CTENOPHORA (comb jellies)

1. Exclusively marine
2. Biradial symmetry.
3. Hermaphroditic.
4. Aboral sense organ.
5. Pelagic.

Ctenophores are usually ovate or spheroidal in shape, but some species have a flat ribbon-like or disc-like form. They have an inner and outer layer of cells separated by mesoglea. The inner, or digestive layer, is a simple pouch. An oral-aboral axis is established by the mouth and an aboral sense organ. Ctenophores have comb-plates which are arranged logitudinally in eight meridonal rows. Each comb-plate consists of a partially fused row of cilia arranged like the teeth of a comb. These comb-plates are the locomotor organs. Ctenophores have two tentacles armed with colloblasts which stick to and entangle prey. The Ctenophores are hermaphroditic. Reproduction is mostly sexual, with both the eggs and sperm being released into the water column where fertilization takes place.

• There are less than a hundred known species of Ctenophores.
• Ctenophores are related to the Cnidaria, but lack the nematocysts.
• During the day, they are frequently seen as iridescent ball-like forms rolling in the waves, and at night they are seen as brightly phosphorescent orbs.
• Ctenophores are found in the marine waters between Greenland and Long Island, off the Pacific coast of North America and in the South Pacific.

1. Braun, Frank A. Jr. 1967. Selected Inverebrate Types. New York: Wiley and Sons, Inc.
2. Carter, G. S. 1965. General Zoology of the Invertebrates. Seattle: University of Washington Press.
3. Goodnight, Clarence J. and Marie L. 1964. General Zoology. New York: Reinhold Publishing Corporation.
4. Wells, Martin. 1968. Lower Animals. New York: McGraw-Hill Book Company.

Laboratory Work on Ctenophora

Classification

• Class Tentaculata--possess tentacles
  • Order Cydippida--sea walnuts
  • Order Platyctenida--shallow water, tropics and arctic
  • Order Lobata--planktonic
  • Order Cestida--pelagic
  • Order Ganeshida--pelagic
  • Order Thalassocalycida--pelagic and fragile
• Class Nuda--lack tentacles
• Order Beroida--Beroe

Drawings:

Draw whole specimen. Show details of comb-row to indicate how organism uses cilia for locomotion

Specimens:

Pleurobrachia--Sea gooseberries. located in small vial