Anatomical and molecular characterization of some rhigonematid parasites of millipedes in Nigeria, with new insights into their phylogeny.

Parasitic nematodes of millipedes from Nigeria are molecularly characterized for the first time. During nematode surveys on live giant African millipedes from several localities in Nigeria, 4 species of rhigonematids were identified by application of integrative taxonomical approaches (morpho-anatomy and molecular markers), including Brumptaemilius sp., Gilsonema gabonensis , Obainia pachnephorus , and Rhigonema disparovis. The results of morphometric and molecular analyses of D2-D3 28S, ITS, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences further characterized the rhigonematid species, and clearly separated them from other related species. Phylogenetic relationships based on 28S and 18S rRNA genes suggest that genera within Ransomnematoidea ( Ransomnema , Heth , Carnoya , Brumptaemilius , Cattiena , Insulanema , Gilsonema ) and Rhigonematoidea ( Rhigonema , Obainia , Xystrognathus , Trachyglossoides , Ichthyocephaloides ) clustered rather closer than could be expected in view of their morphological differences. Phylogenetic relationships based on ITS and COI are congruent with those of other ribosomal genes; however, they are not conclusive due to the scarcity of available sequences of these genes for these genera in NCBI.