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Ctenophora Eschscholtz, 1829 Comb jellies; Sea walnuts

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Higher taxa:  Life   Ctenophora   Global map IDnature guides: Groups_other, North_American_Invasives Overview Phylogeny Links to other sites References Acknowledgements We parsed the following live from the Web into this page. Such content is managed by its original site and not cached on Discover Life. Please send feedback and corrections directly to the source. See original regarding copyrights and terms of use. Image, Beroe cucumis, Jim Mastro, University of California San Diego Image, Adults, E. Prosser Armstrong, National Academy of Sciences of Ukraine Institute of Biology of the Southern Seas Marine and Environmental Education and Research, Inc. University of California, Berkeley

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© Public Domain Ctenophore

Kinds

Bathocyroidae Bathyctenidae Beroidae Bolinopsidae Cestidae Coeloplanidae Cryptocodidae Cryptolobatidae Ctenellidae Ctenoplanidae Dryodoridae Euchloridae Euplokamidae Euplokamididae Eurhamphaeidae Ganeshidae Haeckeliidae Kiyohimeidae Lampeidae Lampoctenidae Leucotheidae Lobatolampeidae Lyroctenidae Lyrotctenidae Mertensiidae Mnemiidae Ocyropsidae Platyctenidae Pleurobrachiidae -- Sea gooseberries Savangiidae Thalassocalycidae Tjalfiellidae

Overview

Ctenophores are marine animals that possess eight rows of cilia that they use in locomotion. Light scatters off these rows of cilia, often causing a "rainbow-effect" to radiate from ctenophores. Although this phenomena is not actually bioluminesence, most ctenophores are bioluminescent in addition to emitting the rainbow of light. Ctenophores are carnivores that feed mostly on zooplankton, with a few larger species feeding on invertebrate larvae and small crustaceans. They use tentacles with specialized sticky cells to capture their prey and bring it to the mouth. It is in this manner that ctenophores are capable of wiping out entire ecosystems because of their carnivorous ways. As voracious predators, ctenophores are capable of overpopulating ecosystems, ravaging the food supply, and thus wiping out indigenous species of the area. All ctenophores are hermaphroditic, releasing both eggs and sperm into the water as they swim. The sperm find the eggs in the water, and fertilization then takes place.

Phylogeny

Tree of Life web project Nuda Beroidae Thalassocalycidae Tentaculata Cestidae Bathyctenidae Dryodoridae Haeckeliidae Lampeidae Mertensiidae Pleurobrachiidae Bathocyroidae Bolinopsidae Eurhamphaeidae Mnemiidae Ocyropsidae Lyrotctenidae Platyctenidae Tjalfiellidae

Links to other sites

Tree of life -- Phylogeny of ctenophores. University of Washington -- General information on ctenophores. Animal diversity web -- Information on ctenophores including classification, pictures, and specimens.

Acknowledgements

Sam Cincotta, University of Georgia, Athens I thank John Pickering for his assistance with the development of this page.

Following modified from Marine and Environmental Education and Research, Inc.

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MEER home Marine biology home Table of Contents Index References Links Phylum Ctenophora Ctenophore, from Fitzinger, 1862. Because Ctenophores have transparent gelatinous bodies that are biradially symmetrical, and commonly lead a planktonic lifestyle, they superficially resemble pelagic Cnidarians such as jellyfish . However, they have many features that are distinctly different from the Cnidarians , such as a mesenchymal musculature, a more developed digestive system, monomorphic life history (only one body type), a cydippid larval stage, and the fact that they are never colonial. Ctenophores move through the water by the coordinated beating of cilia on eight rows of ciliated "combs" (known as ctenes ). This is in contrast to Cnidarians , where the motile medusoid form moves through the water by muscular contractions and pulsing of the medusa 's bell . All Ctenophores are marine, unlike Cnidarians which have some freshwater forms. Ctenophores can be found in all seas and oceans, and are occasionally extremely abundant and a dominant organism in some plankton communities. There are only about 100 extant species of Ctenophores , which can be divided into just two classes, Class Nuda and Class Tentaculata . As their names suggest, members of the class Nuda have no tentacles, whereas those of the class Tentaculata do. They may be found in a wide variety of sizes and shapes, - from spherical to ribbonlike, and from less than 1 cm. diameter to over one meter in length for some ribbonlike forms. They are usually planktonic , living in waters from the surface to as deep as 3,000 meters, and a few species may even be found crawling about on the bottom. Ctenophore, modified from various sources Pleurobrachia sp. from BIODIDAC, Univ. Ottawa The general Characteristics of the Phylum Ctenophora are: Biradially symmetrical, with an oral - aboral body axis . Eight rows of ciliated "combs" or ctenes , controlled by an apical sense organ at the aboral pole. Incomplete gut (mouth but no anus ). No excretory, respiratory, or circulatory systems. Diploblastic , with ectoderm and entoderm , and a cellular mesenchyme , which gives, rise to the musculature (some researchers feel that Ctenophores are triploblastic , with a true mesoderm ). Adhesive structures called coloblasts (but no cnidoblasts or stinging cells as in Cnidaria ). A diffuse nervous system consists of a nerve net, somewhat more specialized than that found in the Cnidaria . A cydippid larval stage, monomorphic life cycle, never with a sessile or benthic stage. REFERENCES Barnes, 1980 Brusca & Brusca, 1990 Barnes, Calow, and Olive, 1993 Meglitsch & Schram, 1991 Top of Page Following modified from University of California, Berkeley    Top | See original Introduction to Ctenophora Ctenophores (Greek for "comb-bearers") have eight "comb rows" of fused cilia arranged along the sides of the animal, clearly visible along the red lines in these pictures. These cilia beat synchronously and propel ctenophores through the water. Some species move with a flapping motion of their lobes or undulations of the body. Many ctenophores have two long tentacles, but some lack tentacles completely. Ctenophores, variously known as comb jellies, sea gooseberries, sea walnuts, or Venus's girdles, are voracious predators. Unlike cnidarians , with which they share several superficial similarities, they lack stinging cells. Instead, in order to capture prey, ctenophores possess sticky cells called colloblasts. In a few species, special cilia in the mouth are used for biting gelatinous prey. The phylogenetic position of ctenophores has been, and still is, in dispute. Ctenophores have a pair of anal pores, which have sometimes been interpreted as homologous with the anus of bilaterian animals (worms, humans, snails, fish, etc.). Furthermore, they possess a third tissue layer between the endoderm and ectoderm, another characteristic reminiscent of the Bilateria. However, molecular data has contradicted this view, although only weakly. Therefore, this is an active area of research. Although most ctenophores swim, one group creeps along the bottom of the seas. Most of these species live on other animals, for instance with echinoderms , sponges , or benthic cnidarians . Many ctenophores, like various other planktonic organisms, are bioluminescent , able to give off light. Until fairly recently, no fossil ctenophores were known. Like most pelagic cnidarians, the bodies of ctenophores are made up mostly of water, and the chances of leaving a recognizable fossil are very slim. Two species of fossil ctenophore have now been found in the Late Devonian , in the famous Hunsrückscheifer slates of southern Germany (Stanley and Stürmer, 1983, 1987). Both owe their preservation to rapid precipitation of pyrite in the tissues, and both are quite similar to living ctenophores in the order Cydippida (the "sea gooseberries.") Other ctenophore-like forms have been found in the Cambrian -age Burgess Shale of the Canadian Rocky Mountains and Chengjiang Formation of Southern China. These forms differ from living ctenophores in several ways, thus obscuring their phylogenetic affinities. Little is currently known about the basic biology of most ctenophores; indeed, the individual in these pictures has not even yet been formally described and named, despite being large, spectacularly colored, and common. These photographs were made available to the UCMP by Underwater World , Queensland, Australia. View the World List of Ctenophora species , arranged in a taxonomic classification, or visit the page on Ctenophora at the Tree of Life. Sources: Stanley, G.D., and W. Stürmer. 1983. The first fossil ctenophore from the Lower Devonian of West Germany. Nature 303:518-520. Stanley, G.D., and W. Stürmer. 1989. A new fossil ctenophore discovered by X-rays. Nature 327:61-63. Updated: 2009-11-22 00:33:48 gmt Discover Life | Top © Designed by The Polistes Corporation