Phylum Ctenophora

General characteristics

• 1) Biradial symmetry in most spp.
• 2) Ellipsoidal body shape
• 3) Mostly triploblastic
• 4) Only one sp. having cnidocytes w/ nematocysts; All spp. have coloblasts = adhesive cells.
• 5) GVC
• 6) Statocyst sense organs : controlling equilibrium.
• 7) No polymorphism.
• 8) Reproduction sexually in monoecious individuals (both male and female sex cells produced by some individuals.
• 9) Luminescence (biochemical light production process involving enzymatic hydrolysis of ATP).

Comparison with Cnidaria

• 1) “Radial” symmetry
• 2) True aboral-oral axis (polarity)
• 3) Mesoglea in all spp.
• 4) GVC (not a true coelomic cavity)
• 5) Diffuse nervous “system”. Very simple and unspecialized.
• 6) Lack true organ systems.

Contrast of Phyla Cnidaria and Ctenophora

• 1) Except one species of Ctenophorans, no stinging cells.
• 2) Mesoglea of Ctenophoras more specialized than Cnidarians (mesenchyme layer which can develop into true muscle tissue)- much more specialized than in Cnidarians- allows more efficient swimming.
• 3) Specialized structures, which include comb plates (ciliated and work in locomotion and food capture and colloblasts.
• 4) Mosaic pattern of development whereby collection of genetically distinct groups of cells are located throughout body.
• 5) GVC specialization esp. near oral/anal opening; pharynx connecting w/ oral/anal opening w/ center of GVC.
• 6) No polymorphism.
• 7) No colonial forms (free-living and living independently)
• 8) Simple anal openings at anterior end of organism for excretion (primarily of soluble wastes).

Classification

• Class Tentaculata - most representative type of phylum Ctenophora. Have tentacles, used mainly for food capture, (ciliated and usually w/out cnidocytes). Comb plates - ciliated structures used mostly swimming.
• Class Nuda - lack tentacles.