Light-Sensitive Channels
(A) Normal movements of C. elegans. (B) When light-sensitive channelrhodopsin-2 ion channels are introduced into its neurons, C. elegans becomes active and coils when exposed to blue light. Information from Zhang et al., 2007. (C) With light-sensitive halorhodopsin ion pumps introduced into its muscles, C. elegans elongates and becomes immobile when exposed to green-yellow light. Information from Liewald et al., 2008.

Sinclair Stammers/Science Source