A bias caused by ectopic development produces sexually dimorphic sperm in nematodes

Christopher Baldi, Jeffrey Viviano, Ronald E. Ellis

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Self-fertile hermaphrodites have evolved independently several times in the genus Caenorhabditis [1, 2]. These XX hermaphrodites make smaller sperm than males [3, 4], which they use to fertilize their own oocytes. Because larger sperm outcompete smaller sperm in nematodes [3-5], it had been assumed that this dimorphism evolved in response to sperm competition. However, we show that it was instead caused by a developmental bias. When we transformed females of the species Caenorhabditis remanei into hermaphrodites [6], their sperm were significantly smaller than those of males. Because this species never makes hermaphrodites in the wild, this dimorphism cannot be due to selection. Instead, analyses of the related nematode Caenorhabditis elegans suggest that this dimorphism might reflect the development of sperm within the distinct physiological environment of the hermaphrodite gonad. These results reveal a new mechanism for some types of developmental bias - the effects of a novel physical location alter the development of ectopic cells in predictable ways.

Original languageEnglish (US)
Pages (from-to)1416-1420
Number of pages5
JournalCurrent Biology
Issue number16
StatePublished - Aug 23 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)


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