We all know animals that, without wings, are capable of flying or gliding for more or less long distances. We speak of “flying” when an active and propelled movement is made, such as a powered airplane, a helicopter or a propelled rocket; and we refer to gliding when the movement is maintained with only passive lift, as would happen with a paper airplane. When it comes to gliding animals, reference is always made to flying squirrels or flying fish . But there are many more that have developed evolutionary strategies that allow them to glide long distances, and in some cases, even fly without wings. Today we bring you five amazing animals that manage to move through the air without wings.
Gliding lizard, the dragon that glides with its ribs
The common gliding lizard ( Draco sumatranus ) is a peculiar small reptile endemic to the archipelagos of Southeast Asia, with a number of extraordinary adaptations.
On the one hand, it has membranous expansions on the sides of the body, called patagios, which are supported by the thoracic ribs. The structure of these bones is elongated, and the muscles , which in other animals allow the rib cage to expand and contract, in gliding lizards have become specialized to allow the transformed ribs to open or close, extending or folding the ribs. patagos.
Still other membranes extend under the throat, sitting on elongated, movable cartilages that arise from the hyoid bone . It is thought that these expansions on the sides of the throat, which can also be folded, would act to improve balance, stability and make it easier for the animal to gain altitude during gliding. In addition, the hind legs are also flattened and combined with expanded lateral scales at the base of the tail to improve the effective aerodynamic surface that facilitates the rudder function.
Giant Manta, the largest glider on earth
The largest animal in the world capable of gliding is found in the sea. We are talking about the giant manta ( Mobula birostris ) , a huge fish that can reach a wingspan of up to seven meters and weigh three tons.
To prepare, the manta folds its mouth appendages against its mouth and flattens its body . It is then propelled with the power of its fins, at great speed, breaking the surface of the water. Already in the air, it continues flapping , while it plans until it falls back into the water.
The reasons why manta rays make these long leaps out of the water are unclear. They are unlikely to do this to escape predators, and since they feed on plankton, they do not do this to feed either. They have proposed, as a hypothesis, that it may be due to a form of communication or social display , although it is more likely that it is simply a way of saving energy . Although the jump itself involves an effort, moving through the air implies less friction, and, therefore, less resistance than moving through the water.
Spiders, pilots of flying machines
Many species of spiders move by the wind, but they do not have bodily adaptations to do so, instead they make a vehicle out of their silk . They first look for high ground from which to launch. There they prepare their flight equipment, built exclusively with silk. They fix the silk at a point, and weave a series of filamentary structures that, when the time comes, detach from their moorings and fly through the air, with the spider suspended from them. Spiders have been found floating at an altitude of 4,000 meters , and have been known to travel hundreds of kilometres.
The technique of these spiders has traditionally been compared to the operation of a paraglider. Of course, the wind would have a lot to do with it, and it does during the flight; however, it has been observed that spiders have a preference for taking flight when the wind is calm. What they do is not actually float in the wind, they use a very different system.
The atmosphere is an electrically charged fluid, something we see very well during a storm, and spiders can sense it. Spider silk also has a certain charge, which allows the strands to stay apart from each other without becoming entangled, due to the effect of repulsion, and also generate enough force to take off and fly.
The serpent that plans changing its shape
Among animals capable of gliding without wings, snakes of the genus Chrysopelea have one of the most complete adaptations. In the tree, its shape is that of a normal snake, with a circular section. But when it propels itself into the void and extends its body to glide, it not only glides lengthwise, but also changes its shape.
It extends its ribs, acquiring a very flattened cut, concave on top and convex almost flat on the belly. That peculiar shape, added to its great length, gives it an unintuitive but very effective aerodynamics . It is really remarkable the fact that the snake does not preserve bilateral symmetry —from left to right—; its flight is undulating as would its movement on land, and as it arches from one side to the other, the side of the body that is in the inner curve of the undulation is thicker than the outer side. However, it does have longitudinal symmetry, which makes it unique among gliding animals, and provides it with enviable maneuverability, without the need for a rudder.
The elusive flying squid
The flying squid of the family Ommastrephidae are perhaps the most fascinating animals capable of flight. As far as we know, flying squid begin their takeoff with their fins and arms folded, taking on the shape of a rocket . Once airborne, they spread their fins and arms, expanding the membrane between them. They position them in such a way as to create a lifting surface . But what’s most fascinating is that they don’t just glide, they actually fly using a system that no other known animal uses: jet propulsion .
In the anatomy of a squid, as in the rest of the cephalopods, there is a cavity called the mantle , which can be filled with water, with an outlet to the outside called a siphon , through which to expel that water under pressure. While in flight, flying squid have some ability to maneuver , either by changing height or direction, directing the jet in different directions at will.
When the water in the mantle is depleted, they begin to glide . Even in this phase, it is thought that he can direct flight at least laterally, by changing the angle of his arms. As it approaches the surface it retracts its fins and arms, entering in the same rocket-like shape with which it emerged. The re-entry is clean, hardly causing splashes or rebounds.
It is estimated that, in this way, squids can fly more than 30 meters away in just 3 seconds, a remarkable feat given that we are talking about animals whose bodies — not counting their arms — measure less than 15 centimeters. of length.
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REFERENCES:
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Holden, D. et al. 2014. Aerodynamics of the flying snake Chrysopelea paradisi : how a bluff body cross-sectional shape contributes to gliding performance. Journal of Experimental Biology, 217(3), 382-394. DOI: 10.1242/jeb.090902McGuire, J. A. et al. 2011. The Biology of Gliding in Flying Lizards (Genus Draco) and their Fossil and Extant Analogs. Integrative and Comparative Biology, 51(6), 983-990. DOI: 10.1093/icb/icr090Morley, E. L. et al. 2018. Electric Fields Elicit Ballooning in Spiders. Current Biology, 28(14), 2324-2330.e2. DOI: 10.1016/j.cub.2018.05.057Muramatsu, K. et al. 2013. Oceanic squid do fly. Marine Biology, 160(5), 1171-1175. DOI: 10.1007/s00227-013-2169-9Rayner, J. M. V. 1986. Pleuston: animals which move in water and air. Endeavour, 10(2), 58-64. DOI: 10.1016/0160-9327(86)90131-6Â
