10 Things You Didn’t Know About Jellyfish
1. Jellyfishes are made up of more than 95% water.
Their bodies are soft and lack a skeletal structure or outer shell. They are delicate and easily damanged. Jellyfishes require water to help support their body and if removed from their aquatic surroundings, they collapse and die.
2. Jellyfish are radially symmetrical.
Jellyfish are symmetrical about a central axis that runs through the length of their body, from the top of their bell to the ends of their tentacles. They have a top and a bottom but they lack a left and right side and as a result differ from many other types of animals (such as mammals, reptiles, fish, birds, and arthropods) which exhibit bilateral symmetry.
3. A jellyfish has a simple digestives system with only one opening.
A jellyfish takes food in through its mouth which is located on the underside if its bell. Food is digested in a sac-like structure called a coelenteron or gastrovascular cavity. Waste material is passed out through the mouth.
4. A common analogy used to describe the delicate way jellyfish pounce through the water likens the jellys’ movements to ‘a simple form of jet propulsion’.
To move forward, jellyfishes take water into their muscular bell and then squirt it out behind them, creating a jet of water that propels the jelly forward. In addition to this form of movement, jellies also drift on water currents to move.
5. Jellyfishes have no brain, no blood, and no nervous system.
Their senses are primitive and consist of a neural net, eye spots that can sense light from dark, and chemosensory pits that help them identify potential prey.
6. A jellyfishes’ body consists of three layers.
The outer layer is called the epidermis, the inner layer which lines the gastrovascular cavity is called the gastrodermis, and the middle layer consists of a thick substance called the mesoglea.
7. Thousands of nematocytes are located on the tentacles, feeding arms, and mouth of a jellyfish.
Nenatocysts consist of a capsule that holds a hollow barbed coil, a vemon sac, and chemo-sensitive trigger hairs that detect when something edible brushes against them. When potential prey brushes against the trigger hairs, the nematocytes expel the coiled barb and inject venom into the victim through the hollow thread. The venom immobilizes the prey and the jellyfish uses its oral arms to move the prey into its mouth where it is passed through to the coelenteron for digestion.
8. Jellyfish belong to the Phylum Cnidaria.
This group of animals, all radially symmetrical, includes corals, sea anemones, hydras, and jellyfish.
9. There are about 200 species of True Jellyfishes.
True Jellyfish are species belonging to the Class Scyphozoa. Examples of True Jellyfish include Moon Jellies, Mediterranean Jellyfish, Sea Nettles, Lion’s Mane Jellyfish, Blue Jellies, and many other lesser known species. The Class Cubozoa includes about 20 species not considered to be True Jellyfish. The Class Cubozoa is also referred to as box jellyfish. The most imfamous of the Cubozoa is the Sea Wasp, a creature with a deadly sting that inhabits the waters off the coast of Australia.
10. The species Craspedacusta sowerbii is sometimes referred to as the only species of freshwater jellyfish, although it is not a true jellyfish.
Craspedacusta sowerbii belongs to the Class Hydrozoa (the group of animals that includes the hydra), not the Class Scyphozoa.
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Rich Life Under the Sea
Gelatinous Zooplankton
Credit: Photo by L. Madin, NOAA, Census of Marine Life, 2006
Census of Marine Life scientists trawled rarely explored tropical ocean depths between the southeast U.S. coast and the Mid-Atlantic Ridge, revealing a newfound variety of zooplankton and other small creatures. Shown above is an
(Source: livescience.com)
Glowing Blue Waves Explained
Sea of Stars
Photograph by Doug Perrine, Alamy
Pinpricks of light on the shore seem to mirror stars above in an undated picture taken on Vaadhoo Island in the Maldives.
The biological light, or bioluminescence, in the waves is the product of tiny marine life-forms called phytoplankton—and now scientists think they know how some of these sea beasts create their brilliant blue glow.
Various species of phytoplankton are known to bioluminesce, and their lights can be seen in oceans all around the world, said marine biologist and bioluminescence expert Woodland Hastings of Harvard University. (Also see “Glowing Sea Beasts: Photos Shed Light on Bioluminescence.”)
“I’ve been across the Atlantic and Pacific, and I’ve never seen a spot that wasn’t bioluminescent or a night that [bioluminescence] couldn’t be seen,” Hastings said.
The most common type of marine bioluminescence is generated by phytoplankton known as dinoflagellates. A recent study co-authored by Hastings has for the first time identified a special channel in the dinoflagellate cell membrane that responds to electrical signals—offering a potential mechanism for how the animals create their unique illumination.
—Ker Than
Mosaic
Photo and caption by Andrey Narchuk
Patterns of sea stars as exquisite mosaics, attractive, and each time is differen
The Otherworldy Flora and Fauna of the Coral Triangle
1. Mantis Shrimp
Stretching from Indonesia to the Philippine Islands, the Coral Triangle is home to a vast array of coral species and fish life.
2. Coral Polyps
Roughly 1.5 billion acres in size, the region is home to more than 75% of the world’s coral global species.
3. Organ-Pipe Coral
Like several other biodiverse marine regions, the area is under threat from overfishing and higher water temperatures that interfere with the coral’s life cycles.
4. Denise’s Pygmy Seahorse
The reef also features the highest diversity of coral reef fishes in the world.
(Source: TIME)
TOSSED AT SEA
Battered coral embryos three hours after fertilization show a mix of fragments and intact individuals. The broken bits turn out to be able to bounce back as small but functional larvae.
Credit: Image courtesy of Science/AAAS
Sand Trap
Photograph by Ramón Domínguez, DEEP Indonesia/Barcroft/Fame Pictures
Titled “Underwater Sadness,” a photograph of a sea turtle caught in a net in the Sea of Cortez (see map) won third place in the “Environment and Conservation” category.
Six of the seven known sea turtle species are listed as vulnerable, endangered, or critically endangered on the International Union for Conservation of Nature’s Red List of Threatened Species. (See more sea turtle pictures.)
Fifteen percent of the Deep Indonesia contest’s proceeds will be donated to marine-conservation efforts.
Nudibranch (Cratena peregrina)
Tarragona, Catalunya, Spain. Photographer: Jordi Benitez, Spain.
