Class Cephalopods belongs to highly organized sea ​​mollusks. Scientists count about 675 modern species, as well as about 11 thousand extinct. They have 8 arms on their heads, and cuttlefish and squids have a pair of tentacles. The length of their body including tentacles can vary from 15 centimeters to 5 meters (in some squids up to 20 meters). Class cephalopods widespread in almost all seas of our planet. They live both at the bottom and in the water column (in upper layers are quite rare).

Cephalopods: behavior and lifestyle

These animals serve as food for many fish, as well as marine mammals. Some of them are edible and are considered commercial fish. Cephalopods include squid, cuttlefish, octopuses, and among the extinct ones it is worth noting belemnite, ammonite and others.

Cuttlefish

move reactively, i.e. they suck in and forcefully spit out water and glide through the waves like living rockets. All representatives who are included in class cephalopods - feed on fish, as well as other inhabitants of the seas. There are also cases when they eat their own kind (cases of cannibalism). But one of the strangest habits of cephalopods can be considered eating their own body.

Sometimes there have been cases where octopuses that were kept in captivity suddenly began to eat themselves, biting off their tentacles, and then died. It is worth noting that class cephalopods They also have such a “means” for protecting themselves from enemies as tearing off their limbs. If an octopus hiding in its hole is caught by a tentacle, it will immediately “throw off” it.

Octopus

When any danger approaches, all cephalopods eject a stream of black caustic liquid into the water. This “ink” blurs in the water, and under this rather thick cloud of black color the mollusk safely hides or runs away.

Cephalopods are the real underwater brothers of chameleons: they can very quickly change the color of their skin. If you make an octopus very angry, it will instantly change gray of its cover to black, and when it calms down, it will turn gray again to the previous normal color of its body.

Cuttlefish

Cephalopods: nautiluses

Among the simplest animalsclass cephalopods shellfish are nautiluses, or otherwise pearl ships. It is worth noting that nautiluses, compared to most cephalopods, have a multi-chambered shell. In the process of growth, this mollusk builds for itself the most spacious and comfortable chambers of its “house” and tries to “settle” in the largest of them - that is, in the very last one.

By filling the remaining chambers with air or water, it can easily float up or sink to the very bottom. From the shell, these pearl ships are able to make “decorations” - the so-called buttons.

Nautilus

Octopuses

Class cephalopods includes marine animals with eight limbs. One of the most remarkable traits of common octopuses is the selfless care they take for their young. Female octopuses take great care of their offspring, vigilantly guarding the laid eggs.

Octopus

Cuttlefish

These animals literally “left their mark” on modern human culture. Since long time, almost all people wrote with its ink. The well-known “bone” (remnant of the head shell) of cuttlefish is no less valuable - it is collected on the sea coast.

It is used as a drawing eraser and, when crushed, as a tooth powder additive and as a medicine.

Cuttlefish

Squid

Interestingly, squids can not only swim well, but also fly. True, not many people know that they are capable of flying. It is important to note that these representatives class cephalopods They fly out of the water to independently overtake prey or to escape from numerous enemies.

The length of such flying squids is quite small - approximately 20 centimeters. Deep-sea squids also amaze with their very complex structure, as well as the size of their own eyes. In some animals of this class they can reach 40 centimeters in diameter. In general, squids pose plenty of mysteries for modern scientists.

Squid

For centuries, legends about giant colossal squids living in the depths of the sea have not been forgotten. And it should be noted that these legends are not without foundation, since the largest and largest mollusks are giant squids, which belong to the class Architeuthis and can sometimes grow up to 25 meters in length, and they weigh about 2.5 tons.

These are the amazing creatures related to class cephalopods , live in the World Ocean. Surely they will present many more surprises to scientists who have been studying them for many decades.

Giant squid

And more about these amazing creatures which are called cephalopods , you will be introduced to these videos:

A new topic in this section is an article by K.N. Nesis

"How long can you sit on eggs?"

A chicken sits on eggs for 21 days. Great spotted woodpecker - only 10 days. Small passerine birds They usually incubate for two weeks, and large predators for up to one and a half months. An ostrich (an ostrich, not a female ostrich) hatches its giant eggs for six weeks. A female emperor penguin “stands” in the midst of the polar night with a single egg, weighing half a kilo, for nine weeks. The record holder from the Guinness Book is the wandering albatross: he sits on the nest for 75-82 days. In general, eggs are small or large, in the tropics or in the Arctic, and all are laid in three months. But this is in birds.

Don't you want a year? How about two? A female sand octopus (Octopus conispadiceus) that lives in Primorye and northern Japan has been sitting on its eggs for more than a year (1). The Arctic octopus (Bathypolypus arcticus), common in our northern seas, incubates eggs for 12-14 months. It's actually incubating! It should be noted that only in very few birds does the female sit on the eggs constantly, and the male feeds her; in most cases, the hen runs away or flies away from time to time to feed a little. That's not what an octopus is like! She doesn't leave the eggs for a minute. In octopuses, the eggs are oval and with a long stalk; different species vary greatly in size: from 0.6-0.8 mm in length - in pelagic Argonaut octopuses to 34-37 mm - in some Sea of ​​Okhotsk, Antarctic and deep-sea bottom octopuses. Pelagic octopuses carry eggs on own hands, but the bottom ones are simpler in this regard - they have a burrow house. The female weaves small eggs with the tips of her hands into a long cluster with stems and with a drop of special glue, which hardens tightly in water, glues each cluster (and there are more than one hundred of them) to the ceiling of her home; in species with large eggs, the female glues each one one by one.

And now the octopus sits in the nest and incubates the eggs. Well, of course, he doesn’t warm them with his body - octopuses are cold-blooded, but he constantly goes through them, cleans them (otherwise they become moldy), washes them with fresh water from the funnel (the jet nozzle under the head) and drives away all sorts of small predators. And all this time he eats nothing. And she can’t eat anything - wise nature decided not to tempt the starving female with the proximity of such fatty, nutritious and, probably, tasty eggs: shortly before laying them, all incubating octopuses completely stop producing digestive enzymes, and therefore nutrition. Most likely, your appetite disappears completely! Before breeding, the female accumulates a reserve nutrients in the liver (like a bird before migrating) and consumes it during incubation. By the end she is exhausted to the limit!

But before she dies, she has one more important task to do: help her octopuses hatch! If you take the eggs from the female and incubate them in an aquarium, they develop normally, except that there is a little more waste (some of the eggs will die from mold), but the process of eggs hatching from the clutch is greatly extended: from the birth of the first octopus to the last it can take two weeks , and two months. With a female, everyone is born on the same night! She is giving them some kind of signal. And before hatching, octopuses see perfectly and move quickly in their transparent cell - the egg shell. The octopuses hatched (pelagic larvae - from small eggs, bottom crawling juveniles - from large eggs), spread out and spread out - and the mother dies. Often - the next day, rarely - within a week. She held on with her last strength, poor thing, just to send her children into a big life.

How long does she have the strength to last? Octopuses have been kept in aquariums for a long time, and there are many observations of their reproduction, but in the vast majority of cases they were made on inhabitants of the tropics and temperate waters. Firstly, heating water in aquariums to tropical temperatures is technically easier than cooling it to polar temperatures, and secondly, catching a deep-sea or polar octopus alive and delivering it to the laboratory is also not easy. It has been established that the duration of incubation of octopus eggs ranges from three to five days for tropical argonauts with the smallest eggs and up to five to six months for octopuses of temperate waters with large eggs. And, as I already said, two species have more than a year!

The duration of incubation depends on only two factors: egg size and temperature. Of course, there are specific features, but they are small. This means that the incubation period can also be calculated for those species that have not yet been possible to grow in an aquarium, and it is unlikely that they will be able to grow it soon.

This is especially interesting for our country. Only one or two species of benthic octopuses from Sea of ​​Japan(near the southern part of Primorsky Krai) eggs are small and develop at the stage of planktonic larvae. The giant North Pacific octopus (Octopus dofleini) has medium-sized eggs and is also a planktonic larva. And all the rest have large and very large eggs, direct development (from the eggs young hatch similar to adults), and they live at low or very low temperatures. The sand octopus has large eggs, 1.5-2 cm, but far from being record-breaking. In the northeast of Hokkaido (where by Japanese standards it’s almost the Arctic, but by ours it’s quite a cozy place, you can even swim in the summer) an egg-laying female lived in an aquarium for almost a year, although she was caught with already developing eggs, and if with freshly laid ones - I could probably do one and a half. Arctic Bathypolypus - a resident of the Arctic - was kept in an aquarium in Eastern Canada, where it is not very cold. This means that in our waters and for our octopuses, a year is not the limit! Let's try to calculate, but how much?

Z. von Boletsky tried to calculate the duration of incubation of cephalopods in cold waters (3). He extrapolated to the side low temperatures graph of incubation time versus temperature for inhabitants of temperate waters. Alas, nothing came of it: already at +2°C the line for the octopus went to infinity, and for squids and cuttlefish with eggs of much smaller octopuses it rested in the region of one to three years. But in the Arctic and Antarctic, octopuses successfully hatch their offspring even at subzero temperatures. They haven't been doing this for decades!

V.V. Laptikhovsky from the Atlantic Research Institute of Fisheries and Oceanography in Kaliningrad put together all the available information on the duration of embryonic development cephalopods and developed a mathematical model relating incubation duration to egg size and water temperature. We know the size of the eggs for almost all octopuses in our waters, the temperature of their habitat as well, and Volodya Laptikhovsky explained to me some of the “pitfalls” of his formulas. This is what happened.

The sand octopus in the South Kuril shallow waters, at a depth of about 50 m, incubates its eggs, according to calculations, for more than 20 months, and the giant North Pacific octopus on the edge of the Bering Sea shelf - a little less than 20 months! This coincides with the data of Japanese scientists: the giant octopus, which incubates eggs off the western coast of Canada for six months, would do this for a year and a half on the coast of the Aleutian Islands, and the sand octopus off Hokkaido, at a depth of 50-70 m, would do this for one and a half to two years. The Arctic bathypolypus in the Barents Sea incubates eggs, according to estimates, for two years and a week, and the fishing benthoctopus (Benthoctopus piscatorum - so called by the American zoologist A.E. Veril in gratitude to the fishermen who brought him this deep-sea inhabitant) on the slope of the Polar Basin - 980 days , almost three years. Graneledone boreopacifica at a kilometer depth in the Sea of ​​Okhotsk - two years and two months, tubercular bathypolypus sponsalis and various species of benthoctopus in the Bering and Okhotsk seas - from 22 to 34 s extra months. In general, from one and a half to almost three years! Of course, this is an estimate, because the size of the eggs varies within certain limits, and the temperature of the bottom water is different at different depths, and Laptikhovsky’s formula may not work well at very low temperatures, but the order of magnitude is clear!

It has long been suggested that polar and deep-sea animals have some kind of metabolic adaptations to low temperatures, so that the rate of metabolic processes in their eggs is higher than in the eggs of animals from temperate latitudes, if they were placed in water with a temperature close to zero. However, numerous experiments (though not with octopuses, but it is unlikely that octopuses have a different physiology than crustaceans and echinoderms) have not revealed any metabolic adaptation to cold.

But maybe deep-sea octopuses do not sit on their eggs as inseparably as shallow-water octopuses, but crawl around and feed? Nothing of the kind! Both me and my colleagues have more than once come across female tuberculate bathypolypus in trawls with eggs neatly glued to dead deep-sea glass sponges (very reliable protection: glass sponge as “edible” as a glass glass). Imagine the horror of a small, palm-sized octopus when, with a grinding sound, surrounded by frightened fish, a monster of incredible size approaches it - a fishing bottom trawl. But the female doesn’t throw eggs! And female Arctic Bathypolypus in a Canadian aquarium honestly sat on their eggs in constant care for them for a whole year until the young hatched.

True, neither I nor my colleagues have ever seen female benthoctopus and graneledon with eggs in trawl catches. But we have repeatedly come across large females of these octopuses with a flabby, rag-like body and a completely empty ovary. Most likely, these were brooding (scavenging, i.e., scavenging eggs) females, frightened off their eggs by the approaching trawl. But we have never seen the eggs they swept. They probably hide them well.

It is believed that, apart from octopuses, no other cephalopods guard laid eggs (they don’t even bury them in the ground, like crocodiles and turtles). How long does it take for their eggs to develop?

So far we have talked about finless, or ordinary, octopuses, but there are also finned ones. These are deep-sea, very strange-looking octopuses - gelatinous, like a jellyfish, and with a pair of large, spaniel-like ears, fins on the sides of the body. Cirroteuthis muelleri lives in the depths of the Norwegian, Greenland Seas and the entire Central Polar Basin, right up to the Pole - on the bottom, above the bottom and in the water column. At rest, it looks like an open umbrella (when viewed from above), and when fleeing from danger, with folded hands, it looks like a bell flower (when viewed from the side). Two species of opisthoteuthis are inhabitants of the Bering, Okhotsk seas and the northern part of the Pacific Ocean. These octopuses at rest, lying on the bottom, look like a thick, fluffy pancake with “ears” on the top of the head, and when swimming and hovering above the bottom, they look like a wide tea cup. All of them have large eggs, 9-11 mm long. The female lays them one at a time directly to the bottom and does not care about them anymore, and there is no need: they are protected by a dense chitinous shell, similar to a shell, and so strong that they can even withstand being in the stomachs of deep-sea fish. The duration of development of these eggs, according to calculations, is no less than that of ordinary octopuses guarding the clutch: 20-23 months at the bottom of the Bering and Okhotsk seas, 31-32 months in the depths of the Polar Basin!

The largest eggs of all cephalopods are those of the nautilus (Nautilus pompilius). The same one whose name was taken by a once unknown, but now famous rock band. It is unlikely that the guys have ever seen a living nautilus: it is not our fauna, it lives in the tropics of the eastern Indian and western Pacific oceans, on the slopes of coral reefs. And they certainly didn’t know that he was the cephalopod world record holder for egg size. In the nautilus they reach 37-39 mm in length and are surrounded by a very durable leathery shell. The female lays them on the bottom one by one with long (two weeks) breaks. Typically, nautiluses live at depths of 100-500 m at a temperature of 10-15°C, but to lay eggs the female rises to the shallowest water, where the temperature is 27-28°. Yes, he hides them so cleverly that, no matter how much research has been carried out on the reefs, no one has yet found nautilus eggs in nature. We saw only freshly hatched juveniles slightly larger than the current five-ruble fish. But in aquariums, nautiluses live well and lay eggs, but they do not develop. Only recently, after many failures, in aquariums in Hawaii and Japan it was possible to select the required temperature conditions and obtain normally hatched fry. The incubation period turned out to be 11-14 months. And this is with almost tropical temperature!

Cuttlefish also lay eggs on the bottom and either camouflage them by painting them black with their own ink, or tie them with a stem to stinging lobed soft corals (so that the egg sits on a coral branch, like a ring on a finger), or glue them to the bottom, hide under empty shells shellfish And our ordinary northern cuttlefish from the genus Rossia (Rossia - not in honor of our country, but after the English navigator of the early last century, John Ross, who first caught the northern cuttlefish Rossia palpebrosa in the Canadian Arctic) stuff eggs covered with durable calcareous shells into soft flint-horned sponges. According to calculations, the duration of incubation of eggs in the Pacific (R. pasifica) and northern russians(R. palpebrosa, R. moelleri) at a temperature of 0-2°C for about four months. However, in the aquarium of the American city of Seattle, the eggs of the Pacific Russia developed for five to eight months at a temperature of 10 ° C, so in reality the duration of their incubation in our northern and Far Eastern seas can be significantly more than six months.

Now - about squids. The gelatinous egg capsules of coastal loliginid squids, attached by a short stalk to the bottom and resembling either bean pods or white sausages, are familiar to all viewers of “The Underwater Odyssey of Team Cousteau.” But the egg clutches of squid - inhabitants of the outer shelf and the open ocean - are very few people know. Clutches of the most important commercial species - the Pacific Todarodes pacificus and the Atlantic Illex illecebrosus - were observed in aquariums. These are hefty, a meter in diameter, balls of transparent mucus, in which up to hundreds of thousands of eggs are suspended. The clutches are 99.99% water and float like huge soap bubbles. And also in the aquarium we saw how a small firefly squid (Watasenia scintillans), which is found in the Sea of ​​Japan and the Southern Kuriles, lays eggs: two threads of transparent mucus with a chain of eggs in it crawl out of the mantle cavity of the female through two slits on the sides of the neck and rise up . In a huge, one and a half meter, thick diamond squid, the clutch looks like a gelatinous stocking 1.5-2 meters long and 20-30 cm in diameter; on the outside of such a stocking, a gelatinous cord with eggs is wound in two threads. In general, in all known oceanic squids, the clutch is a jelly with small, usually 1-2 mm, eggs that develop quite quickly: in the tropics and temperate regions. warm waters- 5-10 days, rarely - up to two weeks. Deep-sea squid have larger eggs, 3-6 mm, and they take longer to develop. But squids are still far from being octopuses!

But the oviposition of deep-sea squids is unknown. I have been working with gonatid squids for many years. They absolutely dominate in numbers and biomass in the squid world of the Okhotsk, Bering Seas and Kuril ocean waters. These include the Commander squid (Berryteuthis magister) - an important Far Eastern commercial species, and the Arctic gonatus (Gonatus fabricii) - the only squid species that permanently lives in the Arctic Ocean

Cephalopods mentioned in the text: 1 - northern Russia, 2 - Pacific Russia, 3 - nautilus, 4 - Japanese firefly squid, 5 - Californian gonatus, 6 - northern gonatus, 7 - Japanese gonatopsis, 8 - arctic cirrhoteitis, 9 - opisthoteitis, 10-11 - giant North Pacific octopus, 12 - sand octopus, 13 - benthoctopus, 14 - graneledone, 15 - arctic bathypolypus

Until recently, no one in the world could answer the question: where and how do gonatids reproduce? Several years ago, Japanese scuba divers twice saw in the Sea of ​​Okhotsk, off the coast of Hokkaido, near the surface of the water, two large (meter-long) female gonatid squids that were already dying. One of them held in her hands a gelatinous grayish clutch of eggs. The famous professor Takashi Okutani, who was given slides with their image, suggested that the squids guard the clutch. Caring for the offspring of squids was a sensation! I was skeptical about this. I recognized the squid immediately: the Japanese gonatopsis (Gonatopsis japonicus), the largest gonatid squid. But these squids are found near the surface only in their youth, before the onset of puberty, and then they descend to great depths (I caught sexually mature squids even at a depth of 2000 m). When mature, females undergo a gelatinous degeneration and become gelatinous. At the surface, any seabird could easily peck them!

Most deep-sea squid are neutrally buoyant - “floating,” as divers say. The negative buoyancy of the muscles (this is protein, it is heavier than water) is balanced by the positive buoyancy of the large and fatty (especially in gonatid squids) liver - the main storage of reserve nutrients (everyone knows that fat is lighter than water). At the final stages of egg maturation, most deep-sea squid stop feeding, and for the rest of their lives they survive on these reserves. According to the calculations of the intelligent young marine biologist B. Seibel from the famous (in our country much more than in America) city of Santa Barbara, the gonatids have enough of them for nine months of hunger strike. As the eggs mature, reserves from the liver are transferred to the eggs and genitals. This does not affect buoyancy: eggs are also slightly heavier than water. But the eggs have been laid out, and the fat reserves have not all been used up - after all, muscle proteins are consumed first. The balance is immediately disrupted: the positive buoyancy of the fat residues in the liver, no longer compensated by the weight of the eggs, pulls the female towards the surface. There she dies for joy seabirds who adore squid, even if it’s quite watery. I assumed that the squid, as it surfaces, continues to sweep out the remains of the eggs, and on the surface it no longer has the strength to let go of the last clutch.

Quite recently, large deep-sea trawls finally caught female gonatids. The Norwegian scientist H. Bjorke from Bergen caught females of the Arctic gonatus without oviposition in the Norwegian Sea at a kilometer depth, and B. Seibel caught females of the California gonatus (G. californiensis) at a depth of one and a half kilometers off Southern California - and together with oviposition! The clutch is gelatinous, brown or black in color, looks like a honeycomb, and there is one egg in each cell. Seibel showed me these female squids. Not even jelly, but some kind of boiled jellyfish. Dark snot drips from my hand. “Well, how can such a female protect the clutch? - I asked. - Protects! - Seibel answered with conviction. - Otherwise, what is she doing next to the masonry? There are already ready-made larvae there!”

Then I couldn’t think of anything to object to. And only in Moscow it dawned on me: what if the main reserves of fat in the liver are consumed even before spawning, during the period of ripening of eggs? After all, then after spawning, only a film of skin, a pinch of collagen and a drop of fat will remain from the female, and everything else is water in the form of a squid! And the masonry is 99.9% water. This means that the specific gravity of the squid and the clutch is the same and is equal to the specific gravity of the water at the place where the eggs were laid. Neither float nor sink! The female and her clutch are doomed to hang in the water, only slowly moving at the will of deep currents. I calculated: the duration of incubation of arctic gonatus eggs in the Norwegian Sea is approximately 16 weeks, California gonatus eggs off Southern California are 14-15, and commander squid in the Bering Sea are about 12 weeks.

A terrible picture presented itself to me: a black gelatinous mass with developing eggs was hanging motionless in black icy water for months, and a blackened female, either still alive or no longer, was hanging motionless next to it. If it is capable of protecting a clutch from an impressionable person, then certainly not from a toothy deep-sea fish devoid of sentimentality.

And then it also became clear to me why many squids (and not only gonatids) dive to great depths to spawn. Bacteria! In warm waters at shallow depths, bacteria are dissolved and eaten! - mucus oviposition for several days, so that the eggs ready for hatching fall out, and the larva hatches in free water. And this is happiness: how could a tiny newborn squid get through the viscous mucus? Jet-like, like an adult squid, not possible: no free water to throw it out of the funnel. You can't hit them with fins. Push off with your hands - the mucus will not offer resistance. To crawl a half-meter distance, working, like a ciliate, with epithelial cilia, means spending so much energy that the reserves remaining from life in the egg are not enough to catch up and catch the first prey! In the cold depths, not only are there far fewer voracious enemies than at the surface, but bacteria are also inactive. You can take a piece of sausage, put it in a net so that the fish don’t eat it and the crustaceans don’t pluck it, immerse it in great depth and let it sit for a year or two. Then lift it up and you can eat. It will be preserved better than in any refrigerator!

So the mucus of the egg-laying squid, perhaps, remains until the end of incubation, three to four months. It's the mucus, not the ghost of the female, that guards the clutch! Deep-sea fish are not large enough to swallow the egg-laying whole, but tearing it apart and gnawing off a piece - try it, fight the jelly! The gelatinous oviposition of the diamond squid is so tear-resistant that when trying to catch it from the sea, the handle of a net broke, but the mucus remained intact! And the honeycomb structure of the gonatus clutch makes it easier for the squids to escape into the wild.

Understanding the fact that all cold-water (deep-sea and polar) cephalopods and even the tropical nautilus spend a significant part of their lives (months, perhaps years) in egg shells, and incubating female octopuses - next to the clutch, changes our ideas about the biology of these animals and their role in the overall economy of the World Ocean. Experience in studying warm-water and shallow-water cephalopods has led to the conclusion that their life motto is: live fast and die young! The lifespan of the vast majority of small cephalopods in the tropics and moderately warm waters is six months, medium-sized ones, including the main commercial species of squid and octopus, are a year, and large ones are a year or two. With very rare exceptions (nautilus, argonaut, possibly finned octopuses), they all die after the first and only spawning. Octopuses and squids grow much faster than fish. The use of eaten food for growth is as effective in them as in piglets and broiler chickens. The ratio of production to biomass - the most important production and biological indicator - is much higher than that of fish. As a result, for example, in the Sea of ​​Okhotsk, squid, while inferior to fish in biomass by more than an order of magnitude, are only one and a half to two times behind in production (i.e., harvest). But all this applies to the period from birth to spawning. And if you include in life cycle embryonic development and the time from the laying of eggs to the death of the female, the speed of development will be much less, and the ratio of production to biomass and, consequently, the role in the cycle of matter and energy in the ocean will be much lower.

But on the other hand, deep-sea squids and brooding octopuses stop feeding even before laying eggs and do not enter into sexual intercourse until death. food chains ocean. Hard egg shells, unbiteable mucus, protection of the clutch - all this so that their unhatched little ones do not get caught in the food chain. For the biological economy of the ocean, this does not matter, you just need to know: squid and octopuses eat so much food in their youth and grow so quickly not only in order to quickly mature, reproduce and die, but also in order to preserve their offspring.

An octopus sits on eggs. A year (years?) protects, cleanses, washes, sorts them out and, exhausted from hunger, waits, waits, waits. Finally ready! The signal for hatching - and the beloved babies blurred and crawled away (she doesn’t have the strength to look at them!), Now she can die... The squid, like a black ghost (if you hold it in your hands, it will leak through your fingers), hangs for many months near the same black gelatinous masonry. No, this does not look like the instantaneous outburst of passion of a mayfly. But how many invertebrate animals do you, dear reader, know that know what old age is?

In some dinosaurs, only the males seemed to incubate the eggs. Skeletons of representatives of three types of dinosaurs were found directly on their clutches. All three species are the closest relatives of the ancestors of birds. The bone structure of the brood dinosaurs suggests that they were males. It is possible that modern ostriches and other ratites inherited paternal care directly from dinosaurs.

Unlike most other land vertebrates, in birds, care for the offspring is usually divided equally between the father and mother. Males are involved in incubating and feeding chicks in 90% of bird species. For comparison, among mammals, paternal care for offspring occurs in only 5% of species, and among modern reptiles- and even less often.

The class of birds includes two subclasses: ratites (Paleognathae), which includes ostriches, cassowaries, rheas, kiwis and their relatives, and new palates (Neognathae). The second subclass includes the vast majority of modern birds. In neopalates, both parents usually take care of the offspring (sometimes only the mother), while in ratites it is almost always only the father. Which of these options was the original for birds?

The behavior of the closest modern relatives of birds - crocodiles - seems to indicate the primacy of maternal care. In crocodiles, females take care of their offspring. However, the separation of the evolutionary lines of crocodiles and the ancestors of birds occurred a very long time ago, back in the Triassic period, long before the appearance of birds as such. Therefore, to understand the origin of parental care in birds, it was very important to obtain at least some information about the behavior of their immediate ancestors, which, according to the currently prevailing ideas, were lizard-hipped dinosaurs from the group Maniraptora.

Representatives of three species of maniraptor dinosaurs ( , Oviraptor philoceratops , Citipati osmolskae) were found directly on their clutches, in some cases - in poses characteristic of birds hatching eggs. In an article published in the latest issue of the magazine Science, American paleontologists claim that these “hens” were most likely males.

This is evidenced by two facts: the structure of the bones of brood dinosaurs and the ratio of clutch volume to the size of an adult animal.

Researchers studied the ratio of clutch volume to body mass in archosaurs with different types of care for offspring (archosaurs are a group that includes crocodiles, birds, dinosaurs and a number of other extinct reptiles). It turned out that the largest clutches are typical for birds in which only the male incubates the eggs. For crocodiles, with their maternal care for their offspring, and for birds, in which the mother takes care of the chicks together with the father or alone, clutches of a smaller volume are typical. Apparently, this is explained by the fact that egg laying in archosaurs is associated with a very large expenditure of resources. If the clutch is large in volume, the mother may not have enough strength to care for it. It is much easier to do this for the father, who does not waste his body’s resources on laying eggs and can devote himself entirely to caring for the offspring. Moreover, in this case it becomes possible option“communal clutches”: a male takes care of his offspring from several different females.

It turned out that the masonry Troodon, Oviraptor And Citipati in scope they correspond to the model of paternal care for offspring (see figure). Other dinosaurs, less closely related to the ancestors of birds, had significantly smaller relative clutch sizes.

The second argument is that no evidence was found in the bones of mother-hen dinosaurs that these animals were laying eggs shortly before their death. Female archosaurs use a lot of calcium phosphate to form the strong shells of their eggs, with much of the calcium and phosphorus taken directly from the female's bones. In female crocodiles, this leads to the formation of characteristic small cavities in the bones of the limbs. In most birds, before laying eggs, a special tissue is formed in the medullary cavity of long bones - the so-called medullary bone, which serves as a source of calcium for the development of eggs. It gradually dissolves as eggs are laid, but usually some remnants of it remain afterward. Medullary bone has been found in some dinosaurs ( Tyrannosaurus, Allosaurus, Tenontosaurus). However, maniraptor brood dinosaurs have neither medullary bone nor the "crocodilian" signs of partial bone dissolution.

Paleontologists very rarely manage to find out anything about the behavior of extinct animals, and in most cases, conclusions of this kind are made on the basis of fragmentary, indirect and, frankly, controversial data. Against this background, the conclusion of American paleontologists about paternal care for offspring in maniraptor dinosaurs looks quite well founded.

If among maniraptor dinosaurs, considered the closest relatives of the first birds, only males really cared for their offspring, then this behavior is most likely the original behavior for birds. It turns out that ostriches and their ratite relatives inherited paternal care for their offspring directly from their dinosaur ancestors. The participation of the mother in incubating and feeding the chicks, characteristic of neopalates, is a more recent innovation.

Cephalopods are the most highly organized of all representatives of their phylum. Class Cephalopods ( Cephalopoda) is divided into two subclasses: fourgills ( Tetrabranchia) with a single order, family and genus of Nautiluses ( Nautilus) and bibranchs ( Dibranchia) with four orders: octopuses ( Octopoda), vampires ( Vampyromorpha), cuttlefish ( Sepiida) and squid ( Teuthida).

Even the most primitive of cephalopods - nautiluses - take care of their offspring. For example, females Nautilus pompilius, which lay the largest eggs among cephalopods (up to 4 cm in length), carry out this process very responsibly. The female lays eggs on the bottom one by one with long (about two weeks) breaks. Typically, nautiluses live at depths of up to 500 m, but to lay eggs they rise to the shallowest waters, where the temperature reaches 27–28 °C. At the same time, the female hides her eggs so carefully that until now not a single researcher has seen nautilus eggs in nature. Only recently, after many failures, were these mollusks able to be propagated in aquariums. It turned out that the incubation period of their eggs is 11–14 months.

The eggs of some species of octopuses take no less time to develop. Moreover, the females of many representatives of this order “hatch” their clutch, not leaving it for a minute: they constantly sort through the eggs, clean them, and wash them with fresh water from a funnel. In some species, the female, with her sensitive tentacles, carefully weaves the stalks of small eggs into a long cluster and, with a drop of special glue, attaches it to the ceiling of an underwater cave, in which there can be more than one hundred such clusters. In species that lay large eggs, the female attaches them to the ceiling one by one.

During the entire period of egg development, females of “brooding” octopus species do not feed, accumulating a supply of nutrients in their bodies in advance. Before reproduction begins, their production of digestive enzymes completely stops.

Female sand octopus ( Bathypolypus arcticus), living in the waters of Primorye and near Northern Japan, takes care of its clutch for about a year. And the arctic octopus bathypolypus ( Bathypolypus arcticus), living in our northern seas, “hatches” eggs for 12–14 months. After the babies are born, the exhausted female dies. A similar phenomenon - death after the completion of a single reproductive cycle - is generally very typical for female cephalopods. But their males sometimes survive 2-3 breeding seasons.

Before her death, the female octopus must help the babies hatch from the eggs. In an aquarium, without a mother, the hatching process of octopuses is very protracted and up to two months pass from the birth of the first baby to the hatching of the last one in the same clutch. When the mother is alive, the cubs are born in one night. Perhaps the octopus gives them some kind of specific signal, because before hatching, small mollusks already see well and move quite actively in their transparent egg shell.

Cephalopod eggs: 1 - Eledone; 2 - Cirroctopus; 3 - Loligo; 4 - Sepia

Other representatives of bibranched cephalopods do not incubate eggs as carefully as octopuses, but show concern for their safety in other ways. For example, cuttlefish, laying their eggs on the bottom, camouflage them either with ink, or by covering the clutch with empty mollusk shells, or even by tying the eggs to the stems of stinging corals. One species of cuttlefish stuffs its eggs into soft flint-horned lips. Development of cuttlefish eggs in northern waters could probably last more than six months.

As for squid, in known oceanic species the clutch is a gelatinous formation with eggs suspended in it. In the most important commercial species Todarodes pacificus And Illex illecebrosus These are huge, 1 m in diameter, balls of transparent mucus, which contain hundreds of thousands of small eggs. And the little firefly squid ( Watasenia scintillans) these are two transparent strings of mucus that contain mollusk eggs. In warm and moderately warm waters, small squid eggs develop in 5–10, sometimes up to 15 days.

Cephalopods- the most highly organized invertebrate animals. This class includes squids, cuttlefish, octopuses and nautiluses. These animals usually have a well-separated head, and the leg is transformed into a perioral crown of limbs (arms, or legs and tentacles) and a funnel - a unique organ for the animal’s reactive movement.

Extinct ancient cephalopods had a very peculiar shell with septal partitions. The shape of the shell in ancestral forms was extremely diverse, from straight or curved to varying degrees to twisted in one or more planes. A siphon passed through all the chambers - a tube into which the dorsal outgrowth of the mantle entered, and the chambers (if they were developed) were filled with liquid and gas. Of the modern forms, phragmocone has been preserved only by the nautilus, the small deep-sea cuttlefish spirula and ordinary cuttlefish - sepia, but in the latter it is significantly reduced.

Most cephalopods, although not all, have an ink sac that forms as an outgrowth of the rectum. When an animal is irritated or in a moment of danger, ink is thrown out through the anus in the form of a kind of “smoke screen” or an elongated drop, vaguely reminiscent of the mollusk itself.

The lifespan of most cephalopods ranges from six months to two years, most often about a year. All cephalopods, without exception, are dioecious. In males of many species, one of the arms is used to transfer spermatophores to the female. Usually only part of the male’s arm is transformed, but in pelagic argonaut octopuses, the male of which is much smaller than the female (only about 5% of its length), his 3rd, counting from the dorsal side, left hand It completely develops into a hectocotylus, which is huge in relation to the size of the dwarf male, which, after being charged with sperm (the Argonaut has no spermatophores), breaks off, independently crawls along the female’s body, crawls into her mantle cavity and is stored there.

Cephalopods (except Nautilus and Argonaut) reproduce once in their lives, after which they die immediately or after some time. In some oceanic squids and cuttlefish, spawning is very extended, while in deep-sea bottom-finned octopuses, the nautilus and the argonaut, it is intermittent. Nevertheless, they should be considered monoparous animals.

No monogamous species are known among cephalopods. Almost random mating is typical for males. Females, in addition, “practice” the so-called “simultaneous polyandry”. A female Pacific bottom octopus was observed to mate with 6 males at once within 24 hours.

It is very typical for cephalopods to have chromatophores in their skin - complex sacs with colored pigment that allow the animal to change color very quickly, in a second.

A number of cephalopods have luminescent organs - photophores, which can be located both on the outer surface of the body and on internal organs.

Some cephalopods have blue blood because... Instead of hemoglobin, which contains iron, it contains hemocyanin, which contains copper.

But perhaps the most important evolutionary “acquisition” of cephalopods is the brain, which has a rudimentary cortex. In more primitive external shell forms (nautilus) the central nervous system consists of scattered ganglia lying on a cartilaginous plate, and there are 13 lobes in the brain. In highly developed intrashell forms (squids, cuttlefish, octopuses), the central nervous system is highly integrated. Their brain is well isolated, completely enclosed in a cartilaginous shell and has 2-3 times more lobes than that of the nautilus. The brain has association zones, like the vertebrate cerebral cortex, as a result of which higher cephalopods are capable of learning.

Cephalopods are also distinguished by well-developed organs of vision, which in terms of complexity of structure and functions are sometimes not inferior to the eyes of higher vertebrates, including humans. In the giant squid Architeuthis, the diameter of the eyeball can reach 40 cm (and possibly more)! More than half of the brain's nervous tissue is located in the optic lobes.

The extreme size of cephalopods is astonishing: the miniature cuttlefish Idiosepius is only about 10 mm long, while Architeuthis can be up to 18 m in total length (and possibly more) and weigh up to a ton - the largest of modern invertebrates

Until the end of the Cambrian, there were few cephalopods, but in the Ordovician the group began a “golden age”, and they spread throughout the world. Despite the fact that the ancestor of cephalopods was no more than 2 cm in size, already in the Middle Ordovician real giant endocerids appeared with a shell length of more than 10 m! Among the ammonites, already at the end of their history in Cretaceous period, there were also giants with a curled shell diameter of 3.5 m (the size of an elephant)! The weight of such monsters was apparently several tons.

The history of the class of cephalopods has lasted for more than 500 million years, during which numerous ups and downs in the diversity of species and life forms. The entire history of the group was built, so to speak, on attempts to find a morpho-ecological solution to the problem of adaptation to pelagic existence. To maintain buoyancy, ancient cephalopods “chose” two main methods. One way is to preserve the outer shell and achieve hydrostatic equilibrium by changing the pressure in the chambers of the phragmocone. Another method is the reduction of the shell, up to its complete loss, and an active lifestyle while maintaining negative buoyancy. Some modern forms have developed a third way - achieving neutral buoyancy after complete loss of the shell due to watering the tissues and compensating for the weight of “heavy” parts of the body with “floats” filled with light (lighter than water) liquid.

The first path turned out to be an evolutionary dead end for most groups, and of the huge number of species with an external shell, only nautiloids survived - forms with the most simply constructed shell. Thus, there are approximately 20 times more extinct species of cephalopods than modern ones.

The second path turned out to be more successful and led to the emergence of modern forms, in which the shell was overgrown with a mantle on all sides and turned into an internal axial skeleton (an analogue of the notochord and spine) or disappeared altogether. During the evolution of the class, the ecological structure of life forms changed, and in different eras there was different ratio planktonic, nektonic, benthic and benthopelagic species.

Modern cephalopods are represented by two large taxonomic groups (subclasses): nautiloids (there is an external shell; 2 genera and several species of a single family of nautilids) and coleoids (the shell is hidden under the mantle, partially or completely reduced; about 700 species, 140 genera, 45 families, 4 squads).

Nautilus- The animal is remarkable in many ways. Firstly, this is a real “living fossil”, which, like the lobe-finned fish Coelacanth, has been preserved, practically unchanged, for tens of millions of years. Secondly, it retained a number of primitive structural features and way of life. And finally, and this is perhaps the most important thing, it was precisely thanks to the presence of a true phragmocone that the nautilus turned out to be a kind of “connecting link” between modern internal-shelled cephalopods and many extinct external-shelled animals, such as ammonites.

To subclass coleoid include the orders of squids, cuttlefish and octopuses. Squids and cuttlefish are sometimes combined into the superorder decapods - they all have 4 pairs of arms and, as a rule, 1 pair of hunting tentacles between the 3rd and 4th pairs of arms. In addition to those listed, there is also a fourth detachment, with a single representative whose name, translated from Latin, sounds ominous: “hellish vampire squid.” In fact, it is a small, up to 40 cm, quite peaceful pelagic deep-sea fish (usually lives at depths of more than 3 km) relict species, combining the characteristics of finned octopuses and decapods.

To the squad cuttlefish include two large groups of cephalopods: the cuttlefish proper, or sepiids, and the so-called bobtails (from the English bobtail squid - short-tailed squid), or sepiolids. In addition, the order of cuttlefish includes the amazing cephalopod Spirula as an independent suborder. This small mollusk, no more than 5 cm long, differs from all others in that its shell is divided into chambers by partitions - a real phragmocone of ancient cephalopods! Only, unlike the nautilus and ammonites, this shell is not external, but hidden in the thickness of the mantle and twisted not on the dorsal, but on the ventral side

Spirula lives in the tropics, and is absent from our waters. In the south of Primorye there is one species of true cuttlefish, the Japanese cuttlefish, and two species of sepiolids: Pacific Russia and two-horned sepiola. The fins of the cuttlefish border the mantle with a narrow ribbon; eyes of the so-called myopside type (the anterior chamber of the eye communicates with environment only through a small hole in the cornea). The cuttlefish lives at the bottom in coastal zone and can cleverly camouflage itself with the color of the soil, lying in wait for prey - fish and crustaceans.

Unlike true cuttlefish, which live mainly on the shelf and only occasionally descend to depths of more than 200 m, sepiolids sometimes found deeper than 1 km. Sepiolids are quite small animals: the greatest length of the mantle of Pacific Russia, the largest of the sepiolids, reaches 10 cm with a weight of 250 g, but is usually much less. For comparison: the largest true cuttlefish from the tropics southeast asia reaches a length of 50 cm and a weight of 12 kg! Genetic studies have also shown that sepiolids are a well-distinct group. Apparently, they can be considered an independent order of the class of cephalopods.

True cuttlefish are characterized by complex mating behavior. Competition between males for the right to pass on their genes to the next generation can be quite original. So, often before mating, a male literally scratches out with the tips of his hands and blows out the sperm of another male who has preceded him using a funnel from the female’s seminal receptacle, and only then begins to mate! Large cuttlefish have special “lekking chambers” where the male demonstrates his masculine beauty and power to the female. The eggs of cuttlefish and sepiolids are large, usually up to 1 cm, less often up to 2 cm in diameter; in sepiolids they are covered with a hard calcareous shell and are laid in groups on underwater objects. Embryonic development in heat-loving species is short, 1-2 months, while in cold-water Pacific Russia the incubation duration can reach up to 9 months. Cuttlefish have no care for their offspring, and the animals die a short time after spawning.

Squid- the most numerous order of cephalopods. In squids, the calcareous part of the shell is completely reduced, and all that remains of the shell is a chitinous translucent plate, or gladius. Just under 30 families of squid are grouped into two suborders: myopsids (2 families in total and about 50 species) and egopsids (23-25 ​​families and more than 200 species).

Squids, like cuttlefish, with rare exceptions, do not care for their offspring.

Another thing - octopuses. For many representatives of this order, caring for offspring occupies a considerable part of their lives and sometimes takes bizarre forms. The females of some octopuses that live on the sandy bottom carry clutches with them in their arms. Thus, the female of one small Atlantic tropical coastal species was met with a huge clutch of 36 thousand eggs, which weighed almost half the body weight of the octopus itself! The Argonaut female lays fertilized eggs in a thin calcareous shell, in which she lives and which she forms with the secretions of the first pair of hands. Some pelagic octopuses have become truly viviparous: their eggs, after fertilization, remain in long curved oviducts, embryonic development occurs as the eggs move along the oviducts, and young octopuses emerge. All this variety of parental care has evolved and is characteristic of ordinary octopuses.

In general, the order of octopuses is divided into two well-separated suborders: the finned and ordinary octopuses. The first suborder includes deep-sea octopuses with a gelatinous body, two fins on the sides of the body and two rows of antennae along the inner surface of each arm on each side of a single row of suckers. They live at depths usually greater than 500 m.

The suborder of common octopuses is much more diverse and rich in species. They do not have fins, barbels on their arms, or the cartilaginous vestige of a shell. Although there are many pelagic species among these octopuses, most live on the bottom. Bottom-dwelling species can swim or move along the bottom using their arms, literally walking. True octopuses have almost completely lost their shells. That is why they are extremely plastic and can literally seep through narrow cracks in rocks. All octopuses, unlike decapods, do not have chitinous rings in their suckers and, therefore, do not have hooks. There are up to 200 species of true octopuses, about half of them belong to the same genus Octopus. The combination of so many species into one genus is artificial, does not reflect family ties and is caused only by the great morphological similarity of these octopuses. The artificiality of the Octopus genus has been convincingly proven by molecular genetic studies.

The Far Eastern seas of Russia are home to the giant octopus, the largest of all KNOWN octopus species. Individual specimens of this species grow up to 5 m (according to some sources, even up to 10 m!) in length and weigh up to 60, presumably even up to 180 kg or more! Mature males on the Primorye shelf giant octopus weigh 8-25 kg or more, usually 10-15 kg; The average weight of mature females is 11-21 kg. Giant octopuses grow very quickly, gaining up to 2% of their body weight daily, and live, according to various estimates, 3-5 years. There are three known subspecies of the giant octopus. The smallest lives in the Bering Sea and the Kuril Islands, where mature individuals usually have no more than 1 m in length and weigh up to 4 kg. In Primorye and off the west coast North America There are larger subspecies that are genetically practically indistinguishable, but differ well from the Bering Sea. The giant octopus is a very intelligent and beautiful animal and is often kept in aquariums. This is a completely peaceful creature, although there are reliably known facts of unprovoked attacks by an octopus on people at sea. Interestingly, the larger the octopus, the less aggressive it is. The exception is males during the breeding season.

Octopuses are solitary animals and spend almost all their time in shelters (juveniles in mollusk shells, adults in rock burrows and caves). Octopuses are quite skilled in hunting techniques. They can ambush actively swimming fish, collect shellfish by rummaging under stones, and can catch fish with a “cast net”, which is obtained by inflating the membrane between their hands. At the Seattle Aquarium, a large giant octopus managed to catch a 1 m long dogfish, a 0.6 m long stingray and a 1.5 kg chinook salmon using the tip of its outstretched arm as fish bait! Octopuses also eat stingray embryos, removing them from hard-shelled egg capsules using their beak and radula. With its radula, the octopus can drill through large shells of mollusks, which it cannot open with the help of suction cups.

Unlike decapods, octopuses do not have a courtship phase before mating. Mating in a giant octopus is long: the male holds the female in his arms for 2 to 4 hours. In other species, there may be no "full contact" between the sexes, and the male transfers spermatophores to the female at the tip of his hectocotylated hand. After mating, the male does not die immediately and can live for several more months. He practically does not eat, becomes very active and quickly loses weight, and by the end of his life his skin begins to “decrepit” and hang in tatters.

The female giant octopus lays up to 50 thousand small, 6-8 mm long eggs on the ceiling and walls of the underwater lair and begins to protect and carefully care for the clutch. She constantly sits in the den, blows a stream of fresh water through the eggs through a funnel, cleans them with suction cups, and removes sick and dead eggs. The duration of such “incubation” depends on the water temperature, and the hatching of young octopuses begins 5-8 months after laying the eggs, and maybe more. The female waits patiently until the last of her cubs hatches, and after some time, usually within a month, she dies. During the “incubation” of the clutch, the female loses 50-93% of her weight! Octopuses crawl out of the egg, mantle first, with remains yolk sac, which usually falls off or is resorbed within 24 hours. Newborns weigh about 20-30 mg. The juveniles actively swim and feed in the water column, and only after a few months begin to settle to the bottom. By this time, the arms and mantle of young octopuses lengthen, and the eyes move from the sides to the dorsal side. Having settled to the bottom, octopuses immediately look for shelter; usually, they first take refuge in the thickness of gravel, and later occupy empty mollusk shells, begin to move along the bottom on their hands and hunt like adults.

Large octopuses are dangerous, and the main danger is not the strong tentacles of large octopuses, but their poisonous saliva, which has a paralyzing effect on prey. Signs of the disease resemble symptoms snake bite. Off the coast of Australia and Japan live small spotted blue octopuses, whose bite can even be fatal to humans.

Of the marine invertebrate animals, the most gifted are cephalopods: squid, cuttlefish and octopuses. The development in animals of organs capable of using the simplest tools leads to the formation of a more complex brain, to the expansion of the scope of its activity, to the formation of various adaptive reflexes. Octopuses are the smartest of all invertebrates. They are trainable and have good memory, distinguish geometric shapes. They recognize people and get used to those who feed them.

Cephalopods are the only deep-sea invertebrates that have good visual memory, and they use it better than any other vertebrate. Their eyes, which have more than 70 million visual cells, surpass human eyes in visual acuity. They allow the animal to distinguish colors, and can adapt to different distances by changing focus. Moreover, cephalopods can determine the condition of the seabed by feeling it with their tentacles - this information is very important when choosing camouflage.

You can find one octopus, skillfully camouflaged to match the sand on which it lies, and a few meters away from it, a second one, taking on the colors of the rough, dark fragment of the reef on which it is located. For such an absolute adaptation of appearance to the environment, the octopus needs two sources of information: data about color that the eyes give him, and data about the texture or structure of the surface that the organs of touch provide him. When they hunt fish, they also respond to each action of the prey by changing color, becoming lighter or darker. More dark color serves as an indicator of aggression.

The cuttlefish, if it is frightened, reacts in a completely special way: it becomes pale, but remains two very dark spots on the back, apparently designed to convince the intended enemy that these are the eyes of a much larger animal buried in the sand.

Cephalopods are highly capable of learning. Laboratory tests have shown that they can use tools and learn from experience - abilities that have so far only been discovered in great apes.

A glass hollow cylinder, open at the top, was placed in an aquarium with an octopus. In the cylinder is a crab, the octopus's favorite food. The mollusk soon saw the crab, the cylinder stood one and a half meters away from it. An attack followed, but the glass delayed the octopus at the very target.

The octopus wriggled in vain attempts to grab such desired and close prey. In rage, he flared up with one or another shade of crimson. It is unknown how long he would have continued his fruitless attempts, but one tentacle inadvertently jumped over the upper edge of the cylinder and its tip penetrated into the vessel with the crab. Immediately the octopus changed tactics: apparently, the tip of the tentacle smelled the crab, and the blind man led the sighted one. The tentacle, bending over the edge of the cylinder, stretched further and further, inexorably approaching the crab, and the octopus crawled behind it, climbing up the glass. Finally, the tentacle touched the crab and the next second the octopus jumped over the glass wall and grappled with the crab.

Now the octopus knew exactly how to get the crab from behind the glass. But he did not go straight to the crab through the top, but first rushed at the crab, as before, trying to grab it through the glass, only then crawled upward with tentacles that seemed to know the way better. In other words, he exactly repeated his first attempt, which was crowned with success.

The cuttlefish was also asked to remove a shrimp from a jar without a lid. For thirty hours in a row (according to other sources, adult cuttlefish stop their fruitless attempts after an hour), the cuttlefish fought against the glass, attacking head-on, but never thought to rise up a little, as the octopus did.

A few days later the experiment was complicated. The cylinder with the crab was covered with glass. But the tentacles, having studied the road well, bypassed this obstacle without much difficulty. After several unsuccessful attempts they felt a microscopic gap between the flat roof and the side of the can. They lifted the lid and led the octopus behind them.

We took a break of seven days and then repeated the experiment again. The octopus still found the right decision tasks. Conditioned reflex, even not reinforced by an additional lesson, continued to function flawlessly. The cuttlefish, having learned to get food from behind the glass, after eighteen hours forgot how to remove a tasty morsel from the jug without breaking the walls with its forehead).

Octopuses walk on tentacles along the bottom, carry weights in them, build nests from stones, open mollusk shells, attach eggs to stones, and when the octopus sleeps, some tentacles serve as guards. In accordance with the versatile purpose, the roles are distributed between the different tentacles. The tentacles of the second pair from the top, which are usually the longest, are used by octopuses as attack weapons. When attacking prey and defending against an enemy, octopuses try to grab the enemy with these tentacles. IN peacetime fighting arms turn into legs: they serve as stilts when moving along the bottom. The uppermost pair of hands is intended for examining and feeling surrounding objects, and the two lower tentacles are on guard during sleep.

In deep sleep, all the octopus' tentacles, except the two lower ones, are pressed to the body, and the guard arms are extended to the sides. From time to time they stretch upward and slowly circle above the sleeping octopus, like a radar antenna. The octopus is in deep sleep. He doesn't see or hear anything. But as soon as you lightly shake the water or slightly touch the guard tentacles (namely these, and not others!), the animal immediately jumps up.

Cephalopods are a potential human food reserve. About 75 commercial species of cephalopods are known, 64 of which live in the coastal zone (cuttlefish, neritic loliginid squid and benthic octopuses). The annual catch of cephalopods in marine commercial catches has approached 3 million tons. The main consumers of cephalopods are Japan and the countries of Southeast Asia.

IN lately“gastronomic” human interest in cephalopods has increased sharply, since their meat is a complete protein food that can replace fish. Squid can be found in the sea in schools of thousands and are easy to catch with nets. Octopuses are caught individually - with spears or with the help of “jug traps”, which the octopuses take for shelter and willingly occupy. In Japan, Korea and China, instead of traps, ordinary clay jars are often used, only with a hole in the bottom, to drive out the caught octopus.

Besides humans, cephalopods have many enemies. Moray eels, sea ​​eels and stingrays lurk between the reefs. In the open sea, cephalopods become prey for sharks and catfish whales, and in shallow waters they are threatened by birds and seals. This strict natural selection means that only animals with high level development of behavioral stereotypes.

In some countries, paint and ink are made from the ink liquid of cephalopods.