Observations on Hoplolaimus indicus Sher, 1963 and Hoplolaimus seinhorsti Luc, 1958 (Nematoda: Hoplolaimidae) from Southern Iran

Morphological observations are made on several populations of Hoplolaimus indicus and Hoplolaimus seinhorsti, recovered from rhizosphere of mango, tamarind, sour orange and sugarcane from the southern regions of Iran. Detailed studies on the two species Hoplolaimus dubius and H. indicus being separated from each other based on some morphological characters, revealed each of them having intra-specific and overlapping variations in morphology and morphometric ranges, enough for not separating two closely related aforementioned species and as a result, H. dubius is considered as a junior synonym of H. indicus. Observations on H. seinhorsti also supported the Siddiqi’s decision on the synonymy of Hoplolaimus sheri with H. seinhorsti. The results of the phylogenetic analyses using D2-D3 expansion segments of 28S rRNA gene were in agreement with the results of previous works, i.e. the classic scheme for assigning species of the genus into two "ancestral" and/or "derived" groups was supported. In phylogenetic trees inferred, using different analysis methods, the Iranian populations of H. indicus were located in the same clade with H. seinhorsti and H. columbus, belonging to "derived" group of species of the genus characterized by having six nuclei in pharyngeal glands, less than four incisures at each lateral field and anteriorly situated position of excretory pore to hemizonid.