Molecular characterisation and phylogenetic relationship of Verutus volvingentis Esser, 1981 with other cystoid nematodes of the family Heteroderidae (Nematoda: Tylenchida), and some morphological details of its immature life stages

摘要

New phylogenies of cystoid heteroderid nematodes, a group characterised by females that do not turn into hard-walled cysts, were obtained using the D2-D3 of 28S rRNA, ITS rRNA, partial 18S rRNA and partial COI mtDNA gene sequences. The cystoid nematodes studied included a Florida population of Verutus volvingentis from the type locality, an unidentified Verutus sp. from the USA, Cryphodera sp. D from Thailand, Zelandodera sp. from New Zealand and an unknown and putatively new genus of the family Verutinae from Borneo, Malaysia. The results of these analyses indicated that the subfamily Verutinae, represented by species of the genus Verutus, is phylogenetically related to the family Heteroderidae rather than Rotylenchulidae. Verutus species sequences clustered in well supported clades separated from those of other cystoid nematodes. Our study confirmed the unique status of a cystoid nematode from Borneo attributed by D. Sturhan (2018) to an unknown genus in Heteroderidae. In the phylogenetic trees obtained using the studied gene sequences, the genus Zelandodera formed a distinct lineage within Meloidoderinae, confirming the validity of this genus that has not previously been accepted by some authors. Light microscopic studies of V. volvingentis showed the presence of transparent first-stage juvenile moulted cuticle inside the eggs indicating that second-stage juveniles hatch from the eggs. Phasmids in the second-stage juvenile tail were pore-like and connected to a fine duct.