develops_from standing slug migratory slug DDANAT:0000008 Dictyostelium_discoideum_anatomy When the conditions are not optimal for the completion of development, the standing slug bends from a vertical position to a horizontal position, producing a migratory that slug has the ability to migrate towards more favorable environmental conditions. The slug is cylindrical in shape with a rounded, tapering region at its anterior end that is raised with respect to the substratum. It usually measures between 0.8 to 1.2 mm in length with a diameter of 0.15 to 0.25 mm. Slugs sense and respond to light, temperature and acidity, and do not enter culmination until the conditions are optimal. The slug can move at a speed of 0.5 to 2 mm per hour. A trail of slime is deposited on the surface during migration. pseudoplasmodium whole organism