CNIDARIA

Question 1

General Characteristics of Cnidaria

Answer 1

-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

Question 2

What are the 2 subphyla we focused on?

Answer 2

Anthozoa
Medusozoa

Question 3

What types of animals are in Subphylum Anthozoa?

Answer 3

anemones, sea pens, gorgonians, corals

Question 4

What types of animals are in Subphylum Medusozoa?

Answer 4

jellyfish, hydrozoans

Question 5

Subclasses of Anthozoa?

Answer 5

Subclass Octocorallia (sea whips, sea fans, sea pens, soft corals)
Subclass Hexacorallia (anemones, stony corals)

Question 6

Classes of Medusozoa?

Answer 6

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)

Question 7

Diplobastic or Triploblastic?

Answer 7

Diploblastic

Question 8

Radial or Bilateral Symm?

Answer 8

Radial

Question 9

Characteristics of a polyp’s body layers?

Answer 9

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.

Question 10

Hypostome/manubrium/oral disc

Answer 10

elevated structure where the mouth rests

Mouth of anthozoans is on a flat oral disc
Mouth of hydrozoans on a manubrium or hypostome.

Question 11

Are they solitary, colonial, or can they be both?

Answer 11

Both

Question 12

What is the coelenteron?

Answer 12

Their gastrovascular cavity. Serves for circulation and digestion/distribution of food

Question 13

What are Acontia

Answer 13

long threads derived from mesenteries that hang free in the gastrovascular cavity. Function in defense and feeding
(in some sea anemones)

Question 14

What are the three zooids (polyps) present in a colonial hydrozoan?

Answer 14

gastrozooid (feeding polyps)
dactylozooid (defensive polyps)
gonozooid (reproductive polyps)

Question 15

What is the special structure of the bell margin in hydromedusae?

Answer 15

A velum

Question 16

What type of support do polyps have? Are these considered soft or hard support?

Answer 16

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

Question 17

What type of support do medusa have? Are these considered soft or hard support?

Answer 17

Medusae only have soft support- Thin to thick mesoglea

Question 18

What is a thecate hydroid?

Answer 18

Hydroids whose perisarc extends around each hydranth and gonozooid

Question 19

What is an athecate hydroid?

Answer 19

hydroids whose perisarc does not extend around each of the zooids

Question 20

How do polyps move?

Answer 20

Muscles modified gastrodermis and ectodermis.
Longitudinal and circular muscles.
Hydrostatic skeleton.

Methods:
Creeping on pedal disc
Cartwheels
Swimming

Question 21

How do medusae move?

Answer 21

Coronal muscles contract and water pushed out of subumbrella

Method: Swimming (jet propulsion)

Question 22

What are the 3 types of cnidocytes?
How are they triggered?

Answer 22

Three types:
Nematocysts (toxic)
Spirocysts (adhesive)
Ptychocysts (form a tube for the animal to reside in)

Triggered by a mechanoreceptor

Question 23

How do they feed themselves?
How does digestion happen?

Answer 23

Prey subdued by cnidocytes and carried to gastrovascular cavity by tentacles.
Digestion begins extracellularly and continues with intracellular digestion.

Question 24

How do cnidarians reproduce asexually?

Answer 24

Budding
Fission
Pedal disc fracture

Question 25

How do cnidarians reproduce sexually?

Answer 25

Alternation of generations (except anthozoans who lack a medusa stage)

Gametes released into the water. Fertilization usually external