The control of morph development in the parasitic nematode Strongyloides ratti

S. C. Harvey, A. W. Gemmill, A. F. Read, M. E. Viney

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76 Scopus citations


The parasitic nematode Strongyloides ratti has a complex life cycle. The progeny of the parasitic females can develop into three distinct morphs, namely directly developing infective third-stage larvae (iL3s), free-living adult males and free-living adult females. We have analysed of the effect of host immune status (an intra-host factor), environmental temperature (an extra-host factor) and their interaction on the proportion of larvae that develop into these three morphs. The results are consistent with the developmental decision of larvae being controlled by at least two discrete developmental switches. One is a sexdetermination event that is affected by host immune status and the other is a switch between alternative female morphs that is affected by both host immune status and environmental temperature. These findings clarify the basis of the life cycle of S. ratti and demonstrate how such complex life cycles can result from a combination of simple developmental switches.

Original languageEnglish (US)
Pages (from-to)2057-2063
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1457
StatePublished - Oct 22 2000

All Science Journal Classification (ASJC) codes

  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Environmental Science
  • General Agricultural and Biological Sciences


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