It has a detachable butt, and a brain on its butt! | Natural Trumpet

Welcome to the 48th issue of the Nature Trumpet column. In the past half month, we have collected the following natural news and research worth reading:

1) Anglerfish: Swimming upside down for their entire lives

2) Performing Monkey: High pressure, unhappy

3) Sea worms: Swimming and then their butts sneak away

4) Elephant: The rumbling sound that humans cannot understand is the name of the elephant

5) Dolphins: Highly intelligent pirates who steal crab bait every day

6) Bats: Their penises are too big, so they can only mate by contact

Anglerfish swimming upside down

Some fish spend their entire lives swimming upside down!

Image | Wikimedia Commons

When we think of anglerfish, or lantern fish, we probably think of something like this — and scientists used to think so, too — so much so that when they saw an anglerfish swimming upside down, with its lantern hanging upside down, they thought it was just a slightly rebellious fish that had suddenly decided to think about its life upside down today.

Anglerfish: Not dead, just a little sad | References [1]

However, when scientists studied more videos recorded by underwater cameras, they were surprised to find that some anglerfish had been swimming upside down .

This is not a special posture for them in a certain state (such as sleeping) - whether they are foraging, sleeping or hanging out on the seabed, they always maintain this inverted posture. In one video, an anglerfish was hit by the propeller of a submarine and turned upside down. It turned back immediately and returned to the inverted posture with its belly facing up.

Jiang Taigong fishing (inverted version) | References [1]

Scientists speculate that they swim upside down because it helps them find food .

The anglerfish's "lantern" is actually a bioluminescent natural bait that can attract prey. When they are upside down, the upper lip connected to the "fishing rod" can more easily control the position of the bait; and this way the bait is farther away from the mouth, allowing them to catch larger and faster prey. Scientists have even found a squid, known as the "Ferrari of the deep sea", in the belly of an anglerfish swimming upside down. It seems that the handstand stunt is very useful.

At this time, a handsome guy passed by doing a handstand | National Institute of Water and Atmospheric Research

Monkeys are under a lot of pressure

Monkeys who are forced to perform are under a lot of pressure.

Rhesus monkeys are small primates that are smart and cute, but they are often captured and trained for performances. Monkey dancing has even become a special attraction in many Middle Eastern countries. Monkey trainers take monkeys away from their mothers when they are very young, tie them up with collars, and train them to dance. After they are trained, the monkeys are taken to the streets to perform in public, attracting passers-by to throw in a few coins.

Monkeys forced to dance for money in Pakistan | Rangbaz / Wikimedia Commons

A recent study analyzed the status of rhesus macaques forced to perform in Pakistan. The researchers collected hair samples from 50 performing monkeys and 77 monkeys living in non-perturbed sanctuaries.

Comparisons show that the cortisol levels of performing monkeys are much higher than those of monkeys in the reserve, indicating that performing monkeys are constantly under fear and stress ; their testosterone levels are also lower than those of their counterparts in the reserve. More than half of the monkeys showed stereotyped behaviors or even self-harm when forced to perform. Their "cute and well-behaved" appearance in front of passers-by is actually a manifestation of their extreme fear.

A monkey begs passers-by for money with a jar on its head, but beneath its docile appearance lies fear | Tahsin Shah / Wikimedia Commons

Many monkey trainers were brought into this industry by their families when they were very young. They cannot leave the profession without permission, and part of their income needs to be handed over to the leader of the small group. They know that their monkeys are not living well, but monkey dance performances are their only source of income. To save the monkeys who are forced to perform, the government first needs to provide these people with an alternative .

Sea worms leave the body

The "butts" of some sea worms have a mind of their own - while they swim, the back half of their body just moves away on its own.

The English name of this sea worm is literally translated as Megasylllis nipponica, which belongs to the family of annelids. Their dropped "buttocks" are actually a reproductive stem filled with sperm or eggs . This structure will leave the body when it swims and look for the reproductive stems of other opposite sexes, and the two parts will mate to produce offspring.

Sea worm and its removable butt | References [3]

When we say "sea worms' butts have minds of their own," we're not kidding— their reproductive stems really do have brains ! Inside the reproductive stems is a miniature brain, and even eyes, tentacles, and muscles. However, since they are built for reproduction, this structure's sexual organs will fully develop first, leaving the front half of the body and dying once mating is complete.

The buttocks that fell off the male, the red ones are the eyes | Reference [3]

Now that the butt has a brain, will it rebel and stop mating after leaving home to live a carefree life? That won't last long, because the reproductive stem is not equipped with an oral cavity or digestive system, and is equivalent to a disposable battery, which will die soon .

The reproductive stem of sea worms is not only detachable, but can also grow a new one after it falls off . As long as the sea worms eat well and grow their bodies, new reproductive stems will grow again until they are ripe again and go out to perform mating tasks.

Elephants naming each other

In addition to humans, researchers have discovered another animal that names each other: elephants.

In Kenya, researchers discovered that African elephants have names based on the sounds they make. They recorded 625 elephant calls and were able to identify unique names for 119 of them .

Elephants have their own names | Pixabay

The process of finding out who is calling what depends entirely on observing the behavior of the elephants: when an elephant in the herd makes a rumbling sound, and an elephant happens to be left behind, this unlucky elephant may call out this name (imagine that you find your friend missing outside and you would also call out his or her name); when an elephant makes a rumbling sound, another elephant approaches, which also means that it may have heard its own name (elephant: why are you calling me over?).

But is it possible that the rumble is just a call with a special meaning, such as a greeting, help, or a warning about predators? The researchers found that the rumble is different from these universal calls - when the researchers played recordings of various rumbles to the elephants, they responded more strongly to the sound of their own names; and when different elephants made the same rumble, it was always the same elephant that responded, just like different people calling Zhang San, and the one who turned back was always Zhang San.

This study shows that the communication between animals is much more complicated than humans imagine . When they communicate with sounds, they sound just the same as meows, woofs, and rumbles to us, but in fact, they are just encrypted conversations that we can't understand. Not understanding is not necessarily a bad thing, maybe your cat is cursing at you.

Dolphins steal crab bait

Dolphins have a new profession - bandit.

Recently, dolphins near Australia have learned to open crab cages and steal the crab bait inside . Humans often appear in this sea area, and dolphins have become accustomed to the presence of humans. Now, dolphins watch humans put snacks within their reach. Who can not be tempted!

The real thief in the ocean | | Dolphin Discovery Centre Bunbury

The dolphins and the fishermen had a battle of wits and courage. In the most primitive crab traps, the bait is hung on the hook in the middle of the trap. The dolphins can just reach in and tear the bait fish off the hook. In order to defeat the dolphin thieves, the fishermen improved their method and put the crab bait under the trap. But they didn't expect that the dolphins immediately figured out a way to deal with it - they could use their mouths and bodies to cleverly turn the trap so that they could eat the food below.

Some fishermen came up with a solution: put the crab bait in a locked bait box, so that the dolphins couldn't steal it! However, the dolphins' stealing skill points were refreshed again. This time they learned to use their teeth to open the bait box and eat all the fish inside.

Dolphin: I'm just eating my own food! | Dolphin Discovery Centre Bunbury

However, when dolphins steal crab bait, it's not just the fishermen who get hurt, and it's not good for the dolphins themselves. Many people worry that dolphins will get tangled in nets and get hurt when they steal crab bait, or that they keep stealing crab bait and eat too much unhealthy food. So some animal protectionists worked with fishermen to develop a new mesh bait bag with a metal hook on it to seal it tightly. The dolphins couldn't open the new bait bag, so they had to leave in shame - but who knows if they will come up with new ways to steal.

Bats do not mate with penetration

The big brown bat has extra-large male genitalia and can mate for up to 12 hours at a time, but it is the only known mammal that can mate without penetration .

Big brown bat (Eptesicus serotinus) | Alona Shulenko

The average length of a male big brown bat's penis is 16.4 millimeters, seven times the length of a female's vagina; when engorged, the penis is 7.5 millimeters wide, also seven times the width of a female's vagina. Ultimately, the male big brown bat's oversized penis simply can't fit into a female's vagina .

The Big Brown Bat's Extra-Large Penis | References [6]

Scientists initially wondered if the big brown bat's penis hardened after penetration, like a dog's. But they observed 93 copulations and found that none of them were penetrative, and that the penis hardened before contact with the vagina. During copulation, the male grabs the female by the scruff of the neck, presses his penis against the outside of the female's vagina, and begins completely still copulation —usually for just a few dozen minutes, but the longest one lasted 12.7 hours. After copulation, the female bat's belly hair is wet, and there may be semen on it.

When the big brown bat's penis is erect, it is 22% of its total length | Reference [6]

What is the purpose of a large penis when it is not inserted during mating? The female has a tail membrane in her lower body to resist the male and avoid mating, and the role of the male's large penis may be to break through this membrane. There is also a hollow structure on the back of the penis, which can act as a suction cup during the long mating time.

References

[1] https://onlinelibrary.wiley.com/doi/10.1111/jfb.15609

[2] https://www.sciencedirect.com/science/article/pii/S0168159123002836

[3] https://www.nature.com/articles/s41598-023-46358-8

[4] https://www.biorxiv.org/content/10.1101/2023.08.25.554872v1

[5] https://www.livescience.com/animals/dolphins/watch-dolphins-raid-crab-pots-off-australia-in-never-before-seen-footage

[6] https://www.sciencedirect.com/science/article/pii/S0960982223013040

Author: Cat Tun

Editor: Mai Mai

Source of title image: Reference [3]