Compiled by: Zoé Joly-Lopez, McGill University / STRI
The ctenophores are marine invertebrates that constitute the phylum Ctenophora. They are commonly known as comb jellies, although other forms of ctenophores have other names, such as sea gooseberries, cat’s eyes and sea walnuts. Although they must have existed for a very long time, they were first recorded in 1671, and later classified by the taxonomist Carl von Linné. Almost 150 species have been described so far.
Originally, comb jellies were classified with the phylum Cnidaria, that includes jellyfish, but they were recently separated from that group because they were found to lack stinging cells. Comb jellies got their name after the eight vertical comb rows of fused cilia arranged along the sides of the animal. They use these cilia as a motion mechanism in the water. Some ctenophores also possess two long retractable tentacles that move synchronously and enable them to catch preys, whereas others lack tentacles. Ctenophores are generally colorless and can vary in shape and size. They measure in average a couple of centimeters, but some species (such as Venus’s girdle) can measure up to 1 meter long.
They are hermaphroditic and in most cases, the male and female gametes are released into the water, where both fertilization and embryonic development will take place.
As other interesting characteristics, many ctenophores are bioluminescent, which means that they are able to produce and emit light, and they are also capable of extreme regeneration of parts of their body: if half of their body gets destroyed, the other half will be able to rebuilt it.
Ctenophores are predators and eat plankton, worms, larvae, crustaceans, cnidaria and also sometimes other ctenophores. Only one genus (Lampea) has shown to be parasitic. They can be encountered in diverse habitats all over the world, from deep sea to shallow estuarine waters.