CNIDARIA Flashcards
General Characteristics of Cnidaria
-Radial symmetry
-True tissues
-Diploblastic
-Capable of movement via epitheliomuscular cells
-Alternation of generation between polyp and medusa.
-Gastrovascular cavity
-Possess cnidocytes
-Most are predators
-Mostly marine, few freshwater
What are the 2 subphyla we focused on?
Anthozoa
Medusozoa
What types of animals are in Subphylum Anthozoa?
anemones, sea pens, gorgonians, corals
What types of animals are in Subphylum Medusozoa?
jellyfish, hydrozoans
Subclasses of Anthozoa?
Subclass Octocorallia (sea whips, sea fans, sea pens, soft corals)
Subclass Hexacorallia (anemones, stony corals)
Classes of Medusozoa?
Class Scyphozoa (jellyfish)
Class Hydrozoa (hydroids and fire corals
siphonophores (e.g., man-of-war)
by the wind sailors)
Class Cubozoa (sea wasps and box jellies)
Class Staurozoa (stauromedusae)
Diplobastic or Triploblastic?
Diploblastic
Radial or Bilateral Symm?
Radial
Characteristics of a polyp’s body layers?
Outer epidermis has epitheliomuscular cells, sensory cells, and cnidocytes.
Inner layer has gastrodermis (nutritive-muscular cells), which lines a coelenteron called a gastrovascular cavity.
Middle layer of mesoglea or mesenchyme.
Hypostome/manubrium/oral disc
elevated structure where the mouth rests
Mouth of anthozoans is on a flat oral disc
Mouth of hydrozoans on a manubrium or hypostome.
Are they solitary, colonial, or can they be both?
Both
What is the coelenteron?
Their gastrovascular cavity. Serves for circulation and digestion/distribution of food
What are Acontia
long threads derived from mesenteries that hang free in the gastrovascular cavity. Function in defense and feeding
(in some sea anemones)
What are the three zooids (polyps) present in a colonial hydrozoan?
gastrozooid (feeding polyps)
dactylozooid (defensive polyps)
gonozooid (reproductive polyps)
What is the special structure of the bell margin in hydromedusae?
A velum
What type of support do polyps have? Are these considered soft or hard support?
Soft support: Hydrostatic skeleton
Fibers in mesenchyme
Perisarc in hydrozoans
Hard support: Axial skeletons made of protein-mucopolysaccharide in anthozoans, such as gorgonians and sea pens
-Sclerocytes in mesenchyme of most octocorals secrete sclerites.
-Calcareous skeletons
What type of support do medusa have? Are these considered soft or hard support?
Medusae only have soft support- Thin to thick mesoglea
What is a thecate hydroid?
Hydroids whose perisarc extends around each hydranth and gonozooid
What is an athecate hydroid?
hydroids whose perisarc does not extend around each of the zooids
How do polyps move?
Muscles modified gastrodermis and ectodermis.
Longitudinal and circular muscles.
Hydrostatic skeleton.
Methods:
Creeping on pedal disc
Cartwheels
Swimming
How do medusae move?
Coronal muscles contract and water pushed out of subumbrella
Method: Swimming (jet propulsion)
What are the 3 types of cnidocytes?
How are they triggered?
Three types:
Nematocysts (toxic)
Spirocysts (adhesive)
Ptychocysts (form a tube for the animal to reside in)
Triggered by a mechanoreceptor
How do they feed themselves?
How does digestion happen?
Prey subdued by cnidocytes and carried to gastrovascular cavity by tentacles.
Digestion begins extracellularly and continues with intracellular digestion.
How do cnidarians reproduce asexually?
Budding
Fission
Pedal disc fracture
How do cnidarians reproduce sexually?
Alternation of generations (except anthozoans who lack a medusa stage)
Gametes released into the water. Fertilization usually external
