ASK CLAUDIO - DISCOVER THE SCIENCE BEHIND THE SCENES
Learn more about the wacky world of underwater marine sex with GREEN PORNO's marine biologist, Dr. Claudio Campagna!
CLICK ON AN ANIMAL TO LEARN MORE:
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CELESTIAL BEINGS
Some people believe in this equation: starfish = sea stars + brittle stars. Sea Stars are the most famous five-arm creatures that function as the imprinted image for the entire group. But nature perserveres when it manages to find a design that works, and celebrates success by creating variations around the theme. Thus, there are over 1,800 species of starfish, some have less than five arms while others have more arms than numbers can account for. Brittle stars are also multi-ray organisms, but instead of resembling a celestial object that shines in the black night, they are reminiscent of a stylish spider, with long and thin legs.
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THE PERFECT BALANCE
If faced with a mirror, starfish would not be able to decide on their best profile, as they are structurally shaped to resemble a wheel, unlike the two-sided bodies that dominate in nature.
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ELABORATE DESIGN
Under the skin, starfish would make the complex piping system of a distillery, or a modern motorcycle, look like a toy for children. They have a hydraulic vascular system to allow locomotion and feeding by the circulation of currents of water that enters into the body through a filtering valve. Turn a sea star upside down and you will see a busy surface of moving tube feet in which their interior circulates water.
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QUITE A MOUTHFUL
Sea stars like to eat beyond the size of their mouth. For the occasional lunch, and for dinner, they prefer oysters and clams (although they are also scavengers). Food is digested in the stomach, of course, and they have two of them: the cardiac stomach can be extended outwards, everted, to engulf and pre-digest externally large prey. This is handy, as it prevents spoiling the streamlined waist of the bodies by the bulk of a mouthful of food.
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LOVE IS IN THE WATER
Starfish come in two sexes. They reproduce by releasing huge quantities of sperm and eggs to the environment, in a synchronized pattern. Fertilization takes place externally and embryos become part of the plankton... although there are exceptions. Some species brood their young: females hold the eggs or attach them to the ground.
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BRANCHING OUT
But the really bizarre attribute of sea stars is their capability of asexual reproduction by fragmentation. Two individuals may result from the division of one in two halves, or a complete animal could be generated from a piece of an original one. It is true that not just any original "piece" has the potential to grow into a complete new copy. To reproduce, the new piece must contain some cells from the "central disk" - the brainless center of operations from where the arms branch out of the creature.
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BOTTOM DWELLERS
But there is one thing these super-duper marine organisms cannot do: they cannot live in the water column. They are constrained to the bottom of the ocean, from shallow coastal waters to depths of thousands and thousands of meters.
