Ctenophores

Ctenophora (/təˈnɒfərə/; singular: ctenophore /ˈtɛnəfɔːr, ˈtiːnə-/; from Ancient Greek κτείς (kteis) 'comb', and φέρω (pherō) 'to carry') comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming, and they are the largest animals to swim with the help of cilia. Tall nutritive cells that contain minerals inside vacuoles (internal compartments), germ cells that create eggs or sperm, and photocytes that emit bioluminescence make up the closer side. The side of the organ that is farthest away is covered in ciliated cells that move water through the canals and are broken up by ciliary rosettes, holes that link to the mesoglea and are encircled by double whorls of cilia.

Despite having a fragile, gelatinous body, ctenophores are thought to have existed as far back to the early Cambrian, or approximately 525 million years ago. These fossils are found in lagerstätten. on studies of molecular phylogenetics, the place of ctenophores on the "tree of life" is frequently disputed. According to the Ctenophora Sister Hypothesis, which is supported by other scientists, ctenophores began to emerge before sponges, which themselves first appeared before the division between cnidarians and bilaterians.

Their bodies are made up of a mass of jelly with an outer layer that is two cells thick and an inner cavity that is lined with another layer of jelly. The phylum contains a wide variety of body types, such as the large-mouthed beroids that feed on other ctenophores, the flat, typically combless platyctenids, and the egg-shaped cydippids with retractable tentacles that capture prey.

The exceptions are the juveniles of two species, who live as parasites on the salps that the adults of their species feed on. The majority of ctenophores are predators, consuming prey ranging in size from microscopic larvae & rotifers to the adults of small crustaceans.