Nautilus takes care of its offspring. How cephalopods take care of their offspring. Cephalopods: nautiluses

Today we will talk about what kind of gentle parents representatives of the class of cephalopods, the most organized representatives of this type, are.

Baby clams

One of the most important instincts in the animal world is caring for offspring; cephalopods also have this instinct. Even the most primitive representatives of the class, nautiluses, take the issue of reproduction extremely seriously.

Female Nautilus pompilius lays large eggs, about four centimeters long, one at a time. The interval between the laying of each subsequent egg can be up to two weeks. In order for the eggs to form full-fledged offspring, the female has to leave her native cool depths and float to shallow water, where the water warms up well and the temperature reaches 28 degrees Celsius.

The female N. pompilius camouflages her clutch so diligently that until now no one has seen her eggs in natural environment a habitat. And only very recently, scientists managed to reproduce nautiluses in captivity and found out that the maturation period for eggs is 44-56 weeks.

Care and concern

Many representatives of the octopus order do not leave the clutch throughout the entire incubation period. To do this, before the start of the reproductive period, the body accumulates a certain reserve nutrients. Weaving clusters of small eggs, of which there can be hundreds, the females use a special astringent to hang them from the ceiling of the cave. They constantly wash the masonry with fresh water and clean it of debris with caring tentacles. In representatives with larger eggs, the female octopus attaches them to the roof of the cave one at a time.

The female Bathypolypus arcticus, the Arctic octopus, becomes so exhausted after a year of hatching her eggs that she can only help the young mollusks hatch, and then dies from physical exhaustion. In an aquarium, the birth of young animals takes about two months, but in the presence of a female this happens in about 8 hours.

Other representatives of the cephalopod class also protect their offspring. The female cuttlefish camouflages the clutch with an ink cloud, covers it with empty shells, or attaches it to the body of a stinging coral. Other species insert their eggs into the cavity of the flinthorn sponge.

Cephalopods were not without reason dubbed the primates of the sea among invertebrate animals; the reason for this was the complexity of their behavior and progressive features of organization.

New topic in this section - 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 usually incubate for two weeks, and large predators- up to one and a half months. An ostrich (an ostrich, not an 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, 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 their own hands, but bottom-dwelling octopuses are simpler in this regard - they have a burrow. The female weaves small eggs with the tips of her hands into a long cluster with stems and with a drop of special glue that hardens firmly in water, she 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 will disappear completely! Before breeding, the female accumulates a supply of nutrients in the liver (like a bird before migrating) and uses it up 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 fisheries and Oceanography in Kaliningrad brought together all available information about the duration of embryonic development of cephalopods and developed a mathematical model linking the duration of incubation with 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.

Sand octopus in the South Kuril shallow waters, at a depth of about 50 m, it incubates 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: giant octopus, which incubates eggs off the western coast of Canada for six months, on the coast of the Aleutian Islands would do this for a year and a half, 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 (Bathypolypus sponsalis) and various species of benthoctopus in the Bering and Okhotsk seas - from 22 to more than 34 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 like this! 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: a glass sponge is 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 - inhabitants of the Bering Sea, Sea of ​​Okhotsk and the North Pacific. 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 common octopuses, protecting the masonry: 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 part of the Indian and western parts 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. Usually 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. 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 Pacific (R. pasifica) and northern Russian (R. palpebrosa, R. moelleri) eggs at a temperature of 0-2°C is 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 may 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 similar either to 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 known. 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 Kuril Islands, laying 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 moderately 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

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 they could easily be pecked by any seabird!

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 egg-laying in the Norwegian Sea at a kilometer depth, and B. Seibel caught females of the Californian gonatus (G.californiensis) at a depth of one and a half kilometers off Southern California - and together with egg-laying! 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 egg ripening? 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 equals specific gravity water in 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 for months in black icy water, and just as motionless a blackened female was hanging next to it, either still alive or no longer alive. 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? It is impossible to do it in a jet way, like an adult squid: there is no free water to jet 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 is 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: 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?

During the evolution of the animal world, a number of methods have been developed to increase the survival of offspring. One of them is the care of the parents for the young before and after birth. Some animals carry their young on their bodies, others build houses for them, and others feed their offspring.

Such parental care ensures an increased percentage of survival of the species, and for some species, the transfer of social experience. Most interesting cases Guardianship of “parents” will be discussed in this article.

Caring parents among fish

Most fish do not worry about their young: after laying their eggs in the water, the fish disperse in different directions. But in such fish, the survival of the species is ensured by a huge number of eggs. But among the fish there are caring parents. For example, Nannostomus chooses dense algae or aquatic plants, which will protect the eggs. Betta fish build a nest out of their own saliva! Usually the male does this: he fills his saliva with air and whips it into foam. In such a foam nest, the fry hatch - under the watchful supervision of the “father”, who remains with them until the cubs learn to feed on their own.

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Amazing animals

Tropheus lay very few eggs - and in order to save their offspring they are forced to carry the eggs, and then the fry, in their mouths. But the cubs are comfortable and safe! Cichlids have become adept at laying eggs in the shells of bivalve mollusks.

Caring parents - mollusks

Not everyone knows that octopuses are the smartest creatures. The size of their brain is large, and the structure of their eyes resembles the complexity of the human organ of vision. Octopuses don't worse than people take care of their young. After mating, the male octopus soon dies, and the female looks for reliable shelter in the rocks, climbs there and lays eggs.

As you know, for a successful existence biological species each generation of its representatives must leave behind offspring capable of reproduction. During the process of childbirth and the subsequent process of caring for the offspring, mainly instinctive behavior is realized. For example, immediately after the fetus emerges from the birth canal, the female mammal frees it from the membranes, gnaws the umbilical cord, eats the membranes and placenta, and actively licks the newborn. The cubs of a female who does not provide primary care for them are doomed to death in nature, and this trait itself, which is largely hereditary, is eliminated with them.

The success of offspring survival depends greatly on the adequacy of parental behavior, which is an important factor natural selection. Caring for the offspring of many animals begins with preparation for their birth. Often seasonal migrations of animals are associated with movement to breeding grounds, sometimes many thousands of kilometers from their habitat. Animals that do not make such long journeys also choose their nesting territory in advance, and many of them carefully guard it and prepare shelters - nests, burrows, dens, adapted for future offspring.

Types of care for offspring

In the animal world there are the most different shapes care for the offspring: from complete absence to the most complex and long-term relationships between children and parents.

Complete lack of care for offspring

Let us note that in its simplest form, care for the offspring is present in all organisms and is expressed in the fact that reproduction occurs only in conditions favorable for the offspring - in the presence of food, suitable temperature, etc. Subsequently, most invertebrates and fish do not take care of their offspring. Successful existence similar types ensures their mass reproduction. In the vastness of the ocean, many species of invertebrates and fish, gathering in giant schools, lay millions of eggs, which are immediately eaten by a huge variety of carnivorous creatures. The only salvation for such species is colossal fertility, which still allows the minimum number of descendants necessary for the existence of the population to survive and reach adulthood. The number of eggs in many species of fish that lay eggs in the water column is estimated in hundreds and millions. So, the female living in northern seas large sea pike - the moth - spawns up to 60 million eggs in one season, and the giant sea ​​sunfish, reaching a weight of one and a half tons, throws up to 300 million eggs into the ocean waters. Left to chance, fertilized eggs mix with plankton or sink to the bottom and die in countless quantities. The same fate befalls the larvae that hatch from the eggs, but there are still enough survivors to maintain the population of the species.

Carrying eggs laid on the body of one of the parents

The females of many marine animals attach the laid eggs directly to their bodies and carry them, as well as the hatched young, until they become independent. Similar behavior is observed in many aquatic animals: starfish, shrimp and other crustaceans (Fig. 12.9). This behavior represents the next step in the complexity of caring for offspring, but in general it is not particularly inventive.

Rice. 12.9.

passive way of caring for offspring

The number of eggs laid is inversely proportional to the level of parental care. This pattern is well confirmed by sea stars, among which there are both species that lay eggs directly into the water, where they are fertilized by the sperm of several males, and species that carry eggs on their bodies. In species of the first group, the number of eggs maturing in the female’s body reaches 200 million, while in sea stars that take care of their offspring, the number of eggs laid does not exceed several hundred.

Laying eggs in an environment previously found or specially prepared by the female

Construction of nests and their protection until the birth of offspring

A more advanced type of care for offspring can be considered the construction of a nest, laying eggs or eggs there and protecting it until the growing young leave it. This behavior is typical for a number of species of fish, spiders, octopuses, some centipedes, etc. A similar level of care includes the brooding of eggs and fry in the mouths of male fish, as well as the eggs and tadpoles on the hind legs of the midwife toad. The described level is characterized by a lack of any interest on the part of parents in youngsters gaining independence.

Rice. 12.10.

Caring for offspring until they gain independence

Long-term care for offspring is observed in some species of invertebrates and fish. The care of offspring among social insects reaches great perfection.

Many examples different types parental behavior demonstrated by amphibians (Fig. 12.10). In higher vertebrates there are different ways care for the offspring, which depend primarily on the level of maturity of newborns. In the most general outline among them we can highlight the following groups parental behavior:

• – raising offspring by one female or one male;
• – raising offspring by both parents;
• – raising young in a complex family group.

Eyes of a bivalve mollusk.

Octopus.

When danger approaches, cephalopods eject a stream of black liquid into the water. The “ink” blurs in the water, and under this thick black cloud the mollusk escapes safely. Cephalopods are true underwater chameleons: they can quickly change skin color. If you make an octopus angry, it will instantly change grey colour to black, and having calmed down, it will turn gray again.

Among the most simply structured cephalopods are nautiluses, or pearl ships. Nautiluses, unlike most cephalopods, have a multi-chambered shell. Growing up, the mollusk builds ever more spacious chambers for itself and each time settles in the last, largest one. By filling the remaining chambers with water or air, it can float or sink to the bottom. Jewelry and buttons are made from pearl ship shells.

The octopus order includes animals with 8 tentacles. One of the remarkable features of ordinary octopuses is their selfless care for their offspring. The female octopus vigilantly guards the laid eggs. As I.I. writes Akimushkin about one mother octopus who laid eggs in captivity, “if one of the servants dared to throw a piece of meat to her very head, Mephista flared up brick-red in anger, freed her hand from the makeshift basket and threw away her previously favorite food - after all, this “garbage” could get on her precious balls!”

Octopus eggs.

Octopus development.

Nautilus.

Cuttlefish, in the words of the British naturalist Frank Lane, “literally left a mark on human culture.” After all for a long time people wrote it in ink. The famous “bone” (the remains of a shell) of cuttlefish, which is collected on the seashore, is no less valued. It is used as a drawing eraser, in crushed form - as an additive to tooth powder, and also as a medicine.