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Genetics in parasitic nematodes

Adrian Streit

Adrian Streit

  • PhD at the University of Bern, 1991-94
  • Postdoc and Researcher at the Universities of Colorado, Zürich and Fribourg, 1994-03
  • Project leader at the MPI since 2003

Research Interest

The nematode genus Strongyloides consists of parasites that live as parthenogenetic females in the small intestines of their vertebrate hosts. In addition to producing parasitic offspring, the different species of Strongyloides can also form a facultative free-living generation with males and females. This complex life cycle gives these worms an ecologically and mechanistically most interesting "choice" between a parasitic life style associated with clonal reproduction and a free-living existence with sexual reproduction. The presence of a free-living generation offers a unique opportunity for the experimental manipulation of a true parasite. We combine molecular and genetic approaches to study life history switches, i. e. the switch between the parasitic and the free-living cycle and sex determination. Although sex determination in Strongyloides species is environmental, the two sexes differ in their chromosome content. Whereas in S. ratti males this is achieved by eliminating one of the two X chromosomes entirely (chromosome elimination), in S. papillosus males an internal portion of one of the homologs of one chromosome pair is eliminated (chromatin diminution).
 
In a second project we study the reproductive strategies and the population genetic structure of Onchocerca ochengi, a filarial nematode of cattle. This worm is most closely related to O. volvulus, which causes human onchocerciasis, also known as river blindness.

Selected Reading

1) Hildebrandt, J. C., Eisenbarth, A., Renz, A. and Streit, A. (2014). Reproductive biology of Onchocerca ochengi, a nodule forming filarial nematode in zebu cattle. Veterinary Parasitology 205, 318-329

2) Streit, A. (2014). How to become a parasite without sex chromosomes: a hypothesis for the evolution of Strogyloides sp. and related nematodes. Parasitology 141, 1244-1254 (Review)

3) Kulkarni, A., Dyka, A., Nemetschke, L., Grant, W. N. and Streit, A. (2013). Parastrongyloides trichosuri suggests that XX/XO sex determination is ancestral in Strongyloididae (Nematode). Parasitology 140, 1822-1830
 
4) Nemetschke, L., Eberhardt, A. G., Hertzberg, H. and Streit, A. (2010). Genetics, chromatin diminution and sex chromosome evolution in the parasitic nematode genus Strongyloides. Current Biology 20, 1687-1696.
(click to enlarge)
Life cycle of Strongyloides papillosus.