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

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 μ m), 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. [ABSTRACT FROM AUTHOR]