How do ctenophora reproduce

Some argue that a new fossil from the Chengjiang fossil site in China and a peculiar fossil in the Burgess Shale are similar enough to jellyfish that they might be ancient comb jellies that had recently split from the jellyfish lineage.

Either way, there are still plenty of other questions to argue about, such as how long ago the two groups diverged, and even whether ctenophores might be the most ancient group of animals, diverging even earlier than sponges in the animal tree of life. These arguments continue because, as some of the simplest animals alive today, understanding their place in the tree of life helps people understand how all other animals—including people—evolved.

Whichever came first, comb jellies and jellyfish and other Cnidarians made an important step in evolutionary history: they are the earliest known animals to have organized tissues—their epidermis and gastrodermis—and a nervous system. They're also the first animals known to swim using muscles instead of drifting with the whims of the waves. The oldest ancestors of modern day jellies lived at least million years ago, and maybe as long as million years ago. That makes jellyfish three-times as old as the first dinosaurs!

Because jellies have no bones or other hard parts, finding jellyfish fossils is rare. But in , a group of scientists including Allen Collins from the Smithsonian National Museum of Natural History, discovered some beautifully-preserved jellyfish fossils buried in Utah from million years ago. From around the same period, scientists have also found well-preserved comb jelly fossils in the Burgess Shale.

Fossils described in from the Quingjiang site in southern China are some of the best preserved Cambrian fossils ever found, with the cilia and plates easily visible. Scientists are optimistic this discovery will help tease out the relationship between jellyfish and comb jellies.

Jellyfish and ctenophores are carnivorous, and will eat just about anything they run into! Most jellies primarily eat plankton, tiny organisms that drift along in the water, although larger ones may also eat crustaceans, fish and even other jellyfish and comb jellies. Some jellyfish sit upside down on the bottom and have symbiotic algae zooxanthellae in their tissues, which photosynthesize, and so get much of their energy the way plants do.

While their nematocysts and colloblasts do help them defend themselves, plenty of animals manage to catch and eat jellies: more than animal species are known to eat jellies, including fish, sea turtles, crustaceans, and even other jellyfish. Jellies are the favorite food of the ocean sunfish Mola mola and endangered leatherback turtle Dermochelys coriacea , which will migrate thousands of miles for the gelatinous delicacy. Young jellyfish are small enough to be part of the general zooplankton population and are eaten by many animals.

Humans also eat jellyfish: people have fished for jellies for at least years off the coast of China. Some , tons more than million pounds of jellyfish are caught each year by fisheries in 15 countries, and most are consumed in Southeast Asia. Eating jellyfish may become more common around the world as we overfish more preferable fish species. Jellyfish and ctenophores both have tentacles with specialized cells to capture prey: nematocysts and colloblasts, respectively. Jellyfishes' nematocysts are organelles within special cells cnidocytes that contain venom-bearing harpoons.

The cell is activated upon touch or chemical cue, causing the harpoon to shoot out of the cell and spear the prey or enemy, releasing toxin—a process that takes only nanoseconds. A small number of jellyfish are very toxic to humans, such as the box jellyfish Chironex fleckeri and Irukandji jellyfish Carukia barnesi , which can cause severe reactions and even death in some people.

Many comb jellies have colloblasts lining their tentacles, which work like nematocysts but release glue instead of venom. Upon touch, a spiral filament automatically bursts out of colloblast cells that releases the sticky glue. Once an item is stuck, the comb jelly reels in its tentacle and brings the food into its mouth.

One species of ctenophore Haeckelia rubra recycles nematocysts from hydrozoan jellyfish it consumes and uses these to stun and kill prey. Comb jellies come in many shapes and sizes , and so within the group there are many ways to feed.

The rounded and tentacled cydippids have branched tentacles lined with colloblasts that they use, in the traditional jelly style, like a fishing line to trap food and bring it to their mouths. The lobate ctenophores have two flattened lobes that reach below their mouths. Special cilia waving between the lobes generate a current to pull planktonic food between the lobes and into the jelly's mouth, allowing them to feed on plankton continuously.

They also use colloblast-lined tentacles to catch food. The tentacle-less beroids depend on their large mouths. Instead of catching food with colloblasts, they swallow their prey often other ctenophores! Inside their mouths they have small cilia that act as teeth, pulling food apart, which also direct the food into the comb jelly's gut.

Many jellyfish and comb jellies are able to produce light—an ability known as bioluminescence. They have proteins in some tissues that undergo a chemical reaction to produce blue or green light in response to stimuli such as touch. No one's quite sure why jellies bioluminesce, but it seems to be mainly a defense tactic. A bright enough flash could be enough to startle a predator—or to attract an even bigger predator to make the jelly's predator into prey.

Jellies have also adapted their body color to camouflage in the darkness. Most are nearly colorless and transparent, so they can be difficult for predators to see. However, some deep sea jellyfish and comb jellies are a bright red or orange color. Why would they be red instead of black to blend in with the dark water?

Red cannot be seen in dark water deeper than meters , so there's no greater protection from black than red. But red is preferred to black because pigment is easier for animals to produce. Some deep sea jellies just have dark red guts, possibly serving to mask luminescent prey from other larger predators with eyes.

Jellyfish have a complex life cycle: a single jellyfish reproduces both sexually and asexually during its lifetime, and takes on two different body forms. An adult jellyfish is called a medusa, which is the familiar umbrella-shaped form that we see in the water. Medusa jellyfish reproduce sexually by spawning—the mass release of eggs and sperm into the open ocean—with entire populations sometimes spawning all together.

Male and female jellyfish there aren't many hermaphrodites release the sperm and eggs from their mouths. In most species, fertilization takes place in the water; in others, the sperm swim up into the female's mouth and fertilize the eggs within.

The fertilized eggs then develop into planulae singular: planula , which are ciliated free-swimming larvae shaped a bit like a miniature flattened pear. After several days of development, the planulae attach to a firm surface and transform into flower-like polyps. Beroids lack tentacles at any developmental stage. Brusca and Brusca, ; Wrobel, Reproductive tissues develop within the meridional gastrovascular canals and gametes are expelled from the mouth, fertilization usually occurs in the water.

In two benthic genera, Coeloplana and Tjalfiella , gametes are taken in through the mouth and fertilization is internal. Ctenophores are able to self-fertilize, although cross-fertilization with other individuals is also common.

Most ctenophores are simultaneous hermaphrodites, although some dioecious species are known, such as members of genus Ocyropsis. Members of order Platyctenida are also known to reproduce asexually, with small fragments that break off as the animal moves, developing into fully-developed adults. Most ctenophores are capable of reproduction before they reach adulthood paedogenesis. As adults, ctenophores release gametes daily for periods of weeks. Gamete production may slow or cease if food becomes scarce.

Brusca and Brusca, ; Jaspers, et al. As hermaphroditic broadcast spawners, ctenophores exhibit no parental investment beyond the production of gametes. While little information is available regarding average ctenophore lifespans, individual species may have lifespans of anywhere from less than a month to three years. Kasuya, et al. While they may have locally high population densities, ctenophores are solitary animals. Movement is achieved through the use of cilial motion, coordinated by an apical sense organ containing a calcareous statolith.

Depending on the comb jellies' orientation, this statolith presses on one of four balancers tufts of cilia supporting the statolith , causing the downside ctenes to beat more vigorously and right the animal. Benthic ctenophores may "creep" along a surface, using their flattened bodies as a sort of foot.

Some ctenophores exhibit diurnal migration, following the movement of their planktonic prey into deeper water during the day and shallower water at night. The beating motion of their cilia causes light diffraction, which causes waves of color change down the comb rows, not to be confused with bioluminescence. Many, but not all species of ctenophores are also bioluminescent, however, producing blue-green light. Brusca and Brusca, ; Haddock and Case, ; Marinova, et al.

The ctenophore nervous system is a non-centralized net, much like that of cnidarians, although it differs in many important specific aspects and is generally more specialized. Ctenophores have a diffuse subepidermal net of non-polar neurons; beneath the comb rows, these neurons form an elongate mesh resembling nerve fibers.

A large concentration of nerve tissue is also found around the mouth. Outside of the apical sense organ, no other sensory organs have been confirmed, although some species possess oval tracts of cilia called polar fields on the aboral surface, which may play some sensory role. Areas near the mouths of some ctenophore species have chemoreceptive cells, aiding in prey detection and capture. All known ctenophore species are carnivorous, feeding on rotifers , small crustaceans including copepods , amphipods , and euphausiids , and the planktonic larvae of many other species including clams and snails.

Beroids are known to feed on other ctenophores. Depending on the body structure of the specific species, prey may be captured with long tentacles or with a mucosal layer on the body surface, which carries the prey to the mouth by ciliary currents. Colloblasts, located on the animals' tentacles or lobes, aid in prey capture; species of genus Haeckelia do not have colloblasts, and instead use sequestered nematocysts from their cnidarian prey.

Species of Euplokamis have prehensile side branches on their tentacles, which wrap around and snare prey. Brusca and Brusca, ; Haddock, ; Mills, Known predators of ctenophores include other ctenophores, cnidarians , medusae , other invertebrates , fishes, whales , sea turtles , and ocean sunfish. Ctenophores may host a variety of parasites, including endoparasitic trematodes , cestodes , nematodes , ectoparasitic isopods , dinoflagellates , and amphipods.

Some species may also host a parasitic sea anemone. They may serve as intermediate hosts to digenean flukes , due to their placement on the food chain.

A few species of ctenophores may themselves be parasitic on salps. Beyond the potential for scientific research and display in public aquaria, there are no known positive economic effects of ctenophores on humans.

Brusca and Brusca, ; Mills, The introduction of the North American species Mnemiopsis leidyi into the Black Sea in the early s, most likely in ballast water from ships originating in the northwestern Atlantic, completely disrupted this ecosystem's natural food chain. As a rapidly reproducing, generalized feeder, it spread throughout the area, outcompeting native planktonic fishes and completely destroying the region's fishing industry within 10 years of its introduction. Since then, another ctenophore , Beroe ovata , has been introduced as well likely by the same means.

A voracious predator, B. Mnemiopsis leidyi and Beroe ovata have moved into the Caspian Sea from the Black Sea; the ecological ramifications of this introduction remain to be seen. As of , M. Mills, ; Shiganova, There is currently no concern that ctenophores will become threatened or endangered, on either a local or global scale. Mills, It is the second largest ocean in the world after the Pacific Ocean.

This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico. In otherwords, Europe and Asia and northern Africa. Abyssal regions are characterized by complete lack of light, extremely high water pressure, low nutrient availability, and continuous cold 3 degrees C. Referring to an animal that lives on or near the bottom of a body of water.

Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans below m are sometimes referred to as the abyssal zone.

Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria. Found on all continents except maybe Antarctica and in all biogeographic provinces; or in all the major oceans Atlantic, Indian, and Pacific. Iteroparous animals must, by definition, survive over multiple seasons or periodic condition changes. Areas of the deep sea floor where continental plates are being pushed apart.

Oceanic vents are places where hot sulfur-rich water is released from the ocean floor. An aquatic biome. An aquatic biome consisting of the open ocean, far from land, does not include sea bottom benthic zone. Examples are cnidarians Phylum Cnidaria, jellyfish, anemones, and corals.

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.

Christopoulos, is that "ctena" means comb in ancient Greek in Modern Greek, too: "ktena" , and "phora" is a morphological ending that comes from the Greek verb "pherein", to bear Modern Greek: "phero".

Ctenophores are fairly simple animals that live only in marine waters; they can be found in most marine habitats, from polar to tropical, inshore to offshore, and from near the surface to the very deep ocean. There are probably about species of ctenophores throughout the world's ocean, although most of these are poorly known.

I have compiled a list of all valid scientific names for the Phylum Ctenophora , meant to be useful for ctenophore biologists, but which has links to various images of ctenophores on the web that others may also find interesting.

The best-known ctenophores are those that occur near-shore. Such species are typically planktonic, transparent and unpigmented, and most swim by synchronous beating of the eight rows of comb plates. Ctenophores are probably common members of the plankton in most coastal areas worldwide, although they have not been studied in many regions; ctenophores may be seasonally much more abundant in the spring and early summer. Their small size a few mm to several cm and transparency make ctenophores relatively inconspicuous, so even though they are not uncommon, in general they are little known.

Display of ctenophores in public aquariums throughout the world has been bringing them to the attention of many thousands of viewers in recent years. The simplest tool for collecting ctenophores from a boat or off a dock is a cup-on-a-stick type jellyfish catcher : several designs are illustrated.

Near-bottom plankton, deep in a fjord in Washington state or British Columbia. Center, lobate ctenophore Bolinopsis infundibulum ; upper right, hydromedusa Aglantha digitale; lower left, pteropod Clione limacina ; copepods. Crayon drawing by Claudia Mills, while listening to student reports about this ecosystem, December The most numerous coastal ctenophores usually have one of three quite different morphologies. Representatives of the order Cydippida are round or oblong in shape, usually less than 3 cm about one inch in diameter, with solid bodies distinguished by eight radial comb rows that provide locomotion, and two, usually-branched tentacles that are used roughly like fishing lines for capturing small planktonic prey.

The most common cydippid ctenophores worldwide are probably species of the genus Pleurobrachia. Common coastal representatives of the order Lobata include members of the genera Bolinopsis and Mnemiopsis. These "lobate" ctenophores are usually larger than coastal cydippids, and have a pair of highly expandable lobes that are used as sticky prey capture surfaces, accompanied by short tentacles that remain inside the lobes. Like cydippids, lobate ctenophores also feed primarily on small planktonic prey.

The third group of ctenophores that are commonly found in coastal areas are members of the order Beroida. Most beroids are in the genus Beroe. These ctenophores are also basically elongate animals that may be cylindrical or very flat, are often more translucent than transparent, and may be colorless or light pink or yellowish. Beroe s open up like a sack to engulf their prey, which is most typically other species of ctenophores! In addition to the relatively well-known coastal ctenophores, there are many species found only far offshore near the surface, or in the mid-water or in the deep sea.

Although the ocean seems rather uniform, each species is representative of only a small portion of the water column, defined by a combination of water temperature, light availability, depth and other factors - many oceanic ctenophore species are found under similar conditions worldwide. Oceanic ctenophores tend to be much more fragile that coastal species, because they do not need to tolerate wave action or the turbulence and sediment load of coastal waters.

Some of them have fastastic, unlikely shapes. Recognizable species of open ocean near-surface ctenophores include the wing-like Venus' girdle, Cestum veneris. Lesser known species include the lobe-flapping Ocyropsis , which does a kind of frog kick with its feeding lobes for locomotion.

Through observations carried out by open water scuba divers and by manned or unmanned submersibles in the last couple of decades, scientists now have a much better knowledge of these oceanic species, many of which are still unnamed and many others probably still unknown. A few of the oceanic species turn out to get quite large, approaching a meter in maximum dimension, but they are usually so fragile that they cannot be collected in nets. Since these fragile species do not preserve well, our best records are in the form of photographs taken from submersible vehicles.