Summary of the behaviors of the leech and criteria used for their identification
| Behaviors | Description | Behavior identification |
|---|---|---|
| Stationary | Anterior and posterior sucker attached to the dish | Speed of the head Vhead(n) and Vtail(n) <1 pixel/s |
| Still | Midbody still | Speed of the midbody Vmidbody(n) <1 pixel/s |
| Peristaltic-like | Midbody oscillating in a regular way | Vmidbody(n) >1 pixel/s, oscillating with a frequency of ∼0.03 Hz |
| Head attached | Midbody oscillating in an irregular way | Vmidbody(n) >1 pixel/s with no regular oscillations |
| Swimming | Undulatory movement of the entire body | Maximal speed of the head VmaxT(n) between 10 and 30 pixels/s; dominant frequency fdT(n) of elongation (head to tail distance) between 1.3 and 1.7 Hz; and speed of the tail VtailT(n) >3 pixels/s |
| Pseudo-swimming (ventilation) | Undulatory movement of the body and posterior sucker attached to the dish | VmaxT(n) between 10 and 30 pixels/s; fdT(n) of elongation between 1.3 and 1.7 Hz; and VtailT(n) <3 pixels/s |
| Crawling | Alternating steps of elongation (posterior sucker attached) and contraction (anterior sucker attached) | VmaxT(n) between 20 and 40 pixels/s; fdT(n) of elongation between 0.16 and 0.24 Hz |
| Exploratory | Irregular oscillations of the head and anterior part of the body with the posterior sucker attached | VmaxT(n) between 10 and 50 pixels/s; fdT(n) of elongation <0.12 Hz |
| Abrupt movements | Rapid transitions between two states | Changes in position of at least 20 pixels in <5 s |