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Genome size and chromosome number in velvet worms (Onychophora)

Abstract

The Onychophora (velvet worms) represents a small group of invertebrates (~180 valid species), which is commonly united with Tardigrada and Arthropoda in a clade called Panarthropoda. As with the majority of invertebrate taxa, genome size data are very limited for the Onychophora, with only one previously published estimate. Here we use both flow cytometry and Feulgen image analysis densitometry to provide genome size estimates for seven species of velvet worms from both major subgroups, Peripatidae and Peripatopsidae, along with karyotype data for each species. Genome sizes in these species range from roughly 5–19 pg, with densitometric estimates being slightly larger than those obtained by flow cytometry for all species. Chromosome numbers range from 2n = 8 to 2n = 54. No relationship is evident between genome size, chromosome number, or reproductive mode. Various avenues for future genomic research are presented based on these results.

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Acknowledgments

The authors are thankful to Susann Kauschke for maintaining the animals and to Noel N. Tait, Alfredo Hannemann Wieloch and Alvaro Herrera Villalobos for their help with permits. The staff of Forests NSW (New South Wales, Australia), the Instituto Nacional de Biodiversidad (INBio, Heredia, Costa Rica), the National System of Conservation Areas (SINAC, MINAE, Costa Rica), and the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio, Brazil) are gratefully acknowledged for providing collecting and export permits. I.S.O. is supported by a PhD fellowship of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq: 290029/2010-4). G.M. is a Research Group Leader supported by the Emmy Noether Programme of the German Research Foundation (DFG; grant Ma 4147/3-1). N.W.J. has been supported by Natural Sciences and Engineering Research Council of Canada (NSERC) postgraduate scholarships and an Ontario Graduate Scholarship. T.R.G. is supported by an NSERC Discovery Grant.

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Correspondence to Nicholas W. Jeffery.

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Jeffery, N.W., Oliveira, I.S., Gregory, T.R. et al. Genome size and chromosome number in velvet worms (Onychophora). Genetica 140, 497–504 (2012). https://doi.org/10.1007/s10709-013-9698-5

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  • DOI: https://doi.org/10.1007/s10709-013-9698-5

Keywords

  • C-value
  • Nuclear DNA content
  • Peripatidae
  • Peripatopsidae
  • Flow cytometry
  • Feulgen image analysis densitometry
  • Karyotype