The group of organisms known as jellyfish is one of the oldest and most successful. An in-depth investigation of the genome of the moon jelly, Aurelia aurita, reveals that this organism employs the same group of genes during the transition between its polyp and swimming phases of life.
Photographs courtesy of the Birch Aquarium at the Scripps Institution of Oceanography, University of California, San Diego Jellyfish go through a remarkable transformation, beginning as small polyps that develop on the ocean floor and ending as medusae that move through the water and have tentacles that may hurt.
This ability to change form has served jellyfish well throughout the course of more than 500 million years, shepherding them through several instances of major extinctions on Earth. According to David Gold, an associate professor of paleobiology in the UC Davis College of Letters and Science, “Whatever they’re doing has really worked for them.” The genome of a jellyfish, namely that of the moon jelly Aurelia aurita, has been analyzed in such detail for the first time, and the results have revealed the roots of a successful survival strategy.
- The findings of the Aurelia genome, which were co-led by researchers at the University of California San Diego and published online on December 3 in the journal Nature Ecology and Evolution, reveal that early jellyfish recycled existing genes in order to transform from polyp to medusa.
- According to the findings, it appears that animals are able to easily radiate into new niches and forms.
According to Gold, who was the head researcher on the genome project, “These findings give more evidence that evolution does not always make the genetic code more complicated.” [Citation needed] “Jellyfish may develop an extensive and complicated life history utilizing many of the same genes that are found in lesser species.” Takeo Katsuki, a former project scientist at the Kavli Institute for Brain and Mind at UC San Diego and currently an application specialist at Thorlabs Japan Inc., and Gold, who performed the majority of the work as a postdoctoral fellow at the California Institute of Technology, shared equal leadership of the research team.
Gold was responsible for the majority of the work that was completed. “Having their genome sequence establishes their study as a key addition to what we know about their biology,” said Ralph Greenspan, a professor in the UC San Diego Division of Biological Sciences’ Section of Neurobiology and associate director of the Kavli Institute for Brain and Mind, who also led the study.
“Jellyfish are important both evolutionarily and environmentally,” Greenspan said. “Having their genome sequence establishes their study as a key addition to what we know about their biology.” Moon jellies may be found in the Birch Aquarium, which is part of the Scripps Institution of Oceanography at the University of California, San Diego.
The genome: a resource with many applications The phylum Cnidaria, of which corals and anemones are also members, is home to jellyfish. This is one of the most ancient branches on the tree of the animal kingdom. It’s likely that jellyfish were the first animals in the open ocean to swim using their muscles.
They first arose during the latter part of the Precambrian Period, which was a time of significant geologic and biological shifts that came before the Cambrian Explosion of Animal Life. Jellyfish, at some time in their evolutionary history, obtained the capacity to transform from a polyp, which is a stationary form, into a medusa, which is a swimming form.
- Major alterations take place in the jellyfish’s nervous system, muscles, and armament, which are referred to as cnidocytes.
- These alterations take place throughout the transition.
- The researchers discovered that in order for the medusa life stage to do this, it frequently co-opts existing developmental gene networks and cell types that are present in polyps.
According to the findings of the study, Aurelia appears to design its many life phases by making use of many of the same genes that are present in mammals such as fruit flies and humans (all of these animals share a common ancestor, albeit an ancient one).
There is a second explanation for what the researchers discovered in the jellyfish genome, and this one is the more contentious of the two. It’s possible that the parallels between the genome of the moon jellyfish and the genomes of “higher” species show that the Cnidaria originally had a medusa life stage, but that animals like corals and sea anemones lost it through time.
According to Gold, “Our data are unable to differentiate between these two possible outcomes.” “Swimming, carnivorous animals may be considerably older than we believe they are,” if the second hypothesis turns out to be right in the study. According to Gold, the Aurelia genome will be useful in many other areas of biology in addition to concerns pertaining to the process of evolution.
The study of the development and operation of neural systems, as well as animal wound healing and regeneration, can benefit greatly from the use of Aurelia as a model. Moon jellies are also a key contributor to harmful jellyfish blooms, which are occurring increasingly often and wreaking havoc on the environment as well as the economy.
For instance, enormous swarms of moon jellies have choked water-intake pipes at nuclear power facilities in Florida and Sweden, which has resulted in the plants being shut down. A better knowledge of the genetics of Aurelia might lead to the discovery of novel approaches to managing the blooms.
Studying how jellyfish developed in the past might teach us about their possible influence on the future, as Gold explained, “in many aspects, the ancient waters in the late Precambrian are very much like what the present oceans will look like in the near future.” Yang Li and Xifeng Yan of the University of California, Santa Barbara; Michael Regulski of Cold Spring Harbor Laboratory in New York; David Ibberson and Thomas Holstein of Heidelberg University in Heidelberg, Germany; Robert Steele of the University of California, Irvine; and David Jacobs of the University of California, Los Angeles are also listed as authors on the paper.
The National Institutes of Health, a Cordes Postdoctoral Grant at Caltech, the W.M. Keck Foundation, the Gordon and Betty Moore Foundation, a fellowship from the Uehara Memorial Foundation, and the NASA Astrobiology Institute all contributed to the funding for this study. 
Contents
How a jellyfish is made?
Jellyfish have two distinct body shapes throughout their lifecycles, known respectively as the medusa and the polyps. By budding, polyps are able to reproduce asexually, but medusae must create eggs and sperm in order to reproduce sexually. Discover more about the different stages of the jellyfish life cycle, including reproduction.
Where is jellyfish found?
| Jellyfish | |
|---|---|
| Pacific sea nettle ( Chrysaora fuscescens ) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Subphylum: | Medusozoa |
| Groups included | |
| Acraspeda Cubozoa —box jellyfish Scyphozoa —true jellyfish Staurozoa —stalked jellyfish some Hydrozoa —small jellyfish | |
| Cladistically included but traditionally excluded taxa | |
| some Hydrozoa , such as Hydra |
The medusa-stage of some gelatinous species of the subphylum Medusozoa, which is a key component of the phylum Cnidaria, is commonly referred to as a jellyfish or a sea jelly. Other common names for this stage are moon jellies and comb jellies. Jellyfish are primarily mobile marine organisms that have bells shaped like umbrellas and tentacles that trail after them; however, there are a few species of jellyfish that are fixed to the seafloor by stalks rather than being mobile.
- The ringer may pulse in order to create propulsion, which allows for extremely effective mobility.
- It is possible for the tentacles, which are equipped with stinging cells, to be employed to both catch prey and protect against potential predators.
- Jellyfish have a complicated life cycle; the medusa is often the sexual phase, and it is this phase that gives rise to planula larvae, which then spread extensively and transition into a sedentary polyp phase before reaching sexual maturity.
It is possible to encounter jellyfish in any body of water on the planet, from shallow coastal waters to the depths of the ocean. Scyphozoans, sometimes known as “real jellyfish,” are only found in saltwater environments, but certain hydrozoans with a similar appearance may be found in freshwater environments.
- Large, typically colorful, jellyfish are widespread in coastal zones worldwide.
- The medusae of most species develop within a few months and perish shortly after reproducing, but the polyp stage, which is anchored to the seafloor, may have a significantly longer lifespan than the medusae.
- Jellyfish have been around for at least 500 million years, and it’s possible that they’ve been there for 700 million years or more, making them the oldest animal group that possesses more than one organ.
In some parts of the world, jellyfish are prepared and consumed by humans. They are salted and pressed in order to eliminate excess moisture and are regarded a delicacy in certain Asian nations. These countries are home to species of the order Rhizostomae.
- Researchers in Australia have referred to them as the “ideal food” because to the fact that they are sustainable, high in protein, and relatively low in food energy.
- The green fluorescent protein that is used by certain species to create bioluminescence has been repurposed as a fluorescent marker for genes that have been put into other cells or creatures so that it may be utilized in study.
This is another usage for these proteins. The stinging cells utilized by jellyfish to subdue their prey can damage people. Every year, thousands of swimmers all over the world get stung, and the resulting repercussions can range from a minor discomfort to a catastrophic injury or even death.
When did jellyfish come into existence?
Whichever occurred first, comb jellies and jellyfish (and other Cnidarians) achieved a crucial stride in the history of evolution. They are the oldest known creatures to have structured tissues—their epidermis and gastrodermis—and a nervous system. Fossil jellies have been found all over the world.
- They were also the first animals that were discovered to swim by utilizing their muscles rather than just floating with the currents of the ocean.
- At a minimum of 500 million years ago, and maybe as as far back as 700 million years ago, the progenitors of modern-day jellies were already in existence.
According to this, jellyfish have been around for three times as long as the earliest dinosaurs. It is extremely uncommon to uncover fossils of jellyfish due to the absence of bones and other rigid body features. However, in 2007, a group of scientists led by Allen Collins from the Smithsonian National Museum of Natural History uncovered some exceptionally well-preserved jellyfish fossils (link is external) that dated back 505 million years and were buried in Utah.
- In the Burgess Shale, researchers have discovered fossils of well-preserved comb jellies that date back to around the same time period.
- (This link will take you to an external website.) The cilia and plates of fossils discovered at the Quingjiang site in southern China in 2019 (link leads to an external website) are among the finest preserved Cambrian fossils ever discovered, with the fossils having been discovered in 2019.
It is hoped by the scientific community that this discovery will assist in determining the link that exists between jellyfish and comb jellies.
What causes jellyfish to come?
Where do the jellyfish come from that are found on the beach? Jellyfish are said to have a laid-back attitude. Because they go together with the current, there is a possibility that jellyfish will wash up on the coast if it moves in that direction. Jellyfish can also be brought closer to shore by stormy weather and high gusts, and they may eventually wash up on the beach.
Do jellyfish get pregnant?
The form of the jellyfish known as the medusa, with its bell-shaped body and lengthy tentacles, is just one of numerous phases that occur throughout the life cycle of the jellyfish. In their evolution, jellyfish can take a variety of different shapes.
- A recent initiative undertaken by one of our interns has resulted in the addition of a miniature ephyra bowl to the lagoon jelly section of our Tropical Pacific display.
- This will allow visitors to the Aquarium to observe a different stage in the life cycle of jellyfish.
- Ephyra are the free-swimming stage of development that occurs before medusa reach their full adult size.
Jellyfish are capable of both sexual and asexual reproduction. The previous generation, known as the medusa, is responsible for sexual reproduction, while the generation that follows, known as the polyp, is responsible for asexual reproduction. Moon jelly (Aurelia aurita) men in their medusa form, which can be seen at the Ring of Life exhibit, emit sperm trails that are taken up orally by moon jelly females, and internal fertilization occurs as a result of this process.
The medusas of the lagoon jelly, also known as Mastigias papua, may be seen at Ocean Oddities. They spawn directly into the water. Fertilized eggs of both species first grow into a multi-cellular planula, and then they transform into polyps, which are found living on the ocean floor. Jellies reproduce asexually by a process called strobilation while they are in the polyp stage and look like little anemones.
When a polyp strobilates, or divides its body into segments in order to reproduce, it exudes very small ephyra into the surrounding water. Within a short period of time, a bell will emerge, and the ephyra will be deemed to be medusa. This will cause the process to begin all over again.
Do jellyfish come from eggs?
Sebastian Dill from Bermuda asked the question. There are a few species of jellyfish that take in sperm through their mouths in order to fertilize eggs that are located within the body cavity, but the vast majority of jellyfish simply discharge their sperm or eggs directly into the sea.
When conditions are favorable, they will do this behavior once a day, often timed to coincide with either dawn or sunset. The fertilized eggs will eventually hatch into teeny, free-swimming flatworms known as planulae. These planulae will either mature into adult jellyfish directly or will settle on rocks to create an intermediate polyp stage.
After that, the polyps are able to reproduce asexually by bursting off little jellyfish that are one or two millimeters across. These tiny jellyfish feed on plankton and gradually grow into full-size adult jellyfish. Continue reading: What exactly do corals consume? Would it be possible for people to live forever? You can get a fascinating new set of questions and answers in each issue of BBC Focus magazine, and if you follow @sciencefocusQA on Twitter, you can get a taste of entertaining science information every day.
