Planaria exhibit positive geotaxis in a test tube

Planaria exhibit positive geotaxis in a test tube which has water of constant light and temperature. In essence, the planaria settles at the bottom of the test tube (Mandal, 2010). The findings of this study are therefore in tandem with previous findings on response of planarians to gravity. According to Khanna (2004), there is tendency of planarians, when they are unfed, to settle at the bottom of a vessel (e.g. a test tube) if the water has enough oxygen. However, fed planarians seek the surface of the vessel in search of more oxygen for intracellular digestion. Since it is not identified whether the planarians were fed or unfed, it may be possible that the positive geotaxis exhibited by the planarians in this experiment may have been due to planarians probably being unfed.