Remote outer space exploration, experts believe, would be unthinkable without biological components, including animals, introduced in the astronaut's life-support system. Research carried out over the past decades shows that Japanese quail, a small bird with a lot of quite valuable qualities, serves as the optimal object for work in this sphere.

If man sets himself the task of conquering new planets, he will need an autonomous protein food source on board spaceship, for food deliveries from the Earth would be out of the question*. The most rational solution would be to take along small egg-laying poultry. However, hens, for instance, as carriers of many infections, primarily salmonellosis, would be hardly suitable for the purpose. Fortunately, we have a bird of the same order, i. e., Japanese quail (Coturnix coturnix japonica), that has a high body temperature and is not susceptible to most of the infectious diseases and that had been domesticated back in the 11th century in the Land of the Rising Sun.

GALLINACEOUS USED IN OUTER SPACE

Under favorable conditions, quails weighing some 100 - 120 g start laying egg on the 36th day of their life, on average as soon as they are 40 - 42 days old (the respective figure for hens is 180 - 210 days). In their lifetime of 11 months quails manage to lay 300 small tasty eggs of 10 - 12 g each. Five quail eggs, equal in weight to one hen egg, contain 400 percent more potassium, 350 percent more iron and 150 percent more vitamins B₁ and B₂ and a considerably greater amount of vitamin A, nicotinic acid, phosphorus, copper, cobalt and various amino-acids. Protein accounts for 60 percent of the quail egg as against 55.8 percent of the hen egg. Moreover, quail eggs are a hypoallergenic product which fact makes them a unique component of the diet for adults and children

* See: Ye. Sidorova, "Greenhouses for Orbital Stations," Science in Russia, No. 3, 2006. - Ed.

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for a number of diseases. And they can be stored for a very long period of time owing to their natural sterility.

To put it in a nutshell, Japanese quail wins the day in decision-making on its inclusion in the cosmonaut's life-support system. However, the big question is whether or not the birds will be able to develop in full in the absence of gravitation. Various kinds of research have been carried out in a number of countries in the past three decades in search of an answer to this question. Yevgeny Shepelev, D. M., of the RAS Institute of Medical and Biological Problems, and Academician Koloman Bodja of the Slovak Academy of Sciences stood at the source of this research. Joint research had been carried on under their guidance since 1970.

In the initial stage they set themselves the task of making adult quails feel at home in small space and of providing all conditions to them required for life in a spaceship. That is, it was necessary to work out the respective nutrition system for the feathered passengers and find a way for reclamation of their droppings and fallen feathers.

Since it was impossible for birds to drink water under conditions of weightlessness, Irina Abakumova, a staff member of the Institute, has developed methods for obtaining paste-form sterile feed with all necessary components and water content up to 80 percent. The special containers, prepared then, make it possible to store it without any change in its content until now. And staff members of the Leningrad (now St. Petersburg) Biofizpribor institute have developed the method of drying up droppings in the chamber-receptacle of droppings by means of air currents.

However, quail eggs were sent into outer space even before adult quails: in 1979 40 quail eggs, placed in a special incubator with cells fastened on rubber braces to compensate for shock overloads, spent 12 days on board Kosmos-1129 biological sputnik. As ill luck will have it, most of the eggs were broken in the process of the descending capsule's landing. However, for the first time biologists had the opportunity to observe the process of the embryo's development under conditions of a space flight.

Key changes take place on the 3rd, 7th, 10th and 14th day of the Japanese quail's prenatal development. A program providing for the embryos' fixation within these time limits has been prepared by the researchers for further work.

A total of nine experiments with the Japanese quail's eggs were staged on board the Mir orbital station, with the most important of them all held in March 1990. Then for the first time the task was set of further incubation for 48 eggs until chick hatching (it happens on the 18th day) and of studying their behavior under conditions of a space flight. The crew made special preparations for that work. This is what Tamara Guryeva, Cand. Sc. (Biol.), a staff member of the Institute, recollects: "The technical aspect of the problem had been resolved, but we did not know what would happen to living chicks." Yevgeny Shepelev, the program's manager, believed that even if just one chick survived, that would be a good result.

In such experiments much depends on the personal qualities of the person who is directly charged with the job. And in this respect the researchers were quite lucky: pilot cosmonaut Alexei Solovyov, a very competent man, was entrusted to work with the quails. He had displayed interest in the new subject, conducted five experiments and kept notes at his own initiative and even shot a film. Owing to this, he managed to learn more about the feathered passengers' behavior.

As soon as he heard the chirping of the first hatched chick at 21:00 Moscow Time, Solovyov contacted the research

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Incubator-2 complete set of equipment designed for experiments with birds on board the Mir station.

group, although the time was not suitable for communications, in order to tell the happy news to the researchers who had been waiting impatiently for it. The "newborn" was taken out and placed into a chamber specially assigned for it, with stable temperature of +35°C and the respective humidity maintained in it. Further observation was impossible, for the space flight members had to strictly observe the daily routine, and it was time to go to bed.

They found out in the morning that the chick, helping himself with his wings, was constantly chaotically rotating being carried away by air currents. As a result, he lost the ability to fix his eyes on anything and could not take food. The six quail chicks that hatched later were placed into narrow cells, and they ate from the people's hands. However, as soon as they had lost this "support," they also proved nonviable. In their observation of those fledgelings in the first and later experiments, the researchers of the Institute came to the conclusion that their behavior completely depended on the gravitation factor. However, if the fledgelings were supported for 10 days of their life, they would be able to go on living, eat on their own and even propagate.

DEPENDENCE UPON GRAVITATION

It should be pointed out that adult birds, brought to the Mir station in 1990, felt quite well in flight. They ate much and with gusto (as mentioned above, the paste-form feed also had a water content, that is why it was consumed in excessive quantities) and oriented themselves inside the station. For instance, a two-month female quail was able under conditions of weightlessness to fly on her own into the chamber where other quails were feeding. One of the quail females even laid an egg that was in her egg-duct before the space flight. At the Institute researchers' request, cosmonaut Gennady Strekalov kept it separately in the refrigerator, and after the landing and the expiration of the usual incubation period, a normal fledgeling hatched from it that later lived at the Institute until his ripe old age.

Upon their return to the Earth, adult quails suffered from the effects of gravitation, they would drop their head low and bend their legs. However, the fingers of their feet were spread out and they could well support themselves. The researchers examined the male quail's testicles and found that his spermatogenesis deviated from the standard, probably as a result of the space flight stress. However, after a certain period of time the birds completely adapted themselves, and 12 days later the female quail laid an egg. No deviations were revealed in the feathered cosmonauts' progeny. "Had we made them stay longer in weightlessness, they might have mated there, too," Tamara Guryeva says.

The ground experiments with the Japanese quail's chicks, staged currently by Anna Filatova, a post-graduate at the Institute, show that after vertical rotation in klinostat at a speed of 2.0 rpm (in this way the same stress conditions are created as those observed in transition from weightlessness to the gravitation-dependence system) it will take the birds from 0.5 to 5 min. to adapt themselves (to restore their ability to peck grain on their own), even in the absence of sound or sensor signals.

As to the process of chicks hatching from an egg, the process was the same as on the Earth. According to histo-

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That's how Japanese quail embryos looked on the 16th day of their development (experiment in 1996): a - a normally developed embryo of the outer space experiment, b - a normally developed embryo of the laboratory control.

logical research data, upon the completion of the space flight practically all chicks met the standards of their four-day development. True, their weight was to a certain degree less. The study of the embryos' morphology has shown that up to seven days of their life they have no deviations from the standard but on the 14th - 16th day retarded bone formation (osteogenesis) is observed in the lower extremities, with the usual stages of cartilage transformed into bone preserved. The repeatedly staged experiment and a great amount of the embryological material allow us to draw trustworthy conclusions. No other deviations of quail "cosmonauts" from the control versions have been established. This is most probably attributable, in expert opinion, to the absence of gravitation in the period of embryogenesis, for it was precisely thighbones, i. e., support bones, that grew more slowly, while the wing preserved its normal parameters even under conditions of weightlessness.

In the further analysis of special features of osteogenesis in Japanese quail's embryos, which developed in outer space, the researchers established that calcium content in their bone tissue was to a certain degree below the standard amount, but the phosphorus content remained unchanged. Curiously, the process is reversible as soon as the bird finds itself back on the Earth.

In 1999 the last (joint Russian-Slovak) experiment on bird hatching was conducted on board the Mir space station in the course of which every effort was made to bring the chicks back to the Earth alive. The Slovak cosmonaut Ivan Bella was the man directly in charge of the experiment. On that occasion only five of the 16 hatched chicks were lucky to stay alive (even more of them could have survived but for the unexpected sharp drop in temperature in the descending capsule). Just as the adult quails, the quail chicks first suffered from the effects of gravitation by falling to the side, but they adapted themselves quite rapidly. The

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examination of their bone and muscle tissue showed that after a certain period of time they became normal, although the shortage of calcium remained. The thighbone and shin were taken for analysis, and the researchers tried to determine which of the Ca isotopes was assimilated better. Regrettably, this work, started by specialists of the Institute and of the Moscow Technical University named after N. E. Bauman, has been suspended for an indefinite period of time.

The results of studies of the Japanese quail's histogenesis deserve separate comment. In the course of nine experiments the Institute's biologists have accumulated a sufficient amount of material in order to present an exhaustive picture from the start of the incubation period to the fifth day of the chick's life. It will not be an overstatement to say that the work performed by histologist Tamara Guryeva and embryologist Olga Dadasheva is quite unique.

At least 30 embryos of various ages (of 3, 7, 10 and 14 days) were obtained in the course of the space flight. Their organs and tissues developed normally (just as on the Earth), their alimentary tract was functionally prepared for feed digestion and assimilation. Deviation was in the form of the excessively porous connective tissue, for there was no clear-cut stroma in it.

No changes were revealed in the internal organs' topography and morphometry: the percentage ratio of their weight, size and body parameters was standard. However, focal epithelium hyperplasia was observed in the duodenum, which fact leads to the disruption of feed absorption and parietal digestion. Just as a number of other authors who have published data on the living being's development in outer space, the Institute's specialists have come to the conclusion that under those conditions the division of the body cells (proliferation) outstrips their differentiation. The reasons behind this phenomenon are so far unknown. That may be the body's stress reaction to change in the environment.

The chicks had clearly manifested liver dystrophy, fatty degeneration, venous stagnation and a hightened leukocytic activity. What could be the reason behind it? Tamara Guryeva believes that the fact is most probably attributable to hunger (the cosmonauts cannot constantly feed the quail chicks, who, under conditions of weightlessness, are unable to eat on their own) and, consequently, this process is reversible. The corresponding experiment is currently being conducted at the Institute for checking this hypothesis. However, the Slovak researchers are of a different opinion. They believe that changes in the chicks' liver come as a result of the disruption of the process of absorption of nutrients under conditions of weightlessness. However, in order to support this viewpoint it is necessary to exclude hunger as the reason behind the event.

MYSTERIES TO BE UNRAVELLED

Joint Russian-American research into incubation of quail eggs under conditions of weightlessness was launched in 1995 within the framework of the NASA program. A three-stage protection system, i. e., three tightly closing Teflon containers, one fitting into another, was developed for biological material fixed in a chemical reagent to be kept on board the space station. The novelty made it possible to use paraformaldehyde as a fixing agent well preserving tissues and to analyze the embryos' histology in greater detail than before. They staged a total of three experiments: one in 1995 and two in 1996.

So, what were the results of the histological research into the selected material? In the "outer space" version the quantity of deviations in the embryos accounted on average for 15 percent of their total quantity, whereas in the "ground' version the respective figure was 1 - 2 percent. The revealed pathologies were of four types: first, anaphthalmia (the absence of an eye) or micro-phthalmia (one eye is smaller than the other), second, deviation in beak development (the upper plate is smaller than the lower one), third, ectopia (the abdominal cavity not closed), fourth, four legs or screwed up legs.

The US specialists studied the embryo with four legs corresponding to 14 days of development. It was revealed that

Japanese quails' poses: a - after their return to the Earth (outer space experiment); b - synchronous control.

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That's how Japanese quail embryos looked on the 7th day of their development (experiment of 1996): a - an embryo of the outer space experiment with a deviation in eye development (micro-phthalmia); b - a normally developed embryo of the outer space experiment, c - a normally developed embryo of the laboratory control.

the tail part of the spinal column was cleaved, with two legs growing on each side. At present we have several explanations of the origin of such anomalies under conditions of space flight. For instance, Yevgeny Shepelev believed that in the stage of putting the spaceship on the orbit the vibration and overloads could lead to change in the embryo's position in relation to the egg's important components (air chamber, yolk and white). And under conditions of weightlessness structural displacements are consolidated. However, there is an objection to this version: all eggs are shaken but most of the embryos have no deviations.

Anomalies in the Japanese quail's development could have come as a result of disruptions in the incubation temperature and humidity modes under conditions of weightlessness, according to Vladimir Sychev, Dr. Sc. (Biol.), manager of the Institute's laboratory of biological life-support systems. The fact is that detailed monitoring of maintained parameters had not been provided for in Incubator-1M instrument used for experiments in outer space. That is why the probability should not be ruled out of the existence of zones within its space where gaseous phase indicators differed from the optimal ones that were observed on the Earth.

Tamara Guryeva believes that the galactic radiation or general radiation effect in the course of the space flight may be the reason behind the above-mentioned anomalies. In order to check this viewpoint, researchers at the Institute began studying the effect of small chronic radiation doses on the Japanese quail's embryos.

Their first experiments showed that gamma-radiation had no effect at all on the embryos' development, while neutron radiation produced the same picture that had been observed in experiments on board the space station. True, there were less embryos with deviations in their development, but the combination of deviations was the same - abnormal development of leg bones, not closed abdominal cavity, eye anomaly and underdeveloped brain hemispheres. The effect of radiation, Guryeva believes, is the most significant in the early period of embryo development. But this cannot be asserted as an indisputable fact, for all those pathologies also occur on the Earth. Consequently, the specialists should work on the statistics of such episodes.

The Japanese quail has proved a highly promising object not only for the development of biological life-supporting systems. As a result of research in this sphere, a lot of data of great interest to evolutionary biology was obtained. Observation of embryogenesis under conditions of outer space was also carried out on other objects. For instance, a pregnant rat lived on board a biological sputnik for two weeks. But in this case the mother's body was able to protect the future offspring. However, the Japanese quail is self-sufficient from the outset. Moreover, just as man, it is in need of support. The fact is that the man and the quail have a similar behavioral model under conditions of weightlessness.

Regrettably, the ISS does not carry equipment for experiments with birds at present. However, experiments on the Earth's surface do not provide grounds for final answers to the questions posed in the course of the previous research. What is the reason for the origin of the Japanese quail embryo anomalies? To what degree is the process of dwindling calcium content in the chicks' bone tissue reversible? Is there an opportunity for the fosterlings' adaptation to weightlessness conditions? Shall we be able to keep an animal population on board a spaceship in the period of a very long flight to other planets?

The fact is that the answers are also important from the viewpoint of providing an adequate life-support system to cosmonauts in their future interplanetary flights.