Claude Dejoux: a career in the name of entomology

Interview of Claude Dejoux
Wetland entomologist
IRD Retiree – Chad – Bolivia – Mexico
Professional career path

Fascinated since childhood by the “things of nature”, I opt for a scientific baccalaureate called at the time “Modern Prime”. With this last diploma in my pocket, I set off in search of a training course in which water would play a main role, with in mind the idea of making fish farming more scientific than simply intensive fish farming. My eyes move towards a “Waters and Forests” training, when I discover by chance that the ENSAT (Toulouse National School of Agronomy) offers specialized training in fish farming and water biology…

Party for the “Pink City” for a year of preparation, I join this school but quickly realize that this speciality announced is very badly taught there, even without interest. I am there… I remain there, but a little disillusioned and, having the possibility to follow at the same time a faculty, I aim in parallel to obtain a degree in Biology at the Faculty of Sciences of Toulouse.

Lot of work at stake, but also the benefit of rubbing shoulders with two different types of teaching, one very practical in Engineering School and the other very theoretical and cumulative in University. These two ways of acquiring knowledge will thus be beneficial to me for a long time thereafter.

Claude Dejoux studying aquatic insects of Lake Chad (Source : C. Dejoux)

Obtaining a degree in Biology and a diploma in Agronomy, I have my passport to a research career in ecology, with as starting tools mathematics, physics, chemistry and general biology, including a certificate of degree specialized in entomology ! Learning by chance that the Office de la Recherche Scientifique et Technique d’Outre-mer (ORSTOM) (now IRD) recruits hydrobiologists, I apply by a simple letter and am immediately accepted as a student researcher, a sweet era unfortunately over!

After a year and a half of additional training in different laboratories (Paris in Oceanography, Biology, Banyuls and Biarritz in Hydrobiology, CNRS of Gif-sur-Yvette in Hydrobiology, Institut Max Plank de Plan in Germany for a specialization on the study of Diptera Chironomidae and in Hamburg on water pollution problems), I do three months of “classes” in France, before leaving to finish my military service, in 1964, as VSN (National Service Volunteers) in Chad, where I will stay to work for about ten years within the framework of ORSTOM.

Having initially chosen the aquatic insects component when ORSTOM set up its hydrobiologist team in Chad, I first worked on Lake Chad, then on other aquatic environments in the country. Taxonomy and ecology of Chironomidae occupy most of my time in the early years, given their importance in the food chain of fish and birds in this ecosystem, work that will lead to a state thesis supported at the University of Orsay.

Larvae of the species Simulium damnosum (simulia) on a leaf (Source : C. Dejoux)

The project of setting up by the OMS (World Health Organization) a long and vast program to control onchocerciasis, filariasis transmitted by a simulia (small dipteran whose larvae live in the running waters of West African rivers and streams) is for me an opportunity to apply my knowledge on aquatic insects. The program aims to eradicate this diptera in the main watercourses by applying insecticides weekly to the breeding sites for about 20 years, while preserving the other non-target aquatic species.

Before leaving Chad for Côte d’Ivoire, the more central operational base for this program, I develop several systems for toxicity testing of “candidate” insecticides, both in the laboratory and in situ in rivers. These impact research methods will be used and refined during the 7 years that will last my collaboration to this program which will finally prove a success. Focussed for several years on the problems of damage to aquatic environments by pesticides and all other causes of pollution, I was mandated in 1984 by the international program “GEMS Water” (Global Water Quality Monitoring Program) to search throughout West Africa for reference laboratories that could carry out regular sampling and analysis feeding the database of this global monitoring. This will lead me to the writing of a synthesis work on the pollution of African continental waters published in 1988 (Editions ORSTOM).

Having trained enough local technicians to continue a job that has become routine, I accept ORSTOM’s proposal to take over the representation of this institute in La Paz, Bolivia. The administrative task is heavy but I find the opportunity to study the entomofauna of the Bolivian part of Lake Titicaca and, with a colleague algologist, to carry out a synthesis of limnological knowledge of this magnificent high altitude environment. This synthesis will be published in 1992 (Editions Kluwer) in the series of biological monographs of the great lakes of the world.

Water pollution in Chalco, peripheral district of Mexico City (Source : C. Dejoux)

After 4 years (1985-1989) spent working between 3 500 and 5 000 meters of altitude, I go down a little by accepting the post of Representative of the IRD in Mexico in 1992, where, at an ideal altitude of 2 400m, I still need to share oxygen with some 20 million fellow citizens! I will end a career that will become administrative, but made of coordinating multidisciplinary programs that will give me an ecological vision (in the etymological sense of the term…) of the problems related to the preservation of different types of environment on our planet. This vision of interdependence of ecological factors will, once I retire in 1996, allow me to intervene on various environmental problems in several countries of the world through the ECTI, an association of senior volunteers.

Importance of insects in aquatic environments

While practically absent from the oceans (only one family of semi-aquatic Hemiptera occurs there : Halobatidae), insects inhabit all freshwater environments with in some a very great diversity.

In most cases, they spend their larval and pupal phase (Odonates, Ephemeral, Diptera, etc.), the adult phase being aerial, allowing dissemination and reproduction. True microcosm (although some species reach several centimeters), they have an important role in the equilibrium of aquatic biotopes by participating in the degradation of organic matter as primary decomposers (by fragmentation, ingestion and defecation), before the action of secondary decomposers, worms and bacteria for example.

PVC gutteraterie for simultaneous testing of several insecticides (Source : C. Dejoux)

Their role is equally important in the food chain, serving as food for many fish, amphibians and birds after eating microalgae or macrophytes themselves. The food bowl of some African fish like Mormyridae can be exclusively composed of larvae of Diptera Chironomidae (“red mud worms” of fishermen), like that of some Anatidae (ducks) feeding on shallow mudflats. Let’s not talk about all the opportunistic species: fish, amphibians, birds that force-feed themselves for example during mass emergences of Ephemeres.

Penetrating the environment of aquatic insects also means being surprised by the adaptations they have developed to colonize all kinds of micro-environments and, for each species, seeking its preferendum environmental. Understanding why a species is or is not present in an environment is the key to dynamic ecological studies and helps better analyze the impacts of hydrosystem stress.



Insects, bio-indicators of pollution

If we take the term pollution in its broadest sense, i.e. an attack on the aquatic environment with negative impact on its integrity, insects are a very good analytical tool. They each have, like every living being, their weaknesses, both physical and physiological and, depending on the nature of a pollution and knowledge of the ecology that can be called “intimate” species present, it is possible to determine which species will be most affected.

Toxicity tests between two insecticides in situ (Source : . C. Dejoux)

Many indices have been proposed by different authors to quantify a level of pollution or health of an aquatic biotope: many use insects in their calculation. For river studies, for example, the most frequently used index in France is lIBGN (Normalized Global Biological Index) which, depending on the relative densities of certain insect families (Trichoptera, Ephemeroptera, etc.), results in a final score that is intended to characterize the level of aggression of the environment. These methods are rapid but poorly reflect the action of pollutants and cannot take into account certain natural disturbances that occurred some time ago and whose effect may affect the hydrogen system in the medium term. A good general knowledge and over a long period of time of the dynamics of the environments studied makes it possible to weight the result of specific analyses.

It is certainly by combining these two types of knowledge that we have managed, in African rivers treated with anti-simulidian insecticides, to evaluate the long-term impact on entomocenoses (communities of interdependent living beings, here insects, occupying the same biotope). This impact was rather low with Téméphos (organophosphorus insecticide) used for a long time, higher with Chlorphoxim (chlorinated organ) introduced later to avoid developing cross-resistance in target insects and practically zero with the use of Bacillus thuringiensis (BTI, strain H14-De Barjac). Among the families most sensitive to the first two compounds, we should mention the Ephemera of the Baetidae family as well as the Perlidae.

Pollution of aquatic environments in different countries and general environmental pollution

Initial data (time, temperature, etc. at a certain date) are still often lacking to make precise decisions on the evolution of pollution of global aquatic ecosystems (even if this was the aim of the GEMS Water programme).

My own experience makes me say that it is generally better in many countries, and increasingly worrying in others ! It is better when appropriate legislation regulates polluting discharges into aquatic environments, even the simplest use of natural fresh water. It is worse when nothing protects these environments or when legislation is not enforced.

Harvesting benthic fauna from Lake Titicaca using an Ekman bucket (Source : C. Dejoux)

In many countries, man considers rivers as simple sewers, capable of both digesting everything without consequences and especially transporting waste… elsewhere ! The permanent increase in the world population, linked to greed for profits, are two extremely worrying factors. Canalised waterways, galloping urban planning, deforestation, excessive use of pesticides, water-hungry agriculture are all factors that affect aquatic environments, even if the presence of treatment plants (where they exist) is a positive factor and give in good conscience.

Without plagiarizing Arthus Bertrand or Nicolas Hulot, for example, I have had the opportunity to see in China rivers polluted by pesticide runoff from intensive agriculture, various mining residues or “serious ecological” accidents that destroy all aquatic life for many months, rivers that carry millions of cubic meters of mud in connection with the deforestation of watersheds. In Morocco, drinking water in Rabat is difficult to treat because of the eutrophication of supply lakes, a phenomenon linked to the leaching of land receiving too much fertilizer. In Bolivia, a textile factory discharging its “coloured effluents” directly into the Rio la Paz… which had become azoic for kilometres, or iron mine effluents discharged directly into a lake whose pH had fallen to 1.5. In Mexico, waste water discharges from Mexico City causing rivers receiving them from moss mountains resulting from the misuse of domestic detergents…

All this only concerns water, but it is possible to make similar observations concerning land or air and it is only necessary to look at the pollution rates in the big cities or to note the degradation of the natural grounds because of an intensive agriculture not reasoned, the loss of herbaceous cover leading to erosion, runoff and losses of organic matter…

I think that awareness exists, but remains insufficient. A greater effort is needed to inform young people and ecology, in the noble sense of the term, should have a prominent place in school curricula.

Evolution of environmental damage in the world

Although it is necessary to distinguish situations according to the degree of development of the countries concerned, I think that almost everywhere it is possible to distinguish two phenomena whose results are opposed. On the one hand, the almost exponential increase in the world’s population is creating more and more needs to feed and ensure the broad life of all these people. This implies an increasingly large and sometimes (often?) anarchic exploitation of all natural resources, with known consequences on the environment: deforestation, depletion of fossil energies, intensive agriculture depleting soils (or extensive reducing biodiversity…), destruction of natural habitats for simple profit, the list of impacts of this growing humanity is long and we list here only a few macro phenomena .

In opposition, many scientists or ordinary citizens have become aware of this situation and are trying to slow it down or find alternative solutions. Ecological knowledge has improved enormously and it is no longer necessary to see fish with their bellies in the air in a watercourse to realize if the environment is polluted. Similarly, it is now realised that over-intensive use of irrigation depletes the slicks faster than they recharge and, above all, reduces the natural fertility of the soil by leaching.

A little everywhere movements are created for the respect of nature, the preservation of a biodiversity are the degree, low or high, reflects in part the good or bad health of our planet. Agro-ecology proves that we can feed many people without growing salads without soil in huge sheds! Recycling, in the broad sense of the term, is slowly becoming an economic philosophy with beneficial effects (see the article on entomoculture).

Region by region, the current situation will be a result of these two major trends, but I think it will still take time for us all to realize the need to respect as much as possible this enormous potential that surrounds us: water, air and land !

To often still, the verb avoir is preferred to the verb be and the word “profit” governs our behaviors. For example, I carried out two missions to lower Mongolia in China, at the same place, 7 years apart. The first was aimed at the preservation and restoration of wetlands in the north of the Tibetan massif. The second, more general ecological, was linked to the success of the national reforestation programme in northern China to slow desertification.

My first mission report recommended conservation measures for existing wetlands and, above all, sounded the alarm in the face of anarchic use of local water resources. Seven years later, the city that welcomed me had grown from a population of 300,000 to over a million. Gigantic buildings grew from all sides, beautiful parks abundantly watered decorated the residential districts and, icing on the cake, a large artificial “recreational” lake had been created, fed by pumps taking water from the nearby river which was no more than a “skeleton” of rivers. Besides this, the whole river valley downstream from the city, where 7 years earlier flourishing agriculture existed, had become almost desert and to feed thousands of additional inhabitants, all vital foodstuffs were imported from southern China. Not to mention the thousands of dead trees at the site of the famous “green belt”, due to the lack of minimum water supplies !

I could thus multiply these examples of environmental abrasion such as the almost total drying up of part of the Volta river to water the sugar belt of Banfora in Burkina Faso, or the cotton crops in the Sahelian zone which devastated the bush at the expense of food crops to finally lead to a practically worthless production on the world market. In Bolivia, Lake Titicaca, which was full of life in its south-eastern region in the 1980s, became in this region a soup of algae without fish by hyper eutrophication, because of the accumulation of nutrients coming from the leaching of agricultural lands along its shores.

Of course we must not see that this bad side of our aggression of natural environments because beautiful actions exist elsewhere, but to signal them helps to an awareness of our responsibilities with regard to our living environment.

A particular anecdote
Hydrobiological helicopter of the WHO onchocerciasis control programme (Source : C. Dejoux)

After writing a report against the use of an insecticide proposed by the long-term treatments by the firm Bayer, this work was challenged and to prove the safety of the product an “expert” was sent to Côte d’Ivoire for verification. With him we did tests in situ with full-scale treatments, with our equipment developed for this purpose and by comparing on two different diversion bays the impacts of the insecticide usually used with that of the new proposed. The result having been essentially the same: unfavourable to the new product, the expert’s argument was that we should have done the test at the same time and in a rapids zone, with on half of the river a treatment with a product and on the symmetrical half with the Bayer product! When we know the turbulence associated with the rapids, it is hard to imagine cutting the reach lengthwise so that each product remains on its side! We never heard from the expert and his possible report.

  • Photo album
« 1 of 2 »

In the same section, you can discover the interviews of

Chargé de recherche – Entomologiste chez Cycle Farms