The number of taxonomically defined animal species is around 1.5 million. These are classified into 32 phyla according to their distinct features. One of these is the phylum of Tardigrada.

These cute, tiny water creatures were discovered in 1773 by Johann August Ephraim Goeze. Despite being aquatic, these animals were called “water bears” because of their legs; and because of their resemblance to pandas, they were named “Tardigrada,” meaning “slow stepper,” by the Italian biologist Lazzaro Spallanzani. Tardigrades also look like dwarf rhinos and armadillos. There are about 1,000 different species in the Tardigrade phylum.

Tardigrades live in habitats with variable amounts of humidity, from high mountains to deep oceans, and from polar regions to the equator. They are especially found in lakes, freshwater springs, or on stone walls, mosses, lichens, leaves, and litter.

As cute, charismatic, miniature animals, tardigrades can be seen under a microscope. The length of adults can reach 1.5 mm, while the smallest ones are under 0.1 mm; their larval length is only around 0.05 milimeters. Their body is covered with a strong but elastic material.

Animals grow in two ways: via an increase of cell numbers or the enlargement of a single cell. In Tardigrades, generally the latter is observed. These animals possess a hard external skeleton, like insects, and this structure changes as they grow.

Their bodies are composed of five sections: a distinct head in addition to four body parts, each equipped with claws. They walk using the short, blunt feet under their bodies. Their clawed legs help them cling to sand particles or plant surfaces. Their hind legs are used for snatching and slow acrobatic movements. They have a sharp mouth, called a “stylet,” which enables them to consume plant cells, algae, small invertebrates, and even their own kind.

They are provided with anatomical and physiological features similar to larger animals, including a digestive track and system: a mouth, esophagus, stomach, small intestine, anus, well developed muscles, a pair of abdominal nervous systems, and a brain. The body lumen of Tardigrades are filled with a fluid that is in contact with every cell and this provides them with their necessary nutrition and gas exchanges without the need for a circulatory or respiratory system. Their respiration occurs throughout their body surfaces. Because of their physiology and ability to quickly reproduce, Tardigrades can be used as a model organism for education and research. The cell count of certain species of Tardigrades at birth never changes during their lives. While some species contain around 40,000 cells, some have fewer. Their reproduction can be sexual, but it also can occur via parthenogenesis (offspring development without the fertilization of the egg).

Tardigrades: Organisms of extreme conditions

Tardigrades are created with a resistance to a wide range of temperatures, pressures, and radiation. Therefore, they can live in environments where many living things die. They can survive a temperature of 150 C for minutes, and can also live at minus 200 C without suffering any damage for days; they can even stay alive at temperatures near absolute zero (−273 C).

Some Tardigrades can live at extreme low pressures, including situations approaching a vacuum, or at extreme high pressures, such as 600 times the normal atmospheric pressure. This pressure is six times the pressure present at the depths of the Mariana trench, the deepest part of the Earth’s oceans (roughly 11,000 meters). This was discovered when Tardigrades were taken to space and exposed to different pressures. When brought back to Earth, they were still alive.

They can also survive in environments with no humidity for 10 years, and they can stay alive in places where radiation is 1,000 times more (5000 Gy to 6200 Gy) than many organisms can endure (10 Gy is fatal for humans).

Hibernation – a dead phase

How does a Tardigrade stay alive in detrimental conditions?

When they are exposed to conditions unsuitable for life, they enter a semi-dead phase called Cryptobiosis. One of the most distinct changes during this state is that their metabolic speed slows down to near zero, and they experience programmed dehydration. In very low temperatures, Tardigrades’ water ratios drop from 85% to 3%. This way, damages that can occur by freezing are prevented. As is well-known, the main hazard during freezing is the cell membrane damage caused by the crystallization of cellular water.

During the dehydration stage, trehalose sugars are synthesized (this also happens when Tardigrades are faced with low temperatures). This sugar prevents possible damages to the cell membranes during freezing and water loss. This sugar is very intriguing for the pharmaceutical industry because of its potential use in the prevention of freezing-related damages in organ transplants.

Another benefit of dehydration is resistance to radiation. This is because reactive molecules generated in the cell by the effects of radiation cannot cause a reaction in a dehydrated medium; due to the low water concentration, the possibility of harmful reactions drops.

Cryptobiosis does not only take place during dehydration. It also happens during periods of low temperature (cryobiosis), high salinity (osmobiosis), and low oxygen. By being able to hibernate, Tardigrades are important for space research. Maybe during interplanetary trips, passengers could be hibernated by freezing.

Tardigrades could have other uses for medical purposes. Certain disease-causing microorganisms could be dehydrated without killing them via Cryptobiosis. This way, “weakened organisms” contained in vaccines get to be stored in a dry fashion, eliminating the need for freezers, making them easier to store and distribute. Similar technologies could also be employed for the conservation of seeds, sperms, blood, and various nutrients.

Cats are born with their eyes closed and no sense of hearing, but they improve their abilities over time. Their sense of vision develops every day and babies require approximately five months to be able match the visual capabilities of an adult cat. To augment their abilities, kittens have incredible senses of smell.

This can be witnessed when kittens are fed by their mother. A mother cat designates a nipple for each baby. When kittens that seem to be fighting each other during nursing are observed carefully, one can see that each newborn is trying to reach their own designated nipple. They find it through their incredible sense of smell.

As mentioned above, though cats are friendly, they will occasionally misbehave. This naughtiness hints that their predatory instincts are still intact. The development of their hunting ability is honed through games and aided by the fact that kittens do not have feelings of fear before they are six weeks old. During this short time, they are required to obtain sufficient experience to survive. When they are one year old, a cat will have all their adult characteristics.

One defining trait of cats is their flexibility. Cats have 40 more bones than humans and this enables them with such flexibility. Most of these bones are located in the spine and tail sections. The advanced flexibility of the lumbar bones provides cats with agility. The disks positioned in between vertebrae are tighter than the disks of human vertebra. This feature naturally enables cats to move uniquely and flex their body up to 11%.

This also means that when a cat encounters prey, it can estimate the distance at a glance and can jump 1.5 meters without needing any speed. The human equivalent would be jumping 8.5 meters without a running start. Another aspect of this flexibility is that cats can go through any opening that their heads fit through because they lack a clavicle. They also have powerful legs and their paws are created in a way to contract within a fraction of a second upon landing. Their retractable claw acts as a hook when protruded completely and permits them to climb and grasp vertical surfaces.

We often overlook cats. They’re pets and companions. But in truth, they’re so much more. Blessed with some incredible traits, cats are actually marvels of creation.

Animals with nine lives!

When falling, cats open their legs sideways to generate a parachute effect. By doing this, they control their speed to prepare for a soft landing and land on their feet with remarkable reflexes. A fluid in their inner ear moves when they are not in balance and they develop a reflex to help them land on their paws. There is one problem: they cannot relax their muscles completely when falling from places that are not high enough, disabling the parachute effect. The risk of injury for cats is lower if they fall from the thirty-second floor (100 m) than if they fall from the seventh floor, experiments have shown.

Sensing earthquakes

Cats have many senses that are significantly stronger than human senses. Sight and hearing, which are required for hunting and survival, are the two basic senses more advanced than the rest. Every sound they hear feels very powerful. For instance, the tic-tac sounds of a clock are four times stronger to cats than to humans. Cats are granted the skill to distinguish high frequency sounds that humans and even dogs cannot notice. This skill enables them to separate between the voices of people. In addition, there are more than 20 muscles in a cat’s ear. This enables the independent movement and control of each ear. Thus they can determine the source of sound with speed and precision, and detect the exact location of prey from just a small movement in one-sixteenth of a second.

These cute animals are skilled at feeling the weakest vibrations. With this skill, cats are considered to have the ability to feel earthquakes a couple of days in advance, like some other animals, though it is not exactly understood how this occurs. It is possible that these animals can even sense vibrations too small to be captured by measuring systems. Despite all the efforts of scientists, they struggle to forecast the timing of earthquakes even with modern technological devices. However, many animal species display abnormal behaviors hours and even days before an earthquake. This remains a mystery how animals react in such a way. Therefore, data acquired with detailed studies performed on animals will surely provide many benefits in terms of accurate prediction of earthquakes.

A cat’s eye

Cat’s eyes are also created in a fashion to let them focus on their prey. Sharp vision is as important as the sense of hearing for a night hunter. During hunting, the target is in focus and everything else is blurry. Cat’s eyes, when compared to human eyes, contain many extra cells in charge of sensing light, including a crystal layer behind the retina that absorbs all available but unused light. Like other nocturnal animals, cats have the layer called “tapetum lucidum” in their eyes. This layer reflects light like a mirror, and for this reason, cat’s eyes shine in darkness. This reflection effect even permits cats to utilize the lowest level of light possible. The iris can adjust its width depending on the light’s strength, just like the diaphragm of a camera; this allows cats to distinguish their surroundings in the dark. Another feature of Tapetum lucidum is that when light strikes a cat’s eye from an angle, it causes the eye to shine, even in dim light.

There are limits to cat’s night vision powers – and they make up for this with their whiskers. A cat’s whiskers enable them to sense the slightest changes in the air. These facial hairs work like a radar system, helping them to identify the outline of objects that they barely see.

Sensing fear

The one sense cat’s lack when compared to humans is their sense of taste. Cat tongues have 25% less papillae (taste buds) than human tongues; they do not enjoy sugary foods. The pleasure these animals get from eating is related to another sense granted to them in addition to smell and taste. Cats have an organ located at the frontal section of their palate which is lacking in humans. It’s called the Jacobson organ. Chemical signals enter the mouth and end up in a small capsule after passing through the opening in between two palates located behind the front teeth. These chemical cues are stored here. This means that they can taste chemical signals. Even though it is not possible for cats to compete with dogs in terms of olfactory senses, this ability is fourteen times more powerful than human’s sense of smell. This skill is used for social communication. It’s likely that cats recognize people through their scents. While a human nose houses only 5 million olfactory cells, there are around 200 million sensory cells placed in the small noses of cats. A significant portion of their brain is ready to sense, assess, and respond properly to chemical signals.

Tidy animals

Cats dedicate a major portion of their time to cleaning. These animals truly enjoy their cleaning sessions. It takes a long time to fix their tangled fur. In addition, their fur must be bright and well cleaned in order to protect their body against exposure to external elements like cold air and rain. Cats lick their paws to use them like gloves to clean their faces. Their tongue is long and there are small projections found in the rear section. This section, rich in buds, acts like a brush and enables them to better clean their fur. The tongue triggers the oil glands at the base of each hair. A fluid is secreted that makes a cat’s fur waterproof.

Despite their fur, cats do not get heat exhaustion. The hairs not only prevent them from feeling intense heat, but also keep them warm by insulating them from the surrounding environment. These animals also display strong resistance to pain. This results from their high levels of endorphin, the hormone for pain reduction.

Sleeping beauties

Cats spend 2/3 of their lives sleeping. Therefore they are often used as experimental animals for sleep-related research. It is possible to say that we owe most of the information regarding sleep mechanisms and the effects of sleep to cats.

Natural navigation

Cats are created with the perfect tool for navigation. Experiments have shown that they can cover miles of road to return back to their home. It is thought that these animals find their way by employing the sun and the Earth’s magnetic field. What is hard to explain is how they happen to find a new house when their owners move. It is still unknown whether this skill originates from a certain sensory mechanism or whether cats are provided with even sharper senses than we think they have. Whatever the answers may be for these questions, we can simply conclude that cats are animals which have been truly blessed in a way that allows them to adapt to their environments.