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All 200 species of jellyfish exhibit radial symmetry. This means that they have a distinct top and bottom, but do not have a left or right side as all of their appendages radiate outwards from a central point, rather like the spokes of a bicycle wheel. A Mediterranean jellyfish. Jellyfish Reproduction 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 There’s a whole netherworld of the deep sea that we don’t see when we have our lights on,” says Kevin Raskoff, a scientist at California State University, Monterey Bay. “And that’s the natural light of the deep sea: bioluminescence.” 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.” 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.
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.” 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. 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 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.”
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.” 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. 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. 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.
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. 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. The light is produced by a chemical reaction between a chemical substance called luciferin and oxygen from the environment. This reaction releases energy and as a result, light is emitted. An enzyme called luciferase helps this reaction occur. For an animal to emit light regularly they must continually bring new luciferin into their system. Some animals acquire it through their diet while others can produce their own. 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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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. 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
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