Where does the sand crab usually live? Sand crabs, photo
Crabs are arthropods from the order of decapod crustaceans, also known as short-tailed crayfish. The modern classification includes more than 6,780 species of crabs, many live only in the seas, others tolerate salt and fresh water equally well. Several dozen species of crabs inhabit the territorial waters of Russia.
Since ancient times, crabs have been an important commercial item; their meat is tasty and considered a delicacy. Thanks to their omnivorous nature, crabs eat everything they can find, watch and catch. Massive claws are the crab's main weapon and means of obtaining food. What do crabs that live in Russian waters eat?
Sand crab (Xantho poressa)
This is a small crab, with a shell width of up to 4.2 cm. It is colored grayish-green with dark speckles, sometimes with a blue or purple tint. It feeds on small benthic invertebrates and decomposed organic matter.
It is found off the coast of Crimea and the Caucasus, and is found in the Mediterranean Sea and off the coast of the Canary Islands. The sand crab is extremely slow, rarely goes to a depth of more than 15 m, and prefers shallow water with a pebble or sandy bottom.
Sand crab (Xantho poressa).
Chinese mitten crab (Eriocheir sinensis)
An extremely unpretentious species, it originally lived exclusively in the Yellow Sea, but at the beginning of the 20th century, with ballast waters, it accidentally ended up in Europe and today it is found even on the Volga and Lake Onega. It feeds on everything it finds at the bottom: shellfish, fish remains and algae.
Blue crab (Callinectes sapidus)
At the beginning of the 20th century, blue crabs - natives of the Atlantic coast - appeared in the waters of Europe and today they are found in the North, Baltic, Mediterranean and Adriatic seas. The carapace, up to 20 cm wide, is brown, gray, greenish or bluish with wide (up to 8 cm) orange spines on the sides.
It is found at depths of up to 36 m and competes quite aggressively for food with other crayfish. It eats everything that crabs eat: shellfish, small fish, worms, sea urchins, aquatic vegetation and carrion. But unlike many relatives, when there is a lack of food, he practices cannibalism.
Blue crab (Callinectes sapidus).
Common snow crab (Chionoecetes opilio)
An inhabitant of the cold waters of the Bering, Okhotsk and Barents seas, it is found at depths of up to 100 m. The shell of males reaches a width of 16 cm, the color is usually reddish, and turns green before molting.
It eats starfish, sponges and bryozoans, shrimp, amphipods, dead fish and other crustaceans. The plant part of the diet consists of various algae.
Common snow crab (Chionoecetes opilio), large and small.
Marble crab (Pachygrapsus marmoratus)
A rare species of crabs listed in the Red Book. Lives in the Black and Mediterranean seas, most often found in the coastal waters of Sochi and Abkhazia. A medium-sized crab, with a carapace width of up to 10 cm, a characteristic “marble” color and long legs covered with spiny hairs.
It obtains food consisting of invertebrates and organic remains on the rocky bottom, occasionally comes ashore and can do without water for some time.
Marble crab (Pachygrapsus marmoratus).
Marble crab (Pachygrapsus marmoratus).
Grass crab (Carcinus aestuarii)
It is found off the coast of the Black and Azov Seas, as well as in many reservoirs of the Mediterranean Sea basin. A medium-sized crab, with a shell up to 8 cm wide, painted grass-green. It has small claws, so it defends itself poorly and, in case of danger, runs away sideways at a speed of up to 1 m/sec.
It obtains food from ambush, hunting mussels, shrimp, small gastropods and fish fry. Willingly eats carrion and algae in coastal lagoons and bays.
Grass crab (Carcinus aestuarii), female with eggs.
Grass crab (Carcinus aestuarii).
Four-cornered hairy crab (Erimacrus isenbeckii)
Lives in cold waters from the coast of the Kamchatka Peninsula to the Eastern Passage. This is a medium-sized crab with an almost equilateral shell, up to 12 cm in diameter. The limbs and shell are densely strewn with short, stiff hairs.
The animal's diet is similar to that of many crab species and includes gastropods and small crustaceans.
Four-cornered hairy crab (Erimacrus isenbeckii).
Crabs are of great benefit and are considered the orderlies of rivers and seas, cleaning coastal waters from decomposing organic residues.
And twenty varieties of them live in the Black Sea. They have quite decent sizes, unusual shape and habits. Most of them live in the shallow waters of the coastal zone, hiding in algae. Let's look at what types of crabs live in the Black Sea.
Stone crab
Stone crab is the largest Black Sea crab. He prefers to live in deeper places. Of course, it can also be found near the shore, but only in deserted and deserted places. The Black Sea crab, whose size reaches nine to ten centimeters, does not feed on carrion like other species; it is strong and aggressive in itself, so it can become an agile and fast predator at any time. In ambush, a crab can guard small fish, worms, and snails. His claws are very strong, he snaps them as well as hermit crabs, like seeds.
The Black Sea crab has a special type of muscle. At the molecular level, they are quite different from the muscles of humans and animals. An interesting fact is that the color of a crab’s shell always matches the color of the stones in which it lives. As a rule, this is a reddish-brown hue, but stone crabs that live among yellow sandstones are themselves very light. They protect their shelter in the stones, as well as the surrounding territory, from other inhabitants. Females carry eggs under their abdomen. At one time they lay 130,000 eggs.
The habitat of this species is very large. Stone crabs not only live in the Black Sea, but also in the Mediterranean and on the Atlantic coast. Until the eighties of the twentieth century, its numbers were quite impressive. This species was even considered as an industrial species. Now its numbers have decreased significantly, it has become an endangered species.
But nevertheless, people engage in amateur fishing. During the day, stone crabs are found in the depths, and at night they come to the shallows. It is there that they are caught, blinded by the light of flashlights. The number of stone crab has decreased significantly due to deteriorating living conditions and uncontrolled fishing, because it has good taste.
Hairy crab
The Black Sea hairy crab is very similar to the stone crab, only its size is half the size. And the carapace is dark purple in color and covered on top with a thick layer of yellow bristles-hairs. The Black Sea crab prefers to live near the shore under rocks. Its diet is not very different from that of other crabs. It poses a danger to fish because it splits their strong shells like a nut.
marble crab
The shell of the marbled crab can be colored from dark brown to blue-green, and is dotted with a large number of light stripes that resemble marble. Because of its dark color and long limbs, it is sometimes called the spider crab. This is the only Black Sea crab that runs out of the water and travels along coastal rocks and stones.
At night they can climb rocks to a height of five meters, and along gentle slopes they can go five to ten meters from the water. But only when they sense danger, they take off with lightning speed and hide in the nearest crevice or throw themselves into the water.
What do Black Sea crabs eat? In addition to algae, they eat the remains of their fellows and various other organic matter. They will not disdain even scraps from the human table. Marble crabs are also rare and therefore considered an endangered species.
Herbal or Mediterranean crab
The Black Sea grass crab also lives in shallow water, but prefers abundant grassy thickets, but it can also live among stones. Its green shell reaches eight centimeters. When encountering a predator, it does not rely much on its claws, but immediately runs away. But he runs very quickly, albeit sideways. Its speed reaches up to one meter per second.
Lilac crab, or water lover
Black Sea crabs are very interesting. Among them there is another remarkable water-loving crab. It is quite slow and can be found not only in shallow water, but also at depths of up to fifteen meters. The lilac crab loves solitude very much. It can bury itself in the sand and remain there for weeks without air or food.
Swimming crab
The swimming crab is another one that likes to burrow into the ground. It is small in size, but its hind legs are slightly flattened, like shoulder blades. With their help, he throws sand on himself. In addition, crabs successfully use these unique flippers when swimming.
It should be noted that this is the only species that can swim. All other Black Sea crabs cannot do this.
Blue crab
The blue crab is the rarest species of sandy soil. It appeared in the waters of the Black Sea in the sixties of the twentieth century. And he arrived from the Mediterranean. It was brought in with ballast water by ships on the US East Coast. However, the Black Sea turned out to be too cold for them. Young crabs cannot survive at such temperatures, which is why they are extremely rare.
Invisible crab
The invisible crab is an amazing specimen. Its uniqueness is that it is almost impossible to detect among algae. The thin and long-legged creature is a true master of camouflage.
It plants tiny bushes of algae on its shell and in this form wanders around unnoticed.
crab pea
There is also a very small pea crab. As a rule, it lives among mussels, and sometimes even settles inside a shell with a live mollusk. Such crabs can also be found in shallow water in rocks, but it is extremely difficult to see them, since an adult specimen fits on a ten-kopeck coin.
Instead of an afterword
The Black Sea has become home to twenty species of crabs in those places where the shore is rocky and dense thickets of algae begin right at the water's edge. Such places are home to many inhabitants of the underwater world, including crabs. They also took a liking to sandbanks.
And the smallest representatives can be detected only if you take a bunch of algae and rinse them in a basin, only then will the pea crab show itself - the smallest representative of the family and the greatest master of camouflage.
Crabs are a large group of aquatic and semi-aquatic animals belonging to the order Decapod Crustaceans. Crabs differ from related crayfish, shrimp, lobsters and lobsters by a noticeably shortened abdomen, tucked under a wide cephalothorax. This gives them a specific, well-recognized shape. At the same time, crabs have reached unprecedented diversity: 6,793 species of these animals are united in 93 families, which is half the number of the entire order.
The spotted-footed rock crab (Grapsus grapsus) is a native of the Galapagos Islands.
Along with a special body shape, crabs are characterized by the presence of 10 pairs of limbs. They are divided into thoracic and abdominal. The first 3 pairs of thoracic limbs are very short, they are called maxillae, because they do not participate in movement, but only serve to bring food to the mouth. The remaining pairs of thoracic legs are used for locomotion, grasping and cutting food, and can also perform other auxiliary functions. The pair of the largest and most massive legs are claws. With their help, crabs can not only hunt, but also defend themselves and participate in mating fights. The narrow specialization of these organs is reflected in their appearance: often the right and left claws have different sizes and shapes, giving the crab’s body a noticeable asymmetry. As for the abdominal legs, they are small and are used for fertilization (in males) or bearing eggs (in females). Vital organs such as gills are connected to the chest legs of crabs. Often their petals are located directly on the leg segments or near the place of their attachment to the body.
Due to the huge difference in the size of the claws, lure crabs appear to be one-armed. Like people, these animals are right-handed and left-handed, with 85% being right-handed.
Crabs are one of the most advanced crustaceans, so they have developed sensory organs. Vision plays a big role in their lives. The eyes of these animals are complex, faceted. They are made up of thousands of eyes, each of which sees only a tiny part of the space directly in front of them. The final assembly of the image occurs in the animal’s brain. Numerous observations have proven that with the help of vision, crabs identify a potential enemy, find a partner during the breeding season, and navigate in search of food. But if an animal is blinded, it will only lose the ability to see danger, but will find food and a partner with almost the same efficiency. Antennas (“antennae”), capable of capturing odors, will help him with this. If the crab's antennae are also cut off, then it... will find food again. True, in this case he will have to spend a lot of time and effort, because he will literally move towards the prey by touch, tapping his claws on the ground. Some types of crabs have balance organs - statoliths. By the way, the eyestalks play a huge role in their physiology. These are real endocrine glands, capable of secreting hormones and regulating such body functions as the frequency of molting, the onset of puberty, and even color changes!
The Latreille's land bigeye (Macrophthalmus latreillei) has especially long eye stalks, which is associated with the need to inspect the area at a great distance.
Crabs do not have skin as such; it is replaced by a layer of hard and impenetrable chitin, which forms a kind of shell. Chitin is unable to stretch, making normal linear growth impossible. Crabs solve this problem by molting regularly. When the old shell bursts, a soft and defenseless animal emerges. It takes from several weeks to six months for the new cover to harden; during this period, the crab hides in a secluded place and grows intensively. Chitin can be impregnated with all kinds of pigments, so crabs can have almost any color.
The bicolor vampire crab (Geosesarma bicolor) gets its name from its unusual combination of bright yellow eyes with a dark purple shell. Due to its impressive appearance, it is often kept by amateur aquarists.
In addition, the chitinous cover may have outgrowths: sparse and hard, like spines, short and hard, like bristles, or long and thin, like wool.
The Chinese mitten crab (Eriocheir sinensis) stands out among its relatives with a “fur” muff on its claws.
The sizes of these animals also vary widely. The diameter of the shell of the world's smallest pea crab does not exceed 1 cm, while the leg span of the largest Japanese spider crab reaches 4 m and weighs 20 kg.
Pea crab (Pinnotheres boninensis) lives on the coast of the Azov and Black Seas.
Crabs inhabit all the seas and oceans of the planet, but they reach their greatest diversity in the tropics. The habitat of these crustaceans has a very wide range: crabs can be found in the shallow waters of seas and oceans, among thickets of corals on reefs, at depths of up to 5000 m, in cave ponds, in the intertidal zone, mangroves and even in the depths of islands far from the coast. The vast majority of them live in salt water, about 850 species live in fresh water. Crabs that spend long periods of time on land store water under their shells or develop organs like lungs. Their underdeveloped gills almost do not work, and when constantly immersed in water, such individuals die. Bottom-dwelling species are often active in the dark; land crabs are most active during the day.
The second largest Tasmanian giant crab on the planet (Pseudocarcinus gigas), with a carapace width of 46 cm, weighs up to 13 kg.
When moving, these crustaceans never place both legs of one pair on the ground at the same time, which gives their gait stability, but the short body length and large number of legs make forward movement inconvenient, so crabs prefer to walk sideways. At the same time, this does not in the least prevent them from developing decent speed, for example, a grass crab covers 1 m in 1 second! But these animals swim poorly and reluctantly.
The exception is swimming crabs, whose back pair of legs are transformed into paddle-blades, thanks to which they feel at home in the water element.
These crustaceans have a quarrelsome character; they all live alone and jealously guard their areas or shelters; Males are especially aggressive. At the same time, areas of small crabs are very small, so there can be up to 50 burrows per 1 sq.m. Danger is the only thing that makes the inhabitants of the colony forget about strife. When threatened, crabs signal their neighbors by waving their claws, making sounds, or tapping on the ground. Thanks to vibrations, even those individuals that do not see the enemy manage to hide.
Blue soldier crabs (Dotilla myctiroides) form large aggregations on beaches.
Shelters deserve special attention. In the simplest case, these animals hide among coral branches, in crevices between stones or shell valves, and in the cavities of sponges. But many crabs do not expect favors from nature, but instead dig holes in viscous silt or sand. These houses may have one straight passage (often quite deep), or several branched passages with emergency exits; beckoning crabs equip the entrance to the hole with a lid. Some species live under the canopy of jellyfish, among the tentacles of sea anemones, in the mantle cavity of mollusks, among the needles, or even in the rectum of sea urchins.
These holes on one of the beaches of Malaysia were dug by the closest relatives of soldier crabs - scopimera. Each individual, pushing sand out of its home, rolls it into a neat ball. The crab droppings have the same shape when they eat the soil.
Crabs have practically no food specialization; they are all omnivores to one degree or another. These animals can eat bacterial films covering rocks, algae, fallen leaves and flowers, bivalves, polychaete worms, starfish, small crustaceans and even octopuses. Like crayfish, crabs readily feast on carrion. Species living in shallow water happily “snack” the soil on regular food. By passing sludge through their intestines, they assimilate the microorganisms contained in it. Crabs not only grab large prey, but cut it up like real gourmets. At the same time, they use their claws like a knife and fork: they hold the prey with one, and cut off neat pieces with the other.
A grass crab (Carcinus maenas) is about to dine on a bivalve.
Reproduction in crabs is clearly seasonal; in different species it is timed to coincide with certain natural phenomena (rainy season, highest tides). For example, Christmas Island red crabs (Gecarcoidea natalis) live on land away from the shore, but move to the surf line to lay eggs. Their migration is one of the most ambitious phenomena in nature.
Millions of individuals rush towards their goal like a living river, overcoming roads, ditches and other obstacles along the way.
At this time, crabs die en masse under the wheels of vehicles and under the feet of people who are tired of avoiding countless travelers.
To prevent the crabs from dying, Christmas Island is creating barriers along roads to divert migrants away from dangerous routes.
Pay attention to the insects in the frame. These are yellow crazy ants brought to the island by people. They turned out to be a very aggressive and prolific species and have already destroyed 1/3 of the crab population - 20 million individuals!
No less interesting are the mating battles of beckoning crabs. With their hypertrophied signal claw, they threaten their opponents and even fencing with it in a collision. Then they signal the female with waving movements, as if declaring their victory. This emphasized ritualism has led to the fact that in many species there is a very noticeable difference between males and females (sexual dimorphism).
Duel of beckoning crabs.
Before mating, the couple sometimes takes a “face to face” position and can remain in this position for several days. Interestingly, one mating is enough for a female to lay fertilized eggs throughout her life. This is explained by the fact that the male presents her with sperm packed in special bags - spermatophores. In them, the germ cells remain viable for many years; during the next season, the female dissolves the spermatophore membrane with special secretions and fertilization occurs again. The fertility of crabs is very high and amounts to tens of thousands and millions of eggs. The female carries them on her abdominal legs from a couple of weeks to several months. The hatched larvae begin to swim freely.
Swimming crab larva.
After several molts, they turn into young crabs, which settle in the biotopes characteristic of a particular species. The lifespan of these crustaceans ranges from 3-7 years for small species to 50-70 years for the huge spider crab.
Japanese spider crab (Macrocheira kaempferi).
Due to their great diversity and abundance, crabs have many enemies. Their lives are attacked by fish, octopuses, crocodiles, starfish, seagulls and virtually all predatory animals that wander along the coast. Crayfish raccoons generally specialize in collecting crabs on the shore. Such intense interest on the part of carnivores has forced these crustaceans to develop many methods of defense. The simplest of them is camouflage. This is achieved in some cases by coloring, which very accurately reproduces the color and even the pattern of the substrate on which the species is found.
The caramel crab (Hoplophrys oatesii) imitates the dendronephthia coral on which it lives in color and shape.
In other cases, surrounding objects are used for cover. For example, shy crabs cover themselves with a shell-shield, decorator crabs cut out pieces of bryozoans and hydroids with their claws and place them on their backs, gluing them together with special secretions. On the crab's back, these colonial animals continue to develop and transform its shell into a flower bed.
It is difficult to recognize the perfectly camouflaged decorator crab (Camposcia retusa) in this crawling bush.
The Dromia crab looks for a sponge and, like a real seamstress, cuts a piece out of it exactly to the size of its back.
The Dromia erythropus crab resembles an old woman in a beret. Since its body is quite fleshy, the dromia has to look for a flap with a curve that perfectly follows the convexities of its shell.
If disguise does not help, active methods of defense are used. Large crabs take a fighting stance and raise their claws up. If the offender does not understand the hint, they use their wire cutters and are capable of inflicting deep cuts. Boxer crabs always hold sea anemones in their claws, the stinging cells of which are dangerous even for relatively large animals.
A female boxer crab (Lybia tessellata) in a fighting stance with sea anemones. A clutch of eggs is visible on the abdomen of this individual.
Many species are capable of autotomy (self-amputation). When it sees an enemy, the crab throws its leg away by contracting special muscles. In this case, the valves at the tear site immediately close the wound and stop the bleeding. If such a handout was not enough, the victim offers the predator the next limb. Severed legs grow back after several molts.
The land hermit crab is a land crab that can drown if left in water for a long time. It lives in the Caribbean Sea, it is also common in Venezuela, the Bahamas, Belize, India, Florida, and the Virgin Islands. These crabs are also called tree crabs, tropical land hermit crabs, and Caribbean hermit crabs.
Description of the land hermit crab
There are 7 varieties of tropical land hermit crabs. These crabs reach a length of about 3 centimeters, the weight of an adult individual reaches 110 grams.
The body shape is cylindrical, elongated. The body is covered with small hairs. The front part of the body is protected by a hard shell, while the abdominal part is much softer.
Land hermit crabs have 5 pairs of legs. The first pair represents claws. With the help of the right claw, the crab eats, and the left one is used for protection, for example, in times of danger, it can close the entrance to its hole. Most crabs have purple claws, but they also come in lemon, brown or red. The second and third pair of crab legs are for walking. The last two pairs of legs are very small; they sometimes do not protrude from the shell.
Caribbean hermit crabs breathe using gills. There are 2 pairs of retractable antennae: long antennae are used for touch, and short antennae perform the function of smell. Land hermit crabs have good eyesight.
When the crab is outside the shell, its sex can be determined: the male has hairs on the last pair of legs, and there are no appendages on the abdominal cavity.
Lifestyle of land hermit crabs
Tree crabs are social animals that live in large groups. They are nocturnal, their peak activity is observed at 20:00. Land hermit crabs do not like high temperatures and the sun, so during the day they hide in small holes, under stones, logs, leaves, and the like.
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Land hermit crabs live on the sandy shores of the Caribbean islands, at a distance of 1.8-3.5 kilometers from the water. They are found among coastal plants. They avoid swamps and places with dense vegetation. Hermit crabs prefer water with low salinity.
If a tropical land crab stays in water for too long, it will drown. Adults molt every 12-18 months, while juveniles molt several times a year. After molting, the crab chooses a new, larger shell.
At temperatures below 20 degrees, the activity of land hermit crabs decreases, and at temperatures below 18 degrees they hibernate. These crabs can make various sounds: chirping, crackling, croaking.
Tropical land hermit crabs feed at night. They are omnivorous scavengers. Their diet also includes cactus fruits and even fresh droppings of horses and cows. In captivity, their life expectancy can reach 11 years.
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Reproduction of land hermit crabs
The breeding season for tree crabs is August-October. To mate, males and females have to leave their shells. Young females lay 800-1200 eggs, and adult females lay 40-50,000 eggs. The color of newly laid eggs is red-brown; within a month they turn blue or gray.
3 weeks after mating, the female goes to shallow water, her eggs are on her 5th leg, she collects them and places them on wet stones. The eggs are washed away by the waves into the water.
The larvae of land hermit crabs have several stages of development: zoe, then glaucotoe, then young crab. During metamorphosis, the larva settles to the bottom and then crawls out onto land.
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Zoe is thin and long, its size reaches 3 millimeters. She has 2 large eyes. At this stage the larva feeds on plankton. Zoe moults 3-4 times, during which she grows.
After 4-5 molts, the larva enters the glaucotoe stage. At this stage, very small antennae appear, the eyes are located on stalks, and the first paws transform into claws. Glaucothoe resembles an adult crab in appearance. This stage lasts about a month, at the end of which the larva grows to 5 millimeters.
Before the last stage, young crabs begin to look for a shell. If a crab comes out of the sea without a shell, it usually dies.
On land, young crabs are active mainly at night, and during the day they hide in various cracks and crevices.
These crabs are kept in horizontal terrariums. The soil is partially filled with water, but the water level should be very low, since land hermit crabs drown easily.
There are 10,000 species of decapods (crabs), the characteristic features of which are stalked, strongly bulging eyes, five pairs of legs and fusion of the head and chest into one continuous body part covered with a shell. As the crab grows, this shell bursts several times, and the crab “molts.” At this time, he is completely helpless and usually hides deep in the cracks of the rocks. Gradually, a new shell grows and hardens. On the ventral side of the crab's cephalothorax there are five pairs of legs, the first pair always with claws (the limbs of crabs are regenerated, that is, restored when lost, like the tails of lizards). Crabs breathe through their gills using oxygen dissolved in the water.Crabs are the most advanced representatives of crustaceans and since their appearance on earth 180 million years ago they have managed to conquer almost all possible habitats: from the abysses of the sea to the coasts, rivers, swamps, temperate forests, deserts and the highest mountains, such as the peaks of Kilimanjaro or Himalayan.
Almost two dozen species of crabs are found in the Black Sea. They are quite large, unusual in shape and habits. The average sizes of Crimean crabs are: body length up to 4 cm, width up to 5 cm, weight up to 50 g. Most of them live in the shallow coastal zone among algae.
Stone crab(Eriphia spinifrons) is the largest crab in the Black Sea. The width of its shell is 9-10 cm. It prefers to live deeper, although it is often found close to the shore, but this is only in deserted rocky places. If all bottom crustaceans are primarily scavengers (by the nature of their diet), then the stone crab, strong and aggressive, can be a fast and dexterous predator. In ambush he lies in wait for snails, worms and small fish. Its claws have monstrous strength - they snap like seeds, shells of mollusks and hermit crabs. Their muscle fibers at the molecular level differ from those of animals and humans (not in our favor). The color of the stone crab's shell is always the same as that of the stones among which it lives. Basically, it is a red-brown color, but stone crabs living among yellow sandstones are themselves quite light.
Hairy crab(Pilumnus hirtellus) is similar to the stone one, only its size is half as large. And the carapace is dark purple in color and covered with a thick layer of yellowish bristles-hairs. It lives closer to the shore, under rocks. Its diet is not too different from other crabs, but it is especially dangerous for various gastropods - it crushes their strong shells like nuts, only fragments fly.
marble crab(Pachygrapsus marmaratus) has a blue-green to dark brown carapace, mottled with many light stripes, reminiscent of variegated marble. Because of its dark color and long legs, it is often called the spider crab. This is the only Black Sea crab that runs out of the water and travels along coastal stones and rocks. At night, they can climb 2-5 m up rocks, and on gentle slopes move 5-10 m away from the water’s edge. However, at the first danger, they instantly take off and throw themselves into the water or the nearest crevice.
Mediterranean or herbal crab(Carcinus mediterraneus) is also an inhabitant of shallow water, prefers grass thickets, but can also live among stones. The greenish shell of the “grass” reaches a width of 7...8 cm. When meeting a predator, not relying much on its claws, it takes off headlong. And he runs, albeit sideways, but very quickly - at a speed of up to 1 m/s.
Another remarkable crab - lilac, or water lover(Xantho poressa). It is slower and is found not only in shallow water, but at depths of up to 15 m. The lilac crab prefers solitude. Buried in the sand, it can sit there for weeks without food or air.
Another fan of burrowing into the ground - swimming crab(Macropipes holsatus). This small crab has hind legs that are flattened like shoulder blades. With them he throws sand on himself. The crab also uses these unique flippers for swimming. This is the only Black Sea crab that can swim.
But the rarest crab of sandy soils is blue crab(Callinectes sapidus). He is also a swimmer. It appeared in the Black Sea only in the 60s of the twentieth century. from the Mediterranean, and arrived there with the ballast waters of ships from the east coast of the United States. But the Black Sea turned out to be too cold for the survival of the juveniles of this emigrant, so he is a very “rare bird” among us. The one in the photo caught in the shallow waters of Cape Bugas (underwater photography - S. Vshivtsev, 06/12/2010).
Or this amazing specimen - invisible crab. Invisible - because it is almost impossible to see it among the algae. This lean, long-legged crab is a master of camouflage. He carefully places small bushes of algae on his shell. So he wanders around unnoticed in his camouflage coat.
We also have a very small crab - pea crab. It usually lives among mussels, sometimes even inside the shell of a living mollusk. But you can find them on the rocks of shallow water, but it’s very difficult to see – an adult-sized crab can easily fit on a ten-kopeck coin.
Freshwater crab(Potamon tauricum Czern) is the most unusual crab of Crimea. He stands out not for his size, but for his lifestyle and origin. As the name implies, it does not live in the sea, but in fresh water: in mountain rivers and ponds associated with them. Since river crabs cannot spread thanks to currents, as the larvae of “normal” crabs do, they prefer to travel by land, usually at night and during rains. The most interesting thing is that in the Miocene, on foot, they crossed the entire continent (South-East Asia is considered the center of origin of the Potamon genus) all the way to Western Europe. During the Ice Age, the range of freshwater crabs was significantly reduced. The southern coast of Crimea is one of the refuges where they have survived to this day.