aboral end attach to substrate. Asexual reproduction, polymorphism , modular colonies.
How do polyps reproduce asexually?
Budding, fission and pedal laceration (fragmentation)
Describe the medusa form.
- Tetramerous
- Bell shape
- Mouth on concave side of the bell.
- Tentacles on the rim of the medusa.
- Free-swimming
What sensory structures are present in the medusae form?
- Statocyst
- Ocelli
How many germ layers do the mesdusa have?
- They are diploblastic.
(epidermis & gastrodermis) middle is mesoglea.
What are the 5 cells of Cnidarians ?
- Epitheliomuscular
- Interstitial
- Mucus gland cells
- Cnidocytes
- Sensory cells.
What is the purpose of the epitheliomuscular cell?
Affect muscular contraction of the outter epidermis.
What causes contractions in the cnidaria outer epidermal cells?
Myofibrils
What is the purpose of mesoglea ?
Jelly like, thickness vary with different cnidaria,** supports and acts as an elastic skeletal.**
Nerve Net
(location, what causes nerve action potential, what is it?).
- Is a diffused nervous system.
- located at the base of the epidermis and gastrodermis.
- Nerve action potentials transmited by neurotransmitters.
Explain the life cycle of a typical Cnidarian
Zygote developed into a planulae -> settles on a substrate -> planulae forms into polyp-> asexually form more polyps + medusae -> reproduce sexually.
Name the 4 classes of the Cnidaria
Hydrozoa
Scyphozoa
Cubozoa
Anthozoa
Example of the hydrozoa
Fire corals
Key features of the Hydrozoa
- Velum present
- 4 radial canals
- Acellular mesoglea
- Hydromedusae
- Polyp conspicous
- Manbrium in which the mouth is at the end.
- Colonial
- Marine
- Gametes release outside the body
Example of the Scyphozoa
Upsidedown jelly fish
Key features of the scyphozoa
- Bell margin scalloped
- Have lappets
- Lappets have sensory structure called Rhopalium
- Free swiming
- Medusae dominant
- Tentacles on subumbrella side
- Mouth leads to stomach
- nerve net
- No velum
- distinct sexes
- reproduce sexually
*
Describe cubozoa
- Strong swimmer
- Medusoid stage dominant
- Polyp is inconspicuous or absent
- tentacles at corner at the Pedalium
- 24 well developed eyes
- Have rhopalia
- Margin not scalloped
- Boxed shaped in transverse section.
Example of cubozoa
Box jellyfish
Key characteristics of anthozoa
- Medusa stage absent
- coral polyp
- biradial symmetric
- polyp more complex and larger than other stages.
- have amoeboid mesenchyme cells
- Mouth leads to Pharynx
- Solitary or colonial
- marine
- have 3 subclases: main subclasses are Hexacorallia and Octocorallia.
Which subclass covers hard corals ?
Hexacorallia
Which subclass of anthozoa covers soft corals?
Ocotocorallia
Difference between hexacorallia and Octocorallia.
Hexamerous vs octomerous
simpler tentacles vs pinnate tentacles
About scleractinian
- Have cups formed from Calcium carbonate named Calyx.
- Have cups where polyp can retract to.
- Skeleton secreted at base of polyp.
- Gastrovascular connected by coensarc.
- Sclerosepta sticks in true septa.
- Skeleton made of aragonite.
An example of the Scleractinian
Brain corals.
Describe octocorallia
- Solenia (gastrovascular cavity communicates through it)
- 8 pinnate tentacles.
- 8 unpaired septa.
- cellular thick mesoglea
- Horny protein or fused spicules endoskeleton
- Cnidocytes in both layers.
- colonial
- Septa goes into the upper body.
What is a key feature of cnidocytes?
Cnidae or nematocytes.
Prey-capture in Cnidarian
Cnidocil triggered from hydrostactic pressure (high tensional and osmotic pressure or forces) and the hollow barbed or spiculated threads are released and they sting prey, release toxins and immobolize them.
