Lecture 8: Ctenophora

Question 1

Planktonic orders

Answer 1

Cydippida, lobata, beroida, cestida

Question 2

Benthic ctenophores

Answer 2

Platyctenida

Question 3

Ctenophores’ similarities to Cnidarians

Answer 3

1. No coelom
2. No nephridial excretory systems
3. No gonads
4. Pelagic
5. Predatory
6. Tentacles studded

Question 4

Ctenophore features

Answer 4

1. Cnidaria tentacles around mouth, ctenophore tentacles (2) in pair of deep sheath invaginations in mesogleal material, extensions of epidermis and mesoglea in tentacles (not gastro) with branches
2. Pharynx is broad flat sac, perpendicular to tentacle sheaths (Biradial symmetry)
3. Digestive tract: stomach branches from central gut out to periphery, but regular branching longitudinal main root for digested food materials to tentacles, BRAIN, and specialized cells
4. Ctenes (comb rows) - swimming organ, epidermal structure (8), ciliated with fused plates of plasma membrane

Question 5

Colloblast Cells

Answer 5

Surface of tentacles and around mouth, contains sticky mucus beneath plasma membrane, set off depending on “brain”

Question 6

Beroe (nuda)

Answer 6

No tentacles, develop comb rows along tubular body swim with mouth stitched together. No colloblasts but opens mouth rapidly for suction. Hardened cuticle over plasma membrane, hardened ciliary teeth.

Question 7

Striated Muscle

Answer 7

Epitheliomuscular cells from mesoderm

Contractile in parallel (latitudinal and radial fibers) form z bands

Directed contraction of motors in same direction

Question 8

Embryos of Ctenophores

Answer 8

No alteration of generations, determinate cleavage, endomesodermal muscle cells, no planula stage

Question 9

Ctenophores lack:

Answer 9

Hox genes, neurotransmitters, microRNA