An Introduction to Zoology
Chapter 10: The Radiata: Phylum Ctenophora:
The Phylum Ctenophora:
In the previous chapter, we discussed the Phylum Cnidaria, one of the two phyla of
diploblastic,
radially-symmetrical animals. The other radiate phylum is the Phylum Ctenophora (from the Greek “ktenos,” meaning “comb,” and “phora,” meaning “bearing”). Ctenophorans are commonly known as “sea walnuts” or “comb jellies.” All known ctenophoran species are marine, and ctenophorans are the largest organisms that use cilia as their main source of propulsion.
Ctenophorans are fragile, beautiful creatures. In most species, the body is transparent and looks like glass. The comb rows create iridescent patterns as they beat. In addition, many species are
bioluminescent, and can produce spectacular light displays. One of the most memorable experiences I’ve ever had was a night of sitting on a dock and watching comb jellies swimming in the water below, their comb plates glowing brightly. It was on an Ecology class trip, and several students desperately wanted to catch some of them to take home. I had a hard time convincing them that the fragile creatures would never survive, and so should be left alone.
As you might expect, the ctenophorans and the cnidarians have a lot in common. The ctenophorans are a much smaller phylum, however, and are much less familiar to most people. I suspect that the average person, upon seeing a ctenophoran, would think that it was a kind of cnidarian. Nonetheless, despite the superficial similarities between ctenophorans and cnidarians, there are a number of important differences between them.
Introduction
Linear Mode
