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  • Usually, you think ofaquaticandarborealcreatures as totally separate animals,

  • as different as octopuses and orangutans.

  • But evolution doesn't always result in things that fit into our narrow categories.

  • A number of species have evolved unique physical features and behaviors that

  • helped them make the leap from rivers to redwoods, or oceans to evergreen trees.

  • Like some crabs.

  • And alsofish.

  • If you think of crabs, you likely picture them scurrying along a shoreline,

  • swimming in a sea, or hanging out in some kind of freshwater habitat.

  • But one crab from Southern India lives exclusively in trees.

  • It was described in 2017, in a paper published in the Journal of Crustacean Biology,

  • and those authors described this crab as not only a new species, but a new genus!

  • The animal was identified thanks to the expert knowledge of the region's Kani tribes,

  • who alerted scientists of the crustaceans' existence.

  • That's how the crab got its Latin name, Kani maranjandu,

  • which includes the local words fortreeandcrab”.

  • As for how these crabs live in trees, they have long, spidery legs that end

  • in a sharp hook, so they can wrap around branches and grab trunks with a firm grip.

  • And although it's not clear why they evolved this way, they're making the most of it.

  • They live in hollows as high as 10 meters up, and feed on slugs, worms,

  • insects and also leaves and seeds.

  • They also take advantage of water trapped on leaves and in tree cavities

  • in order to live without having to travel to a body of water!

  • I mean, who needs rivers and ponds when you have

  • your own plant-puddle paradise to hang out in?

  • Alternatively, you could have your own gigantic tree canopy,

  • if you're a wandering salamander, that is.

  • Like many of their relatives, wandering salamanders are commonly found in moist,

  • terrestrial habitats.

  • And a few salamander species

  • migrate up into trees at certain times of the year.

  • But some populations take up residence high in trees, year-round.

  • And we're talking way up.

  • Wandering salamanders make their homes in the world's

  • tallest forest canopy, living on the horizontal branches of giant redwood trees!

  • This seems like it wouldn't work, since most salamanders

  • need a moist environment to keep from drying out.

  • But redwood branches can be two meters wide and are often

  • covered in fern mats that develop a thick soil layer over time.

  • Pieces of bark, broken-off twigs and branches and other debris

  • add to this rich organic layer, making these tree limbs mimic the forest floor.

  • And that's a perfect habitat for moisture-loving salamanders.

  • But considering some of these salamanders have been found more than 80 meters up,

  • the big question is, how did they get there in the first place?

  • Well, they have prehensile tails that can grab onto branches,

  • much like monkeys and opossums do.

  • They also have long limbs and special toe pads that

  • give them the grip they need to climb sky-high.

  • Wandering salamanders have been found in redwood canopies during the whole year,

  • so it's safe to assume they're not trekking down to the ground for long periods of time.

  • Instead, these salamanders hang out in the canopy, munching on juicy springtails:

  • wingless, soft-bodied creatures that look like insects

  • and are found in high densities in redwood canopies.

  • So if you're a wandering salamander, there's just no need to leave your high-rise home.

  • Now, compared to towering redwoods,

  • mangrove trees might not be very impressive in stature.

  • But for a fish, clambering up out of the water into

  • the lower parts of a mangrove forest, even only once in a while,

  • and then staying there for days is a pretty remarkable feat.

  • Mangrove killifish are found in the salty waters of tropical mangrove forests

  • from Florida to South America.

  • And they're actually amphibious, surviving both in the water and on land.

  • In fact, killifish can survive more than two months out of water,

  • as long as it stays moist enough.

  • Now, the problem with most fish is that maybe ironically,

  • they just can't get enough oxygen on land.

  • When they're out of water, their gills collapse,

  • so there's not enough surface area to take in the oxygen they need.

  • But killifish can adapt.

  • For one, they can expand their blood vessels in their skin to allow more

  • blood to flow around and to allow for more gas exchange.

  • And long-term, they can even develop new vessels.

  • When they're exposed to air, they also increase

  • the amount of hemoglobin in their blood,

  • which lets them carry more oxygen around their bodies.

  • Now, you might expect these fish to have unique adaptations

  • like specialized fins to accommodate amphibious locomotion.

  • But strangely, they don't have any obvious physical features that make land travel easier.

  • Instead, they seem determined to hurl themselves out of water,

  • using movements that researchers describe aslaunches, squiggles, and pounces”.

  • Killifish take to the trees for a number of reasons.

  • They might be trying to get away from other fish,

  • or to escape poor water conditions, or sometimes to pursue a meal.

  • And it's not just a few fish here and there.

  • Researchers have found up to 100 fish in a single log!

  • Breaking the mold from their aquatic relatives,

  • these incredible tree-loving animals have developed unique ways to move up in the world.

  • Whether it's spidery legs, finger-like tails, or a determined wiggle,

  • these adaptations are examples of just how flexible and unexpected evolution can be.

  • If you like learning about topics like this,

  • you might want to try out today's Daily Challenges from Brilliant.

  • There are multiple new challenge questions every day that cover all kinds of science,

  • and every challenge gives you all the context you need to solve it,

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B2 中高級 美國腔

树木中生活的水生动物(Aquatic Animals That Live in Trees)

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    joey joey 發佈於 2021 年 05 月 14 日
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