Cephalopods- the most unusual, largest, predatory and most perfect of mollusks. Cephalopods have reached a high degree of development. These are a kind of primates among the invertebrate inhabitants of the sea.
These animals were called cephalopods because they have tentacles, or “arms,” on their heads, which are also called “legs,” because octopuses (and squids too) often walk on them along the bottom, like on stilts. In addition, embryologists have found that the tentacles of cephalopods developed from the “leg” of their ancient ancestor - the primitive mollusk.
The sizes of cephalopods are very diverse. Some of them are among the smallest representatives of nekton, while others are the largest invertebrate animals in general. Decapoda sizes range from 1 cm (Idiosepius) to 18 m (giant squid of the genus Architeuthis).
Anatomical features. According to the number of tentacles and other characteristics, class cephalopods divided into two subclasses. Octopuses(subclass Octopoda) have 8 tentacles, and they wear the shell, or rather its underdeveloped remnant (two cartilaginous rods or cartilaginous formations of a different shape), not outside, but under the skin of the back.
U squid And cuttlefish(subclass of decapods - Decapoda) Not eight, like octopuses, but ten tentacles and the body is equipped with fins (regular octopuses do not have fins).
The body of the cuttlefish is flat, like a flat cake; in the squid it is cone-shaped, similar to a rocket. At the narrow end of the "rocket", where the tail would be, diamond-shaped fins spread out to the sides.
The shell of cephalopods is rudimentary: the cuttlefish has a calcareous plate, the squid has a chitinous feather, similar to the Roman sword gladius. Gladius is the name given to an underdeveloped squid shell.
The tentacles of cephalopods surround the mouth like a corolla. Suckers sit on them in one or two rows, less often in three or four. At the base of the tentacle, the suckers are smaller, in the middle there are the largest ones, and at the ends they are very tiny.
The mouth of cephalopods is small, the pharynx is muscular, and in the throat there is a black horny beak (brown in the squid), curved, like a parrot. A thin esophagus runs from the throat to the stomach. Along the way, it pierces the brain. Octopuses have a fairly large brain: it has fourteen lobes. The octopus's brain is covered with a rudimentary cortex of tiny gray cells - the control room of memory, and on top it is protected by a real cartilaginous skull. The cartilaginous skeleton of cephalopods is close in composition to the cartilage of vertebrates. Cartilage is extremely rare in invertebrate animals, but in cephalopods the cartilaginous internal skeleton is well developed. It not only surrounds the brain, but also supports the eyes with cupped projections. Supporting cartilages are also developed at the base of the tentacles, fins and in the buttons of the locking mantle apparatus.
Nervous system cephalopods are more complex than those of all other invertebrate animals. Its ganglia are very large and are so closely packed together that they essentially form a single nerve mass. Only in sections can one distinguish its constituent nodes.
The nervous system of cephalopods is highly specialized. In the subtlety of their feelings, accuracy of perception and complexity of responses and behavior, cephalopods are superior to many marine animals. Some researchers who have carried out the most advanced experiments on the behavior of cephalopods believe that there is much in common in the formation of conditioned reflexes and inhibition processes in the brain of humans and octopuses, although the centers that manage these functions are not homologous in origin. Brain cells tightly fit the esophagus on all sides. Therefore, octopuses (squids and cuttlefish too), despite their very predatory appetites, cannot swallow prey larger than a forest ant. But nature has endowed them with a grater, with which they prepare “puree” from crabs and fish. The fleshy tongue of cephalopods is covered with a hemispherical horny sheath. The cover is lined with tiny teeth that grind food, turning it into pulp. Food is moistened in the mouth with saliva and enters the stomach, then into the cecum, which is essentially the second stomach.
There is both a liver and a pancreas. The digestive juices they secrete are very active - they quickly digest food within four hours.
In other cold-blooded animals, digestion takes many hours; in flounder, for example, 40-60 hours.
Cephalopods have not one, but three hearts: the main one, consisting of one ventricle and two atria, drives blood throughout the body, and the other two (branchial hearts) push it through the gills. The main heart beats 30-36 times per minute.
Unlike other mollusks, cephalopods have an almost closed circulatory system: in many places (in the skin, muscles) arteries pass through capillaries directly into veins.
Their blood is unusual - blue! Dark blue when oxygenated and pale in the veins.
The color of animal blood depends on the metals that are part of the blood cells (erythrocytes) or substances dissolved in the plasma. Instead of hemoglobin, the blood of cephalopods contains hemocyanin. Copper, which is part of hemocyanin, gives their blood a bluish color.
We now move on to a description of the most interesting organ of cephalopods - the “jet engine”. Notice how simply, with what minimal use of material, nature solved a complex problem.
Below, at the “neck” of the squid (let’s take this mollusk as an example), a narrow gap is noticeable - the mantle opening. Some kind of tube sticks out from it, like a cannon from an embrasure. This is a funnel, or siphon, the “nozzle” of a jet engine.
Both the gap and the funnel lead into a vast cavity on the “belly”: this is the mantle cavity - the “combustion chamber” of a living rocket. Sucking water into it through a wide mantle slit, the mollusk then forcefully pushes it out through the funnel. To prevent water from flowing back through the gap, the squid closes it tightly using special “fastener buttons” when the “combustion chamber” is filled with sea water. Along the edge of the mantle opening there are cartilaginous mushroom-shaped tubercles. On the opposite side of the slot they correspond to indentations. The tubercles fit into the recesses and firmly lock, like buttons, all exits from the chamber, except one - through the funnel.
When the mollusk contracts its "abdominal" muscles (the muscles of the abdominal wall of the mantle), a strong stream of water shoots out from the siphon. The reactive force generated in this case pushes the squid in the opposite direction. The funnel is directed towards the end of the tentacles, so the cephalopod usually swims with the rear end of the body forward.
Jet shocks and suctions of water into the mantle cavity follow one after another with elusive speed, and the squid rushes like a rocket in the blue of the ocean.
Movement. Pumping water through itself, the cephalopod glides in the azure waves like a rocket. Squids have reached the highest perfection in jet navigation. Their body even copies the rocket in its external forms (or, better said, the rocket copies the squid, since it has indisputable priority in this matter).
The squid's body is long, cylindrical, extremely streamlined, pointed in front and behind. On its tail, a living rocket carries stabilizers - diamond-shaped fins. The tentacles on the outer side opposite the suckers are armed with powerful longitudinal carinae. When the tentacles are folded together, they resemble the tail of an arrow or an aircraft bomb.
By bending the bundled tentacles to the right, left, up or down, the squid turns in one direction or another. Since such a steering wheel is very large compared to the animal itself, its slight movement is enough for the squid, even at full speed, to easily dodge a collision with an obstacle. A sharp turn of the steering wheel - and the swimmer rushes in the opposite direction. So he bent the end of the funnel back and now slides head first. He bent it to the right - and the jet push threw him to the left. When moving quickly, the funnel always sticks out right between the tentacles and the squid rushes with its tail forward, as if a fast-moving crayfish, endowed with the agility of a horse, were running.
If a squid or cuttlefish swims slowly, undulating its fins, miniature waves run over them from front to back, and the animals glide gracefully, occasionally also pushing themselves with a stream of water thrown out from under the mantle.
Octopuses and some other octopuses (Eledone, Agronauta) can move along the bottom on their “hands”. For this purpose, the lateral pairs of arms are usually used, which, as a rule, are longer than the others. Therefore, octopuses move sideways along the bottom, like crabs. They rise on their arms, lower their torso down to the ventral pair of arms and turn the opening of the funnel to the side, usually to the right. In this position, octopuses surprisingly resemble an ugly big-headed man. Some researchers have observed octopuses moving along the bottom “on tiptoes” - at the very tips of tentacles extended vertically downward. At critical moments, octopuses, like squids, can develop great speed. Typically, octopuses swim relatively slowly. Joseph Seinl, who studied the migrations of octopuses, calculated: an octopus half a meter in size swims through the sea at an average speed of about 15 km per hour. Each stream of water thrown out of the funnel pushes it forward (or rather, backward, since the octopus swims backwards) by 2-2.5 m.
Sense organs. If, writes one scientist, you asked a zoologist to indicate the most striking feature in the development of the animal world, he would not name the human eye (of course, this is an amazing organ) and not the octopus eye, but would draw attention to the fact that both of these eyes, the eye a person and the eye of an octopus are very similar." They are similar not only in their structure, but often even in their expression - a strange fact that has always amazed naturalists.
The eye of an octopus is not much different from the eye of a mammal or even a human. But there are some differences: for example, the cornea of most cephalopods is not solid, but is pierced in front by a small (cuttlefish) or rather wide (squid) hole. The lens is not elliptical, but round, divided in half by a thin epithelial plate. “In addition,” writes the famous Soviet researcher V.A. Dogel, “in the eye of Cephalopoda there are adaptations to vision in both stronger and weaker lighting. The cells of the retina contain brown granular pigment. In bright daylight, the latter is distributed throughout cell and thus partly protects the cell from too much light. At night, all the pigment is concentrated only at the base of the cell, the sensitivity of which increases as a result."
Accommodation (setting vision at different distances, focusing) in humans is achieved by changing the curvature of the lens, and in cephalopods - by removing or bringing it closer to the retina, just as the lens moves in a camera.
None of the inhabitants of the sea have such keen eyes as the octopus and its relatives. Only the eyes of an owl, a cat, and a human can compete with them.
On one square millimeter of the retina octopus there are about 64 thousand visual elements that perceive light, cuttlefish even more - 150 thousand, squid- 162 thousand, y carp- 50 thousand, y cats- 397 thousand, y person- 400 thousand, and owls even 680 thousand
And the size of the eyes of cephalopods is record-breaking. The cuttlefish's eye is only ten times smaller than itself, and giant octopus eyes the size of a small wheel: 40 cm in diameter! A thirty-meter blue whale's eye does not exceed 10-12 cm in length (200-300 times smaller than the whale itself).
Even blinded octopuses see the light. Or rather, they feel it over the entire surface of the body. They have a very sensitive skin: tactile, photosensitive, olfactory and taste cells are scattered in the skin.
The octopuses recognized the taste of the food offered by the experimenters not only with their tongue. And even mainly not with the tongue, but with the “hands”. The entire inner surface of the tentacles (but not the outer) and each sucker are involved in tasting food. To find out whether the proposed dish matches its taste, the octopus tastes it with the tip of its tentacles. The octopus's sense of taste is so subtle that it apparently recognizes its enemies by taste.
McGinity, an American oceanographer, released a drop of water from a pipette near the octopus, which he collected in another aquarium near the moray eel, the octopus's worst enemy. The octopus acted according to the simulated situation: it got scared, turned purple and took off running.
However, it is still unknown by what sense he recognized the enemy - taste or smell. The difference between these feelings is small, and in the octopus there may be none at all. We already know that the taste organs, capable of distinguishing sweet from sour, bitter from salty, are located in the octopus, in addition to the tongue and lips, on the inside of the tentacles. But with its tentacles, the octopus also perfectly recognizes odors: the smell of musk and other odorous substances. What sense notifies, for example, a blind octopus of where a dead fish lies? He unmistakably finds her even at a distance of one and a half meters. Taste? Smell?
A well-fed octopus usually does not show interest in food - it is not a glutton, but a tentacle cut off from the same octopus, deprived of brain control, stubbornly crawls for a tasty morsel.
Apparently, in octopuses (and in squid and cuttlefish) taste and smell are inseparable.
It remains to mention one more sense - hearing. Do octopuses hear or are they deaf to everything?
They probably can hear a little if you shout in their ear. However, this is not easy to do: it is not easy to find an octopus “ear” from the outside. There are no external signs that would indicate its existence. But if we cut into the cartilaginous skull of an octopus, inside we will find two bubbles with lime lenses enclosed in them. These are statocysts, the organs of hearing and balance. The impacts of sound waves (not only, perhaps, only; strong impacts) vibrate the calcareous pebbles, they touch the sensitive walls of the bubble, and the animal perceives the sound, apparently as an indistinct hum.
The lime crystals also tell the octopus about the position of its body in space. Octopuses with cut out statocysts lose their orientation: swimming with their backs down, which normal animals never do, otherwise they will suddenly start spinning like a top or confuse the top and bottom of the pool.
Lifestyle. All cephalopods are exclusively marine animals. They live only in oceans and full-salt seas. They are especially numerous in the tropical and subtropical regions and in temperate latitudes. The salt content in sea water must be at least 33%. (This is why cephalopods are not found in our Black Sea, whose salinity is almost half that of the ocean.)
Coastal species of cephalopods tolerate desalination better and can apparently live in water with salinity reduced to 33%. But inhabitants of the open sea, such as the squid Brachioteuthis rusei, feel bad even at salinities below 35%.
In the ocean, cephalopods are found from the abyssal depths to the surface, from the tropics to the polar seas. Some of them, like many fish, swim freely in the water column, others prefer to hide at the bottom.
Most squids and pelagic octopuses are typical representatives of nekton, but there are also planktonic organisms among them. Such, for example, is the rod-shaped Doratopsis vermicularis, which lives in the open sea in a community of jellyfish and salps. This squid is completely transparent and resembles a piece of ice floating in the water. The larvae of almost all cephalopods lead a planktonic lifestyle; some of them at this stage resemble D. vermicularis in their shape. These are the young individuals of Chiroteuthidae, some Cranchidae.
Small Argonauts(Argonauta hias) should also be classified as representatives of macroplankton. Their females, burdened with a shell, are largely dependent on the will of the wind and waves in their movements.
Finally, cephalopods (Sepiolidae, Octopodidae, Cirroteuthidae) lead a benthic, coastal and sedentary lifestyle. Cuttlefish prefer sandy or muddy soils. Here they lie for a long time at the bottom, half buried in the sand, and lie in wait for prey. Having descended to the ground, Sepia agitates it with wave-like movements of its fins; As the silt settles, it covers it with a thin layer and camouflages it perfectly. The ability to change color to match surrounding objects helps it remain invisible on any ground.
Many other representatives of the suborder also stay near the bottom cuttlefish(Sepiella, Sepiola, Russia). The vast majority of octopuses are also bottom and coastal animals.
Octopuses prefer rocky soils. They hide among stones or in rock crevices. Some of them (Paroctopus conispadiceus, Eledone moschata) also settle on sandy soils. As observations of octopuses kept in aquariums have shown, even on sandy soil they make a shelter for themselves from stones that they bring from afar.
Squid- inhabitants mainly of the open seas.
Nutrition. The main food of cephalopods is fish, crabs and shells. But many species (especially deep-sea ones) also eat carrion. They also eat each other. Small squids and octopuses live in constant fear for their lives, which are threatened by the greed of their larger counterparts. This is one of the circumstances that makes it difficult to keep octopuses in aquariums: larger octopuses eat smaller ones. And hunger is not always the cause of cannibalism. Therefore, even Aristotle, reflecting on bad customs polypus, decided that they eat each other in order to maintain their vitality: an octopus that has not tasted octopus meat seems to wither and die.
An even stranger habit of octopuses is autophagy, self-devouring.
Naturalists have sometimes observed how octopuses kept in captivity suddenly, for no apparent reason, began to eat themselves! They bit the tentacles clean off and... died.
Although cephalopods are very voracious, they can starve for a long time if necessary. In aquariums, octopuses sometimes lived without food for several weeks, and brooding females do not eat anything for about two months, sometimes more, until they hatch their young.
Protective devices. Without exception, all cephalopods are predators, and the predators are very voracious. The size of the prey does not bother them: cephalopods even attack animals several times their size. These are, without a doubt, the most aggressive and warlike inhabitants of the seas. Cephalopods are connected with all the inhabitants of the ocean by invisible but strong threads of biological relationships. They eat many fish and crabs and themselves provide food for millions of predators that devour them: here are fish - sharks, moray eels, tuna, mackerel, cod; there are also birds - albatrosses, skuas, penguins and sea animals - whales, dolphins, seals.
Needless to say, there are many enemies. But cephalopods do not give up without a fight: they are well armed. Their tentacles are lined with hundreds of suckers, and many squids also have claws, sharp and curved, like those of cats. There are no teeth, but there is a beak. Horny, hooked, it easily bites through fish skin and crab shells, and pierces through even the durable shells of bivalve mollusks. A cuttlefish can crush with its beak the shell of a large crayfish or the skull of a fish twice its size. Four or six kilogram squids easily bite through the wire line of a spinning rod, and therefore experienced spinning anglers, wanting to “fish” for octopuses, use a strong steel core. Pierced by a spear, the squid gnaws it with its beak with such fury that only splinters fly. Dosidicus hunt four-pound tunas and eat the giant fish clean, leaving only the head intact.
The following episode speaks about the strength of the tentacles of cephalopods.
The Brighton Aquarium in England experimented with a small, foot-sized octopus. The attendant lowered a crab tied to a string into the pool, and the naturalist watched below, sitting by the glass. As soon as the crab touched the water, the octopus jumped out of its corner like a bullet and grabbed it, tearing the string out of the hands of the attendant.
“Give me another crab,” said the naturalist. “And hold it tight.”
The second crab was lowered. The octopus looked at him lustfully, but did not want to part with his first prey. The crab, swaying, approached. Two feelings seemed to be fighting in the octopus - greed and prudence. Greed has triumphed. Holding the caught crab with seven hands, he reached up with the eighth and grabbed a new treat. A jerk, another jerk. The octopus pulled a third time and the string broke!
Autotomy (self-mutilation) - the oldest means of life insurance - is also in the octopus's arsenal of protective devices. The eight long arms that explore every inch of unfamiliar space when the octopus goes out to hunt for prey are more often endangered than other parts of the body.
The tentacles are strong - by grabbing one, you can pull the entire octopus out of the hole. This is where the octopus “autotomizes” itself: the muscles of the captured tentacle contract spasmodically. They contract with such force that they tear themselves apart. The tentacle falls off, as if cut off by a knife. The predator receives it as a ransom for his life.
The octopus Octopus defilippi has mastered the art of autotomy. Grabbed by the hand, he immediately breaks up with her. The tentacle wriggles desperately - this is a false maneuver: the enemy rushes at it and misses the main target. The rejected tentacle twitches for a long time and, if released, even tries to crawl and can attach itself.
In the process of evolution, cephalopods acquired an even more amazing miracle weapon - an ink bomb. Instead of a piece of living flesh, the squid throws out a crude fake of its own person in front of its open mouth to devour it. The squid seems to split into two before our eyes and leaves its ethereal double to the enemy, and quickly disappears.
In a moment of danger, cephalopods eject a stream of black liquid from the funnel. The ink spreads in the water like a thick cloud, and under the cover of a “smoke screen” the mollusk more or less safely escapes, leaving the enemy to wander in the dark.
The ink contains organic dye from the melanin group, similar in composition to the pigment with which our hair is colored. The shade of ink is not the same in all cephalopods: in cuttlefish it is blue-black (in a strong dilution of the sepia color), in octopuses it is black, in squid it is brown.
Ink is produced by a special organ - the pear-shaped outgrowth of the rectum. It is called the ink sac. This is a dense bubble, divided into two parts by a septum. The upper half is reserved for the reserve tank, which stores ink, the lower half is filled with the tissues of the gland itself. Her cells are filled with grains of black paint. Old cells are gradually destroyed, their paint dissolves in the juices of the gland - ink is obtained. They enter the “warehouse” - they are pumped into the upper bottle, where they are stored until the first alarm.
Not all the contents of the ink sac are sprayed out at once. An ordinary octopus can set a “smoke screen” six times in a row, and after half an hour it completely restores the entire spent supply of ink. The coloring power of the ink liquid is unusually high. In five seconds, the cuttlefish paints all the water in a tank with a capacity of 5.5 thousand liters with spewed ink. And giant squids spew out so much inky liquid from the funnel that the sea water becomes cloudy for hundreds of meters!
Cephalopods are born with a sac filled with ink. One tiny cuttlefish, barely emerging from the shell of the egg, immediately colored the water with five ink volleys.
And here is an unexpected discovery made by biologists. It turned out that the traditional idea of a “smoke screen” of cephalopods should be thoroughly revised. Observations have shown that the ink discarded by cephalopods does not dissolve immediately, not until it hits something. They hang in the water as a dark, compact drop for a long time, up to ten minutes or more. But the most striking thing is that the shape of the drop resembles the outlines of the animal that threw it out. The predator grabs this drop instead of the fleeing prey. That's when it "explodes" and envelops the enemy in a dark cloud. The shark becomes completely confused when a school of squid simultaneously, like a multi-barrel mortar, throws out a whole series of “ink bombs”. She rushes from side to side, grabs one imaginary squid after another, and soon the whole thing disappears in a thick cloud of ink scattered by her.
The zoologist put the squid in a tub and tried to catch it with his hand. When his fingers were already a few inches from the target, the squid suddenly darkened and, as it seemed to Hal, froze in place. The next moment, Hal grabbed... an ink model, which fell apart in his hands. The deceiver was floating at the other end of the tub.
Hal repeated his attempt, but now watched the squid closely. When his hand approached again, the squid darkened again, threw out a “bomb” and immediately became deathly pale, then darted invisible to the far end of the tub.
What a subtle maneuver! The squid didn’t just leave its image in its place. No, it's a dress-up scene. First, it attracts the enemy's attention with a sharp change in color. Then he immediately replaces himself with another dark spot - the predator automatically fixes his gaze on it - and disappears from the scene, changing his “outfit”. Please note: now his color is not black, but white.
The ink of cephalopods has another amazing protective property. McGinity, an American biologist, conducted a series of experiments on the Californian octopus and moray eel. And this is what I found: octopus ink, it turns out, paralyzes the olfactory nerves of predatory fish!
After a moray eel has been in an ink cloud, it loses the ability to recognize the smell of a lurking mollusk, even when it stumbles upon it. The paralyzing effect of the octopus drug lasts for more than an hour!
The ink of cephalopods in high concentrations is dangerous for themselves. Gilpatrick made the following experiment: he planted a small octopus in a bucket of sea water and added ink extracted from five of the same mollusks to it. Three minutes later the octopus was dead.
Li-Xuer performed a similar experiment: he put two small octopuses into a five-liter vessel. They quickly turned the water black, emptying their ink sacs, and... died ten minutes later.
In the sea, in the wild, the octopus avoids the harmful effects of its weapons, quickly leaving the poisoned place. In a confined space, it is not easy for him to do this. In pools with poor water changes, the concentration of ink quickly exceeds the permissible norm, poisons the captives, and they die.
Is cephalopod ink dangerous for humans?
Let's ask a spearfishing expert like James Aldridge to answer this question. He says: “I behaved so freely with the octopus that I received a stream of ink right in the face. And since I was not wearing a mask, the liquid got into my eyes and blinded me. The world around me, however, did not darken from this, but turned into a wonderful amber color. Everything around me seemed amber in color as long as the film of this ink remained in front of my eyes. This lasted for about ten minutes or so. This incident did not affect my vision."
In the same book, Aldridge writes: “Octopuses surprisingly quickly and harmoniously color themselves to match the color of the surrounding area, and when you shoot one of them and kill or stun it, it does not immediately lose the ability to change color. I observed this myself once, having laid harvested octopus onto a piece of newspaper for cutting. The killed octopus instantly changed color, becoming striped, white and black striped!"
After all, he lay on a printed page and copied its text, imprinting on his skin the alternation of black lines and light spaces. Apparently, this octopus was not completely dead; its eyes still perceived the shades of the fading colors of the solar world, which it was leaving forever.
Even among higher vertebrates, few have the invaluable gift of changing skin color at whim or necessity, repainting themselves, copying the shades of external decoration.
All cephalopods have elastic, rubber-like cells under their skin. They are filled with paint, like watercolor tubes. The scientific name for these wonderful cells is chromotophores.
Each chromatophore is a microscopic ball (when at rest) or a pinpoint disk (when stretched), surrounded at the edges, like sun rays, by many subtle muscles - dilators, i.e. dilators. Few chromatophores have only four dilators; usually there are more - about twenty-four. Dilators, contracting, stretch the chromatophore, and then the paint contained in it occupies an area tens of times larger than before. The diameter of the chromatophore increases sixty times: from the size of a needle point to the size of a pinhead. In other words, the difference between a contracted and an expanded colored cell is as great as between a two-kopeck coin and a car wheel.
When the dilator muscles relax, the elastic shell of the chromatophore takes its previous shape.
The chromatophore stretches and contracts with exceptional speed. It changes its size in 2-3 seconds, and according to other data even faster - in 1/2 - 1/7 second.
Each dilator is connected by nerves to brain cells. In octopuses, the “control room”, which manages the change of scenery, occupies two pairs of lobe-shaped lobes in the brain. The front pair controls the color of the head and tentacles, the back pair controls the color of the body. Each blade controls its own, i.e., right or left, side. If you cut the nerves leading to the chromatophores on the right side, then on the right side of the mollusk one constant color will harden, while its left half will “play” with colors of different tones.
What organs correct the functioning of the brain, causing it to change the color of the body exactly in accordance with the background of the surroundings? Eyes. The visual impressions received by the animal travel through complex physiological channels to the nerve centers, and they send appropriate signals to the chromatophores: they stretch some, contract others, achieving a combination of colors that is most suitable for camouflage. An octopus that is blind in one eye loses the ability to easily change shades on the eyeless side of the body. Removal of the second eye results in almost complete loss of the ability to change color.
The disappearance of color reactions in a blinded octopus is incomplete, because the change in color also depends on the impressions received not only by the eyes, but also by the eyes. suction cups. If you deprive an octopus of its tentacles or cut off all the suckers, it turns pale and, no matter how it puffs itself up, it cannot turn red, green, or black.
Cephalopod chromatophores contain black, brown, red-brown, orange and yellow pigments. The largest are dark chromatophores; in the skin they lie closer to the surface. The smallest ones are yellow. Each mollusk is endowed with chromatophores of only three colors: brown, red and yellow or black, orange and yellow. Their combination, of course, cannot give the full variety of shades for which cephalopods are famous. Metallic shine, violet, silver-blue, green and bluish-opal tones impart to their skin a special kind of cells - iridiocysts. They lie under a layer of chromatophores and hide many shiny plates behind a transparent shell. Iridiocysts are filled, like funhouses in parks, with rows of “mirrors”, a whole system of “prisms” and “reflectors” that reflect and refract light, decomposing it into the magnificent colors of the spectrum.
An irritated octopus from ash-gray in a second can turn black and turn into gray again, demonstrating on its skin all the subtle transitions and nuances in this range of colors. The countless variety of shades in which the octopus's body is painted can only be compared with the changing color of the evening sky and sea.
If it occurred to someone to organize a worldwide chameleon competition, the cuttlefish would probably win the first prize. In the art of camouflage, no one can compete with her, not even an octopus. The cuttlefish adapts to any soil without difficulty. One minute she was striped like a zebra, she sank onto the sand and immediately changed her color - she became sandy yellow. She floated over the white marble slab and turned white. Here she lies on the pebbles, illuminated by the sun, her back is decorated with a pattern of light (to match the sun’s glare) and gray-brown spots. On black basalt the cuttlefish is black as a raven, and on the mottled stone it is piebald.
Researcher Holmes described nine color patterns that cuttlefish use to express feelings (three patterns) and camouflage (six patterns).
Striped or spotted coloring, composed of sharply contrasting elements (black stripes on a white skin, or white on a black, or black spots on a yellow background), is found in many animals: the tiger, leopard, jaguar, ocelot, giraffe, kudu and bongo. . okapi, fish, snakes, butterflies.
Have you noticed that all of these animals have stripes and spots in rows across their bodies? After all, this is not accidental. The fact is that the transverse stripes, reaching the boundaries of the silhouette, suddenly end. The solid contour line is dissected by alternating white and black fields of color, and the animal, losing its usual outlines to the eye, merges with the background of the area. People also resort to the same method of camouflage when they paint military installations with light and dark spots that break up the contours of the structure being camouflaged.
If black and white stripes go not across, but along the contours of the body, then they do not separate, but, on the contrary, emphasize them. Easily visible coloration is beneficial to poisonous or foul-smelling creatures, so that predators do not grab them by mistake. Such are, for example, the salamander and the skunk: they actually have stripes running along the body.
Contrasting stripes, breaking up the silhouette of the cuttlefish, help it blend in with the color of any soil. After all, the zebroid pattern is a universal camouflage.
Even newborn octopuses are not left unarmed. While their own means of combat have not yet developed, the little ones arm themselves with the “poisonous arrows” of jellyfish.
Jellyfish sting like nettles. Their tentacles are lined with microscopic batteries of stinging vesicles - nematocysts.
The German scientist Adolf Näf caught larvae of tremok-topus - miniature pelagic octopuses - in the Mediterranean Sea and was surprised to discover that each larva held in front of it in its weak “hands” a barrier of scraps of jellyfish tentacles.
Nef decided that the stinging nematocysts that line the jellyfish's tentacles serve as a defense weapon for octopus babies.
Does any other living creature possess such a variety of protective instincts and such perfect “combat technology” as cephalopods?
Organs of luminescence. Jean Baptiste Verani loved to come to the seashore when fishermen returned with their catch. Their boats brought strange animals. One day, near Nice, he saw a crowd of people on the shore. A completely unusual creature was caught in the net. The body is thick - like a sac, like an octopus, but there are ten tentacles, and they are connected by a thin membrane, like an umbrella.
Verani lowered the bizarre captive into a bucket of sea water and “at that very moment,” he writes, “I was captured by the amazing spectacle of sparkling spots that appeared on the skin of the animal. It was either a blue ray of sapphire that blinded me, or an opal ray of topaz , then both rich colors mixed in a magnificent radiance that surrounded the mollusk at night, and it seemed one of the most wonderful creations of nature."
Thus, Jean Baptiste Verani, a young French naturalist, discovered in 1834 the bioluminescence of cephalopods. He was not mistaken when he decided that the numerous bluish dots on the animal’s body were luminous organs (photophores). In a deep sea squid histioteuthis, which Verani studied, about two hundred of these “flashlights”; some of them reach a diameter of 7.5 mm - real spotlights! The design of a photophore resembles a spotlight or a car headlight. And its shape is approximately the same - hemispherical. The organ is covered on all sides, except for the luminous surface facing outward, with a black, opaque layer. Its bottom is lined with shiny fabric. This is a specular reflector. Directly in front of it is a light source - a photogenic body, a mass of phosphorescent cells. The top of the “headlight” is covered with a transparent lens, and on top of it is a diaphragm (a layer of black cells - chromatophores). Crawling onto the lens, the chromatophores close it and the light goes out.
The luminous organs of squids are endowed with a number of other optical devices.
U calliteuthys, for example, light emanating from a photogenic mass crosses an obliquely placed “mirror”. Special muscles turn the “mirror” in different directions, and the light beam changes its direction.
Photophores also contain light filters - screens made of multi-colored cells. Sometimes a color reflector plays the role of a light filter. It is not uncommon for one mollusk to have lighting fixtures of ten different designs.
Some squids are literally dotted with large and small photophores, not only on the outside, but also on the inside. Many wear a "belt of fire gems" under their robes. The light from the shining "stones" penetrates outward through transparent "windows" in the skin and muscles of these animals.
Often photophores sit on the eyes - on the eyelids or even on the eyeball itself, and sometimes they merge into continuous stripes surrounding the eye orbit with a luminous semiring.
U taxis And bathotauges, bizarre inhabitants of the deep, their eyes sit on long stalks and each eye is endowed with powerful photophores. These squids, notes Frank Lane, have two optical devices at once - rangefinders and searchlights.
Photophores in the eyes have been found not only in squids, but also in some deep-sea crayfish and fish. Obviously, a light source close to the eyes helps to view nearby objects. Far vision at depth is out of the question.
The luminous organs of cuttlefish have a different structure than those of squids: they do not contain a solid mass of photogenic cells.
Glowing cuttlefish lanterns are the most economical light bulbs in the world. They burn for years without recharging. The light-producing fuel multiplies faster than it can burn. Cuttlefish carry a whole world of glowing bacteria in a special capsule inside their bodies.
The “bubble” with bacteria is immersed in the recess of the ink sac. The bottom of the cavity is lined, like mother of pearl, with a layer of shiny cells. This is a specular reflector. The cuttlefish's "pocket flashlight" also has a collector lens. Gelatinous and transparent, it lies on top - on a bag with bacteria.
There is also a switch for the flashlight. When it is necessary to “put out” the light, the cuttlefish releases several droplets of ink into the mantle cavity. The ink covers the bag of bacteria with a thin film, as if throwing a black blanket over it, and the light goes out.
Two-horned sepiola named by zoologists Chochin-iku- a miniature creature, the size of a thumbnail, that hunts for crustaceans in the ocean waters near the coast of Japan and the Kuril Islands. At night, sepiola glows. A radiant halo surrounds her tiny body, and the shining baby soars above the black abyss of the sea, like a living star.
Sepiola is not difficult to catch. A simple net on a long stick is suitable for this. Turning her over on her back and carefully bending the edge of her mantle, we will see a large, two-horned “bubble” (hence the name of the baby). It lies on the ink sac, covering it entirely, and is filled with mucus. This is a mycetome - a “cage” for luminous bacteria.
Observations have shown that Chochin-ika, saving his life, throws “liquid fire” at the enemy - instantly a luminous cloud flares up around the animal. A predator trying to grab a cuttlefish goes blind. Meanwhile, the mollusk hurries to hide in a safe place.
However, he achieved the best results in the “flamethrower” art heteroteuthys- “pyrotechnician”, which Aristotle wrote about. Heteroteuthis lives in the Atlantic Ocean and the Mediterranean Sea at shallow depths - up to 500-1000 m. The heteroteuthis mycete is equipped with a large reservoir. The walls of the tank are elastic, and when the surrounding muscles contract, millions of bacteria erupt outward, flashing bright fireworks in the depths of the sea.
The luminous organs of cephalopods work very economically: 80 and even 93% of the light they emit are short-wave rays and only a few percent are thermal rays. In an electric light bulb, only 4% of the supplied energy is converted into light, and 96% into heat. In a neon lamp, the efficiency is slightly higher - up to 10%.
Reproduction. During reproduction, male cephalopods use one of the tentacles - it is called a hectocotylus - to remove sperm packaged in “packages” from the “sinus” (from the mantle cavity) and transfer it to the mantle cavity of the female. The packages of sperm are called spermatophores. Their shape is varied, but usually resembles a bottle, a tube, or a “Cossack saber.” Their sizes range from 3 mm to 115 cm (for the octopus Octopus dofleini). Spermatophores are stored in a special container - the Needham's organ. They lie in a compact pack parallel to each other. During reproduction, jets of water carry them out through a funnel. Here the mollusk picks them up with one of its hands and “presents” them to the female.
The design of the spermatophore is quite complex and somewhat resembles the design of a mine. The main part of its “explosive” apparatus is an elastic spring coiled into a large number of turns and a special plug - the “fuse” of a biological “mine”. After the spermatophore enters the mantle cavity of the female, the spermatophore plug swells and bursts, as if exploding, the spring unfolds with force and throws out the sperm.
Romanian biologist Emil Racovita was the first researcher (not counting, perhaps, Aristotle) who managed to observe mating octopuses at the end of the last century. The animals sat at some distance from each other. The male held the female with one of his eight arms, and with a hectocotylus tentacle he took spermatophores from his mantle cavity and transferred them to the mantle cavity of the female.
In many species of octopuses, the hectocotylus has the shape of a flexible hand equipped with two fingers, of which one is very long (ligula), the second is very short (calamus). These fingers capture the spermatophores. However, the mechanism of action of hectocotylus is not yet clear enough. The male deep-sea octopus Vampyroteuthis infernalis has no hectocotyls at all.
A highly remarkable adaptation to fertilization is observed in small pelagic octopuses from the group Argonautidae. A very large hectocotylus in male Argonauts and Tremocotopus develops in a special sac between the fourth and second arms of the left side. A mature hectocotylus breaks away from the male’s body and, wriggling, swims away in search of a female of its species. Having found her, the hectocotylus crawls into her mantle cavity, where one or two spermatophores contained inside it “explode” and fertilize the eggs. This will be discussed in more detail in the chapter on the Argonauts.
In larger octopuses of the genus Ocythoe, sperm-filled hectocotyles also detach from the male’s body, swim on their own and, having found a female, crawl into the cavity of her mantle and attach themselves there.
Spermatophores of other cephalopods are usually transferred by the male directly into the mantle cavity of the female and placed there near the entrance to the oviduct. However, this is not observed in all Cephalopoda, but mainly in octopuses. In more primitive forms (Nautilus, Sepiidae, most Loliginidae, some Sepiolidae, and squids, particularly Ommastrephidae), spermatophores are attached by the male to the folds or seminal receptacles of the female's oral cone.
Fertilization of cephalopod eggs mostly occurs during their laying, when they leave the oviduct and enter the mantle cavity, or when, carried by a current of water through a funnel, they pass past the mouth. In this case, the sperm is captured by the gelatinous membrane of the eggs or the mucous mass covering them. Only in Argonautidae are eggs fertilized in the oviduct, so that advanced stages of egg development are found in it, which by the time of laying have already undergone at least fragmentation. In Ocythoe, the development of eggs during their stay in the oviducts goes so far that this octopus, according to some information, gives birth to live young.
It has been reliably established that viviparous forms were already among ammonites.
In the living chamber of the shell of the Upper Jurassic Oppelia sterospis, 60 small aptychia were found, i.e., the remains of the shells of 60 young ones. Fingerprints of others known ammonites(Dactylioceras commune. Harpoceras lythense) together with juveniles inside the shell.
It is generally accepted that in cephalopods, egg fertilization is internal. But this is not true. In many cephalopods, in which spermatophores are attached to the female's oral cone, fertilization occurs outside the animal's body. But even in those species in which the attachment of spermatophores and fertilization of eggs occurs inside the mantle cavity, we cannot consider the latter internal, since the mantle cavity is not an internal cavity of the body. It is constantly filled with water, and the eggs in it remain, essentially, in external environmental conditions. In this respect, it can be compared to the pouch of marsupials, although it has a completely different meaning. Only in those species of cephalopods in which egg fertilization occurs in the oviduct (Agronauta ocythoe) is it truly internal.
Thus, within the class Cephalopoda we encounter three different types of reproduction, representing a sequential development of the same process: external fertilization, internal fertilization and viviparity.
Squid eggs, while still in the female’s oviducts, are “packed” into long gelatinous threads, which are pushed out through the funnel. Then the female turns upside down, stands almost vertically and, quickly twitching her tail fins, jerkily moves along the bottom on her arms, without, however, releasing the eggs from them. So, balancing on the tips of the tentacles, it walks upside down until it bumps into some protruding object - a shell, for example, or a stone. Then the female feels this object for two to three seconds, as if examining its suitability as an anchor for eggs, after which she attaches an egg thread to it.
During the breeding season, some cuttlefish secrete what appears to be a luminous mucus. Females swim near the surface, males rush towards them from the depths, like luminous arrows.
The ways in which cuttlefish attach their eggs to underwater objects have puzzled many naturalists who have found their egg-laying sites. Each egg hangs on a long stalk - a stalk. The stems of all the eggs are so carefully intertwined with each other and tightly wrapped around the seaweed that it seems that even a person with his dexterous fingers could not have done it more accurately. Attaching the eggs requires very complex movements of the mollusk's tentacles.
Number of species and geological history. Zoologists have already described about six hundred species of cephalopods (each large group - squid, cuttlefish, octopuses - has approximately two hundred species). Each new exploration of the sea brings, as a rule, new species of these animals unknown to science.
And there was a time when the seas and oceans of our planet were literally teeming with cephalopods. Paleontologists already know more than 11 thousand fossil species.
The oldest of the cephalopods were nautiloids. From them came the ammonites, named after the ancient Egyptian god Ammon, whom the priests depicted with the head of a ram. A coiled ram's horn, similar to an ammonite shell, was the emblem of the ram god.
Both nautiluses and ammonites lived in massive spiral or straight shells. Slowly crawling along the bottom, the animals carried them with difficulty. Gradually, in the process of evolution, extensive chambers filled with gas developed in the shell - the house immediately became light as air, and turned from a sinker into a float. Animals, like inflatable boats, now drifted freely on the waves and settled across all seas and oceans.
Among the ancient nautiluses and ammonites there were also babies no larger than a pea. Others carried dugout shells the size of a small tank. Mollusk endoceras lived, for example, in a shell that looked like a five-meter cone. It could easily accommodate three adults.
Ammonite shell Pachydiscus- a monstrous wheel with a diameter of 3 m! If all the turns were untwisted, then it would be possible to build a staircase from it to the fourth floor. Never before or now has anyone had such huge shells.
For four hundred million years, ammonites and nautiluses swam serenely on the waves. Then suddenly they died out. This happened eighty million years ago, at the end of the Mesozoic era. Science has not established with certainty when and how belemnites, the closest relatives of squid and cuttlefish, originated from nautiluses. Two hundred million years ago they already roamed the seas.
Belemnites were almost indistinguishable from squids. Maybe just the specific gravity of its shell: it was heavy, soaked in lime. How this happened is unknown, but the shell gradually moved from the surface of the mollusk into it.
The belemnites seemed to swallow her, or, better said, devoured her. The shell was covered with folds of the body on all sides and ended up under the skin. Now it was no longer a house, but a kind of spine. But the spinal shell retained its ancient shape for a long time - a hollow cone divided into chambers with a massive tip. Outwardly, it resembled a spear or javelin.
This is where belemnites got their strange name: belemnon (Greek) - dart.
Belemnites became extinct a little later than ammonites. Squids originated from belemnites. The kingdom of dinosaurs had not yet reached its greatness, and squids already lived in the sea. Octopuses appeared later - a hundred million years ago, at the end of the Cretaceous period 3.
Well, cuttlefish are very young (in the evolutionary sense) creatures. They began their development at the same time as horses and elephants - just some fifty million years ago.
We can judge what the ancestors of octopuses looked like not only from their fossilized shells, but also from living specimens: six species from the oldest genus of sea patriarchs have survived to this day. Surviving nautiluses live in the southwest Pacific Ocean: off the Philippines, Indonesian Islands and Northern Australia.
In the body structure of modern nautiluses, many primitive features characteristic of the ancestors of all cephalopods have been preserved.
For example, they live in shells, like snails, they have very imperfect eyes, the funnel consists of two blades rolled into a tube, the edges of which are not fused. Nautiluses have 4 kidneys (nephridia), 4 gills and 4 gill hearts. Therefore, zoologists have classified them into a subclass of four-gill cephalopods, and octopuses, squids and cuttlefish, which have only two gills, into