Comb Jellies
Comb Jellies — Phylum Ctenophora
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Ctenophores (Ktenes="comb"; ophora="carrying") are small, free-swimming marine invertebrates. They are commonly known as comb jellies and are found in both coastal and oceanic waters. Four species commonly occur in the Canadian Arctic: Mertensia ovum, Pleurobrachia pileus, Bolinopsis infundibulum, and Beroe cucumis. Each of the first three species possesses a pair of tentacles used in capturing prey, such as copepods and amphipods, but Beroe cucumis lacks these tentacles since it preys upon other ctenophores – simply by ingesting them!
The general body shape of all ctenophores is spherical or ovoid and arctic species range in size from a pea to a golf ball. Ctenophores are composed of a thick, jelly-like substance full of fibres. Most comb jellies are transparent, but their bodies are brightened by eight rows of colour. These rows are composed of tiny hairs, called comb rows, and divide the body into equal sections, giving the group its common name. These combs also provide locomotory power for the animal.
Most ctenophores possess long, contractile tentacles that are covered with an adhesive mucous and are used to capture prey, particularly copepods, a group of small crustaceans that occurs in the water column. These prey, especially species of the copepod genus, Calanus, are high in fat, so arctic ctenophores are higher in fat than their temperate zone counterparts.
Some ctenophores are able to reproduce asexually - small fragments that break off an injured individual can regenerate into a complete adult. All ctenophores, however, are also capable of sexual reproduction. Individuals typically possess both male and female reproductive parts and shed their sex cells via their mouth into the water where fertilization takes place. A few species have internal fertilization, brooding their young before releasing them as free-swimming juveniles.
