Almost all species in phylum ctenophora are hermaphrodites, meaning that they have both male and female functioning sexual organs. (One exception is the genus Ocryopsis, which is either male or female.) Both eggs and sperm are released into the water; fertilization takes place externally. Most species are self-fertile. Once a ctenophore is released from the egg, it all of the structures of an adult ctenophore are present, but on a smaller scale.

Evolutionary History:

Structurally, ctenophores are a very simple phylum of animals. Very few fossils of ctenophores have been found, because their bodies are very soft and gelatinous. The fossils that are available suggest that phylum ctenophora is at least 400 million years old.
Scientists have found shocking new evidence that suggests that the first animal on earth was a ctenophore, and not the less complex sponge, as was previously thought. Using molecular phylogenetics (DNA, RNA, biochemical analysis), scientists have determined that ctenophores were the first animals to diverge. These results are significant, because they prove that evolution is not necessarily a progression towards increased complexity.


Ctenophores can occupy the near surface of the water, and some species are capable of diving deeper into the water they inhabit. they consume millions of small organisms and are actually regulating the overpopulation of these species. In 1980, the North Atlantic ctenophore Beroe ovata was accidentally introduced to the Black Sea and became an invasive species. For the most part, ctenophores are not a wide spread food source for other organisms because they have a low ratio of organic matter to salt and water. However, they are preyed upon by some jellyfish and turtles.