Lecture 6: Cnidaria (Anthozoa)

Question 1

Epithelia of Cnidaria

Answer 1

Continuous sheets of cells, basal apical polarity, secreted acellular basal lamina, intercellular junctions

Question 2

Classes of Cnidaria

Answer 2

Scyphozoa
Hydrozoa
Anthozoa

Question 3

Features of Anthozoa

Answer 3

Body = polyp, radial symmetry, ectoderm embryonic germ layer on outside, gastrodermal layer on inside from endodermic germ layer

Question 4

Myoepithelial cells of Anthozoans

Answer 4

Produce actin, release secretions

- Actin and myosin elements both parallel and perpendicular to acis and around circumference

Question 5

Gland cells of Anthozoans

Answer 5

Gastroderm gland cells secrete mucus and enzymes;

Epidermal gland cells secrete mucus, chitin, carbonate (hardened material that forms a kind of exoskeleton)

Question 6

Nerve cells of Anthozoans

Answer 6

Intracellular chemical communication over synapses, each nerve cell only propogates a reaction in one direction, but many cnidarians can send action potentials in both directions

Question 7

Interstitial cells of Anthozoans

Answer 7

Capable of moving and differentiation into gametes and other needed cells

Question 8

Cnidocytes in Anthozoans

Answer 8

Gastrodermal cnidocyte in Scyphozoans, Cubozoans and Anthozoans

Epidermal cnidocytes in ALL classes of cnidarians

Question 9

4 types of Cnidocytes

Answer 9

Volvent (attach to substrate)
Defendant and penetrant (loaded with neurotoxins)
Adherent

Question 10

Mesoglea in Anthozoans

Answer 10

Water and carbonate molecules, not cellular

Question 11

Skeleton contains…

Answer 11

1. Chitin = keratinized polysaccharides
2. Hard organic matrix (soft corals and gorgonians)
3. Calcium carbonate (millesporinga, stylasterina, helioporacea)

Question 12

Some specialized Anthozoan Anatomy: Septum

Answer 12

Creates small cascular spaces where prey can be tucked in

Gastrovascular epithelium develops thickened patches of myoepithelial cells parallel to acis becoming retractor muscles

Question 13

Some specialized Anthozoan Anatomy: Acontia

Answer 13

Extension of septa as defensive structure; contractile cells and cnidocytes in pores

Question 14

Some specialized Anthozoan Anatomy: Acrorhagi

Answer 14

Inflatable patches of epidermis underneath tentacles with high concentrations of nematocysts, loosely attached to basal lamina and inflated by sea water

Question 15

Simplified Anthozoan Sex

Answer 15

Gonads from interstitial cells in gastrodermis; eggs and sperm exit mouth

Females hold eggs in gastrointestinal spaces to wait for sperm

Question 16

Gastrula to Planula

Answer 16

2 epithelial layers are formed in embryonic development:

Ectodermal cells: skin, neurons, sensory structures
Endodermal cells: gut, digestive organs and gametes

Question 17

Anthozoa 3 types

Answer 17

Soft corals: octocorals
Anemones: hexacorals (actinaria)
Scleractinians: hexacorals (scleractinia)

Question 18

Hermatypic Corals

Answer 18

Scleractinia
Reef forming
High rates of metabolism, growth and asexual budding
Zooxanthellae as symbiont dinoflagellates
Epidermal cells absorb calcium and HCO, calcium crystallizes while releasing water and CO2