Morphological and molecular characterisation of three known species of Criconematoidea from Iran

Abstract

Summary In this study, we provide morphological and molecular characterisation of three known species of the Criconematoidea, namely Criconema cylindraceum, Paratylenchus alleni and P. steineri, recovered from Iran. Descriptions, morphometric data, drawings and photomicrographs are provided, and comparisons are made with closely related species. Phylogenetic analysis using the D2-D3 expansion segments of the 28S rRNA gene revealed that C. cylindraceum formed a cluster with Ogma decalineatus, a species with a similar head structure, but with differences in cuticle ornamentation, tail shape and morphometric characters. Moreover, P. alleni grouped with species of Paratylenchus having four lateral lines and a short stylet (< 40 μm), exceptionally including the unresolved P. straeleni, while P. steineri formed a clade with long stylet species, including P. teres and P. wuae. The taxonomic placement of C. cylindraceum in Criconema, rather than in Criconemoides, is justified, and P. teres is molecularly differentiated from P. steineri, the two species differing in having or lacking a stylet in the fourth-stage juvenile.