Not all frogs can be sons. Some are your frog grandpa.

Summer is coming, and the sound of frogs is rising. I wonder if you have been scanned by the World Environment Day's "Travel Frog commonweal Tour" these two days? The hot travel frog traveled to China at the beginning of the year and met all kinds of endangered animals native to China.

For example, the Chinese horseshoe crab, which was introduced in the species calendar:

……

Frog "son", what is the misunderstanding?

The introduction of native endangered animals in the game comes from the species calendar, so without saying much here, let's take a look at the frog "son" who was thought to be inconspicuous and attracted attention again.

Wait, who do you call "son"? Who are you calling inconspicuous?

As the largest group of amphibians, there are nearly 5,000 species of frogs in the world, which show their adaptability to different habitats in a variety of magical ways. Some of these species have even lived to be... Your grandfather frog, such as poison frog.

An example of adaptive evolution: Rhacophorus nigropalmatus, a Wallace flying frog in the rainforest of Southeast Asia, can glide from branch to branch on its webbed feet when in danger or foraging, named after the great philologist Alfred Wallace. Picture: endangeredliving.com

When it comes to poison frogs, the first thing that comes to mind must be about 170 species of the family Dendrobatidae. Arrow poison frogs do not synthesize toxins themselves, but obtain toxins from captured arthropod prey and accumulate them, and develop bright body colors as warning colors to tell predators that you can never eat them yourself.

The most toxic golden arrow poison frog, Phyllobates terribilis, has a subcutaneous lethal dose of alkaloid toxin on the surface of mice. Picture: Brian Gratwicke / Wikimedia Commons

This reminds people of the wild clam in The Demi-Gods & Semi-Devils, which is "no more than two inches long and red all over the body." the so-called "king of all poisons"-Zhong Ling's pet mink tasted and died instantly.

But there is a problem here. In addition to being "foodie unfriendly", Mangyan clams can also "spray poison fog" to actively defeat the enemy, which no matter how poisonous the arrow poison frog can do.

Biologically, a phenomenon full of toxins such as arrow poison frogs is called "poisonous", but it can be "venomous" if the secreted toxins can be injected into other organisms by some means to cause damage on their own initiative, such as various poisonous snakes. The difference between the two is clear at a glance in the following picture:

That is the difference between "you bite me, you die" and "I bite you or you die". Picture: snakebuddies.net

"poisonous" is not uncommon. You must have heard of the story of indigenous people smearing arrowheads with the venom of arrow poison frogs, which is why the family Arrow poison frogs are famous. However, Grandpa Frog who can "release poison" seldom heard of it.

Is it true that a frog can release poison?

So far, only two species of Anura (frogs) have been identified as "venomous": Corythomantis greeningi and Aparasphenodon brunoi.

An is Bruno's helmet frog, B is Greene's frog. Picture: Jaredet al./ Current Biology (2015)

The two frogs come from the bizarre continent of South America and, like the Japanese rain frog, the protagonist of the Travel Frog, belong to the family Hylidae of the order Anura. The Bruno helmet frog lives in the tropical / subtropical humid broad-leaved forest (Restinga) along the Atlantic coast of Brazil and, like other species of the same genus, lives in the central pineapple puddle, while the green frog adapts to the semi-arid savanna region (Caatinga) of northeastern Brazil and breeds on seasonal ponds during the rainy season.

A Bruno helmet frog lying in a pineapple. Photo: Instituto ú ltimos Ref ú gios / iNaturalist.org

Both frogs are truly exquisite bones-compared to the round-headed "quack babies" we usually think of as having flat heads, protruding jaws, ossified epidermis and fused with skulls. The generic name of Bruno's helmet frog contains the Greek root spheno for "wedge", and I don't know if it comes from the shape of the head, while the generic name of the green frog begins with "helmet" corytho. In fact, the heads of both kinds of frogs are "protruding and tilting", forming a round plate-like structure.

Ancient Greek Corinthian helmets are also used to describe helmet frogs with anti-bones in the back of their heads. Notice the two protrusions behind the head of the helmet frog, forming the second half of the helmet. Left: MatthiasKabel / Wikimedia Commons; right: Instituto ú ltimos Ref ú gios / iNaturalist.org

What is the evolutionary significance of such skull specialization and shape? The helmet frog has the behavior of "phragmosis": the green frog likes to hide in the cave in the drier environment, when the bone "inch head" facing the mouth of the cave can seal the hole well. On the one hand, it is a defense against potential predators; on the other hand, it also reduces the loss of water in the cave, which helps to keep it moist.

The green frog in the test tube will also plug the opening with a big head. Photo: Jaredet al./ J. Zool. (2005)

It is not only frogs that have this kind of behavior. The heads of the soldier ants of the genus Cephalotes have been specially transformed into the lid of the tree hole, which can be said to be the act of protecting the cave at its peak. Picture: Alex Wild

In addition to being used as a tool for blocking doors, the big heads of the two kinds of frogs have more powerful uses. Bruno's helmet frog and Grimm's frog have sharp bone spines at the front of their heads, which are stained with venom secreted by skin poison glands (granular glands) when they pass through the skin-so they are the real arrow poison frogs. When they are bitten by a predator or caught by a hand, they wiggle their heads desperately to try to stab each other with venom-coated bones. This venom delivery mechanism allows two kinds of "poisonous" poison frogs to enter the "venomous Club", and they really achieve the "release of poison".

Scanning electron microscope photos of skulls of Bruno helmet frog (left) and green frog (right). Picture: Jaredet al. / Current Biology (2015)

Image above: the surface of the skin of the green frog with protruding bone spurs. The lower left and lower right are electron microscope photos of the bone spines of Bruno's armoured frog and Green's frog (marked with *). The lower left arrow indicates the opening of the venom gland on the surface of the skin, and the lower right letter g indicates the venom gland. Picture: Jaredet al./ Current Biology (2015)

It is worth mentioning that, compared with other frogs, the heads of the two poisonous frogs are so flexible that they can even bow their heads at 90 °and observe a moment of silence. This may also be the result of their body structure adapting to their lifestyle. After all, flexible head rotation is beneficial to both hole defense and bone spur attacks.

The venom of frogs should not be underestimated.

The power of their venom attack should not be underestimated: the venom secreted by the head of green frog is twice as toxic as that of Bothrops in South America, while that of Bruno helmet frog is 25 times that of Agkistrodon acutus, and the semi-lethal dose of head venom to mice is only 3.12g.

Looking back, a smile is full of poison. For amphibians with only one cervical vertebra, species that can make this pose are rare. Photo: Instituto ú ltimos Ref ú gios / iNaturalist.org

When it comes to poisoning experts in vertebrates, there are all kinds of reptile snakes, which have "professional" venomous glands modified with salivary glands and connected fangs. In the helmet frog venom, the researchers also found hyaluronidase, which is common in snake venom, which dissolves the cellular stroma in the wound and helps the toxin spread.

Although the equipment is relatively primitive, these amphibians who "rob the enemy with their heads" eventually achieve the same goal as the drug lords, relying on the power of evolution to become the poisonous and poisonous king of frogs.

There is a poem.

Two-ribbed salamander

The head breaks the poison and flows the helmeted frog.

If you get caught on a trip,

Release poison to make the enemy can go home ~

This article is a special contribution to species Calendar, from @ Lupin, author of species Calendar.

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