Expression of arthropod distal limb-patterning genes in the onychophoran Euperipatoides kanangrensis
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A current hypothesis states that the ancestral limb of arthropods is composed of only two segments. The proximal segment represents the main part of the modern leg, and the distal segment represents the tarsus and claw of the modern leg. If the distal part of the limb is an ancestral feature, one would expect conserved regulatory gene networks acting in distal limb development in all arthropods and possibly even their sister group, the onychophorans. We investigated the expression patterns of six genes known to function during insect distal limb development in the onychophoran Euperipatoides kanangrensis, i.e., clawless (cll), aristaless (al), spineless (ss), zinc finger homeodomain 2 (zfh2), rotund (rn), and Lim1. We find that all investigated genes are expressed in at least some of the onychophoran limbs. The expression patterns of most of these genes, however, display crucial differences to the known insect patterns. The results of this study question the hypothesis of conserved distal limb evolution in arthropods and highlight the need for further studies on arthropod limb development.
KeywordsArthropod limb development Evolution Limb patterning
The experiments were conducted during the “Evolution and Development” course at Uppsala University in the spring of 2013. We gratefully acknowledge the support of the New South Wales government Department of Environment and Climate Change by provision of a permit SL100159 to collect onychophorans at the Kanangra Boyd National Park and the Australian government Department of the Environment, Water, Heritage, and the Arts for export permits WT2009-4598 and WT2012-4704. The authors wish to thank Jean Joss, Rolf Ericsson, Robyn Stutchbury, and especially Noel Tait, for their help during onychophoran collection. Mattias Hogvall is thanked for his help as laboratory assistant. Nico Posnien and Alistair McGregor helped with the analysis of the embryonic transcriptome.
- Campbell LI, Rota-Stabelli O, Edgecombe GD, Marchioro T, Longhorn 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 108:15920–15924PubMedCentralPubMedCrossRefGoogle Scholar
- Dunn CW, Hejnol A, Matus DQ, Pang K, Browne WE, Smith SA, Seaver E, Rouse GW, Obst M, Edgecombe GD, Sorensen MV, Haddock SHD, Schmidt-Rhaesa A, Okusu A, Kristensen RM, Wheeler WC, Martindale MQ, Giribet G (2008) Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452:745–749PubMedCrossRefGoogle Scholar
- Kittelmann M, Schinko JB, Winkler M, Bucher G, Wimmer EA, Prpic NM (2009) Insertional mutagenesis screening identifies the zinc finger homeodomain 2 (zfh2) gene as a novel factor required for embryonic leg development in Tribolium castaneum. Dev Genes Evol 219:399–407PubMedCentralPubMedCrossRefGoogle Scholar