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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.
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.
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? 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. 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. We’ve been doing this for 15 years now, and yet we still see new stuff almost every dive,” says MBARI scientist Bruce Robison. “And that’s just in Monterey Bay. Our knowledge about the deep sea is still so poor that even after all these years of diving in this one spot, we still see new things all the time.”
Through the use of remotely operated submersible vehicles, or ROVs, scientists at MBARI have gained unprecedented access to the jellies’ realm. A scientific ROV is essentially a swimming robot outfitted with research equipment such as sampling containers, headlights, and high-resolution video cameras. While the vehicle dives deep into the cold undersea darkness, scientists sit comfortably aboard a ship on the sea surface, controlling the ROV movements remotely and watching its video feed on a bank of screens. Manned submersibles are also used in studying jellies, but an ROV, freed from its human occupant, can run longer without resurfacing and makes an excellent camera platform. In recent years we’ve learned that larvaceans account for a quarter to maybe a third of all the organic carbon that gets from the upper layers of the ocean in Monterey Bay, at least down to the deep-seafloor community,” Robison says. “They play a critical role in the transfer of energy from the sunlit layers to the deep seafloor.” 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. The larvae settle on the seafloor and are now known as polyps. The polyps then begin to bud asexually and produce medusae which then develop into adults. Other true jellyfish species belonging to other genera may spend their lives solely as polyps or medusae and not alternate between the two different life stages in the same way. Jellies are perfectly adapted to a three-dimensional watery habitat,” Robison says. “The fact that we see so many different kinds of them reflects the fact that they have a fundamentally successful body plan and way of making a living.”
The Basics
Like most venomous animals, the jellyfish inject their venom to cause pain and irritation. Jellyfish venom contains a type of protein called a porin which is responsible for the pain caused by their sting. This protein is not only found in the venom of all jellyfish but also in their relatives, including corals and anemones. 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. 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.
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. Not a lot is known about the ways that the various jellyfish species reproduce. The best-studied jellyfish belong to the genus Aurelia. These jellyfish have separate sexes and so the adults reproduce sexually. The males release their sperm through their mouths which then enter the surrounding water. These swim to the female and enter into her oral cavity where they are then able to reach the eggs. Once the eggs are fertilized, the fertilized eggs (zygotes) move into the oral arms where they spend some time developing and becoming larvae. 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.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. 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 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
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.” Submersible vehicles also offer a unique window on jelly behavior and ecology. “One of the advantages of working on jellies is that they’re blind and deaf,” Robison says. “They don't seem to mind at all when we fly up to them and zoom in with our lights and cameras. We can make good observations of the interactions of jellies with one another, their prey, and their predators, without disturbing them.” And the jellies themselves, being transparent, offer an additional window onto their lives. “Who eats whom that’s easy to see with a transparent animal,” Robison says. “You don’t have to cut them open to find out what was for lunch.”
Fun Facts about the Jellyfish!
Jellyfish have been around for millions of years, even before dinosaurs lived on the Earth. Pulsing along on our ocean currents, these jelly-like creatures can be found in waters both cold and warm, deep and shallow and along coastlines, too. Some jellyfish are clear, but others are vibrant colours of pink, yellow, blue and purple. They can be bioluminescent, too, which means they produce their own light! 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? 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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