Shiten: why is it called a "living fossil", and what else is interesting?

One of the oldest creatures on the planet is a shield. No wonder it is called a "living fossil." At the same time, you can’t call the shield rare, you can’t imagine fauna: it lives everywhere in puddles and ponds. And if desired, it can be made a resident of the home aquarium.

Shield Description

People often wonder when they first see the shield: what kind of creature is this? Indeed, its appearance can not be called ordinary. First of all, its features are the property of respectable age. Over the course of 230 million years of being on our planet, the morphology of the shield has not undergone changes.

Shchitni - crustaceans, allocated in a separate family. These creatures are small in size: the length of the body in different species ranges from 2 cm in the smallest to 12 cm in the largest. Sea shields do not exist: they are all inhabitants of freshwater bodies of water, where there are suitable conditions for their life.

The Russian-speaking name of the family is given due to the presence of a shield in these animals covering its body, which perfectly protects the body. Around this shell there are legs, the number of which can reach 70 pairs.
Biologists also distinguish bugs in the typical genus Triops, which in Greek means “three-eyed”. This is due to another feature of ancient creatures - the presence of an organ that looks like a third eye. There are two hypotheses about its purpose: according to one, it is a kind of sensor for tracking light, which helps the animal to navigate in the environment; and the other - that the body performs a primitive chemical analysis of water.

Scutellaria live on all continents except Antarctica: they live in both the Arctic and tropical climates.

Some types of shield

In total, 16 species of bugs are known. But scientists admit that in reality there may be more, because research on these crustaceans is incomplete. Here are some of the most prominent members of the family:

1. Triops australiensis (Australian Shingles). The length of their body is 6 - 9 cm, and the color can be varied: brown, yellowish and even gray with a blue tint. The shell is rounded.
2. Triops longicaudatus (or American). Outwardly similar to the Australian, but its dimensions are smaller - up to 5 cm.
3. Lepidurus apus (spring shingles). Distributed throughout Eurasia. The animal's body is brown-green, enclosed in a light shield, decorated with spots of a darker shade. The creature is about 5 cm long, and the shell ends in an oblong plate. Appear in early spring when the air temperature reaches 15 ° C. Then the shield can be found in puddles, grooves, shallow ponds and in flood meadows.
   

   

4. Triops cancriformis (summer shingles). This species has a massive carapace, under which almost the entire body is hidden. Unlike spring, it does not have a plate at the end of the abdomen. Dark spots covering the shell are larger.

The giant bugs, whose length reached 2 m, is an extinct creature.However, today in the media and on the Internet periodically information appears about huge (50-60 cm) shields that cause panic to local residents in the regions of Russia and Ukraine. Biologists call such rumors exaggeration.

Life Shields

The fortresses managed to survive for millions of years, almost unchanged, thanks to a unique survival system of its kind. They live only in temporary reservoirs of small depth, where there are no enemies. These creatures inhabit only fresh and stagnant water; therefore, species of sea shields do not exist.

When the lowland is filled with water, after 1-3 days cysts “come to life” - a temporary form of life, covered with a protective shell. Nauplii emerge from it (larvae not exceeding 0.5 mm in length). Immediately after birth, they begin to develop rapidly. After going through several developmental cycles, which takes a couple of weeks, the larvae will become an adult ready for reproduction.

It is a mistake to call cysts eggs because they contain an already formed embryo.

Almost all of its life, the shield lives on the bottom of its reservoir, looking for food at the bottom. Their activity lasts day and night, although for full-fledged life, creatures still need sunlight, which easily penetrates deep into a shallow reservoir.

Many are interested in whether the shield is dangerous to people. Despite the seemingly frightening appearance to many, this crustacean does not harm human health.

Shields have one strangeness in behavior, which scientists still have not been able to explain: animals sometimes swim with their belly up on the surface of the water. It has a red color, which makes the creature noticeable to birds, joyfully enjoying themselves with such easy prey. Biologists had a version that such surface exits are needed to produce oxygen when it is not enough in water. But experiments have shown that even with its optimal saturation, the shields continue to behave in a strange way. The only explanation says that ascent is a rudimentary behavior: earlier, these arthropods fed on bacteria that accumulate near the surface of the water.

During the life of the shields, which is 50–90 days, they constantly molt, especially in the first weeks of life. As it grows, the old shield becomes small, and the animal discards it.

Animal nutrition

Shields are omnivores. In the reservoir in which they live, these animals usually close the food chain, taking the place of the main predator. Some species are characterized by cannibalism, but the shields eat their relatives only with a lack of traditional food. In some regions, they are considered pests, because the triops are not averse to feasting on plant foods, causing damage to rice plants.

How do they breed?

The process of propagation of shields is very exciting and is still not fully understood. So, usually in the population there are only females involved in the laying of cysts without the help of males. But whether they are hermaphrodites or they are characterized by parthenogenesis (reproduction without fertilization) is not clear. Also unclear are the reasons why males sometimes appear in the population and bisexual reproduction begins to occur.

Cysts are easily carried by the wind on the surface of the earth, which contributes to the resettlement of shields.

At the edge of the carapace, at the back of the abdomen of the shield, a special sac is attached, in which the egg is hidden. From it, an embryo develops in the shell - a cyst. They are the females that are buried in the ground at the bottom of the reservoir, securing them with a special secret. When this happened, the population is ready for extinction: when the water disappears, the cysts will remain in the ground, continue the genus, when the moisture returns and there will be favorable conditions. They are extremely tenacious, and are able to survive for decades. Cysts are not threatened by drought, increase or decrease in air temperature.

The mechanism of activation of cysts is also a mystery to scientists. It has only been established that this requires a suitable temperature, soft water, light rays and a certain chemical composition of the environment.When these conditions are met, half of the cysts awaken, and the other remains in a dormant state to “secure” in case the population does not have time to postpone new ones due to the drying up of the reservoir.

The content of shields in aquariums

The content of shields in freshwater aquariums is gaining popularity. These are very unpretentious creatures: they feel comfortable in the water of any temperature, undemanding to feed. They are usually sold in a state of cysts, from which then larvae appear. Watching the process is very exciting.

Aquarium-themed shops sell kits with shield cysts for children, because caring for these crustaceans is not a big deal.

In order for the shields to feel comfortable in captivity, you need to create certain conditions for them:

1. Fresh water with a temperature of 15 ° C (for Lepidurus apus) to 25 ° C (for the rest).
2. At the bottom of the aquarium there should be fine sand necessary for the existence and reproduction of the shield.
3. The food is the same as for aquarium fish. These creatures are omnivores, so special treats for them are not required.
4. As soon as the larvae emerged from the cysts, it was recommended to provide them with round-the-clock artificial lighting: this way the development will go faster.
5. The optimal number of bugs in one aquarium is 5 individuals.

But there are some difficulties that may arise in the content. Shitni, being predators, are able to destroy small inhabitants of the aquarium: for example, fish fry. They also sometimes damage the roots of ornamental plants.

Shitnits are unique ancient animals. Their life is so amazing that some of its sides are still a big secret for biologists. Having opened a shield in the aquarium, you can get to know the creature and its habits better: this is a fascinating process that will appeal to both children and adults.