Additional files and data from 'Electrical signaling and coordinated behavior in the closest relative of animals'

The transition between simple to complex multicellularity involves large degrees of division of
labor and specialization of cell types. In animals, complex sensory motor systems are primarily
built around the fundamental cell types of muscles and neurons, though the evolutionary origin
of these cells, and their integration, remains unclear. Here, in order to investigate sensory-behavior
coupling in the closest relatives of animals, we established a line of the
choanoflagellate, Salpingoeca rosetta, which stably expresses the calcium indicator RGECO1.
Using this, we identify a novel cellular behavior associated with electrical signaling, in which
ciliary arrest is coupled with apical-basal contraction of the cell. This behavior, and the
associated calcium transients, are synchronized in the multicellular state and result in
coordinated ciliary arrest and colony wide contraction, suggesting information is spread amongst
the cells. Our work reveals fundamental insights into how choanoflagellates sense and respond to
their environment and offer a new perspective into the integration of cellular and organism wide
behavior in the closest protistan relatives of animals.