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TOP RARE and Most BEAUTIFUL Seashells
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MOLLUSKS MAKE ONLY ONE SHELL. • Mollusks use calcium carbonate and proteins, secreted from their mantles, to build their shells. As a mollusk grows, so does its exoskeleton. • MOST SHELLS OPEN TO THE RIGHT. • Although there are some species with shells that are always sinistral, or left opening, nine out of 10 shells are dextral, meaning they open to the right. • Though shell collectors might love them, there are dire consequences to being a sinistral animal: Mating with dextral mollusks is pretty much impossible. • SHAPE MATTERS. • Seashells can be plain and smooth (think clamshells) or come adorned with spikes and ridges and protrusions. Both shapes serve a purpose. Elaborate shells come from the tropics, where predation is fierce. Mollusks in the tropics evolved these ornaments to ward of predators—a much better option than creating a big, thick shell, which will keep predators at bay but is also a pain to make and drag around. The pleats and corrugations on many tropical shells are a cost-effective way of creating a strong body armor that’s difficult to break into while keeping the weight down. Thickening and flaring out the aperature of seashells is another way of deterring predators. • Sleeker mollusks, meanwhile, can use their streamlined shape to move without detection and to get away quickly. A shell’s shape can also keep the mollusk from sinking in sand and mud, or to keep them anchored in it. • THE PATTERNS ON SHELLS AREN’T RANDOM. • Recent research suggests that the elaborate colors and patterns on shells are not frivolous playthings but important registration markers for shell-making that have been subject to the forces of natural selection, and have evolved over time. In other words, mollusks might use the patterns to figure out where to put their mantles to continue making their shells. Scientists still aren’t sure what kinds of pigments the mollusks are using. • THE OLDEST KNOWN HERMIT CRAB USED AN AMMONITE SHELL. • There are nearly 1000 species of hermit crab existing today, which rely on old seashells from dead mollusks to protect their soft abdomens. (Interestingly, hermit crabs never kill the current occupants of the shells; they wait until the mollusk has died, and let other animals do the eating, before they take over.) The oldest known hermit crab fossil was discovered in 2002, in the Yorkshire, England village of Steepton. Paleontologist Rene Fraaije spotted the crab in the shell, which, belongs to an ammonite, “an extinct cephalopod that swam through far more ancient seas, in the Lower Cretaceous around 130 million years ago. After it died it sank down to the seabed where a crab scuttled past, picked it up and climbed inside.” It’s the only one found in an ammonite so far. • #RareSeashells #TOP
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