Natural chemical substances often act as information carriers, that is as a special code which living organisms use for intercommunication. Feromones are one graphic example. These are the substances that animals discharge into the environment and that have a specific effect on the behavior or physiological condition of kindred individuals.

Bombicol was the first sexual feromone to be isolated from a silkworm (Bombyx mori) female in the pure form. One insect was found to contain a mere 1.5 ug of this biologically active compound, but quite enough to excite as many as a billion males. In theory, of course. Since each worm weighs about 1 g, we get a million kg of silkworms hot with the procreation desire.

Ever since 1959, feromones and related substances have been the object of active research in this country and abroad. A wealth of data has been amassed to open up new dimensions on these compounds. And quite recently Dr. Sergei Ostroumov, a leading researcher at the Department of Biology (M.V. Lomonosov Moscow State University) supplied a more relevant definition.

"Feromones are individual substances or their mixtures (complexes, sets, combinations) which are discharged by organisms into the environment (air or water medium, or else on the body outer surface) and which perform the functions of an information signal usually meant for other individuals of the selfsame species; feromones can induce a definite response (relative to behavior, physiological and growth processes) in these individuals; feromones may act as stimulants or, conversely, as inhibitors for any particular reaction, forms of behavior or physiological processes in recipients."

Dr. Ostroumov notes in particular: in mammalians feromones and the related chemical communication have been best studied in mice as test objects. And best of all the effect of feromones on the condition of the hormonal system has been investigated in rodents. Hormones control the course of estrus (rut, heat) manifest in recurrent changes in the vagina of pubescent females, correlating with cyclic processes in their ovary and uterus. Copulation and fertilization occur only at the end of proestrus (a stage prior to estrus, or rut) and with the onset of estrus (rut, heat).

Witten's effect has also been described in mice: the smell of male urine stimulates and synchronizes the estrual cycle in females (the urine of emasculated males is devoid of this effect). As it has been found, the stimulating action is due to the compound dihydro-exo-brevicomin that works in this case as feromone.

In 1955 what has become known as Leigh-Boot's effect was discovered in mice: a group of females locked up in a cage showed deceleration of the estrual cycle down to its complete arrest (that is the diestrus period, or the time in between bouts of rut, became longer due to the lower level of estrogens in blood). This effect is caused by several volatile substances contained in the urine.

Further studies of feromones and the action of chemical communication they cause on rodents' beha-

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vior make one ponder over the possibility of like phenomena in other mammals, man including. Remarkably, Leigh-Boot's effect was observed in single-gender female colleges (with girl students not coeducated): the girls none of whom had met male undergraduates for a long time showed a menstrual lag.

Further studies into feromones may shed light on other intriguing facts and behavioral idiosyncrasies, in particular, help unlock the enigma of long-standing libido among Chinese emperors who, as historians tell us, would drink the urine of virgins so as to boost their virility.

Alongside feromones, there are several other categories of chemical substances carrying out a signal-emitting or a regulatory function. Here an important role is played by ecological chemomediators, or native chemical compounds that act as go- betweens and information carriers in the transmission of signals from one organism to another (sexual and aggregational feromones, etc.). Implicated in this process are ecological chemoregulators impacting the behavior, physiology and growth patterns. Assigned to this category are feromones produced by the only prolific queen in a beehive or the breeder female in an ant nest and modifying the physiology and behavior of the other individuals so much so that they lose reproductive functions.

Involved in ecological processes, these chemoregulators and chemomediators are an important tool for the corrective and selective effects on populations and ecosystems. They are of immense practical significance in farm production making it possible to cut the use of pesticides and apply instead compounds of selective effect, less toxic and decomposing more readily in soil and water.

Besides, there is an increasing amount of synthetic chemical substances present in the biosphere. Way back in 1990 their total list topped 6,000,000, and this number has been gaining 5 percent yearly. According to expert estimates, something like 6,000 compounds are synthesized each week worldwide. Only several thousand have undergone ecological and toxicological tests. And about 25,000 are potentially cancerogenic. They pollute the atmosphere, soil and water.

A grave hazard is posed by synthetic surface-active substances (surfactants) acting upon water media. These compounds are but poorly eliminated in biological purification installations and get into effluents. As much as 2.5 g of surfactants is produced per capita in Russia daily, and this is quite a bit. The presence of synthetic surfactants in bodies of water is a hazard for their self-purification potential, it poses a threat of imbalance in the extant trophic chains. These substances inhibit the vital activity of many species, as seen in the example of bacteria and cyanonacteria, diatoms and green algae, flagellates, higher plants and invertebrates (annelides, pulmonate and bivalve mollusks, etc.). Thus, sea mollusks, among them mussels (Mytilus edulis, M. galloprovincialis) and oysters (Grassostrea gigas), respond by a lower rate of water filtration, that is the process of water self- purification is impaired. In fact, the present condition of aquatic populations in Russia, CIS countries, in Europe and America is a cause of legitimate anxiety. For instance, the Russian Federation's Red Data Book lists over 30 endangered taxa of bivalved mollusks.

This problem has both ecological and economic implications. According to most conservative estimates, the natural filtrating activity of a community of mollusks in an area of 84 m ² is comparable to a corresponding purification setup worth 400 USD. And if the area is 600 m² , the cost will be up to 6,700 USD. Therefore a broader approach is needed to the problem of pollutants and xenobiotics. Conventionally, it has been practice to estimate the hazard by the number of lethal cases of the living organisms affected. Yet it is likewise necessary to count in factors that reduce the native capacity of ecosystems for self-purification as well as other effects.

At the same time, a comparative study of sensitivity to surfactants on the part of organisms in various links of the food chain of water ecosystems has shown the auto- trophs of the lowest level (including one-celled organisms of the phyto-plankton) to be more resistant to chemicals than those of higher levels. One and the same contaminant has been found to affect organisms of two coupled trophic levels in such a way that the combined effects of its action threatens to upset equilibrium in an ecosystem dramatically at the expense of one of the two.

Ostroumov S., "On Functions of Living Matter", Vestnik Rossiyskoi akademii nauk (Bulletin of the Russian Academy of Sciences), Vol. 73, No. 3, 2003

Digest prepared by Igor GORYUNOV

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