Tag: Biology

Crabs in Love: Monogamous Parasites of Sea Turtles | April 15 2026, 21:56

WOW, it turns out that under the shell near the anus of sea turtles, the parasitic crabs Planes minutus make themselves at home, and there’s only enough space for a cozy duo, so they form a monogamous pair and live happily ever after inside the turtle’s butt (had no idea what to do with this information, so I brought it here). In relation to the turtle, this is commensalism. It’s when it’s good for one (or in our case, two), and the third doesn’t give a damn. I see a scientific paper claiming that they sometimes mistake the turtle for ocean debris, where there’s room for more than one wife, and then, goodbye monogamy. But, at least, no butts involved.

Evolution of Understanding: Brain as a Predictive Model | March 18 2026, 13:29

An interesting philosophical thought came to my mind. What if evolution doesn’t exist in us (not in biological life), but in our system of understanding the laws of the world 🙂 That is, the system of understanding the laws of the world adapts itself so that everything more or less matches up. That is, the brain constructs an internal hallucination and constantly suppresses it in order to minimize the error of prediction. And there’s a big question — does our understanding system strive for truth (absolute correspondence to the world) or just for comfort (so that the picture in the head does not fall apart)?

With this approach, there’s a problem that if you don’t look into the future, then at each iteration, the understanding system adjusts its model so that the prediction works, but simultaneously creates problems for the next iteration, because it has to account for them already. As a result, this layered pie accumulates contradictions and constraints to such an extent that each subsequent theory becomes more and more complex and accreted with a multitude of unexplainable gaps. Dark matter, black hole radiation, gravitational waves, and so forth appear to somehow stretch the owl to fit the globe.

But yes, this is related to the question of whether mathematics was discovered or invented.

Decoding Leather Products: From Genuine to Synthetic | February 23 2026, 18:11

Today I learned how the hierarchy of leather products is actually structured. Everyone knows that faux leather is completely synthetic; it’s a layer of polymer on a fabric base. There is also cheap leather, often labeled as Genuine Leather, which technically remains an animal-derived product. It turns out to be the lower, looser layer of the hide, which on its own lacks strength or aesthetics, so it’s turned into a sort of sandwich, encased in a thick layer of plastic (polyurethane) with embossing. Essentially, cheap leather is split or compressed leather scraps (Bonded leather or bi-cast/tri-cast), glued together with plastic. It’s essentially akin to plywood or particle board.

How such leather is produced: 1) Leather scraps and waste are taken 2) they are shredded into small fibers 3) mixed with a binder – polyurethane or latex – resulting in a mass similar to pulp 4) this mixture is evenly distributed on a substrate, which typically serves as fabric or paper material 5) a roller or plate with a pattern mimicking natural leather is then pressed onto the surface of the mixture, creating a texture reminiscent of real leather. 6) After drying, a protective coating is applied to enhance the strength, wear resistance, and appearance of the material.

Expensive leather is called Aniline or Full Grain. Essentially, it is made from the top part of the hide (which is exposed to air on the animal). It is dyed with transparent dyes, and contains no plastic. Nubuck or suede is part of the hide which, excuse me, comes in contact with the flesh.

Many also judge the quality of leather by its smell, thinking that a distinctive aroma is the main sign of authenticity and high class. This is easily mistaken. The scent we associate with expensive leather is often the result of chemists’ work. Manufacturers of cheap bonded leather products use special fragrance sprays that mimic the smell of expensive tanning. Real high-quality leather, such as vegetable-tanned leather, smells more like wood, oak bark, or mimosa, because these substances are used in its processing.

Another professional secret concerns the edges of the product. If you see that the edge of a bag or belt is neatly filled with a thick layer of “rubber” or paint so that the structure of the layers is not visible, this is often not done for design’s sake. Such a technique helps to conceal that very plastic sandwich which makes up the material. Craftsmen working with truly high-quality Full Grain leather often leave the cuts open or just slightly polish them with wax, because they have nothing to hide — the fiber structure of such leather is equally dense throughout its thickness.

Understanding Fever: A Physiological Defense Mechanism | February 17 2026, 09:00

I’ve only slightly (hopefully) gotten sick here and realized during the process that many people around me take pills for a minor onset of fever, considering it normal.

I’m sharing my understanding of the process, which should be very close to scientific. When an infection penetrates the body, foreign bacteria or viruses enter the bloodstream, which the immune system attacks. During the attack, signaling molecules are produced, the purpose of which is to declare a general alert throughout the body. Specifically, cytokines are produced, which also inform the brain (hypothalamus) that action is needed. Pyrogens (fever-inducing agents) include cytokines and external pathogens. The hypothalamus activates a fever through the synthesis of prostaglandins. Why: at a temperature of 38.5°C, the immune system becomes more active, antibodies are produced in larger amounts, microbial reproduction slows down, and some viruses do not reproduce.

If you consume, for example, Ibuprofen, it blocks the enzyme (COX) that creates these prostaglandins. Meaning, the pyrogens are still in the blood, but the brain “can’t hear” them and doesn’t raise the temperature.

There are only two cases when you should reduce fever: if you truly feel awful, have a severe headache, vomiting, etc. Unnecessary stress does not help the body. And if the temperature exceeds 39°C. At that point, the harm from high temperature outweighs the benefits. Even then, there are so many “buts” that a doctor should make the decision. For example, if the heart is problematic, these are special cases.

Oh, here’s something else interesting. Why when the temperature is high you feel “cold” and want to cover up. In the hypothalamus itself, there’s something like a thermostat, normally set to 36.6°C. When pyrogens arrive, it raises the temperature through prostaglandins, but since it’s the brain, it immediately cranks up its own “normal temperature” in its thermostat to, say, 38.5°C. As a result, a body temperature of 37°C suddenly feels low, and it feels like “it’s cold around, need to cover up.” Covering up is passive thermal insulation, and generally, it helps to more quickly raise the temperature to the target level. Later, when the temperature reaches 38.5°C, the chills may disappear (unless the hypothalamus further raises its thermostat). And when the temperature plateaus, around 38.5°C, covering up is harmful.

When the temperature starts to drop back, the internal thermostat switches to 36.6°C, and to cool down faster, the body produces sweat. So, if you’re sweating, it’s a sign of recovery.

(Well, what else is there to do at four in the morning, when because of all this, I can’t sleep)

Capuchins in Costa Rica: Monkey Antics and Natural Insecticides | January 03 2026, 20:55

In the photo — a white-shouldered capuchin. Took this pic in Manuel Antonio, Costa Rica a week ago. At that moment, a troop of at least 40-50 monkeys stormed the beach: they were everywhere. Scrambling through bags, one started to pull out a towel but couldn’t manage it. They’ve already figured out how zippers work. Capuchins have rather scary sharp teeth, but it seems they don’t use them on people without reason.

While preparing this post, I decided to read up a bit about them. Turns out, they practice so-called “self-anointment” — they rub their fur with crushed ants or centipedes. The chemicals (like formic acid) released by these insects act as a potent insecticide, deterring parasites. Also, if a capuchin finds a lemon or wild onion, it will crush them into a pulp and thoroughly “perfume” itself with the juice.

Capuchins have very complex social bonds, which they maintain in very specific ways. They have “trust testing” rituals that might seem odd to a human. Two monkeys can sit and alternately stick their fingers deep under each other’s eyelids. This is the supreme form of trust — “I allow you to hurt me because I trust you.” Also, they can insert their fingers into each other’s nostrils and sit like that for a long time, entering a sort of trance. I’ll put links in the comments.

Dangerous Beauty: The Spiked Palms of Costa Rica’s Jungles | January 03 2026, 02:35

A very typical palm for Costa Rican jungles. Hugging one of these is a bad idea. These black spikes are incredibly sharp, hard, and can reach lengths of 10-15 centimeters. They are arranged in dense rings along the entire trunk. The most treacherous thing about these spikes is their fragility and dirt. If a person or animal runs into such a spike, the tip easily breaks off and remains deep in the wound. Since in the tropical climate these needles are home to millions of bacteria and fungi, a deep splinter almost guarantees a serious, painful, and slow-healing inflammation.

The density of the needles varies, sometimes the trunk is not visible behind them.

Such was the case in the series Pluribus.

Exploring Nature’s Design: How Insect Bites Transform into Palm Leaf Patterns | January 03 2026, 02:15

This is a palm leaf in the jungle about 60-70 centimeters wide. I stopped and wondered how it is that beetles chew through to create such a pattern.

I mean, when you think about it, the answer is obvious. They make one hole in a folded leaf, and then the leaf unfolds, creating many holes – like a paper snowflake. Upon contemplating this, I realized that palm leaves grow as a “cigar,” a rolled-up tube. I didn’t know this, but the very regular holes leave no other explanation.

But there is another thing – the holes are a bit large for a beetle or an ant. Obviously, if they were to eat a leaf that’s rolled up into a tube, they would end up biting through several layers at once, because if they ate the layers separately, the structure wouldn’t appear as regularly. But their mouths aren’t huge enough, of course, to eat such multi-layered leaves.

Apparently, an ant or beetle was eating the leaf while it was still small. Afterwards, the leaf grows evenly throughout and, obviously, the hole increases along with the leaf. The holes don’t heal; the leaf is alive and grows. A hole made by a beetle could initially be only a couple of millimeters in size, but then it grows to the size of a finger.

Exploring the Golden Carpenter Ants of Costa Rica | December 31 2025, 14:28

Golden Carpenter ants from my last trip to Costa Rica. They are huge, about 1.5cm. They build nests in wood. Unlike termites, they don’t eat the wood, they just make a home for themselves there. They don’t have stingers, but if disturbed too much, they can bite with their jaws (as seen in the photo on the left) and inject formic acid. Their distinctive feature is a golden abdomen. I’ll write about other notable leaf-cutter ants next time, half of my phone is full of them.