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Abstract

Onychophoranext term (velvet worms) represent a small animal taxon considered to be related to Euarthropoda. We have obtained 1873 5′ cDNA sequences (expressed sequence tags, previous termESTs)next term from the velvet worm Epiperipatus sp., which were assembled into 833 contigs. BLAST similarity searches revealed that 51.9% of the contigs had matches in the protein databases with expectation values lower than 10−4. Most previous termESTsnext term had the best hit with proteins from either Chordata or Arthropoda (not, vert, similar40% respectively). The previous termESTsnext term included sequences of 27 ribosomal proteins. The orthologous sequences from 28 other species of a broad range of phyla were obtained from the databases, including other previous termESTnext term projects. A concatenated amino acid alignment comprising 5021 positions was constructed, which covers 4259 positions when problematic regions were removed. Bayesian and maximum likelihood methods place Epiperipatus within the monophyletic Ecdysozoa (previous termOnychophora,next term Arthropoda, Tardigrada and Nematoda), but its exact relation to the Euarthropoda remained unresolved. The “Articulata” concept was not supported. Tardigrada and Nematoda formed a well-supported monophylum, suggesting that Tardigrada are actually Cycloneuralia. In agreement with previous studies, we have demonstrated that random previous termsequencingnext term of cDNAs results in sequence information suitable for previous termphylogenomicnext term approaches to resolve metazoan relationships.