What do crabs eat? Soil and plants
These animals are classified as arthropods, class - crustaceans. The crab has five pairs of limbs, one pair is transformed into claws, they are more powerful and larger than the other limbs, sometimes this pair has significant asymmetry. This happens because during rival fights, or while defending its life, the crab loses one claw. A new one grows in its place.
The crab has a muscle that certain moment begins to contract strongly and the tissue ruptures. There is no major blood loss and the bleeding stops quickly.
The legs of different crabs may vary in shape and size. Some have the last pair in the form of oars - they help when swimming.
The body shape of crabs is special - it was given the name - crab-shaped. Sometimes it's more round shape, sometimes square or similar to a triangle. The body is slightly flattened, the abdomen smoothly passes into the so-called cephalothorax. This name is formed due to the fusion of the head and chest parts of the body. At the top there are pronounced eyes on stalk-like processes.
The body is covered with a hard cover - chitinous cuticle, which contains organic matter– chitin. The chitin cover serves as the crab's exoskeleton. He protects internal organs animal from various external influences. During the molting period, the crab's shell becomes soft. A new, durable cover is formed under it, and the animal sheds the old one. The shell has a name - carapace, its size and shape are different, depending on the type of crab.
At the moment of molting, the crab experiences a large expenditure of energy.
It moves with the help of four pairs of hind limbs. Crabs have a special gait; they move sideways rather than straight. Despite this method of movement, crabs can run quite quickly. For example, an ordinary grass crab reaches speeds of up to 1 m/s. Swimming crabs swing their chest legs (from the second to fourth pair) up to 780 per minute.
There are many varieties of crabs - 6,780 species. The largest one at the moment is the Japanese spider crab. Its size reaches 3 meters (abdomen across). His legs look like spiders - thin and long.
Crabs can be found in the sea and on land, as well as in oceans and freshwater bodies.
Food varies for different types, mainly algae, small crustaceans and fish, bivalves, larvae, worms. Crabs are scavengers, so they do not disdain the remains of animals. The crabs take the food with their claws and bring it to their mouth.
Reproduction occurs by laying eggs. The mating period occurs after the winter migration and molting of crabs. Females are considered sexually mature when they reach 8 years of age, and males when they reach 10 years of age.
The mating process occurs on seabed, where males arrive first, females a little later. The female crab lays her eggs on her abdominal legs. She can lay up to 40,000 eggs at one time. The male fertilizes the eggs and the female moves to shallow water. Gestation of eggs lasts almost a year.
After the eggs mature, the larvae hatch. Baby crabs go through many stages of development before becoming full-fledged crabs.
During the period of growth, the cub is forced to periodically shed its shell. At this moment he is especially vulnerable to predators, so he needs to hide.
Crabs are in danger from almost everywhere. These are squid, cuttlefish and other animals that hunt them. How can they defend themselves?
Despite your small size And defenseless look, crabs have learned to defend their lives.
For example, a crab that lives in Indian and Pacific Oceans– Daldorfia horrida, is a master of camouflage. His body is like seabed, has all sorts of growths and thorns. Plus, it's poisonous.
But the twilight hairy crab is helped to remain unnoticed by its hairy cover. Long hairs growing on the body of this crustacean trap large particles - grains of sand, silt, grass. You won’t immediately understand what it is – an animal, part of the bottom or coral.
The color of crabs can be bright or not very bright. There are species that have nothing special - brown shades, standard form, but there are non-standard copies. These include the Madagascar freshwater crab. It has a distinct body shape, multi-colored and bright colors - its body and pair of claws are bright yellow. The remaining four pairs long legs– pink.
The pebble clown crab has a striking bright color, its body is painted with a variety of patterns. He is beautiful, but behind his beauty lies danger - this small crab, the size of a five-ruble coin, is very poisonous.
Non-poisonous crabs are harvested by people for food. Crab fishing accounts for 20% of the total seafood turnover. Crabs are harvested by hand, either with nets or crab pots. Crab meat is used in cooking. It is rich in protein and vitamins.
You will need
- - aquaterrarium;
- - lamp;
- - coarse sand;
- - stones;
- - granulated food for aquarium fish;
- - vegetables, fruits, fish, seafood;
- - table or sea salt;
- - calcium chloride;
- - ceramic shards.
Instructions
Before you buy a crab at a pet store, you need to choose the most suitable home for it. An ordinary aquarium, i.e. a body of water without land will not work. To keep crabs in a special aquaterrarium, in which sufficient quantity water will be combined with stone islands and varied vegetation. The size of the aquaterrarium, as well as the ratio of water and land in it, depend solely on the type of crab you choose.
The fact is that most The crab spends its life on the shore, and not in the water. To create for a pet optimal conditions existence, arrange its home in such a way that the crab can move from a small artificial reservoir to the shore without any problems. Place a lamp over the stone islands. Crabs love light; you can often observe how your pets willingly visit an artificially created “solarium”.
Use coarse sand as a substrate. Keep it constantly moisturized using a drip or ebb-flow system. The thickness of the sand layer should be about 5 cm. The same value should be followed when organizing a reservoir for crab. The water in it should be hard and slightly salted. To prepare it, dissolve 1 tsp. sea or table salt and 1 tsp. calcium chloride in 10 liters of water.
It is advisable to install a filter in the crab pond. These creatures feel good in clean cold water. 25% of its total quantity will have to be changed weekly. It is necessary to wash the soil and clean it of feces and food debris once every two months.
Also take care to build shelters for the crabs. These creatures stubbornly defend their right to privacy, so they just need a secluded place where they can hide from prying eyes. The role of shelters can be played by ceramic shards of various sizes and gaps between large stones.
In terms of nutrition, domestic crabs are unpretentious. The basis of the diet can be high-quality granulated food for aquarium fish. Crabs will not refuse gammarus, tubifex and dry daphnia. Diversify your pets' diet with finely chopped vegetables, fruits, fish and seafood. Carefully place small pieces of these delicacies in front of the crabs resting on the stone islands.
If you do not want to periodically watch “gladiator fights” and brutal battles, get one crab. These creatures are inveterate individualists, so they feel much more comfortable alone than in the company of their own kind. Despite their attractive and harmless appearance at first glance, crabs are quite aggressive. In nature, fights often occur between males for territory, shelter, females and food. Often such fights end in death.
Crabs are representatives of crustaceans. They can live in both sea and fresh water. These animals feed on invertebrates. Crabs reproduce by laying eggs in secluded places, which go through a series of intermediate transformations before becoming an adult.
Appearance of crabs
The crab has a small head that merges with the chest. The crab's body is protected from above chitinous shell, which is exoskeleton. These animals change their shell during growth several times during their lives. During the molting period, the old shell comes off, and the new one is not yet saturated with sufficiently lime, remains weak, which makes the animal very vulnerable. That’s why, in order to somehow protect yourself during this dangerous period, crabs camouflage themselves with the color and texture of their surroundings. For the same purpose, in the first days after molting, they hide and do not hunt.
Crabs have claws on their front pair of legs, which help them hunt and escape from their pursuers. When in danger, crabs can shed their claws. An interesting fact is that crabs have blue blood.
Benefits of crabs
They eat crab meat, which is a delicious seafood with amazing delicate taste. The meat of crabs is found in the claws, legs and back. Since each individual contains little meat, harvesting crab in industrial quantities is labor-intensive, which determines its high cost.
Crab meat is a rich source complete protein, With low content fat It contains no carbohydrates. It's becoming important factor when including dietary crab meat in the diet of obese people and patients with obesity. Crab protein is easily digested and absorbed by the body, because there is practically no connective tissue in crab meat. Thanks to this, despite the relatively low calorie content of crabs, a feeling of fullness is achieved quite quickly.
The amino acid taurine occupies a significant proportion in the protein structure, which supports muscle health and blood vessels, retina.
The benefits of crab can also be judged by the presence of omega-6 and omega-3 fatty acids, reducing the content of “bad” cholesterol in human blood, which in turn significantly reduces the risk cardiovascular diseases and atherosclerosis.
Crabs living in the sea accumulate a lot of iodine, the most important trace element for humans. Iodine is part of the structure of thyroid hormones, and they are involved in the regulation of all types of metabolism and are responsible for the development nervous system and human growth. Only 20 - 40 g of crab meat contain daily norm Yoda.
Crab is rich in vitamins, especially PP and group B, as well as microelements. Zinc and selenium from seafood are involved in the formation of testosterone, a sex hormone in men. Therefore, for them, the benefit of crab also lies in maintaining libido. Its meat also contains copper, calcium, phosphorus, sulfur, sodium, magnesium, etc.
Crabs are useful for people suffering from digestive disorders, obesity, cardiovascular diseases and thyroid pathology, visual impairment, anemia, depression or nervous tension.
The calorie content of crabs is approximately 85 kcal per 100 g of product.
Cooking crabs
Since the crab has very delicious meat, then even simple recipes preparations result in amazingly tender, delicious dishes. So, to boil crab, you need to add salt to the water at the rate of 50 g per 1 liter of water, and cook for about 15 minutes from the moment it boils. When the crab is ready, the small claws are easily separated from the meat. It is better to cool it before using. Before serving, crab meat is sprinkled with lemon juice and decorated with sprigs of greenery.
This seafood is included in the recipes of many gourmet salads and exotic dishes. Since crab meat spoils quickly, it is stored for a very short time - no longer than 15 hours (or 30 hours on ice).
Video from YouTube on the topic of the article:
People have been breeding fish for a long time, and this activity is no longer perceived as some kind of exotic. But time, like fashion, does not stand still, and today more and more often you come across aquarium crabs. They differ favorably from other crustaceans in their variegation of color and exciting behavior. That is why we decided to talk about aquarium crabs and the nuances of keeping them with.
Aquarium crab
- very popular pets kept in. Many of them are rather uncooperative arthropods that cannot tolerate any neighbors, including their own relatives. They live mainly in salt water, although there are freshwater species, which take root well at home.
The most popular crabs that take root well at home:
- Rainbow. Can grow up to 15 cm in diameter.
- Leopard print. Completely freshwater crustacean. Very aggressive, can only be kept in pairs (male-female).
- Mango. Small, 4-5 cm in diameter, unpretentious pet.
- Freshwater Dutch. Small (2-3 cm), gray, omnivorous, peace-loving crab.
Conditions for a sea dweller
Many inexperienced aquarists prefer to keep crabs in a tank with fish or other water inhabitants. But they soon come to the conclusion that it is better to purchase a separate tank (or rather, an aquaterrarium) for these crustaceans, because the conditions for keeping them are somewhat different.
Water requirements
Most aquarium crabs salted water is required.
The water level should not be deeper than 15 cm. Perfect option– 10-15 cm.
It would be useful to recall that the purity of water should be at high level. In addition, the water must be running. This can be done using filtration and additional aeration.
Important! If the content of nitric acid and ammonia salts in the water is high, the crabs may wither away. Therefore, these parameters need to be monitored systematically by analyzing the composition of the water.
To reduce the level of nitrates and ammonia, it is recommended to add salt to the water (2-5 g per 1 liter of water). This procedure is performed during the molting period of crustaceans.
It's better to add salt to the water sea salt, but if you don’t have one, you can mix baking soda, calcium chloride and regular table salt.
The water should not be softer than 10 °, especially during the molting period, and with an acidity of 7.2-7.5. Water hardness directly affects the adaptation period.
Behind temperature conditions You also need to make sure that the water should be around +25-26°C. Moreover, failure to comply with these parameters may result in the death of the pet.
Soil and plants
Many people wonder: is soil needed in an aquarium? Experts say that soil is simply necessary for the crab. And if you remember what crabs eat, then this question will simply disappear. After all, it is in the soil that nitrifying bacteria, vital for stabilizing the biological balance, can multiply.
The ideal soil for crabs is zeolite mixed with coral chips. But you can use a composition with tuff granules and granite gravel.
The granules cannot be small. Acceptable size is 3-5 mm. The fact is that the soil needs to be periodically siphoned, and during this process small and too light particles will be carried away by the flow, therefore, cleaning will be difficult.
About 10-14 days before moving the crabs into the tank, you need to introduce nitrifying bacteria (Nitrosomonas, Nitrobacter) and introduce several small fish that can easily tolerate alkaline salt water.
Did you know?There is one unusual representative crabs like the Yeti Crab. Its paws and claws are covered with "fur." Researchers have not yet revealed what such a fur coat is for.
Experts say that you can cope without soil, but you need to take care of a powerful external canister filter to ensure microbiological purification of the water.
You should also not forget what a crab eats in nature and try to recreate an analogue at home. To do this, it is advisable to plant aquatic species in the aquarium. In this case, it is better to use algae that float on top or in a layer of water:
- Elodea;
- Wolfia rootless;
- pemphigus;
- Vallisneria;
- Riccia floating;
- water fern;
- duckweed;
- Indian nayas;
- hygrophila;
- water hyacinth;
- Java moss.
Important! It is undesirable to use algae whose roots will be located in the ground - crabs dig them up and throw them away.
Requirements for an aquarium
To begin with, crabs in an aquarium need dry land. Without a shore, these crustaceans will simply die, because they spend about 90% of their time on land. At the same time, some processes (shell shedding) cannot take place without water.
The land should not be flat - there should be a slight rise along which the crab can easily climb to the top. Steps can be made of sand or stones. There must be special conditions in the water itself, because crabs are residents of mostly salty water bodies.
The aquarium should be quite spacious, because some crabs grow up to 15-17 cm. Therefore, the optimal dimensions of their home are 50x40 cm, and if you plan to keep several pets, then the length of the aquarium should be at least a meter.
Home equipment
In order to provide a comfortable home, you need to take into account what the crab looks like and how it behaves in natural conditions. Better environment- not water, but a damp substrate and a bathing suit in which he can molt and wet his gills.
In this case, you do not need to buy any filters or siphons - the water is simply replaced with fresh water as it gets dirty. A regular plastic food container can serve as a bathing suit, but not another large aquarium with an entrance or a ready-made bathing suit for reptiles. The main requirement is that the crab must be completely immersed in the container.
The absence of different filters and heating pads allows you to avoid the danger of wires. Cases were often observed when crustaceans died due to a short circuit - the crabs simply bit the wires with their claws.
Since crabs lead a burrowing lifestyle, they often dig holes with embankments in the ground and destroy the shore. To prevent this from happening, you need to lay a pipe on land at an angle, the cross-section of which will be slightly larger than the diameter of the shell. At the same time, you need to ensure that water does not stagnate in this pipe and that there is always air there (ventilate).
Did you know?The largest known crab is giant spider crab. Adult representatives of this species reach a weight of 20 kg, and the claws, when open, are almost 4 meters long.
What do crabs eat: nutrition
Many people are interested in what crabs eat at home. As experts say, they can eat any fish food (dry and dried gammarus, daphnia, bloodworms, mealworms), as well as:
- shellfish (mussels, squid);
- crickets;
- crustaceans;
- lean meat (beef, chicken liver);
- white fish meat.
These crustaceans do not disdain carrion, and they look for food both in the water and on the shore.
Important! It is useful to give the crabs a kind of omelette made from paprika, dried nettles and crushed calcium salt (calcium glycerophosphate).
To prevent your pets from destroying algae, you can include plant foods in their diet:
- oranges;
- apples;
- pumpkin;
- dandelion foliage;
- nettle;
- green pea;
- Bell pepper;
- bananas;
- boiled carrots;
- spinach;
- Brussels sprouts;
- salad;
- pears.
It is advisable to pour boiling water over all greens and vegetables or lightly boil them and cut into small pieces.
The food should be placed in a dry place suitable for the crab. It should be remembered that food should not be placed in water, since food, when decomposing, strongly poisons it and can lead to an outbreak of serious diseases that will simply kill the pet.
There is no need to feed crabs - 1/3 of their body weight is enough, but not more than half of its weight.
Did you know?In fact, crab claws are not powerful enough to fight the enemy. Fights are won only because of their terrifying appearance.
Is it possible to breed crabs in captivity?
If you regularly monitor how crabs are kept and feed them well, they will feel great at home.
In nature, these crustaceans reproduce throughout the summer, when it is warm. comfortable weather. Crabs reproduce by laying eggs.
Unfortunately, we cannot do without the ocean, since the offspring must necessarily go through the plankton stage.
In captivity, crabs reproduce quite difficult (by the way, there is very little evidence of this), although mating behavior present.
Fish compatibility
It’s better to buy one crab and not worry that it will be boring. The fact is that the males of these crustaceans are quite territorial. The appearance of another representative of this species can end sadly - they will certainly fight, defending food, females, territories, etc. In these fights, opponents will receive injuries (lose claws and other limbs), which are then restored during the next molt.
It is also worth noting that crabs do not get along well with other neighbors. For example, if leisurely fish swim in the aquarium, they will often be pinched. Get along well with crabs (according to at least, these crustaceans will not eat them) such fish:
- ;
For those who saw Kamchatka crabs for the first time in their lives, these animals make a great impression.
In terms of its size, the Kamchatka crab is an outstanding representative not only of decapods, but also of all crustaceans. Character traits structures of crustaceans reproduced in Kamchatka crab on a large scale, they are striking even with the most superficial glance at this animal.
The width of the shell of the average male Kamchatka crab is about 16 centimeters, the span of its legs is almost 1 meter, and its weight exceeds 2 kilograms. The largest specimens reach 25 centimeters in carapace width, one and a half meters in leg span and 7 kilograms in weight.
The body of the Kamchatka crab consists of a cephalothorax, covered with a common shell, and a belly, folded under the cephalothorax. Therefore, if you look at a crab from above, only its shell and legs are visible. A powerful shell with large sharp spikes reliably protects the animal and, in addition, serves as a support for the muscles. The shell, like that of the crayfish, fuses with the body only on the back, and on the sides it lags behind the walls of the body and hangs down like the sides of a jacket, covering the gills. The gills in the resulting cavities are protected from damage and at the same time are easily washed with water. In front of the cephalothorax are attached two pairs of antennae, eyes on stalks, jaws and legs. Front edge The shell is armed with a sharp outgrowth that protects the eyes.
The abdomen of the crab, always tucked under the cephalothorax, in females bears special appendages for bearing eggs. The abdomen contains the intestine and internal genital organs. The first pair of crab legs is armed with powerful claws, the next three pairs are used for movement, and the last pair of reduced legs is always under the shell and is used for cleaning the gills. The muscles of the walking legs are very well developed.
What do Kamchatka crabs eat?
Kamchatka crabs are predators. They eat marine bottom polychaetes, mollusks, amphipods, echinoderms, small sea acorns and other bottom animals. The crabs tear their prey with their claws and, using their legs and jaws, crush, grind and send it into their mouths. The right - large - claw is used to crush shells of mollusks and skeletons sea urchins. With its left claw, the crab can tear only soft prey. Very interesting experiments were carried out to find out what sense guides crabs in search of prey. Food was lowered into a large aquarium where Kamchatka crabs were kept. The animal immediately reacted to the smell with characteristic movements of the antennae and began searching for prey. The crab cannot determine the direction to the prey by smell, so it begins to move slowly, feeling the bottom with the ends of its claws. The crab lowers its claws vertically downwards and, touching the ground with the ends of its claws, quickly opens and closes them, as if snapping scissors, to see if anything gets caught. These probing movements are very energetic and "nervous".
The crab searches blindly, describing the most incredible loops along the bottom of the pool. As it approaches the feeder, when the smell of food intensifies, the crab becomes very excited and probes the bottom with its claws even more often. However, even in close proximity to the food (for example, at a distance of 1 centimeter from the end of the claws to the food), the crab repeatedly misses and moves away from it again. This suggests that the crab's sense of smell and vision are poor helpers, and it finds its prey only through touch.
Finally, the crab probes for food with the tip of its claw and quickly grabs it with one claw or both at once. In search of prey, the animals lost an unusually large amount of time, traveling an unnecessary long distance.
All my long life Kamchatka crabs wander, repeating the same route every year. The Kamchatka crab is an exclusively running animal and is completely unsuited to either swimming or burrowing into the ground. The crab cannot burrow, because then its open gills can become clogged with silt. Powerfully developed leg muscles allow you to cover long distances. The crab runs both forward and sideways, alternately throwing out and bending its walking legs. The claws of the feet act like pegs stuck into the ground. The body is supported by weight when walking. The speed of movement of Kamchatka crabs in a straight line reaches 2 kilometers per hour. However, the crab usually moves in zigzags, and the distance it travels per day does not exceed 10-13 kilometers. Individual crabs wander in different directions, and the speed of movement of the entire school is only 2-4 kilometers per day. Crab schools all year round walk within their migratory area. The size of such areas for one school is almost 200 kilometers. Some crabs stray from their schools and move into schools in neighboring areas. The reason for such transitions is strong competition for food. Animals often move to areas where fishing is more active. There, the number of crabs drops significantly due to fishing, and competition for food decreases.
Where do Kamchatka crabs winter?
The wintering grounds of crabs are located quite far from the coast at depths of 110 to 200 meters. In fact, the crab does not hibernate, but continues to behave in the same way in winter. active image life, just like in the summer. The departure to depth is explained more low temperatures water in shallow waters and ice formation. In the spring, when the bays of the sea are cleared of ice, the crabs move to shallower areas. During this period, males and females of the king crab stay in separate herds and move to the shore in parallel paths. Female crabs carry eggs on their abdominal legs, which have been developing since last year, and halfway through the adult crabs' journey to the shore, a mass hatching of larvae occurs. The fully developed crab embryos in the eggs, whose translucent eyes gave them the name “caviar with eyes,” tear the shells of the eggs into two halves and float up into the water column.
Reproduction of Kamchatka crabs
About a month after the start of migration, schools of males and females meet in shallow waters and mix. The mating period begins. Females at this time look very unpresentable: overgrown with shells barnacles dirty shell, empty shells of eggs on the abdominal legs. Nevertheless, the males choose their mates and clamp the claws of the females with their claws. Couples can remain in this “handshake” position for 3 to 7 days. Then the males help the females molt by pulling off the contaminated old shell from them, and attach spermatophores to the bases of the third pair of walking legs of the female. After this, the partners separate. After some time, the female lays eggs on her abdominal legs, which are fertilized from the spermatophore and which the female carries on herself until next spring.
After mating, the schools of females and males again migrate separately, now the crabs go in search of food and feed all summer. Before the summer migration, males molt, but in complete solitude, hidden among pitfalls. During the feeding period, crab schools gradually move from one field to another with average speed about 4 kilometers per day, destroying a significant number of bottom animals.
Where do Kamchatka crabs live?
The largest quantity of Kamchatka crab, as its name suggests, is found off the coast of Kamchatka, as well as in Primorye. Its distribution area goes from Posyet Bay through the northern part Sea of Japan, across the Sea of Okhotsk and most of Bering Sea along the Aleutian Islands to the Pacific coast of Canada.