Module 3.12 Porifera Classes

Question 1

4 classes of Porifera

Answer 1

1. Calcispongiae
2. Desmospongiae
3. Hexactinellida
4. Homoscleromorpha

Question 2

Calcispongiae spicules

Answer 2

Calcium carbonate

Question 3

Desmospongiae spicules

Answer 3

Silica, spongin, and some chitin
Not six-rayed
Organized around axial filament

Question 4

Homoscleromorpha spicules

Answer 4

Lacking

Question 5

Hexactinellida spicules

Answer 5

Silica (& chitin)
Six-rayed
Organized around axial filament

Question 6

Calcispongiae characteristics

Answer 6

• Marine
• Calcium carbonate spicules
• Tubular / Vase-shaped
• 3 types of canal systems / body constructions

Question 7

Homoscleromorpha characteristics

Answer 7

• Lacking spicules (or if present = silicon)
• Have distinct basal membrane, but no desmosomes

Question 8

Desmiospongiae characteristics

Answer 8

• Largest class of Porifera
• Spicules are never calcareous,
  instead, are composed of silica,
  spongin, and some chitin.
• All are in leuconoid construction.
• Shows variety of forms:
  encrusting, erect, branching,
  multilobed, spherical, or tubular

Question 9

Hexactinellida characteristics

Answer 9

• Spicules are silicon and chitin
• Syconoid or leuconoid
  construction
• The choanocyte tissues are
  syncytial~ many nuclei within a
  single plasma membrane
• Lacks pinacoderm

Question 10

Name the 2 classes of Porifera with six-rayed spicules

Answer 10

Hexactinellida & Desmiospongiae

Question 11

Why are Sclerosponges no longer a class of Porifera?

Answer 11

They are POLYPHYLETIC ergo they share two or more common ancestors, but do not share the most common recent ancestor

Question 12

Spongia, Clathria, Spongilla

Answer 12

Demospongiae

Question 13

Leucosolenia, Grantia, Sycon

Answer 13

Calcispongiae/Calcarea

Question 14

Euplectella, Hyalonema

Answer 14

Hexactinellida