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Bioflourescent jellyfish: Getty Images UK. Close-up of purple jellyfish: Bruce H. Obison. Jellyfish with long tentacles: Natursports, Dreamstime. Yellow jellyfish: Tim Hester, Dreamstime. Map showing jellyfish distribution: National Geographic Maps. The jellyfish’s mouth is found in the centre of its body. From this small opening it both eats and discards waste. And it serves another purpose, too – by squirting a jet of water from its mouth, the jellyfish can propel forward! Cool, eh? While in space, the number of jellyfish multiplied. On their return to Earth, the scientists examined these space-born animals and discovered that unlike Earth-born jellies, they couldn’t figure out how to deal with gravity. Through genetic analysis, biologists are slowly gaining a better understanding of how and when the jellies evolved. Needless to say, fossils of jellies are few and far between. The evidence now suggests that jellies are an ancient life-form, hundreds of millions of years old, and probably predate most of the more familiar, complex animals. But many questions remain. For example, the comb jellies are typically classified into two types, those with tentacles and those without. Which type is older? Did the tentacleless kind appear first and the tentacled kind evolve later? Or did tentacles come first and then, in some comb jellies, disappear over time? Only further study and exploration will tell. What marine researchers know for certain is that the jellies they’ve discovered so far represent only a small fraction of what’s out there.
The immense number of jellies, and the many roles they play in food webs, could explain a larger mystery about Earth’s carbon cycle. To better understand the global climate and changes in the biosphere, scientists need an accurate measure of the total amount of carbon that is cycling between the planet’s living inhabitants, atmosphere, oceans, and solid earth. Consistently, however, they have faced a “budget gap” in their accounting. About 25 percent of the carbon that shouldbe out there seems to be missing. Where is it? Jellies are a completely surprising component of the deep-sea food web,” Robison says. “Our present understanding of where jellies fit into the way the world works is far from complete. But it’s very clear they are a significant part of deep-ocean communities.” Many jellyfish species have the ability to produce their own light, in a process known as bioluminescence. This light is used primarily as a form of communication between animals and can be used for defense, offense, and intraspecific communication. The greatest diversity in jellyfish bioluminescence occurs in deeper water, where nearly every kind of jellyfish is luminescent and is mostly used in defense against predators. Underwater, bioluminescence finds all manner of purpose. Some animals use it to attract mates. A male sea-firefly ( Vargula hilgendorfii) will squirt out a bright dot of light, zip upward, and then squirt another and another, essentially drawing an arrow that points out his whereabouts. Other creatures use bioluminescence to detect or lure prey. The viperfish ( Chauliodus sloani) dangles a luminescent lure in front of its mouth and then snaps up any creature that dares to investigate.Jellies share a remarkably basic construction. The “jelly” in jellies is little more than a mixture of saltwater and some carbon-containing sugars. True jellyfish (phylum Cnidaria, class Scyphozoa) are made of two transparent layers, an outer one for protection, and an inner one that handles digestion. In between, a small amount of fibrous jelly called mesoglea serves as the scaffolding for everything else what little there is. Ctenophores, or comb jellies, have a similar construction. As a general group, jellies possess a large percentage of watery, transparent tissue.
The advance of molecular biology has greatly aided scientists in their ability to identify and classify organisms. Ultimately, the taxonomy of organisms--how they are grouped in relation to one another--should reflect a common evolutionary ancestry. By examining and comparing DNA, which organisms inherit through reproduction, taxonomists have gained a much clearer picture of how organisms are related to one another across all taxonomic levels.
The jellyfish itself provides a tasty meal for other ocean creatures, particularly sea turtles, who like to guzzle them up regularly. In some cultures around the world, people eat jellyfish, too. In China, they are considered a delicacy, and are also used in Chinese medicine. Jellyfish are known for their sting! These animals have tentacles that have tiny sting cells on them called cnidocytes. These cells have tiny structures inside them that are full of venom, called nematocysts. When something touches a jellyfish these nematocysts shoot out and can penetrate the skin of the animal. The jellies use this mechanism to help capture prey or as a defense mechanism when they feel threatened. What is clear to jelly scientists is how much of the deep sea remains unexplored, and how much there is still to learn about its gelatinous inhabitants. “You can’t really understand what’s going on in there until you know who the players are,” says MBARI’s George Matsumoto. “That’s where we are right now. We’re still trying to understand who all the different players are in the deep sea.” Only in recent years have marine biologists come to grasp the astonishing abundance of gelatinous animals in the world’s waters. By some estimates, transparent jellies make up as much as 40 percent of the biomass in the open ocean. Now, with an improved ability to detect and study these creatures, scientists are slowly coming to a more complete understanding of how ocean food webs work.
And much like jellies, many scientists have even incorporated bioluminescence into their own work lives, often unaware of its original origin. Photoproteins, first isolated from jellyfish several decades ago, are now an integral part of laboratory biology and help researchers do things like mark and identify crucial gene sequences in medical studies. When Bruce Robison was just starting out in marine biology, the study of deep-sea life usually involved dragging a net behind a ship. This method was efficient but selective, he recalls. Trawl samples gave scientists a skewed picture of what populates the oceanic water column: large numbers of fishes, crustaceans, and squids–the hard-bodied animals the nets could actually snare–plus “a handful of goo” that was tossed overboard. These are busy times for jelly discoverers. The use of submersible vehicles has enabled scientists to explore the world of jellies in depth; new creatures are constantly appearing. In February 2004, Raskoff and Matsumoto announced the discovery of yet another deep-sea jelly, Stellamedusa ventana,a tentacleless organism they’ve affectionately named “Bumpy” for the many warty lumps on its softball-size body. Jellyfish are so cool they have even traveled into space! In 1991, some moon jellyfish were sent into outer space on board the Space Shuttle Columbia. This mission was a study conducted by scientists to understand how microgravity affected them. Bioluminescence is found in many marine organisms including around 1500 species of fish! Some species of sea stars, crustaceans, worms, and sharks are also luminescent. Moon jellyfish were sent into space by scientists who wanted to understand how they would respond to microgravity. Jellyfish in Space
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MBARI scientists have put ROVs to work performing various tasks. One simply involves gathering data about jellies: how many of which kind are where, what they do, and when they do it. The ROVs make underwater runs of a certain length at different depths, filming all the while. Later, scientists watch the video and count all the jellies they can. The work is tedious but enlightening. For the first time, scientists are estimating how many jellies are actually down there. And they can monitor how jelly populations change over time with the seasons or in relation to long-term climate cycles like the El Niño southern oscillation. Jellies were always relegated to an interesting but fringe category of strange, snotty animals in the water,” says Kevin Raskoff, a jelly scientist at the Monterey Bay Aquarium Research Institute. “But once we saw how prevalent they are and the diverse habitats they’re found in, it caused us to rethink their role in ecosystems as a whole.”
Almost from the moment George Matsumoto of the Monterey Bay Aquarium Research Institute first saw “Big Red,” he knew he was looking at a new species of jellyfish. It looked just plain bizarre: bulbous, dusky red, and huge, nearly one meter (about three feet) in diameter, with several fleshy arms instead of tentacles, like a balloon with greedy fingers. When Matsumoto and his coauthors, Kevin Raskoff of California State University and Dhugal Lindsay of the Japan Marine Science and Technology Center, described it in a scientific paper in 2003, they gave it a more official name: Tiburonia granrojo. Jellies may also be important indicators of the health of ocean ecosystems. Some biologists have speculated that jelly populations thrive as increasing numbers of shrimps, fishes, and squids are harvested from the oceans, leaving behind vast amounts of uneaten small prey. A rise in jellies may signal drastic changes underway elsewhere in the ocean. “There is evidence,” Robison says. “But while it’s compelling evidence, it’s not yet convincing evidence.” Jellyfish are one of the oldest animals on Earth and have changed very little from their prehistoric ancestors. These fascinating creatures have been studied by scientists for decades, increasing our understanding of the biological adaptations that have enabled them to persist in the world’s oceans for so long. Let’s take a closer look! Jellyfish Sting Bioluminescence is light produced by a chemical process within a living organism. The glow occurs when a substance called luciferin reacts with oxygen. This releases energy, and light is emitted. An enzyme called luciferase facilitates the reaction. Sometimes luciferin and luciferase are bound together with oxygen into a single molecule, or photoprotein. When an ion such as calcium is present, an ensuing reaction emits light. To glow on a regular basis, an organism must continually bring fresh luciferin into its system. Some acquire it through their diet; others produce their own.Humans can also be stung by jellyfish which can result in mild symptoms such as pain and blistering, to more serious symptoms including whole-body illness. In some cases, stings can even be life-threatening. Bioluminescence
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