Cnidarians Flashcards
Classes of Cnidarians
C. Hydrozoa, C. Cubazoa, C. Scyphozoa, C. Anthozoa
Types of symmetry
Radial and Biradial
Tissues
Epidermis and Gastrodermis, and so they are diploblastic
They have polymorphisms.
Medusa(sexual) and Polyp (Asexual)
Between the epidermis and gastrodermis is?
Mesoglea
We have extracellular digestion.
There is a gastrovascular cavity that continues through the tentacle
Hydrostatic Skeleton
The skeleton is supported by water
There are nerves
There is a nerve net and nerves that make the myofibrils contract.
In the epidermis, what is the most common cell?
The epitheliomuscular cell. They have myofibrils that allow them to contract
What are interstitial cells and where are they found?
In the epidermis, and they give rise to other cells
Cnitocytes
The warrior of cells. If the cnidocil is triggered then the nematocyst is discharged. This occurs by a change in the cell’s permeability in water
What cells are found in the gastrodermis?
We have nutritive muscular cells. They are involved in digestion, enzyme secretion, and may take up nutrients.
We also have gland cells which produce mucus
Types of nematocysts
defendant, penetrant, adherant
Class Hydrozoa
Polyp is dominant. They may be solitary or live in groups (obelia). Medusa has a form of the velum that allows for better thrust
Genus Obelia
Obelia is colonial, Has a gastrozoid for eating and tentacles
Inside the polyp is the coenosarc
Gonozoid for asexual reproduction
For sexual, male and female have their own organs. They fertilize, the thing develops into a planula—> develops into new polyp. Alt of gen. Has polyphase perisarc, non living outer layer that is used for protection.
Physalia - Portuguese man of war
Has specialized polyp called pneumatophore which aids in floatation, Still has gastro/gonozoid, but now has specialized tentacles called dactylozooids used for fishing. Colony made up of many polyps
Gonionemus (Hydroid Medusa)
The medusa is the dominant form.
They have a statocyst that has a little grain of sand that aids in balance.
Food gets in through the mouth and into the manubrum –> gastrovascular cavity–> radial canals –> Ring Canal –> then tentacle.
Class Cubozoa
They have a reduced polyp. They are square shaped. They have a pedalium, fleshy part that supports the tentacle. Can herd their prey. The box jelly fish (Chironex fleckeri) can cause Irakandji syndrome
Class Scyphozoa
Medusa is the dominant form. these are our classic jelly fish. The life cycle can be seen through Aurelia.
Learn that
It has a rhopalium- that includes a statocyst, ocelli (eyes) and chemosensory pits. These are seen around the base of the jelly.
C. Anthozoa
These are just anemones and corals. They are polyp only and all marine. They give rise to coral reefs.
Specific Ex. is Metridium
Metridium
From class anthozoa, they have an oral disc and pharynx that is supported by primary septa. Secondary septa aid in absorbing nutrients
They have hydrostatic skeleton, redused mesoglea.
Around the oral groove is the siphonoglyph, used for bringing in water
Inside the gastrovascular cavity is the acontia which will shoot out in self defense
They have a symbiotic and mutualistic relationships
They have symbiotic algae called Zooxanthellae
Corals
Part of the anthozoa.
Stony Corals= zoantherian
Produce a lot of calcium carbonate with the aid of algae
With these, they have six septae,
they are hexacoralian
We also have octocorals which are out soft ones. They have 8 septa and they don’t have the hard calcium carbonate components. The polyps communicate through channel pathways called solenias.
Types of Reefs
Lagoon (No islands)
Barrier (runs parallel to the shore)
Fringing (No gap)
