Download Cnidaria lab_2015 7483KB Apr 16 2015 11:39:46 AM

INTRO TO CNIDARIA
FISH310
Spring 2015
Defining Characteristics
• Cnidea (nematocysts)
• Radial symmetry (mostly!)
• Planula larvae - free-swimming, flattened,
ciliated, bilaterally symmetric larva
• Only 2 tissue layers of tissue (epidermis and
gastrodermis) with mesoglea in-between
• A single opening to the digestive system
• Tentacles around the mouth
• Exclusively aquatic, mostly marine
Polyp or Medusa body plans
with an oral-aboral axis
Cnidea (nettle/stinging thread)
• Multiple Functions:
– food collection, defense and locomotion.
• Can be specialized for wrapping around small objects,
sticking to surfaces, penetrating surfaces, or secreting
proteinaceous toxins.
• Cells that contain cnidea are called cnidoblasts
Nematocysts!
Nematocyst animation!
Nematocysts firing under a microscope!
• Discharge triggered by chemical/physical stimulation of modified
cilia (cnidocil). Takes only 3 ms!
• Primary force behind expulsion is osmotic pressure, although the
exact mechanism remains uncertain. Different types of cnidea may
operate by different mechanisms.
Major classes of Cnidaria
• Hydrozoa
– Hydra
– Portuguese man o' war
• Anthozoa
– sea anemones
– Corals
– sea pens
• Scyphozoa
– jellyfish
• Cubozoa
– Box jellies
Phylogenetic tree
• Main diveragence is between the Anthozoa and
Medusozoa
• Major lineages diveraged over half a billion years
ago.
http://biorxiv.org/content/early/2015/04/06/017632
Class:
Hydrozoa
• ~3,000 mostly marine
species
• Typically small, with
polyp and medusa
stage
• Members include:
– Hydroida
– Siphonophora
– Hydrocorallina
• Gastrodermis lacks
cnidea
• No cells in mesoglea
Portuguese Man
O’War:
not a “true” jellyfish
http://video.nationalgeographic.com/video/manowar_portuguese
Hydrozoans – In lab
• Examine colonial polyp
• Identify species using field guide
• Note colony form, polymorphism, life history
Class:
Anthozoa
• ~7,500 species
• Lack a medusa
stage
• Some species
have algal
symbionts
• Members Include
– Corals
– anemones
– Sea pens
Coral Reefs
See a cool movie on Anemones
Anthozoan
Evolution!
Anthozoa – In lab
• Today we will look at the external and internal
anatomy of a sea anemone
• Dissection:
– Metridium senile.
• Body plan
• Acontia
• Live speciemens
– Anthopleura elegantissima
• Algal symbionts
• Acrorhagi
Acontia
Let’s look at the acontia of
our local Metridium spp.
• Thin filaments extending from the middle
lobe of the mesenteries loaded with
nematocysts
•Extend outside body through small pores in
body wall
• Function in offense, defense, & digestion
Sea Anemones at War!
Acrorhagi
Today we will see these defensive
structures in our Anthopleura dissections
•Hollow spherical protrusions covered
with potent nematocyts
•Function in defending territory
Algal Symbionts
Check out the algal symbionts in our
local anemone: Anthopleura
elegantissima
Zooxanthellae – dinoflagellate
of the genus Symbiodinium
Zoochlorellae- single celled green
algae
Class:
Scyphozoa
• ~ 200 species
• True jellyfish
• Mainly medusoid
Scyphozoan Sensory Structures
Sensory organs include:
– Statocysts – balance organ
– Ocelli – light receptor
Statocysts and ocelli are
contained within structures
called rhopalia
Cubozoans also have highly
advanced sensory structures
(lensed eyes)
Life cycle of Aurelia aurita (moon jellyfish)
• A Mature female medusa
(30 cm in diameter)
carrying planula larvae
(red arrow) in brood
pouches in the oral arms.
• B released, freeswimming planulae (0.20.3 mm).
• C Polyp (1-3mm).
• D Beginning strobilation.
• E Advanced strobilation.
• F Young Ephyra (3-5mm).
• G Ephyra, 4 weeks after
release (8-10mm).
The Moon Jelly Life Cycle
Making a Wet Mount
• 1. Gather a thin slice/piece of whatever your specimen is.
If your specimen is too thick, the coverslip will wobble on
top of the sample like a see-saw and you will not be able
to view it under high power
• 2. Place ONE drop of water directly over the specimen. If
you put too much water, the coverslip will float on top of
the water, making it hard to draw the specimen (Plus too
much water is messy)
• 3. Place the coverslip at a 45 degree angle with one edge
touching the water drop and then gently let go.
Performed correctly the coverslip will perfectly fall over
the specimen. Try to avoid air bubbles.
Next lab: Resilience project
• Assigned readings
• Discussion board posts
• group project
• Thursday:
– Steven Roberts SAFS seminar
• DNA methylation in marine invertebrates
• 4pm
Lab review
CLEAN UP
• Thoroughly wash all dissection tools and trays
• Dispose of animal remains in biohazard
container in the fume hood
• Rinse slides & toss coverslips in sharps
container
• Make sure your scopes are clean and turned
off
• Present your worksheet
Unused
Feeding
Anemone Feeding Video
Hydra Feeding Video
Jellyfish Feeding
Anemone Feeding on Jellyfish
LET’S FIRE SOME!