Cockroaches that lack Blattabacterium endosymbionts: the phylogenetically divergent genus Nocticola.

Phylogenetic relationships among termites, mantids and the five traditionally recognized cockroach families have been the subject of several studies during the last half-century. One cockroach lineage that has remained notably absent from such studies is the Nocticolidae. This group of small, elusive surface- and cave-dwelling species from the Old World Tropics has been proposed to represent an additional family. Using molecular sequences, we performed an initial phylogenetic examination of Nocticola spp. The hypothesis that they are phylogenetically divergent was confirmed from the analyses of three genes and a combined dataset. To supplement our phylogenetic analyses, we attempted to amplify 16S rRNA from the obligate mutualistic endosymbiont Blattabacterium cuenoti, present in all cockroaches studied to date. Unexpectedly, amplification was unsuccessful in all Nocticola spp. examined. This result was confirmed by microscopic examinations of fat body tissue. These Nocticola spp. are the first cockroaches found to be uninfected by B. cuenoti, which raise questions about when the bacterium first infected cockroaches.