Nematodes are small worms. The name nematode comes from the Greek word ‘nema’ that means ‘thread’.The soil inhabiting species are usually 1 mm long, but marine nematodes can reach lengths of over 5 cm, whereas animal parasites can vary from 10 to 30, 40 centimetre.
After Borellus in 1656 had observed "little snakes" in vinegar, he though he found an explanation for the acid taste of vinegar: the little snakes had pointy tongues. It took until 1742 before Baker broke this widespread myth. The nematode species Anguino tritici (a common parasite in wheat) is probably even mentioned by Shakespeare in his 1549 play 'Love’s Labour’s List' when he writes about 'sowed cockle, reaped no corn' describing the seed-galls in wheat plants.
Parasitic nematodes were already known in ancient Egypt. The 'Papyrus Ebers' dating back to 1500 BC contains accounts about roundworms and guinea worms. The latter is an 80 cm long nematode that prefers to live under human skin. Ancient Egyptians used a technique still used today: after a careful incision is made in the skin, the nematode is pulled out gently by winding it on a stick. This bares a striking resemblance to the 'Rod of Asclepius' sign still used by medical doctors!
Nowadays we look upon nematodes as a very successful class of animals. Four out of five multi-cellular animals on earth are nematodes. They're present almost everywhere: in cultivated fields, in sand dunes, in the sediments beneath the Ocean floor, in groundwater, in plants, animals and even in humans. Where there's organic material that can be decomposed, nematodes are present. A handful of dirt contains at least 50 different species of nematodes.
The nematologist Cobb wrote in 1914:
"Nematodes are extremely widespread, and to be found in most unexpected places; they are also inconceivably abundant. A thimbleful of mud from the bottom of river or ocean may contain hundreds of specimens. The nematodes from a 10 - acre field, if arranged single file, would form a procession long enough to reach around the world.
If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes."
Now we can add that we can also indicate the areas where a modern farmer should not grow certain crops, and where the soil needs a clean up sanitation. The number of nematodes per square metre varies from 2 to 10 million. It is estimated that 80% of all multicellular animals on earth are nematodes. Some nematodes are highly specific with respect to their food source. Potato cyst nematodes, for example, feed on potato only. Other plant parasitic nematodes feed on almost every plant species in the field. Apart from plant parasitic nematodes, there are also nematodes feeding on fungi, algae, bacteria, insects, or smaller nematodes. Remarkably, in more or less inactive stages, nematodes withstand freezing and desiccation rather well. When the environment becomes favourable again, they resume their activities.
The Nematode CollectionFor the study of plant parasitic nematodes as well as for the study of nematodes in relation to the environment it is of the utmost importance to know which species of nematodes are involved. The proper identification and name of the nematode is the key to the literature. The Department has invested considerably in the build-up and conservation of the Nematode collection. It consists of over 50.000 slides, with several hundreds of undescribed species, and it is one of the largest collections in the world.
The international position
One of the founders of nematology was Dr. Johannes Govertus de Man (1850 -1930), a biologist from Zealand in the South West of the Netherlands. He wrote over 160 papers on terrestrial, freshwater and marine nematodes. His descriptions of nematodes are still being consulted, and the original drawings are in custody with the Department. It is amazing how detailed his observations were at that time with the microscopes of the period.
In 1956 Dr. Michiel Oostenbrink was the first (part-time) Reader in Nematology to be appointed by the Crown at Wageningen University's Department of Plant Pathology. In this capacity and through his (main) position at the Plant Protection Service Dr. Oostenbrink played an important role in the development of Nematological research and education in Wageningen. Eventually his efforts led to the establishment of the Department of Nematology in 1972.
In the twentieth century the Netherlands has become an exporting country of agricultural commodities, such as potato. The intensifying agriculture, in which nematodes, especially potato cyst nematodes, increasingly became a problem, has led to the development of a new branch of nematology: plant nematology. The Department of Nematology, unique in the Netherlands, had up to 1980 been devoted to plant parasitic nematodes, although with some vision foresight, also attention was given to the systematises of free living nematodes. Many foreign students have received their nematology training here in Wageningen, and Wageningen has become well-known all over the world. Many researchers stay at the Department for specialized studies.
Research on the free living nematodes could develop rapidly after 1980, when the possibilities of using nematodes in environmental studies became apparent. Through the International Courses, participation in International Working-groups and the frequent worldwide personal contacts the Department has a very good International position.
Large amounts of nematicides are still being used; 60% of the total volume of pesticides used in this country, is used to control cyst nematodes. Since the use of traditional nematicides must be reduced, there is an increasing demand for alternatives. Studies on biological control as a possible alternative included in an Integrated Pest management deserve and get attention in an International context. There is a growing need for researchers experienced in physiological and molecular techniques, e.g. the development of monoclonal antibodies and genetic manipulation. In the future also in environmental studies the demand for nematologists will be increasing.
- Biography of Dr. Johannes Govertus de Man
- Wikipedia article about Dr. Johannes Govertus de Man
- 'Life and work of Dr. Johannes Govertus de Man'