FIRST RECORD OF FREE LIVING SOIL NEMATODES, MESORHABDITIS MINUTA (BOSTROM, 1991) IN IRAQ Layla A. Hassan 1 and Muhanned R. Nashaat 2 1 Directorate of Karkh, Ministry of Education, Iraq. 2 Animal and Fish Resources Center, Agricultural and Biological Research Directorate, Ministry of Science and Technology, Iraq. (Accepted 30 May 2018) ABSTRACT : The current study included the new record of the free living nematode, Mesorhabditis minuta in the fields of agricultural crops of cucumber, during the period between May to November, 2016. It is characterized by a tiny body (L= 560.4±39.19 μm) in female and (374.6±22.43 μm) in male. Females have a conical tail with sharp tip, vulva-anus distance slightly larger than tail, the absence of pharyngeal collar and post-uterine sac. Male with short spicules 24±0.63 μm fused at the end part, Peloderan bursa proximally open with papillae arranged 2+4+3. Key words : Mesorhabditis minuta, soil nematodes, free living, new record, Iraq. Biochem. Cell. Arch. Vol. 18, Supplement 1, pp. 1289-1292, 2018 www.connectjournals.com/bca ISSN 0972-5075 INTRODUCTION Soil nematodes are microscopic animals, which are very abundant and diverse in all soils (Yeates, 1979), feed on a large range of organisms in the soil and are dependent on the existence of soil water films, which has an important role in it’s movement (Yeates and Bongers, 1999). In Iraq soil nematodes as parasites on plant have been frequently reported as in study of Katcho et al (1976), Stephan et al (1985) and Taher et al (2017), while free living Nematodes in soil didn’t receive the same attention, despite its importance as bioindicators for the health of soil because it formation well correlates with nitrogen cycling and disintegration (Neher, 2001) so the study included the new record of the free living nematode Mesorhabditis minuta, which belongs to Rhabditiae family. Osche (1952) confirm the role of the fine parts of the stoma in the taxonomy of rhabditids so he split Rhabditis into many subgenera, Mesorhabditis was one of them, Dougherty (1953) add more subgenera to Rhabditis and at the same time uplift the subgenera Mesorhabditis to be full generic rank. While, Sudhaus and Fitch (2001) consider again sub genera to Rhabditis. Mesorhabditis bacterial feeding (Yeates et al, 1993) Andrassy (1983) listed the members of this genus as seventeen valid species and three as species in quirendae. In later years more species adding to the genus by Bostrom (1991), Nicholas (1998), Shah (2005), Abolafia and Pena-Santiago (2009), Ahmad et al (2010) and Borgonie et al (2010). MATERIALS AND METHODS Samples of soil were taken by cylindrical metal core 15cm at depth and 5cm internal diameter from the fields of agricultural crops of cucumber, which belong to the College of Agriculture, University of Baghdad during May to November 2016 with 4 replications monthly. Nematodes were isolated by Baermann’s funnel (Bezooijen, 2006) then the eighteen females and five males were photographed after reducing their movement by heat (Al Zainab and Khtyb, 2003) using an inverted microscope (Leica). Measurement done by Miotic Image plus 2.0 program after calibration of the pictures with microscope lens and the results are given as means ± standard deviation (range) and use the some taxonomic key such as Andrassy (1983), Bostrom (1991), Nicholas (1998), Shah (2005), Abolafia and Pena-Santiago (2009), Ahmad et al (2010) and Borgonie et al (2010) for Nematode identification. RESULTS General description:plate1 (A-C) Adult of worms have somewhat fusi form shape, cuticle finely and slight annulated, female longer and wider than male (Table 1). Head with 6 clearly separate lips each ending a setose papilla. Stoma tubular, cylindrical and narrow, length equals 4.7±0.56 times from it is width in females and 5.98±155 times in males, it also equivalent 1.5 times from head width and nerarly 7 1 from esophagus length in both sexes. Metasomisoglottoid pharyngeal collar