Movement behaviour and video tracking of Milnesium tardigradum Doyère, 1840 (Eutardigrada, Apochela)

Tardigrades or ‘water-bears’ live in moist environments with a high degree of gaseous exchange. In tardigrades, locomotion is essential, e.g. for feeding, to find sexual partners and to adjust the level of hydration by moving to wetter or dryer environments. Here we report on the movement behaviour of Milnesium tardigradum in automated experiments using custom-made video tracking software. The experiments involved 754 hours of recording involving 32 individuals. No significant differences in mobility were observed under infrared versus visible light conditions, representing night and day, respectively. The mean recorded velocity was 23.3 ± 7.38 mm/h, with a maximum of 1166.4 mm/h.