The mitochondrial genome of the water spider Argyroneta aquatica (Araneae: Cybaeidae)

We sequenced nearly the entire mitochondrial genome of Argyroneta aquatica, a wholly underwater‐living spider, thereby enhancing the available genomic information for Arachnida. The confirmed sequences contained the complete set of known genes present in other metazoan mitochondrial genomes. However, the mitochondrial gene order of A. aquatica was distinctly different from that of the most distant Chelicerata Limulus polyphemus (Xiphosura), probably because of a series of gene translocations and/or inversions. Comparison of arachnid mitochondrial gene orders for the purpose of phylogenetic inference is only minimally useful, but provides a strong signal in closely related lineages. To test the basal relationships and the evolutionary pattern of tRNA gene rearrangements among Arachnida, phylogenetic analyses using amino acid sequences of the 13 protein‐coding genes were performed. An interesting feature, the five 135‐bp tandem repeats and two 363‐bp tandem repeats, was identified in the putative control region. Although control region tandem repeats have been reported in many other arachnid and metazoan species, this is the first time it has been described in spiders.