Wolbachia and Spiroplasma endosymbionts in the Anurida maritima (Collembola) species group

A large proportion of arthropods carry maternally-inherited endosymbiotic bacteria with which they have developed close relationships. Some of these endosymbionts are selfish genetic elements and manipulate their hosts’ reproduction to their own advantage, for example via cytoplasmic incompatibility (CI) or male killing. Here we report that the sexually reproducing collembolan Anurida maritima carries two endosymbionts (Wolbachia and Spiroplasma) and provide genome sequences for both bacteria. Phylogenomic analyses indicate that the Wolbachia belong to the A supergroup and that the Spiroplasma are sister to the Citri-Chrysopicola-Mirum lineage. A. maritima is considered a species group and consists of at least two distinct genetic lineages. We show that both lineages carry both endosymbionts. No homologs of the Spiroplasma male-killing gene SpAID were observed within our datasets. Homologs of the male-killing associated wmk and the CI inducing cifA and cifB prophage genes were detected in the Wolbachia genome. Phylogenetic analyses placed the cif genes in the poorly characterised Type V clade. The cifA and cifB gene sequences of the two Anurida lineages are identical. It therefore seems unlikely that the genetic divergence within the species group stems from cifA and cifB induced CI. Laboratory controlled genetic crosses and sex ratio studies will be needed to reveal any potential effect of the two endosymbionts on A. maritima’s reproduction.