Lecture 8: Ctenophora Flashcards
Planktonic orders
Cydippida, lobata, beroida, cestida
Benthic ctenophores
Platyctenida
Ctenophores’ similarities to Cnidarians
- No coelom
- No nephridial excretory systems
- No gonads
- Pelagic
- Predatory
- Tentacles studded
Ctenophore features
- 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
- Pharynx is broad flat sac, perpendicular to tentacle sheaths (Biradial symmetry)
- 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
- Ctenes (comb rows) - swimming organ, epidermal structure (8), ciliated with fused plates of plasma membrane
Colloblast Cells
Surface of tentacles and around mouth, contains sticky mucus beneath plasma membrane, set off depending on “brain”
Beroe (nuda)
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.
Striated Muscle
Epitheliomuscular cells from mesoderm
Contractile in parallel (latitudinal and radial fibers) form z bands
Directed contraction of motors in same direction
Embryos of Ctenophores
No alteration of generations, determinate cleavage, endomesodermal muscle cells, no planula stage
Ctenophores lack:
Hox genes, neurotransmitters, microRNA