Research Article: Two Ektaphelenchinae Paramonov, 1964 (Nematoda: Rhabditida) from Iran have tripartite stylet, with similar observations in other species

Date Published: May 13, 2019

Publisher: Public Library of Science

Author(s): Majid Pedram, Sandhya Koushika.


Two ektaphelenchid nematodes representing one new and one known species are illustrated and characterized using morphological and molecular data. Ektaphelenchus kanzakii n. sp. is mainly characterized by its tripartite stylet having a well visible wide lumen, encompassing a sclerotized and acute anterior part (the conus), a short and slightly tapering middle part (the conophore) that is equally sclerotized but clearly separate from the conus, and a long posterior part that is cylindrical and only weakly sclerotized (the shaft) without basal knobs or swellings. It is further characterized by 863.5 (772–926) μm long females having 23.8 (21.2–27.0) μm long total stylet, distinctly annulated cuticle, three lines in lateral field, vulva at 76.6 (75.3–80.0)%, no rectum, vestigial anus in some individuals, conical posterior body end (tail) with narrow ventrally bent tip, common males in population with two pairs of caudal papillae (the single precloacal papilla and the third caudal pair lacking), spicules with dorsally bent tip and conical tail with sharp or blunt tip. The new species is morphologically compared with close species having conical posterior body end and stylet lacking basal knobs or swellings. Iranian population of Devibursaphelenchus teratospicularis, the second studied species, is characterized by 679.5 (620–709) μm long females having 18.6 (17.5–20.0) μm long total stylet with similar structure to the previous species, subcylindrical body end with widely rounded tip, and rare males with typical spicules of this species and a pair of precloacal and a pair of caudal papillae. Molecular phylogenetic studies of the two recovered species using small and large subunit ribosomal DNA (SSU and LSU rDNA) partial sequences revealed they have close phylogenetic affinities with Ektaphelenchus obtusus in both reconstructed trees. However, species of both genera Ektaphelenchus and Devibursaphelenchus don’t form monophyletic groups in SSU and LSU trees. New observations on stylet structure of the two presently studied and some other ektaphelenchid species having available light microphotographs (LM) yielded on definition of a new term “conophore” for the middle part of the ektaphelenchid-type tripartite stylet.

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Currently 28 species are placed under the genus Ektaphelenchus Fuchs, 1937 [1] (24 in Hunt [2], plus four recently described species: E. taiwanensis Gu, Wang & Chen, 2013 [3], E. ibericus Gu, Wang, Chen & Wang, 2013 [4], E. berbericus Alvani, Mahdikhani-Moghadam, Giblin-Davis & Pedram, 2016 [5] and E. oleae Miraeiz, Heydari, Adeldoost & Ye, 2017 [6], thereafter). The genus is known in Iran with two representatives (E. oleae and E. berbericus, both of which are described form Iran, and apparently are endemic to the country after currently available reports).

The continued studies on identification of ektaphelenchid nematodes occurring in Iran, yielded two species illustrated and studied in present paper. The new species Ektaphelenchus kanzakii n. sp. was described based upon morphological and molecular data. It has a three partite stylet, as described, and an epiptygma-like projection in the vulva. A new term was proposed for the middle part of the stylet, the conophore, differentiating the ektaphelenchid-type tripartite stylet from the common tripartite stylet seen in most non-ektaphelenchid tylenchs (which have conus + shaft + knobs).