The findings were described online April 23 in the journal Biology Letters. Original article on Live Science. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
IE 11 is not supported. For an optimal experience visit our site on another browser. Politics Covid U. News World Opinion Business. This lets them hang onto branches without using any extra energy. Sloths have evolved internal anchors made of connective tissue that hold their organs in place. And that keeps the weight from pressing on their lungs. This lets them breathe freely, even when they hang completely inverted from their hind legs.
And that easier breathing is another way they save energy. That brings us to Cassiopea, a genus of upside-down jellyfish that lives in warm coastal regions like the Caribbean and western Atlantic. All jellyfish start out upside-down, tethered to the ground. Then after they break free, most species flip right-side-up. This one can be found swimming right-side up occasionally, but its natural position is to stay inverted.
First, its arms are home to symbiotic algae, similar to the ones that live in coral. The algae uses photosynthesis to make food, which it shares with its host. But their upside-down pulsating action draws nutrients up from the sediment and across their many mouths so they can feed. In fact, these nutrients feed the entire ecosystem, including little animals the jellyfish sometimes capture for food.
So this odd lifestyle works out for the upside-down jellyfish. And it has a couple of useful adaptations to help it get by this way. To protect its delicate belly, its body makes compounds that absorb harmful UV light. Back on land, a small woodland bird called the nuthatch is known for its habit of foraging upside-down. But when they look for food, they usually go head-first down tree trunks and underneath branches.
Other birds that compete with them, like woodpeckers and creepers, forage right-side-up. So researchers think that flipping over may help the nuthatch find food that these other birds miss. And—it may also help them hide food.
They often tuck seeds and bugs into small cracks, stashing them for the winter. And these upside-down food stashes may be less visible to other birds. At the same time, its claws are narrow, so they can grab tiny footholds. And they have an unusual way of working their feet that helps them stick to vertical surfaces. With their feet staggered, they use the upper leg to pull in close the tree while pushing outward with the lower leg for stability.
Then, rather than walking, they use more of a hop to drop down to a new spot. Moving back to the sea, you can find another kind of upside-down animal right along the shore. Horseshoe crabs, especially young ones, swim upside-down. So they 3D-printed some horseshoe crabs and analyzed them basically the way you would analyze an airplane.
Except instead of looking at airflow over a wing, they looked at the flow of water over the shell. But whereas an airplane wing is shaped to generate lift, the shape of the horseshoe crab generates negative lift. This is great when horseshoe crabs come to shore to mate. Which is a really hard position for them to get out of. But say it wants to get over an obstacle, or get away from its siblings.
After all, these are solitary creatures. Sloths are so well adapted to this upside-down lifestyle that their hair grows in such a way that it points towards the ground when they are inverted -- scientists suspect that this is an adaptation that allows the sloths to shed rainwater more easily. The sloths' claws grip branches so well that hunters don't often target the species -- even once the animals are shot, they often continue to hang from the tree, even after their death.
Too slow to catch prey, sloths are herbivores that primarily consume leaves and fruit. Numerous snake species inhabit the trees of the rain forest, many of which spend their nights hanging from branches in hopes of capturing prey. Green tree pythons Morelia viridis and the behaviorally similar emerald tree boas Corallus canninus provide excellent examples of this behavior, though eyelash vipers Bothriechis schlegelii , carpet pythons Morelia spilota and Amazon tree boas Corallus hortulanus exhibit the behavior as well.
Hoping for a rodent or other animal to pass beneath them, these snakes use their venom or constricting ability to subdue prey once grasped. The prey is then eaten while the snake hangs from his perch.
Snakes that hang in this manner usually have very strong, prehensile tails. Using their small but strong rear legs, bats cling upside down to the bark and branches of trees throughout the rain forest.
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