Genome size and chromosome number in velvet worms (Onychophora)
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.
KeywordsC-value Nuclear DNA content Peripatidae Peripatopsidae Flow cytometry Feulgen image analysis densitometry Karyotype
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.
- Abràmoff MD, Magalhães PJ, Ram JS (2004) Image processing with imageJ. Biophotonics Int 11:36–42Google Scholar
- Anderson DT (1973) Embryology and phylogeny in annelids and arthropods. In: Kerkut GA (ed) Pergamon Press, OxfordGoogle Scholar
- Campbell LI, Rota-Stabelli O, Edgecombe GD, Marchioroc T, Longhorna SJ, Telford MJ, Philippe H, Rebecchi L, Peterson KJ, Pisani D (2011) MicroRNAs and phylogenomics resolve the relationships of Tardigrada and suggest that velvet worms are the sister group of Arthropoda. Proc Natl Acad Sci USA 108:15920–15924PubMedCrossRefGoogle Scholar
- Doležel J, Bartoš J, Voglmayr H, Greilhuber J (2003) Nuclear DNA content and genome size of trout and human. Cytom Part A 51:127–128Google Scholar
- Evans R (1901) On the malayan species of Onychophora. Part II.—the development of Eoperipatus weldoni. Q J Microsc Sci 45:41–88Google Scholar
- Gregory TR (2012) Animal genome size database. http://www.genomesize.com
- McDonald DE, Ruhberg H, Daniels S (2012) Two new Peripatopsis species (Onychophora: Peripatopsidae) from the Western Cape province, South Africa. Zootaxa 3380:55–68Google Scholar
- Mora M, Herrera A, León P (1996) The genome of Epiperipatus biolleyi (Peripatidae), a Costa Rican onychophoran. Rev Biol Trop 44:153–157Google Scholar
- Nielsen C (2012) Animal evolution: interrelationships of the living phyla, 3rd edn. Oxford University Press, OxfordGoogle Scholar
- R Core Team (2012) R: a language and environment for statistical computing. R foundation for statistical computing, Vienna, Austria. ISBN 3-900051-07-0 http://www.R-project.org/
- Sakamoto Y, Zacaro AA (2009) Levan Tutorial—Step by Step, ViçosaGoogle Scholar
- von Kennel J (1888) Entwicklungsgeschichte von Peripatus edwardsii Blanch. und Peripatus torquatus n.sp. II. Theil. Arb Inst Würzburg 8:1–93Google Scholar