Testing the responses of normal tadpoles and tadpoles after genetic modification is very simple. Tadpoles can swim and react to touch and light dimming quite well from stages 32 to 37/38 so these are good stages for behavioural testing.
Tadpoles are placed in dechlorinated tapwater in a petri dish. We normally use a fine hair or pin mounted in a glass Pasteur pipette to touch the cement gland. Mucus from the gland becomes attached so you can "lead" the tadpole gently to middle of a petri dish then move the pin quickly to break the mucus. This ensures that the mucus is not attached and exerting tension which inhibits responses (Lambert et al., 2004).
With the tadpole lying in the dish dimming should lead to swimming ( Jamieson and Roberts, 2000). This depends on excitation of the pineal eye.
If a fine mounted hair or needle is used to stroke or poke the skin on the side of the trunk, tail or head, the tadpole should swim forwards (Boothby and Roberts, 1995). This depends on innervation of the trunk skin by spinal sensory Rohon-Beard neurons, the head skin by trigeminal sensory neurons, OR the excitation of a skin impulse by stronger stimuli (like pokes with a needle; see Roberts, 1998).
When the tadpole swims into the side of the dish it should stop (Boothby and Roberts, 1992). Here is an example: