Chiang Mai Journal of Science

  The aim of this study was to describe the occurrence of Clinostomum complanatum metacercariae infecting Thai medaka (Oryzias minutillus Smith, 1945), a new intermediate host, collected from Pathum Thani province, Thailand.  A total of 533 fish collected from 5 localities included 74 infected fish, 10.7% of prevalence, 0.15 of mean abundance and 1.4 of mean intensity for the fluke.  The worms were 3.58 mm in length and 0.90 mm in width.  The oral suckers were 0.20 mm long and 0.22 mm wide.  The ventral sucker was approximately 0.44 mm long and 0.46 mm wide. The surface topography of this flukes showed structural-systematic features including teguments, papillae, folds, grooves, ridges, pits, pores of glands, spines, cytoplasmic ridges and cobblestone-like units under scanning electron microscopy.  This report is the first record of C. complanatum in fish of the genus Oryzias.  Furthermore, our results may contribute to the knowledge of clinostomatids, regarding the host diversity and systematic morphology of tegumental trematodes.