Lecture 5: Porifera

Question 1

Three classes within Porifera

Answer 1

Calcarea
Demospongiae
Hexactinellida

Question 2

Sponges lack:

Answer 2

Head, mouth, gut, coelom, muscles, nervous system, digestive excretory circulatory organs, gonads

Question 3

Animal traits in Sponges

Answer 3

Collagen type 4
Animal embryonic development
Acetylcholine-cholinesterase comminication
Septate/ tight junctions between some cells
Epithelia and basal lamina in some tissues of some taxa

Question 4

Distinctive Sponge Features in body plan

Answer 4

Motility of most cells
De-differentiation of many cell types
Great functional and ecological plasticity

Question 5

3 layers of Sponges

Answer 5

Pinacoderm (outer), Mesohyl (middle), Choanoderm (inner)

Question 6

Organelles in the Mesohyl

Answer 6

Archaeocytes (undifferentiated stem cells that vacuum)
Lophocytes (secrete organic fibrillar collagen)
Sclerocytes (with spicules)

Question 7

Organelles in the Choanoderm

Answer 7

Choanocytes (generate water current and food particle capture, apical to spongocoel)

Question 8

Organelles in Pinacoderm

Answer 8

Pinacocytes and Porocytes

Question 9

3 Sponge grades of construction

Answer 9

1. Asconoid
2. Syconoid (increase SA and collar cells for feeding and water flow)
3. Leuconoid (large number of small chambers layered in collar cells, choanocyte chambers embedded in mesohyl. Incurrent ostia canal, outcurrent osculum canal)

Question 10

Sponge grades differ among classes: Demospongiae

Answer 10

All leukonoid

Skeleton: spongin, siliceous spicules, both monaxon and tetraxon megascleres

Question 11

Sponge grades differ among classes: Calcarea

Answer 11

All three grades, the only class with asconoid
Skeleton: calcium carbonate spicules

Question 12

Sponge grades differ among classes: Hexactinellida

Answer 12

Generally syconoid

Skeleton: siliceous hexagonal megascleres, syncytial pinacoderm and choanoderm

Question 13

Spongin fibers are

Answer 13

Polymerized collagen

Question 14

Sponge Sex Process

Answer 14

1. Eggs develop from archeocytes in mesohyl and wait for Mr. Right
2. Sperm arise from collar cells (turn to gametes directly)
3. Female actors take up sperm by suspension feeding
4. Collar cells capture sperm, engulf, put in vacuols and hands to oocyte for fertilization in mesohyl

Question 15

Placozoa classes and layers

Answer 15

1. Trichoplax
2. Hoilungia
3. Polyplacotoma

2 epithelial layers, sister group to planulozoa and cnidarians