Annotation with Blast2GO suite [46] resulted in significant BlastX hits to sequences in the non-redundant (nr) database of NCBI for in 44.6% of F. candida transcripts, while functional annotations could be retrieved for 34.2%. These percentages were slightly higher for O. cincta, where 48.5% of transcripts showed a significant BlastX hit, and 38.4% could be annotated. The relatively low functional annotation levels for both species can be explained by the lack of full-length sequences and by the relatively large phylogenetic distance between springtails and other genomic model organisms. Fig 2 provides a general overview of the most represented biological processes and molecular functions in both collembolan transcriptomes. Notably, most of the Blast top hits were retrieved from Daphnia pulex, followed by Tribolium castaneum and Pediculus humanus for both collembolan transcriptomes (S2 Fig). Interestingly, this shows that Daphnia, a crustacean, rather than the well-investigated genomes of insects such as Drosophila and Tribolium, produced the highest number of Blast hits with collembolan transcripts. This suggests that transcriptomes of springtails have more genes in common with crustaceans than with insects, although Collembola seem to be more related to Insecta, since they share the six-legged body plan as well as a terrestrial life-style in most cases. We have to note that the high level of similarity between Daphnia and Collembola could also be caused by the comparably fast evolution rates in Tribolium and Drosophila, which have been well documented [67, 68]. Nevertheless, Collembola represent one of the first lineages splitting off after the terrestrialization, still bearing a clear genomic signature of the crustaceans.