Dorylaimida

Abstract: PART I: ECOLOGY Introduction: summary of present knowledge and research addressing the ecology and taxonomy of freshwater nematodes, P De Ley, University of California, USA, W Decraemer, Ghent University, Belgium, and Eyualem-Abebe Techniques for processing freshwater nematodes, M Hodda, CSIRO Entomology, Canberra, Australia, and Eyualem-Abebe Composition and distribution of free-living aquatic nematodes: global and local perspectives, W Traunspurger and I C Michiels, University of Bielefield, Germany, and Eyualem-Abebe Dynamics of limno-nematodes: abundance, biomass and diversity, Eyualem-Abebe, W Traunspurger, and I C Michiels Production of freshwater nematodes, M Bergtold, University of Bielefield, Germany, and W Traunspurger Feeding ecology of free-living benthic nematodes, T Moens, Ghent University, Belgium, M Bergtold, and W Traunspurger Patterns in the size structure of freshwater nematode communities: the cases of Lakes Konigssee and Brunnsee, Germany, W Traunspurger and M Bergtold Freshwater nematodes in environmental science, S Hoes, W Traunspurger, and A Zullini, Universita di Milano-Bicocca, Italy Nematodes in lotic systems, M Hodda Nematodes from extreme freshwater habitats, M Hodda, A Ocana, University of Granada, Spain, and W Traunspurger Computation and application of nematode community indices: general guidelines, D A Neher and B J Darby, University of Vermont, USA PART II: TAXONOMY Order Enoplida, N Smol and A Coomans, Ghent University, Belgium Order Triplonchida, A Zullini Dorylaimida I: Superfamilies Belondiroidea, Nygolaimoidea, and Tylencholaimoidea, R Pena-Santiago, Universidad de Joen, Spain Dorylaimida Part II: superfamily Dorylaimoidea, M T Vinciguerra, Universita di Catania, Italy Order Mononchida, A Zullini and V Peneva, Central Laboratory of General Ecology, Bulgaria Orders Chromadorida, Desmodorida and Desmoscolecide W Decraemer and N Smol Order Monhysterida, A Coomans and Eyualem-Abebe Order Araeolaimida, A Muthumbi, University of Nairobi, Kenya and A Vanreusel, Ghent University, Belgium Order Plectida, O Holovachov, Ivan Franko National University of Lviv, Ukraine and P De Ley Order Rhabditida: Suborder Tylenchina, W Bert and G Borgonie, Ghent University, Belgium Order Rhabditida: Suborder Rhabditina, J Abolofia, Universidad de Jaen, Spain.

Abstract: Summary. Seasonal dynamics of soil nematodes and root biomass were examined from under western wheatgrass (Agropyron smithii) and little bluestem (Andropogon scoparius) from a heavily grazed prairie dog (Cynomys ludovicianus) colony occupied for 5 to 10 years and an adjacent lightly grazed, uncolonized area in Wind Cave National Park, South Dakota, USA. Nematodes were differentiated into classes of plant-parasitic Tylenchida and Dorylaimida and nonparasitic Dorylamida and Rhabditida. Root-feeding nematodes were generally more numerous from A. smithii than from A. scoparius, while nonparasitic populations were not different in soil from beneath the two plant species. Rhabditida, parasitic Dorylaimida and Tylenchida (from A. scoparius only) were more numerous on the prairie dog colony than from the uncolonized site, but nonparasitic Dorylaimida populations did not differ between the two areas. Mean total (live plus dead) root biomass beneath A. scoparius and A. smithii on the prairie dog colony averaged 71% and 81%, respectively, of values from the uncolonized area. Estimated consumption by root-feeding nematodes averaged 12.6% and 5.8% of annual net root production in the upper 10 cm from the prairie dog colony and uncolonized site, respectively. We conclude that, because of microhabitat modification or reductions in plant resistance to nematodes, heavy grazing by aboveground herbivores apparently facilitates grazing by belowground herbivores. Because heavily grazed plants have less roots than lightly grazed or ungrazed plants, the impact of root-feeding nematodes on primary producers is likely to be greatest in heavily grazed grasslands.

Abstract: Publisher Summary This chapter presents an ecological view of some aspects of plant-nematode interactions, while avoiding the pathogenic aspects of plant disease. The chapter presents the statistical view, interactions between nematodes and other factors on plants, implies that more information is needed on the effects of plants on nematodes. Two orders of nematodes have evolved dependence on plants, the Tylenchida, containing some 2,000 plant dependent species, and the Dorylaimida, some 200 species. This shows the degree of association between plant and nematodes is very diverse and maintain the view that while a few genera with sedentary, saccate females are plant-parasites in the strict sense, most nematodes have a looser, grazing or browsing association and are better termed plant-feeding. They and many of the less pathogenic Tylenchida are probably subclinical pathogens or “root pruners” and may have an important role in nutrient cycling through their influence on the microbial community surrounding the roots. The chapter concludes that the poorly defined feeding habits of nematodes, the absence of distinct trophic levels, the increase in quality or information content of food with progression from the autotroph, and stimulation of prey species by grazers or predators, their populations are worthy of study.